JP6977761B2 - Adhesive sheet and image display device using it - Google Patents

Description

The present invention relates to an image display device such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, a pen tablet, etc., and an adhesive sheet that can be used therefor.

In recent years, in order to improve the visibility of an image display device, an image display panel such as a liquid crystal display (LCD), a plasma display (PDP) or an electroluminescence display (ELD), and protection placed on the front side (visual side) thereof. The gap between the panel and the touch panel member is filled with an adhesive sheet or a liquid adhesive to suppress reflection of incident light or emitted light from a display image at the air layer interface.

As a method of filling the voids between the constituent members for an image display device with an adhesive, a method of filling the voids with a liquid adhesive resin composition containing an ultraviolet curable resin and then irradiating the voids with ultraviolet rays to cure the voids. Is known (Patent Document 1).

Further, a method of filling the gaps between the constituent members for an image display device with an adhesive sheet is also known. For example, Patent Document 2 describes, as a method for manufacturing a laminated body for forming an image display device, which has a structure in which an image display device constituent member is laminated on at least one side of a transparent double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet is primarily crosslinked by ultraviolet rays. Is disclosed to a method of secondary curing the adhesive sheet by irradiating the adhesive sheet with ultraviolet rays via the image display device constituent member after the image is attached to the image display device constituent member.

Patent Document 3 includes at least two components for an image display device facing each other, and at least one of the components for an image display device has an image display having a stepped portion and a flat surface portion excluding the stepped portion on the bonded surface. The device is an image display device having a configuration in which the space between the two components for an image display device is filled with a transparent double-sided adhesive sheet for an image display device, and the transparent double-sided adhesive sheet for an image display device is a device. It is formed from a non-solvent-based pressure-sensitive adhesive composition containing no solvent, the thickness of the maximum thickness portion of the pressure-sensitive adhesive sheet is 250 μm or less, the gel content at a position in contact with the step portion is 10% or more, and An image display device is disclosed, which is characterized in that it is smaller than the gel fraction at a position in contact with the flat surface portion.

In Patent Document 4, image display device constituent members are laminated via a transparent double-sided adhesive sheet as a method for manufacturing a laminate for image display device configuration that can simultaneously realize unevenness followability and foaming reliability. Regarding the method for manufacturing a laminated body for forming an image display device having a structure, the pressure-sensitive adhesive composition is formed into a single-layer or multi-layer sheet, which is cross-linked with ultraviolet rays and first cured to perform primary curing. After forming an adhesive sheet and laminating two image display device constituent members via a transparent double-sided adhesive sheet before secondary curing, ultraviolet rays are irradiated from at least one image display device constituent member side, and the member is passed through this member. A method characterized by cross-linking the transparent double-sided pressure-sensitive adhesive sheet before secondary curing with ultraviolet rays to perform secondary curing is disclosed.

Further, the following are disclosed as an adhesive or an adhesive sheet for bonding between constituent members for an image display device.
For example, Patent Document 5 describes adhesion using a hot-melt type adhesive composition containing urethane (meth) acrylate having a weight average molecular weight of 20,000 to 100,000 as a main component and having a loss tangent of less than 1 at 25 ° C. The sheet is disclosed.

In Patent Document 6, a touch panel comprising a (meth) acrylic polymer obtained by copolymerizing a (meth) acrylic monomer having a crosslinkable functional group and a monomer containing a specific macromer and a cross-linking agent is attached. Accordingly, a suitable pressure-sensitive adhesive layer is disclosed.

Patent Document 7 describes as a transparent double-sided adhesive sheet for an image display device capable of alleviating distortion generated in an adhesive sheet after bonding even if the bonding surface has a stepped portion having a height of 50 μm to 100 μm. A transparent double-sided adhesive sheet for an image display device used for bonding an image display device component having a stepped portion having a height of 50 μm to 100 μm and a flat surface portion on the bonding surface and another image display device component. When the thickness of the maximum thickness portion of the adhesive sheet is 250 μm or less, the gel content at the position where the adhesive sheet comes into contact with the step portion when bonded is 10% or more, and the bonded sheet is bonded. Disclosed is a transparent double-sided pressure-sensitive adhesive sheet for an image display device, which is smaller than the gel fraction at a position where it comes into contact with the flat surface portion.

International Publication No. 2010/027041 International Publication No. 2012/032995 Japanese Unexamined Patent Publication No. 2014-167634 WO2012 / 032995 WO2010 / 0388366 Gazette Japanese Unexamined Patent Publication No. 2013-18227 Japanese Unexamined Patent Publication No. 2014-58686

For example, in the display screen of a mobile phone or the like, a configuration is adopted in which a polarizing film or the like is laminated on a liquid crystal panel display (LCD), and a plastic protective panel is laminated on the polarizing film or the like via an adhesive or a sheet. A light-transmitting portion such as a printing portion is usually attached to the peripheral edge of the back surface of the protective panel.
When the protective panel to which such a printing portion is attached is attached to another image display device component such as a touch panel via an adhesive sheet, the adhesive sheet can be filled to every corner by following the printing step. At the same time, if the surface of the adhesive sheet is not smooth, the adhesive sheet will be distorted or deformed when the image display components are attached, which may cause a decrease in visibility due to uneven display. Therefore, the adhesive sheet is flexible. Is required. Moreover, there is a problem that distortion and deformation are likely to occur in the adhesive sheet due to a printing step or the like.

On the other hand, it is required that the exposed adhesive surface does not become sticky even in a harsh environment such as high temperature and high humidity. Not only that, the pressure-sensitive adhesive sheet after the image display device components are bonded via the pressure-sensitive adhesive sheet is also required to have a high cohesive force that does not cause peeling or foaming.

Therefore, in the present invention, for example, even when a component for an image display device having a light-transmitting portion such as a printing portion and a light-transmitting portion in a bonding surface is bonded, the followability to a step portion or the like is achieved. And surface flatness can be obtained, distortion and deformation do not occur even in the light opaque part, and the adherends can be firmly bonded to each other with high cohesive force, and further, under high temperature and high humidity, etc. It is an object of the present invention to provide a new adhesive sheet and an image display device capable of preventing the exposed adhesive surface from becoming sticky even in the harsh environment of the above.

The present invention is a pressure-sensitive adhesive sheet containing a (meth) acrylic copolymer (A) and a photopolymerization initiator (C) and partially photo-cured, and any portion of the surface of the pressure-sensitive adhesive sheet. In addition, it has a soft part having a gel content of less than 1% and a hard part having a gel content of 40% or more.
The (meth) acrylic copolymer (A) contains a monomer a having a glass transition temperature (Tg) of less than 0 ° C., a monomer b having a glass transition temperature (Tg) of 0 ° C. or higher and lower than 80 ° C., and a glass transition temperature. It is a (meth) acrylic acid ester copolymer or a vinyl copolymer obtained by copolymerizing with a monomer c having (Tg) of 80 ° C. or higher.
The molar ratio of the monomer a, the monomer b, and the monomer c in the (meth) acrylic acid ester copolymer or the vinyl copolymer constituting the (meth) acrylic copolymer (A) is a: b :. c = 10 to 40:90 to 35: 2 to 25,
The glass transition temperature (Tg [S]) of the soft portion measured by the differential scanning calorimeter (DSC) is −70 ° C. to −10 ° C., and the glass transition temperature (Tg [H]) of the hard portion is An adhesive sheet having a temperature of -60 ° C to + 20 ° C and a difference (Tg [H] -Tg [S]) between the glass transition temperature of the hard portion and the glass transition temperature of the soft portion of 3 ° C or more. suggest.

The present invention also includes at least two components for an image display device facing each other, and at least one of the components for an image display device is described above in an image display device having a light-transmitting portion and a light-transmitting portion on a bonded surface. It is an image display device having a structure in which the space between two components for an image display device is filled with an adhesive sheet, and the gel fraction at a position in contact with the light transmitting portion of the adhesive sheet is 40% or more. Moreover, we propose an image display device characterized in that the gel fraction at a position in contact with the light opaque portion is less than 1%.

In the adhesive sheet proposed by the present invention, a soft portion having a gel fraction of less than 1% can obtain followability to a stepped portion and surface flatness, and can alleviate distortion and deformation in the sheet. On the other hand, the hard portion having a gel content of 40% or more can not only prevent the adhesive surface from becoming sticky, but also can firmly adhere the adherends to each other with a high cohesive force.
Therefore, for example, even when a component for an image display device having a light-transmitting portion such as a printing portion and a light-transmitting portion in the bonding surface is bonded, the adhesive sheet as a whole follows the printing step portion. Properties and surface flatness can be obtained, distortion and deformation do not occur even in the light-impermeable portion, and adherends can be firmly bonded to each other with high cohesive force. Further, by making the exposed adhesive surface a hard portion, it is possible to prevent the exposed adhesive surface from becoming sticky even in a harsh environment such as high temperature and high humidity.

It is a top perspective view which showed an example of the pressure-sensitive adhesive sheet which concerns on this invention. It is a top perspective view which showed the other example of the pressure-sensitive adhesive sheet which concerns on this invention. It is a top perspective view which showed the further example of the pressure-sensitive adhesive sheet which concerns on this invention. 3 (B) is a view showing an example of the pressure-sensitive adhesive sheet laminated body provided with the pressure-sensitive adhesive sheet, (A) is a top perspective view thereof, and (B) is a sectional view. It is a top perspective view which showed the further example of the pressure-sensitive adhesive sheet which concerns on this invention.

Hereinafter, an example of the embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

<Book adhesive sheet>
The pressure-sensitive adhesive sheet according to the present embodiment (hereinafter referred to as "the main pressure-sensitive adhesive sheet") is a pressure-sensitive adhesive sheet containing a (meth) acrylic copolymer (A) as a base polymer and partially photocured. Therefore, any of the pressure-sensitive adhesive sheets is a pressure-sensitive adhesive sheet having a soft portion having a gel content of less than 1% and a hard portion having a gel content of 40% or more.

As a method for measuring the gel fraction, extraction with a solvent can be mentioned. Specifically, when the polymer constituting the pressure-sensitive adhesive sheet is not crosslinked, a solvent (good solvent) for dissolving the polymer is selected, and then the pressure-sensitive adhesive sheet is extracted using the solvent. Examples of the solvent for extraction include ethyl acetate, acetone, toluene, xylene, lower alcohols, tetrahydrofuran and the like.
The temperature and time for extraction may be set arbitrarily. After performing the extraction operation, the component (swelling component) that has not been dissolved in the solvent may be recovered, dried, and then the weight fraction may be measured. Specific examples of the extraction method include Soxhlet extraction and the methods described in Examples described later.
If the gel fraction is high, the pressure-sensitive adhesive sheet may be appropriately crushed and used for extraction.

As shown in FIG. 1 or 2, for example, the adhesive sheet may have the soft portion and the hard portion in the sheet surface of the adhesive sheet, and may be in the form of having the soft portion and the hard portion, and FIGS. 3 (A) and 3 (B). Alternatively, as shown in FIG. 5, the end face portion on at least one side of the pressure-sensitive adhesive sheet may have the hard portion. At this time, the sheet surface of the adhesive sheet may be a soft portion or a hard portion. Further, as shown in FIG. 5, the end face portion on at least one side of the pressure-sensitive adhesive sheet wound in a roll shape may have the hard portion.

The "base polymer" in the present invention means a resin forming the main component of the pressure-sensitive adhesive composition forming each layer. Although the specific content of the base polymer is not specified, as a guide, 50% by mass or more of the resin contained in the pressure-sensitive adhesive composition forming each layer, particularly 80% by mass or more, and 90% by mass or more among them. It is a resin that occupies (including 100% by mass). When there are two or more types of base polymers, the total amount thereof corresponds to the content.

The gel fraction of the soft portion is preferably less than 1% from the viewpoint of followability to the step portion, surface flatness, and the ability to alleviate distortion and deformation in the sheet, particularly 0.8. It is particularly preferably less than%, and more preferably less than 0.5%.
On the other hand, the gel fraction of the hard part is 40% or more from the viewpoint that it exerts a high cohesive force to enhance the adhesiveness and the adhesive surface does not become sticky even in a harsh environment such as high temperature and high humidity. It is preferable, and particularly preferably 45% or more, and particularly preferably 50% or more.

