JP7614728B2 - Adhesive sheet with release film - Google Patents

Description

The present invention relates to an adhesive sheet with a release film.

Generally, adhesives (also called pressure-sensitive adhesives; the same applies below) are in a soft solid (viscoelastic) state at temperatures around room temperature, and have the property of easily adhering to an adherend when pressure is applied. Taking advantage of this property, adhesives are typically in the form of adhesive sheets containing a layer of the adhesive, and are widely used in a variety of industrial fields, from home appliances to automobiles and office equipment.

Some of the above adhesive sheets require a high degree of smoothness on the adhesive surface (surface of the adhesive layer). One example of such an adhesive sheet is an adhesive sheet for optical applications. For example, Patent Documents 1 and 2 describe that the surface roughness (Ra) of the adhesive layer of an optical adhesive sheet is set to a predetermined range in order to improve visibility. Patent Document 3 describes that the ten-point average roughness of the adhesive surface of an adhesive sheet that can be used for optical applications is set to about 1000 nm or less. Patent Document 4 describes that in an adhesive sheet that is attached to an optical member such as a polarizing plate, the surface roughness (Ra) of a release film placed on the surface of the adhesive layer is set to 0.1 μm or less. Patent Document 5 describes that the surface roughness (Ra) and maximum projection height (Rp) of the release film are set to a predetermined range.

Patent No. 4673344 Patent No. 4805999 JP 2017-105974 A Patent No. 4069625 Patent No. 6300788

In various products such as portable electronic devices, adhesive sheets can be used in areas that are visible from the outside. For example, adhesive sheets for portable electronic devices can be used not only on the image display surface of the electronic device, but also on other surfaces (e.g., the back surface). Therefore, adhesive sheets used for this purpose may be required to have high transparency that makes their presence unnoticeable, and the adhesive surface may also be required to be highly smooth. If orange peel or streaks are present on the adhesive surface, visibility through the adhesive sheet will be reduced, and the design, beauty, and luxurious feel of the adherend surface may be impaired.

One application in which a highly smooth adhesive surface is desirable, but is not limited to this, is the application of attaching a film with a design including a specific color tone such as a metallic tone to the inside of a transparent housing constituting a portable electronic device, with the design forming surface (decorative surface) facing the transparent housing. Since both adhesive surfaces of the adhesive sheet used to fix the transparent housing and the film can affect visibility, it is desirable that both adhesive surfaces have high smoothness. Even adhesive sheets with smoothness that have been considered to be at an acceptable level in the past do not necessarily have a satisfactory level of surface smoothness, as optical distortion is observed under more accurate evaluation conditions. If an adhesive sheet with an adhesive surface with a higher degree of smoothness could be realized, it would be practically useful as a joining means that does not impair the design, aesthetics, or luxury of the adherend.

The present invention was created in consideration of the above circumstances, and aims to provide an adhesive sheet with an adhesive surface having high surface smoothness, protected by a release film.

According to this specification, a pressure-sensitive adhesive sheet with a release film is provided. This pressure-sensitive adhesive sheet with a release film includes a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a release film laminated on the adhesive surface of the pressure-sensitive adhesive sheet. The maximum height Rz of the adhesive surface of the release film is 400 nm or less.
According to the above configuration, the adhesive surface of the adhesive sheet is protected by the release film while in contact with the surface of the release film having a maximum height Rz of 400 nm or less, and therefore has high surface smoothness. Therefore, when the adhesive sheet is attached to the adherend, the adhesive surface with the adherend has high surface smoothness, and adhesion with no optical distortion or suppressed optical distortion can be achieved.

In some preferred embodiments, the arithmetic mean roughness Ra of the surface of the release film is 30 nm or less. This configuration preferably realizes a configuration with an adhesive surface having high surface smoothness.

In some preferred embodiments, the peeling force of the release film against the adhesive sheet is 1 N/50 mm or less. This configuration suppresses fine waviness of the adhesive surface due to the so-called stick-slip phenomenon caused by peeling from the release film when the release film is removed from the adhesive surface during use of the adhesive sheet, making it easier to obtain a smoother adhesive surface.

In some preferred embodiments, the thickness of the release film is within the range of 50 to 125 μm. By configuring in this manner, the release film has a sufficient thickness, and it is possible to prevent an event (dent) in which the smoothness of the adhesive sheet surface is impaired through the release film. Such an event may be caused, for example, by foreign matter that gets mixed in between the release films when the adhesive sheet with the release film is wound into a roll. In addition, by making the thickness of the release film equal to or less than a predetermined value, it becomes easier to remove the release film from the adhesive sheet, and the adhesive surface of the adhesive sheet is more likely to maintain a high surface smoothness even after the release film is removed.

In some preferred embodiments, the adhesive sheet has a total light transmittance of 85% or more and a haze value of 1% or less. An adhesive sheet that satisfies the above characteristics allows the adherend to be easily seen through the adhesive sheet, and does not impair the visibility of the design, etc., of the adherend.

In some embodiments, the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer and a supporting substrate laminated on one side of the pressure-sensitive adhesive layer. The effects of the technology disclosed herein can be preferably achieved in an embodiment using a single-sided pressure-sensitive adhesive sheet. In this embodiment, the supporting substrate can be a transparent substrate.

In some other embodiments, the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a first adhesive surface and a second adhesive surface. The pressure-sensitive adhesive sheet with a release film has a first release film arranged on the first adhesive surface and a second release film arranged on the second adhesive surface as release films. The maximum height Rz ₁ of the first adhesive surface side surface S1 of the first release film and the maximum height Rz 2 of the second adhesive surface side surface S2 of the second release film are both 400 nm or less. Even in such a configuration, the effects of the technology disclosed herein can be preferably realized. In this configuration, it _is preferable that the arithmetic mean roughness Ra ₁ of the surface S1 of the first release film and the arithmetic mean roughness Ra ₂ of the surface S2 of the second release film are both 30 nm or less. The peeling force of the first release film to the pressure-sensitive adhesive sheet and the peeling force of the second release film to the pressure-sensitive adhesive sheet can both be 1 N/50 mm or less. Furthermore, the thickness of the first release film and the thickness of the second release film may each be within the range of 50 to 125 μm.

In still other embodiments, the pressure-sensitive adhesive sheet is a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface. The release film is a double-sided release film having a first release surface and a second release surface. The maximum height Rz ₁ of the first release surface of the release film and the maximum height Rz ₂ of the second release surface of the release film are both 400 nm or less. Even in such a configuration, the effects of the technology disclosed herein can be preferably realized. In this configuration, it is preferable that the arithmetic mean roughness Ra ₁ of the first release surface and the arithmetic mean roughness Ra ₂ of the second release surface are both 30 nm or less. The peeling force of the first release surface relative to the pressure-sensitive adhesive sheet and the peeling force of the second release surface relative to the pressure-sensitive adhesive sheet may both be 1 N/50 mm or less.

In some preferred embodiments, the adhesive layer is an acrylic adhesive layer. With an acrylic adhesive, it is possible to achieve the desired adhesive properties and viscoelastic properties with excellent impact resistance without using additives such as softeners that can cause a decrease in transparency, or by limiting the amount of additives used, making it easy to achieve both transparency and adhesive and viscoelastic properties. In addition, acrylic adhesives tend to have better resistance to discoloration than, for example, rubber-based adhesives, and are also advantageous in terms of maintaining transparency over a long period of time.

In some preferred embodiments, the gel fraction of the adhesive layer is 30 to 95% by weight. When the gel fraction of the adhesive layer is 95% by weight or less, the adhesive sheet tends to have excellent conformability to uneven surfaces. Therefore, it can adhere well to the surface of an adherend having uneven surfaces. For example, when a logo mark or the like is printed on the surface of the adherend, the adhesive sheet can conform well to the unevenness of the print without impairing visibility. In addition, when the gel fraction of the adhesive layer is 30% by weight or more, it tends to easily exhibit good adhesive properties and viscoelastic properties. For example, a configuration having an adhesive layer with the above gel fraction tends to be less likely to cause dents and also has excellent deformation resistance.

In some preferred embodiments, the pressure-sensitive adhesive layer has a storage modulus at 25° C. of 4 × 10 ⁴ Pa or more. A pressure-sensitive adhesive layer having the above-mentioned storage modulus at 25° C. tends to have favorable heat resistance and is likely to exhibit favorable adhesive properties such as deformation resistance.

In some preferred embodiments, the thickness of the adhesive sheet is 5 to 100 μm. Adhesive sheets with a thickness of 5 μm or more tend to have excellent conformability to uneven surfaces and are easy to absorb deformation caused by foreign matter, etc. Furthermore, by setting the thickness to 100 μm or less, the adhesive sheet is less likely to warp and a high adhesive surface smoothness is easily obtained.

In some preferred embodiments, the pressure-sensitive adhesive sheet has a modulus of elasticity of 3.0 MPa or more as measured by the tensile test described below. By satisfying the above characteristics, the pressure-sensitive adhesive sheet can exhibit high resistance to deformation.
[Tensile test]
The adhesive layer of the adhesive sheet is irradiated with ultraviolet light at an illuminance of 300 mW/ ^cm2 and an accumulated light quantity of 3000 mJ/ ^cm2 , and then aged at 50°C for 48 hours, after which the adhesive layer is cut to a size of 10 mm in width and 150 mm in length to prepare a test piece. A tensile test is performed on the test piece using a tensile tester under conditions of 23°C and 50% RH, with a chuck distance of 120 mm and a tensile speed of 50 mm/min to obtain a stress-displacement curve, and the elastic modulus [MPa] is calculated from the initial slope.

In some preferred embodiments, the pressure-sensitive adhesive sheet has an impact resistance of 2.0 J/10 ^mm2 or more as measured by the following shear impact test. By satisfying the above characteristics, the pressure-sensitive adhesive sheet can exhibit high impact resistance. For example, a pressure-sensitive adhesive sheet that satisfies the elastic modulus characteristics and the impact resistance characteristics in the tensile test described above can form a bond that is highly resistant to deformation and highly resistant to impact, and can therefore be preferably used, for example, for the purpose of joining or fixing members.
[Shear impact test]
A shear impact test is performed using a pendulum-type adhesive shear impact tester based on JIS K6855. As a measurement sample, a first surface of the 10 mm square pressure-sensitive adhesive sheet is attached to the center of a 25 mm square, 1.7 mm thick chemically strengthened glass plate, and then a second surface of the pressure-sensitive adhesive sheet is attached to the center of a 40 mm square stainless steel plate (SUS304BA plate) and pressed with a load of 5 N for 10 seconds, followed by autoclaving (50°C, 0.5 MPa, 15 minutes), irradiating with ultraviolet light from the glass plate side under conditions of an illuminance of 300 mW/ ^cm2 and an integrated light quantity of 3000 mJ/ ^cm2 , and then aging at 50°C for 48 hours.
The measurement sample was fixed with the stainless steel plate facing down, and the impact resistance [J/10 mm2] was determined by measuring the absorbed energy [J] when a hammer was struck against the outer peripheral side of the glass plate under conditions of a hammer energy of 2.75 J and a hammer speed of 3.5 m/sec in an environment of 23°C and ^50% RH.

In some preferred embodiments, the pressure-sensitive adhesive layer contains a polymer (A) and a photoreactive monomer (B). The photoreactive monomer (B) further contains a compound B1 having a ring structure and two or more ethylenically unsaturated groups in the molecule, and it is more preferable that the molecular weight of the compound B1 per ethylenically unsaturated group is 100 g/mol or more. A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer can suitably form a bond that is highly resistant to deformation and highly resistant to impact.

The adhesive sheet with release film disclosed herein can realize an adhesive sheet with high surface smoothness on both adhesive surfaces, and is therefore preferably used in applications for fixing a transparent member to a member having an image display surface, decorative surface, or colored surface, which tend to require high visibility. For example, in an embodiment in which the decorative surface of a decorative film is fixed to a transparent member, the adhesive sheet has suppressed optical distortion, making the decorative surface easily visible through the adhesive sheet, and can function as a joining means that does not impair the design, beauty, or luxury of the decorative surface.

The adhesive sheet with release film disclosed herein can be provided in the form of an adhesive sheet with release film roll in which the adhesive sheet with release film is wound. Such a roll body is easy to handle during storage and transportation, and is also advantageous in terms of productivity.

FIG. 1 is a schematic cross-sectional view showing a pressure-sensitive adhesive sheet with a release film according to one embodiment. FIG. 4 is a schematic cross-sectional view showing a pressure-sensitive adhesive sheet with a release film according to another embodiment.

The following describes preferred embodiments of the present invention. Note that matters necessary for the implementation of the present invention other than those specifically mentioned in this specification can be understood by a person skilled in the art based on the teachings on the implementation of the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the field. In addition, in the following drawings, components and parts that perform the same function may be described with the same reference numerals, and duplicated descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the product actually provided.

In this specification, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure, as described above. The adhesive referred to here may generally be a material that has a property of satisfying a complex tensile modulus E ^* (1Hz)< ¹⁰⁷ dyne/ ^cm2 (typically, a material that has the above property at 25°C), as defined in "CA Dahlquist, "Adhesion: Fundamental and Practice", McLaren & Sons, (1966) P. 143".

In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer, and is also called an acrylic polymer. The acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group in one molecule. In addition, in this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.
In this specification, the terms "mass" and "weight" are synonymous.

In this specification, a "photoreactive monomer" is a compound having at least one functional group (photoreactive functional group) in the molecule that can undergo a reaction when irradiated with light, and typically a compound having at least one ethylenically unsaturated group in the molecule as the photoreactive functional group. The photoreactive monomer referred to here may be any monomer that can undergo a reaction as a monomer, and may itself be, for example, a polymer such as an oligomer or polymer (for example, a polymer having at least one ethylenically unsaturated group in the molecule).

In addition, in this specification, "photocurable" refers to the property of being cured by irradiation with light such as ultraviolet light. For example, a photocurable adhesive composition refers to a composition that is cured by photocuring to become an adhesive or an adhesive layer. A photocurable adhesive layer refers to an adhesive layer that can be cured by irradiation with light such as ultraviolet light, and is used as a term referring to an adhesive layer before photocuring treatment that is completely cured by carrying out a photocuring treatment. A photocurable adhesive sheet is used as a term referring to an adhesive sheet that includes such a photocurable adhesive layer.

<Examples of the configuration of adhesive sheets with release film>
One configuration example of the adhesive sheet with a release film disclosed herein is shown in FIG. 1. This adhesive sheet with a release film 1 includes a double-sided adhesive sheet 10, a first release film 21, and a second release film 22. The adhesive sheet 10 has a first adhesive surface 10a and a second adhesive surface 10b on the opposite side of the first adhesive surface 10a. The adhesive sheet 10 of this embodiment is a substrateless double-sided adhesive sheet made of an adhesive layer 12, and therefore the first adhesive surface 10a and the second adhesive surface 10b are the first surface 12a and the second surface 12b of the adhesive layer 12, respectively. The first release film 21 is disposed on the first adhesive surface 10a of the adhesive sheet 10, and one surface (first adhesive surface side surface S1) 21a is in releasable contact with the first adhesive surface 10a of the adhesive sheet 10. The second release film 22 is disposed on the second adhesive surface 10b of the adhesive sheet 10, and one surface (second adhesive surface side surface S2) 22a of the second release film 22 is in contact with the first adhesive surface 10b of the adhesive sheet 10 in a releasable manner. The first adhesive surface side surface (S1) 21a of the first release film 21 and the second adhesive surface side surface (S2) 22a of the second release film 22 are release surfaces having a release treatment layer made of, for example, a silicone-based release treatment agent. In this way, the adhesive sheet 1 with release film is in a form in which the first adhesive surface 10a and the second adhesive surface 10b of the adhesive sheet 10 are protected by the first release film 21 and the second release film 22, respectively. Then, when the adhesive sheet 10 is used, the first release film 21 and the second release film 22 are removed, and the first adhesive surface 10a and the second adhesive surface 10b are exposed and are attached to an adherend.

The adhesive sheet 1 with a release film may be in the form of a roll (adhesive sheet roll with a release film) 100 as shown in FIG. 1. Such an adhesive sheet roll 100 has the adhesive sheet 1 with a release film wound around a core (rolling core) 50.

The structure of an adhesive sheet with a release film according to another embodiment is shown in FIG. 2. The adhesive sheet with a release film 2 shown in FIG. 2 comprises a one-sided adhesive sheet (single-sided adhesive sheet) 10 and a release film 21. The single-sided adhesive sheet 10 comprises an adhesive layer 12 and a support substrate 14 supporting the adhesive layer 12, one side of which (the first side 12a of the adhesive layer 12) is an adhesive surface 10a, and the other side is a back surface (non-adhesive surface). In this embodiment, the back surface of the adhesive sheet 10 is constituted by one side 14b of the support substrate 14 (the surface opposite to the adhesive layer side surface 14a of the support substrate 14). The second side 12b of the adhesive layer 12 is fixed to the other side (adhesive layer side surface) 14a of the support substrate 14, and the adhesive layer side surface) 14a can be said to be a non-peeling surface (non-peeling surface). In this way, the adhesive layer 12 is provided without the intention of separating it from the support substrate 14. On the other hand, the surface (adhesive surface S1) 21a of the release film 21 is a release surface, similar to the first release film in FIG. 1, and is in releasable contact with the adhesive surface 10a of the adhesive layer 12 to protect the adhesive surface 10a. This adhesive sheet 2 with release film can also be provided in the form of a roll (adhesive sheet roll) 200 as shown in FIG. 2. The adhesive sheet roll 200 has the adhesive sheet 10 with the adhesive layer 12 and the support substrate 14, and the adhesive sheet 2 with release film having the release film 21, wound around a core (rolling core) 50.

Note that, although FIG. 1 illustrates a roll body 100 in which the adhesive sheet 1 with a release film is wound around a core 50, the roll body 100 may be in a form that does not have a core 50, i.e., a so-called coreless type roll body in which the adhesive sheet 1 with a release film is wound alone. The same applies to the roll body 200 shown in FIG. 2.

In addition, the adhesive sheet 1 (before use) shown in FIG. 1 has a configuration in which the first adhesive surface 10a and the second adhesive surface 10b are protected by a first release film 21 and a second release film 22, at least the adhesive side of which is a surface (release surface) having releasability, respectively. However, the second release film 22 may be omitted, and a release film 21 having release surfaces on both sides may be used, and the adhesive sheet 1 may be rolled up to bring the second adhesive surface 10b into contact with the back surface of the release film 21, so that the second adhesive surface 10b is also protected by the release film 21.

The adhesive sheet may be a substrate-less adhesive sheet as shown in FIG. 1, a substrate-attached single-sided adhesive sheet as shown in FIG. 2, or a substrate-attached double-sided adhesive sheet. Specifically, the adhesive sheet may be a substrate-embedded adhesive sheet with a non-peeling substrate. The substrate may be a plastic film, paper, nonwoven fabric, or the like. Although FIGS. 1 and 2 show an example of a form in which the adhesive layer 10 has a single layer structure, the configuration of the adhesive layer 10 is not limited thereto. For example, the adhesive layer may be configured to include two or more sub-adhesive layers made of the same or different adhesives.

<Release film>
(Maximum height Rz of adhesive surface)
The release film disclosed herein has a maximum height Rz of the adhesive side surface of 400 nm or less. This allows the adhesive surface of the adhesive sheet to have high surface smoothness. In addition, in a form in which the first and second release films are disposed on each adhesive surface of the adhesive sheet, the maximum height Rz ₁ of the first adhesive side surface S1 of the first release film and the maximum height Rz ₂ of the second adhesive side surface S2 of the second release film are both 400 nm or less. This allows each adhesive surface of the double-sided adhesive sheet to have high surface smoothness, and both adhesive surfaces can exhibit high surface smoothness when attached to an adherend.

