JP6036674B2 - Double-sided pressure-sensitive adhesive sheet, double-sided pressure-sensitive adhesive sheet with release sheet, method for producing the same, and transparent laminate - Google Patents

Description

The present invention relates to an adhesive, particularly a double-sided pressure-sensitive adhesive sheet that is used by being attached to a liquid crystal cell of a liquid crystal display device, a double-sided pressure-sensitive adhesive sheet with a release sheet and a method for producing the same, and a transparent laminate constituting an optical component such as a polarizing plate About the body.

In a liquid crystal cell of a liquid crystal display (LCD), a polarizing plate is bonded and used. On one side of this polarizing plate, an adhesive layer for adhering to other optical components such as a liquid crystal cell (hereinafter referred to as “liquid crystal cell”) is formed. A mold sheet is attached. Moreover, in order to protect the surface on the surface on the opposite side to the said adhesive layer of a polarizing plate, the protective sheet (protective film) comprised by the protective sheet base material and an adhesive layer is affixed. In this case, the polarizing plate is used after the release sheet is peeled off and attached to the liquid crystal cell with the exposed adhesive layer, and then the protective sheet is peeled off.

The polarizing plate substrate used in the liquid crystal cell has a three-layer structure in which a PVA polarizer is sandwiched between two TAC (triacetylcellulose) protective films, or a TAC protective film and COP ( (Cycloolefin polymer) It has a three-layer structure with a PVA polarizer between it and a protective film. Due to its material properties, it has poor dimensional stability, especially in high temperature or high temperature and high humidity environments due to shrinkage. Is big. Therefore, when such a polarizing plate is attached to a liquid crystal cell with an adhesive, defects such as lifting and peeling of the adhesive layer are likely to occur. Such a problem can be reduced by reducing the holding power of the pressure-sensitive adhesive layer, but problems such as foaming of the pressure-sensitive adhesive layer due to insufficient cohesive force of the pressure-sensitive adhesive layer arise.

JP 2001-294828 A JP 09-033723

Conventionally, various adhesives have been proposed to prevent these defects. By using a two-component cross-linking type acrylic adhesive having high adhesive strength and high shearing force, problems such as floating and peeling caused by contraction of the polarizing plate substrate were improved. However, in recent years, the optical parts of liquid crystal cells have also been made thinner due to the thinning of touch panels such as smartphones. Specifically, a polarizing plate, a transparent conductive film such as tin-doped indium oxide (ITO), a glass that supports a conductive member such as a metal circuit, and an adhesive layer that bonds and fixes them are thinner than before. For this reason, the liquid crystal cell comprised from a polarizing plate / adhesive layer / glass warps to the polarizing plate side by the shrinkage | contraction of a polarizing plate, etc. have arisen. In addition, the shrinkage stress of the polarizing plate base material cannot be absorbed or relaxed by the adhesive, and cannot follow the deformation of the base film, resulting in white spots in the TN (TFT) liquid crystal cell and color unevenness in the STN. There is a problem that is easy to do.

A two-layer double-sided pressure-sensitive adhesive sheet composed of a first acrylic pressure-sensitive adhesive layer as described in Patent Document 1 and a second acrylic pressure-sensitive adhesive layer with a large amount of added plasticizer has been proposed. However, when the pressure-sensitive adhesive layer is thinned according to the thinning of the liquid crystal cell, the problem that the liquid crystal cell warps to the polarizing plate side due to contraction of the polarizing plate cannot be improved. A two-layer double-sided pressure-sensitive adhesive sheet composed of acrylic pressure-sensitive adhesive layers having different shear elastic moduli as described in Patent Document 2 has also been proposed, but in the same way, the problem of warpage could not be improved with a thin pressure-sensitive adhesive layer. .

As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the main component of the first pressure-sensitive adhesive layer is one of an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and an epoxy-based pressure-sensitive adhesive. It has been found that high stress relaxation and adhesion can be achieved by using a urethane-based pressure-sensitive adhesive as the main component of the pressure-sensitive adhesive layer.
The present invention has been provided based on such knowledge, and includes the following configurations.