Further, if the glass transition temperature (Tg [S]) of the soft portion measured by a differential scanning calorimeter (DSC) is −70 to −10 ° C., appropriate flexibility and self-adhesiveness in the normal temperature range. The Tg of the soft portion is preferably −70 to −10 ° C., particularly preferably −65 ° C. or higher or −15 ° C. or lower, and particularly preferably −60 ° C. or higher or −20 ° C. or lower. ..
On the other hand, if the glass transition temperature (Tg [H]) of the hard portion measured by using a differential scanning calorimeter (DSC) is -60 to + 10 ° C., a high cohesive force can be obtained. Tg
Is preferably −60 ° C. to + 20 ° C., particularly preferably −55 ° C. or higher or + 15 ° C. or lower, and particularly preferably −50 ° C. or higher or + 10 ° C. or lower.
Further, if the difference (Tg [H] -Tg [S]) between the glass transition temperature (Tg [S]) of the soft portion and the glass transition temperature (Tg [H]) of the hard portion is 3 ° C. or higher, it is flexible. As a result of achieving both the contradictory quality of the cohesive force at a higher level, it is possible to achieve both the followability to the adherend surface at the time of bonding and the excellent foaming resistance after forming the laminated body, which is preferable. Therefore, the difference (Tg [H] -Tg [S]) in the glass transition temperature (Tg [H]) of the hard portion is preferably 3 ° C. or higher, particularly 5 ° C. or higher, and 7 ° C. or higher among them. Is particularly preferable.

(Asker hardness of soft part)
When the asker hardness (c) of the soft portion in the present adhesive sheet is 10 or more, it is preferable because an appropriate hardness related to cutting processability and ease of handling can be obtained. Further, when the asker hardness (c) is less than 60, appropriate flexibility and adhesion to the adherend can be obtained, which is preferable.
From this point of view, the asker hardness (c) of the soft portion in the present adhesive sheet is preferably 10 or more and less than 60, particularly preferably 15 or more or 55 or less, and particularly preferably 20 or more or 50 or less.

(Asker hardness of hard part)
When the asker hardness (d) of the hard portion in the present adhesive sheet is 40 or more, a high cohesive force can be obtained, and a laminated body having excellent shape stability and foaming reliability can be obtained. Further, when the asker hardness (d) is less than 90, it is preferable because it does not become too brittle and a laminated body having excellent impact resistance can be obtained.
From this point of view, the asker hardness (d) of the hard portion of the pressure-sensitive adhesive sheet is preferably 40 or more and less than 90, particularly preferably 43 or more or 88 or less, and particularly preferably 45 or more or 85 or less.

Further, in the present adhesive sheet, when the above (d)-(c) is 20 or more, both the followability to the adherend surface at the time of bonding and the excellent foaming resistance after forming a laminated body are compatible. It is preferable because it can be used.
From this point of view, in the present adhesive sheet, the difference ((d)-(c)) between the asker hardness (c) of the soft portion and the asker hardness (d) of the hard portion is preferably 20 or more, and above all, 20 or more. Alternatively, it is particularly preferably 80 or less, particularly preferably 25 or more or 75 or less.
In this pressure-sensitive adhesive sheet, in order to adjust the asker hardness (c) of the soft portion and the asker hardness (d) of the hard portion, the composition ratio of the cross-linking agent or the photopolymerization initiator may be adjusted in the composition or the manufacturing method, or the pressure-sensitive adhesive may be adjusted. The amount of light irradiation to the composition may be adjusted. However, the method is not limited to this method.

(180 ° peeling force of soft part)
When the 180 ° peeling force of the soft portion of the pressure-sensitive adhesive sheet is 3 N / cm or more, it has appropriate adhesion to the adherend at room temperature and is excellent in bonding workability, which is preferable.
From this point of view, the 180 ° peeling force of the soft portion in the present adhesive sheet is preferably 3 N / cm or more, particularly preferably 20 N / cm or less, and particularly preferably 4 N / cm or more or 15 N / cm or less. ..

(180 ° peeling force of hard part)
It is preferable that the 180 ° peeling force of the hard portion of the pressure-sensitive adhesive sheet is 5 N / cm or more because excellent foaming resistance and peeling resistance can be obtained.
From this point of view, the 180 ° peeling force of the hard portion of the pressure-sensitive adhesive sheet is preferably 5 N / cm or more, particularly preferably 25 N / cm or less, and particularly preferably 6 N / cm or more or 20 N / cm or less.

In this adhesive sheet, in order to adjust the 180 ° peeling force of the soft part and the hard part, the type and composition ratio of the cross-linking agent and the photopolymerization initiator are adjusted in the composition and the manufacturing method, and heating / addition at the time of bonding is performed. The pressure conditions and the light irradiation conditions after bonding may be adjusted. However, the method is not limited to this method.

(40 ° C holding power of soft part)
When the holding force of the soft portion of the present adhesive sheet at a temperature of 40 ° C. is less than 10 mm, excellent processability and storage stability can be obtained.
From this point of view, the holding force of the soft portion of the pressure-sensitive adhesive sheet at a temperature of 40 ° C. is preferably less than 10 mm, more preferably less than 8 mm, and even more preferably less than 5 mm.

(70 ° C holding power of soft part)
In addition, regarding the holding power of the soft part of this adhesive sheet at a temperature of 70 ° C., if the bonding surface shifts and the weight falls in less than 10 minutes, excellent adhesion to the adherend at the time of bonding is achieved. It is preferable because it can absorb unevenness.
From this point of view, regarding the holding force of the soft part of this adhesive sheet at a temperature of 70 ° C., it is preferable that the sticking surface shifts and the weight falls in less than 10 minutes, and in particular, the sticking surface shifts and the weight takes less than 8 minutes. It is more preferable that the weight is dropped, and it is more preferable that the sticking surface is displaced and the weight is dropped in less than 6 minutes.

(Retaining power of 40 ° C or 70 ° C of hard part)
The holding force of the hard portion of the present adhesive sheet at temperatures of 40 ° C. and 70 ° C. is preferably less than 1 mm, more preferably less than 0.7 mm, and less than 0.5 mm. Is even more preferable.
When the holding power of the hard portion of the pressure-sensitive adhesive sheet at temperatures of 40 ° C. and 70 ° C. is within the above range, a high cohesive force can be obtained, and shape stability and foaming resistance in a moist heat environment can be obtained.

<How to make this adhesive sheet>
The present adhesive sheet can be produced as follows.

(1) A light-transmissive member can be obtained by irradiating the light-curable adhesive sheet with light while concealing the soft portion with a light-impermeable member, that is, a light-impermeable member used for photo-curing. The portion covered with the above can be a soft portion, and the portion not covered with the light-transmitting member, that is, the portion irradiated with light can be photocured to form a hard portion.

(2) Further, if the end face portion of the adhesive sheet is irradiated with light and the portion other than the end face portion is not irradiated with light, the end face portion is made into a hard part and the other part is made into a soft part. Can be done.
For example, the end face portion of the adhesive sheet may be irradiated with light from a vertical direction, a horizontal direction, or an oblique vertical direction (assuming that the front and back surfaces of the sheet are arranged vertically and vertically), or the front and back surfaces of the adhesive sheet may be irradiated with light. A sheet that does not transmit light used for photocuring may be laminated on the side or both sides, and light may be irradiated from a vertical direction, a horizontal direction, or an oblique vertical direction. By irradiating with light in this way, it is possible to photo-cure the end face portion of the pressure-sensitive adhesive sheet. At this time, as the light-impermeable sheet used for photocuring, an ultraviolet absorber is kneaded into a release sheet using polyethylene terenaphthalate as a base polymer, a polyethylene terephthalate film or a polyolefin film, or ultraviolet rays are absorbed on the surface. It is particularly preferable to use a light-impermeable release sheet used for photocuring, such as a release sheet using a film coated with an agent.
The end face portion and its peripheral portion may become a hard portion when irradiated with light.

(3) Further, even if a pressure-sensitive adhesive sheet having a desired gel fraction is prepared separately and both are integrated, a soft portion and a hard portion can be formed in the pressure-sensitive adhesive sheet.

<Adhesive sheet X>
The present pressure-sensitive adhesive sheet can be formed by partially photo-curing using the following pressure-sensitive adhesive sheet X. However, the present invention is not limited to the use of the following adhesive sheet X to form the present adhesive sheet.

The pressure-sensitive adhesive sheet X has a gel fraction (a) of less than 1%, particularly less than 0.8%, of which 0.5, from the viewpoint of being able to exhibit hot melt properties in the state before photo-curing. It is particularly preferable that it is less than%.
Further, the adhesive sheet X can obtain a high cohesive force after photo-curing, and the gel fraction (b) after photo-curing is 40% or more from the viewpoint of obtaining foam resistance reliability in a moist heat environment. Is preferable, and particularly preferably 45% or more or 95% or less, and particularly preferably 50% or more or 90% or less.

In order to adjust the gel fraction (a) before photo-curing and the gel fraction (b) after photo-curing as described above, the composition ratio of the cross-linking agent or the photopolymerization initiator may be adjusted in the composition or manufacturing method. , The temperature at the time of processing and the amount of light irradiation may be adjusted. However, the method is not limited to this method.

<This adhesive composition>
A resin composition (hereinafter, referred to as “the present pressure-sensitive adhesive composition”) that can be suitably used for forming the pressure-sensitive adhesive sheet X will be described. However, this is just an example, and the present invention is not limited to this.

The pressure-sensitive adhesive composition is preferably a photocurable pressure-sensitive adhesive composition. Above all, a resin composition containing a (meth) acrylic copolymer (A), a cross-linking agent (B), and a photopolymerization initiator (C) is preferable.
However, as described above, the composition of the pressure-sensitive adhesive composition for forming the present pressure-sensitive adhesive sheet is limited as long as the gel fraction after attachment can be made different depending on the portion in the pressure-sensitive adhesive sheet. is not it.

Here, the present adhesive sheet has a hot-melt property that can be kept in a sheet shape under normal conditions, melts or flows when heated in an uncrosslinked state, and has a photo-curing property that can be photo-cured. It is particularly preferable to have an adhesive sheet.
If the sheet can be maintained in a normal state, it is easier to handle than a liquid adhesive, and the work of filling the liquid can be omitted, so that the productivity is particularly excellent.
Further, if it has an appropriate adhesiveness, that is, a property of adhering to an adherend in a short time with a light force (referred to as "tackiness") in a normal state, that is, near room temperature, positioning at the time of attachment is performed. Since it is easy and excellent in workability, it is preferable that it has tackiness in a normal state, that is, near room temperature, and it is more preferable that it has tackiness even in a relatively low temperature range of −5 ° C. to 20 ° C.
Further, if it has a hot melt property that melts or flows when heated, the adhesive can be filled by following the uneven portion such as a printing step by heating and softening or fluidizing. It can be filled without causing such problems.
Further, if it has photocurability, it can be firmly adhered by finally photocuring.
As described above, in order to produce an adhesive sheet that can be kept in a sheet shape under normal conditions, has a hot melt property that melts or flows when heated in an uncrosslinked state, and can be photocured. For example, in the case of a single-layer pressure-sensitive adhesive sheet, a single-layer pressure-sensitive adhesive sheet may be prepared from the pressure-sensitive adhesive composition (I) or (II) described below. On the other hand, in the case of a multi-layered pressure-sensitive adhesive sheet, for example, a two-kind two-layer structure in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition (I) or (II) and a pressure-sensitive adhesive layer made of another pressure-sensitive adhesive composition are laminated, or A two-kind three-layer structure in which an adhesive layer composed of the adhesive composition (I) or (II) is arranged on the front and back via an intermediate resin layer, or an adhesive layer composed of the adhesive composition (I) or (II). , A three-kind three-layer structure in which an intermediate layer made of an intermediate resin composition and an adhesive layer made of another pressure-sensitive adhesive composition are laminated in this order can be mentioned.
However, the pressure-sensitive adhesive composition for forming the present pressure-sensitive adhesive sheet is not limited to the pressure-sensitive adhesive composition (I) or (II).

