JP2021020998A - Adhesive sheet, adhesive sheet with release sheet and laminate - Google Patents

Abstract

To provide an adhesive sheet exhibiting excellent outgas resistance and yellowing resistance after post-curing.SOLUTION: There is provided an adhesive sheet having an adhesive layer obtained by forming an adhesive composition into a semi-cured state, wherein the adhesive composition comprises a crosslinkable (meth)acrylate copolymer, a crosslinking agent, a monofunctional monomer having one acryloyl group, a polyfunctional monomer having two acryloyl groups and a photopolymerization initiator, the crosslinkable (meth)acrylate copolymer has a unit derived from t-butyl methacrylate, the monofunctional monomer is a lauryl(meth)acrylate and the polyfunctional monomer is a diacrylate having a bisphenol skeleton.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive sheet, an adhesive sheet with a release sheet, and a laminate.

Conventionally, a display device such as a liquid crystal display (LCD) and an input device used in combination with a display device such as a touch panel have been widely used. In the manufacture of these display devices and input devices, transparent adhesive sheets are used for bonding optical members, and transparent adhesive sheets are also used for bonding display devices and input devices. ..

It is known that there are several polymerization methods for the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive sheet, as described below. Specifically, there are methods such as polymerization by heat, polymerization by active energy rays, polymerization by heat (or active energy rays), and then polymerization by active energy rays (or heat) in two stages.

The pressure-sensitive adhesive sheet formed by two-stage polymerization in which polymerization is carried out by heat (or active energy ray) and then polymerization by active energy ray (or heat) is an adhesive having both thermosetting property and active energy ray curable property. It is formed from a composition (hereinafter, may be referred to as "dual curable pressure-sensitive adhesive composition"). For example, the pressure-sensitive adhesive composition is thermoset before being bonded to the adherend, temporarily adhered to the adherend, and then further irradiated with active energy rays to completely cure the pressure-sensitive adhesive composition ( It is called post-curing or after-cure). As a result, the pressure-sensitive adhesive layer is firmly adhered to the adherend.

Patent Document 1 includes a base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and a lauryl acrylate (b1). The monomer (B), the cross-linking agent (C) that reacts with the base polymer (A) by heat, and the polymerization initiator (D) that initiates the polymerization reaction of the monomer (B) by irradiation with active energy rays. , A pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer obtained by semi-curing a pressure-sensitive adhesive composition containing the solvent (E) by heating is described.

Japanese Unexamined Patent Publication No. 2016-084391

When the adhesive sheet is attached to, for example, a resin plate that easily generates outgas, air bubbles may be generated at the interface between the adhesive sheet and the resin plate or in the adhesive sheet. Further, in recent years, an optical member to which an adhesive sheet is attached may be used in a harsh environment such as a high temperature or high humidity environment, and in such an environment, the adhesive sheet may turn yellow, which is a problem. It was.

Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of enhancing the outgas resistance and the yellowing resistance of the adhesive sheet after post-curing.

As a result of diligent studies to solve the above problems, the present inventors have made a crosslinkable (polymer) having a predetermined structure in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer in a semi-cured state. By blending an acrylic copolymer, a cross-linking agent, a lauryl (meth) acrylate, a diacrylate having a bisphenol skeleton, and a photopolymerization initiator, the pressure-sensitive adhesive layer after post-curing exhibits excellent outgas resistance and yellowing resistance. I found that it could be done.
Specifically, the present invention has the following configuration.

[1] An adhesive sheet having an adhesive layer in which the adhesive composition is in a semi-cured state.
The pressure-sensitive adhesive composition contains a crosslinkable (meth) acrylic copolymer, a crosslinker, a monofunctional monomer having one acryloyl group, a polyfunctional monomer having two acryloyl groups, and a photopolymerization initiator.
The crosslinkable (meth) acrylic copolymer has a unit derived from t-butyl methacrylate and has a unit.
The monofunctional monomer is lauryl (meth) acrylate,
An adhesive sheet in which the polyfunctional monomer is a diacrylate having a bisphenol skeleton.
[2] integrated quantity of light to the adhesive sheet and irradiating the cured adhesive sheet with an active energy ray such that the 3000 mJ / cm ^2, before and after processing when the post curing adhesive sheet was 500 hours at 105 ℃ L ^* a ^* b ^* The adhesive sheet according to [1], wherein the amount of change in the b value (Δb ^* ) in the color space is less than 0.5, and the color difference (ΔE ^* ab value) is less than 1.
[3] The content of the unit derived from t-butyl methacrylate in the crosslinkable (meth) acrylic copolymer is 15 to 40% by mass with respect to the total mass of the crosslinkable (meth) acrylic copolymer. The adhesive sheet according to [1] or [2].
[4] The content of lauryl (meth) acrylate is 5 to 30 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer, according to any one of [1] to [3]. Adhesive sheet.
[5] The content of the diacrylate having a bisphenol skeleton is 1 to 10 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer, according to any one of [1] to [4]. Adhesive sheet.
[6] The photopolymerization initiator according to any one of [1] to [5], wherein the photopolymerization initiator is a photopolymerization initiator having an absorbance of 0.2 or more at a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass. Adhesive sheet.
[7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the cross-linking agent is at least one selected from a 2-4-functional isocyanate-based cross-linking agent and a 2-4-functional epoxy-based cross-linking agent. ..
[8] For bonding the first member,
The adhesive sheet according to any one of [1] to [7], wherein the first member is at least one selected from a resin plate, a resin sheet, and a resin film.
[9] For bonding the second member,
The adhesive sheet according to any one of [1] to [8], wherein the second member is at least one selected from a glass plate, a resin plate, a resin sheet, and a resin film.
[10] The pressure-sensitive adhesive sheet according to [8] or [9], wherein the resin plate, the resin sheet and the resin film contain at least one selected from a polycarbonate resin and a (meth) acrylic resin.
[11] An adhesive sheet with a release sheet comprising a pair of release sheets having different peeling forces on both surfaces of the adhesive sheet according to any one of [1] to [10].
[12] An adhesive layer after curing after irradiating the adhesive layer of the adhesive sheet according to any one of [1] to [10] with active energy rays and post-curing, and an adhesive layer after post-curing. A laminate having a first member on one surface side and a second member on the other surface side of the post-cured pressure-sensitive adhesive layer.

According to the present invention, it is possible to obtain an adhesive sheet that exhibits excellent outgas resistance and yellowing resistance after post-curing.

FIG. 1 is a schematic view showing a cross section of a release sheet or an adhesive sheet having a base material.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, the numerical range represented by using "~" in this specification means the range including the numerical values before and after "~" as the lower limit value and the upper limit value.

In addition, in this specification, "(meth) acrylic" represents both acrylic and methacrylic, or either. Further, in the present specification, "monomer" and "monomer" are synonymous, and "polymer" and "polymer" are synonymous.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition is in a semi-cured state. Here, the pressure-sensitive adhesive composition includes a crosslinkable (meth) acrylic copolymer, a crosslinker, a monofunctional monomer having one acryloyl group, a polyfunctional monomer having two acryloyl groups, and a photopolymerization initiator. Contains. Here, the crosslinkable (meth) acrylic copolymer has a unit derived from t-butyl methacrylate, the monofunctional monomer is lauryl (meth) acrylate, and the polyfunctional monomer has a bisphenol skeleton. It is an acrylate.

