JP7638640B2 - Reinforcing films, optical and electronic components - Google Patents

Description

The present invention relates to a reinforcing film, and optical and electronic components to which the reinforcing film is attached.

Adhesives in the form of adhesive sheets are widely used in various applications in portable electronic devices such as mobile phones, smartphones, and tablet computers, as well as other electronic devices, for the purpose of bonding adherends together or fixing objects to adherends. For example, adhesive sheets are used as reinforcing materials (reinforcing films) that impart rigidity and impact resistance to the optical and electronic components that make up the above-mentioned devices. Patent documents 1 and 2 are cited as documents disclosing this type of prior art.

Furthermore, in recent years, portable electronic devices that can be folded or rolled have been attracting attention, and progress has been made in the development of adhesive sheets that can be used to fix flexible devices (typically image display devices such as organic electroluminescence (EL) and liquid crystal display devices) built into such electronic devices (Patent Documents 3 to 6).

On the other hand, looking at the performance of the adhesive, recently, an adhesive sheet has been proposed that shows low adhesive strength when first applied to an adherend, but can then increase significantly in adhesive strength (Patent Document 7). An adhesive sheet with such properties exhibits reworkability (reworkability) that is useful for preventing a decrease in yield due to incorrect or failed application of the adhesive sheet before the increase in adhesive strength, and can exhibit strong adhesiveness that is suitable for the intended purpose of the adhesive sheet after the increase in adhesive strength.

Patent No. 6366199 Patent No. 6366200 Patent No. 6376271 JP 2016-108555 A JP 2017-095657 A JP 2017-095659 A Patent No. 6373458

The reinforcing film can also be used in the flexible device. For example, in the manufacture of the flexible device, since the components constituting the device are often thin, it is desirable to apply an adhesive sheet as a reinforcing film to reinforce the device and prevent defects caused by deformation and improve handling. Since flexible devices can be repeatedly folded or bent, the reinforcing film used in the flexible device is required to have the property of recovering the shape normally even when repeatedly bent (bending recovery) and the property of not causing defects such as peeling (bending retention). A reinforcing film having such bending recovery and bending retention can be used for various purposes including flexible devices, and is useful with few restrictions on the range of application.

For example, as proposed in Patent Document 7, an adhesive that exhibits low adhesion at the beginning of application and then increases significantly in adhesion is also desirable to have flex recovery and flex retention when used as a reinforcing film. One method for improving flex retention is, for example, appropriately setting the storage modulus of the adhesive. However, when the storage modulus of an adhesive designed to increase in adhesion as described above is changed, both the initial low adhesion and the adhesion after the increase are affected. Also, when considering flex recovery in addition to flex retention, it is not easy to satisfy all of these characteristics. It would be practically useful to be able to improve flex recovery and flex retention for an adhesive that exhibits low adhesion at the beginning of application and then increases significantly in adhesion.

The present invention was created in consideration of the above circumstances, and aims to provide a reinforcing film that exhibits easy peelability when initially attached to an adherend, can then significantly increase its adhesive strength, and has flex recovery and flex retention. Another aim of the present invention is to provide optical and electronic components to which the reinforcing film is attached.

According to the present specification, a reinforcing film having a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer includes a polymer (A) and a polymer (B). The polymer (B) includes a monomer unit having a polyorganosiloxane skeleton and a (meth)acrylic monomer unit. The pressure-sensitive adhesive layer has a surface elastic modulus of 1 to 20 kPa at 23°C. Furthermore, the weight average molecular weight of the polymer (B) is 10,000 to 100,000.

According to the above configuration, the adhesive layer contains the polymer (A) and the polymer (B) containing a monomer unit having a polyorganosiloxane skeleton, so that it exhibits light peelability at the beginning of application to the adherend, and can then significantly increase its adhesive strength. In addition, by using the polymer (B) having a weight average molecular weight in the range of 10,000 to 100,000, it is possible to better achieve both light peelability at the beginning of application and increased adhesive strength. In addition, the reinforcing film has flex recovery and flex retention. Specifically, a reinforcing film in which the surface modulus of elasticity at 23°C (23°C surface modulus) of the adhesive layer is 1 kPa or more exhibits the above-mentioned adhesive properties while exhibiting good flex recovery. In addition, since the 23°C surface modulus of the adhesive layer is 20 kPa or less, it exhibits the above-mentioned adhesive properties while exhibiting good flex retention, so that even when used in a manner in which it is repeatedly folded, problems such as peeling are unlikely to occur.

In some preferred embodiments of the technology disclosed herein (including reinforcing films, optical members, and electronic members; the same applies below), the pressure-sensitive adhesive layer has a bulk modulus _G'23 of 10 to 200 kPa at 23°C. A pressure-sensitive adhesive having a bulk modulus _G'23 in this range tends to provide a suitable range of adhesive strength at the initial stage of application that provides excellent light peelability. In addition, the pressure-sensitive adhesive has excellent processability and generally tends to provide both strain relaxation and flex recovery in the normal temperature range.

In some preferred embodiments, the pressure-sensitive adhesive layer has a bulk modulus _G'80 at 80°C of 5 to 100 kPa. A pressure-sensitive adhesive having a bulk modulus _G'80 in this range generally tends to achieve both flex recovery and flex retention. For example, even when used under high temperature conditions of around 80°C, the pressure-sensitive adhesive may have elasticity suitable for flex recovery and adhesive retention that realizes flex retention.

In some preferred embodiments, the pressure-sensitive adhesive layer has a tan δ ₈₀ at 80° C. of 0.10 to 0.60. A pressure-sensitive adhesive having the above tan δ ₈₀ (loss modulus G″ ₈₀ at 80° C./storage modulus G′ ₈₀ at 80° C.) of 0.10 or more is likely to exhibit adhesive strength suitable for bending retention. Furthermore, by having the above tan δ ₈₀ of 0.60 or less, plastic deformation of the pressure-sensitive adhesive is suppressed and good bending recovery is likely to be obtained. Furthermore, even when the reinforcing film is held in a bent state for a long period of time, it is likely to exhibit a holding force (bending holding force) that does not cause peeling from the adherend.

The polymer (A) is preferably an acrylic polymer. The effects of the technology disclosed herein are preferably achieved by an adhesive layer containing the polymer (A), which is an acrylic polymer, and the polymer (B), which contains a monomer unit having a polyorganosiloxane skeleton.

In some preferred embodiments, the content of the polymer (B) in the adhesive layer is 0.5 to 5 parts by weight per 100 parts by weight of the polymer (A). By setting the amount of polymer (B) to 0.5 parts by weight or more per 100 parts by weight of polymer (A), it is easy to obtain light peelability at the initial stage of application. By setting the amount of the polymer (B) to 5 parts by weight or less, it is easy to achieve the desired increase in adhesive strength. In addition, by setting the amount of polymer (B) used within the above range, it is easy to achieve good bending recovery and bending retention.

In some preferred embodiments, the molar ratio ([NCO]/[OH]) of the isocyanate group and the hydroxyl group contained in the pressure-sensitive adhesive layer is 0.002 to 0.03. A pressure-sensitive adhesive layer having a molar ratio ([NCO]/[OH]) of 0.002 or more tends to have excellent bending recovery and excellent processability. In addition, by setting the molar ratio ([NCO]/[OH]) to 0.03 or less, it tends to be easier to achieve a suitable increase in adhesive strength. In the pressure-sensitive adhesive layer, the isocyanate group and the hydroxyl group may exist in a state where at least a portion of them are chemically bonded (crosslinked). The pressure-sensitive adhesive layer may, for example, contain a crosslinking agent, and in such a configuration, the isocyanate group may, for example, be part of the crosslinking agent, and the hydroxyl group may, for example, be part of the polymer (A).

The reinforcing film disclosed herein is suitable as a reinforcing film that imparts rigidity and impact resistance to optical members such as polarizing plates and wavelength plates during processing or transport of the optical members. Therefore, according to this specification, an optical member to which any of the reinforcing films disclosed herein is attached is provided.

The reinforcing film disclosed herein is also suitable as a reinforcing film for electronic components of devices such as portable electronic devices. Therefore, this specification provides an electronic component to which any of the reinforcing films disclosed herein is attached.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a reinforcing film according to an embodiment. FIG. 4 is a cross-sectional view illustrating a schematic configuration of a reinforcing film according to another embodiment. FIG. 4 is a cross-sectional view illustrating a schematic configuration of a reinforcing film according to another embodiment.

Preferred embodiments of the present invention will be described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings on carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.
In the following drawings, the same reference numerals may be used to denote components or parts having the same function, and duplicated descriptions may be omitted or simplified. In addition, the embodiments shown 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 addition, in this specification, "acrylic polymer" refers to a polymer containing monomer units derived from (meth)acrylic monomers in the polymer structure, and typically refers to a polymer containing monomer units derived from (meth)acrylic monomers at a ratio of more than 50% by weight. In addition, (meth)acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl group" means acryloyl group and methacryloyl group collectively. Therefore, the concept of (meth)acrylic monomer here can include both monomers having acryloyl group (acrylic monomer) and monomers having methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" means acrylic acid and methacrylic acid, and "(meth)acrylate" means acrylate and methacrylate collectively.

<Structural example of reinforcing film>
The reinforcing film disclosed herein has the form of an adhesive sheet having an adhesive surface formed by an adhesive. The adhesive sheet used as the reinforcing film is configured to include an adhesive layer. The reinforcing film disclosed herein may be in the form of an adhesive sheet with a substrate in which the adhesive layer is laminated on one or both sides of a supporting substrate, or may be in the form of a substrate-less adhesive sheet that does not have a supporting substrate. Hereinafter, the supporting substrate may be simply referred to as a "substrate".
In this specification, the term "reinforcing film" refers to an adhesive sheet (reinforcing adhesive film) used to reinforce an adherend as described below. The reinforcing film is not limited to the form of an adhesive sheet with a substrate, for example, since it can be reinforced by attaching a support material or the like to one adhesive surface of the reinforcing film and then attaching the other adhesive surface to the adherend to be reinforced. In this respect, it is understood as a broader concept than the "reinforcing film" described below, which has the form of an adhesive sheet with a substrate.

The structure of a reinforcing film according to one embodiment is shown in FIG. 1. The reinforcing film 1 is configured as a substrate-attached single-sided adhesive sheet including a sheet-like support substrate 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. The adhesive layer 21 is fixed to the first surface 10A side of the support substrate 10. The reinforcing film 1 is used by attaching the adhesive layer 21 to an adherend. Before use (i.e., before attachment to an adherend), the reinforcing film 1 may be a component of a release-liner-attached reinforcing film 100 in which the surface (adhesive surface) 21A of the adhesive layer 21 is in contact with a release liner 31, at least the side facing the adhesive layer 21 being a release surface (release surface), as shown in FIG. As the release liner 31, for example, one configured to be a release surface by providing a release layer made of a release treatment agent on one side of a sheet-like substrate (liner substrate) can be preferably used. Alternatively, the release liner 31 may be omitted, and the supporting substrate 10 may have the second surface 10B as the release surface, and the reinforcing film 1 may be rolled up so that the adhesive surface 21A is in contact with the second surface 10B of the supporting substrate 10 (roll form). When attaching the reinforcing film 1 to an adherend, the release liner 31 or the second surface 10B of the supporting substrate 10 is peeled off from the adhesive surface 21A, and the exposed adhesive surface 21A is pressed against the adherend.

The structure of a reinforcing film according to another embodiment is shown in FIG. 2. The reinforcing film 2 is configured as a substrate-attached double-sided adhesive sheet including a sheet-like support substrate 10 having a first surface 10A and a second surface 10B, an adhesive layer 21 provided on the first surface 10A side, and an adhesive layer 22 provided on the second surface 10B side. The adhesive layer (first adhesive layer) 21 is adhered to the first surface 10A of the support substrate 10, and the adhesive layer (second adhesive layer) 22 is adhered to the second surface 10B of the support substrate 10. The reinforcing film 2 is used by attaching the adhesive layers 21 and 22 to different locations on an adherend. The locations to which the adhesive layers 21 and 22 are attached may be locations on different members, or may be different locations within a single member. As shown in FIG. 2, the reinforcing film 2 before use may be a component of a reinforcing film with a release liner 200 in which the surface (first adhesive surface) 21A of the adhesive layer 21 and the surface (second adhesive surface) 22A of the adhesive layer 22 are in contact with release liners 31 and 32, each of which has a release surface on the side facing the adhesive layers 21 and 22. As the release liners 31 and 32, for example, a sheet-like substrate (liner substrate) may be preferably used, in which a release layer made of a release treatment agent is provided on one side of the substrate so that the one side is the release surface. Alternatively, the release liner 32 may be omitted, and a release liner 31 with both sides being release surfaces may be used, which may be superimposed on the reinforcing film 2 and rolled in a spiral shape to form a reinforcing film with a release liner in which the second adhesive surface 22A is in contact with the back surface of the release liner 31 (roll form).

The structure of a reinforcing film according to yet another embodiment is shown in FIG. 3. The reinforcing film 3 is configured as a substrate-less double-sided adhesive sheet made of an adhesive layer 21. The reinforcing film 3 is used by attaching the first adhesive surface 21A, which is made up of one surface (first surface) of the adhesive layer 21, and the second adhesive surface 21B, which is made up of the other surface (second surface) of the adhesive layer 21, to different locations on the adherend. As shown in FIG. 3, the reinforcing film 3 before use may be a component of a reinforcing film 300 with a release liner in which the first adhesive surface 21A and the second adhesive surface 21B are in contact with release liners 31 and 32, each of which has a release surface at least on the side facing the adhesive layer 21. Alternatively, the release liner 32 may be omitted, and a release liner 31 with both sides being release surfaces may be used, which is superimposed on the reinforcing film 3 and rolled in a spiral shape to form a reinforcing film with a release liner in which the second adhesive surface 21B is in contact with the back surface of the release liner 31 (roll form).

The reinforcing film may be in the form of a roll or a sheet, and may be cut, punched, or otherwise processed into an appropriate shape depending on the application or mode of use. The adhesive layer in the technology disclosed herein is typically formed continuously, but is not limited to this, and may be formed in a regular or random pattern, such as a dotted or striped pattern.

<Adhesive Layer>
The reinforcing film disclosed herein includes a pressure-sensitive adhesive layer containing a polymer (A) and a polymer (B). Such a pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing a polymer (A) that is a complete or partial polymer of a monomer raw material A, and a polymer (B). The form of the pressure-sensitive adhesive composition is not particularly limited, and may be in various forms, such as a solvent type, a water-dispersed type, a hot melt type, or an active energy ray curable type (e.g., a photocurable type).

(Surface elastic modulus at 23°C)
The pressure-sensitive adhesive layer disclosed herein is characterized in that the surface elasticity of its surface (adhesive surface) at 23° C. (23° C. surface elasticity) is in the range of 1 to 20 kPa. When the 23° C. surface elasticity is 1 kPa or more, the pressure-sensitive adhesive layer can have good flexion recovery while realizing the adhesive properties based on the inclusion of polymer (A) and polymer (B). When the surface elasticity is 20 kPa or less, the pressure-sensitive adhesive layer can exhibit good flexion retention while realizing the adhesive properties.