<Adhesive composition (I)>
The pressure-sensitive adhesive composition (I) contains an acrylic copolymer (A1) made of a graft copolymer having a macromonomer as a branch component, a cross-linking agent (B1), and a photopolymerization initiator (C1). Examples of the resin composition to be used.

(Acrylic copolymer (A1))
The acrylic copolymer (A1) as the base polymer may be a graft copolymer having a macromonomer as a branch component.

(Stem component)
The stem component of the acrylic copolymer (A1) is preferably composed of a copolymer component containing a repeating unit derived from (meth) acrylic acid ester.

The glass transition temperature of the copolymer constituting the stem component of the acrylic copolymer (A1) is preferably −70 to 0 ° C.
At this time, the glass transition temperature of the copolymer component constituting the stem component refers to the glass transition temperature of the polymer obtained by copolymerizing only the monomer component constituting the stem component of the acrylic copolymer (A1). .. Specifically, it means a value calculated by the Fox calculation formula from the glass transition temperature and the composition ratio of the polymer obtained from the homopolymer of each component of the copolymer.
The Fox calculation formula is a calculated value obtained by the following formula, and is a polymer handbook [Polymer HandBook, J. Mol. It can be obtained by using the value described in Brandrup, Interscience, 1989].
1 / (273 + Tg) = Σ (Wi / (273 + Tgi))
[In the formula, Wi indicates the weight fraction of the monomer i, and Tgi indicates the Tg (° C.) of the homopolymer of the monomer i. ]

The glass transition temperature of the copolymer component constituting the stem component of the acrylic copolymer (A1) is the flexibility of the pressure-sensitive adhesive composition (I) at room temperature and the pressure-sensitive adhesive composition on the adherend. Since the wettability of (I), that is, the adhesiveness is affected, the glass transition temperature of the pressure-sensitive adhesive composition (I) is from −70 ° C. to obtain appropriate adhesiveness (tackiness) at room temperature. The temperature is preferably 0 ° C. or higher, particularly preferably −65 ° C. or higher or −5 ° C. or lower, and particularly preferably −60 ° C. or higher or −10 ° C. or lower.

However, even if the glass transition temperature of the copolymer component is the same, the viscoelasticity can be adjusted by adjusting the molecular weight. For example, by reducing the molecular weight of the copolymer component, it can be made more flexible.

Examples of the (meth) acrylic acid ester monomer contained in the stem component of the acrylic copolymer (A1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and isopropyl (meth) acrylate. n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl ( Meta) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate , Decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, Isobornyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO modified (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl ( Examples thereof include meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and benzyl (meth) acrylate. These include hydroxyl group-containing (meth) acrylates such as hydroxyethyl (meth) acrylates, hydroxypropyl (meth) acrylates, hydroxybutyl (meth) acrylates, and glycerol (meth) acrylates having hydrophilic groups and organic functional groups, and (meth) acrylates. ) Acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxypropylphthalic acid Acid, 2- (meth) acryloyloxyethyl maleic acid, 2- (meth) acryloyloxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, fumal Carboxyl group-containing monomers such as acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride, glycidyl (meth) acrylate, α-ethylacrylic acid. Epoxy group-containing monomers such as glycidyl and (meth) acrylic acid 3,4-epoxybutyl, amino group-containing (meth) acrylic acid ester-based monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, (meth). ) Acrylate, N-t-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, maleic acid amide, maleimide, etc. It is also possible to use a monomer containing an amide group, a heterocyclic basic monomer such as vinylpyrrolidone, vinylpyridine, vinylcarbazole and the like.
In addition, styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, acrylonitrile, methacrylonitonyl, vinyl acetate, vinyl propionate, alkyl vinyl ether, hydroxyalkyl vinyl ether, and alkyl, which can be copolymerized with the above acrylic monomer and methacrylic monomer. Various vinyl monomers such as vinyl monomers can also be appropriately used.

Further, the stem component of the acrylic copolymer (A1) preferably contains a hydrophobic (meth) acrylate monomer and a hydrophilic (meth) acrylate monomer as constituent units.
If the stem component of the acrylic copolymer (A1) is composed of only hydrophobic monomers, there is a tendency for moist heat bleaching. Therefore, it is preferable to introduce hydrophilic monomers into the stem components to prevent moist heat bleaching. ..
Specifically, as the stem component of the acrylic copolymer (A1), a hydrophobic (meth) acrylate monomer, a hydrophilic (meth) acrylate monomer, and a polymerizable functional group at the end of the macromonomer are included. Examples thereof include copolymer components obtained by random copolymerization.

Here, as the hydrophobic (meth) acrylate monomer, an alkyl ester having no polar group (excluding methyl acrylate) is preferable, and for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and the like. sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) Acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (Meta) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclo Examples thereof include pentenyloxyethyl (meth) acrylicate and methylmethacrylate.
Examples of the hydrophobic vinyl monomer include vinyl acetate, styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, and an alkyl vinyl monomer.

As the hydrophilic (meth) acrylate monomer, methyl acrylate and an ester having a polar group are preferable, and for example, methyl acrylate, (meth) acrylic acid, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, and the like. Hydroxyl-containing (meth) acrylates such as hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and glycerol (meth) acrylate, (meth) acrylic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (Meta) Acryloyloxypropyl Hexahydrophthalic Acid, 2- (Meta) Acryloyloxyethylphthalic Acid, 2- (Meta) Acryloyloxypropylphthalic Acid, 2- (Meta) Acryloyloxyethyl Maleic Acid, 2- (Meta) Acryloyl Carboxyl groups such as oxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate, etc. Containing monomer, acid anhydride group-containing monomer such as maleic anhydride and itaconic anhydride, epoxy group-containing monomer such as glycidyl (meth) acrylate, glycidyl α-ethylacrylate, and 3,4-epoxybutyl (meth) acrylate. , Acrylate polyalkylene glycol (meth) acrylate such as methoxypolyethylene glycol (meth) acrylate, N, N-dimethylacrylamide, hydroxyethylacrylamide and the like.

(Branch component: macromonomer)
It is preferable that the acrylic copolymer (A1) has a macromonomer introduced as a branch component of the graft copolymer and contains a repeating unit derived from the macromonomer.
The macromonomer is a polymer monomer having a polymerizable functional group at the terminal and a high molecular weight skeleton component.

The glass transition temperature (Tg) of the macromonomer is preferably higher than the glass transition temperature of the copolymer component constituting the acrylic copolymer (A1).
Specifically, since the glass transition temperature (Tg) of the macromonomer affects the heating and melting temperature (hot melt temperature) of the pressure-sensitive adhesive composition (I), the glass transition temperature (Tg) of the macromonomer is from 30 ° C. to 30 ° C. The temperature is preferably 120 ° C. or higher, more preferably 40 ° C. or higher or 110 ° C. or lower, and further preferably 50 ° C. or higher or 100 ° C. or lower.
With such a glass transition temperature (Tg), by adjusting the molecular weight, excellent processability and storage stability can be maintained, and the temperature can be adjusted to hot melt at around 80 ° C.
The glass transition temperature of the macromonomer refers to the glass transition temperature of the macromonomer itself and can be measured with a differential scanning calorimeter (DSC) (heating rate: 5 ° C./min, baseline shift variation). Measure Tg from the point).

Further, in a room temperature state, it is possible to maintain a state in which the branch components are attracted to each other and physically cross-linked as a pressure-sensitive adhesive composition, and the physical cross-linking is released by heating to an appropriate temperature. In order to obtain fluidity, it is also preferable to adjust the molecular weight and content of the macromonomer.
From this point of view, the macromonomer is preferably contained in the acrylic copolymer (A1) in a proportion of 5% by mass to 30% by mass, particularly 6% by mass or more or 25% by mass or less, and 8% by mass among them. It is preferably more than or less than 20% by mass.
The number average molecular weight of the macromonomer is preferably 500 or more and less than 8000, and more preferably 800 or more or less than 7500, and more preferably 1000 or more or less than 7000.
As the macromonomer, a generally manufactured one (for example, a macromonomer manufactured by Toagosei Co., Ltd.) can be appropriately used.

The high molecular weight skeleton component of the macromonomer is preferably composed of an acrylic polymer or a vinyl polymer.
Examples of the high molecular weight skeleton component of the macromonomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) Acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (Meta) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate , 3,5,5-trimethylcyclohexaneacrylate, p-cumylphenol EO modified (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, Benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, (meth) acrylic acid, glycidyl (meth) acrylate, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (meth) acrylic nitrile, alkoxyalkyl (meth) ) Acrylate, (meth) acrylate monomers such as alkoxypolyalkylene glycol (meth) acrylate, styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, alkyl vinyl monomers, vinyl acetate, alkyl vinyl ether, hydroxyalkyl vinyl ether and the like. Various vinyl monomers and the like can be mentioned, and these can be used alone or in combination of two or more.

Examples of the terminal polymerizable functional group of the macromonomer include a methacryloyl group, an acryloyl group, and a vinyl group.

(Crosslinking agent (B1))
As the cross-linking agent (B1), a cross-linking agent having two or more cross-linking groups such as an epoxy group, an isocyanate group, an oxetane group, a silanol group, and a (meth) acryloyl group can be appropriately selected. Among them, polyfunctional (meth) acrylate having two or more (meth) acryloyl groups, especially three or more, and having an epoxy group, an isocyanate group, and a silanol group (meth) in terms of reactivity and the strength of the obtained cured product. ) Acrylate is preferred.

By cross-linking the cross-linking agent (B1) in the adhesive material after laminating and integrating the image display device components, the sheet exhibits high cohesive force in a high temperature environment instead of losing the hot melt property. , Excellent foam resistance and reliability can be obtained.

Examples of such (meth) acrylates include 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, glycering lysidyl ether di (meth) acrylate, 1, 6-Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, bisphenol A polyethoxydi (meth) acrylate, bisphenol A polyalkoxydi (meth) acrylate , Bisphenol F polyalkoxydi (meth) acrylate, polyalkylene glycol di (meth) acrylate, trimethylolpropanetrioxyethyl (meth) acrylate, ε-caprolactone-modified tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, Pentaerythritol tri (meth) acrylate, propoxylated pentaerythritol tri (meth) acrylate, ethoxylated pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol Tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) acrylate, tris (acryloxyethyl) isocyanurate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, di. Pentaerythritol Penta (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol penta (meth) acrylate, hydroxyvivariate neopentylglycol di (meth) acrylate, hydroxyvivariate neopenglycol ε-caprolactone In addition to UV-curable polyfunctional monomers such as di (meth) acrylates, trimetylol propantri (meth) acrylates, alkoxylated trimetylol propantri (meth) acrylates, and ditrimethylolpropantetra (meth) acrylates as additives. Polyfunctional acrylic oligomers such as polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, and isocyanate (meth) acrylate. G, 1,1- (bis (meth) acryloyloxymethyl) ethyl isocyanate, 2- (2- (meth) acryloyloxyethyloxy) ethyl isocyanate, glycidyl (meth) acrylate, hydroxyethyl acrylate glycidyl ether, hydroxypropyl (meth) ) Acrylo glycidyl ether, hydroxybutyl (meth) acrylate glycidyl ether and the like can be mentioned.

Among the above, a polyfunctional monomer or oligomer containing a polar functional group such as a hydroxyl group is preferable from the viewpoint of improving the adhesion to the adherend and the effect of suppressing moist heat bleaching.
Among them, it is preferable to use a polyfunctional (meth) acrylic acid ester having a hydroxyl group or a carboxyl group.
Therefore, from the viewpoint of preventing moist heat bleaching, it is preferable to contain a hydrophobic acrylate monomer and a hydrophilic acrylate monomer as the stem component of the acrylic copolymer (A1), that is, the graft copolymer. Furthermore, it is preferable to use a polyfunctional (meth) acrylic acid ester having a hydroxyl group as the cross-linking agent (B1).