[1] A double-sided pressure-sensitive adhesive sheet for bonding a first transparent base material and a second transparent base material, the double-sided pressure-sensitive adhesive sheet has a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, The main component of the first pressure-sensitive adhesive layer is any one of an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and an epoxy-based pressure-sensitive adhesive. The main component of the second pressure-sensitive adhesive layer is a urethane-based pressure-sensitive adhesive. The gel fraction of the pressure-sensitive adhesive layer is larger than the gel fraction of the second pressure-sensitive adhesive layer, the interlayer strength between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is 5 N / 25 mm or more, The first pressure-sensitive adhesive layer is in contact with the transparent base material, the second pressure-sensitive adhesive layer is in contact with the second transparent base material, and the first transparent base material is a polycarbonate single-layer sheet, a polymethyl methacrylate single-layer sheet, Polycarbonate / polymethylmethacrylate laminate sheet, triacetylcellulose sheet, cycloolefin Characterized in that it is either fin polymer sheet, double-sided pressure-sensitive adhesive sheet.
[2] The double-sided pressure-sensitive adhesive sheet according to [1], wherein the thickness of the first pressure-sensitive adhesive layer is 1 to 20 μm, and the thickness of the second pressure-sensitive adhesive layer is 1 to 30 μm.
[3] The double-sided adhesive according to [1] or [2], wherein the gel fraction of the first adhesive layer is 60% or more and the gel fraction of the second adhesive layer is less than 60%. Sheet.
[4] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the first pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive.
[5] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein an antistatic agent is contained in at least one of the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer.
[6] A double-sided pressure-sensitive adhesive sheet with a release sheet, wherein the release sheet is laminated on at least one side of the double-sided pressure-sensitive adhesive sheet according to any one of [1] to [5].
[7] A step of applying a first pressure-sensitive adhesive layer-forming coating solution on a release sheet, and heating the first pressure-sensitive adhesive layer-forming coating solution to form the first pressure-sensitive adhesive layer. Forming the second pressure-sensitive adhesive layer-forming coating liquid on the other release sheet, heating the second pressure-sensitive adhesive layer-forming coating liquid, and applying the second pressure-sensitive adhesive layer-forming coating liquid. And a step of forming a pressure-sensitive adhesive layer, and a step of overlapping and pressure-bonding the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer so that they are in contact with each other. A method for producing an adhesive sheet.
[8] A step of simultaneously applying a first pressure-sensitive adhesive layer-forming coating liquid and a second pressure-sensitive adhesive layer-forming coating liquid on a release sheet, and for applying a first pressure-sensitive adhesive layer that has been applied With the release sheet according to [6], including a step of heating the coating liquid and the second adhesive layer forming coating liquid to form the first adhesive layer and the second adhesive layer. A method for producing a double-sided PSA sheet.
[9] A transparent laminate in which the first transparent substrate and the second transparent substrate are bonded together by the double-sided pressure-sensitive adhesive sheet according to any one of [1] to [5].

According to the present invention, it is possible to provide a method for producing a double-sided pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet with a release sheet, and a double-sided pressure-sensitive adhesive sheet with a release sheet that are excellent in stress relaxation and adhesion with an optical film and hardly cause delamination. Since the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in stress relaxation properties, it can easily follow the deformation of the optical film, and can provide a transparent laminate in which the double-sided pressure-sensitive adhesive sheet is in close contact while maintaining the display performance of the liquid crystal display device.

It is sectional drawing which shows one Embodiment of the double-sided adhesive sheet of this invention. It is sectional drawing which shows one Embodiment of the double-sided adhesive sheet with a peeling sheet of this invention. It is sectional drawing which shows one Embodiment of the transparent laminated body of this invention.

<Double-sided adhesive sheet>
One embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention will be described.
In FIG. 1, the double-sided adhesive sheet 10 of this embodiment is shown. The double-sided pressure-sensitive adhesive sheet 10 of this embodiment includes a first pressure-sensitive adhesive layer 11 and a second pressure-sensitive adhesive layer 12 provided in contact with one surface 11 a of the first pressure-sensitive adhesive layer 11.