With the above configuration, the pressure-sensitive adhesive sheet of the present invention can exhibit excellent outgas resistance and yellowing resistance after post-curing. In the pressure-sensitive adhesive sheet of the present invention, since the crosslinkable (meth) acrylic copolymer contains a unit derived from t-butyl methacrylate, the pressure-sensitive adhesive sheet after post-curing can be used in a harsh environment such as a high temperature or high humidity environment. Even if it is, yellowing is suppressed. Further, in the pressure-sensitive adhesive composition, outgas resistance can be more effectively enhanced by using lauryl (meth) acrylate as a monofunctional monomer and diacrylate having a bisphenol skeleton as a polyfunctional single amount in combination. .. As described above, the adhesive sheet of the present invention has both excellent outgas resistance and yellowing resistance.
On the other hand, since the pressure-sensitive adhesive sheet of the present invention has an adhesive layer in a semi-cured state before post-curing, it has excellent flexibility in the semi-cured state and is adhered to the adherend in the semi-cured state. Excellent adhesion to the adherend, for example, even when the adherend has a curved surface or a stepped portion, it follows the shape of the adherend and exhibits excellent adhesion. Then, since post-curing is performed in such a state, the pressure-sensitive adhesive layer can be firmly adhered to the adherend. As described above, the adhesive sheet of the present invention exhibits excellent outgas resistance and yellowing resistance while firmly adhering to the adherend during post-curing.

In the present specification, the outgas resistance of the pressure-sensitive adhesive sheet after post-curing is such that the integrated light amount becomes 3000 mJ / cm ² after the adherend is attached to both sides of the pressure-sensitive adhesive layer to prepare a laminated body. It can be evaluated by irradiating with ultraviolet rays, placing it in an environment of 105 ° C. and a relative humidity of 10% or less, and visually checking the laminated body after 500 hours. Specifically, it is preferable that no bubbles, floats or peeling are observed in the laminate.

In the present specification, the yellowing resistance of the adhesive sheet after post-curing is calculated by calculating the amount of change in the b value (Δb ^* ) in the L ^* a ^* b ^* color space and the color difference (ΔE ^* ab value). Can be evaluated. Specifically, when the pressure-sensitive adhesive sheet of the present invention is irradiated with active energy rays so that the integrated light intensity becomes 3000 mJ / cm ² to form a post-cured pressure-sensitive adhesive sheet, and then the post-cured pressure-sensitive adhesive sheet is treated at 105 ° C. for 500 hours. The amount of change in the b value (Δb ^* ) and the color difference (ΔE ^* ab value) in the L ^* a ^* b ^* color space before and after the processing of are calculated using the following formulas.
Equation 1)
ΔE ^* ab = [(L ^* 1-L ^* 0) ² + (a ^* 1-a ^* 0) ² + (b ^* 1-b ^* 0) ² ] ^1/2
Equation 2)
Δb ^* = b ^* 1-b ^* 0
Here, L ^* 0 is the L ^* value before the post-cured adhesive sheet is treated at 105 ° C. for 500 hours, and a ^* 0 is the a ^* value before the post-cured adhesive sheet is treated at 105 ° C. for 500 hours. , B ^* 0 are b ^* values before the post-cured adhesive sheet is treated at 105 ° C. for 500 hours. Further, L ^* 1 is the L ^* value after treating the post-cured adhesive sheet at 105 ° C. for 500 hours, and a ^* 1 is the a ^* value after treating the post-cured adhesive sheet at 105 ° C. for 500 hours. b ^* 1 is the b ^* value after the post-cured adhesive sheet is treated at 105 ° C. for 500 hours.
The value of Δb ^* is preferably less than 0.5, more preferably 0.4 or less. Further, the value of ΔE ^* ab is preferably less than 1, more preferably 0.9 or less, further preferably 0.8 or less, still more preferably 0.7 or less. It is particularly preferably 0.6 or less.

<Structure of adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet composed of only the pressure-sensitive adhesive layer. Further, the pressure-sensitive adhesive sheet may be a single-sided pressure-sensitive adhesive sheet having a base material (preferably a transparent base material) on one side, or a double-sided pressure-sensitive adhesive sheet. The double-sided adhesive sheet includes a single-layer adhesive sheet composed of an adhesive layer, a multi-layer adhesive sheet in which a plurality of adhesive layers are laminated, and a multi-layer adhesive in which another adhesive layer is laminated between the adhesive layers. A multi-layered pressure-sensitive adhesive sheet in which a support is laminated between a sheet, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer, and a multi-layered pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is laminated on one side of the support and another pressure-sensitive adhesive layer is laminated on the other side. Can be mentioned. When the double-sided adhesive sheet has a support, it is preferable to use a transparent support as the support. As the support, a general film used in the optical field can be used as in the case of the transparent substrate. Since such a double-sided pressure-sensitive adhesive sheet is also excellent in transparency of the pressure-sensitive adhesive sheet as a whole, it can be suitably used for bonding optical members to each other.

The pressure-sensitive adhesive sheet of the present invention is preferably a double-sided pressure-sensitive adhesive sheet. Further, the present invention may relate to an adhesive sheet with a release sheet having release sheets on both surfaces of the adhesive sheet. When the adhesive sheet of the present invention is provided with the release sheets on both surfaces, the adhesive sheet 10 with the release sheet may have the release sheets 12a and 12b on both surfaces of the adhesive layer 11 as shown in FIG. preferable.

The release sheet is a releaseable laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyolefin film such as a polyethylene film or polypropylene film as a low polarity base material. Can be mentioned.
Papers and polymer films are used as the base material for the release sheet in the releaseable laminated sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of the silicone-based release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone Co., Ltd., and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Can be mentioned. Further, the silicone-based release agent may contain a silicone resin which is an organic silicon compound having ₂ units of SiO and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ = CH (CH ₃ ) SiO _1/2 units. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.
A commercially available product may be used as the peelable laminated sheet. For example, a heavy separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd., and a light separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd., can be mentioned. it can.

The pressure-sensitive adhesive sheet with a release sheet preferably has a pair of release sheets having different peeling forces on both surfaces of the pressure-sensitive adhesive sheet. That is, it is preferable that the release sheet has different peelability between the release sheet 12a and the release sheet 12b in order to facilitate the release. When the peelability from one side and the peelability from the other side are different, it becomes easy to peel off only the release sheet having the higher peelability first. In that case, the peelability of the release sheet 12a and the release sheet 12b may be adjusted according to the bonding method and the bonding order.