The content of the cross-linking agent (B1) is not particularly limited. As a guide, the ratio of 0.5 to 20 parts by mass, especially 1 part by mass or more or 15 parts by mass or less, and 2 parts by mass or more or 10 parts by mass or less, based on 100 parts by mass of the acrylic copolymer (A1). Is preferable.
By containing the cross-linking agent (B1) in the above range, it is possible to achieve both the shape stability of the present pressure-sensitive adhesive sheet in the uncross-linked state and the foaming reliability of the pressure-sensitive adhesive material after cross-linking. However, this range may be exceeded in balance with other factors.

(Photopolymerization Initiator (C1))
The photopolymerization initiator (C1) functions as a reaction initiation aid in the cross-linking reaction of the above-mentioned cross-linking agent (B1).
As the photopolymerization initiator, currently known ones can be appropriately used. Of these, a photopolymerization initiator that is sensitive to ultraviolet rays having a wavelength of 380 nm or less is preferable from the viewpoint of ease of control of the crosslinking reaction.
On the other hand, a photopolymerization initiator that is sensitive to light having a wavelength longer than 380 nm is preferable because the sensitive light easily reaches the deep part of the pressure-sensitive adhesive sheet.

Photopolymerization initiators are roughly classified into two types according to the radical generation mechanism: a cleavage-type photopolymerization initiator that can generate radicals by cleaving and decomposing a single bond of the photopolymerization initiator itself, and a photo-excited initiator. And the hydrogen donor in the system form an excitation complex, which is roughly classified into a hydrogen abstraction type photopolymerization initiator capable of transferring the hydrogen of the hydrogen donor.

Of these, the cleavage-type photopolymerization initiator decomposes to another compound when a radical is generated by light irradiation, and once excited, it loses its function as a reaction initiator. Therefore, it is preferable because it does not remain as an active species in the pressure-sensitive adhesive after the cross-linking reaction is completed and there is no possibility of causing unexpected photodegradation or the like in the pressure-sensitive adhesive material.
On the other hand, the hydrogen abstraction type photopolymerization initiator does not generate a decomposition product like a cleaved type photopolymerization initiator during a radical generation reaction by irradiation with active energy rays such as ultraviolet rays, so that it is unlikely to become a volatile component after the reaction is completed, and is subject to exposure. It is useful in that it can reduce damage to the body.

Examples of the cleavage-type photoinitiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-. On, 1- (4- (2-hydroxyethoxy) phenyl) -2-hydroxy-2-methyl-1-propane-1-one, 2-hirodoxy-1- [4- {4- (2-hydroxy-2) -Methyl-propionyl) benzyl} phenyl] -2-methyl-propane-1-one, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone), phenylglycoxylic Methyl 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butane-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1- On, 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, bis (2,4,6-trimethylbenzoyl)- Examples thereof include phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and derivatives thereof.

Examples of the hydrogen abstraction type photoinitiator include benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4- (meth). Acryloyloxybenzophenone, Methyl 2-benzoylbenzoate, Methyl benzoylate, Bis (2-phenyl-2-oxoacetic acid) Oxybisethylene 4- (1,3-Acryloyl-1,4,7,10,13- Pentaoxotridecyl) Benzophenone, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone and its derivatives And so on.
However, the photopolymerization initiator is not limited to the substances listed above. Any one of the cleavage type photopolymerization initiator and the hydrogen extraction type photopolymerization initiator mentioned above may be used, or two or more kinds may be used in combination.

The content of the photopolymerization initiator (C1) is not particularly limited. As a guide, 0.1 to 10 parts by mass, especially 0.5 parts by mass or more or 5 parts by mass or less, and 1 part by mass or more or 3 parts by mass or less, based on 100 parts by mass of the acrylic copolymer (A1). It is preferable to contain it in the proportion of.
By setting the content of the photopolymerization initiator (C1) in the above range, it is possible to obtain an appropriate reaction sensitivity to active energy rays.

(Other ingredients)
The pressure-sensitive adhesive composition (I) may contain a known component contained in a normal pressure-sensitive adhesive composition as a component other than the above. For example, if necessary, a tackifier resin, an antioxidant, a light stabilizer, a metal inactivating agent, an antiaging agent, a hygroscopic agent, a polymerization inhibitor, an ultraviolet absorber, a rust preventive, and a silane coupling agent. , Various additives such as inorganic particles can be appropriately contained.
Further, if necessary, a reaction catalyst (tertiary amine compound, quaternary ammonium compound, tin laurate compound, etc.) may be appropriately contained.

<Adhesive composition (II)>
As the pressure-sensitive adhesive composition (II), a monomer a having a glass transition temperature (Tg) of less than 0 ° C., a monomer b having a glass transition temperature (Tg) of 0 ° C. or higher and lower than 80 ° C., and a glass transition temperature (Tg) of 80. Monomer c at ° C. or higher is copolymerized at a molar ratio of a: b: c = 10-40: 90 to 35: 0 to 25, and has a weight average molecular weight of 50,000 to 400,000 (meth) acrylic acid ester copolymer weight. Examples thereof include a resin composition containing a (meth) acrylic copolymer (A2) containing a coalesced or vinyl copolymer, a cross-linking agent (B2), and a photopolymerization initiator (C2).
For the number average molecular weight and the weight average molecular weight, gel permeation chromatography (GPC) is used, and converted values using polystyrene as a standard substance are adopted.

((Meta) acrylic copolymer (A2))
The (meth) acrylic copolymer (A2) as the base polymer is preferably a (meth) acrylic acid ester copolymer or a vinyl copolymer.

The (meth) acrylic acid ester copolymer or vinyl copolymer preferably has a weight average molecular weight of 50,000 to 400,000, particularly 60,000, from the viewpoint of achieving both shape retention and hot melt properties at room temperature. It is more preferably 350,000 or less, and more preferably 70,000 or more or 300,000 or less.

The acrylic acid ester-based copolymer has physical properties such as glass transition temperature (Tg) and molecular weight by appropriately selecting the type, composition ratio, polymerization conditions, etc. of the acrylic monomer and methacrylic monomer used to adjust the copolymer. Can be adjusted as appropriate.
At this time, examples of the acrylic monomer constituting the acrylic acid ester copolymer include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate and the like as main raw materials.
In addition to these, a (meth) acrylic monomer having various functional groups may be copolymerized with the above-mentioned acrylic monomer depending on the purpose of imparting cohesive force or polarity.
Examples of the (meth) acrylic monomer having the functional group include methyl methacrylate, methyl acrylate, hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, N-substituted acrylamide, acrylonitrile, methacrylic nitrile, fluoroalkyl acrylate, and organosiloxy group. Acrylate and the like can be mentioned.

On the other hand, examples of the vinyl copolymer include vinyl acetate that can be copolymerized with the above acrylic monomer and methacrylic monomer, and vinyl copolymers obtained by appropriately polymerizing various vinyl monomers such as alkyl vinyl ether and hydroxyalkyl vinyl ether. ..

The (meth) acrylic copolymer (A2) of this pressure-sensitive adhesive sheet includes a monomer a having a glass transition temperature (Tg) of less than 0 ° C. and a monomer b having a glass transition temperature (Tg) of 0 ° C. or higher and lower than 80 ° C. , A (meth) acrylic acid ester obtained by copolymerizing a monomer c having a glass transition temperature (Tg) of 80 ° C. or higher at a molar ratio of a: b: c = 10 to 40: 90 to 35: 0 to 25. It is preferably a polymer or a vinyl copolymer.
At this time, each glass transition temperature (Tg) of the monomers a, b, and c means each glass transition temperature (Tg) when a polymer is prepared from the monomer (homorylated).

The monomer a is preferably, for example, a (meth) acrylic acid ester monomer having an alkyl group structure having a side chain having 4 or more carbon atoms.
At this time, the side chain having 4 or more carbon atoms may be a straight chain or a branched carbon chain.
More specifically, the monomer a is a (meth) acrylic acid ester monomer having a linear alkyl group structure having 4 to 10 carbon atoms, or has a branched alkyl group structure having 6 to 18 carbon atoms (). It is preferably a meta) acrylic acid ester monomer.

Here, as the "(meth) acrylic acid ester monomer having a linear alkyl group structure having 4 to 10 carbon atoms", n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n- Decyl acrylate and the like can be mentioned.
On the other hand, examples of the "(meth) acrylic acid ester monomer having a branched alkyl group structure having 6 to 18 carbon atoms include 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-methylhexyl acrylate, isooctyl acrylate, and isononyl acrylate. Examples thereof include isodecyl acrylate and isodecyl methacrylate.

The monomer b has a (meth) acrylic acid ester monomer having 4 or less carbon atoms, a (meth) acrylic acid ester monomer having a cyclic skeleton in the side chain, a vinyl monomer having 4 or less carbon atoms, or a cyclic skeleton in the side chain. It is preferably a vinyl monomer.
Above all, it is particularly preferable that the monomer b is a vinyl monomer having 4 or less carbon atoms in the side chain.

Here, examples of the "(meth) acrylic acid ester monomer having 4 or less carbon atoms" include methyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl methacrylate, and t-. Butyl acrylate, isobutyl acrylate, isobutyl methacrylate and the like can be mentioned.
Examples of the "(meth) acrylic acid ester monomer having a cyclic skeleton in the side chain" include isobornyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, tetrahydrofurfuryl methacrylate, benzyl acrylate, and benzyl methacrylate. , Phenoxyethyl acrylate, Phenoxyethyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 3,3,5-trimethylcyclohexanol acrylate, Cyclic trimethylolpropaneformal acrylate, 4-ethoxylated cumylphenol acrylate, Dicyclopentenyl Examples thereof include oxyethyl acrylate, dicyclopentenyl oxyethyl methacrylate, and dicyclopentenyl acrylate.
Examples of the "vinyl monomer having 4 or less carbon atoms" include vinyl acetate, vinyl propionate, vinyl butyrate, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether and the like.
Examples of the "vinyl monomer having a cyclic skeleton in the side chain" include styrene, cyclohexyl vinyl ether, norbornyl vinyl ether, norbornenyl vinyl ether and the like. Of these, a vinyl monomer having 4 or less carbon atoms in the side chain or an acrylic acid ester monomer having 4 or less carbon atoms in the side chain is particularly preferable.

The monomer c is preferably a (meth) acrylic acid ester monomer having 1 or less carbon atoms in the side chain, or a (meth) acrylic acid ester monomer having a cyclic skeleton in the side chain.
Here, examples of the "(meth) acrylic acid ester monomer having 1 or less carbon atoms in the side chain" include methyl methacrylate, acrylic acid, and methacrylic acid.
Examples of the "(meth) acrylic acid ester monomer having a cyclic skeleton in the side chain" include isobornyl methacrylate, 3,3,5-trimethylcyclohexylmethacrylate, dicyclopentanylacryllate, dicyclopentanylmethacrylate, and dicyclopentanylmethacrylate. Cyclopentenyl methacrylate and the like can be mentioned.

The (meth) acrylic copolymer (A2) copolymerizes with the monomer a, the monomer b, and the monomer c at a molar ratio of a: b: c = 10 to 40: 90 to 35: 0 to 25. If it contains a (meth) acrylic acid ester copolymer or a vinyl copolymer, the peak of Tan δ can be adjusted to 0 to 20 ° C., and it has a sheet-like shape in a normal state, that is, in a room temperature state. Can be retained. Moreover, it is possible to develop adhesiveness (referred to as "tackiness") to the extent that it can be peeled off. Further, when heated to a temperature at which hot melt is possible, fluidity is exhibited, and it is possible to follow the stepped portion of the bonded surface and fill every corner.
Therefore, from this point of view, the molar ratio of the monomer a, the monomer b, and the monomer c in the (meth) acrylic acid ester copolymer or the vinyl copolymer constituting the (meth) acrylic copolymer (A2) is , A: b: c = 10 to 40:90 to 35:00 to 25, particularly 13 to 40:87 to 35:00 to 23, and among them, 15 to 40:85 to 38: 2 to 20. Is preferable.
Further, from the same viewpoint as above, the monomer a, the monomer b, and the monomer c in the (meth) acrylic acid ester copolymer or the vinyl copolymer constituting the (meth) acrylic copolymer (A2) The molar ratio is preferably b>a> c.