The maximum height Rz of the adhesive surface of the release film (including the maximum height _Rz1 of the first adhesive surface S1 of the first release film and the maximum height _Rz2 of the second adhesive surface S2 of the second release film. The same applies hereinafter unless otherwise specified) is preferably about 340 nm or less, more preferably about 280 nm or less, and even more preferably about 240 nm or less, and may be less than 200 nm, less than 150 nm, or less than 120 nm. In addition, from the viewpoint of ease of production and handling of the release film, in some embodiments, the above maximum height Rz may be, for example, about 50 nm or more, about 80 nm or more, or about 100 nm or more. In an embodiment having a first and second release film, the maximum height _Rz1 of the first adhesive surface S1 of the first release film and the maximum height _Rz2 of the second adhesive surface S2 of the second release film may be about the same or different.

(Arithmetic mean roughness Ra of adhesive side surface)
In addition, it is preferable that the arithmetic mean roughness Ra of the adhesive side surface of the release film is limited to a predetermined value or less (e.g., about 100 nm or less, or even less than 50 nm) from the viewpoint of realizing an adhesive surface with high surface smoothness. In addition, in a form in which a first and a second release film are disposed on each adhesive surface of the adhesive sheet, it is appropriate that the arithmetic mean roughness Ra ₁ of the first release film surface S1 and the arithmetic mean roughness Ra ₂ of the second adhesive side surface S2 of the second release film are limited to, for example, about 100 nm or less (or even less than 50 nm). In some embodiments, the arithmetic mean roughness Ra of the adhesive surface of the release film (including the arithmetic mean roughness Ra ₁ of the first adhesive surface S1 of the first release film and the arithmetic mean roughness Ra ₂ of the second adhesive surface S2 of the second release film. The same applies hereinafter unless otherwise specified) is preferably about 30 nm or less, and may be about 25 nm or less, about 20 nm or less, or about 18 nm or less. In addition, from the viewpoint of ease of production and handling of the release film, in some embodiments, the arithmetic mean roughness Ra may be, for example, about 5 nm or more, about 10 nm or more, or about 15 nm or more. In an embodiment having a first and a second release film, the arithmetic mean roughness Ra ₁ of the first adhesive surface S1 of the first release film and the arithmetic mean roughness Ra ₂ of the second adhesive surface S2 of the second release film may be about the same or different.

(Surface properties of the back side)
The maximum height Rz and arithmetic mean roughness Ra of the back surface (opposite side to the adhesive layer) of the release film (including the first release film and the second release film) are not particularly limited. The maximum height Rz of the back surface (opposite side to the adhesive layer) of the release film may be more than 400 nm (e.g., about 500 nm or more) or more than 800 nm (e.g., 1000 nm or more) from the viewpoint of productivity, etc. The arithmetic mean roughness Ra of the back surface (opposite side to the adhesive layer) of the release film may be more than 30 nm (e.g., more than 35 nm, or even about 50 nm or more) from the viewpoint of productivity, etc.

The maximum height Rz and arithmetic mean roughness Ra of the release film surface can be adjusted by the selection of the film material, the molding method, surface treatment such as release treatment, etc. Examples include adjusting the smoothness of the layers that make up the release surface (anti-blocking layer, hard coat layer, oligomer prevention layer, etc.), reducing or eliminating the use of filler particles in the surface layer or release film substrate (particle-free), and adjusting the stretching conditions.

The maximum height Rz and arithmetic mean roughness Ra of the release film surface are measured using a non-contact surface roughness measuring device. As a non-contact surface roughness measuring device, a light interference type surface roughness measuring device is used, for example, a three-dimensional optical profiler (product name "NewView7300", manufactured by ZYGO) or an equivalent product can be used. For example, a glass plate (a soda lime glass plate manufactured by MATSUNAMI, thickness 1.3 μm) is attached and fixed with an adhesive to the surface opposite to the measurement surface of the release film, and the surface shape can be measured using a three-dimensional optical profiler (product name "NewView7300", manufactured by ZYGO) in an environment of 23°C and 50% RH. The same applies to the examples described later. The specific measurement conditions and calculation method are the same as the measurement conditions for the maximum height Rz and arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet described in the examples described later.

The release film (including the first release film and the second release film; the same applies below unless otherwise specified) may be selected and used from those having a maximum height Rz of the adhesive side surface of 400 nm or less. Non-limiting examples of release films that may be used include release films having a release treatment layer on the surface of the release film substrate; and release films made of low-adhesion resins such as fluorine-based polymers (polytetrafluoroethylene, etc.) and polyolefin-based resins (polyethylene, polypropylene, etc.).

As the release film disclosed herein, one having a release treatment layer on a release film substrate can be preferably used. The release treatment layer can be formed by surface treating the release film substrate with a release treatment agent. The release treatment agent can be a known release treatment agent such as a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine-based release treatment agent, or molybdenum (IV) sulfide. In some embodiments, a release film having a release treatment layer made of a silicone-based release treatment agent can be preferably used. The thickness and method of forming the release treatment layer are not particularly limited, and can be set so that appropriate release properties are exhibited on the adhesive side surface of the release film.

Various plastic films can be used as the release film substrate. In this specification, a plastic film is typically a non-porous sheet, and is a concept that is distinguished from, for example, nonwoven fabric (i.e., does not include nonwoven fabric).

Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as triacetyl cellulose; acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, and cyclic polyolefin resins such as norbornene resins; (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyarylate resins, and polyphenylene sulfide resins. Release film substrates formed from one or a mixture of two or more of these resins can be used. Among these, a polyester resin film (e.g., a PET film) formed from a polyester resin is a preferred release film substrate.

The plastic film used as the release film substrate described above may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. The plastic film may have a single layer structure or a multilayer structure including two or more sublayers. The plastic film may contain known additives that can be used in release film substrates for pressure-sensitive adhesive sheets, such as antioxidants, antiaging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, and nucleating agents. In a multilayer plastic film, each additive may be contained in all sublayers, or only in some of the sublayers.

In some preferred embodiments, the release film substrate (typically a plastic film) may be one in which the content of particles such as inorganic particles (e.g., pigments, lubricants, fillers, etc.) in the layer on the release surface side is limited, or one that is substantially free of such particles. Here, "substantially free" means that the amount of particles (e.g., inorganic particles) in the layer is less than 1% by weight, preferably less than 0.1% by weight (e.g., 0 to 0.01% by weight). A release film having such a release film substrate tends to have a low maximum height Rz and arithmetic mean roughness Ra of the release surface. When the release film substrate (typically a plastic film) has a multilayer structure, the particle content in the layer on the release surface side may be 1/10 or less (e.g., 1/50 or less) of the particle content in layers other than the layer on the release surface side.

In embodiments having a first and second release film, the first release film and the second release film may be made of the same material and have the same configuration, or may be made of different materials and have different configurations.

The thickness of the release film is not particularly limited, and may be, for example, about 10 μm to 500 μm. From the viewpoint of the strength and dimensional stability of the release film, the thickness of the release film is suitably 20 μm or more, preferably 30 μm or more, may be 35 μm or more, may be 40 μm or more, or may be 45 μm or more. In some preferred embodiments, the thickness of the release film is approximately 50 μm or more, may be approximately 60 μm or more, or may be approximately 70 μm or more. This allows the release film to have a sufficient thickness, and it is possible to prevent the phenomenon (dents) in which the smoothness of the adhesive sheet surface is impaired through the release film. In addition, from the viewpoint of the handleability of the release film (for example, ease of rolling), the thickness of the release film is suitably 300 μm or less, preferably 250 μm or less, may be 200 μm or less, may be 150 μm or less, or may be 130 μm or less. In some preferred embodiments, the thickness of the release film is approximately 125 μm or less, and may be approximately 115 μm or less, approximately 105 μm or less, or approximately 90 μm or less. By making the thickness of the release film equal to or less than a predetermined value, the film is less likely to leave a rolling mark when rolled, is easier to remove from the adhesive sheet, and the adhesive surface of the adhesive sheet is more likely to maintain a high level of surface smoothness even after the release film is removed.

In an embodiment having a first and second release film, the thickness of the first release film and the second release film may be the same or different. From the viewpoint of peeling workability, etc., it is preferable that the first release film and the second release film have different thicknesses, and it is preferable that the thickness of the thicker release film is approximately 1.1 times or more, for example approximately 1.25 times or more, the thickness of the thinner release film.

If necessary, a carrier or auxiliary film may be attached to the back of the release film. The presence of such a back auxiliary film can make it easier to prevent dents even in an embodiment in which a thin release film is used, and can improve the workability of punching and other processes. As such a back auxiliary film, a known or commonly used adhesive tape with a resin film substrate can be used.

<Release strength of release film>
The adhesive sheet with a release film disclosed herein preferably has the peeling force of the release film against the adhesive sheet limited to a predetermined value or less. This makes it easier to obtain a smoother adhesive surface by suppressing the fine undulation of the adhesive surface due to the so-called stick-slip phenomenon caused by peeling from the release film when the release film is removed from the adhesive surface during use of the adhesive sheet. In some preferred embodiments, the peeling force of the release film is approximately 1 N/50 mm or less, more preferably less than 0.90 N/50 mm, even more preferably less than 0.70 N/50 mm, particularly preferably less than 0.50 N/50 mm, and may be less than 0.40 N/50 mm, less than 0.30 N/50 mm, less than 0.20 N/50 mm, or less than 0.10 N/50 mm. The lower limit of the peeling force of the release film is, for example, 0.01 N/50 mm or more, and may be 0.05 N/50 mm or more from the viewpoint of the protection and lifting prevention of the release film. The release strength of the release film can be adjusted by, for example, subjecting the surface of the release film to a release treatment.

In an embodiment having a first and second release film, it is preferable that the release force of the first release film and the release force of the second release film with respect to the adhesive sheet are different from the viewpoint of peeling workability. For example, the release force of the release film on the heavy release side (e.g., the second release film) is suitably about 1.2 times or more than the release force of the release film on the light release side (e.g., the first release film), preferably about 1.4 times or more, may be about 1.5 times or more, or may be about 1.8 times or more. From the viewpoint of maintaining light release properties, it is suitable that the release force of the release film on the heavy release side (e.g., the second release film) is about 3 times or less than the release force of the release film on the light release side (e.g., the first release film), and may be about 2 times or less.

The peel strength of the release film is measured by preparing an adhesive sheet with a release film cut to a length of 150 mm and a width of 50 mm, in an atmosphere of 23°C and 50% RH, at a pulling speed of 300 mm/min and a peel angle of 180°. Specifically, it is measured by the method described in the Examples below.

<Adhesive sheet>
(Surface properties of adhesive surface)
The adhesive sheet disclosed herein has an adhesive surface whose maximum height Rz is limited to a predetermined value or less. A configuration having an adhesive surface designed to have a low maximum height Rz can have high surface smoothness and can be free of optical distortion or can have optical distortion suppressed. Such an adhesive sheet can be one that does not impair the design of the adherend, for example, its aesthetic appearance, or its luxurious feel, when the adherend surface is viewed through the adhesive sheet. When the adhesive sheet is in the form of a double-sided adhesive sheet having adhesive surfaces on both sides, it is appropriate that the maximum heights Rz of the first adhesive surface and the second adhesive surface constituting the double-sided adhesive sheet are limited to a predetermined value or less. By having each adhesive surface of the double-sided adhesive sheet have high surface smoothness, adhesion can be achieved with no optical distortion or with optical distortion highly suppressed. For example, when one of the adherends is a transparent member and the other is an adherend having a design, the design of the adherend can be well viewed through the adhesive sheet.

The maximum height Rz of the adhesive surface of the adhesive sheet (including the first adhesive surface and the second adhesive surface; the same applies below unless otherwise specified) is preferably about 600 nm or less, more preferably about 500 nm or less, even more preferably about 450 nm or less, and particularly preferably about 400 nm or less, and may be less than 350 nm, less than 300 nm, or less than 250 nm. From the viewpoint of production efficiency, etc., in some embodiments, the maximum height Rz of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 50 nm or more, about 100 nm or more, or about 200 nm or more. In an embodiment in which the adhesive sheet has a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be about the same or different.

The adhesive surface of the adhesive sheet disclosed herein is preferably limited to a predetermined value or less in arithmetic mean roughness Ra. A configuration having an adhesive surface designed to have a low arithmetic mean roughness Ra makes it easier to highly suppress optical distortion. When the adhesive sheet is in the form of a double-sided adhesive sheet having adhesive surfaces on both sides, it is appropriate that the arithmetic mean roughness Ra of the first adhesive surface and the second adhesive surface constituting the double-sided adhesive sheet are limited to a predetermined value or less. By having each adhesive surface of the double-sided adhesive sheet have high surface smoothness, adhesion with no optical distortion or with optical distortion highly suppressed can be preferably achieved.

The arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet is preferably about 70 nm or less, more preferably about 65 nm or less, and even more preferably about 55 nm or less, and may be less than 50 nm, less than 45 nm, or less than 40 nm. From the viewpoint of production efficiency, etc., in some embodiments, the arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 20 nm or more, or about 30 nm or more (e.g., about 40 nm or more). In an embodiment in which the adhesive sheet has a first adhesive surface and a second adhesive surface, the arithmetic mean roughness Ra of the first adhesive surface and the arithmetic mean roughness Ra of the second adhesive surface may be about the same or different.

The maximum height Rz and arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet can be adjusted depending on the surface properties of the release film laminated on the adhesive surface, the peeling force of the release film from the adhesive sheet, the thickness of the adhesive layer, etc.

The maximum height Rz of the adhesive surface of the adhesive sheet may be the maximum height Rz of the adhesive layer surface constituting the adhesive sheet. Similarly, the arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet may be the arithmetic mean roughness Ra of the adhesive layer surface constituting the adhesive sheet. Therefore, the ranges and values described above as the maximum height Rz and arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet may be adopted as the ranges and values of the maximum height Rz and arithmetic mean roughness Ra of the adhesive layer surface.

The maximum height Rz and arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet are measured using a non-contact surface roughness measuring device for the adhesive surface of the adhesive sheet after the release film has been peeled off from the adhesive sheet with release film. As the non-contact surface roughness measuring device, a surface roughness measuring device using an optical interference method is used, and for example, a three-dimensional optical profiler (product name "NewView7300", manufactured by ZYGO Corporation) or an equivalent product can be used. The specific measurement operation and measurement conditions can be set according to the measurement conditions described in the examples below, or so as to obtain results equivalent to or corresponding to those obtained when the measurement conditions are followed.

(Total light transmittance)
In some embodiments, the total light transmittance of the pressure-sensitive adhesive sheet is, for example, about 50% or more, and is preferably, for example, about 70% or more. From the viewpoint of visibility of the adherend through the pressure-sensitive adhesive sheet, in some preferred embodiments, the total light transmittance of the pressure-sensitive adhesive sheet is about 85% or more, more preferably about 90% or more. Theoretically, the upper limit of the total light transmittance is a value obtained by subtracting the light loss (Fresnel loss) caused by reflection at the air interface from 100%, and in practical use, it may be about 95% or less, or about 94% or less (for example, 93% or less). With a pressure-sensitive adhesive sheet having such a total light transmittance, good visibility can be obtained through the pressure-sensitive adhesive sheet.

(Haze value)
In some embodiments, the haze value of the pressure-sensitive adhesive sheet is, for example, about 10% or less, and it is appropriate to set it to about 3% or less. From the viewpoint of visibility of the adherend through the pressure-sensitive adhesive sheet, in some preferred embodiments, the haze value of the pressure-sensitive adhesive sheet is about 1% or less, more preferably about 0.8% or less, and even more preferably 0.5% or less. The lower limit of the haze value is theoretically 0%, and in practice, it may be more than about 0.0%. The "haze value" refers to the ratio of diffuse transmitted light to the total transmitted light when visible light is irradiated on the measurement target. It is also called the cloudiness value. The haze value can be expressed by the following formula.
Th[%]=Td/Tt×100
In the above formula, Th is the haze value [%], Td is the scattered light transmittance, and Tt is the total light transmittance.

The total light transmittance and haze value of the pressure-sensitive adhesive sheet can be adjusted by the composition (base polymer type and added components) and thickness of the pressure-sensitive adhesive sheet (typically the pressure-sensitive adhesive layer).

The total light transmittance of the pressure-sensitive adhesive sheet may be the total light transmittance of the pressure-sensitive adhesive layer that constitutes the pressure-sensitive adhesive sheet. Similarly, the haze value of the pressure-sensitive adhesive sheet may be the haze value of the pressure-sensitive adhesive layer that constitutes the pressure-sensitive adhesive sheet. Therefore, the ranges and values described above as the total light transmittance and haze value of the pressure-sensitive adhesive sheet can be adopted as the ranges and values of the total light transmittance and haze value of the pressure-sensitive adhesive layer.

The total light transmittance and haze value of the adhesive sheet can be measured by attaching the adhesive sheet to be measured to one side of a glass plate and using a haze meter. The haze meter can be an instrument manufactured by Murakami Color Research Laboratory called "HM-150N" or an equivalent. Specifically, the measurements are performed using the method described in the Examples below.

The adhesive sheet having the total light transmittance and haze value as described above may be a colored transparent or colorless transparent adhesive sheet. In this specification, the term "transparent" is used in a sense that includes translucency. In addition, the optical distortion reduction effect of the adhesive sheet according to the technology disclosed herein can be achieved in a configuration in which at least a portion of the adhesive sheet surface has a degree of transparency that allows visibility through the adhesive sheet, so the adhesive sheet does not need to be transparent or translucent.

(Adhesion to glass)
The adhesive strength of the adhesive sheet disclosed herein is not particularly limited and can be set according to the purpose. In some embodiments, the adhesive strength of the adhesive sheet to a glass plate (adhesive strength to glass) is, for example, about 1.0 N/20 mm or more, and may be about 3.0 N/20 mm or more (for example, about 5.0 N/20 mm or more). From the viewpoint of bonding reliability, the adhesive strength to glass is preferably about 7.0 N/20 mm or more, more preferably about 8.0 N/20 mm or more, even more preferably about 9.0 N/20 mm or more, and may be about 10.0 N/20 mm or more, or may be about 11.0 N/20 mm or more. The adhesive sheet having the above adhesive strength to glass can be preferably used for purposes such as bonding and fixing of members. From the viewpoint of easily achieving a balance with other properties, the adhesive strength to glass may be, for example, about 20 N/20 mm or less, about 16.0 N/20 mm or less, or about 12.0 N/20 mm or less. The adhesive strength to glass can be adjusted by selecting the composition, thickness, etc. of the pressure-sensitive adhesive layer.

The adhesive strength to glass is determined by pressing the adhesive surface to be measured against a glass plate by rolling a 2 kg rubber roller back and forth once, and measuring the peel strength when peeling the adhesive sheet from the glass plate at a peel angle of 180 degrees and a tensile speed of 300 mm/min in accordance with JIS Z 0237 using a tensile tester in an environment of 23°C and 50% RH. Specifically, it is measured by the method described in the Examples below.

(Elastic modulus by tensile test)
In some preferred embodiments, the adhesive sheet has a modulus of elasticity (also referred to as initial modulus of elasticity) of 3.0 MPa or more in a tensile test. Adhesive sheets with a higher modulus of elasticity tend to exhibit better deformation resistance. The adhesive sheet with a high modulus of elasticity can be preferably used for purposes such as joining and fixing members. For example, in an embodiment in which two members are joined via an adhesive sheet, the high deformation resistance of the adhesive sheet can be useful for precisely maintaining the relative positions of the two members. In addition, in an embodiment in which a film member and another member are joined via an adhesive sheet, the high deformation resistance of the adhesive sheet can be useful for suppressing a phenomenon in which the appearance of the laminate changes due to local pressure from the film member side (pressure deformation resistance). In an embodiment in which the adherend is a rigid member having transparency (e.g., a glass member), it is particularly meaningful to suppress a change in appearance visually recognized from the adherend side.

In some preferred embodiments of the pressure-sensitive adhesive sheet, the elastic modulus may be, for example, 5.0 MPa or more, 7.0 MPa or more, 10.0 MPa or more, 15.0 MPa or more, or 20.0 MPa or more. The increase in the elastic modulus tends to improve the deformation resistance. The upper limit of the elastic modulus is not particularly limited. From the viewpoint of easily achieving a balance with other properties (e.g., one or more properties selected from impact resistance, adhesion to glass, haze value, etc.), the elastic modulus is advantageously 150 MPa or less, preferably 120 MPa or less, may be 100 MPa or less, may be 80 MPa or less, or may be 60 MPa or less. The elastic modulus measured by the tensile test can be adjusted by selecting the composition of the pressure-sensitive adhesive sheet (typically the pressure-sensitive adhesive layer), etc. The elastic modulus measured by the tensile test is measured by the above-mentioned tensile test. More specifically, it is measured by the method described in the examples below.