From the viewpoint of improving flex recovery, the 23°C surface elastic modulus is preferably 2 kPa or more, more preferably 3 kPa or more, and even more preferably 4 kPa or more (e.g. 5 kPa or more), and may be 8 kPa or more, 10 kPa or more, or 12 kPa or more (e.g. 14 kPa or more). The higher the surface elastic modulus, the better the initial light peelability tends to be. In addition, from the viewpoint of achieving both good flex recovery and flex retention while favorably expressing an increase in adhesive strength, the 23°C surface elastic modulus is appropriately 15 kPa or less, and is preferably 12 kPa or less, more preferably 9 kPa or less, and even more preferably 7 kPa or less (e.g. 6 kPa or less), and may be 4 kPa or less.

The 23°C surface elastic modulus of the adhesive layer can be adjusted by the type and characteristics (molecular weight, glass transition temperature, molecular structure, etc.) of polymer (A), the type (chemical structure, etc.) and characteristics (molecular weight, glass transition temperature, etc.) of polymer (B), the amount used, and the type and amount used of the crosslinking agent. The 23°C surface elastic modulus of the adhesive layer is measured by the method described in the Examples below.

(23°C bulk elastic modulus _G'23 )
The bulk modulus G' ₂₃ at 23°C (23°C bulk modulus G' ₂₃ ) of the pressure-sensitive adhesive layer is appropriately set within a range that satisfies the above-mentioned range of the surface modulus at 23°C, and is not limited to a specific range. In some embodiments, the bulk modulus G' ₂₃ at 23°C of the pressure-sensitive adhesive layer is suitably set to 10 kPa or more. By setting the bulk modulus G' ₂₃ to a predetermined value or more, the adhesive strength at the initial stage of application tends to be in a suitable range that is excellent in light peelability. In addition, the pressure-sensitive adhesive layer has excellent processability and generally tends to have excellent flex recovery in the normal temperature range. The bulk modulus G' ₂₃ is preferably 15 kPa or more, more preferably 20 kPa or more, even more preferably 25 kPa or more, and particularly preferably 30 kPa or more. In some other embodiments, the bulk modulus G' ₂₃ may be 50 kPa or more, 80 kPa or more, or 100 kPa or more.

In some embodiments, the 23°C bulk modulus _G'23 of the pressure-sensitive adhesive layer is suitably 200 kPa or less. A pressure-sensitive adhesive having a bulk modulus _G'23 of a predetermined value or less generally tends to have excellent strain relaxation properties in the normal temperature range and is also prone to exhibiting increased adhesive strength. The bulk modulus _G'23 is preferably 150 kPa or less, more preferably 90 kPa or less. In some preferred embodiments, the bulk modulus _G'23 may be 60 kPa or less, or 40 kPa or less (e.g., 35 kPa or less).

(80°C bulk elastic modulus _G'80 )
The bulk modulus _G'80 at 80°C (80°C bulk modulus _G'80 ) of the pressure-sensitive adhesive layer is appropriately set within a range that satisfies the above-mentioned range of the surface modulus at 23°C, and is not limited to a specific range. In some embodiments, the bulk modulus _G'80 at 80°C of the pressure-sensitive adhesive layer is preferably 5 kPa or more. By setting the bulk modulus _G'80 to a predetermined value or more, the flex recovery is generally improved, and even when used under high temperature conditions, the pressure-sensitive adhesive layer can have elasticity suitable for flex recovery. In some preferred embodiments, the bulk modulus _G'80 may be 7 kPa or more, 9 kPa or more, or 10 kPa or more. In some other embodiments, the bulk modulus _G'80 may be 15 kPa or more, 30 kPa or more, or 50 kPa or more.

In some embodiments, the 80°C bulk elastic modulus _G'80 of the pressure-sensitive adhesive layer is suitably 100 kPa or less. By limiting the bulk elastic modulus _G'80 to a predetermined value or less, it is generally easy to obtain good bending retention and to achieve both bending recovery and bending retention. For example, in various environments including high temperature conditions, it may have elasticity suitable for bending recovery and adhesive retention that realizes bending retention. The bulk elastic modulus _G'80 is preferably 90 kPa or less, more preferably 60 kPa or less. In some embodiments, the bulk elastic modulus _G'80 may be 20 kPa or less, 16 kPa or less, or 14 kPa or less (e.g., 12 kPa or less).

(80℃ _tanδ80 )
The tan δ ₈₀ at 80° C. (80° C. tan δ ₈₀ ) of the pressure-sensitive adhesive layer is appropriately set within a range that satisfies the above-mentioned range of the surface elastic modulus at 23° C., and is not limited to a specific range. In some embodiments, the 80° C. tan δ ₈₀ of the pressure-sensitive adhesive layer is suitably 0.10 or more. The higher the tan δ ₈₀ , the more likely the pressure-sensitive adhesive will exhibit adhesive strength suitable for bending retention. The tan δ ₈₀ is preferably 0.20 or more. In some preferred embodiments, the tan δ ₈₀ may be 0.30 or more, 0.40 or more, or 0.45 or more.

In some embodiments, the 80°C tan δ ₈₀ of the pressure-sensitive adhesive layer is preferably 0.60 or less. By having the tan δ ₈₀ of 0.60 or less, the plastic deformation of the pressure-sensitive adhesive is suppressed, and good bending recovery is easily obtained. In addition, even when the reinforcing film is held in a bent state for a long time, it is easy to exhibit a holding force that does not cause peeling from the adherend. Furthermore, the increase in adhesive force is also likely to be in a suitable range. The 80°C tan δ ₈₀ may be 0.55 or less. In some other embodiments, the 80°C tan δ ₈₀ may be 0.50 or less, or may be 0.35 or less.

The 23°C bulk modulus _G'23 , 80°C bulk modulus _G'80 and 80°C tan _δ80 of the pressure-sensitive adhesive layer can be adjusted by the type and characteristics (molecular weight, glass transition temperature, molecular structure, etc.) of polymer (A), the type (chemical structure, etc.) and characteristics (molecular weight, glass transition temperature, etc.) and amount used of polymer (B), and the type and amount used of crosslinking agent, etc. The 23°C bulk modulus _G'23 , 80°C bulk modulus _G'80 and 80°C tan _δ80 of the pressure-sensitive adhesive layer are measured by the method described in the Examples below.

(Polymer (A))
As the polymer (A), one or more of various 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, known in the field of pressure-sensitive adhesives, can be used. In the reinforcing film disclosed herein, the polymer (A) is typically the main component of the polymer components contained in the pressure-sensitive adhesive layer, i.e., a component that occupies more than 50% by weight, and may be a component that occupies 75% by weight or more of the above polymer components. In some embodiments, the polymer (A) is a component that occupies more than 50% by weight of the entire pressure-sensitive adhesive layer, and may be a component that occupies 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more (e.g., 97% by weight or more).

The glass transition temperature T _A of the polymer (A) is not particularly limited and can be selected so as to obtain preferred properties in the reinforcing film disclosed herein. In some embodiments, a polymer (A) having a T _A of less than 0°C can be preferably used. Since a pressure-sensitive adhesive containing such a polymer (A) exhibits moderate fluidity (e.g., mobility of the polymer chain contained in the pressure-sensitive adhesive), it is suitable for realizing a reinforcing film whose adhesive strength increases to a predetermined value or more upon heating. The reinforcing film disclosed herein can be preferably implemented using a polymer (A) having a T _A of less than -10°C, less than -20°C, less than -30°C, or less than -35°C. In some embodiments, T _A may be less than -40°C or less than -50°C. In some preferred embodiments, T _A is less than -55°C, more preferably less than -58°C, even more preferably less than -62°C, and may be less than -65°C (e.g. less than -66°C). The lower limit of T _A is not particularly limited. From the viewpoint of material availability and improving the cohesive strength of the pressure-sensitive adhesive layer, it is usually preferable to use a polymer (A) having a _T of −80° C. or higher, −70° C. or higher. In some embodiments, the _T may be, for example, −63° C. or higher, −55° C. or higher, −50° C. or higher, or −45° C. or higher.

In this specification, the glass transition temperature (Tg) of polymers including polymer (A) and polymer (B) described later refers to a nominal value described in literature, catalogs, etc., or a Tg calculated by Fox's formula based on the composition of the monomer raw materials used in the preparation of the polymer. The Fox formula, as shown below, 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.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature (unit: K) of a 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 to calculate Tg should be a value listed in a publicly available document. Specifically, the values are listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values are listed in the Polymer Handbook, the highest value is used.

As the glass transition temperature of a homopolymer of a monomer not described in the Polymer Handbook, a value obtained by the following measurement method is used.
Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser tube, and stirred for 1 hour while passing nitrogen gas through. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Then, the homopolymer solution is cast and applied onto a release liner, and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. This test sample was punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity was measured in a shear mode at a temperature range of −70° C. to 150° C. and a heating rate of 5° C./min while applying a shear strain of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES"), and the temperature corresponding to the peak top temperature of tan δ was taken as the Tg of the homopolymer.

Although not particularly limited, the weight average molecular weight (Mw) of the polymer (A) is usually about 20×10 ⁴ or more. With the polymer (A) having such Mw, a pressure-sensitive adhesive exhibiting good cohesiveness is easily obtained. From the viewpoint of obtaining a higher cohesive force, in some preferred embodiments, the Mw of the polymer (A) may be, for example, 30×10 ⁴ or more, 40×10 ⁴ or more, 50×10 ⁴ or more, 60×10 ⁴ or more, or 80×10 ⁴ or more. In addition, the Mw of the polymer (A) is usually about 500×10 ⁴ or less. Since the polymer (A) having such Mw is easy to form a pressure-sensitive adhesive exhibiting moderate fluidity (mobility of polymer chains), it is suitable for realizing a reinforcing film having low initial adhesion and large increase in adhesion. It is also preferable that the Mw of the polymer (A) is not too high from the viewpoint of improving compatibility with the polymer (B). In some preferred embodiments, the Mw of the polymer (A) may be, for example, 250×10 ⁴ or less, 200×10 ⁴ or less, 150×10 ⁴ or less, 100×10 ⁴ or less, or 70×10 ⁴ or less.

In this specification, the Mw of polymer (A) and polymer (B) described later can be determined in terms of polystyrene by gel permeation chromatography (GPC). More specifically, the Mw can be measured according to the method and conditions described in the examples described later.

As the polymer (A) in the reinforcing film disclosed herein, an acrylic polymer can be preferably used. When an acrylic polymer is used as the polymer (A), good compatibility with the polymer (B) tends to be easily obtained. Good compatibility between the polymer (A) and the polymer (B) is preferable because it can contribute to reducing the initial adhesive strength and improving the adhesive strength after heating through improving the mobility of the polymer (B) in the adhesive layer. In addition, acrylic polymers, which have a high degree of freedom in molecular design, are suitable as adhesive materials that can improve adhesive properties, flex recovery, and flex retention in a balanced manner.

The acrylic polymer may be, for example, a polymer containing 50% by weight or more of monomer units derived from (meth)acrylic acid alkyl ester, that is, a polymer in which 50% by weight or more of the total amount of the monomer components (monomer raw material A) for preparing the acrylic polymer is (meth)acrylic acid alkyl ester. As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms (i.e., C _1-20 ) may be preferably used. Since it is easy to balance the properties, the proportion of (meth)acrylic acid C _1-20 alkyl ester in the monomer raw material A may be, for example, 50% by weight or more, or may be 60% by weight or more. In some preferred embodiments, the proportion of (meth)acrylic acid C _1-20 alkyl ester in the monomer raw material A is 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more. By using an acrylic polymer with such a monomer composition, it is easy to obtain a pressure-sensitive adhesive that balances the increase in adhesive strength with bending recovery and bending retention. The proportion of the C _1-20 alkyl (meth)acrylic acid ester in the monomer raw material A may be, for example, 99.9% by weight or less, 98% by weight or less, or 95% by weight or less. In some embodiments, the proportion of the C _1-20 alkyl (meth)acrylic acid ester in the monomer raw material A may be, for example, 90% by weight or less, 85% by weight or less, or 80% by weight or less.

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 _1-18 alkyl ester, and it is more preferable to use at least a (meth)acrylic acid C _1-14 alkyl ester. In some embodiments, the acrylic polymer may contain at least one selected from a (meth)acrylic acid C _4-12 alkyl ester (preferably an acrylic acid C _4-10 alkyl ester, for example an acrylic acid C _6-10 alkyl ester) as a monomer unit. For example, an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) is preferable, and an acrylic polymer containing at least 2EHA is particularly preferable.

In some preferred embodiments, the proportion of the _C6-10 alkyl acrylate (preferably a _C8-9 alkyl acrylate, typically 2EHA) in the monomer raw material A for preparing the acrylic polymer is 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more. An acrylic polymer having such a monomer composition is particularly suitable for achieving the effects of the technology disclosed herein. In addition, the proportion of the _C6-10 alkyl acrylate (preferably a _C8-9 alkyl acrylate, typically 2EHA) in the monomer raw material A may be, for example, 99.9% by weight or less, and from the viewpoints of initial low adhesion, flex recovery, and the like, may be 98% by weight or less, or may be 95% by weight or less.

In some preferred embodiments, it is preferable that the proportion of (meth)acrylic acid _C1-3 alkyl ester (e.g., (meth)acrylic acid _C1 alkyl ester, typically methyl methacrylate (MMA)) is limited in the monomer raw material A for preparing the acrylic polymer. (Meth)acrylic acid _C1-3 alkyl ester (e.g., (meth)acrylic acid _C1 alkyl ester, typically MMA) tends to have a relatively high Tg, and a pressure-sensitive adhesive containing an acrylic polymer using the above monomer component tends to have high cohesiveness. By limiting the amount of (meth)acrylic acid _C1-3 alkyl ester used, the cohesive strength of the pressure-sensitive adhesive can be appropriately reduced, and an elastic modulus (typically a surface elastic modulus) suitable for achieving both bending retention and increased adhesive strength can be preferably realized. From such a viewpoint, the proportion of the (meth)acrylic acid _C1-3 alkyl ester (for example, (meth)acrylic acid _C1 alkyl ester, typically MMA) in the above-mentioned monomer raw material A is suitably 8% by weight or less, preferably 6% by weight or less, more preferably 3% by weight or less, and further preferably 1% by weight or less (for example, 0 to 0.3% by weight).

The monomer raw material A may contain, as the main component, an alkyl (meth)acrylate ester, and, if necessary, other monomers (copolymerizable monomers) that are copolymerizable with the alkyl (meth)acrylate ester. As the copolymerizable monomer, a monomer having a polar group (e.g., a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) can be suitably used. The monomer having a polar group can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the acrylic polymer. The copolymerizable monomers can be used alone or in combination of two or more.

Non-limiting examples of copolymerizable monomers include the following:
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 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-(meth)acryloylmorpholine, 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, monomers having a succinimide skeleton, such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyhexamethylene succinimide;
Maleimides, such as, for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, and the like; and
For example, itaconimides such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide.
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.
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-(meth)acrylamide, 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.
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 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 such as methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (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.
(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and the like.
(Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and the like.
Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene, etc.
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 is not particularly limited, but it is usually appropriate to set it to 0.01% by weight or more of the monomer raw material A. 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 monomer raw material A, or may be 1% by weight or more. In some preferred embodiments, the content of the copolymerizable monomer in the monomer raw material A is 3% by weight or more, more preferably 5% by weight or more, and even more preferably 7% by weight or more (e.g., 8% by weight or more). The more the amount of the copolymerizable monomer used, the higher the cohesiveness and the more the bending recovery tend to improve. In addition, the amount of the copolymerizable monomer used can be 50% by weight or less of the monomer raw material A, and preferably 30% by weight or less. This prevents the cohesive force of the adhesive from becoming too high, and can improve the tackiness at room temperature (25 ° C.). In some preferred embodiments, the amount of the copolymerizable monomer used is 20% by weight or less of the monomer raw material A, more preferably 15% by weight or less (e.g., 12% by weight or less), and may be 10% by weight or less. By limiting the amount of copolymerizable monomer used, the cohesive strength of the adhesive is reduced, the modulus of elasticity (typically the surface modulus of elasticity) falls within a suitable range, making it easier to obtain excellent bending retention and increase adhesive strength.