(Crosslinking agent (B2))
By cross-linking the cross-linking agent (B2) in the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet exhibits high cohesive force in a high-temperature environment, and excellent foaming resistance can be obtained.

As such a cross-linking agent (B2), a cross-linking agent having two or more cross-linking groups such as an epoxy group, an isocyanate group, an oxetane group, a silanol group, and a (meth) acryloyl group can be appropriately selected. Among them, polyfunctional (meth) acrylate having two or more (meth) acryloyl groups, especially three or more, and having an epoxy group, an isocyanate group, and a silanol group (meth) in terms of reactivity and the strength of the obtained cured product. ) Acrylate is preferred.

Examples of such (meth) acrylates include 1,4-butanediol di (meth) acrylate, glycerindi (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (). Meta) acrylate, tricyclodecanedimethanol di (meth) acrylate, bisphenol A polyethoxydi (meth) acrylate, bisphenol A polypropoxydi (meth) acrylate, bisphenol F polyethoxydi (meth) acrylate, ethylene glycol di (meth) acrylate, tri. Methylolpropantrioxyethyl (meth) acrylate, ε-caprolactone-modified tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propoxylated pentaerythritol tri (meth) acrylate, pentaacrylate Elythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) Acrylate, Tris (acryloxyethyl) isocyanurate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol penta Di (meth) acrylate, di (meth) acrylate of ε-caprolactone adduct of (meth) acrylate, neopentyl glycol di (meth) acrylate of hydroxyvivariate, neopen glycol of hydroxyvivariate, trimethylolpropane tri (meth) acrylate, trimethylolpropane In addition to ultraviolet curable polyfunctional monomers such as polyethoxytri (meth) acrylate and ditrimethylolpropanetetra (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and polyether (meth) Polyfunctional acrylic oligomers such as meta) acrylates, isocyanate (meth) acrylates, 1,1- (bis (meth) acryloyloxymethyl) ethyl isocyanates, 2- (2- (meth) acryloylo). Examples thereof include xyethyloxy) ethyl isocyanate, glycidyl (meth) acrylate, hydroxyethyl acrylate glycidyl ether, hydroxypropyl (meth) acrylate glycidyl ether, and hydroxybutyl (meth) acrylate glycidyl ether.

Among the above, a polyfunctional monomer or oligomer containing a polar functional group is preferable from the viewpoint of improving the adhesion to the adherend, heat resistance, and the effect of suppressing moist heat bleaching. Among them, it is preferable to use a polyfunctional (meth) acrylic acid ester having an isocyanul ring skeleton.

The content of the cross-linking agent (B2) is not particularly limited. As a guide, 0.5 to 20 parts by mass, particularly 1 part by mass or more or 15 parts by mass or less, and 2 parts by mass or more or 10 parts by mass among them, with respect to 100 parts by mass of the (meth) acrylic copolymer (A2). The ratio is preferably as follows.
By containing the cross-linking agent (B2) in the above range, it is possible to achieve both the shape stability of the present pressure-sensitive adhesive sheet in the uncross-linked state and the foaming reliability of the pressure-sensitive adhesive sheet after cross-linking. However, this range may be exceeded in balance with other factors.

(Photopolymerization Initiator (C2))
The photopolymerization initiator (C2) functions as a reaction initiation aid in the cross-linking reaction of the above-mentioned cross-linking agent (B2), and the description of the above-mentioned photopolymerization initiator (C1) is appropriately used. Can be used.

The content of the photopolymerization initiator (C2) is not particularly limited. As a guide, 0.1 to 10 parts by mass, especially 0.5 parts by mass or more or 5 parts by mass or less, and 1 part by mass or more or 3 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A2). It is preferably contained in a proportion of parts by mass or less.
By setting the content of the photopolymerization initiator (C2) in the above range, it is possible to obtain an appropriate reaction sensitivity to active energy rays.

(Other ingredients)
The pressure-sensitive adhesive composition (II) may contain a known component contained in a normal pressure-sensitive adhesive composition as a component other than the above. For example, if necessary, a tackifier resin, an antioxidant, a light stabilizer, a metal inactivating agent, an antiaging agent, a hygroscopic agent, a polymerization inhibitor, an ultraviolet absorber, a rust preventive, and a silane coupling agent. , Various additives such as inorganic particles can be appropriately contained.
Further, if necessary, a reaction catalyst (tertiary amine compound, quaternary ammonium compound, tin laurate compound, etc.) may be appropriately contained.

<Method of manufacturing adhesive sheet X>
The method for producing the pressure-sensitive adhesive sheet X is a solution coating method in which the pressure-sensitive adhesive compositions (I) and (II) prepared by a known method are dissolved in a solvent and coated, or the pressure-sensitive adhesive composition is heated and melted. Examples include a hot melt coating method for coating. However, as long as the desired pressure-sensitive adhesive sheet can be obtained, the present invention is not particularly limited and can be produced by a known method.
In the above-mentioned pressure-sensitive adhesive compositions (I) and (II), when molding a thin film product having a thickness of 50 μm or less, it is preferable to adopt a solution coating method from the viewpoint of ease of thickness control. On the other hand, when molding an adhesive sheet having a thickness of 50 μm or more, it is preferable to adopt a hot melt coating method because of environmental pollution and ease of thick film molding.

<Laminate structure>
The present adhesive sheet may be a sheet composed of a single layer or a multilayer sheet in which two or more layers are laminated.

When the present pressure-sensitive adhesive sheet is used as a multi-layered transparent double-sided pressure-sensitive adhesive material, specifically, the laminated structure includes a two-kind two-layer structure in which the present pressure-sensitive adhesive composition and another pressure-sensitive adhesive resin composition are laminated, or an intermediate structure. A two-kind, three-layer structure in which the present pressure-sensitive adhesive composition is arranged on the front and back via a resin layer, or the present pressure-sensitive adhesive composition, an intermediate resin composition, and another pressure-sensitive adhesive resin composition are laminated in this order. Examples include 3 types and 3 layers. Above all, it is preferable to form the outermost layer from the present pressure-sensitive adhesive composition, for example, the above-mentioned pressure-sensitive adhesive compositions (I) and (II).
Further, the present pressure-sensitive adhesive composition and another pressure-sensitive adhesive resin composition are formed into a sheet shape on different release films or image display device constituent members, and both pressure-sensitive adhesive surfaces are laminated to obtain the present pressure-sensitive adhesive sheet. Alternatively, the present pressure-sensitive adhesive composition, the intermediate resin composition, and the pressure-sensitive adhesive resin composition may be co-extruded in this order to obtain the present pressure-sensitive adhesive sheet of two types and three layers. Further, the present pressure-sensitive adhesive composition or another pressure-sensitive adhesive resin composition may be laminated on the front and back surfaces of the intermediate resin layer to obtain the present pressure-sensitive adhesive sheet.
Further, for example, even if the pressure-sensitive adhesive sheet has a base material having an pressure-sensitive adhesive layer (referred to as “the main pressure-sensitive adhesive layer”) formed of the present pressure-sensitive adhesive composition, the base material does not have a base material. It may be an adhesive sheet. Further, it may be a double-sided pressure-sensitive adhesive sheet having the main adhesive layer on both the upper and lower sides, or a single-sided pressure-sensitive adhesive sheet having the main pressure-sensitive adhesive layer only on the upper and lower one side.

<Thickness>
The thickness of the pressure-sensitive adhesive sheet is preferably 250 μm or less in the maximum thickness portion from the viewpoint of not hindering the thinning of the image display device. In other words, the present adhesive sheet may be a sheet having a uniform thickness or a non-uniform sheet having a partially different thickness, and in the case of a sheet having a non-uniform thickness, it is the thickest. It is preferable that the thickness of the large portion is 250 μm or less.
Further, from the viewpoint of not hindering the adhesion to the adherend and the impact absorption, the thickness of the maximum thickness portion is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more.

<Use>
This adhesive sheet can be used as it is, but it can also be used as follows. However, the method of using this adhesive sheet is not limited.

(Adhesive sheet laminate)
The present adhesive sheet can be provided, for example, as an adhesive sheet laminate having a structure in which a release film is laminated on one side or both sides of the present adhesive sheet.
At this time, the adhesive sheet may have the soft portion and the hard portion in the sheet surface, for example, as shown in FIGS. 1 or 2, and may be in the form of having the soft portion and the hard portion, and FIGS. 3 (A) and 3 (B). As shown in the above, the end face portion on at least one side of the pressure-sensitive adhesive sheet may have the hard portion. At this time, the entire surface of the end face portion may be the hard portion, or a part of the end face portion may be the hard portion. Further, there may be a hard portion in the end face and the in-plane.
As shown in FIGS. 4A and 4B, if the end face portion of the adhesive sheet is a hard portion, the exposed end face portion becomes sticky even in a harsh environment such as high temperature and high humidity. Since there is no such thing, it can be stored favorably.

(Laminate for configuring this image display device)
When the adhesive sheet has the soft portion and the hard portion in the sheet surface, for example, an image having a configuration in which two constituent members for an image display device are laminated via the adhesive sheet. A display device configuration laminate (hereinafter referred to as "the image display device configuration laminate") can be produced and provided.

In the laminated body for configuring an image display device, for example, a component for an image display device having a light-transmitting portion and a light-transmitting portion on a bonded surface and another component for an image display device are attached to the pressure-sensitive adhesive sheet X. The pressure-sensitive adhesive sheet X can be partially photo-cured by irradiating the pressure-sensitive adhesive sheet X with light via the former image display device component.

As an example of the laminate for configuring the image display device, in addition to the laminate composed of the protective panel / the adhesive sheet / polarizing film, for example, the image display panel / the adhesive sheet / touch panel, the image display panel / the adhesive sheet / protection. Examples of configurations such as a panel, an image display panel / main adhesive sheet / touch panel / main adhesive sheet / protective panel, polarizing film / main adhesive sheet / touch panel, polarizing film / main adhesive sheet / touch panel / main adhesive sheet / protective panel are given. Can be done.
The protective panel and the image display panel may be those in which the touch panel sensor is incorporated in the protective panel or the image display panel itself.

(This image display device)
An image display device (hereinafter referred to as "the image display device") can also be configured by using the adhesive sheet or the laminated body for constructing the image display device.

That is, the present image display device includes at least two image display device components facing each other, and at least one image display device component has an image display device having a light opaque portion and a light transmission portion on the bonded surface. In an image display device having a structure in which the space between the two image display device components is filled with an adhesive sheet, the gel content at a position in contact with the light transmitting portion of the adhesive sheet is 40%. The image display device can be configured as described above, wherein the gel content at the position in contact with the light opaque portion is less than 1%.

In the above-mentioned laminate for configuring the image display device and the image display device, a portion that does not transmit light having a wavelength required for photocuring, such as a printed portion around the screen (referred to as a “light opaque portion” in the present invention). A component for an image display device having a portion (referred to as a "light transmission portion" in the present invention) that transmits light having a wavelength required for photocuring on the bonded surface, and a component for another image display device. At the time of bonding, the gel fraction at the position in contact with the light transmissive portion is set to less than 1%, and the gel fraction at the position in contact with the light transmissive portion is set to 40% or more, so that the light impervious portion presses. The stress received by the light can be relaxed, the strain generated in this portion can be reduced, and the adherends can be firmly adhered to each other with a high cohesive force.

The gel fraction at the position in contact with the light opaque portion is particularly preferably less than 1%, and more preferably less than 0.8%.
On the other hand, the gel fraction at the position in contact with the light transmitting portion is particularly preferably 40% or more, and more preferably 45% or more.

An example of a preferable manufacturing method of this image display device will be described.
First, the pressure-sensitive adhesive sheet X is heated and hot-melted, and the image display device component 1 having the printing unit (1) and the image display device component 3 are laminated via the pressure-sensitive adhesive sheet X. At this stage, since the adhesive sheet X is moderately soft, it is possible to sufficiently follow the step while maintaining the storage stability.
Next, light such as ultraviolet rays is irradiated from the outside of the component 1 for the image display device. Then, since the printing unit (1) shields the light, the light does not reach the portion in contact with the printing unit (1), or the light that reaches is significantly limited, while the light without the printing unit (1) is present. Light sufficiently reaches the portion in contact with the transmissive portion (3), the cross-linking reaction of this portion proceeds and photocuring can be performed, and excellent peeling resistance and foaming resistance can be realized.