Further, the present invention may relate to an adhesive sheet with a transparent film having a transparent film on at least one surface of the adhesive sheet. In this case, the transparent film is preferably at least one selected from a polyethylene terephthalate film, an acrylic film, a polycarbonate film, a triacetyl cellulose film and a cycloolefin polymer film. The adhesive sheet with a transparent film may be a sheet in which a transparent film / adhesive sheet / release sheet are laminated in this order.

<Adhesive layer>
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition is in a semi-cured state, and the pressure-sensitive adhesive layer has post-curing property. The pressure-sensitive adhesive sheet may be made of a pressure-sensitive adhesive layer.

In the present specification, when the gel fraction of the pressure-sensitive adhesive layer is increased by 10% by mass or more by irradiating or heating with active energy rays under the following conditions, the pressure-sensitive adhesive layer before irradiation or heating is in a semi-cured state. Suppose there is. In this case, when the pressure-sensitive adhesive layer is post-cured by irradiating it with active energy rays, the optical transparent PET separators are attached to both sides of the pressure-sensitive adhesive layer, and the active energy rays (high-pressure mercury lamp or high-pressure mercury lamp or) are attached from the optical transparent PET separator side. (Metal halide lamp) is irradiated so that the integrated light amount is 3000 mJ / cm ² . When the pressure-sensitive adhesive layer is post-cured by heating, heat treatment is performed in an oven at 100 ° C. for 1 hour with separator films (release sheets) bonded to both surfaces of the pressure-sensitive adhesive layer.
Above all, the gel fraction of the pressure-sensitive adhesive layer in the semi-cured state is preferably 10% by mass or more and less than 70% by mass, and more preferably 20% by mass or more and less than 65% by mass. The gel fraction of the pressure-sensitive adhesive layer after post-curing is preferably 65 to 100% by mass, more preferably 70 to 100% by mass.

The gel fraction of the pressure-sensitive adhesive layer is a value measured by the following method. First, about 0.1 g of an adhesive sheet (adhesive layer) is collected in a sample bottle, 30 ml of ethyl acetate is added, and the mixture is shaken for 24 hours. Then, the contents of this sample bottle are filtered through a 150 mesh stainless steel wire mesh, and the residue on the wire mesh is dried at 100 ° C. for 1 hour to measure the dry mass (g). The gel fraction is calculated from the obtained dry mass by the following formula 1.
Gel fraction (mass%) = (dry mass / collected mass of adhesive sheet) x 100 ... Equation 1

In the present specification, the "semi-cured state" is preferably a state after thermosetting. Then, it is preferable to "post-cure" by irradiating with active energy rays after that. That is, the "semi-cured state" is preferably a state after thermosetting and is a soft pressure-sensitive adhesive layer before irradiation with active energy rays. The "post-curing" is preferably a step of completely curing the pressure-sensitive adhesive layer with heat or active energy rays, and more preferably a step of completely curing the pressure-sensitive adhesive layer with active energy rays. That is, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably in a semi-cured state by thermosetting the pressure-sensitive adhesive composition, and preferably has active energy ray-curability.

The thickness of the pressure-sensitive adhesive layer can be appropriately set according to the intended use, and is not particularly limited, but is preferably 5 to 1000 μm, more preferably 8 to 500 μm, and particularly preferably 10 to 300 μm. By setting the thickness of the pressure-sensitive adhesive layer within the above range, it is possible to prevent the pressure-sensitive adhesive from sticking out and stickiness, so that workability can be improved. Further, by setting the thickness of the pressure-sensitive adhesive layer within the above range, the production of a double-sided pressure-sensitive adhesive sheet becomes easy.

The adhesive force against glass with a peeling speed of 300 mm / min measured by a method according to JIS Z 0237 of the pressure-sensitive adhesive layer is preferably 1 to 25 N / 25 mm in a semi-cured state, and is preferably 3 to 20 N / 25 mm. Is more preferable, and after post-curing, it is preferably 10 to 50 N / 25 mm, and more preferably 15 to 45 N / 25 mm. By setting the adhesive force of the pressure-sensitive adhesive layer against the glass within the above range, it is possible to suppress unintentional peeling of the pressure-sensitive adhesive layer, and on the other hand, it is possible to easily re-peel the pressure-sensitive adhesive layer when it is attached by mistake.

<Adhesive composition>
The pressure-sensitive adhesive layer described above is a semi-cured state of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition used in the present invention is a dual-curable pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition contains a crosslinkable (meth) acrylic copolymer, a crosslinker, a monofunctional monomer having one acryloyl group, a polyfunctional monomer having two acryloyl groups, and a photopolymerization initiator.

(Crosslinkable (meth) acrylic copolymer)
The crosslinkable (meth) acrylic copolymer has a unit derived from t-butyl methacrylate. Further, the crosslinkable (meth) acrylic copolymer may further have a non-crosslinkable (meth) acrylic acid ester unit (a1) in addition to the unit derived from t-butyl methacrylate, and has a crosslinkable functionality. It may further contain an acrylic monomer unit (a2) having a group. In addition, in this specification and claims, a "unit" is a repeating unit (monomer unit) constituting a polymer.

The crosslinkable (meth) acrylic copolymer has a unit derived from t-butyl methacrylate, and the content of the unit derived from t-butyl methacrylate in the crosslinkable (meth) acrylic copolymer is crosslinkable (meth). The amount is preferably 15% by mass or more, more preferably 18% by mass or more, further preferably 20% by mass or more, and more preferably 25% by mass or more, based on the total mass of the meta) acrylic copolymer. Is particularly preferred. The content of the unit derived from t-butyl methacrylate is preferably 40% by mass or less with respect to the total mass of the crosslinkable (meth) acrylic copolymer. By setting the content of the unit derived from t-butyl methacrylate within the above range, the pressure-sensitive adhesive sheet of the present invention can exhibit more excellent yellowing resistance after post-curing and can improve processability. ..

The crosslinkable (meth) acrylic copolymer has, in addition to the unit derived from t-butyl methacrylate, a non-crosslinkable (meth) acrylic ester unit (a1) as long as it does not interfere with yellowing resistance. May be good. The non-crosslinkable (meth) acrylic acid ester unit (a1) is a repeating unit derived from the (meth) acrylic acid alkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, n-butyl (meth) acrylic acid, and (meth). Isobutyl acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, (meth) N-nonyl acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate, (meth) Examples thereof include stearyl acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. One of these may be used alone, or two or more thereof may be used in combination.
Among the above (meth) acrylic acid alkyl esters, at least one selected from methyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate is selected because of its high adhesiveness. preferable.

The crosslinkable (meth) acrylic copolymer may further contain an acrylic monomer unit (a2) having a crosslinkable functional group in addition to the unit derived from t-butyl methacrylate. In this case, the acrylic monomer unit (a2) having a crosslinkable functional group is a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, and a glycidyl group-containing monomer unit. Is preferable.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.
The hydroxy group-containing monomer unit is a repeating unit derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 3-chloro-2-hydroxypropyl (meth) acrylate. , 4-Hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, polyalkylene glycol mono (meth) acrylate and the like.
Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth) acrylamide and allylamine.
Examples of the glycidyl group-containing monomer unit include repeating units derived from a glycidyl group-containing monomer such as glycidyl (meth) acrylate.