In some embodiments, the monomer raw material A may contain a monomer having a nitrogen atom-containing ring. By using a monomer having a nitrogen atom-containing ring, the cohesive strength and polarity of the adhesive can be adjusted, and the adhesive strength after heating can be suitably improved. By including a monomer having a nitrogen atom-containing ring in the monomer raw material A, the compatibility between the polymer (A) formed from the monomer raw material A and the polymer (B) tends to be improved. This makes it easier to obtain a reinforcing film whose adhesive strength can be greatly increased by heating.

The monomer having a nitrogen atom-containing ring can be appropriately selected from the above examples, and can be used alone or in combination of two or more. In some embodiments, it is preferable that the monomer raw material A contains at least one monomer selected from the group consisting of N-vinyl cyclic amides and cyclic amides having a (meth)acryloyl group as the monomer having a nitrogen atom-containing ring.

Specific examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. Particularly preferred are N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactam.
Specific examples of cyclic amides having a (meth)acryloyl group include N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, etc. A suitable example is N-acryloylmorpholine (ACMO).

The amount of the monomer having a nitrogen atom-containing ring is not particularly limited, and is usually 40% by weight or less of the monomer raw material A, and may be 30% by weight or less, 20% by weight or less, or 10% by weight or less. In some preferred embodiments, from the viewpoint of lowering the cohesive strength and lowering the elastic modulus (typically the surface elastic modulus), the content of the monomer having a nitrogen atom-containing ring in the monomer raw material A is 7% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less (e.g., 1.5% by weight or less). In addition, the amount of the monomer having a nitrogen atom-containing ring is usually 0.01% by weight or more of the monomer raw material A (preferably 0.1% by weight or more, for example 0.5% by weight or more). From the viewpoint of obtaining a moderate cohesive strength and elastic modulus, in some embodiments, the amount of the monomer having a nitrogen atom-containing ring may be 0.8% by weight or more of the monomer raw material A, and may be 1.0% by weight or more.

In some preferred embodiments, the monomer raw material A includes a hydroxyl group-containing monomer. The use of a hydroxyl group-containing monomer can adjust the cohesive strength and polarity of the adhesive, and thus the elastic modulus (typically the surface elastic modulus), thereby enabling the effects of the technology disclosed herein to be preferably realized. In addition, the hydroxyl group-containing monomer provides a reaction site with a crosslinking agent (e.g., an isocyanate-based crosslinking agent) described below, and can increase the cohesive strength of the adhesive through a crosslinking reaction.

As hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, N-(2-hydroxyethyl)(meth)acrylamide, etc. can be suitably used. Among them, preferred examples include 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA), and N-(2-hydroxyethyl)acrylamide (HEAA). From the viewpoint of obtaining a cohesive force suitable for bending recovery and bending retention, 4HBA is particularly preferred.

The amount of the hydroxyl group-containing monomer used is not particularly limited, and is usually appropriate to be 40% by weight or less of the monomer raw material A, may be 30% by weight or less, or may be 20% by weight or less. In some preferred embodiments, from the viewpoint of reducing the cohesive force and thus the elastic modulus (typically the surface elastic modulus), the content of the hydroxyl group-containing monomer in the monomer raw material A is 15% by weight or less, more preferably 12% by weight or less (e.g., 10% by weight or less). By limiting the amount of the hydroxyl group-containing monomer used, the mobility of the polymer (B) in the adhesive layer is improved, and it is easy to realize an increase in adhesive strength. In some other embodiments, the content of the hydroxyl group-containing monomer may be 5% by weight or less of the monomer raw material A. In addition, it is appropriate to use the hydroxyl group-containing monomer in an amount of 0.01% by weight or more of the monomer raw material A (preferably 0.1% by weight or more, for example 0.5% by weight or more). From the viewpoint of obtaining an appropriate cohesive strength and elastic modulus, in some preferred embodiments, the amount of the hydroxyl group-containing monomer used is 1% by weight or more of the monomer raw material A, more preferably 3% by weight or more, even more preferably 5% by weight or more, and particularly preferably 7% by weight or more (e.g., 8% by weight or more).

In some embodiments, a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer can be used in combination as a copolymerizable monomer. In this case, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 0.1% by weight or more of the monomer raw material A, preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, particularly preferably 7% by weight or more (e.g., 9% by weight or more), and may be 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more. In addition, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 50% by weight or less of the monomer raw material A, and preferably 30% by weight or less. In some preferred embodiments, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer is 20% by weight or less of the monomer raw material A, more preferably 15% by weight or less (e.g., 12% by weight or less).

In an embodiment in which the monomer raw material A contains a combination of a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer, the relationship (weight basis) between the content of the monomer having a nitrogen atom-containing ring ( _WN ) and the content of the hydroxyl group-containing monomer ( _WOH ) in the monomer raw material A is not particularly limited. _WN / _WOH may be, for example, 0.01 or more, and usually 0.05 or more is appropriate, and may be 0.10 or more, or 0.12 or more. In addition, _WN / _WOH may be, for example, 10 or less, and usually 1 or less is appropriate, and is preferably 0.50 or less, 0.30 or less, 0.20 or less, or 0.15 or less.

In some embodiments, it is preferable that monomer raw material A does not contain a monomer (monomer S1) having a polyorganosiloxane skeleton, which is preferably used as a component of monomer raw material B described later, or that the content of the monomer is less than 10% by weight (more preferably less than 5% by weight, for example less than 2% by weight) of monomer raw material A. With monomer raw material A of such a composition, a reinforcing film that preferably achieves both initial reworkability and strong adhesion after the adhesive strength increases can be preferably realized. For the same reason, in some other embodiments, it is preferable that monomer raw material A does not contain monomer S1, or if it contains monomer S1, its content (by weight) is lower than the content of monomer S1 in monomer raw material B.

The method for obtaining polymer (A) is not particularly limited, and various polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately adopted. In some embodiments, the solution polymerization method can be preferably adopted. The polymerization temperature when carrying out solution polymerization can be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

The initiator used for polymerization can be appropriately selected from conventionally known thermal polymerization initiators, photopolymerization initiators, etc., depending on the polymerization method. The polymerization initiator can be used alone or in combination of two or more kinds.

Examples of the thermal polymerization initiator include azo-based polymerization initiators (e.g., 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2 -imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride, etc.; persulfates such as potassium persulfate; peroxide-based polymerization initiators (e.g., dibenzoyl peroxide, t-butyl permaleate, lauroyl peroxide, etc.); redox-based polymerization initiators, etc. The amount of the thermal polymerization initiator used is not particularly limited, but can be, for example, within the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the monomer component (monomer raw material A) used in the preparation of the acrylic polymer.

The photopolymerization initiator is not particularly limited, but for example, a benzoin ether-based photopolymerization initiator, an acetophenone-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 ketal-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, etc. can be used. The amount of the photopolymerization initiator used is not particularly limited, but for example, it can be in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the monomer raw material A.

In some embodiments, the polymer (A) may be included in the adhesive composition for forming the adhesive layer in the form of a partial polymer (polymer syrup) obtained by irradiating a mixture of the monomer raw material A and a polymerization initiator with ultraviolet (UV) light to polymerize a part of the monomer component. The adhesive composition containing such a polymer syrup can be applied to a predetermined substrate and irradiated with ultraviolet light to complete the polymerization. In other words, the polymer syrup can be regarded as a precursor of the polymer (A). The adhesive layer disclosed herein can be formed, for example, using an adhesive composition containing the polymer syrup and polymer (B).

(Polymer (B))
The polymer (B) in the technology disclosed herein is a polymer of a monomer component (monomer raw material B) containing a monomer having a polyorganosiloxane skeleton (hereinafter also referred to as "monomer S1") and a (meth)acrylic monomer. The polymer (B) can be said to be a copolymer of the monomer S1 and a (meth)acrylic monomer. The polymer (B) can be used alone or in combination of two or more types. The polymer (B) can function as an adhesive strength increase retarder that suppresses the adhesive strength at the initial stage of application to the adherend due to the low polarity and mobility of the polyorganosiloxane structure derived from the monomer S1, and increases the adhesive strength to the adherend by heating. The monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. The monomer S1 promotes uneven distribution of the polymer (B) on the surface of the adhesive layer in the reinforcing film before use (before application to the adherend) due to the low polarity derived from its structure, and exhibits light peelability (low adhesion) at the initial stage of application. As the monomer S1, a structure having a polymerizable reactive group at one end can be preferably used. According to a configuration including such a monomer S1 unit and a (meth)acrylic monomer unit, a polymer (B) having a polyorganosiloxane skeleton in the side chain is formed. The polymer (B) having such a structure is likely to have a low initial adhesive strength and a high adhesive strength after heating due to the mobility and ease of movement of the side chain. In addition, in some embodiments, as the monomer S1, a monomer having a polymerizable reactive group at one end and not having a functional group that causes a crosslinking reaction with the polymer (A) at the other end can be preferably used. The polymer (B) in which the monomer S1 having such a structure is copolymerized is likely to have a low initial adhesive strength and a high adhesive strength after heating due to the mobility of the polyorganosiloxane structure derived from the monomer S1.

ここで、上記一般式（１），（２）中のＲ^３は水素またはメチルであり、Ｒ^４はメチル基または１価の有機基であり、ｍおよびｎは０以上の整数である。 As the monomer S1, for example, a compound represented by the following general formula (1) or (2) can be used. More specifically, examples of the one-end reactive silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. include X-22-174ASX, X-22-2426, X-22-2475, and KF-2012. The monomer S1 can be used alone or in combination of two or more kinds.

Here, in the above general formulas (1) and (2), ^R3 is hydrogen or methyl, ^R4 is a methyl group or a monovalent organic group, and m and n are integers of 0 or more.

The functional group equivalent of monomer S1 can be an appropriate value within a range in which the desired effect is achieved using monomer S1, and is not limited to a specific range. From the viewpoint of sufficiently suppressing the initial adhesive strength, the functional group equivalent is, for example, 100 g/mol or more, or 200 g/mol or more, and is preferably 300 g/mol or more (for example, 500 g/mol or more), and is preferably 800 g/mol or more, and more preferably 1500 g/mol or more. In a particularly preferred embodiment, from the viewpoint of achieving both low adhesive strength at the initial stage of application and increased adhesive strength after heating, the functional group equivalent is 2000 g/mol or more, and more preferably 2500 g/mol or more, and may be 3000 g/mol or more, 4000 g/mol or more, or 5000 g/mol or more. In some other embodiments, the functional group equivalent weight may be 9000 g/mol or more, 12000 g/mol or more, or 15000 g/mol or more.

From the viewpoint of sufficiently increasing the adhesive strength, the functional group equivalent is, for example, suitably 30,000 g/mol or less, may be 20,000 g/mol or less, may be less than 15,000 g/mol, or may be less than 10,000 g/mol. In some preferred embodiments, the functional group equivalent of monomer S1 is 7,000 g/mol or less, more preferably 5,500 g/mol or less, even more preferably 4,500 g/mol or less, may be 4,200 g/mol or less, or may be 3,500 g/mol or less. When the functional group equivalent of monomer S1 is within the above range, compatibility (e.g., compatibility with the base polymer) in the adhesive layer is likely to be good, the mobility of the polyorganosiloxane skeleton (chain) of polymer (B) is good, and the mobility of polymer (B) can be easily adjusted to an appropriate range, making it easier to realize an adhesive layer that achieves both initial low adhesion and increased adhesive strength after heating.

Here, the term "functional group equivalent" refers to the weight of the main skeleton (e.g., polydimethylsiloxane) bonded to one functional group. The unit g/mol is calculated based on 1 mol of functional group. The functional group equivalent of the monomer S1 can be calculated, for example, from the spectrum intensity of ¹ H-NMR (proton NMR) based on nuclear magnetic resonance (NMR). The calculation of the functional group equivalent (g/mol) of the monomer S1 based on the spectrum intensity of ¹ H-NMR can be performed based on a general structural analysis method related to ¹ H-NMR spectrum analysis, with reference to the description of Japanese Patent No. 5951153 if necessary. In the functional group equivalent of the monomer S1, the functional group refers to a polymerizable functional group (e.g., an ethylenically unsaturated group such as a (meth)acryloyl group, a vinyl group, or an allyl group).

When two or more monomers having different functional group equivalents are used as _the monomer S1 _, the functional group equivalent of _the monomer S1 can be calculated by the following formula:
Functional group equivalent of monomer S1 (g/mol)=(functional group equivalent of monomer _S11 ×amount of monomer _S11 +functional group equivalent of monomer _S12 ×amount of monomer _{S12+...+functional group equivalent of monomer S1n ×} amount of monomer _S1n )/(amount of monomer S11+amount of _{monomer S12 +} ...+amount of monomer _S1n )

The content of monomer S1 can be an appropriate value within a range in which the desired effect is achieved using the monomer S1, and is not limited to a specific range. From the viewpoint of sufficiently suppressing the initial adhesive strength, in some embodiments, the content of monomer S1 in the total amount of monomer components (monomer raw material B) for preparing polymer (B) may be, for example, 5% by weight or more, and from the viewpoint of better exerting the effect as an adhesive strength increase retarder, it is preferably 10% by weight or more, more preferably 12% by weight or more, even more preferably 15% by weight or more, particularly preferably 18% by weight or more, and may be 20% by weight or more. In addition, from the viewpoint of polymerization reactivity and compatibility, the content of monomer S1 in monomer raw material B may be, for example, 80% by weight or less, and it is appropriate to set it to 60% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. By setting the polymerization ratio of monomer S1 within an appropriate range, the increase in adhesive strength can be suitably expressed.

In addition to monomer S1, monomer raw material B contains a (meth)acrylic monomer that is copolymerizable with monomer S1. By using one or more (meth)acrylic monomers, the mobility of polymer (B) within the adhesive layer can be suitably adjusted. It can also be useful for improving the compatibility between polymer (B) and polymer (A). Polymer (B) containing a (meth)acrylic monomer unit can be well compatible with acrylic polymers, and therefore, by improving the mobility of polymer (B) within the adhesive layer, it is easy to reduce the initial adhesive strength and improve the adhesive strength after heating.

In the polymer (B) used in the technology disclosed herein, the composition of the (meth)acrylic monomer contained in the monomer raw material B is preferably set so that the glass transition temperature T _B1 based on the composition of the (meth)acrylic monomer is higher than the glass transition temperature T _A of the polymer (A). T _B1 can be set, for example, to be higher than 0°C. Here, the glass transition temperature T _B1 based on the composition of the (meth)acrylic monomer refers to Tg calculated by the Fox formula based on the composition of only the (meth)acrylic monomer among the monomer components used in the preparation of the polymer (B). T _B1 can be calculated from the glass transition temperature of the homopolymer of each (meth)acrylic monomer and the weight fraction of each (meth)acrylic monomer in the total amount of the (meth)acrylic monomer by applying the above-mentioned Fox formula to only the (meth)acrylic monomer among the monomer components used in the preparation of the polymer (B). Polymer (B) having a relatively high glass transition temperature T _B1 (typically higher than 0° C.) tends to suppress the initial adhesive strength. Also, polymer (B) having a relatively high glass transition temperature T _B1 (typically higher than 0° C.) tends to provide a reinforcing film having a large adhesive strength increase ratio.