The components for the two image display devices include, for example, a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, a pen tablet, and the like, and components of an image display device such as an LCD, PDP, or EL. Can be mentioned. More specifically, for example, any one of the group consisting of a touch panel, an image display panel, a surface protection panel and a polarizing film, or a laminate composed of a combination of two or more kinds can be mentioned.

(Adhesive sheet roll)
As shown in FIG. 5, the present adhesive sheet may be in the form of being rolled into a roll. For example, the pressure-sensitive adhesive sheet X may be rolled into a roll and then photo-cured by irradiating only its end face with light, or the pressure-sensitive adhesive sheet having only its end face photo-cured may be rolled into a roll. good. In any case, if the end face of the adhesive sheet rolled into a roll is a photo-curing portion, the exposed roll end face will not become sticky even in a harsh environment such as high temperature and high humidity. Therefore, it can be suitably stored.

(Explanation of words, etc.)
Generally, a "sheet" is a product that is thin by definition in JIS, and its thickness is small for its length and width, and is flat. Generally, a "film" is thicker than its length and width. A thin, flat product with an extremely small size and an arbitrarily limited maximum thickness, which is usually supplied in the form of a roll (Japanese Industrial Standards JISK6900). However, since the boundary between the sheet and the film is not fixed and it is not necessary to distinguish between the two in the present invention, in the present invention, even if the term "film" is used, the term "sheet" is included and is referred to as "sheet". Even if it is, it shall include "film".
Further, when the term "panel" is used, such as an image display panel or a protective panel, it includes a plate, a sheet and a film, or a laminate thereof.

In the present specification, when "X to Y" (X and Y are arbitrary numbers) is described, it means "X or more and Y or less" and "preferably larger than X" or "preferably larger than X" unless otherwise specified. It also includes the meaning of "smaller than Y".
Further, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably larger than X" and is described as "Y or less" (Y is an arbitrary number). In the case of a field, the meaning of "preferably smaller than Y" is included unless otherwise specified.

Hereinafter, it will be described in more detail with reference to Examples. However, these do not limit the present invention in any way.

[Reference Example 1]
As the (meth) acrylic copolymer (A), 15 parts by mass (18 mol%) of a macromonomer composed of polymethyl methacrylate (Tg: 105 ° C.) and having a number average molecular weight of 2900 and butyl acrylate (Tg: −55 ° C.) Acrylic graft copolymer (A-1) obtained by random copolymerization of 81 parts by mass (75 mol%) and 4 parts by mass (7 mol%) of acrylic acid (Tg: 106 ° C.) (weight average molecular weight: 230,000). ) 1 kg, 90 g of glycerin dimethacrylate (manufactured by Nichiyu Co., Ltd., product name: GMR) (B-1) as a cross-linking agent (B), and 2,4,6-trimethylbenzophenone as a photopolymerization initiator (C). And 15 g of a mixture of 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) (C-1) were uniformly mixed to prepare an adhesive resin composition 1.
Peeled polyethylene terephthalate film Y (manufactured by Mitsubishi Resin Co., Ltd., Diafoil MRV-V06, thickness 100 μm, referred to as “release film Y”) and peeled polyethylene terephthalate film Z (manufactured by Mitsubishi Resin Co., Ltd., Dia The composition 1 is sandwiched between foil MRQ, thickness 75 μm, and referred to as “release film Z”), shaped into a sheet so as to have a thickness of 150 μm using a laminator, and an adhesive sheet X1 (thickness 150 μm). ) Was produced.
A black sheet (LSL-8 Inoac Co., Ltd., light transmittance 0%) was cut with double-sided tape on one side and cut into 50 mm × 100 mm on the surface of the release film Z laminated on one side of the adhesive sheet X1. A light-transmitting portion was formed by laminating, and an adhesive sheet laminate having a light-transmitting portion and a light-transmitting portion in the sheet surface was produced.
Next, from the black sheet side of the adhesive sheet laminate thus produced, ultraviolet rays are irradiated from the black sheet side so that the integrated light amount at a wavelength of 365 nm is 2000 mJ / cm ² , using a high-pressure mercury lamp, and the light of the adhesive sheet laminate is obtained. The permeable portion was cured to prepare an adhesive sheet 2-1 having a soft portion and a hard portion. (See Fig. 2)
Here, the soft portion means a portion of the adhesive sheet shielded by the black sheet, and the hard portion means a portion of the adhesive sheet not shielded by the black sheet.

[Example 2]
As the (meth) acrylic copolymer (A), 55 parts by mass (36 mol%) of 2-ethylhexyl acrylate (Tg: −70 ° C.) and 40 parts by mass (56 mol%) of vinyl acetate (Tg: 32 ° C.) were used. A cross-linking agent (B) with respect to 1 kg of an acrylic copolymer (A-2) (weight average molecular weight: 170,000) formed by random copolymerization with 5 parts by mass (8 mol%) of acrylic acid (Tg: 106 ° C.). ), 70 g of a mixture (B-2) (manufactured by Toa Synthetic Co., Ltd., product name: Aronix M313) of isocyanuric acid EO-modified diacrylate and isocyanuric acid EO-modified triacrylate, and EzaCure KTO46 as a photopolymerization initiator (C). (C-2) (manufactured by Polymer) 5 g was uniformly mixed to prepare an adhesive resin composition 2.
The composition 2 was sandwiched between the release films Y and Z and shaped into a sheet so as to have a thickness of 150 μm using a laminator to prepare an adhesive sheet X2 (thickness 150 μm).
A pressure-sensitive adhesive sheet laminate was produced in the same manner as in Reference Example 1 except that the pressure-sensitive adhesive sheet X2 was used, and further, a pressure-sensitive adhesive sheet 2 having a soft portion and a hard portion was produced in the same manner as in Reference Example 1.

[Reference Example 3]
As the (meth) acrylic copolymer (A), 10 parts by mass (17 mol%) of polymethylmethacrylate macromonomer (Tg: 105 ° C.) having a number average molecular weight of 1400 and 2-ethylhexyl acrylate (Tg: −70 ° C.) 90. 1 kg of acrylic graft copolymer (A-3) (weight average molecular weight: 230,000) formed by random copolymerization with parts by mass (83 mol%) and tricyclodecandidimethacrylate (new) as a cross-linking agent (B). A mixture of 50 g of Nakamura Chemical Co., Ltd., product name: DCP) (B-3) and 2,4,6-trimethylbenzophenone and 4-methylbenzophenone as a photopolymerization initiator (C) (manufactured by Lanberti Co., Ltd., product name: 15 g of Ezacure TZT) (C-1) was uniformly mixed to prepare an adhesive resin composition 3.
The composition 3 was sandwiched between the release films Y and Z and shaped into a sheet so as to have a thickness of 150 μm using a laminator to prepare an adhesive sheet X3 (thickness 150 μm).
A pressure-sensitive adhesive sheet laminate was produced in the same manner as in Reference Example 1 except that the pressure-sensitive adhesive sheet X3 was used, and further, a pressure-sensitive adhesive sheet 3 having a soft portion and a hard portion was produced in the same manner as in Reference Example 1.

[Reference example 4]
As the (meth) acrylic copolymer (A), 12 parts by mass (19 mol%) of polymethylmethacrylate macromonomer (Tg: 105 ° C.) having a number average molecular weight of 2400 and 2-ethylhexyl acrylate (Tg: -70 ° C.) 85. Acrylate-based graft copolymer (A-4) (weight average molecular weight: 80,000) 1 kg obtained by random copolymerization of parts by mass (74 mol%) and acrylic acid (Tg: 106 ° C.) by 3 parts by mass (7 mol%). As the cross-linking agent (B), 90 g of glycerin dimethacrylate (manufactured by Nichiyu Co., Ltd., product name: GMR) (B-1), and 2,4,6-trimethylbenzophenone and 4 as the photopolymerization initiator (C). -An adhesive resin composition 4 was prepared by uniformly mixing 15 g of a mixture of methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) (C-1).
The composition 4 was sandwiched between the release films Y and Z and shaped into a sheet so as to have a thickness of 150 μm using a laminator to prepare an adhesive sheet X4 (thickness 150 μm).
A pressure-sensitive adhesive sheet laminate was produced in the same manner as in Reference Example 1 except that the pressure-sensitive adhesive sheet X4 was used, and a pressure-sensitive adhesive sheet 4 having a soft portion and a hard portion was produced in the same manner as in Reference Example 1.

[Reference Example 5]
Photopolymerization started with 1 kg of the acrylic copolymer (A-1) (weight average molecular weight: 230,000) used in Reference Example 1 and 70 g of trimethylolpropane triacrylate (B-4) as the cross-linking agent (B). A mixture of 2,4,6-trimethylbenzophenone as an agent (C) and 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) (C-1) (8 g) is uniformly mixed to obtain the pressure-sensitive adhesive resin composition 5. Made.
A solution obtained by diluting the pressure-sensitive adhesive resin composition 5 with ethyl acetate so that the solid content concentration becomes 40% is peeled-treated polyethylene terephthalate film Y (manufactured by Mitsubishi Resin Co., Ltd., Diafoil MRV-V06, thickness 100 μm, “separation”. The peeled surface of the film Y) was coated and dried so that the thickness after drying was 25 μm, and then the peeled polyethylene terephthalate film Z (manufactured by Mitsubishi Resin Co., Ltd.) was applied to the coated adhesive surface. A pressure-sensitive adhesive sheet X5 (thickness 25 μm) was prepared by coating with a diafoil MRQ, a thickness of 75 μm, and referred to as “release film Z”).
A pressure-sensitive adhesive sheet laminate was produced in the same manner as in Reference Example 1 except that the pressure-sensitive adhesive sheet X5 was used, and further, a pressure-sensitive adhesive sheet 5 having a soft portion and a hard portion was produced in the same manner as in Reference Example 1.

[Comparative Example 1]
2-Ethylhexyl acrylate (Tg: -70 ° C) 75 parts by mass (57 mol%), vinyl acetate (Tg: 32 ° C) 20 parts by mass (33 mol%) and acrylic acid (Tg: 106 ° C) 5 parts by mass (10 mol%) To 1 kg of the (meth) acrylic copolymer (A-5) obtained by random copolymerization of the above, 200 g of trimethylol propantriacrylate (B-4) and 10 g of 4-methylbenzophenone (C-3) are mixed and added. Prepared a resin composition for an intermediate layer.
The resin composition for the intermediate layer is sandwiched between two stripped polyethylene terephthalate films (Panac, NP75Z01, thickness 75 μm / Toyobo, E7006, thickness 38 μm) so that the thickness is 80 μm. The sheet (α) for the intermediate layer was prepared by shaping it into a shape.

Subsequently, 20 g of 4-methylbenzophenone (C-3) as a photopolymerization initiator (C) was added and mixed with 1 kg of the acrylic copolymer (A-5) to prepare a resin composition for an adhesive layer. did.
The resin composition for the adhesive layer was sandwiched between two stripped polyethylene terephthalate films (Mitsubishi Plastics, Diafoil MRA, thickness 75 μm / Toyobo Co., Ltd., E7006, thickness 38 μm) to a thickness of 35 μm. A resin sheet (β) for an adhesive layer was prepared by shaping it into a sheet so as to be.
On the other hand, the resin composition for the adhesive layer was sandwiched between two stripped polyethylene terephthalate films (Mitsubishi Plastics, Diafoil MRF, thickness 75 μm / Toyobo Co., Ltd., E7006, thickness 38 μm), and the thickness was 35 μm. A resin sheet (β') for an adhesive layer was prepared by shaping it into a sheet so as to be.