When the crosslinkable (meth) acrylic copolymer further contains an acrylic monomer unit (a2) having a crosslinkable functional group, the acrylic monomer unit (a2) having a crosslinkable functional group is a hydroxy group-containing simple substance. It is preferably a monomer unit. When the crosslinkable (meth) acrylic copolymer has a hydroxy group-containing monomer unit, yellowing of the pressure-sensitive adhesive sheet can be suppressed more effectively. Furthermore, since the crosslinkable (meth) acrylic copolymer has a hydroxy group-containing monomer unit, it is possible to exhibit better adhesiveness to an adherend such as a resin plate.

The content of the acrylic monomer unit (a2) having a crosslinkable functional group in the crosslinkable (meth) acrylic copolymer is preferably 0.5 to 50% by mass, preferably 1.0 to 40% by mass. Is more preferable. When the content of the acrylic monomer unit (a2) having a crosslinkable functional group is at least the lower limit of the above range, it has sufficient crosslinkability necessary for maintaining the semi-cured state, and is in the above range. If it is below the upper limit of, it is easy to maintain the required adhesiveness.

When the acrylic monomer unit having a crosslinkable functional group in the crosslinkable (meth) acrylic copolymer is a unit derived from a hydroxy group-containing (meth) acrylate, a unit derived from the hydroxy group-containing (meth) acrylate. The content is preferably 5% by mass or more, and more preferably 10% by mass or more, based on the total mass of the crosslinkable (meth) acrylic copolymer. The content of the unit derived from the hydroxy group-containing (meth) acrylate is preferably 50% by mass or less, preferably 40% by mass or less, based on the total mass of the crosslinkable (meth) acrylic copolymer. Is more preferable. By setting the content of the unit derived from the hydroxy group-containing (meth) acrylate within the above range, the adhesion to the adherend can be further enhanced.

In the crosslinkable (meth) acrylic copolymer, the content of the carboxy group-containing monomer unit may be 1% by mass or less with respect to the total mass of the crosslinkable (meth) acrylic copolymer. Preferably, it may be 0% by mass. Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.

<Nitrogen-containing monomer>
The crosslinkable (meth) acrylic copolymer may further contain units derived from nitrogen-containing monomers. The nitrogen-containing monomer is a monomer containing a nitrogen element in one molecule. Examples of the nitrogen-containing monomer include dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, N-vinylcaprolactam, and N-vinyl-2-. Examples thereof include pyrrolidone, dimethylaminoethyl (meth) acrylate, and N-vinylformamide. Among them, the nitrogen-containing monomer is preferably at least one selected from an acrylamide derivative, an amino group-containing monomer and a nitrogen-containing heterocyclic ring-containing monomer, and more preferably an acrylamide derivative. The acrylamide derivative is more preferably at least one selected from dimethylacrylamide, diethylacrylamide and acryloylmorpholine, and particularly preferably dimethylacrylamide. Since the crosslinkable (meth) acrylic copolymer contains a unit derived from the nitrogen-containing monomer as described above, the semi-cured pressure-sensitive adhesive layer is easily adhered to the substrate, while being easily adhered to the substrate. The pressure-sensitive adhesive layer after post-curing becomes high in hardness, and outgas resistance can be further enhanced.

When the crosslinkable (meth) acrylic copolymer contains units derived from the nitrogen-containing monomer, the content of the units derived from the nitrogen-containing monomer is the total mass of the crosslinkable (meth) acrylic copolymer. On the other hand, it is preferably 1% by mass or more, and more preferably 3% by mass or more. The content of the unit derived from the nitrogen-containing monomer is preferably 20% by mass or less with respect to the total mass of the crosslinkable (meth) acrylic copolymer.

The crosslinkable (meth) acrylic copolymer may have other monomeric units, if desired. The other monomer may be a monomer copolymerizable with the above-mentioned acrylic monomer, and examples thereof include (meth) acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylpyrrolidone, and vinylpyridine. The content of the other monomer unit in the crosslinkable (meth) acrylic copolymer is preferably 20% by mass or less, and more preferably 15% by mass or less.

<Weight average molecular weight of crosslinkable (meth) acrylic copolymer>
The weight average molecular weight of the crosslinkable (meth) acrylic copolymer is preferably 100,000 to 2 million, more preferably 200,000 to 1.5 million. When the weight average molecular weight is within the above range, it is easy to maintain the semi-cured state of the pressure-sensitive adhesive sheet, and it is easy to obtain the hardness after post-curing, and the processability is excellent. The weight average molecular weight of the crosslinkable (meth) acrylic copolymer is a value before cross-linking with a cross-linking agent. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and determined based on polystyrene. As the crosslinkable (meth) acrylic copolymer, a commercially available one may be used, or one synthesized by a known method may be used.

(Crosslinking agent)
The pressure-sensitive adhesive composition contains a cross-linking agent. The cross-linking agent can be appropriately selected in consideration of the reactivity of the cross-linking (meth) acrylic copolymer with the cross-linking functional group. For example, it can be selected from known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds and butylated melamine compounds. Among these, it is preferable to use an isocyanate compound or an epoxy compound because the hydroxy group-containing (meth) acrylate can be easily crosslinked. That is, the cross-linking agent is preferably at least one selected from a 2- to 4-functional isocyanate-based cross-linking agent and a 2- to 4-functional epoxy-based cross-linking agent.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. Examples of commercially available products include tolylene diisocyanate compounds (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L), xylylene diisocyanate compounds (manufactured by Mitsui Chemicals, Inc., Takenate D-110N) and the like. Examples of the epoxy compound include TETRAD-C (manufactured by Mitsubishi Gas Chemical Company), TETRAD-X manufactured by Mitsubishi Gas Chemical Company, and the like.

The content of the cross-linking agent in the pressure-sensitive adhesive composition is appropriately selected according to the desired tackiness and the like, but is 0.01 to 5 parts by mass with respect to 100 parts by mass of the cross-linking (meth) acrylic copolymer. Is preferable, and 0.1 to 3 parts by mass is more preferable. By setting the content of the cross-linking agent within the above range, the workability can be further improved. As the cross-linking agent, one type may be used alone or two or more types may be used in combination, and when two or more types are used in combination, the total mass is preferably within the above range.

(Monofunctional monomer)
The pressure-sensitive adhesive composition contains a monofunctional monomer having one acryloyl group. Here, the monofunctional monomer is lauryl (meth) acrylate, and lauryl acrylate is particularly preferable. Since the pressure-sensitive adhesive composition contains lauryl (meth) acrylate, the semi-cured pressure-sensitive adhesive sheet is excellent because it has high wettability to adherends such as resin plates and glass, but does not have high adhesive strength. Demonstrates reworkability. Further, after the adhesive sheet is completely cured, the outgas resistance of the adhesive sheet can be more effectively enhanced.