(Impact resistance)
The pressure-sensitive adhesive sheet disclosed herein preferably has an impact resistance of 2.0 J/10 ^mm2 or more. A highly reliable bond can be formed by the pressure-sensitive adhesive sheet having high impact resistance. This can be an advantageous feature for a pressure-sensitive adhesive sheet used for joining or fixing members, for example. Even if such a pressure-sensitive adhesive sheet is subjected to an impact due to, for example, a fall or a collision, it can withstand the impact and maintain good bonding between the member and the adherend.

In some preferred embodiments of the pressure-sensitive adhesive sheet, the impact resistance may be, for example, 2.1 J/10 mm ² or more, 2.3 J/10 mm ² or more, 2.5 J/10 mm ² or more, 2.7 J/10 mm ² or more, or 3.0 J/10 mm ² or more. The pressure-sensitive adhesive sheet disclosed herein may also be preferably implemented in an embodiment in which the impact resistance is 3.3 J/10 mm ² or more or 3.5 J/10 mm ² or more. The upper limit of the impact resistance is not particularly limited. From the viewpoint of easily achieving a balance with other properties, the impact resistance may be, for example, 20 J/10 mm ² or less, 15 J/10 mm ² or less, 10 J/10 mm ² or less, 8.0 J/10 mm ² , or 6.0 J/10 mm ² or less. The impact resistance can be adjusted by selecting the composition, thickness, etc. of the pressure-sensitive adhesive layer. The impact resistance is measured by the above-mentioned shear impact test, more specifically, by the method described in the examples below.

(Thickness)
The thickness of the adhesive sheet is appropriately set according to the purpose and mode of use, and is not limited to a specific range. The thickness of the adhesive sheet may be, for example, about 1 μm to 500 μm, for example, about 3 μm to 500 μm. In some embodiments, the thickness of the adhesive sheet is suitably 5 μm or more, for example, may be 10 μm or more, preferably 20 μm or more, more preferably 25 μm or more, and may be more than 25 μm. In a thick adhesive sheet, optical distortion is likely to be reduced due to the stress dispersion ability of the adhesive layer. In addition, a thick adhesive sheet tends to have excellent step followability and is easy to absorb deformation due to foreign matter, etc. Impact resistance also tends to be improved. The technology disclosed herein can be preferably implemented in an embodiment in which the thickness of the adhesive sheet is 30 μm or more. The thickness of the adhesive sheet may be 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 75 μm or more, or 90 μm or more. On the other hand, when the thickness of the pressure-sensitive adhesive sheet is increased, the optical path passing through the pressure-sensitive adhesive sheet is also increased, so that optical distortion is easily recognized. Therefore, in some embodiments, the thickness of the pressure-sensitive adhesive sheet is suitably set to, for example, 200 μm or less, and may be 150 μm or less, 120 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, or 35 μm or less.

<Adhesive Layer>
In the technology disclosed herein, the type of adhesive constituting the adhesive layer contained in the adhesive sheet is not particularly limited. The adhesive layer may be an adhesive layer composed of one or more adhesives selected from various known adhesives such as acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, a mixture of these, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorine adhesives. Here, the acrylic adhesive refers to an adhesive that uses an acrylic polymer as the base polymer (the main component of the polymer component, i.e., a component that is contained in an amount of more than 50% by weight). The same applies to rubber adhesives and other adhesives.

(Polymer (A))
In some embodiments, the pressure-sensitive adhesive layer contains a polymer (A). Examples of materials that can be used as the polymer (A) include polymers that exhibit rubber elasticity at room temperature, such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers, which are known in the field of pressure-sensitive adhesives. These can be used alone or in combination of two or more.

The weight ratio of the polymer (A) to the total weight of the adhesive layer is preferably 40% by weight or more, more preferably 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more, and may be approximately 80% by weight or more, approximately 90% by weight or more, or approximately 97% by weight or more (for example, approximately 99% by weight or more). Adhesives with a high content of polymer (A) tend to have excellent transparency. In addition, the weight ratio of the polymer (A) to the total weight of the adhesive layer is typically less than 100% by weight, and from the viewpoint of easily adjusting the balance of properties, it is advantageous to be 95% by weight or less, preferably 92% by weight or less, and may be 90% by weight or less, or may be 87% by weight or less.

An example of a suitable polymer (A) is an acrylic polymer. The adhesive layer in the technology disclosed herein may be an acrylic adhesive layer containing an acrylic polymer as a base polymer (the main component of the polymer component, i.e., a component that accounts for more than 50% by weight). Acrylic adhesives are preferred from the viewpoints of transparency and weather resistance, and are easy to realize viscoelastic properties with excellent impact resistance without relying heavily on additives such as softeners. The acrylic polymer (hereinafter sometimes referred to as "acrylic polymer (A)") as polymer (A) is preferably an acrylic polymer composed of a monomer component containing 40% by weight or more of (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having X to Y carbon atoms at the ester terminal may be referred to as "(meth)acrylic acid C _X-Y alkyl ester".

In some embodiments, the proportion of the C _1-20 (meth)acrylic acid alkyl ester in the entire monomer components of the acrylic polymer (A) is suitably more than 40% by weight, for example, 45% by weight or more, 50% by weight or more, 55% by weight or more, or 60% by weight or more, since it is easy to balance the properties. The proportion of the C _1-20 (meth)acrylic acid alkyl ester in the entire monomer components may be 100% by weight, but is suitably 98% by weight or less, for example, 95% by weight or less, or 90% by weight or less, since it is easy to balance the properties. In some embodiments, the proportion of the C _1-20 (meth)acrylic acid alkyl ester in the entire monomer components of the acrylic polymer (A) may be, for example, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, or 60% by weight or less, from the viewpoint of improving the cohesiveness of the pressure-sensitive adhesive layer.

Non-limiting specific examples of the (meth)acrylic acid C _1-20 alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and (meth)acrylic acid. Examples of the acrylates include isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

Of these, it is preferable to use at least a (meth)acrylic acid C _4-20 alkyl ester, and it is more preferable to use at least a (meth)acrylic acid C _4-18 alkyl ester. Particularly preferable (meth)acrylic acid C _4-18 alkyl esters include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). Other specific examples of (meth)acrylic acid C _4-20 alkyl esters that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), and the like. These (meth)acrylic acid C _4-20 alkyl esters can be used alone or in combination of two or more.

The monomer component preferably contains, for example, either one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). In some embodiments, the monomer component preferably contains at least BA. Here, examples of monomer components containing at least BA include monomer components having a composition that contains BA but not 2EHA, and monomer components having a composition that contains BA and 2EHA, and in which the content of 2EHA is less than the content of BA (for example, the content of 2EHA is less than 0.5 or 0.3 times the content of BA).

In some embodiments, the monomer component constituting the acrylic polymer (A) may contain 40% by weight or more of the (meth)acrylic acid _C4-18 alkyl ester. The proportion of the (meth)acrylic acid _C4-18 alkyl ester in the monomer component may be, for example, 50% by weight or more, 60% by weight or more, or 65% by weight or more.
Furthermore, from the viewpoint of enhancing the cohesiveness of the pressure-sensitive adhesive layer, the ratio of the (meth)acrylic acid _C4-18 alkyl ester in the monomer components is suitably 99.5% by weight or less, may be 95% by weight or less, may be 85% by weight or less, or may be 75% by weight or less.

The monomer components constituting the acrylic polymer (A) may contain, in addition to the (meth)acrylic acid alkyl ester, other monomers (copolymerizable monomers) that can be copolymerized with the (meth)acrylic acid alkyl ester, if necessary. As the copolymerizable monomer, a monomer having a polar group (e.g., a carboxyl group, a hydroxyl group, a nitrogen atom-containing ring, etc.) or a monomer having a relatively high homopolymer glass transition temperature (e.g., 10°C or higher) can be suitably used. The monomer having a polar group can be useful for introducing crosslinking points into the acrylic polymer (A) or for increasing the cohesive strength of the adhesive. The copolymerizable monomers can be used alone or in combination of two or more.

Non-limiting examples of copolymerizable monomers include the following:
Carboxy group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.
Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride.
Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.
Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloylphosphate, and the like.
Epoxy group-containing monomers: for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl ether (meth)acrylate, allyl glycidyl ether, and glycidyl ether (meth)acrylate.
Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile, etc.
Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate.
Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)(meth)acrylamide; N-hydroxyalkyl (meth)acrylamides such as N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, and N-(4-hydroxybutyl) (meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl (meth)acrylamide such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; and others, N,N-dimethylaminopropyl (meth)acrylamide, N-(meth)acryloylmorpholine, and the like.
Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Monomers having an epoxy group: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, etc. (for example, lactams such as N-vinyl-2-caprolactam).
Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, and the like.
Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, and the like.
Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and the like.
Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate.
Alkoxy group-containing monomers: for example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; alkoxyalkylene (meth)acrylates (for example, alkoxypolyalkylene glycol (meth)acrylates) such as methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.
Alkoxysilyl group-containing monomers: for example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane.
Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.
Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene, etc.
(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, (meth)acrylates containing an alicyclic hydrocarbon group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.
(Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, (meth)acrylates containing an aromatic hydrocarbon group such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate.
Other examples include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from alcohols derived from terpene compounds.

When such a copolymerizable monomer is used, the amount used is not particularly limited, but it is appropriate that it is 0.01% by weight or more of the total monomer components. From the viewpoint of better exerting the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1% by weight or more of the total monomer components, or may be 0.5% by weight or more. Also, from the viewpoint of easily balancing the adhesive properties, it is appropriate that the amount of the copolymerizable monomer used is 50% by weight or less of the total monomer components, and preferably 40% by weight or less.

で表わされるＮ－ビニル環状アミドを用いることができる。ここで、一般式（１）中、Ｒ¹は２価の有機基であり、具体的には－（ＣＨ₂）_ｎ－である。ｎは２～７（好ましくは２，３または４）の整数である。なかでも、Ｎ－ビニル－２－ピロリドンを好ましく採用し得る。窒素原子を有するモノマーの他の好適例としては、（メタ）アクリルアミドが挙げられる。 In some embodiments, the monomer component constituting the acrylic polymer (A) may contain a monomer having a nitrogen atom. The use of a monomer having a nitrogen atom can increase the cohesive strength of the adhesive and favorably improve the peel strength after photocuring. A suitable example of a monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring. The monomer having a nitrogen atom-containing ring can be one of those exemplified above, for example, a monomer represented by the general formula (1):

In the general formula (1), R ¹ is a divalent organic group, specifically, -(CH ₂ ) _n -. n is an integer of 2 to 7 (preferably 2, 3, or 4). Of these, N-vinyl-2-pyrrolidone is preferably used. Another suitable example of a monomer having a nitrogen atom is (meth)acrylamide.

The amount of the monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) used is not particularly limited, and may be, for example, 1% by weight or more, 3% by weight or more, or even 5% by weight or more or 7% by weight or more of the total monomer components. In some embodiments, the amount of the monomer having a nitrogen atom used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer components. In addition, the amount of the monomer having a nitrogen atom used is suitably, for example, 40% by weight or less of the total monomer components, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. In some other embodiments, the amount of the monomer having a nitrogen atom used may be, for example, 20% by weight or less, or 15% by weight or less of the total monomer components.

In some embodiments, the monomer components constituting the acrylic polymer (A) may include a hydroxyl group-containing monomer. By using a hydroxyl group-containing monomer, the cohesive strength of the adhesive and the degree of crosslinking (for example, crosslinking by an isocyanate crosslinking agent) can be suitably adjusted. When a hydroxyl group-containing monomer is used, the amount used is not particularly limited, and may be, for example, 0.01% by weight or more of the total monomer components, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 5% by weight or more, or 10% by weight or more. In addition, from the viewpoint of suppressing the water absorption of the adhesive layer, in some embodiments, the amount of the hydroxyl group-containing monomer used is suitably, for example, 40% by weight or less of the total monomer components, and may be 30% by weight or less, 25% by weight or less, or 20% by weight or less. In some other embodiments, the amount of the hydroxyl group-containing monomer used may be, for example, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer components.

In some embodiments, the proportion of the carboxyl group-containing monomer in the monomer components of the acrylic polymer (A) may be, for example, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less (for example, less than 0.1% by weight). The acrylic polymer (A) may not substantially use a carboxyl group-containing monomer as a monomer component. Here, substantially not using a carboxyl group-containing monomer means that at least intentionally not using a carboxyl group-containing monomer. As described above, a pressure-sensitive adhesive layer containing an acrylic polymer (A) in which the amount of the carboxyl group-containing monomer used is limited is preferable from the viewpoint of preventing metal corrosion. A pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer may be preferably used, for example, in an embodiment in which the pressure-sensitive adhesive layer contacts an adherend having a metal material.

In some embodiments, the monomer component constituting the acrylic polymer (A) may contain an alicyclic hydrocarbon group-containing (meth)acrylate. This can increase the cohesive force of the adhesive and improve the peel strength after photocuring. As the alicyclic hydrocarbon group-containing (meth)acrylate, the above-mentioned examples can be used, and for example, cyclohexyl acrylate and isobornyl acrylate can be preferably used. When an alicyclic hydrocarbon group-containing (meth)acrylate is used, the amount used is not particularly limited, and can be, for example, 1% by weight or more, 3% by weight or more, or 5% by weight or more of the total monomer components. In some embodiments, the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used may be 10% by weight or more, or 15% by weight or more of the total monomer components. The upper limit of the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is suitably about 40% by weight or less, and may be, for example, 30% by weight or less, or 25% by weight or less (for example, 15% by weight or less, or even 10% by weight or less).

The polymerization method for forming (synthesizing) the polymer (A) from the monomer components is not particularly limited, and various conventionally known polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically carried out in the presence of a thermal polymerization initiator); photopolymerization carried out by irradiating with light such as ultraviolet light (typically carried out in the presence of a photopolymerization initiator); radiation polymerization carried out by irradiating with radiation such as β rays and γ rays; and other polymerization methods can be appropriately adopted. Two or more polymerization methods may be combined (for example, stepwise) to be carried out.

As the solvent for solution polymerization (polymerization solvent), for example, any one of the following solvents or a mixture of two or more solvents can be used: aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.

In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator may be used depending on the polymerization method, polymerization mode, etc. Such polymerization initiators may be used alone or in appropriate combination of two or more types.

The thermal polymerization initiator is not particularly limited, but may be, for example, an azo polymerization initiator, a peroxide initiator, a redox initiator formed by combining a peroxide with a reducing agent, or a substituted ethane initiator. More specifically, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2- Examples of initiators include, but are not limited to, azo initiators such as methylpropionamidine hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; redox initiators such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate; and the like. Thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C), but is not limited thereto.

The photopolymerization initiator is not particularly limited, but examples that can be used include ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators.

The amount of polymerization initiator used is not particularly limited and may be a normal amount depending on the polymerization method and polymerization mode. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, e.g., about 0.01 to 1 part by weight) of polymerization initiator can be used per 100 parts by weight of monomer to be polymerized.

In the above polymerization, various conventionally known chain transfer agents (which may also be understood as molecular weight regulators or polymerization degree regulators) may be used as necessary. As chain transfer agents, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol may be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. Specific examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; styrenes such as α-methylstyrene and α-methylstyrene dimer; compounds having a benzylidene group such as dibenzylideneacetone, cinnamyl alcohol, and cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; olefins such as 2,3-dimethyl-2-butene and 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene; and the like. The chain transfer agent can be used alone or in combination of two or more. The technology disclosed herein can also be preferably implemented in an embodiment in which no chain transfer agent is used.

When a chain transfer agent is used, the amount used may be, for example, about 0.005 to 1 part by weight per 100 parts by weight of the monomer component. In some embodiments, from the viewpoint of impact resistance, the amount of chain transfer agent used per 100 parts by weight of the monomer component may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, 0.05 parts by weight or more, or 0.07 parts by weight or more. In some embodiments, from the viewpoint of deformation resistance, the amount of chain transfer agent used per 100 parts by weight of the monomer component may be, for example, 0.5 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, or less than 0.1 parts by weight (for example, 0.09 parts by weight or less).

In the technology disclosed herein, the glass transition temperature (Tg) of the polymer (A) is not particularly limited, but is suitably less than 0°C, preferably less than -10°C, and preferably less than -20°C. The impact resistance tends to improve as the Tg of the polymer (A) decreases. In some embodiments, the Tg of the polymer (A) may be less than -25°C or less than -30°C. The Tg of the polymer (A) is typically -80°C or higher, and may be, for example, -70°C or higher, -60°C or higher, or -55°C or higher. From the viewpoint of increasing the elastic modulus, in some embodiments, the Tg of the polymer (A) is preferably -50°C or higher, more preferably -45°C or higher, and may be -40°C or higher, -38°C or higher, or -35°C or higher.

In this specification, the Tg of a polymer refers to the Tg calculated by the Fox formula based on the composition of the monomer components used in the preparation of the polymer. The Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)

In the above Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction (copolymerization ratio by weight) of monomer i in the copolymer, and Tgi is the glass transition temperature (unit: K) of the homopolymer of monomer i. When the target polymer for which Tg is specified is a homopolymer, the Tg of the homopolymer and the Tg of the target polymer are the same.

The glass transition temperature of the homopolymer used in calculating Tg is a value described in a publicly known document. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
n-Butyl acrylate -55℃
2-Ethylhexyl acrylate -70℃
Isostearyl acrylate -18℃
Cyclohexyl acrylate 15℃
N-vinyl-2-pyrrolidone 54℃
2-Hydroxyethyl acrylate -15℃
4-Hydroxybutyl acrylate -40℃

For the glass transition temperatures of homopolymers of monomers other than those listed above, the values given in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) should be used. If multiple values are given in this document, the highest value should be used.

The weight average molecular weight (Mw) of the polymer (A) is not particularly limited. From the viewpoint of achieving a good balance between deformation resistance and impact resistance, in some embodiments, the Mw of the polymer (A) is, for example, approximately 10 × 10 ⁴ or more, preferably more than 20 × 10 ⁴ , may be more than 30 × 10 ⁴ , may be more than 40 × 10 ⁴ , or may be more than 50 × 10 ^4. In addition, the upper limit of the Mw of the polymer (A) may be approximately 500 × 10 ⁴ or less. From the viewpoint of adhesion to the adherend and peel strength, in some embodiments, the Mw of the polymer (A) may be, for example, 300 × 10 ⁴ or less, 150 × 10 ⁴ or less, 100 × 10 ⁴ or less, 90 × 10 ⁴ or less, or 75 × 10 ⁴ or less.
The above examples of Mw may be applied to the Mw of the polymer (A) in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein, or may be applied to the Mw of the polymer (A) in the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer.

The Mw refers to a value calculated based on standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC device, for example, a model "HLC-8220GPC" (manufactured by Tosoh Corporation) or an equivalent device can be used. As the measurement conditions for GPC, for example, the following method is adopted. The Mw in the examples described later is measured by the following method.
(GPC measurement conditions)
Apparatus: Tosoh Corporation, HLC-8220GPC
column:
Sample column: Tosoh Corporation, TSKguard column Super HZ-H (1 column) + TSKgel Super HZM-H (2 columns)
Reference column: Tosoh Corporation, TSKgel Super H-RC (1 column)
Flow rate: 0.6mL/min
Injection volume: 10 μL
Column temperature: 40°C
Eluent: THF
Injected sample concentration: 0.2 wt%
Detector: differential refractometer Weight average molecular weight is calculated based on polystyrene standard.