The PET films on both sides of the intermediate layer sheet (α) are sequentially peeled off and removed, and the PET films on one side of the adhesive layer resin sheet (β) and (β') are peeled off, and the exposed adhesive surface is used for the intermediate layer. The sheets (α) were sequentially bonded to both surfaces to prepare a three-layer pressure-sensitive adhesive sheet composed of (β) / (α) / (β').
Through the PET film remaining on the surfaces of (β) and (β'), ultraviolet rays are irradiated with a high-pressure mercury lamp so ^{that the integrated light amount at a wavelength of 365 nm is 1000 mJ / cm 2, and (α), (β) and (β)} β') was crosslinked with ultraviolet rays to prepare a pressure-sensitive adhesive sheet X6 (thickness 150 μm).
Double-sided tape is attached to one side of a black sheet (LSL-8 Inoac, light transmittance 0%), cut into 50 mm x 100 mm, and then one of the adhesive sheets X6 is peeled off to form a polyethylene terephthalate film (manufactured by Mitsubishi Resin Co., Ltd.). , Diafoil MRF) was affixed to the surface to form light-transmitting, and a pressure-sensitive adhesive sheet laminate having a light-transmitting portion and a light-transmitting portion in the sheet surface was produced.
Next, from the black sheet side of the pressure-sensitive adhesive sheet laminated body thus produced by the pressure-sensitive adhesive sheet ^{, ultraviolet rays are irradiated from the black sheet side so that the integrated light amount at a wavelength of 365 nm is 2000 mJ / cm 2} , using a high-pressure mercury lamp, and the light of the laminated body is emitted. The pressure-sensitive adhesive material in contact with the transmissive portion was further irradiated with light to prepare a pressure-sensitive adhesive sheet 6.

[Comparative Example 2]
650 g of phenoxy resin (A-6) (manufactured by InChem, PKHH, weight average molecular weight of 52,000) and polyurethane acrylate (B-4) having a carbonate skeleton (manufactured by Negami Kogyo Co., Ltd.) as an alternative to the cross-linking agent (B). , UN5500, weight average molecular weight 67,000) 1 kg, and 43 g of 1-cyclohexylphenylketone (C-4) (BASF, Irgacure 184) as a photopolymerization initiator (C). 7 was produced.
The composition 7 is sandwiched between two stripped polyethylene terephthalate films (Mitsubishi Plastics, Diafoil MRV-V06, thickness 100 μm / Mitsubishi Plastics, Diafoil MRQ, thickness 75 μm), and a laminator is used. The adhesive sheet X7 (thickness 150 μm) was prepared by shaping it into a sheet so as to have a thickness of 150 μm.
Double-sided tape is attached to one side of a black sheet (LSL-8 Inoac Co., Ltd. light transmittance 0%), cut into 50 mm x 100 mm, and one of the adhesive sheets X7 is peeled off to form a polyethylene terephthalate film (manufactured by Mitsubishi Resin Co., Ltd.). , Diafoil MRQ) was affixed to the surface to form light-transmitting, and an adhesive sheet laminate having a light-transmitting portion and a light-transmitting portion in the sheet surface was prepared.
Next, from the black sheet side of the adhesive sheet laminate thus produced, ultraviolet rays are irradiated from the black sheet side so that the integrated light amount at a wavelength of 365 nm is 2000 mJ / cm ² , using a high-pressure mercury lamp, and the light of the adhesive sheet laminate is obtained. The permeable portion was cured to prepare an adhesive sheet 7.

[Comparative Example 3]
For 1 kg of a commercially available acrylic adhesive (A-7) (manufactured by Soken Kagaku Co., Ltd., trade name "SK Dyne 1882"), an isocyanate-based curing agent (manufactured by Soken Kagaku Co., Ltd., trade name "L-45") 1. An adhesive resin composition 6 was prepared by uniformly mixing 85 g and 0.5 g of an epoxy-based curing agent (manufactured by Soken Kagaku Co., Ltd., trade name “E-5XM”).
The composition 6 is applied to the release surface of a polyethylene terephthalate film (trade name "MRF75": manufactured by Mitsubishi Plastics Co., Ltd.) that has been peeled to a thickness of 50 μm so that the thickness after drying is 75 μm, and is heated. The solvent was dried to prepare a pressure-sensitive adhesive sheet having a thickness of 75 μm.
Further, the composition 6 was applied to a release surface of a stripped polyethylene terephthalate film (manufactured by Mitsubishi Plastics, Diafoil MRV-V06, thickness 100 μm) so that the thickness after drying was 75 μm. The solvent was dried by heating to prepare a pressure-sensitive adhesive sheet having a thickness of 75 μm.
The two pressure-sensitive adhesive sheets prepared were adhered to each pressure-sensitive adhesive surface and cured for one week to react with a curing agent to prepare a pressure-sensitive adhesive sheet 8 (thickness 150 μm).

[evaluation]
Various physical property values of the pressure-sensitive adhesive sheets 1 to 8 produced in Examples, Reference Examples and Comparative Examples were measured and evaluated as follows.

(Gel fraction)
The following measurements were taken for the parts of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples, Reference Examples and Comparative Examples that were in contact with the light-transmitting portion, that is, the hard portion and the portion that was in contact with the light-impermeable portion, that is, the soft portion. Was done.
For the adhesive sheet 8 of Comparative Example 3, the following measurements were performed at arbitrary points.

1) The pressure-sensitive adhesive composition is weighed (W1) and wrapped in a 200-mesh SUS mesh (W0) weighed in advance.
2) Immerse the SUS mesh in 100 mL of ethyl acetate for 24 hours.
3) Take out the SUS mesh and dry it at 75 ° C. for 4 and a half hours.
4) Obtain the weight (W2) after drying, and measure the gel fraction of the pressure-sensitive adhesive composition from the following formula.
Gel fraction (%) = 100 × (W2-W0) / W1

(Glass transition temperature (Tg))
Using a differential scanning calorimetry device (DSC-8500) manufactured by PerkinElmer, temperature rise measurement was performed at a temperature rise rate of 5 ° C./min based on JIS K-7121 (ISO3146), and an adhesive sheet was obtained from the obtained thermogram. The glass transition temperature (Tg) was determined for each of the portions of 1 to 7 in contact with the light transmitting portion, that is, the hard portion and the portion in contact with the light opaque portion, that is, the soft portion.
For the adhesive sheet 8 of Comparative Example 3, the same measurement was performed at any place.

(Asker hardness)
For the parts of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples, Reference Examples, and Comparative Examples that are in contact with the light-transmitting parts, that is, the soft parts, the release film of the sheet is peeled off, and the exposed adhesive surfaces are sequentially overlapped to form a plurality of sheets. The adhesive sheets were laminated so that the total thickness was within the range of 5 mm to 7 mm. As a result, the influence of the hardness of the stage on which the measurement sample is placed can be reduced, and the indentation hardness peculiar to the material can be compared and measured. Then, the tip terminal of the Asker C2L hardness tester was pressed vertically downward at a speed of 3 mm / min with a load of 1 kg against the exposed adhesive surface of the laminated adhesive sheet, and the C2 asker hardness (c) of the soft portion was measured.

In the same manner as above, the adhesive sheets are laminated so as to be within the range of 5 mm to 7 mm at the portions of the adhesive sheets 1 to 7 produced in Examples, Reference Examples and Comparative Examples in contact with the light transmitting portions, that is, the hard portions. The C2 asker hardness (d) of the hard portion was measured.
For the pressure-sensitive adhesive sheet 8 produced in Comparative Example 3, the same measurement was performed at any place.

(180 ° peeling force of soft part)
After cutting out the portion of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples, Reference Examples and Comparative Examples in contact with the light-transmitting portion, that is, the soft portion, one of the release films is peeled off, and a 50 μm PET film (Mitsubishi) is used as the backing film. A laminated product was prepared by laminating a die foil T100 manufactured by Resin Co., Ltd. (thickness 50 μm).
After cutting the laminated product to a length of 150 mm and a width of 10 mm, the adhesive sheet exposed by peeling off the remaining release film was rolled and pressure-bonded to the soda lime glass by reciprocating a roll of 2 kg once.
When this adhesive force measurement sample was peeled off at a peeling angle of 180 ° and a peeling speed of 60 mm / min in an environment of 23 ° C. and 40% RH, the peeling force (N / cm) on the glass was measured and light opaque. The 180 ° peeling force of the part in contact with the portion, that is, the soft portion was determined.

(180 ° peeling force of hard part)
For the adhesive sheets X1 to 7 in the state before light irradiation produced in Example 2, Reference Examples 1, 3 and 4, and Comparative Examples 1 and 2, one of the release films was peeled off, and a 50 μm PET film (Mitsubishi resin) was used as the backing film. A laminated product was prepared by laminating a die foil T100 (50 μm) manufactured by the same company.
After cutting the laminated product to a length of 150 mm and a width of 10 mm, the remaining release film was peeled off and the exposed adhesive surface was rolled and pressure-bonded to soda lime glass by reciprocating a 2 kg roll once. After autoclaving (80 ° C, gauge pressure 0.2 MPa, 20 minutes) is applied to the bonded product for finishing and bonding, the adhesive sheet is cured by irradiating it with ^{ultraviolet rays at 365 nm so that the integrated light intensity is 2000 mJ / cm 2.} After curing for 15 hours, it was used as a peeling force measurement sample.
The peeling force (N / cm) when the above peeling force measurement sample was peeled off at a peeling angle of 180 ° and a peeling speed of 60 mm / min in an environment of 23 ° C. and 40% RH was measured, and light transmission was performed. The 180 ° peeling force of the part in contact with the portion, that is, the hard portion was set.
With respect to the pressure-sensitive adhesive sheet 8 prepared in Comparative Example 3, after cutting out the pressure-sensitive adhesive sheet at an arbitrary portion, the measurement was carried out in the same manner as the procedure of the 180 ° C. peeling force of the soft portion.

(Retaining power of soft part)
After cutting the soft portion of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples, Reference Examples and Comparative Examples into 50 mm × 100 mm, the release film on one side is peeled off, and one side of the pressure-sensitive adhesive sheet is peeled off. However, it was attached with a hand roller so as to overlap with a polyethylene terephthalate film (thickness 38 μm) for lining, and this was cut into strips having a width of 25 mm and a length of 100 mm to obtain test pieces.
Next, the remaining release film was peeled off and attached to a vertically erected SUS plate (120 mm × 5 mm × 1.5 mm) with a hand roller so that the test pieces overlapped by a length of 20 mm. At this time, the bonding area between the transparent double-sided adhesive sheet and the SUS plate is 25 mm × 20 mm.
Then, the test piece was cured in an atmosphere of 40 ° C. and 70 ° C. for 15 minutes, and then a 4.9 N weight was attached vertically to the test piece and allowed to stand for 30 minutes. The length (mm) in which the sticking position was displaced downward was measured. For those with the sticking surface displaced and the weight dropped, the time required for the weight to fall was measured.
Since the adhesive sheet 7 of Comparative Example 2 does not have self-adhesiveness, the test piece laminated on the SUS plate was preheated at 80 ° C. for 5 minutes, and after being brought into close contact with the adherend, the holding force was measured. ..

(Holding power of hard part)
With respect to the adhesive sheets X1 to 7 in the state before light irradiation produced in Example 2, Reference Examples 1, 3 to 5 and Comparative Examples 1 and 2, the SUS and the test piece were used in the same manner as in the holding force measurement before photocuring. After making the laminate, backing while checking the integrated light amount with a photometer (UNIMETER UIT250 / sensor: UVD-C365) so that ultraviolet rays with a wavelength of 365 nm ^{reach 2000 mJ / cm 2 on the adhesive sheet.} A high-pressure mercury lamp was used to irradiate ultraviolet rays from the polyethylene terephthalate film side for use to prepare an adhesive sheet corresponding to a portion in contact with a light transmitting portion, that is, a hard portion.
Then, the test piece was cured in an atmosphere of 40 ° C. and 70 ° C. for 15 minutes, and then a 4.9 N weight was attached vertically to the test piece and allowed to stand for 30 minutes. The length (mm) in which the sticking position was displaced downward was measured.
When the test piece hardly moved and the deviation length was less than 0.1 mm, it was described as "<0.1 mm" in Table 2.
With respect to the pressure-sensitive adhesive sheet 8 produced in Comparative Example 3, after cutting out the pressure-sensitive adhesive sheet at an arbitrary portion, measurement was performed in the same manner as in the procedure for measuring the holding force of the soft portion.