The content of the lauryl (meth) acrylate is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and 10 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. The above is more preferable, and 15 parts by mass or more is particularly preferable. The content of lauryl (meth) acrylate is preferably 30 parts by mass or less with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. By setting the content of the lauryl (meth) acrylate within the above range, the outgas resistance of the pressure-sensitive adhesive sheet after post-curing can be more effectively enhanced.

(Polyfunctional monomer)
The pressure-sensitive adhesive composition contains a monomer (polyfunctional monomer) having a bisphenol skeleton in the molecule and having two (meth) acryloyl groups. That is, the pressure-sensitive adhesive composition contains a diacrylate having a bisphenol skeleton as a polyfunctional monomer. In the present invention, by using a polyfunctional monomer having a bisphenol skeleton in one molecule, it is possible to increase the hardness of the pressure-sensitive adhesive layer after post-curing and at the same time impart stress relaxation property.

Examples of such a polyfunctional monomer include diacrylate of bisphenol A diglycidyl ether, diacrylate of propoxylated bisphenol A, and diacrylate of bisphenol F diglycidyl ether.

Commercially available products can be used as the polyfunctional monomer. Examples of commercially available products include bifunctional monomer M211B (bisphenol A ethylene oxide-modified diacrylate) manufactured by Toa Synthetic Co., Ltd., bifunctional monomer M208 (bisphenol F ethylene oxide-modified diacrylate) manufactured by Shin-Nakamura Chemical Co., Ltd. , Bifunctional monomer A-BPP-3 (propoxylated bisphenol A diacrylate) and the like.

The content of the diacrylate having a bisphenol skeleton is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and 3 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. The above is more preferable, and 5 parts by mass or more is particularly preferable. The content of the diacrylate having a bisphenol skeleton is preferably 10 parts by mass or less with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. By setting the content of the diacrylate having a bisphenol skeleton within the above range, the hardness of the pressure-sensitive adhesive layer after post-curing can be increased more effectively, and the processability of the pressure-sensitive adhesive sheet can be improved.

(Photopolymerization initiator)
The pressure-sensitive adhesive composition contains a photopolymerization initiator. The photopolymerization initiator is preferably one that initiates the polymerization of a polyfunctional monomer or a monofunctional monomer by irradiation with active energy rays. Here, the "active energy ray" means an electromagnetic wave or a charged particle beam having an energy quantum, and examples thereof include ultraviolet rays, electron beams, visible rays, X-rays, and ion beams. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

The photopolymerization initiator is preferably a photopolymerization initiator having an absorbance of 0.2 or more at a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass. By using such a photopolymerization initiator, the polymerization reaction between the polyfunctional monomer and the monofunctional monomer can easily proceed by irradiation with active energy rays.

The photopolymerization initiator is not particularly limited, but is, for example, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenylketone, 2-hydroxy-2-methyl-1-henylpropanol, 1- [4-( 2-Hydroxyethoxyl) -phenyl] -2-hydroxy-methylpropanone, 2-hydroxy-1-(4- (4- (2-hydroxy-2-methylpropionyl) benzyl) phenyl) -2-methyl-1- Alkylphenone-based photopolymerization initiators such as propanone, acylphosphine oxide-based polymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl) phenylphosphine oxide, Examples thereof include intramolecular hydrogen abstraction type photopolymerization initiators such as methyl benzoylate and 4-methylbenzophenone, as well as oil-soluble polymerization initiators such as oxime ester-based photopolymerization initiators and cationic photopolymerization initiators.
Among these, the acylphosphine oxide-based photopolymerization initiator has an absorbance of 0.2 or more at a wavelength of 380 nm in an acetonitrile solution having a concentration of 0.1% by mass, so that polymerization starts even through a film or resin plate having ultraviolet absorbing performance. Therefore, it is preferable.
Commercially available products of such an acylphosphine oxide-based photopolymerization initiator include IRGACURE 819 (bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide BASF) and IRGACURE TPO (2,4,6-trimethyl). Benzoyludiphenylphosphine oxide (manufactured by BASF) and the like can be mentioned.

The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is appropriately selected according to the content of the monomer, the irradiation amount of the active energy ray at the time of post-curing, and the like. Meta) With respect to 100 parts by mass of the acrylic copolymer, 0.01 to 5 parts by mass is preferable, and 0.1 to 3 parts by mass is more preferable. By setting the content of the photopolymerization initiator within the above range, the outgas resistance and yellowing resistance of the post-cured pressure-sensitive adhesive sheet can be more effectively enhanced. Further, the processability of the pressure-sensitive adhesive sheet can be improved by setting the content of the photopolymerization initiator within the above range.

(solvent)
The pressure-sensitive adhesive composition may contain a solvent. In this case, the solvent is used to improve the coating suitability of the pressure-sensitive adhesive composition. Examples of the solvent include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene and dichloropropane; methanol, ethanol, Alcohols such as propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate , Ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate, etc .; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Examples thereof include polyols such as glycol monomethyl ether acetate and derivatives thereof.

The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, more preferably 30 to 400 parts by mass, based on 100 parts by mass of the crosslinkable (meth) acrylic copolymer.
The content of the solvent is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the pressure-sensitive adhesive composition. One type of solvent may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the total mass is preferably within the above range.

(Other ingredients)
The pressure-sensitive adhesive composition may contain components other than the above as long as the effects of the present invention are not impaired. Examples of other components include components known as additives for adhesives. For example, a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, a light stabilizer such as a hindered amine compound, and the like can be selected as necessary. In addition, dyes and pigments may be added for the purpose of coloring.

As the plasticizer, for example, a non-functional group acrylic polymer may be used. The non-functional group acrylic polymer does not have a functional group such as a polymer consisting of only an acrylic monomer unit having no functional group other than an acrylate group or an acrylic monomer unit having no functional group other than an acrylate group. Examples thereof include polymers composed of non-acrylic monomer units. Since the non-functional group acrylic polymer is not crosslinked, the step followability can be improved without affecting the adhesiveness.
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. One type of these antioxidants may be used alone, or two or more types may be used in combination.
As the metal corrosion inhibitor, a benzodiazole-based resin can be mentioned as a preferable example because of the compatibility and high effect of the pressure-sensitive adhesive.
Examples of the tackifier include rosin-based resin, terpene-based resin, terpene phenol-based resin, Kumaron inden-based resin, styrene-based resin, xylene-based resin, phenol-based resin, and petroleum resin.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto group-substituted alkoxy oligomer).
Examples of the ultraviolet absorber include benzotriazole-based compounds, benzophenone-based compounds, and triazine-based compounds.

<Manufacturing method of adhesive sheet>
The method for producing an adhesive sheet of the present invention includes a step of applying the above-mentioned pressure-sensitive adhesive composition on a release sheet to form a coating film, and a step of heating the coating film to make a cured product in a semi-cured state. Is preferable. By heating the coating film, the reaction between the crosslinkable (meth) acrylic copolymer and the crosslinker proceeds to form a cured product (adhesive layer) in a semi-cured state. That is, during heating, the polymerization reaction of the polyfunctional monomer or the monofunctional monomer by the photopolymerization initiator does not proceed in the coating film, or even if it progresses, it is slight, so that the pressure-sensitive adhesive layer contains The polyfunctional monomer and monofunctional monomer contained in the pressure-sensitive adhesive composition, and at least a part of the photopolymerization initiator are contained in an unreacted state. As described above, the pressure-sensitive adhesive sheet of the present invention preferably has post-curability and active energy ray-curability.