(First adhesive layer)
The 1st adhesive layer 11 has as a main component any one adhesive of an acrylic adhesive, a polyester adhesive, or an epoxy adhesive.
An acrylic pressure-sensitive adhesive is obtained by crosslinking an acrylic polymer with a cross-linking agent, a polyester-based pressure-sensitive adhesive is obtained by cross-linking a polyester polymer with a cross-linking agent, and an epoxy pressure-sensitive adhesive comprises an epoxy resin formed by a cross-linking agent. Cross-linked. Further, the “main component” means that 50% by mass or more is contained with respect to the entire pressure-sensitive adhesive layer. In terms of higher adhesion to an optical film such as a polarizing plate substrate, the ratio of the main component is preferably 70% by mass or more, and more preferably 90% by mass or more.
Further, from the viewpoint of excellent transparency, light resistance, and heat resistance, the first pressure-sensitive adhesive layer 11 preferably contains an acrylic pressure-sensitive adhesive as a main component.

[Acrylic polymer]
The acrylic polymer is a polymer having a non-crosslinkable acrylic monomer unit and a crosslinkable monomer unit. Here, the “monomer unit” is a repeating unit constituting the polymer. An “acrylic polymer” is a compound having a (meth) acryloyl group. “(Meth) acryloyl group” means an acryloyl group or a methacryloyl group. The non-crosslinkable acrylic monomer is an acrylic monomer having no crosslinkable group, and the crosslinkable monomer is a monomer having a crosslinkable group. The crosslinkable monomer may be an acrylic monomer or a nonacrylic monomer as long as it can be polymerized with the noncrosslinkable acrylic polymer, and is preferably an acrylic monomer. Examples of the crosslinkable group include a carboxyl group, a hydroxyl group, an amino group, and an epoxy group glycidyl group.

Examples of the non-crosslinkable acrylic monomer unit include a (meth) acrylic acid ester unit in which a hydrogen atom of a carboxyl group of (meth) acrylic acid is substituted with a hydrocarbon group. 1-18 are preferable and, as for carbon number of this hydrocarbon group, 1-8 are more preferable. The hydrocarbon group may have a substituent. The substituent is not particularly limited as long as it does not contain a crosslinkable group, and examples thereof include alkoxy groups such as methoxy group and ethoxy group. Specific examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, Isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n- (meth) acrylate Octyl, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, N-dodecyl (meth) acrylate, stearyl, methoxyethyl (meth) acrylate, (meth) acrylic acid Kishiechiru, cyclohexyl (meth) acrylate include benzyl (meth) acrylate. These may be used individually by 1 type and may use 2 or more types together.
In the present invention, “(meth) acrylic acid” means containing both “acrylic acid” and “methacrylic acid”.
Among these, n-butyl acrylate, 2-ethylhexyl acrylate, and methyl acrylate are preferable from the viewpoint of adhesiveness.

As the crosslinkable monomer unit, a carboxyl group-containing copolymerizable monomer unit, a hydroxyl group-containing copolymerizable monomer unit, an amino group-containing copolymerizable monomer unit, a glycidyl group-containing copolymerizable monomer Examples include body units. Examples of the carboxyl group-containing copolymerizable monomer include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, grataconic acid, and anhydrides thereof. Such as things.
Examples of the hydroxyl group-containing copolymerizable monomer include (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. (Meth) acrylic acid lactones such as hydroxyalkyl, (meth) acrylic acid mono (diethylene glycol) (meth) acrylic acid [(mono, di or poly) alkylene glycol], (meth) acrylic acid monocaprolaclone It is done.
Examples of the amino group-containing copolymerizable monomer include (meth) acrylamide and allylamide.
Examples of the glycidyl group-containing copolymerizable monomer include glycidyl (meth) acrylate.
Among these, a hydroxyl group-containing copolymerizable monomer unit is preferable from the viewpoint of adhesiveness, crosslinkability, polymerizability and durability, and reworkability that allows re-peeling and reuse of glass, More preferred are hydroxyalkyl methacrylates, particularly preferred are 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

The content of the crosslinkable monomer unit in the acrylic polymer is preferably 0.01 to 20% by mass, and more preferably 0.5 to 10% by mass. If the content of the crosslinkable monomer unit is not less than the above lower limit value, it can be sufficiently crosslinked, and if it is not more than the above upper limit value, sufficient adhesive strength can be secured.
In addition, when a carboxyl group-containing copolymerizable monomer unit is contained as a crosslinkable monomer unit, the acidity becomes strong, so when a corrosive film such as a tin-doped indium oxide film or a metal film is in contact with these, May corrode the film. In the case of containing a carboxyl group-containing copolymerizable monomer unit as a crosslinkable monomer unit from the viewpoint of corrosion resistance to a metal film such as a tin-doped indium oxide film applied to the liquid crystal cell surface, the inclusion The amount is preferably less than 0.5% by mass, and more preferably 0% by mass.