In some preferred embodiments, T _B1 is 10° C. or higher, more preferably 30° C. or higher, and even more preferably 40° C. or higher, and may be 45° C. or higher. When T _B1 is higher, the adhesive strength at the initial stage of application generally tends to be better suppressed. This is because, according to the polymer (B) having T _B1 at or above a predetermined temperature, the improvement in the mobility and mobility of the polyorganosiloxane structural portion accompanying the temperature rise to room temperature or a region somewhat higher than room temperature is effectively suppressed by the monomer unit derived from the (meth)acrylic monomer contained in the polymer (B), and the low adhesiveness due to the presence of the polyorganosiloxane structural portion can be better maintained. From the viewpoint of more stably maintaining the low adhesiveness at the initial stage of application, in some embodiments, T _B1 may be, for example, 50° C. or higher, 55° C. or higher, or 60° C. or higher. In addition, T _B1 may be, for example, 120° C. or lower, or 100° C. or lower. When T _B1 is lower, the adhesive strength tends to increase more easily due to heating. In some preferred embodiments, T _B1 is, for example, 90° C. or less, more preferably 70° C. or less, even more preferably 60° C. or less, and particularly preferably 55° C. or less (for example, 50° C. or less).

From the viewpoint of making it easier to exert the effect of appropriately setting T _B1 , the total amount of the monomer S1 and the (meth)acrylic monomer in all the monomer components for preparing the polymer (B) may be, for example, 50% by weight or more, 70% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or may be substantially 100% by weight.

The glass transition temperature T _B of the polymer (B) is not particularly limited and can be selected so as to obtain preferred properties in the reinforcing film disclosed herein. The T _B of the polymer (B) may be, for example, less than 50°C, 30°C or less, 20°C or less, 15°C or less, or 10°C or less. When the T _B of the polymer (B) is low, the mobility (typically temperature-sensitive mobility) of the polymer (B) is improved, and the adhesive strength can be greatly increased. In some preferred embodiments, the T _B of the polymer (B) is 5°C or less, less than 0°C, -5°C or less, or -10°C or less. In some embodiments, the T _B of the polymer (B) may be, for example, -40°C or more, or -30°C or more. The higher the T _B , the more the polymer (B) unevenly distributed on the surface side of the pressure-sensitive adhesive layer when attached to the adherend contributes to a decrease in initial adhesive strength, and the easier peeling property at the initial stage of attachment tends to be excellent. In some preferred embodiments, the T _B of the polymer (B) is −20° C. or higher, and may be −15° C. or higher. By setting the T _B in an appropriate range, it is possible to control the easy peelability at the initial stage of application and the increase in adhesive strength after heating within preferred ranges.

In some embodiments, the composition of the monomer components for preparing the polymer (B) can be set so that T _B1 is higher than T _B , that is, T _B1 -T _B is greater than 0°C. With such a composition, the effect of adjusting the mobility of the polymer (B) by the composition of the (meth)acrylic monomer contained in the monomer components is easily exhibited. T _B1 -T _B may be, for example, about 40°C to 100°C, or about 50°C to 90°C. In some preferred embodiments, T _B1 -T _B is 45°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher (e.g., 58°C or higher). In addition, from the viewpoint of suitably exhibiting the effect of containing the polymer (B), T _B1 -T _B is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower (e.g., 62°C or lower).

From the viewpoint of easily controlling the mobility of the polymer (B) in the pressure-sensitive adhesive layer, in some embodiments, the composition of the monomer components for preparing the polymer (B) can be set in relation to the glass transition temperature TA of the polymer ( _A ) so that _TB is 20° C. or more higher than _TA , that is, _{TB -TA} is 20° C. or more. In some preferred embodiments, _TB -TA _is , for example, 30° C. or more, more preferably 40° C. or more, even more preferably 50° C. or more, and may be 60° C. or more or may be 70° C. or more. In addition, from the viewpoint of increasing the adhesive strength, _{TB -TA} may be, for example, 130° C. or less, or 120° C. or less, preferably 100° C. or less, more preferably 80° C. or less, even more preferably 65° C. or less, may be 55° C. or less, or may be 45° C. or less.

Examples of (meth)acrylic monomers that can be used for monomer feedstock B include (meth)acrylic acid alkyl esters. The term "alkyl" as used herein refers to a chain-like (including linear and branched) alkyl (group) and does not include the alicyclic hydrocarbon group described below. For example, one or more of the monomers exemplified above as (meth)acrylic acid alkyl esters that can be used for polymer (A) can be used as components of monomer feedstock B. In some embodiments, monomer feedstock B can contain at least one type of (meth)acrylic acid C _4-12 alkyl ester (preferably (meth)acrylic acid C _4-10 alkyl ester, for example (meth)acrylic acid C _6-10 alkyl ester). In other embodiments, monomer feedstock B can contain at least one type of methacrylic acid C _1-18 alkyl ester (preferably methacrylic acid C _1-14 alkyl ester, for example methacrylic acid C _1-10 alkyl ester). Monomer raw material B may contain, as a (meth)acrylic monomer, for example, one or more selected from MMA, n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA).

Other examples of the (meth)acrylic monomer include (meth)acrylic acid esters having an alicyclic hydrocarbon group. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, etc. can be used. In some embodiments, the monomer raw material B may contain at least one selected from dicyclopentanyl methacrylate, isobornyl methacrylate, and cyclohexyl methacrylate as the (meth)acrylic monomer.

The content of the (meth)acrylic acid alkyl ester and the (meth)acrylic acid ester having the alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10% by weight or more and 95% by weight or less, 20% by weight or more and 95% by weight or less, 30% by weight or more and 90% by weight or less, 40% by weight or more and 90% by weight or less, or 50% by weight or more and 85% by weight or less. From the viewpoint of the ease of increasing the adhesive strength by heating, the use of the (meth)acrylic acid alkyl ester may be advantageous. In some embodiments, the content of the (meth)acrylic acid ester having the alicyclic hydrocarbon group may be less than 50% by weight, less than 30% by weight, less than 15% by weight, less than 10% by weight, or less than 5% by weight of the monomer raw material B. The (meth)acrylic acid ester having the alicyclic hydrocarbon group may not be used.

In some preferred embodiments, the (meth)acrylic monomer, which is a component of the monomer raw material B, may contain a monomer M2 having a homopolymer Tg of 50° C. or more. In the polymer (B), the mobility and movement of the polyorganosiloxane structure portion with increasing temperature are appropriately controlled by copolymerizing the monomer S1 and the monomer M2, and it is easy to achieve both initial easy peelability (reworkability) and increased adhesive strength after heating. In some embodiments, the Tg of the homopolymer of the monomer M2 may be 60° C. or more, 70° C. or more, 80° C. or more, or 90° C. or more. In addition, the upper limit of the Tg of the homopolymer of the monomer M2 is not particularly limited, but from the viewpoint of ease of synthesis of the polymer (B), it is usually appropriate that it is 200° C. or less. In some embodiments, the Tg of the homopolymer of the monomer M2 may be, for example, 180° C. or less, 150° C. or less, or 120° C. or less.

As the monomer M2, for example, from among the (meth)acrylic monomers exemplified above, one whose homopolymer Tg satisfies the conditions can be used. For example, one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid esters having an alicyclic hydrocarbon group can be used. As the (meth)acrylic acid alkyl ester, a methacrylic acid alkyl ester in which the number of carbon atoms in the alkyl group is in the range of 1 to 4 can be preferably used.

In an embodiment in which the monomer raw material B contains the monomer M2, the content of the monomer M2 may be, for example, 5% by weight or more of the monomer raw material B, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, or 30% by weight or more. In some embodiments, the content of the monomer M2 may be 35% by weight or more of the monomer raw material B, 40% by weight or more, 45% by weight or more, 50% by weight or more, or 55% by weight or more. The content of the monomer M2 may be, for example, 90% by weight or less, and is usually suitably 80% by weight or less, preferably 75% by weight or less, may be 70% by weight or less, or may be 65% by weight or less. In some preferred embodiments, the content of the monomer M2 is 60% by weight or less (for example, 50% by weight or less, typically 42% by weight or less). In polymer (B), the copolymerization ratio of monomer M2 with a Tg of 50° C. or higher is limited to a predetermined value or less, so that the adhesion strength after heating can be preferably increased based on the mobility of polymer (B) at around 50° C. From the same viewpoint, the content of monomer M2 in monomer raw material B may be 35% by weight or less, 25% by weight or less, or 15% by weight or less (for example, 5% by weight or less).

The content of the monomer M2 can be preferably applied, for example, to an embodiment in which the monomer M2 is composed of one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid esters having the alicyclic hydrocarbon group, or an embodiment in which the monomer M2 is composed of one or more monomers selected from (meth)acrylic acid alkyl esters (e.g., methacrylic acid alkyl esters). One preferred example of such an embodiment is an embodiment in which the monomer M2 is composed of MMA.

In some embodiments, the (meth)acrylic monomer may contain monomer M3, the homopolymer of which has a Tg of less than 50°C (typically -20°C or more and less than 50°C). The use of monomer M3 makes it easier to obtain a reinforcing film that has a good balance between adhesive strength and cohesive strength after the adhesive strength increases. From the viewpoint of making it easier to exert such effects, it is preferable to use monomer M3 in combination with monomer M2.

As the monomer M3, for example, one of the (meth)acrylic monomers exemplified above that satisfies the homopolymer Tg condition can be used. For example, one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters can be used.

In an embodiment in which monomer raw material B contains monomer M3, the content of monomer M3 may be, for example, 5% by weight or more of monomer raw material B, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, or 35% by weight or more. In addition, the content of monomer M3 is usually appropriate to be 70% by weight or less of monomer raw material B, and may be 60% by weight or less, or 50% by weight or less. The content of monomer M3 described above may be preferably applied, for example, to an embodiment in which monomer M3 is composed of one or more monomers selected from (meth)acrylic acid alkyl esters (e.g., methacrylic acid alkyl esters).

In some embodiments of the reinforcing film disclosed herein, the monomer raw material B preferably contains 30% by weight or less of a monomer having a homopolymer Tg of higher than 170°C. Here, unless otherwise specified, the concept of a monomer content of X% by weight or less in this specification includes an embodiment in which the content of the monomer is 0% by weight, that is, an embodiment in which the monomer is not substantially contained. Furthermore, "substantially not contained" means that the monomer is not used at least intentionally. If the copolymerization ratio of a monomer having a homopolymer Tg of higher than 170°C becomes high, the mobility of polymer (B) tends to be insufficient, and it may be difficult to increase the adhesive strength by heating to a temperature range higher than 50°C.

In some embodiments, it is preferable that the monomer raw material B contains at least MMA as a (meth)acrylic monomer. A polymer (B) in which MMA is copolymerized can easily produce a reinforcing film with high adhesive strength after heating. The proportion of MMA in the total amount of (meth)acrylic monomers contained in the monomer raw material B may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 40% by weight or more. In addition, the proportion of MMA in the total amount of the monomer raw material B is usually appropriate to be 95% by weight or less, and in some preferred embodiments, the proportion of MMA in the total amount of the monomer raw material B may be 75% by weight or less, 65% by weight or less, 60% by weight or less, or 55% by weight or less (for example, 50% by weight or less) from the viewpoint of increasing adhesive strength after heating.

Other examples of monomers that may be included together with monomer S1 as monomer units constituting polymer (B) include the carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, monomers having a nitrogen atom-containing ring (N-vinyl cyclic amides, cyclic amides having a (meth)acryloyl group, monomers having a succinimide skeleton, maleimides, itaconimides, etc.), aminoalkyl (meth)acrylates, vinyl esters, vinyl ethers, olefins, (meth)acrylic acid esters having an aromatic hydrocarbon group, heterocyclic ring-containing (meth)acrylates, halogen atom-containing (meth)acrylates, (meth)acrylic acid esters obtained from terpene compound derivative alcohols, etc., as exemplified above as monomers that may be used in polymer (A).

Further examples of monomers that may be included together with monomer S1 as monomer units constituting polymer (B) include oxyalkylene di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate; monomers having a polyoxyalkylene skeleton, such as polyethylene glycol and Polymerizable polyoxyalkylene ethers having a polymerizable functional group such as a (meth)acryloyl group, a vinyl group, an allyl group, etc. at one end of a polyoxyalkylene chain such as polypropylene glycol, and an ether structure (alkyl ether, aryl ether, aryl alkyl ether, etc.) at the other end; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxypropyl (meth)acrylate, etc.; salts such as alkali metal (meth)acrylates; trimethylol. Polyfunctional (meth)acrylates such as propane tri(meth)acrylic acid esters; halogenated vinyl compounds such as vinylidene chloride and 2-chloroethyl (meth)acrylate; oxazoline group-containing monomers such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline; aziridine group-containing monomers such as (meth)acryloylaziridine and 2-aziridinylethyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, lactones and 2-hydroxyethyl (meth)acrylate Examples of such monomers include hydroxyl group-containing vinyl monomers such as adducts of the above; fluorine-containing vinyl monomers such as fluorine-substituted (meth)acrylic acid alkyl esters; reactive halogen-containing vinyl monomers such as 2-chloroethyl vinyl ether and vinyl monochloroacetate; organosilicon-containing vinyl monomers such as vinyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, and 2-methoxyethoxytrimethoxysilane; and macromonomers having radically polymerizable vinyl groups at the monomer ends obtained by polymerizing vinyl groups. These monomers can be copolymerized with monomer S1 either alone or in combination of two or more.

In some embodiments, the polymer (B) may preferably be one that does not have a functional group that undergoes a crosslinking reaction with the polymer (A). In other words, the polymer (B) is preferably included in the adhesive layer in a form that is not chemically bonded to the polymer (A). An adhesive layer that includes the polymer (B) in such a form has good mobility of the polymer (B) when heated, and is suitable for improving the adhesive strength increase ratio. The functional group that undergoes a crosslinking reaction with the polymer (A) may vary depending on the type of functional group that the polymer (A) has, and may be, for example, an epoxy group, an isocyanate group, a carboxy group, an alkoxysilyl group, an amino group, etc.

The Mw of the polymer (B) used in the technology disclosed herein is in the range of 10,000 to 100,000. By having the Mw of the polymer (B) of 10,000 or more, the polymer (B) does not remain on the surface of the adhesive layer when heated, and exhibits an excellent increase in adhesive strength. The Mw of the polymer (B) is preferably 12,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, particularly preferably 22,000 or more, and most preferably 25,000 or more. In some other embodiments, the Mw of the polymer (B) may be 30,000 or more, 50,000 or more, or 70,000 or more. In addition, by using a polymer (B) with an Mw of 100,000 or less, the compatibility and mobility of the polymer (B) in the adhesive layer are adjusted to an appropriate range, and the light peelability at the initial stage of application is excellent. In some preferred embodiments, the Mw of the polymer (B) is preferably 80,000 or less, more preferably 60,000 or less, even more preferably 40,000 or less (e.g., 30,000 or less), and may be 25,000 or less, or may even be 20,000 or less. By setting the Mw of the polymer (B) within an appropriate range, it is possible to obtain an adhesive that is excellent in both easy peelability at the initial stage of application and increasing adhesive strength.