(transparency)
One of the release films was peeled off from the part of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples and Comparative Examples in contact with the light-transmitting portion, that is, the hard portion, and the exposed adhesive surface was exposed to two soda lime glasses (82 mm × 53 mm ×). (0.5 mm thick) was rolled and bonded, and then autoclaved (80 ° C., gauge pressure 0.2 MPa, 20 minutes) was applied for finish bonding to prepare a laminate for optical evaluation.
For the adhesive sheet 8 prepared in Comparative Example 3, a sample was similarly prepared at any place.
For the laminated body, a haze value according to JIS K7136 and a total light transmittance (%) according to JIS K7361-1 were determined using a haze meter (NDH5000 manufactured by Nippon Denshoku Kogyo Co., Ltd.).

(Absorbing unevenness)
The adhesive sheets X1 to 4, 6 and 7 in the state before light irradiation produced in Example 2, Reference Examples 1, 3 and 4 and Comparative Examples 1 and 2 were cut into 50 mm × 80 mm, and one of the release films was obtained. The adhesive surface that was peeled off and exposed was placed on the printed surface of soda lime glass (82 mm x 53 mm x 0.5 mm thick) with a thickness of 80 μm printed on the peripheral edge of 3 mm, so that the four sides of the adhesive material were applied to the printing step. The film was press-pressed using a vacuum press (absolute pressure 5 kPa, temperature 80 ° C., press pressure 0.04 MPa). Next, the remaining release film was peeled off, and a Zeonoa film (manufactured by Nippon Zeon Corporation, 100 μm thickness) was press-bonded, and then autoclaved (80 ° C., gauge pressure 0.2 MPa, 20 minutes) was applied for finishing and bonding. From the printed soda lime glass side, the sheet X is irradiated with ultraviolet rays with a high-pressure mercury lamp so ^{that ultraviolet rays having a wavelength of 365 nm reach 2000 mJ / cm 2, and the unprinted openings, that is, the light transmitting parts are irradiated.} The sheets at the contact points were cured to prepare the evaluation laminates 1 to 6.
As for the adhesive sheet X5 prepared in Reference Example 5, a laminated body 7 for evaluation was similarly prepared using a printed soda lime glass having a printing thickness of 15 μm.
For the adhesive sheet 8 created in Comparative Example 3, a laminate of soda lime glass and Zeonoa film (manufactured by Nippon Zeon Co., Ltd., 100 μm thickness) printed in the same procedure as described above was prepared using the adhesive sheet 7. After that, it was subjected to autoclave treatment (80 ° C., gauge pressure 0.2 MPa, 20 minutes) for finishing and pasting to obtain a laminate 8 for evaluation.

Visually observing the manufactured laminates 1 to 8, those in which the adhesive material did not follow and bubbles remained in the vicinity of the printing step were marked with "x", and those in which the film was bent and distorted in the vicinity of the step and unevenness was visible. "Δ", and those bonded smoothly without bubbles were judged to be "○".

(Reliability against foaming)
The evaluation laminates 1 to 8 prepared by the unevenness absorption evaluation were put into a constant temperature and humidity chamber at 85 ° C. and 85% RH, and the appearance was observed after curing for 100 hours. Those in which bubbles were generated in the adhesive sheet were judged as "x", and those in which there was no change in appearance were judged as "○".

(Discussion)
Since the pressure-sensitive adhesive sheets produced in Examples 2 and Reference Examples 1 and 3 to 5 have a gel fraction of less than 1% in the soft portion, they exhibit high fluidity by heating. Therefore, by heating and melting at the time of bonding, not only is it excellent in followability to uneven surfaces, but even if one of the adherends is a material with low rigidity such as a film, it does not bend near the step and is smooth. I was able to obtain a good laminate. Furthermore, since the gel content of the hard part is 40% or more, it exhibits high cohesive force even under harsh environmental tests such as high temperature and high humidity, does not cause peeling, foaming, or deformation, and is highly reliable. It was possible to obtain a laminated body having the above.

Since the adhesive resin composition of the adhesive sheet of Comparative Example 1 is partially crosslinked by irradiation with ultraviolet rays, when the glass with a printing step and the film are laminated, the unevenness due to the printing step is transferred to the film side and the laminated body is smooth. Was not obtained. In addition, foaming was observed under the high temperature and high humidity test triggered by the distortion of the adhesive material near the step, and the storage stability was inferior.
Comparative Example 2 is a hot-melt type pressure-sensitive adhesive sheet that does not use a (meth) acrylic copolymer and uses a pressure-sensitive adhesive resin composition having a certain degree of rigidity in the room temperature range.
The sheet of Comparative Example 2 had a very low tackiness near room temperature as compared with the adhesive sheet of Example. When the glass with a printing step and the sheet are laminated, the fluidity at the time of heating is low, so that the unevenness due to the printing step is slightly transferred to the sheet side, and the smoothness of the laminated body is inferior to that of the adhesive sheet of the example. The result was. In addition, as can be seen from the high asker hardness in the light-impermeable areas, the sheet has high rigidity during bonding work and does not have self-adhesiveness, so it is adhered from the positioning stage when bonding. It is necessary to preheat the body, and there is also a problem that the work is complicated as compared with the adhesive sheet that can be attached at room temperature only by crimping.
In Comparative Example 3, since the cross-linking reaction of the pressure-sensitive adhesive resin composition of the pressure-sensitive adhesive sheet 7 has already been completed, there is no soft portion having a gel content of 1% or less in the pressure-sensitive adhesive sheet, and a printing step is formed on the film side. Not only was it impossible to obtain a smooth laminate due to the transfer of unevenness due to the above, but also the adhesive could not be partially filled in the vicinity of the corners where the printing steps intersect, resulting in the remaining bubbles.

From the results of the above examples and the test results conducted by the inventor so far, both the (meth) acrylic type having a soft portion having a gel fraction of less than 1% and a hard portion having a gel fraction of 40% or more. It can be considered that if a photocurable transparent double-sided pressure-sensitive adhesive sheet containing a polymer is used, the two image display device constituent members can be suitably bonded as in the embodiment.

Further, it can be considered that the gel fraction of the soft portion in the pressure-sensitive adhesive sheet surface is preferably less than 1%, and the gel fraction of the hard portion is preferably 40% or more.
Further, the glass transition temperature (actual measurement Tg) of the soft portion in the pressure-sensitive adhesive sheet surface is preferably −70 to −10 ° C., and the glass transition temperature (actual measurement Tg) of the hard portion is −60 to + 20 ° C., which is hard. It is preferable that the difference (Tg [H] -Tg [S]) between the glass transition temperature (Tg [H]) of the portion and the glass transition temperature (Tg [S]) of the soft portion is 3 ° C. or higher. can.

[Reference Example 6]
Regarding the adhesive sheet X1 produced in Reference Example 1, a long laminated sheet having a width of 150 mm and a length of 100 m is wound around a plastic winding core having a diameter of 6 inches with an initial winding tension of 70 N and a taper rate of 20%, and adhered. A sheet roll was produced.
A high-pressure mercury lamp is used to irradiate the end face of the produced sheet roll with light so that the integrated light amount at a wavelength of 365 nm ^{reaches 500 mJ / cm 2} , and the end face is photocured to have a hard portion on the end face. It was a roll.

[Comparative Example 4]
An adhesive sheet roll was produced in the same manner as in Reference Example 6 except that it was not irradiated with light.

The pressure-sensitive adhesive sheet roll of Comparative Example 4 having only the soft portion having no hard portion and the pressure-sensitive adhesive sheet roll of Reference Example 6 having a hard portion on the end face portion produced in this manner were constantly heated at 40 ° C. and 90% RH. After storing in a wet tank for 2 weeks, the end face of the adhesive sheet roll was visually observed.
The adhesive sheet roll of Reference Example 5 having a hard portion on the end face portion did not have glue squeezed out from the end face portion, and the sheet unwinding workability was good, whereas the adhesive sheet of Comparative Example 4 consisting of only a soft portion. The end face of the sheet roll became sticky due to the adhesive squeezing out, which hindered the unwinding work.

Claims (15)

A pressure-sensitive adhesive sheet containing a (meth) acrylic copolymer (A) and a photopolymerization initiator (C) and partially photo-cured, and a gel component is contained in any part of the surface of the pressure-sensitive adhesive sheet. It has a soft part with a ratio of less than 1% and a hard part with a gel content of 40% or more.
The (meth) acrylic copolymer (A) contains a monomer a having a glass transition temperature (Tg) of less than 0 ° C., a monomer b having a glass transition temperature (Tg) of 0 ° C. or higher and lower than 80 ° C., and a glass transition temperature. It is a (meth) acrylic acid ester copolymer or a vinyl copolymer obtained by copolymerizing with a monomer c having (Tg) of 80 ° C. or higher.
The molar ratio of the monomer a, the monomer b, and the monomer c in the (meth) acrylic acid ester copolymer or the vinyl copolymer constituting the (meth) acrylic copolymer (A) is a: b :. c = 10 to 40:90 to 35: 2 to 25,
The glass transition temperature (Tg [S]) of the soft portion measured by the differential scanning calorimeter (DSC) is −70 ° C. to −10 ° C., and the glass transition temperature (Tg [H]) of the hard portion is A pressure-sensitive adhesive sheet having a temperature of −60 ° C. to + 20 ° C., wherein the difference (Tg [H] −Tg [S]) between the glass transition temperature of the hard portion and the glass transition temperature of the soft portion is 3 ° C. or higher. A sheet formed of a resin composition containing a (meth) acrylic copolymer (A), a cross-linking agent (B), and a photopolymerization initiator (C) is partially photo-cured. The adhesive sheet according to claim 1. The (meth) acrylic copolymer (A) is a heavy weight average molecular weight of from 50,000 to 400,000 (meth) pressure-sensitive adhesive sheet according to claim 1 or 2, characterized in that an acrylic copolymer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein any of the monomers b or c is a (meth) acrylic acid ester monomer having a cyclic skeleton in the side chain. The cross-linking agent (B) has two or more cross-linking groups, and the cross-linking group is either an epoxy group, an isocyanate group, an oxetane group, a silanol group or a (meth) acryloyl group. The adhesive sheet according to any one of claims 2 to 4 , which is characteristic. The invention according to any one of claims 1 to 5 , wherein the adhesive sheet has a soft portion having a gel fraction of less than 1% and a hard portion having a gel fraction of 40% or more in the sheet surface. Adhesive sheet. A pressure-sensitive adhesive sheet laminate having a structure in which the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 and a release film are laminated. An image display device configuration laminate having a structure in which two image display device components are laminated via the adhesive sheet according to any one of claims 1 to 6. The eighth aspect of the present invention is characterized in that the image display device component is any one of the group consisting of a touch panel, an image display panel, a surface protection panel, and a polarizing film, or a laminate composed of a combination of two or more types. The above-mentioned laminated body for configuring an image display device. An image display device configured by using the laminate for forming an image display device according to claim 8 or 9. In an image display device having at least two image display device components facing each other, and at least one image display device component has a light-transmitting portion and a light-transmitting portion on a bonded surface.
An image display device having a configuration in which the space between the two components for an image display device is filled with the adhesive sheet according to any one of claims 1 to 6.
The image is characterized in that the gel fraction at a position in contact with the light transmitting portion of the pressure-sensitive adhesive sheet is 40% or more, and the gel fraction at a position in contact with the light opaque portion is less than 1%. Display device. The claim is characterized in that the constituent members for the two image display devices are any one of the group consisting of a touch panel, an image display panel, a surface protection panel, and a polarizing film, or a laminated body composed of a combination of two or more types. Item 11. The image display device according to item 11. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6 , wherein the end face portion on at least one side of the pressure-sensitive adhesive sheet has a hard portion having a gel fraction of 40% or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6 , wherein the end face portion on at least one side of the pressure-sensitive adhesive sheet wound in a roll shape has a hard portion having a gel fraction of 40% or more. A pressure-sensitive adhesive sheet laminate having a structure in which a release film is laminated on both the front and back sides of the pressure-sensitive adhesive sheet according to claim 13 or 14.

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