(Photoreactive Monomer (B))
In some preferred embodiments, the pressure-sensitive adhesive layer may contain a photoreactive monomer (B) in addition to the polymer (A) (e.g., acrylic polymer (A)) as described above. As the photoreactive monomer (B), a compound having 2 or more ethylenically unsaturated groups in the molecule (hereinafter also referred to as the "functional group number"). The upper limit of the functional group number of the compound used as the photoreactive monomer (B) is not particularly limited. The functional group number may be, for example, 50 or less, 40 or less, 30 or less, 20 or less, or 15 or less. In some embodiments, a compound having an ethylenically unsaturated group with a functional group number of, for example, 2 to 10 may be used, and it is preferable to use a compound with a functional group number of 2 to 8, and it is more preferable to use a compound with a functional group number of 2 to 6. The photoreactive monomer (B) may be used alone or in combination of two or more kinds.

The photoreactive monomer (B) contained in the adhesive layer can form a crosslinked structure by reacting the ethylenically unsaturated groups with light (e.g., ultraviolet) irradiation or the like after application to an adherend. The adhesive sheet containing the photoreactive monomer (B) in the adhesive layer can increase the deformation resistance of the adhesive layer by curing the adhesive layer by ultraviolet irradiation or the like after application to an adherend. This can favorably achieve both good conformability to the surface shape of the adherend when applied to the adherend and high deformation resistance after application.

Examples of the ethylenically unsaturated group include, but are not limited to, an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. The two or more ethylenically unsaturated groups contained in the molecule of the photoreactive monomer (B) may be the same group, or may be two or more different groups. From the viewpoint of photoreactivity, preferred ethylenically unsaturated groups include an acryloyl group and a methacryloyl group. Of these, an acryloyl group is preferred.

The functional group equivalent of the compound used as the photoreactive monomer (B) is not particularly limited. The functional group equivalent may be, for example, about 50 to 10,000 g/mol, about 50 to 8,000 g/mol, about 50 to 5,000 g/mol, about 50 to 3,000 g/mol, or about 50 to 2,000 g/mol. In some embodiments, from the viewpoint of photocurability, a compound having a functional group equivalent of about 60 to 800 g/mol (more preferably about 80 to 600 g/mol) may be preferably used as the photoreactive monomer (B).

The functional group equivalent of the photoreactive monomer (B) is calculated by dividing the molecular weight [g/mol] of the photoreactive monomer (B) by the number of ethylenically unsaturated functional groups contained in the photoreactive monomer (B). The molecular weight of the photoreactive monomer (B) can be obtained, for example, by the GPC method as a weight average molecular weight converted into standard polystyrene. The molecular weight [g/mol] of the photoreactive monomer (B) may be the manufacturer's nominal value or a molecular weight calculated from the molecular structure.

The molecular weight of the photoreactive monomer (B) is not particularly limited and may be selected so that the desired effect is preferably exhibited. For example, a photoreactive monomer (B) having a molecular weight of approximately 20,000 or less may be used. From the viewpoint of ease of preparation and coatability of the adhesive composition, in some embodiments, the molecular weight of the photoreactive monomer (B) may be, for example, 16,000 or less, 10,000 or less, 4,000 or less, 1,500 or less, or 1,000 or less. The molecular weight of the photoreactive monomer (B) is, for example, 100 or more, typically 120 or more. From the viewpoint of processability and handleability of the adhesive sheet, in some embodiments, the molecular weight of the photoreactive monomer (B) may be, for example, 150 or more, 200 or more, 280 or more, 350 or more, 420 or more, 480 or more, or 550 or more.

In the adhesive sheet disclosed herein, the amount of photoreactive monomer (B) contained in the adhesive layer is not particularly limited and can be appropriately set according to the target performance (e.g., the elastic modulus of the adhesive layer after photocuring). In some embodiments in which the adhesive layer contains a polymer (A) and a photoreactive monomer (B), the amount of photoreactive monomer (B) per 100 parts by weight of the polymer (A) contained in the adhesive layer may be, for example, 1 part by weight or more, and is suitably 3 parts by weight or more. From the viewpoint of making it easier to increase the elastic modulus of the adhesive layer after photocuring, the amount of photoreactive monomer (B) per 100 parts by weight of the polymer (A) may be 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. In addition, from the viewpoint of the cohesiveness of the adhesive layer before photocuring and the handleability (e.g., processability) of the adhesive sheet, the amount of photoreactive monomer (B) per 100 parts by weight of polymer (A) is suitably 80 parts by weight or less, preferably 60 parts by weight or less, may be 50 parts by weight or less, 40 parts by weight or less, or may be 35 parts by weight or less.

In some embodiments, the pressure-sensitive adhesive layer preferably contains at least a compound B1 having a ring structure and two or more ethylenically unsaturated groups in the molecule as the photoreactive monomer (B). The pressure-sensitive adhesive layer containing the compound B1 of such a structure can effectively increase the deformation resistance of the pressure-sensitive adhesive layer by light irradiation. The ring in the ring structure may be an aliphatic ring or an aromatic ring. The ring may be a carbon ring or a heterocycle. The number of rings contained in one molecule of compound B1 may be 1 or 2 or more. The upper limit of the number of rings contained in compound B1 is not particularly limited, and may be, for example, 100 or less, 70 or less, 50 or less, 30 or less, 15 or less, 8 or less, 6 or less, 5 or less, or 4 or less. When compound B1 contains two or more rings, the rings may or may not form a condensed ring (typically a bicyclic or tricyclic condensed ring) by one or two or more rings. The ring is preferably included in the main chain of compound B1. In other words, it is preferable that one ethylenically unsaturated group in compound B1 and at least one other ethylenically unsaturated group are linked via the ring structure. Compound B1 can be used alone or in combination of two or more.

As the compound B1, a compound having a ring structure and two or more ethylenically unsaturated groups in the molecule and a functional group equivalent of 100 g/mol or more can be preferably used. A pressure-sensitive adhesive sheet containing the compound B1 satisfying the above functional group equivalent in the pressure-sensitive adhesive layer can suitably form a bond with high deformation resistance and high impact resistance. The reason for obtaining such an effect is not particularly limited, but it is considered that the rigidity of the ring structure of the compound B1 can effectively increase the elastic modulus of the pressure-sensitive adhesive layer after light irradiation to impart deformation resistance, while the functional group equivalent of the compound B1 is a predetermined value or more, so that the distance between the crosslinking points can be maintained and a crosslinking structure with high impact resistance can be formed. In some embodiments, the functional group equivalent of the compound B1 may be, for example, 120 g/mol or more, 150 g/mol or more, 180 g/mol or more, 230 g/mol or more, 280 g/mol or more, 320 g/mol or more, or 350 g/mol or more. Increasing the functional group equivalent of compound B1 tends to improve impact resistance. The functional group equivalent of compound B1 may be, for example, 10,000 g/mol or less, 8,000 g/mol or less, 5,000 g/mol or less, 3,000 g/mol or less, or 2,000 g/mol or less. In some embodiments, from the viewpoint of photocurability and the like, the functional group equivalent of compound B1 is preferably 800 g/mol or less, more preferably 600 g/mol or less. In some embodiments, the functional group equivalent of compound B1 may be 500 g/mol or less, 400 g/mol or less, or 300 g/mol or less.

In some embodiments, the number of functional groups of compound B1 may be, for example, 2 to 50, 2 to 40, 2 to 30, or 2 to 10, and is preferably, for example, 2 to 6, 2 to 4, or 2 to 3. In some embodiments, compound B1 having 2 functional groups may be preferably used.

Compound B1 may have a functional group other than an ethylenically unsaturated group. Examples of functional groups other than an ethylenically unsaturated group include a hydroxyl group, a carboxyl group, and an amino group. Preferred examples of functional groups other than an ethylenically unsaturated group include a hydroxyl group and an amino group.

Examples of compound B1 include bisphenol A type epoxy (meth)acrylates such as bisphenol A glycidyl ether (meth)acrylic acid adduct, bisphenol A glycidyl amine (meth)acrylic acid adduct, and bisphenol A glycidyl ester (meth)acrylic acid adduct; alkylene oxide modified bisphenol A (meth)acrylates such as ethylene oxide (EO) modified bisphenol A di(meth)acrylate and propylene oxide (PO) modified bisphenol A di(meth)acrylate; bisphenol F type epoxys such as bisphenol F glycidyl ether (meth)acrylic acid adduct, bisphenol F glycidyl amine (meth)acrylic acid adduct, and bisphenol F glycidyl ester (meth)acrylic acid adduct. bisphenol F di(meth)acrylate; alkylene oxide modified bisphenol F (meth)acrylate such as EO modified bisphenol F di(meth)acrylate and PO modified bisphenol F di(meth)acrylate; bisphenol E type epoxy (meth)acrylate such as bisphenol E glycidyl ether (meth)acrylic acid adduct, bisphenol E glycidyl amine (meth)acrylic acid adduct and bisphenol E glycidyl ester (meth)acrylic acid adduct; alkylene oxide modified bisphenol E (meth)acrylate such as EO modified bisphenol E di(meth)acrylate and PO modified bisphenol E di(meth)acrylate; 9,9-bis(4-hydroxyphenyl)fluorenedi(meth)acrylate, 9,9-bis[4- (meth)acrylates containing a fluorene skeleton, such as [(2-hydroxyethoxy)phenyl]fluorene di(meth)acrylate; (meth)acrylates having an aliphatic ring (which may be an alicyclic condensed ring), such as tricyclodecane dimethanol di(meth)acrylate, hydrogenated bisphenol A type epoxy (meth)acrylate, hydrogenated bisphenol F type epoxy (meth)acrylate, hydrogenated bisphenol E type epoxy (meth)acrylate, hydrogenated phthalic acid type epoxy (meth)acrylate, hydrogenated terpene phenol (meth)acrylate, and 1,4-cyclohexane dimethanol diglycidyl ether (meth)acrylate; (meth)acrylic acid adducts of novolac type epoxy resins; (meth)acrylic acid adducts of thioether type epoxy resins; naphtha (meth)acrylates having an aliphatic ring (which may be an alicyclic condensed ring), such as tricyclodecane dimethanol di(meth)acrylate, hydrogenated bisphenol A type epoxy (meth)acrylate, hydrogenated bisphenol F type epoxy (meth)acrylate, hydrogenated bisphenol E type epoxy (meth)acrylate, hydrogenated phthalic acid type epoxy (meth)acrylate, hydrogenated terpene phenol (meth)acrylate, and 1,4-cyclohexane dimethanol diglycidyl ether (meth)acrylate; (meth)acrylic acid adducts of novolac type epoxy resins; (meth)acrylic acid adducts of thioether type epoxy resins; Examples of the (meth)acrylic acid adduct include, but are not limited to, (meth)acrylic acid adducts of talc-type epoxy resins, (meth)acrylic acid adducts of dicyclopentadiene-type epoxy resins, (meth)acrylic acid adducts of alkyldiphenol-type epoxy resins, (meth)acrylic acid adducts of biphenyl-type epoxy resins, (meth)acrylic acid adducts of terpene phenol resins, isocyanurate-type (meth)acrylates such as tris(2-hydroxyethyl)isocyanurate di(meth)acrylate and tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, divinylbenzene, hydroquinone di(meth)acrylate, resorcinol di(meth)acrylate, and modified products of any of the above-mentioned materials (e.g., amine-modified products, acid-modified products, halogen-modified products). In some embodiments, a compound B1 having an aromatic carbon ring may be preferably used. Suitable examples of compound B1 include compounds containing a bisphenol A structure, such as bisphenol A type epoxy (meth)acrylate, alkylene oxide modified bisphenol A (meth)acrylate, and modified products thereof (e.g., amine modified products).

Commercially available products that can be used as compound B1 include, but are not limited to, products manufactured by Shin-Nakamura Chemical Co., Ltd. under the trade names "A-DCP" and "A-BPE-4", products manufactured by Osaka Organic Chemical Industry Co., Ltd. under the trade names "Viscoat #540" and "Viscoat #700HV", products manufactured by Nippon Kayaku Co., Ltd. under the trade names "Epoxy Ester 3000A" and "Epoxy Ester 80MFA" manufactured by Kyoeisha Chemical Co., Ltd., and products manufactured by Daicel Allnex under the trade names "EBECRYL 3700", "EBECRYL 3703", and "EBECRYL 3603".

The amount of compound B1 relative to 100 parts by weight of polymer (A) contained in the adhesive layer is not particularly limited, and can be, for example, 0.5 parts by weight or more. From the viewpoint of easily obtaining an adhesive layer that balances deformation resistance and impact resistance, in some embodiments, the amount of compound B1 relative to 100 parts by weight of polymer (A) may be, for example, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, or 15 parts by weight or more. In addition, from the viewpoint of the cohesiveness of the adhesive layer before photocuring and the handleability of the adhesive sheet, the amount of compound B1 relative to 100 parts by weight of polymer (A) is appropriately 80 parts by weight or less, preferably 60 parts by weight or less, and may be 50 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 25 parts by weight or less, or 15 parts by weight or less.

In some embodiments, the pressure-sensitive adhesive layer may contain, as the photoreactive monomer (B), a compound B2 having two or more functional groups and no ring structure in the molecule. Compound B2 is preferably used in combination with compound B1. This adjusts the crosslinking structure of the pressure-sensitive adhesive layer, and can form a bond that more suitably balances deformation resistance and impact resistance. Compound B2 can be used alone or in combination of two or more types.

The number of functional groups of compound B2 may be, for example, 50 or less, 40 or less, 30 or less, 20 or less, or 15 or less. The number of functional groups of compound B2 used in some embodiments may be, for example, 2 to 10, preferably 3 to 10, 3 to 8, or 4 to 6. For example, in an embodiment in which a compound having 2 functional groups is used as compound B1, it may be advantageous to use compound B2 having 3 or more functional groups (preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more).

The functional group equivalent of compound B2 is not particularly limited, and may be, for example, 5000 g/mol or less, 2000 g/mol or less, or 1000 g/mol or less. In some embodiments, the functional group equivalent of compound B2 may be, for example, 600 g/mol or less, and from the viewpoint of improving the photocurability and hardness of the cured product, may be 400 g/mol or less, 300 g/mol or less, 200 g/mol or less, 150 g/mol or less, or 100 g/mol or less. The functional group equivalent of compound B2 is typically 50 g/mol or more, preferably 60 g/mol or more, 70 g/mol or more, 80 g/mol or more, or 90 g/mol or more.

Examples of compounds that can be used as compound B2 include, but are not limited to, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, trimethylolethane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, EO-modified or PO-modified products of any of the above-mentioned materials, and the like.

In the embodiment using the compound B2, the amount of the compound B2 relative to 100 parts by weight of the polymer (A) contained in the adhesive layer is not particularly limited, and can be, for example, 0.1 parts by weight or more. From the viewpoint of easily obtaining an adhesive layer that balances deformation resistance and impact resistance, in some embodiments, the amount of the compound B2 relative to 100 parts by weight of the polymer (A) may be, for example, 1 part by weight or more, 2 parts by weight or more, 4 parts by weight or more, 6 parts by weight or more, 10 parts by weight or more, or 12 parts by weight or more. In addition, from the viewpoint of suppressing a decrease in adhesion to the adherend due to excessive crosslinking, in some embodiments, the amount of the compound B2 relative to 100 parts by weight of the polymer (A) is, for example, appropriately set to 25 parts by weight or less, preferably set to 17 parts by weight or less, may be 15 parts by weight or less, may be 13 parts by weight or less, or may be 9 parts by weight or less.

In the embodiment in which the compound B1 and the compound B2 are used in combination, the compound B2 may preferably be a compound having a functional group number of 3 or more and a functional group equivalent smaller than that of the compound B1 used in combination therewith. In some embodiments, the ratio (FE ₂ /FE ₁ ) of the functional group equivalent FE ₂ of the compound B2 to the functional group equivalent FE ₁ of the compound B1 may be, for example, 0.9 or less, 0.7 or less, 0.5 or less, or 0.4 or less. According to such an embodiment, the effect of improving the elastic modulus by the photoreactive monomer (B) may be efficiently exhibited. The lower limit of the ratio (FE ₂ /FE ₁ ) is not particularly limited, and may be, for example, 0.01 or more, 0.1 or more, or 0.2 or more.

In an embodiment in which compound B1 and compound B2 are used in combination, the weight ratio (W ₂ /W ₁ ) of the amount W ₂ of compound B2 to the amount W ₁ of compound B1 is not particularly limited. In some embodiments, the weight ratio (W ₂ /W ₁ ) may be, for example, 0.05 to 10, 0.1 to 5, 0.2 to 3, or 0.3 to 2. By setting the weight ratio (W ₂ /W ₁ ) to any of the above ranges, the effect of using compound B1 and compound B2 in combination tends to be favorably exhibited.

In some other embodiments using the photoreactive monomer (B) (typically compound B2), the amount of the photoreactive monomer (B) (typically compound B2) used can be about 3% by weight or less of the monomer components of the polymer (A), preferably about 2% by weight or less, and more preferably about 1% by weight or less (e.g., about 0.5% by weight or less). When using the photoreactive monomer (B) (typically compound B2), the lower limit of the amount used is not particularly limited as long as it is greater than 0% by weight. It is appropriate to use the photoreactive monomer (B) (typically compound B2) in an amount of about 0.001% by weight or more (e.g., about 0.01% by weight or more) of the monomer components.

In some embodiments, the photoreactive monomer (B) may be contained in the adhesive layer in a free form. Such an adhesive layer may be suitably formed using an adhesive composition containing the photoreactive monomer (B) in a free form. Here, "free form" means that the photoreactive monomer (B) is not chemically bonded to other components (e.g., polymer (A)) contained in the adhesive layer or the adhesive composition. An adhesive composition containing the photoreactive monomer (B) in a free form may be advantageous in terms of ease of preparation and suppression of gelation.

In some other embodiments, at least a portion of the photoreactive monomer (B) may be included in the adhesive layer in a form chemically bonded to other components (e.g., polymer (A), a crosslinking agent described below, etc.) included in the adhesive layer or the adhesive composition from the viewpoint of improving the processability of the adhesive sheet. The chemical bond may be, for example, a bond formed by a reaction between a functional group F1 other than an ethylenically unsaturated group contained in the molecule of the photoreactive monomer (B) and a functional group F2 contained in the molecule of the other component and capable of reacting with the functional group F1. The other component may be a crosslinking agent, and the photoreactive monomer (B) may be bonded to the polymer (A) via the crosslinking agent.

(Acrylic oligomer)
The adhesive layer of the adhesive sheet disclosed herein may contain an acrylic oligomer from the viewpoint of improving the cohesive force and improving the adhesion to the surface adjacent to the adhesive layer (for example, the surface of the supporting substrate in the adhesive sheet, the surface of the adherend to which the adhesive sheet is attached, etc.). The adhesive layer containing the acrylic oligomer may be preferably formed using an adhesive composition containing the acrylic oligomer. As the acrylic oligomer, one having a higher Tg than the Tg of the above-mentioned polymer (A) may be preferably used.

The Tg of the acrylic oligomer is not particularly limited, and may be, for example, about 20°C or more and 300°C or less. The Tg may be, for example, about 30°C or more, about 40°C or more, about 60°C or more, about 80°C or more, or about 100°C or more. When the Tg of the acrylic oligomer is high, the effect of improving the cohesive force generally tends to be high. In addition, from the viewpoint of anchoring to the support substrate and impact absorption, the Tg of the acrylic oligomer may be, for example, about 250°C or less, about 200°C or less, about 180°C or less, or about 150°C or less. The Tg of the acrylic oligomer is a value calculated based on the Fox formula, like the Tg of the polymer (A).

The Mw of the acrylic oligomer is not particularly limited, and may be, for example, approximately 1000 or more, suitably approximately 1500 or more, approximately 2000 or more, or approximately 3000 or more. The Mw of the acrylic oligomer may be, for example, less than approximately 30,000, suitably less than approximately 10,000, or approximately less than 7,000, or approximately less than 5,000. When the Mw is within the above range, the effect of improving the cohesiveness of the adhesive layer and the adhesion to the adjacent surface is easily exhibited. The Mw of the acrylic oligomer can be measured by GPC and calculated as a value converted into standard polystyrene. Specifically, for example, it can be measured using a HPLC 8020 manufactured by Tosoh Corporation, two TSKgel GMH-H (20) columns, and a flow rate of approximately 0.5 mL/min in tetrahydrofuran solvent.