In some preferred embodiments, the Mw of the polymer (B) is preferably lower than the Mw of the polymer (A). This makes it easier to realize a reinforcing film that has both good reworkability at the initial stage of application and an increase in adhesive strength after heating. In some embodiments, the Mw of the polymer (B) may be, for example, 0.8 times or less, 0.75 times or less, 0.5 times or less, or 0.3 times or less of the Mw of the polymer (A). In some preferred embodiments, the ratio (Mw _B /Mw A ) of the Mw _B of the polymer (B) to the Mw _A of the polymer ( _A ) is 0.3 or less, more preferably 0.2 or less, even more preferably 0.1 or less, and particularly preferably 0.06 or less (e.g., 0.05 or less). In addition, the ratio (Mw _B /Mw _A ) is, for example, appropriately 0.010 or more, preferably 0.020 or more, more preferably 0.03 or more, and even more preferably 0.04 or more. The effects of the technology disclosed herein can be better realized by setting the Mw of polymer (A) and the Mw of polymer (B) in an appropriate range. In some other embodiments, the Mw of polymer (B) may be 0.03 times or less (e.g., 0.02 times or less) the Mw of polymer (A).

Polymer (B) can be prepared, for example, by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization.

In order to adjust the molecular weight of the polymer (B), a chain transfer agent can be used as necessary. Examples of the chain transfer agent to be used include compounds having a mercapto group, such as octyl mercaptan, lauryl mercaptan, t-nonyl mercaptan, t-dodecyl mercaptan, mercaptoethanol, and α-thioglycerol; thioglycolic acid esters, such as thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, thioglycolic acid ester of ethylene glycol, thioglycolic acid ester of neopentyl glycol, and thioglycolic acid ester of pentaerythritol; and α-methylstyrene dimer. The chain transfer agent can be used alone or in combination of two or more.

The amount of chain transfer agent used is not particularly limited, but typically, 0.05 to 20 parts by weight, preferably 0.1 to 15 parts by weight, and more preferably 0.2 to 10 parts by weight, of the chain transfer agent is contained per 100 parts by weight of the monomer. By adjusting the amount of the chain transfer agent added in this way, a polymer (B) with a suitable molecular weight can be obtained. In some preferred embodiments, the amount of the chain transfer agent used is 5 parts by weight or less, more preferably 1 part by weight or less, and even more preferably 0.8 parts by weight or less, per 100 parts by weight of the monomer.

As a means for adjusting the molecular weight of polymer (B), various conventionally known means, including the use of the chain transfer agent, can be used alone or in appropriate combination. The same applies to the molecular weight of polymer (A). Non-limiting examples of such means include selection of a polymerization method, selection of the type and amount of polymerization initiator used, selection of polymerization temperature, selection of the type and amount of polymerization solvent used in a solution polymerization method, selection of light irradiation intensity in a photopolymerization method, etc. A person skilled in the art would be able to understand how to obtain a polymer having a desired molecular weight based on the description of this application, including the specific examples described below, and the common general technical knowledge at the time of filing this application.

In the reinforcing film disclosed herein, the amount of polymer (B) used relative to 100 parts by weight of polymer (A) can be, for example, 0.1 parts by weight or more, and from the viewpoint of obtaining a higher effect (preferably, light peelability at the initial stage of application), 0.3 parts by weight or more is preferable, 0.5 parts by weight or more is more preferable, 0.8 parts by weight or more is even more preferable, and it may be 1.0 parts by weight or more. In some embodiments, from the viewpoint of improving reworkability, etc., the amount of polymer (B) used can be, for example, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more. In addition, the amount of polymer (B) used relative to 100 parts by weight of polymer (A) can be, for example, 75 parts by weight or less, 30 parts by weight or less, 10 parts by weight or less, or 8 parts by weight or less. From the viewpoint of suitably achieving the desired increase in adhesive strength, in some preferred embodiments, the amount of polymer (B) used per 100 parts by weight of polymer (A) is 5.0 parts by weight or less, more preferably 3.0 parts by weight or less, even more preferably 2.5 parts by weight or less, and particularly preferably 1.5 parts by weight or less (e.g., 1.2 parts by weight or less). By setting the amount of polymer (B) used within the above range, it is easy to achieve good bending recovery and bending retention, and it is possible to better balance light peelability at the initial stage of application and increased adhesive strength.

The adhesive layer may contain a polymer (optional polymer) other than polymer (A) and polymer (B) as necessary, to the extent that the performance of the reinforcing film disclosed herein is not significantly impaired. The amount of such optional polymer used is usually 20% by weight or less of the total polymer components contained in the adhesive layer, and may be 15% by weight or less, or 10% by weight or less. In some embodiments, the amount of the optional polymer used may be 5% by weight or less, 3% by weight or less, or 1% by weight or less of the total polymer components. The adhesive layer may be substantially free of polymers other than polymer (A) and polymer (B).

(Crosslinking Agent)
In the pressure-sensitive adhesive layer, a crosslinking agent may be used as necessary for the purpose of adjusting the cohesive force. As the crosslinking agent, a crosslinking agent known in the field of pressure-sensitive adhesives may be used, and examples thereof include epoxy-based crosslinking agents, isocyanate-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, and metal chelate-based crosslinking agents. Isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents can be preferably used. As a crosslinking agent that satisfies both bending recovery and bending retention, an isocyanate-based crosslinking agent can be preferably used. The crosslinking agent may be used alone or in combination of two or more types.

As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more types.

Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.
Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

A preferred example of a polyfunctional isocyanate is a polyfunctional isocyanate having an average of three or more isocyanate groups per molecule. Such a trifunctional or higher isocyanate may be a multimer (e.g., a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (e.g., an addition reaction product of a polyhydric alcohol and two or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples of such isocyanates include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimer adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, trimethylolpropane adducts of xylylene diisocyanate, trimethylolpropane adducts of isophorone diisocyanate, trimethylolpropane adducts of hexamethylene diisocyanate, polymethylene polyphenylisocyanate, polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, and polyfunctional isocyanates such as polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc.

Commercially available products of the above multifunctional isocyanates include "Duranate TPA-100" manufactured by Asahi Kasei Chemicals Corporation, "Coronate L", "Coronate HL", "Coronate HK", "Coronate HX", and "Coronate 2096" manufactured by Tosoh Corporation, and "Takenate D110N", "Takenate D120N", "Takenate D140N", and "Takenate D160N" manufactured by Mitsui Chemicals, Inc.

Epoxy crosslinking agents include bisphenol A, epichlorohydrin type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These can be used alone or in combination of two or more.

Metal chelate compounds include metal components such as aluminum, iron, tin, titanium, and nickel, and chelate components such as acetylene, methyl acetoacetate, and ethyl lactate. These can be used alone or in combination of two or more.

When a crosslinking agent is used, the amount used is not particularly limited, and can be, for example, an amount exceeding 0 parts by weight per 100 parts by weight of polymer (A). The amount of crosslinking agent used can be, for example, 0.01 parts by weight or more per 100 parts by weight of polymer (A), and is preferably 0.05 parts by weight or more. By increasing the amount of crosslinking agent used, the adhesive strength at the initial stage of application tends to be suppressed and reworkability tends to be improved. The bending recovery and processability tend to be excellent. In some embodiments, the amount of crosslinking agent used per 100 parts by weight of polymer (A) may be 0.1 parts by weight or more, 0.5 parts by weight or more, or 0.8 parts by weight or more. On the other hand, from the viewpoint of obtaining an increase in adhesive strength after heating while allowing the mobility of polymer (B) to an appropriate extent, the amount of crosslinking agent used per 100 parts by weight of polymer (A) is usually appropriate to be 15 parts by weight or less, may be 10 parts by weight or less, or may be 5 parts by weight or less.

The technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as a crosslinking agent. From the viewpoint of achieving both good reworkability at the initial stage of application and increased adhesive strength after heating, in some embodiments, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of polymer (A) can be, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0.07 parts by weight or more, and may be 0.10 parts by weight or more, or may be 0.15 parts by weight or more (for example, 0.20 parts by weight or more). By increasing the amount of isocyanate-based crosslinking agent used, moderate cohesive strength and elastic modulus are obtained, and bending recovery and processability tend to be excellent. In addition, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of polymer (A) can be, for example, 5 parts by weight or less, preferably less than 1.0 parts by weight, more preferably less than 0.5 parts by weight, even more preferably less than 0.3 parts by weight, and particularly preferably less than 0.2 parts by weight (for example, 0.15 parts by weight or less). This appropriately reduces the adhesive's cohesive strength and, therefore, its elastic modulus (typically, its surface elastic modulus), resulting in good bending retention and also making it easier to increase adhesive strength after heating.

Although not particularly limited, when an isocyanate-based crosslinking agent is used in a configuration in which the adhesive layer contains a hydroxyl group-containing monomer as a monomer unit, the molar ratio ([NCO]/[OH]) of the isocyanate group and the hydroxyl group contained in the adhesive layer can be, for example, 0.001 or more. In this way, by increasing the amount of the isocyanate-based crosslinking agent used relative to the hydroxyl group-containing monomer, the elastic modulus (typically the surface elastic modulus) of the adhesive becomes a suitable range, and the bending recovery tends to be improved. In addition, the processability also tends to be excellent. In some preferred embodiments, the molar ratio ([NCO]/[OH]) is 0.002 or more, more preferably 0.004 or more, even more preferably 0.006 or more (for example, 0.007 or more), and may be 0.010 or more, 0.020 or more, or 0.030 or more. In addition, the molar ratio ([NCO]/[OH]) can be, for example, 1.0 or less, or may be 0.10 or less. By limiting the molar ratio to a predetermined value or less, a crosslinked structure suitable for greatly increasing the adhesive strength after heating relative to the adhesive strength at the initial stage of application can be preferably formed. In some preferred embodiments, the molar ratio ([NCO]/[OH]) is 0.030 or less, more preferably 0.015 or less, even more preferably 0.012 or less (e.g., 0.009 or less), and may be 0.005 or less. In the adhesive layer, the isocyanate group and the hydroxyl group may exist in a state in which at least a portion of them are chemically bonded (crosslinked). More specifically, the isocyanate group may exist in a state in which they are chemically bonded (crosslinked) with the hydroxyl group. On the other hand, the hydroxyl group may exist in a state in which a portion of the hydroxyl group is chemically bonded with the isocyanate group, and another portion of the hydroxyl group is not chemically bonded (crosslinked) with the isocyanate group.

In some preferred embodiments, the adhesive layer contains a catalyst. The catalyst may be added for the purpose of promoting the curing of the adhesive layer during the formation of the adhesive layer, typically for the purpose of more effectively proceeding with any of the crosslinking reactions described above. Therefore, the catalyst is also called a curing catalyst or a crosslinking catalyst. By adding a catalyst, the initial curing is promoted and side reactions that cause the generation of bubbles on the surface of the adhesive layer can be suppressed. Examples of catalysts include organometallic compounds such as iron-based catalysts, tin-based catalysts, titanium-based catalysts, zirconium-based catalysts, lead-based catalysts, cobalt-based catalysts, and zinc-based catalysts, and tertiary amine compounds. These can be used alone or in combination of two or more. Among them, iron-based catalysts and tin-based catalysts are preferred from the perspective of the balance between reaction rate and pot life, and iron-based catalysts are particularly preferred.

Examples of iron-based catalysts include iron acetylacetonate and iron 2-ethylhexanoate. Iron-based catalysts can be used alone or in combination of two or more.

Examples of tin-based catalysts include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin methoxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate. Tin-based catalysts can be used alone or in combination of two or more.

The amount of catalyst used is not particularly limited, and can be, for example, 0.0001 parts by weight or more, preferably 0.001 parts by weight or more, more preferably 0.003 parts by weight or more, even more preferably 0.006 parts by weight or more, and particularly preferably 0.008 parts by weight or more, per 100 parts by weight of polymer (A). By using an appropriate amount of catalyst, the generation of bubbles from the adhesive layer is suppressed, and a smooth adhesive surface is easily obtained. In addition, the amount of catalyst used per 100 parts by weight of polymer (A) can be, for example, 1 part by weight or less, and may be 0.1 parts by weight or less. In some preferred embodiments, the amount of catalyst used per 100 parts by weight of polymer (A) is 0.03 parts by weight or less, more preferably 0.02 parts by weight or less, even more preferably 0.01 parts by weight or less, and may be 0.005 parts by weight or less. By appropriately limiting the content of catalyst per 100 parts by weight of polymer (A), it is easy to achieve a suitable increase in adhesive strength.

Although not particularly limited, when a catalyst is used in a configuration in which the adhesive layer contains a hydroxyl group-containing monomer as a monomer unit, the amount of catalyst used can be an amount such that the molar ratio of the catalyst and the hydroxyl group contained in the adhesive layer ([catalyst]/[OH]) is, for example, 1.0×10 ⁻⁶ or more, preferably 1.0×10 ⁻⁵ or more, more preferably 1.0×10 ⁻⁴ or more, even more preferably 2.0×10 ⁻⁴ or more, and particularly preferably 3.0×10 ⁻⁴ or more. By using an appropriate amount of catalyst, bubble generation from the adhesive layer is suppressed, and a smooth adhesive surface is easily obtained. In addition, the molar ratio ([catalyst]/[OH]) can be, for example, 5.0×10 ⁻² or less, and may be 5.0×10 ⁻³ or less. In some preferred embodiments, the molar ratio ([catalyst]/[OH]) is 3.0×10 ⁻³ or less, more preferably 1.0×10 ⁻³ or less, even more preferably 5.0×10 ⁻⁴ or less, and may be 3.0×10 ⁻⁴ or less. By appropriately limiting the catalyst content, it is easy to realize a suitable increase in adhesive strength.

(Tackifier resin)
The adhesive layer may contain a tackifier resin as required. The tackifier resin is not particularly limited, but may be, for example, a rosin-based tackifier resin, a terpene-based tackifier resin, a phenol-based tackifier resin, a hydrocarbon-based tackifier resin, a ketone-based tackifier resin, a polyamide-based tackifier resin, an epoxy-based tackifier resin, or an elastomer-based tackifier resin. The tackifier resin may be used alone or in combination of two or more.

The amount of the tackifier resin is not particularly limited, and can be set so that the adhesive performance is appropriate depending on the purpose and application. The amount of the tackifier resin (when two or more types of tackifier resins are included, the total amount of them) per 100 parts by weight of polymer (A) can be, for example, about 5 to 500 parts by weight. In addition, the technology disclosed herein can be preferably implemented in an embodiment in which the amount of the tackifier resin used is limited. For example, the amount of the tackifier resin per 100 parts by weight of polymer (A) can be less than 20 parts by weight, or less than 10 parts by weight, or less than 3 parts by weight, or less than 1 part by weight (0 parts by weight to less than 1 part by weight), and in some embodiments, the adhesive layer does not substantially contain a tackifier resin.

In addition, the adhesive layer in the technology disclosed herein may contain, as necessary, known additives that can be used in adhesives, such as leveling agents, plasticizers, softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, and preservatives, to the extent that the effects of the present invention are not significantly impeded.

The adhesive layer constituting the reinforcing film disclosed herein may be a cured layer of an adhesive composition. That is, the adhesive layer may be formed by applying (for example, coating) an adhesive composition such as a water-dispersed type, a solvent type, a photocurable type, or a hot melt type to a suitable surface, and then appropriately carrying out a curing treatment. When two or more types of curing treatments (drying, crosslinking, polymerization, cooling, etc.) are performed, these can be performed simultaneously or in multiple stages. In an adhesive composition using a partial polymer (polymer syrup) of a monomer raw material, typically, a final copolymerization reaction is performed as the curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, in the case of a photocurable adhesive composition, light irradiation is performed. If necessary, a curing treatment such as crosslinking or drying may be performed. For example, if a photocurable adhesive composition needs to be dried, it is recommended to perform photocuring after drying. In an adhesive composition using a complete polymer, typically, drying (heat drying), crosslinking, etc. are performed as the curing treatment as necessary.