In order to bring the pressure-sensitive adhesive composition into a semi-cured state, it is preferable to perform an aging treatment in which the pressure-sensitive adhesive sheet is allowed to stand at a constant temperature for a certain period of time after the solvent is removed after coating. The aging treatment can be performed, for example, by allowing it to stand at 23 ° C. for 7 days.

The semi-cured pressure-sensitive adhesive layer can be post-cured by irradiating an adherend such as a base material with active energy rays. That is, the pressure-sensitive adhesive sheet of the present invention is a two-step curing type pressure-sensitive adhesive sheet, has a pressure-sensitive adhesive layer semi-cured only by heat before bonding, and the pressure-sensitive adhesive layer is post-cured by active energy rays after bonding. Will be done.

The coating of the pressure-sensitive adhesive composition can be carried out using a known coating device. Examples of the coating device include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater and the like.

A known heating device such as a heating furnace or an infrared lamp can be used for heating the coating film formed by applying the pressure-sensitive adhesive composition.

<How to use the adhesive sheet>
In the method of using the pressure-sensitive adhesive sheet of the present invention, it is preferable that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend. In the method of using the pressure-sensitive adhesive sheet, it is preferable that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is adhered to an adherend when it is in a semi-cured state and irradiated with active energy rays to post-cure the pressure-sensitive adhesive layer.

<Use of adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention can suppress the generation of air bubbles even when it is attached to an adherend such as a base material, post-cured, and then exposed to a high humidity and heat environment. The pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet used for bonding to a base material, and is a pressure-sensitive adhesive sheet used for bonding to at least one selected from a resin plate, a resin sheet, and a resin film. Is more preferable.

When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet is bonded to the first member and the second member. In this case, the first member is at least one selected from a resin plate, a resin sheet and a resin film, and the second member is at least one selected from a glass plate, a resin plate, a resin sheet and a resin film. It is preferable to have.

When a resin plate, a resin sheet or a resin film is used as the adherend, these members are preferably members containing at least one selected from a polycarbonate resin and a (meth) acrylic resin. For example, the resin plate, the resin sheet or the resin film may be a resin plate made of polycarbonate, a resin sheet or a resin film, or may be a resin plate made of (meth) acrylic resin, a resin sheet or a resin film. Further, the resin plate, the resin sheet or the resin film may be a member containing both a polycarbonate resin and a (meth) acrylic resin, and may be, for example, a laminate of a polycarbonate resin layer and a (meth) acrylic resin. ..

Examples of the polycarbonate base material include PC-1151 manufactured by Teijin Chemicals Ltd. Further, as the multilayer base material containing the polycarbonate base material, for example, MR-58U or IMR05 manufactured by Mitsubishi Gas Chemical Company, Inc. can be used. Here, the composition of MR-58U is HC (hard coat) / PMMA (polymethyl methacrylate) / PC (polycarbonate) / HC (hard coat). The overall thickness of MR-58U is preferably 0.3 mm to 1.2 mm, and the thickness of one hard coat layer is preferably 0.0005 mm to 0.02 mm. The composition of IMR05 is HC (hard coat) / PC (polycarbonate).

Further, the pressure-sensitive adhesive sheet of the present invention suppresses the generation of bubbles and peeling even when exposed to a high humidity and heat environment after being bonded to an optical member such as a polarizing plate and post-cured. be able to. Here, the polarizing plate includes a polarizing element and a polarizer protective film, and the pressure-sensitive adhesive sheet of the present invention is preferably bonded to the polarizer protective film. The polarizer protective film includes a cycloolefin resin film, a cellulose acetate resin film such as triacetyl cellulose and diacetyl cellulose, a polyester resin film such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, a polycarbonate resin film, and acrylic. Examples thereof include a based resin film and a polypropylene resin film. In particular, when the polarizer protective film is a cellulose acetate-based resin film, the effect of suppressing the generation of bubbles is exhibited by using the pressure-sensitive adhesive sheet of the present invention.
In the present invention, since the generation of air bubbles in the adherend of the adhesive sheet can be suppressed, deterioration of visibility can be prevented when the adhesive sheet is incorporated in a display device or the like.

<Laminated body>
The present invention also relates to a laminate having the above-mentioned adhesive sheet and adherend. In the laminated body, the pressure-sensitive adhesive layer of the above-mentioned pressure-sensitive adhesive sheet is irradiated with active energy rays and post-cured, and then the first member is provided on one surface side of the post-cured pressure-sensitive adhesive layer and the post-cured pressure-sensitive adhesive layer. It is preferable that the second member is provided on the other surface side of the pressure-sensitive adhesive layer after post-curing.

Here, the first member is at least one selected from a resin plate, a resin sheet and a resin film, and the second member is at least one selected from a glass plate, a resin plate, a resin sheet and a resin film. It is preferable to have. It is preferable that all the members are optical members. Examples of the optical member include each component in an optical product such as a touch panel and an image display device, a cover lens on the outermost layer, and the like.

When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet can be used for bonding transparent optical films inside a touch panel, bonding a transparent optical film and glass, and bonding a transparent optical film and a liquid crystal panel for a touch panel. It is used for bonding with, bonding of cover glass and transparent optical film, bonding of resin cover lens and touch panel, etc., and one of the members is selected from polycarbonate resin and (meth) acrylic resin. It may be a member containing at least one kind. A hard coat layer may be provided on the transparent optical film or the polycarbonate base material.

<Manufacturing method of laminated body>
The method for producing a laminated body includes a step of attaching the pressure-sensitive adhesive layer of the above-mentioned pressure-sensitive adhesive sheet to an adherend in a semi-cured state and then irradiating an active energy ray to post-cure the pressure-sensitive adhesive layer. Before the irradiation with the active energy rays, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is in a semi-cured state, so that the initial adhesion to the substrate is good. In this way, after the pressure-sensitive adhesive sheet is attached to the adherend, the pressure-sensitive adhesive layer is post-cured with active energy rays, so that the cohesive force of the pressure-sensitive adhesive layer is increased and the adhesiveness to the adherend is improved. In addition, the post-cured pressure-sensitive adhesive layer can prevent the base material from being deformed or distorted.

Examples of the active energy ray include ultraviolet rays, electron beams, visible rays, X-rays, ion rays and the like, which can be appropriately selected depending on the polymerization initiator contained in the pressure-sensitive adhesive layer. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.
As the light source of ultraviolet rays, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp and the like can be used.
As the electron beam, for example, an electron beam emitted from each type of electron beam accelerator such as Cockloft Wald type, Bandecliff type, Resonant transformer type, Insulated core transformer type, Linear type, Dynamitron type, High frequency type is used. it can.
Radiation output of the UV, integrated light quantity is preferably to be a 100~10000mJ / cm ^2, and more preferably made to be 500~5000mJ / cm ^2.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below.