The acrylic polymer may have other monomer units other than the non-crosslinkable acrylic monomer unit and the crosslinkable monomer unit. Examples of other monomers include (meth) acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinyl pyrrolidone, vinyl pyridine and the like.
The content of other monomer units in the acrylic polymer is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. If the content of other monomer units is not less than the lower limit, the physical properties can be easily adjusted, and if it is not more than the upper limit, yellowing due to deterioration with time can be prevented.

[Crosslinking agent used for acrylic polymer]
Examples of the crosslinking agent used for the acrylic polymer include isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, butylated melamine compounds, and the like. Among these crosslinking agents, an isocyanate compound and an epoxy compound are preferable because the acrylic polymer can be easily crosslinked. In particular, when the acrylic polymer contains only a hydroxyl group-containing copolymerizable monomer unit as a crosslinkable monomer unit, it is preferable to use an isocyanate compound because of the reactivity of the hydroxyl group.
Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diester. Glycidyl ether, tetraglycidyl xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexanone, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Can be mentioned. It is preferable that the content of the crosslinking agent is appropriately selected according to the desired pressure-sensitive adhesive properties.

[Polyester polymer]
The polyester polymer is a polymer obtained by polycondensation of a polyvalent carboxylic acid component containing an aromatic dicarboxylic acid and a polyol component containing a diol having a hydrocarbon group in the side chain. A polymer obtained by further polycondensing a trivalent or higher polyvalent carboxylic acid and / or a trivalent or higher polyhydric alcohol is preferable.

Examples of the aromatic dicarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p- Phenylene diglycolic acid, o-phenylene diglycolic acid, diphenylacetic acid, diphenyl-p, p-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid And aromatic dicarboxylic acids such as anthracene dicarboxylic acid, phthalic anhydride, 1,8-naphthalenedicarboxylic acid anhydride, 2,3-naphthalenedicarboxylic acid anhydride, and the like.

Moreover, the ester compound which esterified the above aromatic dicarboxylic acid component and aromatic dicarboxylic acid anhydride with lower alcohol, for example, C1-C4 alkyl alcohol, can also be used. When an ester compound obtained by esterifying an aromatic dicarboxylic acid component or an aromatic dicarboxylic acid anhydride with a lower alcohol is used, an ester bond is generated not by dehydration condensation with a diol component but by an ester exchange reaction by dealcoholization. Furthermore, a compound obtained by half-esterifying an aromatic tricarboxylic acid anhydride or an aromatic tetracarboxylic acid anhydride with a monoalcohol can be used as the aromatic dicarboxylic acid.

These aromatic dicarboxylic acid components can be used alone or in combination of two or more. Among these, terephthalic acid and isophthalic acid are preferable from the viewpoint of heat resistance and wet heat resistance.
Examples of polyvalent carboxylic acids other than aromatic dicarboxylic acids include citraconic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid , Undecanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, fumaric acid, itaconic acid, maleic acid diglycolic acid, cyclohexanone-3,5-diene-1,2-carboxylic acid, hexahydroterephthalic acid, 1,4-cyclohexane Aliphatic and alicyclic dicarboxylic acids such as dicarboxylic acid and dimer acid, succinic anhydride, maleic anhydride, glutaric anhydride, butyl succinic anhydride, hexyl succinic anhydride, octyl succinic anhydride, dodecyl succinic anhydride Butyl maleic anhydride, pentyl maleic anhydride, Silmaleic anhydride, octylmaleic anhydride, decylmaleic anhydride, dodecylmaleic anhydride, butylglutamic anhydride, hexylglutamic anhydride, heptylglutamic anhydride, octylglutamic anhydride, decylglutamic anhydride, dodecylglutamic acid Aliphatics such as anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylpentahydrophthalic anhydride, methyltrihydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylhymic anhydride, An alicyclic dicarboxylic acid anhydride is mentioned.