The adhesive composition can be applied using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater.

The thickness of the adhesive layer is not particularly limited, and can be, for example, 6 μm or more. In some embodiments, the thickness of the adhesive layer may be 8 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more or more than 20 μm. The adhesive strength after heating tends to increase due to the increase in the thickness of the adhesive layer. In some embodiments, the thickness of the adhesive layer may be, for example, 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, or 40 μm or less. It may be advantageous for the thickness of the adhesive layer not to be too large in terms of thinning the reinforcing film and preventing cohesive failure of the adhesive layer. A reinforcing film having an adhesive layer with a thickness within the above-mentioned range can be well-balanced in adhesive properties such as adhesive strength, bending recovery, and bending retention. In addition, in the case of a reinforcing film having a first adhesive layer and a second adhesive layer on the first and second surfaces of a substrate, the thickness of the adhesive layer described above can be applied to at least the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from a similar range. In addition, in the case of a reinforcing film without a substrate, the thickness of the reinforcing film is the same as the thickness of the adhesive layer.

<Support substrate>
The reinforcing film according to some embodiments may be in the form of a substrate-attached adhesive sheet having an adhesive layer on one or both sides of the substrate. The material of the substrate is not particularly limited, and can be appropriately selected according to the purpose and mode of use of the reinforcing film. Non-limiting examples of substrates that can be used include resin films such as plastic films; foam sheets made of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven 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, semi-synthetic fibers such as acetate, etc.); 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 substrate may be a composite of these. Examples of such composite substrates include, for example, a substrate having a structure in which metal foil and the above-mentioned plastic film are laminated, and a plastic substrate reinforced with inorganic fibers such as glass cloth.

As the substrate of the reinforcing film disclosed herein, various film substrates can be preferably used. The film substrate may be a porous substrate such as a foam film or a nonwoven fabric sheet, or may be a nonporous substrate, or may be a substrate having a structure in which a porous layer and a nonporous layer are laminated. In some embodiments, the film substrate 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. As the resin film, one that can independently maintain its shape (self-supporting or independent) can be preferably used. The resin film may be a single-layer structure, or a multi-layer structure of two or more layers (for example, a three-layer structure).

Examples of resin materials that can be used to form the resin film include polyester, polyolefin, 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), fluororesins such as polytetrafluoroethylene (PTFE), acrylic resins, polyacrylate, polystyrene, polyvinyl chloride, and polyvinylidene chloride. The resin film may be formed using a resin material that contains only one of these resins, or may be formed using a resin material that is a blend of two or more of these resins. The resin film may be unstretched or stretched (for example, uniaxially or biaxially stretched).

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

Specific examples of polyester 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 base film of the reinforcing film disclosed herein include PI film, PET film, PEN film, PPS film, PEEK film, CPP film, and OPP film.

The resin film may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, as necessary, to the extent that the effects of the present invention are not significantly hindered. The amount of additives to be added is not particularly limited, and can be set appropriately depending on the purpose, 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 substrate may be substantially composed of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an optical property adjusting layer (e.g., a coloring layer, an anti-reflection layer), a printing layer or a lamination layer for imparting a desired appearance to the substrate, an antistatic layer, an undercoat layer, a release layer, and other surface treatment layers.

The thickness of the substrate is not particularly limited and may be selected according to the purpose and mode of use of the reinforcing film. The thickness of the substrate may be, for example, 1000 μm or less. In some embodiments, from the viewpoint of the handling and processability of the reinforcing film, the thickness of the substrate may be, for example, 500 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. From the viewpoint of miniaturization and weight reduction of the product to which the reinforcing film is applied, in some embodiments, the thickness of the substrate may be, for example, 160 μm or less, 130 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 60 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 substrate is reduced, the flexibility of the reinforcing film and its ability to follow the surface shape of the adherend tend to improve. In addition, from the viewpoint of handleability, processability, and the like, the thickness of the substrate may be, for example, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 25 μm or more, or more than 25 μm. In some embodiments, the thickness of the substrate may be, for example, 30 μm or more, 35 μm or more, 55 μm or more, 70 μm or more, 75 μm or more, 90 μm or more, or 120 μm or more. For example, a substrate having a thickness of 30 μm or more may be preferably used in a reinforcing film.

The first surface of the substrate may be subjected to a conventionally known surface treatment, such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, an acid treatment, an alkali treatment, or the formation of an undercoat layer by applying an undercoat agent (primer), as necessary. Such a surface treatment may be a treatment for improving the anchoring property of the adhesive layer to the substrate. For example, a substrate that has been subjected to such an anchoring property improvement treatment may be preferably used in a reinforcing film having a substrate that includes a resin film as a base film. The above surface treatments may be applied alone or in combination. The composition of the primer used to form the undercoat layer is not particularly limited, and may be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and preferably about 0.1 μm to 1 μm. Other treatments that may be applied to the first surface of the substrate as necessary include an antistatic layer formation treatment, a colored layer formation treatment, a printing treatment, etc.

When the reinforcing film disclosed herein is in the form of a single-sided pressure-sensitive adhesive sheet having an adhesive layer only on the first surface of the substrate, the second surface of the substrate may be subjected to a conventionally known surface treatment such as a release treatment or an antistatic treatment, if necessary. For example, by surface treating the back surface of the substrate with a release treatment agent (typically by providing a release layer made of a release treatment agent), the unwinding force of the reinforcing film wound in a roll shape can be reduced. As the release treatment agent, a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, an olefin-based release treatment agent, a fluorine-based release treatment agent, a fatty acid amide-based release treatment agent, molybdenum sulfide, silica powder, etc. can be used. In addition, for the purpose of improving printability, reducing light reflectivity, improving overlapping properties, etc., the second surface of the substrate may be subjected to a corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, etc. In addition, in the case of a double-sided pressure-sensitive adhesive sheet, the second surface of the substrate may be subjected to a surface treatment similar to those exemplified above as surface treatments that can be applied to the first surface of the substrate, if necessary. The surface treatment applied to the first surface of the substrate and the surface treatment applied to the second surface may be the same or different.

<Characteristics of the reinforcing film>
The reinforcing film disclosed herein is preferably limited to a predetermined value or less in initial adhesive strength N ₂₃ measured after laminating to a stainless steel plate and holding at 23 ° C. for 30 minutes. In some embodiments, the adhesive strength N ₂₃ is preferably less than 500 gf/25 mm, more preferably less than 400 gf/25 mm, even more preferably less than 300 gf/25 mm, particularly preferably 250 gf/25 mm or less (e.g., 200 gf/25 mm or less), and may be 150 gf/25 mm or less. A low adhesive strength N ₂₃ is preferable from the viewpoint of reworkability. The lower limit of the adhesive strength N ₂₃ is not particularly limited, and may be, for example, 1 gf/25 mm or more. From the viewpoint of the workability of attaching to the adherend and the prevention of positional deviation before the adhesive strength increases, it is usually appropriate that the adhesive strength N ₂₃ is 10 gf/25 mm or more. From the viewpoint of improving adhesive strength after heating, in some embodiments, the adhesive strength _N23 may be, for example, 20 gf/25 mm or more, 50 gf/25 mm or more, 80 gf/25 mm or more, or 100 gf/25 mm or more (e.g., 150 gf/25 mm or more).

The adhesive strength N ₂₃ [gf/25mm] is determined by pressing the film onto a stainless steel (SUS) plate as an adherend, leaving it in an environment of 23°C and 50% RH for 30 minutes, and then measuring the 180° peel adhesive strength in the same environment (i.e., at 23°C) under the conditions of a peel angle of 180° and a tensile speed of 300mm/min. SUS304BA plate is used as the adherend. In the measurement, if necessary, a suitable backing material (e.g., a PET film with a thickness of about 25 μm) can be attached to the reinforcing film to be measured to reinforce it. More specifically, the adhesive strength N ₂₃ can be measured according to the measurement method for initial adhesive strength described in the examples described later.

The reinforcing film disclosed herein has an adhesive strength that increases when heated, and may have an adhesive strength N ₆₀ of 300 gf/25 mm or more, i.e., an adhesive strength measured at 23 ° C after being attached to a stainless steel plate and held at 60 ° C for 60 minutes. In some embodiments, the adhesive strength N ₆₀ is 400 gf/25 mm or more, and preferably 500 gf/25 mm or more. A reinforcing film that satisfies this characteristic has an adhesive strength that increases to a predetermined value or more when heated after being attached to an adherend. According to the technology disclosed herein, it is possible to obtain a strong adhesive strength by heating. In some preferred embodiments, the adhesive strength N ₆₀ is 600 gf/25 mm or more, more preferably 700 gf/25 mm or more, and may be 800 gf/25 mm or more, or may be 900 gf/25 mm or more. There is no particular upper limit to the adhesive strength N ₆₀ . From the viewpoint of ease of production and economic efficiency of the reinforcing film, in some embodiments, the adhesive strength N ₆₀ may be, for example, 3000 gf/25 mm or less, 1500 gf/25 mm or less, or 1000 gf/25 mm or less.

The adhesive strength N ₆₀ [gf/25mm] is determined by pressing the film onto a SUS plate as an adherend, keeping it in an environment of 60°C for 60 minutes, then leaving it in an environment of 23°C and 50%RH for 30 minutes, and then measuring the 180° peel adhesive strength in the same environment under the conditions of a peel angle of 180° and a tensile speed of 300mm/min. As with the adhesive strength N ₂₃ , a SUS304BA plate is used as the adherend. In the measurement, if necessary, the reinforcing film to be measured can be reinforced by attaching an appropriate backing material (for example, a PET film with a thickness of about 25 μm). More specifically, the adhesive strength N ₆₀ can be measured according to the method for measuring adhesive strength after heating described in the examples described later.

The ratio of the adhesive strength N ₆₀ [gf/25mm] to the adhesive strength N ₂₃ [gf/25mm], i.e., the adhesive strength increase ratio N ₆₀ /N ₂₃ , is not particularly limited, and in some embodiments, N ₆₀ /N ₂₃ is suitably 1.5 or more, preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more (e.g. 3.5 or more), and may be more than 5.0 (e.g. more than 7.0). A reinforcing film with a large N ₆₀ /N ₂₃ exhibits good reworkability at the initial stage of attachment, and can greatly increase the adhesive strength by subsequent heating or the like. The upper limit of N ₆₀ /N ₂₃ is not particularly limited, and is usually 100 or less, and may be 30 or less, 15 or less, or 10 or less from the viewpoint of ease of production and economic efficiency of the reinforcing film. In some embodiments, N ₆₀ /N ₂₃ may be, for example, 5 or less, 3 or less, or 2 or less.

The adhesive strength of the reinforcing film disclosed herein after heating represents one characteristic of the reinforcing film, and does not limit the use of the reinforcing film. In other words, the use of the reinforcing film disclosed herein is not limited to the use of the reinforcing film at 60°C for 60 minutes, and can be used in a manner in which, for example, heating to room temperature (usually 20°C to 30°C, typically 23°C to 25°C) or higher is not performed. Even in such a use, the adhesive strength increases over the long term, and strong bonding can be achieved. In addition, the reinforcing film disclosed herein can be heated at a temperature of more than 30°C (for example, about 50 to 70°C) or higher than 60°C at any time after application to promote an increase in adhesive strength. The heating temperature in such a heat treatment is not particularly limited, and can be set in consideration of workability, economy, the heat resistance of the base material of the reinforcing film and the adherend, and the like. The heating temperature may be, for example, less than 150°C, 120°C or less, 100°C or less, 80°C or less, or 70°C or less. The heating temperature can be, for example, 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, 60°C or higher, or 70°C or higher, and may be 80°C or higher, or 100°C or higher. The heating time is not particularly limited, and may be, for example, 3 hours or less, 1 hour or less, 30 minutes or less, or 10 minutes or less. The heating time may be, for example, 1 minute or more, 15 minutes or more, 30 minutes or more, or 1 hour or more. Alternatively, the heating treatment may be performed for a longer period of time as long as no significant thermal deterioration occurs in the reinforcing film or the adherend. The heating treatment may be performed all at once, or may be performed in multiple steps.

<Reinforcing film with substrate>
When the reinforcing film disclosed herein is in the form of a pressure-sensitive adhesive sheet with a substrate, the thickness of the reinforcing film may be, for example, 1000 μm or less, 600 μm or less, 350 μm or less, or 250 μm or less. In view of the miniaturization, weight reduction, thinning, etc. of the product to which the reinforcing film is applied, in some embodiments, the thickness of the reinforcing film may be, for example, 200 μm or less, 175 μm or less, 140 μm or less, 120 μm or less, or 100 μm or less (for example, less than 100 μm). In addition, in view of handleability, etc., the thickness of the reinforcing film may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more. In some embodiments, the thickness of the reinforcing film may be, for example, 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, or 120 μm or more. The upper limit of the thickness of the reinforcing film is not particularly limited.
The thickness of the reinforcing film refers to the thickness of the portion attached to the adherend. For example, in the case of the reinforcing film 1 having the configuration shown in FIG. 1, the thickness refers to the thickness from the adhesive surface 21A of the reinforcing film 1 to the second surface 10B of the substrate 10, and does not include the thickness of the release liner 31.

The reinforcing film disclosed herein can be suitably implemented, for example, in an embodiment in which the thickness Ts of the support substrate is greater than the thickness Ta of the adhesive layer, i.e., Ts/Ta is greater than 1. Although not particularly limited, Ts/Ta may be, for example, 1.1 or more, 1.2 or more, 1.5 or more, or 1.7 or more. For example, an increase in Ts/Ta tends to make it easier to achieve good effects even when the reinforcing film is made thinner. In some embodiments, Ts/Ta may be 2 or more (e.g., greater than 2), 2.5 or more, or 2.8 or more. In addition, Ts/Ta may be, for example, 50 or less, or 20 or less. From the viewpoint of making it easier to achieve high post-heat adhesive strength even when the reinforcing film is made thinner, Ts/Ta may be, for example, 10 or less, 8 or less, or 5 or less.

The adhesive layer is preferably fixed to the support substrate. Here, the term "fixed" means that the adhesive layer exhibits sufficient anchoring properties to the support substrate to such an extent that, in a reinforcing film whose adhesive strength has increased after application to an adherend, peeling does not occur at the interface between the adhesive layer and the support substrate when the reinforcing film is peeled from the adherend. A reinforcing film with a substrate in which the adhesive layer is fixed to the support substrate can firmly integrate the adherend and the support substrate. A suitable example of a reinforcing film in which the adhesive layer is fixed to the substrate is a reinforcing film in which peeling (anchor failure) does not occur between the adhesive layer and the support substrate when the adhesive strength after heating is measured as described above. A reinforcing film in which anchor failure does not occur when the adhesive strength after heating is measured is a suitable example of a reinforcing film in which the adhesive layer is fixed to the substrate.