(Synthesis of crosslinkable (meth) acrylic copolymer A-1)
2-Ethylhexyl acrylate (2EHA) is blended in an amount of 40% by mass, t-butyl methacrylate (TBMA) in an amount of 35% by mass, and 2-hydroxyethyl acrylate (2HEA) in a proportion of 25% by mass. As a radical polymerization initiator 2, 2'-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain a crosslinkable (meth) acrylic copolymer (A-1). The weight average molecular weight of the crosslinkable (meth) acrylic copolymer (A-1) was 430,000.

(Synthesis of crosslinkable (meth) acrylic copolymer A-2)
2-Ethylhexyl acrylate (2EHA) is blended in an amount of 50% by mass, t-butyl methacrylate (TBMA) is blended in an amount of 25% by mass, and 2-hydroxyethyl acrylate (2HEA) is blended in an amount of 25% by mass as a radical polymerization initiator. 2'-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain a crosslinkable (meth) acrylic copolymer (A-2). The weight average molecular weight of the crosslinkable (meth) acrylic copolymer (A-2) was 460,000.

(Synthesis of crosslinkable (meth) acrylic copolymer A-3)
2-Ethylhexyl acrylate (2EHA) is blended in an amount of 52% by mass, t-butyl methacrylate (TBMA) in an amount of 18% by mass, and 2-hydroxyethyl acrylate (2HEA) in an amount of 30% by mass. As a radical polymerization initiator 2, 2'-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain a crosslinkable (meth) acrylic copolymer (A-3). The weight average molecular weight of the crosslinkable (meth) acrylic copolymer (A-3) was 470,000.

(Synthesis of crosslinkable (meth) acrylic copolymer B-1)
Butyl acrylate (BA) is blended in an amount of 75% by mass and 2-hydroxyethyl acrylate (2HEA) is blended in an amount of 25% by mass, and 2,2'-azobis (2,4-dimethylvaleronitrile) is added as a radical polymerization initiator. Dissolved in solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain a crosslinkable (meth) acrylic copolymer (B-1). The weight average molecular weight of the crosslinkable (meth) acrylic copolymer (B-1) was 510,000.

(Example 1)
0.15 parts by mass of a cross-linking agent (Coronate L-55 manufactured by Toso Co., Ltd.) and lauryl acrylate (Osaka) as a monofunctional monomer with respect to 100 parts by mass of the solid content of the crosslinkable (meth) acrylic copolymer A-1. 27 parts by mass of LA) manufactured by Organic Chemical Industry Co., Ltd., 8 parts by mass of diacrylate (bisphenol FEO modified diacrylate) having a bisphenol skeleton as a polyfunctional monomer (M208 manufactured by Toa Synthetic Co., Ltd.), photopolymerization initiator (BASF) 0.5 part by mass of (IrgacureTPO) manufactured by the same company was added, and the mixture was diluted and stirred with ethyl acetate so as to have a solid content concentration of 40% by mass to prepare an adhesive composition.

<Making an adhesive sheet>
A 38 μm-thick polyethylene terephthalate film (first release sheet) (manufactured by Oji F-Tex Co., Ltd., 38RL-07) having a release agent layer treated with a silicone-based release agent on the pressure-sensitive adhesive composition prepared as described above. The surface of (2)) is uniformly coated with an applicator so that the coating thickness after drying is 200 μm, dried in an air circulation type constant temperature oven at 100 ° C. for 3 minutes, and then applied to the surface of the first release sheet. A pressure-sensitive adhesive layer was formed. Next, a second release sheet (manufactured by Oji F-Tex Co., Ltd., 38RL-07 (L)) having a thickness of 38 μm was attached to the surface of the pressure-sensitive adhesive layer. In this way, an adhesive sheet with a release sheet having a structure of a first release sheet / an adhesive layer / a second release sheet in which the adhesive layer is sandwiched between a pair of release sheets having a difference in release force was obtained. .. The adhesive sheet was cured for 7 days under the conditions of 23 ° C. and 50% relative humidity.

(Example 2)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that the polyfunctional monomer was changed to M211B manufactured by Toagosei Co., Ltd.

(Example 3)
0.15 parts by mass of a cross-linking agent (Coronate L-55 manufactured by Toso Co., Ltd.) and lauryl acrylate (Osaka) as a monofunctional monomer with respect to 100 parts by mass of the solid content of the crosslinkable (meth) acrylic copolymer A-2. 20 parts by mass of LA) manufactured by Organic Chemical Industry Co., Ltd., 5 parts by mass of diacrylate (bisphenol FEO modified diacrylate) having a bisphenol skeleton as a polyfunctional monomer (M208 manufactured by Toa Synthetic Co., Ltd.), photopolymerization initiator (BASF) 0.5 part by mass of (IrgacureTPO) manufactured by the same company was added, and the mixture was diluted and stirred with ethyl acetate so as to have a solid content concentration of 40% by mass to prepare an adhesive composition.
An adhesive sheet with a release sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared as described above was used.

(Example 4)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 3 except that the polyfunctional monomer was changed to M211B manufactured by Toagosei Co., Ltd.

(Example 5)
0.15 parts by mass of a cross-linking agent (Coronate L-55 manufactured by Toso Co., Ltd.) and lauryl acrylate (Osaka) as a monofunctional monomer with respect to 100 parts by mass of the solid content of the crosslinkable (meth) acrylic copolymer A-3. 10 parts by mass of LA) manufactured by Organic Chemical Industry Co., Ltd., 2 parts by mass of diacrylate (bisphenol FEO modified diacrylate) having a bisphenol skeleton as a polyfunctional monomer (M208 manufactured by Toa Synthetic Co., Ltd.), photopolymerization initiator (BASF) 0.5 part by mass of (IrgacureTPO) manufactured by the same company was added, and the mixture was diluted and stirred with ethyl acetate so as to have a solid content concentration of 40% by mass to prepare an adhesive composition.
An adhesive sheet with a release sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared as described above was used.

(Example 6)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 5 except that the polyfunctional monomer was changed to M211B manufactured by Toagosei Co., Ltd.

(Comparative Example 1)
0.15 parts by mass of a cross-linking agent (Coronate L-55 manufactured by Toso Co., Ltd.) and lauryl acrylate (Osaka) as a monofunctional monomer with respect to 100 parts by mass of the solid content of the crosslinkable (meth) acrylic copolymer B-1. 10 parts by mass of LA) manufactured by Organic Chemical Industry Co., Ltd., 2 parts by mass of diacrylate (bisphenol FEO modified diacrylate) having a bisphenol skeleton as a polyfunctional monomer (M208 manufactured by Toa Synthetic Co., Ltd.), photopolymerization initiator (BASF) 0.5 part by mass of (IrgacureTPO) manufactured by the same company was added, and the mixture was diluted and stirred with ethyl acetate so as to have a solid content concentration of 40% by mass to prepare an adhesive composition.
An adhesive sheet with a release sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared as described above was used.