Polyester polymers use a diol having a hydrocarbon group in the side chain to improve the wettability of the substrate, improve heat resistance and moist heat resistance, especially when used as a laminate of optical members. There is no problem. In this invention, it is preferable to use 10-80 mol% of diol which has a hydrocarbon group in a side chain as a diol component, and it is still more preferable to use 20-40 mol%. If the amount of the diol having a hydrocarbon group in the side chain is less than 10 mol%, the heat resistance and heat and moisture resistance are poor, and when used as a laminated body of optical members, a problem such as film peeling may occur. Moreover, when it exceeds 80 mol%, there exists a tendency for a tack to fall, superposition | polymerization time becomes long, and a problem may be produced in productivity.

The hydrocarbon group in the diol having a hydrocarbon group in the side chain is preferably a linear or branched alkyl group having 1 to 10 carbon atoms, and more preferably a linear or branched alkyl group having 3 to 9 carbon atoms.
Examples of the polyol component other than the diol having a hydrocarbon group in the side chain include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexane. Diol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, bisphenol A, hydrogenated bisphenol A, polyoxyethylene glycol, polyoxypropylene glycol, polyoxy Examples thereof include ethylene polyoxytetramethylene glycol, polyoxypropylene polyoxytetramethylene glycol, and polyoxyethylene polyoxypropylene polyoxytetramethylene glycol.

Furthermore, a diol containing a sulfur atom can be used in combination. A dithiol containing a sulfur atom can also be used in combination. It is preferable to use a trihydric or higher polyhydric alcohol as the polyol component of the present invention. By using a trihydric or higher polyhydric alcohol, the polyester polymer can be branched, and thereby the cohesive force of the pressure-sensitive adhesive can be improved. When using a trihydric or higher polyhydric alcohol, it is preferable to use 0.1 to 5 mol% in the polyol component, and 0.5 to 3 mol% is more preferable in consideration of use in an optical member. If it is less than 0.1 mol%, the cohesive force may be reduced, and the heat resistance and moist heat resistance are inferior. When used as a laminate of optical members, there may be a problem such as film peeling. On the other hand, if it exceeds 5 mol%, the viscosity becomes high during synthesis, which may cause a problem in productivity.

Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6- Examples include hexanetriol.

The polyester polymer of the present invention can be obtained by polycondensing the polyvalent carboxylic acid component and the polyol component by a known method in the presence of a catalyst.

[Crosslinking agent used for polyester polymer]
Examples of the crosslinking agent used in the polyester polymer include a polyisocyanate compound, a polyfunctional silane compound, and an N-methylol group-containing compound. Among these, the polyisocyanate compound and the polyfunctional silane compound are particularly crosslinked. It is preferably used because it is excellent in the adhesiveness of the resin composition after the reaction and the adhesion to the coating layer.

Examples of the polyisocyanate compound include aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate. Of the polyisocyanate compounds, use of non-yellowing or hard yellowing polyisocyanate compounds such as 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, cyclohexyl isocyanate, etc., weather resistance, heat resistance or heat and humidity resistance From this point, it is particularly preferable.

Examples of the polyfunctional silane compound include a silane coupling agent.

The polyester pressure-sensitive adhesive of the present invention preferably contains a crosslinking agent. By the reaction between the reactive functional group in the polyester polymer and the functional group in the cross-linking agent, the resin composition is two-dimensionally cross-linked, and adhesion with the optical member can be ensured. Furthermore, since heat resistance and wet heat resistance under severe conditions can be improved, it can be preferably used for optical members.
0.001-20 mass parts is preferable with respect to 100 mass parts of polyester polymers, and, as for content of a crosslinking agent, 0.01-10 mass parts is more preferable. When the usage-amount of a crosslinking agent exceeds the said upper limit, the crosslinking density of the adhesive layer formed from a polyester adhesive and a filler will become dense, and the tack of an adhesive layer will fall. Therefore, the adhesiveness and stress relaxation property with respect to the optical member are lowered, and peeling tends to occur. On the other hand, if the amount is less than the lower limit, a sufficient cross-linked structure cannot be obtained, so that the cohesive force is lowered and the heat resistance and heat-and-moisture resistance tend to be lowered.