Examples of monomer components constituting the acrylic oligomer include (meth)acrylate monomers such as the above-mentioned various C _1-20 alkyl (meth)acrylic esters, the above-mentioned various alicyclic hydrocarbon group-containing (meth)acrylates, the above-mentioned various aromatic hydrocarbon group-containing (meth)acrylates, and (meth)acrylates obtained from alcohols derived from terpene compounds. These can be used alone or in combination of two or more.

From the viewpoint of improving adhesion, it is preferable that the acrylic oligomer contains, as a monomer unit, an acrylic monomer having a relatively bulky structure, such as an alkyl (meth)acrylate having a branched structure in the alkyl group, such as isobutyl (meth)acrylate or t-butyl (meth)acrylate; an alicyclic hydrocarbon group-containing (meth)acrylate; or an aromatic hydrocarbon group-containing (meth)acrylate. In addition, when ultraviolet light is used in synthesizing the acrylic oligomer or in preparing the adhesive layer, a monomer having a saturated hydrocarbon group at the ester end is preferable in that it is less likely to cause polymerization inhibition, and for example, an alkyl (meth)acrylate having a branched structure in the alkyl group or a saturated alicyclic hydrocarbon group-containing (meth)acrylate can be suitably used.

The proportion of the (meth)acrylate monomer in the total monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (e.g., 80% by weight or more, and even 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition substantially consisting of one or more (meth)acrylate monomers. When the monomer components include an alicyclic hydrocarbon group-containing (meth)acrylate and a C _1-20 alkyl (meth)acrylate ester, the weight ratio thereof is not particularly limited. In some embodiments, the weight ratio of the alicyclic hydrocarbon group-containing (meth)acrylate/C _1-20 alkyl (meth)acrylate ester can be, for example, 10/90 or more, 20/80 or more, or 30/70 or more, and can be 90/10 or less, 80/20 or less, or 70/30 or less.

In addition to the above (meth)acrylate monomers, functional group-containing monomers can be used as monomer components constituting the acrylic oligomer, if necessary. Examples of functional group-containing monomers include monomers having nitrogen atom-containing heterocycles such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as AA and MAA; and hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination of two or more. When a functional group-containing monomer is used, the ratio of the functional group-containing monomer to the total monomer components constituting the acrylic oligomer can be, for example, 1% by weight or more, 2% by weight or more, or 3% by weight or more, and can be, for example, 15% by weight or less, 10% by weight or less, or 7% by weight or less. The acrylic oligomer may not use a functional group-containing monomer.

Suitable acrylic oligomers include, for example, homopolymers of dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), as well as copolymers of DCPMA and MMA, copolymers of DCPMA and IBXMA, copolymers of ADA and methyl methacrylate (MMA), copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), and copolymers of CHMA and AA.

Acrylic oligomers can be formed by polymerizing their constituent monomer components. There are no particular limitations on the polymerization method or polymerization mode, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be used in an appropriate mode. The types of polymerization initiators (e.g., azo-based polymerization initiators) that can be used as necessary are generally as exemplified for the synthesis of acrylic polymer (A), and the amount of polymerization initiator and the amount of chain transfer agent (e.g., mercaptans) that are optionally used are appropriately set based on technical common sense so as to obtain the desired molecular weight, so detailed explanations are omitted.

When the adhesive layer or adhesive composition contains an acrylic oligomer, the content can be, for example, 0.01 parts by weight or more relative to 100 parts by weight of polymer (A), and from the viewpoint of obtaining a higher effect, it may be 0.05 parts by weight or more, or 0.1 parts by weight or more, or 0.2 parts by weight or more. From the viewpoint of compatibility with polymer (A), the content of the acrylic oligomer relative to 100 parts by weight of polymer (A) is suitably less than 50 parts by weight, preferably less than 30 parts by weight, more preferably 25 parts by weight or less, and may be, for example, 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less. The adhesive layer or adhesive composition may not contain an acrylic oligomer.

(Crosslinking Agent)
A crosslinking agent may be used in the pressure-sensitive adhesive layer as necessary. In the pressure-sensitive adhesive sheet disclosed herein, the crosslinking agent is typically contained in the pressure-sensitive adhesive layer in the form after crosslinking reaction. By using a crosslinking agent, the cohesive strength of the pressure-sensitive adhesive layer can be appropriately adjusted. In addition, for example, in a pressure-sensitive adhesive sheet containing a photoreactive monomer (B) in the pressure-sensitive adhesive layer, the crosslinking agent and the photoreactive monomer (B) can be used in combination to suitably achieve both the flexibility of the pressure-sensitive adhesive layer before photocuring of the photoreactive monomer and the deformation resistance of the pressure-sensitive adhesive layer after photocuring.

The type of crosslinking agent is not particularly limited, and can be selected from among conventionally known crosslinking agents so that the crosslinking agent exerts an appropriate crosslinking function within the adhesive layer, for example, depending on the composition of the adhesive composition. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These can be used alone or in combination of two or more.

As the isocyanate-based crosslinking agent, a polyfunctional isocyanate compound having two or more functionalities can be used. Examples include aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. Examples of commercially available products include isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate L"), trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate HL"), isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HX"), and trimethylolpropane/xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-110N"), etc.

As the epoxy crosslinking agent, those having two or more epoxy groups in one molecule can be used without any particular restrictions. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available epoxy crosslinking agents include Mitsubishi Gas Chemical Company's product names "TETRAD-X" and "TETRAD-C," DIC Corporation's product name "Epicron CR-5L," Nagase ChemteX Corporation's product name "Denacol EX-512," Nissan Chemical Industries' product name "TEPIC-G," and the like.

As the oxazoline-based crosslinking agent, any agent having one or more oxazoline groups in one molecule can be used without any particular limitation.
Examples of the aziridine crosslinking agent include trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)], and the like.
As the carbodiimide-based crosslinking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used.

In some embodiments, peroxides may be used as crosslinking agents. Examples of peroxides include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxyisobutyrate, and dibenzoyl peroxide. Among these, examples of peroxides that are particularly excellent in crosslinking reaction efficiency include di(4-t-butylcyclohexyl)peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide. When peroxides are used as the polymerization initiator, it is also possible to use the remaining peroxide that is not used in the polymerization reaction in the crosslinking reaction. In this case, the remaining amount of peroxide should be quantified, and if the ratio of peroxide is less than the specified amount, peroxide should be added as necessary to reach the specified amount. The amount of peroxide can be quantified by the method described in Japanese Patent No. 4971517.

When a crosslinking agent is used, the amount used (the total amount when two or more crosslinking agents are used) is not particularly limited. From the viewpoint of realizing an adhesive that exhibits adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, the amount of crosslinking agent used is suitably about 5 parts by weight or less per 100 parts by weight of polymer (A), and may be 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or less than 1 part by weight. In an embodiment in which a crosslinking agent and a photoreactive monomer (B) are used in combination, from the viewpoint of making it easier to favorably exhibit the effects of such combined use, the amount of crosslinking agent used per 100 parts by weight of polymer (A) may be, for example, 0.80 parts by weight or less, 0.60 parts by weight or less, 0.30 parts by weight or less, or 0.10 parts by weight or less. The lower limit of the amount of crosslinking agent used is not particularly limited, and it may be used in an amount greater than 0 parts by weight per 100 parts by weight of polymer (A). In some embodiments, the amount of the crosslinking agent used can be, for example, 0.001 parts by weight or more, or may be 0.01 parts by weight or more, or may be 0.03 parts by weight or more, relative to 100 parts by weight of the polymer (A).

The technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as a crosslinking agent. The isocyanate-based crosslinking agent may be used in combination with other crosslinking agents. In an embodiment using an isocyanate-based crosslinking agent, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of polymer (A) may be, for example, 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.03 parts by weight or more. In addition, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of polymer (A) may be, for example, 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, less than 2 parts by weight, less than 1 part by weight, less than 0.80 parts by weight, less than 0.60 parts by weight, less than 0.30 parts by weight, less than 0.10 parts by weight, or less than 0.08 parts by weight.

A crosslinking catalyst may be used to promote the crosslinking reaction more effectively. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, nursem ferric, butyltin oxide, and dioctyltin dilaurate. Among these, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used can be, for example, about 0.0001 parts by weight or more, about 0.001 parts by weight or more, about 0.005 parts by weight or more, or about 1 part by weight or less, about 0.1 parts by weight or less, about 0.05 parts by weight or less, relative to 100 parts by weight of polymer (A).

The adhesive composition used to form the adhesive layer may contain a compound that generates keto-enol tautomerism as a crosslinking retarder, if desired. For example, a compound that generates keto-enol tautomerism may be preferably used in an adhesive composition that contains an isocyanate-based crosslinking agent or an adhesive composition that can be used by blending an isocyanate-based crosslinking agent. This can provide an effect of extending the pot life of the adhesive composition.
As the compound that causes keto-enol tautomerization, various β-dicarbonyl compounds can be used. Specific examples include β-diketones such as acetylacetone and 2,4-hexanedione; acetoacetates such as methyl acetoacetate and ethyl acetoacetate; propionylacetates such as ethyl propionylacetate; isobutyrylacetates such as ethyl isobutyrylacetate; malonic acid esters such as methyl malonate and ethyl malonate; and the like. Among these, preferred compounds include acetylacetone and acetoacetates. The compounds that cause keto-enol tautomerization can be used alone or in combination of two or more.
The amount of the compound capable of causing keto-enol tautomerization used may be, for example, 0.1 parts by weight or more and 20 parts by weight or less, and appropriately 0.5 parts by weight or more and 15 parts by weight or less, for example, 1 part by weight or more and 10 parts by weight or less, or may be 1 part by weight or more and 5 parts by weight or less, relative to 100 parts by weight of polymer (A).

(Silane coupling agent)
The adhesive layer of the adhesive sheet disclosed herein may contain a silane coupling agent if desired. The use of a silane coupling agent can improve the peel strength of the adhesive sheet from an adherend (e.g., a glass plate). The adhesive layer containing a silane coupling agent can be suitably formed using an adhesive composition containing a silane coupling agent. In such an adhesive composition, the silane coupling agent is preferably contained in the adhesive composition in a free form from the viewpoint of gelation inhibition and the like. In some embodiments, the silane coupling agent is preferably contained in the adhesive layer of the adhesive sheet disclosed herein in a free form. The silane coupling agent contained in the adhesive layer in such a form can effectively contribute to improving the peel strength. Here, the "free form" refers to the silane coupling agent not being chemically bonded to other components contained in the adhesive composition or the adhesive layer.

Examples of silane coupling agents include silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane. In some embodiments, the above-mentioned effects can be more preferably achieved by employing a silane coupling agent having a trialkoxysilyl group. Among these, preferred silane coupling agents include 3-glycidoxypropyltrimethoxysilane and acetoacetyl group-containing trimethoxysilane.

When using a silane coupling agent, the amount used can be set so as to obtain the desired effect, and is not particularly limited. In some embodiments, the amount of the silane coupling agent used may be, for example, 0.001 parts by weight or more relative to 100 parts by weight of polymer (A), and from the viewpoint of obtaining a higher effect, it may be 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more. In addition, from the viewpoint of suppressing gelation of the adhesive composition, the amount of the silane coupling agent used relative to 100 parts by weight of polymer (A) is suitably 3 parts by weight or less, may be 1 part by weight or less, or may be 0.5 parts by weight or less.

(Photopolymerization initiator)
The adhesive layer of the adhesive sheet disclosed herein may contain a photopolymerization initiator as necessary for the purpose of improving or imparting photocurability. As the photopolymerization initiator, like the photopolymerization initiators exemplified as those usable in the synthesis of the polymer (A), a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, etc. may be used. The photopolymerization initiator may be used alone or in appropriate combination of two or more.

Specific examples of ketal-based photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one and the like.
Specific examples of acetophenone-based photopolymerization initiators include 1-hydroxycyclohexyl-phenyl-ketone, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, and the like.
Specific examples of the benzoin ether-based photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acylphosphine oxide photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like.
Specific examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, etc. Specific examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride, etc. Specific examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, etc. Specific examples of benzoin-based photopolymerization initiators include benzoin, etc. Specific examples of benzyl-based photopolymerization initiators include benzyl, etc.
Specific examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like.
Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

The content of the photopolymerization initiator in the adhesive layer is not particularly limited and can be set so that the desired effect is appropriately exhibited. In some embodiments, the content of the photopolymerization initiator can be, for example, approximately 0.005 parts by weight or more, suitably 0.01 parts by weight or more, preferably 0.05 parts by weight or more, may be 0.10 parts by weight or more, may be 0.15 parts by weight or more, or may be 0.20 parts by weight or more, relative to 100 parts by weight of the polymer (A) contained in the adhesive layer. The photocuring property of the adhesive layer tends to improve by increasing the content of the photopolymerization initiator. In addition, the content of the photopolymerization initiator relative to 100 parts by weight of the polymer (A) is suitably 10 parts by weight or less, preferably 7 parts by weight or less, may be 5 parts by weight or less, 3 parts by weight or less, may be 2 parts by weight or less, or may be 1 part by weight or less. Not having too much photopolymerization initiator can be advantageous in terms of improving the storage stability (e.g., stability against photodegradation) of the adhesive sheet.

The adhesive layer containing a photopolymerization initiator can typically be formed using an adhesive composition (e.g., a solvent-based adhesive composition) containing the photopolymerization initiator. The adhesive composition containing a photopolymerization initiator can be prepared, for example, by mixing the photopolymerization initiator with other components used in the composition. In addition, when preparing an adhesive composition using a polymer (A) (e.g., an acrylic polymer (A)) synthesized (photopolymerized) in the presence of a photopolymerization initiator, the residue (unreacted material) of the photopolymerization initiator used in synthesizing the polymer (A) may be used as part or all of the photopolymerization initiator contained in the adhesive layer. The same applies when an acrylic oligomer synthesized in the presence of a photopolymerization initiator is used as the acrylic oligomer used as needed. From the viewpoint of ease of manufacturing management, the adhesive layer disclosed herein can be preferably formed using an adhesive composition prepared by newly adding the above-mentioned amount of photopolymerization initiator to other components.

The adhesive layer or adhesive composition of the adhesive sheet disclosed herein may contain, as necessary, various additives common in the field of adhesives, such as tackifier resins (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based, etc. tackifier resins), viscosity adjusters (e.g., thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antiaging agents, etc., as other optional components. As for such various additives, those conventionally known can be used in the usual manner, and they do not particularly characterize the present invention, so detailed explanations will be omitted.
The technology disclosed herein can exhibit good adhesive strength without using the above-mentioned tackifier resin. Therefore, in some embodiments, the content of the tackifier resin in the pressure-sensitive adhesive layer or pressure-sensitive adhesive composition can be, for example, less than 10 parts by weight, or even less than 5 parts by weight, relative to 100 parts by weight of the polymer (A). The content of the tackifier resin can be less than 1 part by weight (for example, less than 0.5 parts by weight), or less than 0.1 parts by weight (0 parts by weight or more and less than 0.1 parts by weight). The pressure-sensitive adhesive layer or pressure-sensitive adhesive composition can be one that does not contain a tackifier resin.

From the viewpoint of transparency, it is preferable that the amount of components other than the polymer (A) and the photoreactive monomer (B) used as necessary in the adhesive layer (and thus the adhesive composition used to form the adhesive layer) is limited. In the technology disclosed herein, the amount of components other than the polymer (A) and the photoreactive monomer (B) in the adhesive layer is approximately 30% by weight or less, suitably approximately 15% by weight or less, and preferably approximately 12% by weight or less (e.g. approximately 10% by weight or less). In the adhesive sheet according to some embodiments, the amount of components other than the polymer (A) and the photoreactive monomer (B) in the adhesive layer may be approximately 5% by weight or less, approximately 3% by weight or less, or approximately 1.5% by weight or less (e.g. approximately 1% by weight or less).

<Form of Pressure-Sensitive Adhesive Composition>
The adhesive layer can be formed using an adhesive composition containing the monomer components of the above-mentioned composition in the form of a polymer, an unpolymerized product (i.e., a form in which the polymerizable functional group is unreacted), or a mixture thereof. The adhesive composition can be in various forms, such as a composition containing an adhesive (adhesive component) in an organic solvent (solvent-based adhesive composition), a composition in the form in which an adhesive is dispersed in an aqueous solvent (water-dispersed adhesive composition), a composition prepared to form an adhesive by curing with active energy rays such as ultraviolet rays or radiation (active energy ray-curable adhesive composition), and a hot melt adhesive composition that is applied in a heated and molten state and forms an adhesive when cooled to around room temperature. From the viewpoint of ease of preparation of the adhesive composition and ease of formation of the adhesive layer, a solvent-based adhesive composition can be preferably adopted in some embodiments. The solvent-based adhesive composition can be preferably prepared using a polymer (A) that is a polymer obtained by solution polymerization of a monomer component.

In this specification, "active energy rays" refers to energy rays that have the energy to cause chemical reactions such as polymerization reactions, crosslinking reactions, and decomposition of initiators. Examples of active energy rays include light such as ultraviolet rays, visible light, and infrared rays, and radiation such as alpha rays, beta rays, gamma rays, electron beams, neutron beams, and X-rays.

The pressure-sensitive adhesive composition typically contains at least a portion of the monomer components of the composition (which may be a portion of the type of monomer or a portion of the amount) in the form of a polymer. The polymerization method for forming the polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically carried out in the presence of a thermal polymerization initiator); photopolymerization carried out by irradiating light such as ultraviolet light (typically carried out in the presence of a photopolymerization initiator); radiation polymerization carried out by irradiating radiation such as β rays and γ rays; and the like can be appropriately adopted. In these polymerization methods, the mode of polymerization is not particularly limited, and the polymerization can be carried out by appropriately selecting a conventionally known monomer supply method, polymerization conditions (temperature, time, pressure, light irradiation amount, radiation irradiation amount, etc.), and materials used other than the monomer (polymerization initiator, surfactant, etc.), etc.

In the polymerization, a known or commonly used photopolymerization initiator or thermal polymerization initiator may be used depending on the polymerization method, polymerization mode, etc. Examples of photopolymerization initiators and thermal polymerization initiators are as described above, so duplicated explanations will be omitted. Such polymerization initiators can be used alone or in appropriate combination of two or more types.

(Adhesive composition containing polymerized and unpolymerized monomer components)
The pressure-sensitive adhesive composition according to some embodiments includes a polymerization product of a monomer mixture containing at least a part of the monomer components (raw material monomers) of the composition. Typically, the composition includes a part of the monomer components in the form of a polymer, and the remaining part in the form of an unpolymerized product (unreacted monomer). The polymerization product of the monomer mixture can be prepared by at least partially polymerizing the monomer mixture.
The polymerization reaction product is preferably a partial polymer of the monomer mixture. Such a partial polymer is a mixture of a polymer derived from the monomer mixture and an unreacted monomer, and typically has a syrup-like appearance (viscous liquid). Hereinafter, a partial polymer having such properties may be referred to as "monomer syrup", "polymer syrup", or simply as "syrup".

The polymerization method for obtaining the above-mentioned polymerization reaction product is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. From the viewpoints of efficiency and simplicity, a photopolymerization method can be preferably used. With photopolymerization, the polymerization conversion rate of the above-mentioned monomer mixture can be easily controlled by the polymerization conditions such as the amount of light irradiation (light amount).

The polymerization conversion rate (monomer conversion) of the monomer mixture in the partial polymer is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, and is preferably about 60% by weight or less. From the viewpoint of ease of preparation and coatability of the adhesive composition containing the partial polymer, the polymerization conversion rate is suitably about 50% by weight or less, and is preferably about 40% by weight or less (for example, about 35% by weight or less). The lower limit of the polymerization conversion rate is not particularly limited, but is typically about 1% by weight or more, and is suitably about 5% by weight or more.

The adhesive composition containing the partial polymer of the monomer mixture can be easily obtained, for example, by partially polymerizing the monomer mixture containing all of the raw material monomers by an appropriate polymerization method (for example, photopolymerization method). The adhesive composition containing the partial polymer may contain other components (for example, a photopolymerization initiator, a polyfunctional monomer, a crosslinking agent, an acrylic oligomer described below, etc.) that are used as needed. The method of adding such other components is not particularly limited, and for example, they may be included in the monomer mixture in advance, or they may be added to the partial polymer.