The reinforcing film disclosed herein can be preferably produced by a method that includes, in this order, contacting a liquid adhesive composition with a first surface of a substrate and curing the adhesive composition on the first surface to form an adhesive layer. The curing of the adhesive composition can involve one or more of drying, crosslinking, polymerization, cooling, etc., of the adhesive composition. According to the method of curing a liquid adhesive composition on the first surface of a substrate to form an adhesive layer, the adhesive layer can be more anchored to the substrate than in the method of placing the adhesive layer on the first surface by bonding the cured adhesive layer to the first surface of the substrate. Utilizing this, a reinforcing film in which the adhesive layer is fixed to the substrate can be preferably produced.

In some embodiments, the method of contacting the liquid adhesive composition with the first surface of the substrate can be a method of directly applying the adhesive composition to the first surface of the substrate. By contacting the first surface (adhesive surface) of the adhesive layer cured on the first surface of the substrate with the release surface, a reinforcing film can be obtained in which the second surface of the adhesive layer is fixed to the first surface of the substrate and the first surface of the adhesive layer is in contact with the release surface. The release surface can be the surface of a release liner, the back surface of a substrate that has been treated for release, or the like.

In addition, for example, in the case of a photocurable adhesive composition using a partial polymer (polymer syrup) of a monomer raw material, the adhesive composition may be applied to a release surface, and then the applied adhesive composition may be covered with a first surface of a substrate to bring the uncured adhesive composition into contact with the first surface of the substrate, and in this state, the adhesive composition sandwiched between the first surface of the substrate and the release surface may be irradiated with light to cure, thereby forming an adhesive layer.

The above-mentioned methods are not intended to limit the method for producing the reinforcing film disclosed herein. In producing the reinforcing film disclosed herein, any suitable method capable of adhering the adhesive layer to the first surface of the substrate can be used alone or in combination of two or more. Examples of such methods include the method of curing a liquid adhesive composition on the first surface of the substrate to form an adhesive layer, as described above, and the method of performing a surface treatment on the first surface of the substrate to enhance the anchoring property of the adhesive layer. For example, when the anchoring property of the adhesive layer to the substrate can be sufficiently improved by providing an undercoat layer on the first surface of the substrate, the reinforcing film may be produced by laminating the cured adhesive layer to the first surface of the substrate. The anchoring property of the adhesive layer to the substrate can also be improved by selecting the material of the substrate or the composition of the adhesive. The anchoring property of the adhesive layer to the substrate can also be improved by applying a temperature higher than room temperature to a reinforcing film having an adhesive layer on the first surface of the substrate. The temperature applied to enhance anchoring properties may be, for example, about 35°C to 80°C, about 40°C to 70°C or higher, or about 45°C to 60°C.

When the reinforcing film disclosed herein is in the form of an adhesive sheet having a first adhesive layer provided on a first surface of a substrate and a second adhesive layer provided on a second surface of the substrate (i.e., a double-sided adhesive substrate-attached adhesive sheet), the first adhesive layer and the second adhesive layer may have the same configuration or different configurations. When the first adhesive layer and the second adhesive layer have different configurations, the difference may be, for example, a difference in composition or structure (thickness, surface roughness, formation range, formation pattern, etc.). For example, the second adhesive layer may be an adhesive layer that does not contain polymer (B). In addition, the surface of the second adhesive layer (second adhesive surface) may have a surface elasticity modulus at 23°C outside the range of 1 to 20 kPa (for example, more than 20 kPa) or may be 30 kPa or more.

<Reinforcing film with release liner>
The reinforcing film disclosed herein may take the form of an adhesive product in which the surface (adhesive surface) of the adhesive layer is in contact with the release surface of a release liner. Thus, this specification can provide a reinforcing film with a release liner, which includes any of the reinforcing films disclosed herein and a release liner having a release surface in contact with the adhesive surface of the reinforcing film.

The thickness of the release liner is not particularly limited, but is usually about 5 μm to 200 μm. A release liner having a thickness within the above range is preferable because it is easy to attach to the adhesive layer and easy to peel from the adhesive layer. In some embodiments, the thickness of the release liner may be, for example, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. In addition, from the viewpoint of facilitating peeling from the adhesive layer, the thickness of the release liner may be, for example, 100 μm or less, or 80 μm or less. The release liner may be subjected to a known antistatic treatment such as a coating type, kneading type, or vapor deposition type, as necessary.

The release liner is not particularly limited, and examples thereof include a release liner having a release layer on the surface of a liner substrate such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), and a release liner made of a resin film formed from a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.). Because of their excellent surface smoothness, release liners having a release layer on the surface of a resin film as a liner substrate and release liners made of a resin film formed from a low-adhesion material can be preferably used. The resin film is not particularly limited as long as it is a film that can protect the adhesive layer, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-vinyl acetate copolymer film, etc. To form the release layer, known release treatment agents can be used, such as silicone-based release treatment agents, long-chain alkyl-based release treatment agents, olefin-based release treatment agents, fluorine-based release treatment agents, fatty acid amide-based release treatment agents, molybdenum sulfide, and silica powder. The use of silicone-based release treatment agents is particularly preferred.

The thickness of the release layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and preferably about 0.1 μm to 1 μm. The method for forming the release layer is not particularly limited, and any known method can be used as appropriate depending on the type of release treatment agent used, etc.

<Applications>
The reinforcing film provided by this specification can exhibit good reworkability, for example, in the initial stage after being attached to the adherend, and can contribute to suppressing a decrease in yield and improving the quality of products containing the reinforcing film. The adhesive strength of the reinforcing film can be greatly increased by aging or heating after being attached to the adherend. For example, by heating at an appropriate timing after being attached to the adherend, the reinforcing film can be firmly attached to the adherend. Taking advantage of such characteristics, the reinforcing film disclosed herein can be preferably used in various fields for the purpose of reinforcing members contained in various products.

The reinforcing film disclosed herein can be preferably used as a reinforcing film that is attached to an adherend and reinforces the adherend, for example, in the form of a substrate-attached pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on at least the first surface of a film-like substrate having a first surface and a second surface. In such a reinforcing film, a film substrate containing a resin film as a base film can be preferably used. In addition, from the viewpoint of enhancing reinforcing performance, it is preferable that the pressure-sensitive adhesive layer is fixed to the first surface of the film-like substrate.
For example, optical components used in optical products and electronic components used in electronic products are becoming highly integrated, smaller, lighter, and thinner, and multiple thin optical/electronic components with different linear expansion coefficients and thicknesses may be stacked. By attaching the reinforcing film to such components, it is possible to impart appropriate rigidity to the optical/electronic components. This makes it possible to suppress curling and curvature caused by stress that may occur between multiple components with different linear expansion coefficients and thicknesses during the manufacturing process and/or in the product after manufacture.
Furthermore, in the manufacturing process of optical products/electronic products, in the aspect of performing shaping processing such as cutting on thin optical/electronic components as described above, by attaching a reinforcing film to the components, local stress concentration on the optical/electronic components accompanying processing can be alleviated, and the risk of cracks, breakage, peeling of laminated components, etc. Attaching a reinforcing member to an optical/electronic component and handling it can also be useful for alleviating local stress concentration during transportation, stacking, rotation, etc. of the components, and for suppressing bending or bending due to the weight of the components.
Furthermore, in the case of devices such as optical products and electronic products including the above-mentioned reinforcement film, when the devices are used by consumers in the market, even if the devices are subjected to unintentional stress such as when the devices are dropped, placed under a heavy object, or hit by a flying object, the inclusion of the reinforcement film in the devices can reduce stress on the devices. Therefore, the inclusion of the reinforcement film in the devices can improve the durability of the devices.

The reinforcing film disclosed herein may be preferably used, for example, in a form attached to a member constituting various portable devices (portable devices). Here, "portable" does not mean that it is merely portable, but that it has a level of portability that allows an individual (average adult) to carry it relatively easily. Examples of portable devices herein include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices, 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, and other portable electronic devices, as well as mechanical wristwatches, pocket watches, flashlights, hand mirrors, and the like. Examples of members constituting the above portable electronic devices may include optical films and display panels used in image display devices such as thin-layer displays such as liquid crystal displays and film-type displays. The reinforcing film disclosed herein may also be preferably used in a form attached to various members in automobiles, home appliances, and the like.

The reinforcing film disclosed herein has bending recovery and bending retention, and can be preferably used by taking advantage of these characteristics in a form in which it is attached to a component constituting an apparatus having a bendable element (e.g., a flexible device such as a flexible display, which may also be called a rollable device or a foldable device). Examples of such an apparatus include the various mobile devices (portable devices) described above. Examples of components constituting the above-mentioned mobile electronic devices include optical films and display panels used in image display devices such as liquid crystal displays and organic EL (electroluminescence) displays. The reinforcing film disclosed herein can be preferably used in such mobile electronic devices for reinforcing components constituting the apparatus (typically, image display devices called flexible devices or foldable devices, etc.).

The reinforcing film disclosed herein is suitable for applications such as reinforcing optical members during the manufacture and transportation of optical members used as components of liquid crystal display panels, plasma display panels (PDPs), organic EL displays, etc. It is useful as a reinforcing film applied to optical members such as polarizing plates (polarizing films), wave plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion sheets, and reflective sheets for liquid crystal display panels.

The reinforcing film disclosed herein is not particularly limited in its use, and may be used in a variety of applications for the purpose of imparting rigidity and impact resistance. The reinforcing film disclosed herein is not only preferably used for flexible device applications as described above, but can also be used for other applications not involving flexible devices. The fact that the reinforcing film has flex recovery and flex retention means that there are fewer limitations on the range of application of the reinforcing film, which is a great practical advantage.

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

[Synthesis of Polymer (A)]
(Synthesis Example A1)
In a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser, 90.2 parts of 2-ethylhexyl acrylate (2EHA), 8.6 parts of 4-hydroxybutyl acrylate (4HBA), 1.2 parts of N-acryloylmorpholine (ACMO), 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and ethyl acetate as a polymerization solvent were charged, and nitrogen gas was introduced while gently stirring. The liquid temperature in the flask was kept at about 65°C, and a polymerization reaction was carried out for 6 hours to prepare an acrylic polymer A1 solution with a polymer concentration of 35%. The weight average molecular weight (Mw) of the acrylic polymer A1 was 540,000.

(Synthesis Example A2)
A solution of acrylic polymer A2 was obtained by carrying out solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to 2EHA/4HBA/ACMO/butyl acrylate (BA)=86.1 parts/9.7 parts/1.8 parts/2.4 parts.

(Synthesis Example A3)
A solution of acrylic polymer A3 was obtained by carrying out solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to BA/4HBA=96 parts/4 parts.

(Synthesis Example A4)
A solution of acrylic polymer A4 was obtained by carrying out solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to 2EHA/HEA/methyl methacrylate (MMA)/N-vinyl-2-pyrrolidone (NVP) = 65 parts/15 parts/7 parts/13 parts.

[Synthesis of polymer (B)]
(Synthesis Example B1)
101.15 parts of ethyl acetate, 40 parts of MMA, 20 parts of n-butyl methacrylate (BMA), 20 parts of 2-ethylhexyl methacrylate (2EHMA), 8.7 parts of polyorganosiloxane skeleton-containing methacrylate monomer having a functional group equivalent of 900 g/mol (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Co., Ltd.), 11.3 parts of polyorganosiloxane skeleton-containing methacrylate monomer having a functional group equivalent of 4600 g/mol (trade name: KF-2012, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.09 parts of thioglycerol as a chain transfer agent were placed in a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, a cooler and a dropping funnel. Then, after stirring for 30 minutes under a nitrogen atmosphere at 70 ° C., 0.2 parts of AIBN were added as a thermal polymerization initiator and reacted at 70 ° C. for 3 hours. After stirring at 80° C. for 30 minutes, 0.1 part of AIBN was further added and reacted at 80° C. for 2 hours. Then, 0.05 part of AIBN was further added and reacted at 80° C. for 2 hours to obtain polymer B1. The Mw of the obtained polymer B was 90,200.

(Synthesis examples B2 to B6)
Polymers B2 to B10 were prepared in the same manner as in Synthesis Example B1, except that the amount of the chain transfer agent (thioglycerol) used was changed to 0.11 parts (Synthesis Example B2), 0.3 parts (Synthesis Example B3), 0.5 parts (Synthesis Example B4), 0.6 parts (Synthesis Example B5), 0.7 parts (Synthesis Example B6), 0.8 parts (Synthesis Example B7), 1.5 parts (Synthesis Example B8), 0.03 parts (Synthesis Example B9), or 8 parts (Synthesis Example B10) per 100 parts of the monomer raw material. The weight average molecular weights (Mw) of the obtained polymers (B) were 83,800 for polymer B2, 44,800 for polymer B3, 32,200 for polymer B4, 27,600 for polymer B5, 24,500 for polymer B6, 20,000 for polymer B7, 12,600 for polymer B8, 127,000 for polymer B9, and 2,960 for polymer B10.

The Mw of each of the above-mentioned polymers was measured under the following conditions using a GPC device (HLC-8220GPC, manufactured by Tosoh Corporation) and calculated in terms of polystyrene.
[GPC conditions]
Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution)
Sample injection volume: 10 μL
・Eluent: THF ・Flow rate: 0.6mL/min
Measurement temperature: 40°C
·column:
Sample column: TSKguardcolumn SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns)
Reference column: TSKgel SuperH-RC (1 column)
Detector: Differential refractometer (RI)

[Preparation of reinforcing film]
Example 1
100 parts of acrylic polymer A1, 2.0 parts of polymer B1, and 0.10 parts of isocyanate compound C1 (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent in terms of solid content were added, and the mixture was diluted with ethyl acetate so that the total solid content became 30%, thereby obtaining an acrylic pressure-sensitive adhesive solution according to this example.
A release liner made of polyester resin having a thickness of 75 μm and having one side treated with silicone (product name "Diafoil MRF75", manufactured by Mitsubishi Chemical Corporation) was prepared, and the acrylic adhesive solution obtained above was applied to the silicone-treated surface, followed by drying at 130° C. for 1 minute to form an adhesive layer having a thickness of 25 μm.
A 50 μm-thick polyimide substrate (product name "Upilex 50S", manufactured by Ube Industries, Ltd.) was then bonded to the surface of the resulting pressure-sensitive adhesive layer to obtain a reinforcing film according to this example. This reinforcing film has a pressure-sensitive adhesive layer on one side of a substrate, and has the form of a pressure-sensitive adhesive sheet with a release liner in which the release surface of a release liner is in contact with the pressure-sensitive adhesive layer on one side of the substrate.
In addition, for the reinforcing film of this example, the molar ratio ([NCO]/[OH]) was calculated from the OH amount (the number of moles of hydroxyl groups in the acrylic polymer A1) and the NCO amount (the number of moles of isocyanate groups in the isocyanate compound) in the pressure-sensitive adhesive layer, and was found to be 0.008.

<Examples 2 to 8>
Instead of polymer B1, polymer B2 (Example 2), polymer B3 (Example 3), polymer B4 (Example 4), polymer B5 (Example 5), polymer B6 (Example 6), polymer B7 (Example 7), or polymer B8 (Example 8) was used, and other than that, an acrylic pressure-sensitive adhesive solution according to each example was obtained in the same manner as in Example 1. A reinforcing film according to each example was produced in the same manner as in Example 1, except that each of these acrylic pressure-sensitive adhesive solutions was used.

<Examples 9 to 12>
The amount of isocyanate compound C1 used was changed to 0.015 parts (Example 9), 0.05 parts (Example 10), 0.20 parts (Example 11), or 0.60 parts (Example 12) in terms of solid content relative to 100 parts of acrylic polymer A1, as shown in Table 1. The acrylic pressure-sensitive adhesive solutions of each example were obtained in the same manner as in Example 7, except that these acrylic pressure-sensitive adhesive solutions were used. The reinforcing films of each example were prepared in the same manner as in Example 1, except that these acrylic pressure-sensitive adhesive solutions were used.