[Epoxy resin]
The epoxy resin is not particularly limited as long as it is a resin composed of a compound having two or more oxirane rings (epoxy groups) in one molecule, and generally has an epoxy equivalent of 90 to 2,000.
A conventionally well-known epoxy resin can be used as such an epoxy resin.
Specifically, for example, epoxy compounds having a bisphenyl group such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, bisphenol type, and polyalkylene Bifunctional glycidyl ether type epoxy resin such as glycol type, alkylene glycol type epoxy compound, epoxy compound having naphthalene ring, epoxy compound having fluorene group, phenol novolac type, orthocresol novolak type, trishydroxyphenylmethane And polyfunctional glycidyl ether type epoxy resins such as tetraphenylolethane type, and glycidyl ester type epoxy resins of synthetic fatty acids such as dimer acid.

Among these epoxy resins, the bisphenol A type is preferable because the adhesive force to the adherend is improved.

[Crosslinking agent used for epoxy resin]
The crosslinking agent used for the epoxy resin is a curing agent that cures the epoxy resin by heating, and specific examples thereof include dicyandiamide and hydrazide compounds. Of these curing agents, dicyandiamide is preferred for the reason that the adhesion to an adherend is improved.

The epoxy-based pressure-sensitive adhesive of the present invention preferably contains 0.1 to 30 parts by mass of the crosslinking agent, and more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin. When the content of the cross-linking agent is within this range, the cross-linking property of the pressure-sensitive adhesive and the adhesive property with the adherend become better.

[Additive]
The first pressure-sensitive adhesive layer 11 may contain other additives such as an antioxidant, a tackifier, a silane coupling agent, an ultraviolet absorber, a hindered amine compound light stabilizer, and a filler as necessary. May be included. Examples of the antioxidant include phenolic antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more.
Examples of the tackifier include rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, styrene resins, xylene resins, phenol resins, petroleum resins, and the like. Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers). Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds.

(Second adhesive layer)
The 2nd adhesive layer 12 is an adhesive layer which has a urethane type adhesive as a main component.
“Urethane-based adhesive” is a urethane urea resin crosslinked by a crosslinking agent. The “main component” means 50% by mass or more based on the entire pressure-sensitive adhesive layer. In terms of more excellent stress relaxation and deformation followability to an optical film such as a polarizing plate substrate, the ratio of the urethane-based adhesive to the entire second adhesive layer 12 is preferably 70% by mass or more, and 90% by mass. % Or more is more preferable.

[Urethane urea resin]
The urethane urea resin is a resin having a urethane bond and a urea bond in a polymer chain. The urethane urea resin used for the pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer 12 preferably has an ester bond and / or an ether bond in the polymer chain, and is obtained by reacting a polyol and a polyisocyanate. More preferably, the urethane prepolymer is a resin obtained by reacting a polyamino compound. At this time, a reaction terminator may be used as necessary, or a catalyst such as a tertiary amine compound or an organometallic compound may be used.
The glass transition temperature (Tg) of the urethane urea resin is preferably in the range of −80 ° C. to 0 ° C. in order to impart sufficient adhesiveness to the adhesive.
Below, the polyol, polyisocyanate, and polyamino compound which can be used for the synthesis | combination of a preferable urethane urea resin are demonstrated.

[Polyol]
Examples of the polyol that can be used for the synthesis of the urethane urea resin include polyether polyols, polyester polyols, polycarbonate polyols, copolymers thereof, and other glycols. Moreover, polyols other than these can also be used.

As the polyether polyols, compounds having two or more hydroxyl groups and ether bonds can be used. For example, polymers, copolymers, and grafts of alkylene oxides such as propylene oxide, tetrahydrofuran, ethylene oxide, and butylene oxide. Copolymers; polyether polyols by condensation of hexanediol, methylhexanediol, heptanediol, octanediol or mixtures thereof; glycols obtained by adding alkylene oxides such as ethylene oxide to bisphenols such as bisphenol A and bisphenol F Can be used.

As the polyester polyols, compounds having two or more hydroxyl groups and ester bonds can be used. For example, a polyester polyol obtained by condensation reaction of a polyfunctional alcohol component and a dibasic acid component can be used. Examples of the polyfunctional alcohol component include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3- Dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol , Cyclohexanediol, bisphenol A, bisphenol F, and the like, and compounds having two hydroxyl groups such as glycerin, trimethylolpropane, pentaerythritol and the like. Compounds having the like. Examples of the dibasic acid component include aliphatic or aromatic dibasic acids such as terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Other polyester polyols include β-butyrolactone, β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone, γ-caprolactone, γ-heptanolactone, α-methyl- β-ester polyols can also be used.