The adhesive composition disclosed herein may also be in a form in which a complete polymer of a monomer mixture containing some types of monomers among the monomer components (raw monomers) is dissolved in the remaining types of monomers or their partial polymers. Adhesive compositions in such a form are also included in examples of adhesive compositions containing polymerized and unpolymerized monomer components. In this specification, the term "completely polymerized" refers to a polymerization conversion rate of more than 95% by weight.

As such, a photopolymerization method can be preferably adopted as a curing method (polymerization method) when forming an adhesive from an adhesive composition containing a polymerized product and an unpolymerized product of a monomer component. In an adhesive composition containing a polymerization reactant prepared by a photopolymerization method, it is particularly preferable to adopt a photopolymerization method as a curing method. Since the polymerization reactant obtained by the photopolymerization method already contains a photopolymerization initiator, when the adhesive composition containing this polymerization reactant is further cured to form an adhesive, it can be photocured without adding a new photopolymerization initiator. Alternatively, the adhesive composition may be a composition in which a photopolymerization initiator is added as necessary to the polymerization reactant prepared by the photopolymerization method. The added photopolymerization initiator may be the same as or different from the photopolymerization initiator used in preparing the polymerization reactant. An adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. A photocurable adhesive composition has the advantage that even a thick adhesive layer can be easily formed. In some preferred embodiments, photopolymerization when forming an adhesive from the adhesive composition can be performed by ultraviolet irradiation. For ultraviolet irradiation, known high pressure mercury lamps, low pressure mercury lamps, metal halide lamps, etc. can be used.

(Adhesive composition containing monomer component in the form of a completely polymerized product)
A PSA composition according to some other embodiments contains a monomer component of the PSA composition in the form of a complete polymer. Such a PSA composition may be in the form of, for example, a solvent-based PSA composition containing an acrylic polymer, which is a complete polymer of the monomer component, in an organic solvent, or an aqueous dispersion-based PSA composition in which the acrylic polymer is dispersed in an aqueous solvent.

(Thickness of adhesive layer)
The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer may be, for example, about 1 μm to 500 μm, for example, about 3 μm to 500 μm. In some embodiments, the thickness of the adhesive layer is suitably 5 μm or more, for example, 10 μm or more, preferably 20 μm or more, more preferably 25 μm or more, and may be more than 25 μm. When the thickness of the adhesive layer is large, the stress dispersion ability of the adhesive layer tends to be high. This can advantageously contribute to reducing optical distortion. In addition, a thick adhesive layer tends to have excellent step followability and is easy to absorb deformation due to foreign matter, etc. Impact resistance also tends to be improved. The technology disclosed herein can be preferably implemented in an embodiment in which the thickness of the adhesive layer is, for example, 30 μm or more. The thickness of the adhesive layer may be 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 75 μm or more, or 90 μm or more. On the other hand, when the thickness of the adhesive layer is increased, the optical path passing through the adhesive layer is also increased, so that optical distortion is easily recognized. For this reason, in some embodiments, the thickness of the adhesive layer is suitably set to, for example, 200 μm or less, and may be 150 μm or less, 120 μm or less, preferably 100 μm or less, more preferably 70 μm or less, even more preferably 50 μm or less, and may be 35 μm or less. An adhesive layer having such a thickness can be one in which deformation of the adhesive layer is better suppressed. According to the technology disclosed herein, a bond having high deformation resistance and high impact resistance can be formed in a configuration including an adhesive layer having a thickness of, for example, 70 μm or less.

The thickness of the adhesive layer can be measured with a 1/1000 mm scale dial gauge with a flat probe. For example, in the case of a structure of release film/adhesive layer/release film, the total thickness can be measured with a 1/1000 mm scale dial gauge with a flat probe, and the thickness of the release film can be subtracted to calculate the thickness.

(Tan δ peak top temperature)
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer disclosed herein preferably has a peak top temperature of its loss tangent tan δ in the range of -50°C to 0°C. A pressure-sensitive adhesive having a peak top of tan δ in the low temperature region is likely to provide good impact resistance. The peak top temperature of the loss tangent tan δ of the pressure-sensitive adhesive can be determined by the following method. That is, dynamic viscoelasticity measurement is carried out under the same conditions as the measurement of the 25°C storage modulus described below, and the storage modulus G' and loss modulus G" are measured. Next, the loss tangent tan δ is calculated by the following formula: tan δ = G"/G'; and the temperature dependency is plotted, whereby the temperature corresponding to the peak top (the temperature at which the tan δ curve is maximum) can be determined.

(25°C storage modulus)
The storage modulus at 25°C (25°C storage modulus) of the adhesive layer is appropriately set according to the purpose of use and the mode of use, and is not limited to a specific range. From the viewpoint of adhesive properties such as deformation resistance and heat resistance, the 25°C storage modulus is suitable to be about 4 x ¹⁰⁴ Pa or more, preferably about 6 x ¹⁰⁴ Pa or more, more preferably about 8 x ¹⁰⁴ Pa or more, may be about 1.0 x ¹⁰⁵ Pa or more, may be about 1.2 x ¹⁰⁵ Pa or more, may be about 1.5 x ¹⁰⁵ Pa or more, or may be about 1.8 x ¹⁰⁵ Pa or more. The adhesive layer having a high 25°C storage modulus tends to have excellent resistance to deformation under pressure. In addition, the 25°C storage modulus is, for example, less than 1 x ¹⁰⁷ Pa, and is suitable to be about 1 x ¹⁰⁶ Pa or less. From the viewpoint of suitably expressing adhesive properties such as adhesion, the 25°C storage modulus is preferably about 5.0 x ¹⁰⁵ Pa or less, more preferably about 3.0 x ¹⁰⁵ Pa or less, even more preferably about 2.0 x ¹⁰⁵ Pa or less, and may be about 1.4 x ¹⁰⁵ Pa or less, or may be about 1.0 x ¹⁰⁵ Pa or less. The storage modulus at 25°C of the adhesive sheet (typically a substrate-less adhesive sheet) is also preferably within the range exemplified above. The 25°C storage modulus can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc. of the base polymer. The 25°C storage modulus is measured by the following method. The same applies to the examples described below.

[Storage modulus at 25°C]
A pressure-sensitive adhesive layer having a thickness of about 2 mm is prepared by stacking a plurality of pressure-sensitive adhesive sheets or layers to be measured. A sample is punched out from the pressure-sensitive adhesive layer into a disk shape having a diameter of 7.9 mm, which is sandwiched and fixed between parallel plates. Dynamic viscoelasticity is measured under the following conditions using a viscoelasticity tester (e.g., ARES manufactured by TA Instruments or its equivalent) to determine the storage modulus G' (25°C) [Pa] at 25°C.
・Measurement mode: Shear mode ・Temperature range: -70℃ to 150℃
Heating rate: 5°C/min
・Measurement frequency: 1Hz

(Gel Fraction)
The gel fraction of the adhesive layer is appropriately set according to the purpose of use, the mode of use, etc., and is not limited to a specific range. The gel fraction is, for example, about 99% by weight or less, and is suitably about 97% by weight or less. From the viewpoint of step-following ability, in some preferred embodiments, the gel fraction is about 95% by weight or less, more preferably about 92% by weight or less, and may be about 88% by weight or less, may be about 75% by weight or less, or may be about 65% by weight or less. For example, when a logo mark or other print is formed on the surface of the adherend, the adhesive layer having the gel fraction can follow the unevenness of the print well without impairing visibility. In addition, from the viewpoint of good adhesive properties and viscoelastic properties, the gel fraction of the adhesive layer is, for example, about 10% by weight or more, and is suitably about 20% by weight or more. From the viewpoint of deformation resistance, the gel fraction is preferably about 30% by weight or more, more preferably about 40% by weight, and may be about 50% by weight or more, about 65% by weight or more, or about 75% by weight or more. The gel fraction of the adhesive sheet (typically a substrate-less adhesive sheet) is also preferably within the range exemplified above. The gel fraction can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc. of the base polymer. The gel fraction is measured by the following method. The same applies to the examples described below.

[Gel fraction]
A given amount of adhesive sample (weight _Wg1 ) is wrapped in a porous polytetrafluoroethylene film (weight _Wg2 ) with an average pore size of 0.2 μm in the shape of a purse, and the opening is tied with string (weight _Wg3 ). As the porous polytetrafluoroethylene (PTFE) film, "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Corporation or an equivalent product is used.
The package is immersed in a sufficient amount of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute only the sol component in the adhesive layer outside the film, and then the package is taken out and the ethyl acetate adhering to the outer surface is wiped off, and the package is dried at 130° C. for 2 hours and the weight of the package ( _Wg4 ) is measured. The gel fraction of the adhesive layer is determined by substituting each value into the following formula.
Gel fraction (%)=[( _Wg4 − _Wg2 − _Wg3 )/ _Wg1 ]×100

In addition, the adhesive sheet disclosed herein includes an adhesive sheet in a form in which the adhesive layer is photocured after being attached to an adherend, so at least for a photocurable adhesive sheet (for example, the adhesive sheet of Example 4 having adhesive C described later), ultraviolet light is irradiated under conditions of an illuminance of 300 mW/cm ² and an integrated light amount of 3000 mJ/cm ² , and the measurement sample after aging at 50 ° C for 48 hours is used to measure the peak top temperature of tan δ, the storage modulus at 25 ° C, the gel fraction, the total light transmittance, the haze value, the maximum height Rz of the adhesive surface, the arithmetic mean roughness Ra, the adhesive force, the modulus of elasticity by a tensile test, and the impact resistance. When the release film is transparent, the treatment of irradiating ultraviolet light is preferably performed in a state in which the adhesive sheet (typically the adhesive layer) is sandwiched between the transparent release films.

<Support substrate>
The pressure-sensitive adhesive sheet according to some embodiments may be in the form of a pressure-sensitive adhesive sheet with a support substrate. The material of the support substrate is not particularly limited, and can be appropriately selected according to the purpose and mode of use of the pressure-sensitive adhesive sheet. Non-limiting examples of the support substrate that can be used include resin films such as polyolefin films mainly composed of polyolefins such as polypropylene and ethylene-propylene copolymers, polyester films mainly composed of polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets made of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven fabrics and nonwoven fabrics made by single or mixed spinning of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate); papers such as Japanese paper, fine paper, craft paper, and crepe paper; metal foils such as aluminum foil and copper foil; and the like. The support substrate may be a composite of these. Examples of such a composite structure support substrate include a support substrate having a structure in which a metal layer (e.g., a metal foil, a continuous or discontinuous metal sputter layer, a metal vapor deposition layer, a metal plating layer, etc.) or a metal oxide layer is laminated with the above-mentioned resin film, a resin sheet reinforced with inorganic fibers such as glass cloth, etc. The support substrate may be an optical member (e.g., an optical film) described later, or may be a transparent member formed of a transparent material (e.g., a transparent resin material, glass, etc.).

As the support substrate of the adhesive sheet disclosed herein, various films (hereinafter also referred to as support films) can be preferably used. The support film may be a porous film such as a foam film or a nonwoven fabric sheet, or may be a nonporous film, or may be a film having a structure in which a porous layer and a nonporous layer are laminated. In some embodiments, the support film may preferably be one that includes a resin film that can independently maintain its shape (self-supporting or independent) as a base film. Here, the term "resin film" refers to a resin film that has a nonporous structure and typically does not substantially contain air bubbles (voidless). Therefore, the resin film is a concept that is distinguished from foam films and nonwoven fabrics. The resin film may be a single-layer structure, or may be a multi-layer structure of two or more layers (e.g., a three-layer structure).

Examples of resin materials that can be used to form the resin film include polyester, polyolefin, polycycloolefin derived from a monomer having an aliphatic ring structure such as a norbornene structure, polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide, polyimide (PI), polyamideimide (PAI), polyetheretherketone (PEEK), polyethersulfone (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polystyrene, fluororesins such as polyvinyl chloride, polyvinylidene chloride, and polytetrafluoroethylene (PTFE), acrylic resins such as polymethyl methacrylate, cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose, vinyl butyral-based polymers, arylate-based polymers, polyoxymethylene-based polymers, and epoxy-based polymers. The resin film may be formed using a resin material containing one of these resins alone, or may be formed using a resin material in which two or more of these resins are blended. The resin film may be unstretched or stretched (e.g., uniaxially or biaxially stretched).

Suitable examples of resin materials constituting the resin film include polyester-based resin, PPS resin, and polyolefin-based resin. Here, polyester-based resin refers to a resin that contains more than 50% by weight of polyester. Similarly, PPS resin refers to a resin that contains more than 50% by weight of PPS, and polyolefin-based resin refers to a resin that contains more than 50% by weight of polyolefin.

As the polyester-based resin, typically, a polyester-based resin containing, as the main component, a polyester obtained by polycondensation of a dicarboxylic acid and a diol is used. Specific examples of polyester-based resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate, etc.

As the polyolefin resin, one type of polyolefin can be used alone, or two or more types of polyolefins can be used in combination. The polyolefin can be, for example, a homopolymer of an α-olefin, a copolymer of two or more types of α-olefins, or a copolymer of one or more types of α-olefins with other vinyl monomers. Specific examples include polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers such as ethylene propylene rubber (EPR), ethylene-propylene-butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, and ethylene-ethyl acrylate copolymers. Both low density (LD) polyolefins and high density (HD) polyolefins can be used. Examples of polyolefin resin films include non-oriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, medium density polyethylene (MDPE) film, high density polyethylene (HDPE) film, polyethylene (PE) film made by blending two or more types of polyethylene (PE), and PP/PE blend film made by blending polypropylene (PP) and polyethylene (PE).

Specific examples of resin films that can be preferably used as the support substrate include PET film, PEN film, PPS film, PEEK film, CPP film, and OPP film. Preferred examples from the standpoint of strength include PET film, PEN film, PPS film, and PEEK film. Preferred examples from the standpoint of availability, dimensional stability, optical properties, etc. include PET film.

The resin film can contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, as necessary. The amount of additives is not particularly limited and can be set appropriately depending on the application of the pressure-sensitive adhesive sheet, etc.

The method for producing the resin film is not particularly limited. For example, conventional resin film molding methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately used.

The support substrate may be a support film substantially composed of such a resin film. The support substrate may also be a support film including an auxiliary layer in addition to the resin film. The upper auxiliary layer may be disposed on the adhesive layer side of the resin film, on the opposite side to the adhesive layer, or on both sides of the resin film. Examples of the auxiliary layer include an optical property adjusting layer (e.g., a colored layer, an anti-reflection layer), a decorative layer that imparts a desired appearance to the support substrate or adhesive sheet (e.g., a printed layer, a laminate layer, a continuous or discontinuous metal layer, a continuous or discontinuous metal oxide layer, etc.), a conductive layer, an antistatic layer, an undercoat layer, a release layer, etc.

In some embodiments, the support substrate is preferably a transparent plastic film. In this embodiment, the total light transmittance of the support substrate is, for example, about 50% or more, and is preferably, for example, about 70% or more. From the viewpoint of visibility of the adherend through the pressure-sensitive adhesive sheet, in some preferred embodiments, the total light transmittance of the support substrate is about 85% or more, more preferably about 90% or more. The upper limit of the total light transmittance may be, in practical terms, about 95% or less, or about 94% or less (for example, 93% or less).
The total light transmittance of the supporting substrate can be measured using a haze meter, such as "HM-150N" manufactured by Murakami Color Research Laboratory or an equivalent product.

The thickness of the support substrate is not particularly limited and may be selected according to the purpose and mode of use of the adhesive sheet. The thickness of the support substrate may be, for example, 1000 μm or less. From the viewpoint of handleability (e.g., ease of rolling), etc., it is appropriate to be 500 μm or less, and preferably 300 μm or less, and may be 100 μm or less, 70 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. When the thickness of the support substrate is reduced, the flexibility of the adhesive sheet and its ability to follow the surface shape of the adherend tend to improve. In addition, from the viewpoint of handleability, processability, etc., the thickness of the support substrate may be, for example, 2 μm or more, or may be more than 5 μm or more than 10 μm. In some embodiments, the thickness of the support substrate may be, for example, 20 μm or more, 35 μm or more, or 55 μm or more.

The surface of the support substrate that is to be bonded to the adhesive layer may be subjected to a conventionally known surface treatment, such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of an undercoat (primer), or antistatic treatment, as necessary. Such surface treatments may be treatments for improving the adhesion between the support substrate and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the support substrate. The composition of the primer is not particularly limited, and may be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, but is appropriately about 0.01 μm to 1 μm, and preferably about 0.1 μm to 1 μm.

<Method of manufacturing adhesive sheet with release film>
The method for producing the adhesive sheet with a release film disclosed herein is not particularly limited. For example, an adhesive composition is applied to the release surface of a release film, and dried (e.g., dried by heating) or cured to form an adhesive layer on the release surface, and a different release film is laminated on the surface opposite to the release surface of the adhesive layer to obtain an adhesive sheet with a release film. Alternatively, an adhesive sheet with a release film may be formed by drying or curing an adhesive composition sandwiched between two release films to form an adhesive layer. For an adhesive sheet having a support substrate, for example, a method (direct method) can be adopted in which an adhesive composition is applied to the support substrate and dried or cured to form an adhesive layer. In addition, a method (transfer method) can be adopted in which an adhesive composition is applied to a surface (release surface) having releasability, and dried to form an adhesive layer on the surface, and the adhesive layer is transferred to a support substrate.

The curing process may include crosslinking (for example, crosslinking by the reaction of the crosslinking agent described above), cooling, etc. When two or more types of curing processes are performed, they can be performed simultaneously or stepwise. Various conventionally known methods can be used as a method for applying the adhesive composition. Specific examples include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater, etc.

The adhesive sheet with release film disclosed herein can be suitably manufactured by a method including drying or curing a liquid film of an adhesive composition on the release surface of a release film to form an adhesive layer. According to this method, the adhesive composition (liquid film) in a fluid state is dried or cured in contact with the release surface, so that the smoothness of the adhesive layer surface formed in contact with the release surface can be precisely controlled. The release surface is typically limited in maximum height (Rz) to a predetermined value or less, and by using a release film having such a release surface, a highly smooth adhesive surface can be stably (reproducibly) manufactured.

The adhesive sheet with release film disclosed herein can be preferably manufactured by a method including curing the liquid film of the adhesive composition between the release surfaces of the first release film and the second release film to form an adhesive layer. As a method for disposing the liquid film of the adhesive composition between the release surfaces of the first release film and the second release film, a method can be adopted in which the liquid adhesive composition is applied to the release surface of one release film, and then the liquid film of the adhesive composition is covered with the other release film. As another method, a method can be mentioned in which the first release film and the second release film are supplied between a pair of rolls with their release surfaces facing each other, and the liquid adhesive composition is supplied between the release surfaces. The adhesive composition is preferably applied at 80°C or less, and more preferably at 60°C or less (for example, 40°C or less). This suppresses roughness of the adhesive layer due to the difference in thermal expansion coefficient between the first release film, the second release film, and the adhesive layer, and a more smooth adhesive surface can be formed.

The total thickness of the adhesive sheet with release film disclosed herein is not particularly limited and may be, for example, about 30 μm to 1500 μm. Here, the total thickness of the adhesive sheet with release film refers to the total thickness of the adhesive sheet with release film consisting of at least one release film (including a first release film and a second release film) and an adhesive sheet. In some embodiments, the total thickness of the adhesive sheet with release film may be, for example, 60 μm or more, 80 μm or more, 105 μm or more, 125 μm or more, or 140 μm or more. The total thickness of the adhesive sheet with release film may be, for example, 1000 μm or less, 500 μm or less, or 300 μm or less.

<Roll body>
According to this specification, a roll body (adhesive sheet roll with release film) is provided that includes the adhesive sheet with release film disclosed herein in a wound form. Such a roll body typically includes a core (winding core) and an adhesive sheet with release film wound around the core. The shape of the core is not particularly limited, and may be, for example, a solid columnar shape, a hollow columnar shape (i.e., a cylindrical shape), a hollow or solid polygonal columnar shape, etc. From the viewpoint of improving the handleability of the roll body, a hollow columnar or hollow polygonal columnar core may be preferably adopted. A cylindrical core is particularly preferred.