(Comparative Example 2)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Comparative Example 1 except that the monofunctional monomer was changed to ISTA manufactured by Osaka Organic Chemical Industry Co., Ltd.

(Comparative Example 3)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Comparative Example 1 except that the polyfunctional monomer was changed to M360 manufactured by Toagosei Co., Ltd.

(Comparative Example 4)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that the monofunctional monomer was changed to ISTA manufactured by Osaka Organic Chemical Industry Co., Ltd.

[Measurement and evaluation]
<Outgas resistance>
The outgas resistance was evaluated as follows using the adhesive sheet with a release sheet prepared in Examples and Comparative Examples.
In the adhesive sheet with a release sheet, the second release sheet, which is a light separator film, is peeled off to expose the adhesive layer, and the adhesive layer is attached to a glass plate having a size of 100 mm × 200 mm as a first member. I matched it. Next, the first release sheet, which is a heavy separator film, is peeled off, and the exposed adhesive layer is a polycarbonate resin plate (Teijin Co., Ltd.) having a size of 120 mm × 220 mm and a thickness of 1 mm, which is one size larger than the above glass as a second member. Panlight sheet PC-1151) made of the same product was attached so that the central portions of the sheets overlap each other. As a result, a laminate sample composed of a polycarbonate resin plate / adhesive layer / glass plate was obtained. After treating the laminated body sample in an autoclave at 40 ° C. and 0.5 MPa for 30 minutes, ultraviolet rays are irradiated from the polycarbonate resin plate side so that the integrated light intensity is 3000 mJ / cm ^2, and the bonded area is 100 mm × 200 mm. A test sample of the size of was obtained. The test sample was placed in an environment of 105 ° C. and a relative humidity of 2% for 500 hours, and then the test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the following three criteria.
◯: No bubbles, floats or peeling were observed.
Δ: No floating or peeling was observed, but less than 10 bubbles having a diameter of less than 1 mm were observed.
X: 10 or more bubbles having a diameter of 1 mm or more or bubbles having a diameter of less than 1 mm were observed, or floating or peeling was observed.

<Yellow evaluation>
The second release sheet (light release separator) of the adhesive sheet is peeled off and attached to a transparent glass plate (manufactured by Matsunami Glass Industry Co., Ltd., S9112) having a thickness of 1.2 mm, and then the first release sheet (heavy release separator) is attached. Was peeled off, and another transparent glass plate similar to the above was bonded to prevent air from entering to prepare a laminated sample. Then, the laminated sample was treated in an autoclave at 40 ° C. and 0.5 MPa for 30 minutes, and then irradiated with a high-pressure mercury lamp so that the integrated light intensity was 3000 mJ / cm ² . After that, after standing for 1 hour in an environment of 23 ° C. and 50% relative humidity, the L ^* a ^* b ^* color space L ^* value, a ^* value, and b ^* value were measured and the initial value L ^* 0, It was set to a ^* 0 and b ^* 0. Subsequently, this test sample was treated in an environment of 105 ° C. and 2% relative humidity for 500 hours, and then the L ^* a ^* b ^* color space L ^* a ^* b ^* color space L ^* value, a ^* value, and b ^* value were measured again with a color difference meter. These values were taken as L ^* 1, a ^* 1, and b ^* 1, and the ΔE ^* ab and Δb ^* values were obtained by the following formulas and evaluated according to the following evaluation criteria.
Equation 1)
ΔE ^* ab = [(L ^* 1-L ^* 0) ² + (a ^* 1-a ^* 0) ² + (b ^* 1-b ^* 0) ² ] ^1/2
Equation 2)
Δb ^* = b ^* 1-b ^* 0
(Evaluation criteria)
Yellowing (1)
◯: ΔE ^* ab is less than 1, ×: ΔE ^* ab is 1 or more Yellowing (2)
◯: Δb ^* is less than 0.5 ×: Δb ^* is 0.5 or more

From the above results, the adhesive sheet of the example was excellent in outgas resistance, and yellowing was suppressed even when it was left under high temperature conditions for a long time.

Claims (12)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition is in a semi-cured state.
The pressure-sensitive adhesive composition contains a crosslinkable (meth) acrylic copolymer, a crosslinker, a monofunctional monomer having one acryloyl group, a polyfunctional monomer having two acryloyl groups, and a photopolymerization initiator. ,
The crosslinkable (meth) acrylic copolymer has a unit derived from t-butyl methacrylate and has a unit.
The monofunctional monomer is lauryl (meth) acrylate and
An adhesive sheet in which the polyfunctional monomer is a diacrylate having a bisphenol skeleton. The pressure-sensitive adhesive sheet is irradiated with active energy rays so that the integrated light intensity is 3000 mJ / cm ^2, and the post-cured pressure-sensitive adhesive sheet is prepared. L ^* a ^* b before and after the treatment when the post-cured pressure-sensitive adhesive sheet is treated at 105 ° C. for 500 hours. ^* The adhesive sheet according to claim 1, wherein the amount of change in the b value (Δb ^* ) in the color space is less than 0.5, and the color difference (ΔE ^* ab value) is less than 1. The content of the unit derived from t-butyl methacrylate in the crosslinkable (meth) acrylic copolymer is 15 to 40% by mass based on the total mass of the crosslinkable (meth) acrylic copolymer. Item 2. The adhesive sheet according to Item 1 or 2. The adhesive according to any one of claims 1 to 3, wherein the content of the lauryl (meth) acrylate is 5 to 30 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. Sheet. The item according to any one of claims 1 to 4, wherein the content of the diacrylate having a bisphenol skeleton is 1 to 10 parts by mass with respect to 100 parts by mass of the crosslinkable (meth) acrylic copolymer. Adhesive sheet. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the photopolymerization initiator is a photopolymerization initiator having an absorbance at a wavelength of 380 nm of 0.2 or more in an acetonitrile solution having a concentration of 0.1% by mass. .. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the cross-linking agent is at least one selected from a 2-4-functional isocyanate-based cross-linking agent and a 2-4-functional epoxy-based cross-linking agent. For bonding the first member,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the first member is at least one selected from a resin plate, a resin sheet, and a resin film. For bonding the second member,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the second member is at least one selected from a glass plate, a resin plate, a resin sheet, and a resin film. The pressure-sensitive adhesive sheet according to claim 8 or 9, wherein the resin plate, the resin sheet, and the resin film contain at least one selected from a polycarbonate resin and a (meth) acrylic resin. An adhesive sheet with a release sheet, comprising a pair of release sheets having different release forces on both surfaces of the adhesive sheet according to any one of claims 1 to 10. One of a post-curing pressure-sensitive adhesive layer and a post-curing pressure-sensitive adhesive layer after irradiating the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 10 with active energy rays and post-curing A laminate having a first member on the surface side of the adhesive layer and a second member on the other surface side of the post-cured pressure-sensitive adhesive layer.

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