Polycarbonate polyols have a structural unit represented by — [— O—R—O—CO —] — (R represents a divalent organic group). Polycarbonate polyols can be obtained, for example, by a reaction between glycol or bisphenol and a carbonate ester, or a reaction in which phosgene is allowed to act on glycol or bisphenol in the presence of an alkali. Examples of the carbonic acid ester used in the above reaction include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, and the like. Examples of the glycol or bisphenol used in the above reaction include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, and 2-methyl-1. , 8-octanediol, 3,3′-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 , 6-hexanediol, 1,9-nonanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, or bisphenol Bisphenols such Lumpur A, bisphenol F, ethylene oxide bisphenol, mention may be made of bisphenols obtained by adding alkylene oxide such as propylene oxide.

Examples of glycols other than the above include, for example, compounds having two hydroxyl groups such as ethylene glycol, diethylene glycol, triethylene glycol, butanediol, propanediol, 1,6-hexanediol, neopentyl glycol, and cyclohexanedimethanol; glycerin , A compound having three or more hydroxyl groups such as trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol, methylglucoside; at least one ionic functional group (for example, carboxyl group, phosphate group, sulfone group, first to Polyols containing a tertiary amino group, a quaternary ammonium group, a phosphonium group, and a quaternary sulfonium group can be used.

Among the polyols, it is preferable to use a polyol having a polypropylene glycol skeleton. Among the polyols used in the present invention, the amount of the polyol having a polypropylene glycol skeleton is preferably 50 to 100% by mass with respect to 100% by mass of the polyol. The number average molecular weight of the polyol used in the present invention is preferably 800 to 4,000, and more preferably 1,000 to 3,000.

[Polyisocyanate]
Examples of the polyisocyanate that can be used for the synthesis of the urethane urea resin include aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate.

Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 ″ -triphenylmethane triisocyanate and the like can be used.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like can be used.
Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene. 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like can be used.
Examples of the alicyclic polyisocyanate include isophorone diisocyanate (also known as IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl. -2,6-cyclohexane diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanatomethyl) cyclohexane, and the like can be used.

In addition to the above, a trimethylolpropane adduct of the above polyisocyanate, a trimer having an isocyanurate ring, and the like can be used in combination. Polyphenylmethane polyisocyanate, naphthylene diisocyanate, modified polyisocyanate thereof, and the like can be used. As the polyisocyanate-modified product, a carbodiimide group, a uretdione group, a uretoimine group, a burette group reacted with water, a group of isocyanurate groups, or a modified product having two or more of these groups can be used. A reaction product of a polyol and a diisocyanate can also be used as a polyisocyanate.

[Polyamino compound]
The polyamino compound that can be used for the synthesis of the urethane urea resin is a compound having two or more amino groups. Examples of polyamino compounds include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, triaminopropane, 2,2,4-trimethylhexamethylenediamine, and 2-hydroxyethylethylenediamine. N- (2-hydroxyethyl) propylenediamine, (2-hydroxyethylpropylene) diamine, (di-2-hydroxyethylethylene) diamine, (di-2-hydroxyethylpropylene) diamine, (2-hydroxypropylethylene) Aliphatic polyamines such as diamine, (di-2-hydroxypropylethylene) diamine, and piperazine; isophorone diamine, dicyclohexylmethane-4,4′-diamine, etc. An alicyclic polyamine: phenylenediamine, xylylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, diethyltoluenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4, An aromatic diamine such as 4′-bis- (sec-butyl) diphenylmethane; and a dimer amine obtained by converting a carboxyl group of a dimer acid into an amino group, a dendrimer having a primary or secondary amino group at a terminal, and a propoxy amine at both terminals. The polyoxyalkylene glycol diamine etc. which have can be used.
As the polyamino compound used in the present invention, it is preferable to use a compound obtained by Michael addition reaction of an ethylenically unsaturated compound with a compound having two or more primary amino groups, and further, an ethylenic compound having a hydroxyl group as the ethylenically unsaturated compound. It is preferred to use unsaturated compounds.