<Attachment to Adherend>
The method of attaching the adhesive sheet disclosed herein to an adherend is not particularly limited. Any known or conventional pressure-bonding method can be adopted according to the purpose and mode of use. In some preferred modes, the adhesive sheet can be used in a mode in which the adhesive sheet is attached to the adherend by a method including photocuring the adhesive layer after the sheet is attached to the adherend. By attaching the adhesive sheet to the adherend, an adherend on which the adhesive sheet is laminated is formed. By photocuring the adhesive layer of the adhesive sheet, a laminate including the adhesive sheet with the cured adhesive layer and the adherend is obtained. Thus, this specification provides a method of attaching an adhesive sheet, which includes, in this order, attaching any one of the adhesive sheets disclosed herein to an adherend and irradiating the adhesive sheet with ultraviolet light to photocuring the adhesive layer.

<Applications>
The pressure-sensitive adhesive sheet disclosed herein can be used for fixing, joining, forming, decorating, protecting, supporting, and the like of components constituting various products. The material constituting at least the surface of the above-mentioned component can be, for example, glass such as alkali glass or non-alkali glass; metal materials such as stainless steel (SUS) and aluminum; resin materials such as acrylic resin, ABS resin, polycarbonate resin, polyimide resin, polyester resin such as PET, polystyrene resin, and the like. The above-mentioned component can be, for example, a component constituting various mobile devices (portable devices), automobiles, home appliances, and the like. In addition, the surface of the above-mentioned component to which the pressure-sensitive adhesive sheet is attached can be a painted surface with a paint such as an acrylic-based, polyester-based, alkyd-based, melamine-based, urethane-based, acid-epoxy crosslinked, or a composite of these (for example, an acrylic-melamine-based, alkyd-melamine-based) paint, or a plated surface such as a zinc-plated steel sheet. In addition, the above-mentioned component can be, for example, a resin film, or a resin film having a continuous or discontinuous inorganic layer (which can be a metal layer, a metal oxide layer, or the like).

An example of a preferred application is an optical application. More specifically, the adhesive sheet disclosed herein can be preferably used as an optical adhesive sheet used, for example, for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical members.

The optical member is a member having optical properties (e.g., polarizing, light refraction, light diffraction, optical rotation, etc.). The optical member is not particularly limited as long as it has optical properties, but examples thereof include components constituting devices (optical devices) such as display devices (image display devices) and input devices, or components used in these devices, such as polarizing plates, wave plates, retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, hard coat (HC) films, impact absorbing films, antifouling films, photochromic films, light control films, transparent conductive films (ITO films), and further components in which these are laminated (these may be collectively referred to as "functional films"). The above "plate" and "film" are intended to include plate-like, film-like, sheet-like, and other forms, and for example, "polarizing film" is intended to include "polarizing plate" and "polarizing sheet", etc.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), and electronic paper. Examples of the input device include a touch panel.

The optical member is not particularly limited, but examples include members made of glass, acrylic resin, polycarbonate, transparent polyimide, PET, etc. (e.g., sheet-shaped, film-shaped, or plate-shaped members).

The mode of bonding optical members using the adhesive sheet disclosed herein is not particularly limited, but may be, for example, (1) a mode in which optical members are bonded to each other via the adhesive sheet disclosed herein, (2) a mode in which an optical member is bonded to a member other than an optical member via the adhesive sheet disclosed herein, or (3) a mode in which the adhesive sheet disclosed herein includes an optical member and the adhesive sheet is bonded to an optical member or a member other than an optical member. In the above mode (3), the adhesive sheet having an optical member may be, for example, an adhesive sheet whose supporting substrate is an optical member (e.g., an optical film). In this way, an adhesive sheet having an optical member as a supporting substrate may also be understood as an adhesive-type optical member (e.g., an adhesive-type optical film). In addition, when the adhesive sheet disclosed herein is an adhesive sheet having a supporting substrate and the functional film is used as the supporting substrate, the adhesive sheet disclosed herein may also be understood as an "adhesive-type functional film" having an adhesive layer disclosed herein on at least one side of the functional film.

The adhesive sheet disclosed herein can be preferably used for applications in which it is attached to a decorative film. Here, the decorative film refers to a film having a design (including color, tone, pattern, and even text information such as a logo mark, etc.) on its surface (decorated surface), and is also called a design film or a decorative film. The decorative film includes a member that plays a role in decoration and protection while maintaining the visibility of an image display device or an input device. Examples of decorative films include films having a decorative layer (printed layer, laminate layer, colored layer, glossy layer, continuous or discontinuous inorganic layer (metal layer, metal oxide layer, etc.) that imparts a desired appearance. The decorative film can have a design on its surface while exhibiting good concealment properties.

The decorative film may have a decorative layer. Examples of the decorative layer include a printing layer, a laminate layer, a colored layer, a glossy layer, a continuous or discontinuous inorganic layer, etc. that impart a desired appearance. Examples of the continuous or discontinuous inorganic layer include a continuous or discontinuous metal layer, a continuous or discontinuous metal oxide layer, a laminate of a continuous or discontinuous metal layer and a metal oxide layer, a continuous or discontinuous metal/metal oxide composite layer, etc. Examples of the metal include aluminum, zinc, lead, copper, silver, and alloys thereof. Examples of the metal oxide include chromium oxide, indium oxide, zinc oxide, titanium oxide, etc. The metal layer or metal oxide layer can be formed by deposition, sputtering, etc. A typical example of a decorative film is a metallic film. A metallic decorative film may have electromagnetic wave transparency in addition to metallic luster. Examples of such decorative films include electromagnetic wave-transmitting metallic glossy members such as those described in JP 2018-69462 A, JP 2019-123238 A, and JP 2019-188805 A.

More specifically, the decorative film may further have a substrate layer and a decorative layer covering at least a portion of at least one surface of the substrate layer. As the substrate layer, various resin films such as the plastic films described above may be used. Among them, resin films formed from polyester resins such as PET, polyolefin resins, polycarbonate resins, and (meth)acrylic resins are preferred. The thickness of the substrate layer is not particularly limited, and is, for example, about 5 to 250 μm. The decorative layer may be disposed on the adhesive sheet side of the substrate layer, on the side opposite to the adhesive sheet side, or on both sides of the substrate layer.

In the decorative film including the decorative layer, the thickness of the decorative layer is preferably within the range of about 1 to 1000 nm, and may be, for example, about 1 to 300 nm, or may be, for example, about 1 to 200 nm. The sheet resistance of the decorative layer is suitably 100 Ω/□ or more, and may be, for example, 250 Ω/□ or more, or may be 1000 Ω/□ or more. The decorative film having such a decorative layer can have radio wave transparency, and can be preferably used for various applications requiring radio wave transparency, such as portable electronic devices. The upper limit of the sheet resistance of the decorative layer is not particularly limited, and may be, for example, 1×10 ¹⁶ Ω/□ or less. The sheet resistance can be measured based on the eddy current measurement method described in JIS Z 2316.

The design-forming surface of the decorative film may be flat or may have irregularities due to printing such as a logo mark or engraving. The adhesive sheet disclosed herein may have excellent step-following properties, and therefore can adhere well to the decorative film surface having the irregularities.

In addition, the adhesive sheet disclosed herein can have excellent visibility of the adherend based on the high surface smoothness, and therefore can be preferably used for applications in which it is attached to a transparent member or for fixing two members, at least one of which is a transparent member. Examples of such member fixing applications include an embodiment in which one member is a transparent member and the other is a member having an image display surface, a decorative surface, or a colored surface. In other words, the adhesive sheet disclosed herein is preferably used for fixing a member having an image display surface, a decorative surface, or a colored surface to a transparent member. Examples of image display surfaces include the above-mentioned liquid crystal display surface, organic EL display surface, PDP, electronic paper, etc. Examples of decorative surfaces include the decorative surface of the above-mentioned decorative film. Examples of colored surfaces include the surface of a light-shielding film or a concealing film. Examples of transparent members that can be used include members formed from transparent materials made of glass, acrylic resin, polycarbonate, PET, or other resin. In such a configuration, for example, by using an adhesive sheet with a total light transmittance or haze value equal to or greater than a predetermined value, the image display surface, decorative surface, or colored surface of the adherend member can be clearly seen through the adhesive sheet and transparent member.

The transparent member may be flat, but the adhesive sheet attachment surface may have unevenness such as printing or engraving, or the transparent member may have a three-dimensional shape as a whole. The adhesive sheet disclosed herein may have excellent step-following properties, and therefore can adhere well to the uneven transparent member surface. In addition, a three-dimensional transparent member may have a bent portion that is bent linearly or a curved portion that is curved curved in a curved line in a cross section in the thickness direction. The adhesive sheet attachment surface of the transparent member may have a shape that is bent or curved in any one direction, or may have a shape that is bent or curved in two directions that intersect (for example, perpendicular to) the one direction in addition to the one direction. In other words, the adhesive sheet attachment surface of the transparent member may have a two-dimensional or three-dimensional structure.

The adhesive sheet disclosed herein can be preferably used in portable electronic devices. In the portable electronic devices, the adhesive sheet can be preferably used for applications in which the adhesive sheet is attached to a transparent member or for fixing members, at least one of which is a transparent member. In the portable electronic devices, the adhesive sheet can be preferably used for applications in which the adhesive sheet is attached to an image display surface, a decorative surface, or a colored surface. For example, the adhesive sheet disclosed herein can be preferably used for applications in which the image display surface, a decorative surface, or a colored surface of a component member (e.g., a decorative film) is fixed to the inside of a transparent housing as a transparent member. With such a configuration, the decorative surface, etc. can be seen from the outside of the housing, while, for example, in an embodiment in which a member having a colored surface is used, the adhesive sheet can have internal concealment properties, making it particularly suitable as an exterior structure such as a case.

Non-limiting examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including glasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as an accessory, earwear devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not mean that the device is merely portable, but rather that the device has a level of portability that allows an individual (average adult) to carry it relatively easily.

The matters disclosed in this specification include the following.
[1] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a release film laminated on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet,
A pressure-sensitive adhesive sheet with a release film, wherein the maximum height Rz of the adhesive surface of the release film is 400 nm or less.
[2] The pressure-sensitive adhesive sheet with a release film according to the above-mentioned [1], wherein the arithmetic mean roughness Ra of the adhesive surface of the release film is 30 nm or less.
[3] The pressure-sensitive adhesive sheet with a release film according to the above [1] or [2], wherein the peel strength of the release film from the pressure-sensitive adhesive sheet is 1 N/50 mm or less.
[4] The pressure-sensitive adhesive sheet with a release film according to any one of the above [1] to [3], wherein the thickness of the release film is within the range of 50 to 125 μm.
[5] The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [4] above, wherein the pressure-sensitive adhesive sheet has a total light transmittance of 85% or more and a haze value of 1% or less.
[6] The pressure-sensitive adhesive sheet with a release film according to any one of the above-mentioned [1] to [5], wherein the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer and a supporting substrate laminated on one side of the pressure-sensitive adhesive layer.
[7] The pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive surface and a second pressure-sensitive adhesive surface,
The release film includes a first release film disposed on the first adhesive surface and a second release film disposed on the second adhesive surface,
The pressure-sensitive adhesive sheet with release film according to any one of [1] to [5] above, wherein the maximum height _Rz1 of the first adhesive surface S1 of the first release film and the maximum height _Rz2 of the second adhesive surface S2 of the second release film are both 400 nm or less.
[8] The pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive surface and a second pressure-sensitive adhesive surface,
The release film is a double-sided release film having a first release surface and a second release surface,
The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [5] above, wherein the maximum height _Rz1 of the first release surface of the release film and the maximum height _Rz2 of the second release surface of the release film are both 400 nm or less.
[9] The pressure-sensitive adhesive sheet with a release film according to any one of the above-mentioned [1] to [8], wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer.
[10] The pressure-sensitive adhesive sheet with a release film according to any one of the above [1] to [9], wherein the pressure-sensitive adhesive layer has a gel fraction of 30 to 95% by weight.
[11] The pressure-sensitive adhesive sheet with a release film according to any one of the above [1] to [10], wherein the pressure-sensitive adhesive sheet has a storage modulus at 25° C. of 4×10 ⁴ Pa or more.
[12] The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [11] above, wherein the pressure-sensitive adhesive sheet has a thickness of 5 to 100 μm.
[13] The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [12] above, wherein the pressure-sensitive adhesive sheet has a modulus of elasticity of 3.0 MPa or more as measured by the following tensile test.
[Tensile test]
The adhesive layer of the adhesive sheet is irradiated with ultraviolet light at an illuminance of 300 mW/ ^cm2 and an accumulated light quantity of 3000 mJ/ ^cm2 , and then aged at 50°C for 48 hours, after which the adhesive layer is cut to a size of 10 mm in width and 150 mm in length to prepare a test piece. A tensile test is performed on the test piece using a tensile tester under conditions of 23°C and 50% RH, with a chuck distance of 120 mm and a tensile speed of 50 mm/min to obtain a stress-displacement curve, and the elastic modulus [MPa] is calculated from the initial slope.
[14] The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [13] above, wherein the pressure-sensitive adhesive sheet has an impact resistance of 2.0 J/10 ^mm2 or more as measured by the following shear impact test.
[Shear impact test]
A shear impact test is performed using a pendulum-type adhesive shear impact tester based on JIS K6855. As a measurement sample, a first surface of the 10 mm square pressure-sensitive adhesive sheet is attached to the center of a 25 mm square, 1.7 mm thick chemically strengthened glass plate, and then a second surface of the pressure-sensitive adhesive sheet is attached to the center of a 40 mm square stainless steel plate (SUS304BA plate) and pressed with a load of 5 N for 10 seconds, followed by autoclaving (50°C, 0.5 MPa, 15 minutes), irradiating with ultraviolet light from the glass plate side under conditions of an illuminance of 300 mW/ ^cm2 and an integrated light quantity of 3000 mJ/ ^cm2 , and then aging at 50°C for 48 hours.
The measurement sample was fixed with the stainless steel plate facing down, and the impact resistance [J/10 mm2] was determined by measuring the absorbed energy [J] when a hammer was struck against the outer peripheral side of the glass plate under conditions of a hammer energy of 2.75 J and a hammer speed of 3.5 m/sec in an environment of 23°C and ^50% RH.
[15] The pressure-sensitive adhesive sheet with a release film according to any one of the above [1] to [14], wherein the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet contains a polymer (A) and a photoreactive monomer (B).
[16] The pressure-sensitive adhesive sheet with a release film according to the above-mentioned [15], wherein the photoreactive monomer (B) contains a compound B1 having a ring structure and two or more ethylenically unsaturated groups in the molecule, and the compound B1 has a molecular weight per one of the ethylenically unsaturated groups of 100 g/mol or more.

[17] The pressure-sensitive adhesive sheet with a release film according to the above [16], wherein the compound B1 contains at least one structure selected from the group consisting of a bisphenol A structure, a bisphenol F structure and a bisphenol E structure in the molecule.
[18] The pressure-sensitive adhesive sheet with a release film according to the above [16] or [17], wherein the compound B1 contains an aliphatic ring structure as the ring structure.
[19] The pressure-sensitive adhesive sheet with a release film according to any one of [16] to [18] above, wherein the compound B1 contains, in the molecule, at least one structure selected from the group consisting of a hydroxyl group and an amino group.
[20] The pressure-sensitive adhesive sheet with a release film according to any one of [16] to [19] above, wherein the content of the compound B1 in the pressure-sensitive adhesive layer is 0.5 parts by weight or more and 60 parts by weight or less per 100 parts by weight of the polymer (A).
[21] The pressure-sensitive adhesive layer comprises, as the photoreactive monomer (B), the compound B1 and a compound B2 having two or more functional groups and not having a ring structure in the molecule. The pressure-sensitive adhesive sheet with a release film according to any one of [16] to [20] above.
[22] The pressure-sensitive adhesive sheet with a release film according to the above [21], wherein the functional group equivalent of the above compound B2 is smaller than the functional group equivalent of the above compound B1.
[23] The pressure-sensitive adhesive sheet with a release film according to the above [21] or [22], wherein the functional group equivalent of the compound B2 is 400 g/mol or less.
[24] The pressure-sensitive adhesive sheet with a release film according to any one of [21] to [23] above, wherein the content of the compound B2 in the pressure-sensitive adhesive layer is 25 parts by weight or less per 100 parts by weight of the polymer (A).
[25] The content of the photoreactive monomer (B) in the pressure-sensitive adhesive layer is 1 part by weight or more and 80 parts by weight or less per 100 parts by weight of the polymer (A).
[26] The pressure-sensitive adhesive sheet with a release film according to any one of [15] to [25] above, wherein the polymer (A) is an acrylic polymer.
[27] The pressure-sensitive adhesive sheet with a release film according to the above-mentioned [26], wherein the monomer component constituting the acrylic polymer includes a monomer having a nitrogen atom-containing ring.
[28] The pressure-sensitive adhesive sheet with a release film according to any one of [15] to [27] above, wherein the glass transition temperature of the polymer (A) is −45° C. or higher and lower than 0° C.
[29] The pressure-sensitive adhesive sheet with a release film according to any one of [15] to [28] above, wherein the pressure-sensitive adhesive layer is crosslinked with a crosslinking agent.
[30] The pressure-sensitive adhesive sheet with a release film according to any one of [15] to [29] above, wherein the pressure-sensitive adhesive layer contains a photopolymerization initiator.
[31] The pressure-sensitive adhesive sheet with a release film according to any one of [15] to [30] above, wherein the pressure-sensitive adhesive layer contains a silane coupling agent.
[32] The pressure-sensitive adhesive sheet with a release film according to any one of [1] to [31] above, wherein the pressure-sensitive adhesive sheet has an adhesive strength to glass of 1.0 N/20 mm or more.

[33] The pressure-sensitive adhesive sheet with a release film according to any one of the above [1] to [32], which is used for fixing a member having an image display surface, a decorative surface or a colored surface to a transparent member.
[34] A roll of an adhesive sheet with a release film, comprising the adhesive sheet with a release film according to any one of [1] to [33] above wound thereon.

Several examples of the present invention are described below, but it is not intended that the present invention be limited to those shown in the examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Evaluation method>
[Total light transmittance and haze value]
One release film is peeled off from the adhesive sheet with release film, and the sheet is attached to a glass slide (manufactured by Matsunami Glass Industry Co., Ltd., product name "White Polishing No. 1", thickness 0.8 to 1.0 mm, total light transmittance 92%, haze value 0.2%). Next, the other release film is peeled off to prepare a test piece having a layer structure of adhesive sheet/glass slide. The total light transmittance and haze value of the test piece thus obtained are measured using a haze meter (device name "HM-150N", manufactured by Murakami Color Research Institute). The above measurement is preferably performed by placing the glass plate to which the adhesive sheet is attached so that the adhesive sheet faces the light source.

[Adhesion to glass]
The adhesive sheet with release film is cut to a length of 100 mm and a width of 20 mm. Next, one of the release films of the adhesive sheet with release film is peeled off, and a PET film (trade name "Lumirror S-10", manufactured by Toray Industries, Inc., thickness 25 μm) is backed up. Next, the release film on the other side (measurement surface side) is peeled off, and a 2 kg roller is moved back and forth once to press the glass plate (trade name "Soda Lime Glass #0050", manufactured by Matsunami Glass Industry Co., Ltd.) as a test plate, to prepare a test piece consisting of test plate/adhesive sheet/PET film. The obtained test piece is autoclaved (50°C, 0.5 MPa, 15 minutes), and then allowed to cool for 30 minutes under an atmosphere of 23°C and 50% RH. After cooling, the peel strength is measured using a tensile tester (machine name "Autograph AG-IS", manufactured by Shimadzu Corporation) when peeling the pressure sensitive adhesive sheet (measurement surface side) from the test plate under conditions of 23°C, 50% RH, a pulling speed of 300 mm/min, and a peel angle of 180° in accordance with JIS Z 0237. This is the adhesion strength to glass [N/20 mm].
In the case of a pressure-sensitive adhesive sheet protected by a release film having release surfaces on both sides, or in the case of a single-sided pressure-sensitive adhesive sheet, it is not necessary to peel off one of the release films or to back it with a PET film.