Example 13
An acrylic pressure-sensitive adhesive solution according to this example was obtained in the same manner as in Example 5, except that the amount of polymer B5 used was changed to 1.0 part per 100 parts of acrylic polymer A1, as shown in Table 1. A reinforcing film according to this example was produced in the same manner as in the production of the reinforcing film according to Example 1, except that the obtained acrylic pressure-sensitive adhesive solution was used.

<Examples 14 to 16>
Acrylic pressure-sensitive adhesive solutions according to each example were obtained in the same manner as in Example 7, except that the amount of polymer B7 used was changed to 1.0 part (Example 14), 3.0 parts (Example 15), or 6.0 parts (Example 16) per 100 parts of acrylic polymer A1, as shown in Table 1. Reinforcing films according to each example were prepared in the same manner as in Example 1, except that these acrylic pressure-sensitive adhesive solutions were used.

<Example 17>
An acrylic pressure-sensitive adhesive solution according to this example was obtained in the same manner as in Example 7, except that the acrylic pressure-sensitive adhesive solution was used instead of the acrylic polymer A1. A reinforcing film according to this example was produced in the same manner as in the production of the reinforcing film according to Example 1, except that the obtained acrylic pressure-sensitive adhesive solution was used.

<Example 18>
An acrylic adhesive solution according to this example was obtained in the same manner as in Example 7, except that acrylic polymer A3 was used instead of acrylic polymer A1, and 0.07 parts of isocyanate compound C2 (product name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) was used as a crosslinking agent, calculated as a solid content, per 100 parts of acrylic polymer A3. A reinforcing film according to this example was produced in the same manner as in Example 1, except that the obtained acrylic adhesive solution was used.

<Examples 19 to 20>
Acrylic pressure-sensitive adhesive solutions according to each example were obtained in the same manner as in Example 18, except that the amount of isocyanate compound C2 used was changed to 0.09 parts (Example 19) or 0.395 parts (Example 20) in terms of solid content per 100 parts of acrylic polymer A3, as shown in Table 1. Reinforcing films according to each example were prepared in the same manner as in the preparation of the reinforcing film according to Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

<Comparative Examples 1 and 2>
Except for using polymer B9 (Comparative Example 1) or polymer B10 (Comparative Example 2) instead of polymer B1, an acrylic pressure-sensitive adhesive solution according to each example was obtained in the same manner as in Example 1. Except for using each of these acrylic pressure-sensitive adhesive solutions, a reinforcing film according to each example was produced in the same manner as in the production of the reinforcing film according to Example 1.

<Comparative Example 3>
An acrylic adhesive solution according to this example was obtained in the same manner as in Example 7, except that acrylic polymer A4 was used instead of acrylic polymer A1, and 0.50 parts of isocyanate compound C2 (product name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) was used as a crosslinking agent, calculated as a solid content, per 100 parts of acrylic polymer A4. A reinforcing film according to this example was produced in the same manner as in Example 1, except that the obtained acrylic adhesive solution was used.

<Comparative Examples 4 to 5>
Acrylic pressure-sensitive adhesive solutions according to each example were obtained in the same manner as in Comparative Example 3, except that the amount of isocyanate compound C2 used was changed to 1.10 parts (Comparative Example 4) or 2.50 parts (Comparative Example 5) in terms of solid content per 100 parts of acrylic polymer A4, as shown in Table 1. Reinforcing films according to each example were prepared in the same manner as in the preparation of the reinforcing film according to Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

<Evaluation>
[Surface Elastic Modulus]
The reinforcing film according to each example was aged at 50° C. for one day, and the surface elastic modulus was measured. The release liner protecting the adhesive surface was peeled off, and a nanoindenter device (Triboindenter manufactured by Hysitron Inc.) was used to press an indenter into the surface of the adhesive layer to a depth of 6 μm, and the maximum load (Pmax) [GPa/mm ² ] was obtained by measurement using the nanoindenter. This was calculated using the formula:
Surface hardness [GPa] = Pmax/A
The surface hardness was calculated by substituting the above formula into the above formula, and the surface hardness was converted into a unit of [kPa] and recorded as the surface elastic modulus at 23° C. (23° C. surface elastic modulus). The measurement conditions are as follows. In the above formula, A is the contact projected area of the indenter [mm ² ].
(Measurement conditions)
Indenter approach speed: 5 μm/s
Maximum displacement: 6 μm
Pushing speed: 5μm/s
Pulling speed: 5μm/s
Indenter used: Conical (spherical indenter: radius of curvature 10 μm)
Measurement method: Single indentation measurement Measurement temperature: Room temperature (23°C)

[Bulk Elastic Modulus G' and tan δ]
A release liner R1 (trade name "Diafoil MRF75", manufactured by Mitsubishi Chemical Corporation) made of polyester resin with a thickness of 75 μm and silicone-treated on one side was prepared, and the acrylic adhesive solution according to each example was applied to the silicone-treated surface, and dried at 130° C. for 1 minute to form an adhesive layer with a thickness of 25 μm. Next, the surface of the obtained adhesive layer was covered with a release liner R2 (trade name "Diafoil MRE75", manufactured by Mitsubishi Chemical Corporation) made of polyester resin with a thickness of 75 μm and silicone-treated on one side, with the silicone-treated surface facing the adhesive layer, and aged at 50° C. for 1 day.
Only the resulting pressure-sensitive adhesive layer was taken out and laminated to a thickness of about 1 mm, which was then punched out to a diameter of 8 mm to prepare a cylindrical pellet, which was used as a measurement sample.
The measurement sample was fixed to a φ8 mm parallel plate jig, and the storage modulus G', loss modulus G" and loss tangent tan δ were measured under the following conditions using a dynamic viscoelasticity measuring device ("ARES" manufactured by T.A. Instruments) to determine the storage modulus G' ₂₃ [kPa] at 23° C., the storage modulus G' ₈₀ [kPa] at 80° C. and tan δ at 80° C. (loss modulus G" ₈₀ at 80° C./storage modulus G' ₈₀ at 80° C.).
・Measurement mode: Shear mode ・Temperature range: -70℃ to 200℃
Heating rate: 5°C/min
Frequency: 1Hz
The storage modulus G' corresponds to the portion stored as elastic energy when the material is deformed, and is an index showing the degree of hardness. The loss modulus G'' corresponds to the portion of energy lost that is dissipated due to internal friction, etc. when the material is deformed, and indicates the degree of viscosity.

[Initial adhesive strength]
The reinforcing film according to each example was aged at 50°C for 1 day, and cut together with the release liner to a width of 25 mm x length of 140 mm to be used as a measurement sample. The release liner was peeled off from the measurement sample to expose the adhesive surface, and a 2 kg hand roller was rolled back and forth once to press the sample against a stainless steel plate (SUS304BA plate) as an adherend. The measurement sample thus pressed against the adherend was left at an environmental temperature of 23°C for 30 minutes, and then a tensile tester (manufactured by Shimadzu Corporation, trade name "Autograph AG-Xplus HS 6000mm/min high-speed model (AG-50NX plus)") was used to measure the load when the reinforcing film was peeled off from the adherend under the conditions of a peel angle of 180 degrees and a peel speed (tensile speed) of 300 mm/min, and the average load during measurement was recorded as the initial adhesive strength [gf/25mm].

[Adhesive strength after heating]
For the reinforcing film according to each example, a measurement sample was prepared in the same manner as in the above initial adhesive strength measurement, and was pressed against the adherend. The measurement sample pressed against the adherend was heated for 60 minutes at an environmental temperature of 60 ° C. Then, the sample was left at an environmental temperature of 23 ° C. for 30 minutes, and the load when the reinforcing film was peeled from the adherend was measured using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)") under the conditions of a peel angle of 180 degrees and a peel speed (tensile speed) of 300 mm / min, and the average load during measurement was recorded as the adhesive strength after heating [gf / 25 mm].

[Flexion retention test]
The reinforcing film according to each example was aged at 50°C for one day, and then the release liner was peeled off. A 25 μm thick polyimide substrate (trade name "Upilex 25S", manufactured by Ube Industries, Ltd.) was attached to the exposed adhesive surface, and heated at 60°C for 60 minutes to adhere. Next, the obtained measurement sample (laminate) was fixed in a folded state so that the 25 μm substrate side was on the inside and had a diameter of 6 mm, and heated at 80°C for 15 hours. Then, it was left at room temperature (23°C) and confirmed to have cooled sufficiently, after which the folded state of the measurement sample was released, and within 10 minutes after the release, the bending angle [°] of the folded measurement sample was measured using a protractor to evaluate the bending recovery. The bending angle is the opening angle of the measurement sample (the angle at which the measurement sample opens from the folded state), and the closer to 180° the better the bending recovery, and the closer to 0° the bending angle the worse the bending recovery.
Next, to evaluate the bending retention strength, the presence or absence of "peeling" at the bent portion of the measurement sample was visually confirmed, and a case where "peeling" was not observed was rated as "O", and a case where "peeling" was observed was rated as "X".

The evaluation results for the reinforcing film of each example are shown in Table 1. Table 1 also shows an outline of the composition of the adhesive layer of each example.

As shown in Table 1, the adhesives according to Examples 1 to 20 contained polymer (A) and polymer (B), and the Mw of the polymer (B) was within the range of 10,000 to 100,000. The reinforcing films according to these examples better achieved both low initial adhesive strength and increased adhesive strength after heating compared to Comparative Examples 1 and 2, in which the Mw of the polymer (B) was outside the range of 10,000 to 100,000. Furthermore, the reinforcing films according to Examples 1 to 20 had an adhesive layer with a surface modulus at 23°C within the range of 1 to 20 kPa, and also had good flex recovery and flex retention. On the other hand, in Comparative Examples 3 to 5, in which the 23°C surface modulus was outside the range of 1 to 20 kPa, peeling was observed in the flex retention test.

More specifically, in comparison with Examples 1 to 8, the lower the Mw of polymer (B) is below 100,000, the lower the initial adhesive strength is, and the lowest initial adhesive strength was observed in the range of Mw 20,000 to 30,000. The adhesive strength after heating was high in the range of Mw 80,000 to 100,000 and in the range of Mw 20,000 to 30,000. In Examples 5 and 6, the low initial adhesive strength and the increase in adhesive strength after heating were most balanced. On the other hand, in Comparative Example 1, where the Mw of polymer (B) exceeded 100,000, the initial adhesive strength was high and the light peelability was poor. In Comparative Example 2, where the Mw of polymer (B) was less than 10,000, the adhesive strength did not increase after heating. This is thought to be because the low molecular weight polymer (B) formed a WBL (Weak Boundary Layer) on the surface of the adhesive layer and remained on the surface of the adhesive layer even after heating.

In addition, in comparison with Examples 9 to 12, the higher the 23°C surface elastic modulus of the pressure-sensitive adhesive layer in the range of 1 to 20 kPa, the more the bending recovery was improved, and the initial adhesive strength and the adhesive strength after heating tended to be lower. Examples 10 to 12 were superior to Example 9 in bending recovery, with the 23°C surface elastic modulus being 2 kPa or more, and the tan δ ₈₀ at 80°C being in the range of 0.10 to 0.60. In addition, in Example 12, both the surface elastic modulus and the bulk elastic modulus were high, and the increase in adhesive strength after heating was relatively low compared to Examples 9 to 11. In addition, no difference was observed in the 23°C bulk elastic modulus _G'23 of the pressure-sensitive adhesive layer in Examples 9 to 11. In addition, the 80°C bulk elastic modulus _G'80 in Examples 1 to 8 and 10 was equivalent. With respect to Examples 1 to 12, it can be said that the 23°C surface elastic modulus had a higher correlation with bending recovery than the bulk elastic modulus. In Examples 1 to 12, the molar ratio of isocyanate groups to hydroxyl groups ([NCO]/[OH]) in the pressure-sensitive adhesive layers of Examples 1 to 8 and 10 to 11, which showed a better balance of improved initial adhesive strength, post-heat adhesive strength, flex recovery and flex retention, was within the range of 0.002 to 0.03.

In addition, a comparison of Examples 13 to 16 confirmed that the adhesive strength tended to decrease as the amount of polymer (B) used increased. In Examples 13 to 15, the initial adhesive strength was less than 400 gf/25 mm, and the adhesive strength after heating was 500 gf/25 mm or more, and a good balance was achieved between the easy peelability at the initial stage of application and the increase in adhesive strength after heating. In addition, an excellent increase in adhesive strength was confirmed in Examples 13 to 14 (especially Example 13). In addition, as the amount of polymer (B) used increased, the 23°C surface elasticity increased and the flex recovery tended to decrease. In addition, the results of Examples 17 to 20 confirmed that the desired effect could be achieved even if the type of adhesive polymer (A) or the type of crosslinking agent was changed. In Examples 17 to 18, the increase in adhesive strength after heating was greater than in Examples 19 to 20.

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.

1, 2, 3 Reinforcing film 10 Support substrate 10A First surface 10B Second surface 21 Pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer)
21A Adhesive surface (first adhesive surface)
21B Adhesive surface (second adhesive surface)
22 Adhesive layer (second adhesive layer)
22A Adhesive surface (second adhesive surface)
31, 32 Release liner 100, 200, 300 Reinforcement film with release liner

Claims (6)

A reinforcing film comprising a supporting substrate and a pressure-sensitive adhesive layer laminated on one or both sides of the supporting substrate ,
The supporting substrate is made of a resin film,
The pressure-sensitive adhesive layer contains a polymer (A) and a polymer (B),
The polymer (A) is an acrylic polymer,
The acrylic polymer contains 50% by weight or more of monomer units derived from a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms,
The proportion of monomer units derived from methyl methacrylate in the acrylic polymer is 6% by weight or less,
The acrylic polymer contains monomer units derived from a hydroxyl group-containing monomer in an amount of 1% by weight or more and 12% by weight or less,
The polymer (B) contains a monomer unit having a polyorganosiloxane skeleton and a (meth)acrylic monomer unit,
The pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent in an amount of 0.015 parts by weight or more and less than 0.5 parts by weight based on 100 parts by weight of the polymer (A),
the pressure-sensitive adhesive layer does not contain a tackifier resin or contains the tackifier resin in an amount of less than 3 parts by weight based on 100 parts by weight of the polymer (A);
The pressure-sensitive adhesive layer has a surface elastic modulus of 1 to 20 kPa at 23° C.,
The weight average molecular weight of the polymer (B) is 10,000 to 100,000. The pressure-sensitive adhesive layer has a bulk modulus _G'23 at 23°C of 10 to 200 kPa, a bulk modulus _G'80 at 80°C of 5 to 100 kPa, and a tan δ ₈₀ at 80°C of 0.10 to 0.60. The reinforcing film according to claim 1 or 2, wherein the content of the polymer (B) in the pressure-sensitive adhesive layer is 0.5 to 5 parts by weight per 100 parts by weight of the polymer (A). The reinforcing film according to any one of claims 1 to 3 , wherein the molar ratio ([NCO]/[OH]) of isocyanate groups to hydroxyl groups contained in the pressure-sensitive adhesive layer is 0.002 to 0.03. An optical member having the reinforcing film according to any one of claims 1 to 4 attached thereto. An electronic component having the reinforcing film according to any one of claims 1 to 4 attached thereto.

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