[Release strength of release film]
The adhesive sheet with release film is cut to a length of 150 mm and a width of 50 mm, which is fixed to a test plate, and the release film on the light release side is peeled off from the adhesive sheet using a tensile tester (device name "Autograph AG-IS", manufactured by Shimadzu Corporation) under conditions of an atmosphere of 23°C, 50% RH, a tensile speed of 300 mm/min, and a peel angle of 180°. Excluding the section of 30 mm from the start of peeling, the maximum value in the following 50 mm section is defined as the release film peel force (light release side) [N/50 mm].
The peeling force of the release film on the heavy release side was measured by peeling off the release film on the light release side that protects the adhesive sheet with the release film, backing it with a PET film (product name "Lumirror S-10", manufactured by Toray Industries, Inc., thickness 25 μm), fixing the PET film side to a test plate, and using a tensile tester (device name "Autograph AG-IS", manufactured by Shimadzu Corporation) in an atmosphere of 23°C and 50% RH, at a tensile speed of 300 mm/min and a peel angle of 180°, the release film on the heavy release side was peeled off from the adhesive sheet. The maximum value in the following 50 mm section, excluding the section 30 mm from the start of peeling, was taken as the release film peeling force (heavy release side) [N/50 mm].
In the case of an adhesive sheet protected by a release film with both sides being release surfaces, or in the case of a single-sided adhesive sheet, it is sufficient to carry out the measurement of the release force of one of the release surfaces in the same manner as the measurement of the release force of the release film on the light release side described above, and no backing with a PET film is required.

[Arithmetic mean roughness (Ra) and maximum height (Rz)]
The arithmetic mean roughness (Ra) and maximum height (Rz) of the adhesive surface of the adhesive sheet are measured as follows: Under the above-mentioned conditions for measuring the peel strength of the release film, the release film is peeled off from the adhesive sheet with the release film at a peel angle of 180° at a speed of 300 mm/min, and the exposed adhesive surface after standing for 30 minutes is measured for the surface shape using a three-dimensional optical profiler (product name "NewView7300", manufactured by ZYGO Corporation) in an environment of 23°C and 50% RH.
The arithmetic surface roughness Ra is calculated from the measured data in accordance with JIS B 0601-2001. The maximum height (Rz) is calculated as the sum of the height Rp of the highest peak above the average line of the roughness curve and the depth Rv of the deepest valley below the average line of the data (roughness curve) obtained by the above measurement. The measurement conditions are as follows. The measurements of Ra and Rz are carried out five times (i.e., N=5), and the average values thereof are used.
(Measurement conditions)
Measurement area: 5.62mm x 4.22mm
(Objective lens: 2.5x, internal lens: 0.5x)
Analysis mode:
Remove: Cylinder
Data Fill: ON (Max: 25)
Remove Spikes: ON (xRMS: 1)
Filter: OFF

[Optical distortion evaluation]
A commercially available mirror (thickness 2 mm) made by silver-coating method on raw glass is prepared, and it is confirmed that there is no distortion by visually observing and projecting a reflected image on a screen by the same method as described below with the mirror alone. In a clean room, the surface of the mirror is cleaned with a clean cloth to remove foreign matter, and then one release film of the adhesive sheet with release film is peeled off from the adhesive sheet, and the surface of the mirror is attached with an appropriate tension so that foreign matter, air bubbles, and deformation lines do not enter, and a degassing process is performed using a pressurized degassing device (autoclave) to remove the influence of minute air bubbles (treatment conditions: 50 ° C, 0.5 MPa, 15 minutes). After cooling at room temperature for 30 minutes or more, the other release film is peeled off from the adhesive sheet to create an optical distortion evaluation sample (a laminate consisting of an adhesive sheet and a mirror). The evaluation sample is placed so that the adhesive sheet side faces the point light source side and the angle with respect to the light beam from the point light source is about 45 degrees. A white screen is placed at the end of the light beam to reflect the reflected image. The point light source may be a Xenon Lamp C2577 manufactured by Hamamatsu Photonics KK or an equivalent product. The point light source, evaluation sample, and screen are positioned such that the distance between the evaluation sample and the point light source, and the distance between the evaluation sample and the screen are each about 50 cm.
The point light source is turned on, and the image reflected by the sample and projected onto the screen is visually observed to evaluate the presence and degree of optical distortion according to the following three levels.
E: No optical distortion is observed.
A: Some optical distortion is observed, but is tolerable for practical use.
P: Obvious optical distortion is observed.

[Elastic modulus by tensile test]
A test specimen was prepared by cutting an adhesive sheet (adhesive layer) with a release film to a size of 10 mm in width and 150 mm in length, and the two release films were peeled off to expose the adhesive layer in an environment of 23°C and 50% RH. A tensile test was then performed on the test specimen using a tensile tester (device name "Autograph AG-IS", manufactured by Shimadzu Corporation) under conditions of a chuck distance of 120 mm and a tensile speed of 50 mm/min to obtain an S-S curve, and the elastic modulus [MPa] was calculated from the initial slope (the elastic deformation region of the S-S curve, specifically the slope in the range where the displacement is less than approximately 5%).

The thickness of the test piece used in the tensile test may be the same as or different from the thickness of the adhesive sheet (typically the adhesive layer) as described above. For example, when the thickness of the adhesive sheet is relatively small, the results of the tensile test performed using a test piece prepared to have a thickness of 5 μm or more (for example, about 5 μm to 200 μm) for the purpose of improving operability, etc., can be used as the elastic modulus of the adhesive sheet. For example, the thickness of the test piece can be adjusted by appropriately overlapping the adhesive layer before ultraviolet irradiation in the case of a photocurable adhesive sheet. In addition, a test piece having a thickness that makes it easy to perform a tensile test can be prepared using the same adhesive composition as that used to form the adhesive layer to be measured, and the results of the tensile test performed on the test piece can be used as the elastic modulus of the adhesive layer. The tensile test can be performed, for example, using a test piece having a thickness of about 10 μm to 50 μm (preferably, about 15 μm to 25 μm).

[Impact resistance]
A shear impact test is performed using a pendulum-type adhesive shear impact tester based on JIS K 6855. As a measurement sample, a pressure-sensitive adhesive sheet with a release film is cut into a 10 mm square, one release film is peeled off to expose the first adhesive surface of the pressure-sensitive adhesive sheet, the first adhesive surface is attached to the center of a 25 mm square, 1.7 mm thick chemically strengthened glass plate (manufactured by Corning), the other release film is peeled off to expose the second adhesive surface of the pressure-sensitive adhesive sheet, the second adhesive surface is attached to the center of a 40 mm square stainless steel plate (SUS304BA plate) and pressed with a load of 5 N for 10 seconds, then autoclaved (50 ° C, 0.5 MPa, 15 minutes), irradiated with ultraviolet light from the glass plate side under conditions of an illuminance of 300 mW / cm ² and an accumulated light amount of 3000 mJ / cm ² using a high-pressure mercury lamp, and then aged at 50 ° C for 48 hours.
The measurement sample is fixed with the stainless steel plate facing downward, and a hammer is applied to the outer peripheral side surface of the glass plate at a hammer energy of 2.75 J and a hammer speed (impact speed) of 3.5 m/sec in an environment of 23° C. and 50% RH, and the absorbed energy [J] is measured to determine the impact resistance [J/10 mm ² ]. The measurement is performed three times, and the arithmetic average value is used.
In the case of a pressure-sensitive adhesive sheet protected by a release film having release surfaces on both sides, the measurement can be carried out in the same manner as above, except that only one release film is peeled off.

In addition, the adhesive sheet disclosed herein includes an adhesive sheet in a form in which the adhesive layer is photocured after being attached to an adherend, so that at least the photocurable adhesive sheet (for example, the adhesive sheet of Example 4 having the adhesive C described later) is irradiated with ultraviolet light under conditions of an illuminance of 300 mW/cm ² and an integrated light amount of 3000 mJ/cm ² , and aged at 50 ° C for 48 hours, and then the above measurements (total light transmittance, haze value, adhesive strength to glass, arithmetic mean roughness (Ra) and maximum height (Rz) of the adhesive surface, optical distortion evaluation, elastic modulus by tensile test) are performed using the measurement sample. Regarding the adhesive strength to glass, the photocurable adhesive sheet (for example, the adhesive sheet of Example 4 having the adhesive C described later) is pressed onto a test plate, and then ultraviolet light is irradiated under the above conditions to perform the measurement. In addition, when the release film is transparent, the ultraviolet irradiation process is preferably performed in a state in which the adhesive sheet (typically the adhesive layer) is sandwiched between the transparent release films.
It is desirable to measure the illuminance and amount of light of the light source using an industrial UV checker (model "UVR-T2", light receiving part "UD-T36T2", manufactured by TOPCON) by adjusting the actual distance between the light source and the sample.

<Example 1>
(Preparation of Pressure-Sensitive Adhesive Composition)
As monomer components, 57 parts of n-butyl acrylate (BA), 12 parts of cyclohexyl acrylate (CHA), 23 parts of 4-hydroxybutyl acrylate (4HBA), 8 parts of hydroxyethyl acrylate (HEA), 0.075 parts of trade name "Irgacure 651" (manufactured by BASF Corporation) and 0.075 parts of trade name "Irgacure 184" (manufactured by BASF Corporation) were mixed, and then this monomer mixture was exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, thereby obtaining a partially polymerized product (acrylic polymer syrup) with a polymerization rate of about 10%. To 100 parts of the obtained acrylic polymer syrup, 0.14 parts of dipentaerythritol hexaacrylate (trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) and 0.3 parts of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed uniformly, thereby obtaining an acrylic pressure-sensitive adhesive composition A.

(Preparation of adhesive sheet)
As the first release film, a PET release film having a thickness of 75 μm and a silicone-based release treatment agent on the first adhesive surface side surface S1, which is the surface to be laminated on the first adhesive surface of the adhesive sheet, and a Ra of 18 nm and an Rz of 223 nm on the surface S1 was prepared. As the second release film, a PET release film having a thickness of 100 μm and a silicone-based release treatment agent on the second adhesive surface side surface S2, which is the surface to be laminated on the second adhesive surface of the adhesive sheet, and a Ra of 18 nm and an Rz of 223 nm on the surface S2 was prepared.
The acrylic adhesive composition A obtained above was applied to the first adhesive surface S1 of the first release film so that the thickness after the adhesive layer was formed was 100 μm to form an adhesive composition layer, and then the surface of the adhesive composition layer was covered with the second release film so that the second adhesive surface S2 was on the adhesive composition layer side. This blocked the adhesive composition layer from oxygen. Thereafter, ultraviolet light was irradiated under conditions of an illuminance of 5 mW/cm ² and a light amount of 2000 mJ/cm ² to photocure the adhesive composition layer, thereby producing a substrateless double-sided adhesive sheet consisting only of an acrylic adhesive layer (also referred to as adhesive A), with each side of the acrylic adhesive layer protected by a first and second release film. The weight average molecular weight (Mw) of the acrylic polymer as the base polymer of the adhesive layer was 2 million.

<Example 2>
As the first release film and the second release film, release films having surfaces S1 and S2 having Ra and Rz shown in Table 1 were used, respectively. In addition, the thickness of the pressure-sensitive adhesive layer was changed to 25 μm. Otherwise, a substrate-less double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 above.

<Example 3>
An acrylic polymer syrup was prepared in the same manner as in Example 1 above, except that the monomer components were changed to 68 parts of 2-ethylhexyl acrylate (2EHA), 15 parts of N-vinyl-2-pyrrolidone (NVP), and 17 parts of HEA, and an acrylic pressure-sensitive adhesive composition B was obtained in the same manner as in Example 1 above, except that the obtained acrylic pressure-sensitive adhesive composition B was used and the thickness of the pressure-sensitive adhesive layer (also referred to as pressure-sensitive adhesive B) was changed to 50 μm, and a substrate-less double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 2 above.

<Example 4>
(Preparation of Pressure-Sensitive Adhesive Composition)
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 60 parts of BA, 6 parts of CHA, 18 parts of NVP, 1 part of isostearyl acrylate (iSTA) and 15 parts of 4HBA as monomer components, 0.085 parts of α-thioglycerol as a chain transfer agent, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a polymerization solvent were added so that the monomer components were 45%, and nitrogen gas was flowed and nitrogen replacement was performed for about 1 hour while stirring. Thereafter, the reaction vessel was heated to 60 ° C. and reacted for 7 hours to obtain an acrylic polymer with a weight average molecular weight (Mw) of 350,000. To this acrylic polymer solution (100 parts solids), 0.1 part on a solids basis of trimethylolpropane/xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-110N", solids concentration 75%) as an isocyanate crosslinking agent, 0.01 part of dioctyltin dilaurate (manufactured by Tokyo Fine Chemicals, product name "Embirizer OL-1") as a crosslinking accelerator, 4 parts of acetylacetone as a crosslinking retarder, and silane coupling agent were added. 0.3 parts of 3-glycidoxypropyltrimethoxysilane (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) as a binder, 8 parts of dipentaerythritol hexaacrylate (trade name "A-DPH", manufactured by Shin-Nakamura Chemical Co., Ltd.) and 12 parts of tricyclodecane dimethanol diacrylate (trade name "A-DCP", manufactured by Shin-Nakamura Chemical Co., Ltd.) as photoreactive monomers, and 0.7 parts of 1-hydroxycyclohexyl-phenyl-ketone (trade name "Omnirad184", manufactured by IGM Regins) as a photopolymerization initiator were added and mixed uniformly to prepare a pressure-sensitive adhesive composition C according to this example.

(Preparation of adhesive sheet)
As the first release film and the second release film, release films having surfaces S1 and S2 having Ra and Rz shown in Table 1 were used, respectively.
The adhesive composition C obtained above was applied to the first adhesive surface S1 of the first release film so that the thickness after drying was 20 μm, and the adhesive composition C was dried by heating at normal pressure at 60 ° C for 1 minute and at 120 ° C for 3 minutes, and then aged at 23 ° C for 120 hours to form a photocurable adhesive layer (substrate-less double-sided adhesive sheet). The second adhesive surface S2 of the second release film was attached to the surface of this photocurable adhesive layer to protect it. In this way, a substrate-less double-sided adhesive sheet was produced, which was composed only of a photocurable acrylic adhesive layer (also referred to as adhesive C) and in which each side of the photocurable acrylic adhesive layer was protected by the first and second release films.

<Example 5>
As the first release film and the second release film, release films having surfaces S1 and S2 having Ra and Rz shown in Table 1 were used, respectively. In addition, the thickness of the pressure-sensitive adhesive layer was changed to 100 μm. Otherwise, a substrate-less double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 3 above.

<Examples 6-7>
The first and second release films used were release films having surfaces S1 and S2 with Ra and Rz shown in Table 1. The thickness of the pressure-sensitive adhesive layer was changed to 25 μm in Example 6. The rest of the thickness was the same as in Example 1 above, and substrate-less double-sided pressure-sensitive adhesive sheets according to each example were produced.

<Evaluation>
The adhesive sheets with release film according to each example were evaluated for total light transmittance [%], haze value [%], adhesion to glass [N/20 mm], peeling strength of the release film [N/50 mm], arithmetic mean roughness (Ra) [nm] of the adhesive surface, maximum height (Rz) [nm], and optical distortion. The results are shown in Table 1. In addition, the adhesive sheet of Example 4 was subjected to a tensile test to measure the elastic modulus, and the adhesive sheets of Examples 1 to 4 were subjected to an impact resistance test. Table 1 also shows an overview of each example (release surface Ra and Rz of the release film, adhesive type, adhesive sheet thickness [μm], 25°C storage modulus [Pa], gel fraction [%]).

As shown in Table 1, in Examples 1 to 5, the maximum height Rz of the adhesive side surface of the release film was 400 nm or less, and in the pressure-sensitive adhesive sheets of these examples, after the release film was peeled off, no optical distortion was observed, or the optical distortion was within a practically acceptable range. In addition, the arithmetic mean roughness Ra of the adhesive side surface of the release film of these examples was 30 nm or less, and the peeling force of the release film was 1 N/50 mm or less. On the other hand, in Examples 6 to 7, the maximum height Rz of the adhesive side surface of the release film exceeded 400 nm, and unevenness was observed in the optical distortion evaluation. The elastic modulus of the pressure-sensitive adhesive sheet of Example 4 was 3.0 MPa or more in the tensile test, and the pressure-sensitive adhesive sheets of Examples 1 to 4 all had impact resistance of 2.0 J/10 mm ² or more.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

Reference Signs List 1, 2 Adhesive sheet with release film 10 Adhesive sheet 10a First adhesive surface, adhesive surface 10b Second adhesive surface 12 Adhesive layer 12a First surface 12b Second surface 14 Support substrate 14a Adhesive layer side surface 14b Back surface 21 First release film, release film 21a First adhesive surface side surface S1 (release surface), adhesive surface side surface (release surface)
22 Second release film 22a Second adhesive surface S2 (release surface)
50 Core 100, 200 Roll body (adhesive sheet roll)

Claims (14)

The adhesive sheet has a pressure-sensitive adhesive layer, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive sheet.
the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive surface and a second pressure-sensitive adhesive surface,
The release film includes a first release film disposed on the first adhesive surface and a second release film disposed on the second adhesive surface,
a maximum height _Rz1 of the first adhesive surface S1 of the first release film and a maximum height _Rz2 of the second adhesive surface S2 of the second release film are both 240 nm or less;
A pressure-sensitive adhesive sheet with a release film, wherein the arithmetic mean roughness Ra of the back surface of the first release film and the arithmetic mean roughness Ra of the back surface of the second release film are greater than 35 nm. The adhesive sheet with release film according to claim 1, wherein the arithmetic mean roughness Ra of the first adhesive surface S1 of the first release film and the arithmetic mean roughness Ra of the second adhesive surface S2 of the second release film are 30 nm or less. The adhesive sheet with release film according to claim 1 or 2, wherein the peel strength of the first release film and the peel strength of the second release film relative to the adhesive sheet are 1 N/50 mm or less. The adhesive sheet with release film according to any one of claims 1 to 3, wherein the thickness of the first release film and the thickness of the second release film are both within the range of 50 to 125 μm. The adhesive sheet with release film according to any one of claims 1 to 4, wherein the total light transmittance of the adhesive sheet is 85% or more and the haze value is 1% or less. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 5 , wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 6 , wherein the pressure-sensitive adhesive layer has a gel fraction of 30 to 95% by weight. 8. The pressure-sensitive adhesive sheet with a release film according to claim 1 , wherein the pressure-sensitive adhesive layer has a storage modulus at 25° C. of 4×10 ⁴ Pa or more. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 8 , wherein the pressure-sensitive adhesive sheet has a thickness of 5 to 100 µm. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 9 , wherein the pressure-sensitive adhesive sheet has an elastic modulus of 3.0 MPa or more as measured by the following tensile test.
[Tensile test]
The adhesive layer of the adhesive sheet is irradiated with ultraviolet light at an illuminance of 300 mW/ ^cm2 and an accumulated light quantity of 3000 mJ/ ^cm2 , and then aged at 50°C for 48 hours, after which the adhesive layer is cut to a size of 10 mm in width and 150 mm in length to prepare a test piece. A tensile test is performed on the test piece using a tensile tester under conditions of 23°C and 50% RH, with a chuck distance of 120 mm and a tensile speed of 50 mm/min, to obtain a stress-displacement curve, and the elastic modulus [MPa] is calculated from the initial slope. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 10 , wherein the pressure-sensitive adhesive layer contains a polymer (A) and a photoreactive monomer (B). 12. The pressure-sensitive adhesive sheet with a release film according to claim 11, wherein the photoreactive monomer ( B ) comprises a compound B1 having a ring structure and two or more ethylenically unsaturated groups in the molecule, and the compound B1 has a molecular weight per one ethylenically unsaturated group of 100 g/mol or more. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 12 , which is used for fixing a member having an image display surface, a decorative surface or a colored surface to a transparent member. A roll of an adhesive sheet with a release film, comprising the adhesive sheet with a release film according to any one of claims 1 to 13 wound thereon.

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