[Crosslinking agent]
0.1-3.0 mass parts is preferable with respect to 100 mass parts of urethane urea resins, and, as for the crosslinking agent used for the adhesive of this invention, 0.2-1.5 mass parts is more preferable. If it is at least the lower limit, foaming can be suppressed, and if it is not more than the upper limit, sufficient stress relaxation performance can be provided.

The crosslinking agent used for the pressure-sensitive adhesive of the present invention preferably has a functional group such as an isocyanate group, an epoxy group, an alkoxysilyl group, a methylol group, an aziridine group, or a carbodiimide group. As the crosslinking agent, for example, polyisocyanate compounds, polyfunctional epoxy compounds, high molecular weight polycarbodiimides, N-methylol group-containing compounds, polyfunctional aziridine compounds, metal chelates and the like can be used.

As the crosslinking agent used in the pressure-sensitive adhesive of the present invention, it is particularly preferable to use a polyisocyanate compound. The polyisocyanate compound is a compound having a plurality of isocyanate groups in the molecule, and specifically, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate. Polyisocyanate compounds such as tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, Burettes, isocyanurates, and these polyisocyanates Sulfonate compound and a known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, adducts, etc. and polyisoprene polyol and the like.

Examples of the crosslinking agent other than the polyisocyanate compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, N, N, N ′. , N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine, etc. A polyfunctional aziridine compound such as 2,2′-bishydroxymethylbutanol tris [3- (1-aziridinyl) propionate], 4,4′-bis (ethyleneiminocarbonylamino) diphenylmethane; for example, aluminum, iron, Copper, sub- , Tin, titanium, nickel, antimony, magnesium, vanadium, and polyvalent metals such as chromium and zirconium, and metal chelates, such as coordination compounds with acetylacetone or ethyl acetoacetate.

[Additive]
The pressure-sensitive adhesive of the present invention may contain components other than the urethane urea resin and the crosslinking agent. For example, an acrylic resin, a polyester resin, an amino resin, an epoxy resin, or a polyurethane resin may be used in combination as a resin other than the urethane urea resin.
Further, the pressure-sensitive adhesive of the present invention includes an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, a light stabilizer such as a hindered amine compound, a filler, an ionic property as necessary. Additives such as liquids may be included. Examples of the antioxidant include phenolic antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more. As the metal corrosion inhibitor, a benzotriazole-based resin is preferable because of the compatibility and high effect of the pressure-sensitive adhesive. Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin. Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers). Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds. Examples of the ionic liquid include ionic liquids such as a nitrogen-containing onium salt, a sulfur-containing onium salt, or a phosphorus-containing onium salt, and are preferably described in paragraph numbers 0018 to 0028 of JP2011-89138A. Ionic liquids to be used. The description of paragraph numbers 0018 to 0028 in Japanese Patent Application Laid-Open No. 2011-89138 is incorporated herein as part of this specification.
The compounding amount of these additives is usually preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive layer. preferable.
In addition, the material and aspect described in Paragraph Nos. 0021 to 0105 of JP 2011-148965 A can also be adopted in the present invention, and these descriptions are cited here as a part of this specification.

[Interlayer strength between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer]
The interlayer strength between the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 of the present invention is preferably 5 N / 25 mm or more, more preferably 10 N / 25 mm or more, and 15 N / 25 mm or more. More preferably it is. When the interlayer strength is not less than the lower limit, delamination is unlikely to occur between the first adhesive layer 11 and the second adhesive layer 12 in the durability test. The interlayer strength is preferably 40 N / 25 mm or less. When the interlayer strength is less than or equal to the above upper limit value, it can be peeled off without sticking to the adherend when it is peeled again after being bonded to the adherend.

The adhesive sheet of this invention can make interlayer intensity | strength 5N / 25mm or more by making the gel fraction of a 1st adhesive layer larger than the gel fraction of a 2nd adhesive. In order to further increase the interlayer strength, for example, a method of corona treatment between the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 can be mentioned. Moreover, when manufacturing a double-sided adhesive sheet, interlayer strength can be raised by laminating | stacking the other adhesive layer before one adhesive layer forms a crosslinked structure completely. Furthermore, a double-sided pressure-sensitive adhesive sheet satisfying a desired interlayer strength can also be obtained by simultaneous multilayer coating described later.

[Gel fraction]
The gel fraction of the first pressure-sensitive adhesive layer 11 is preferably 60% or more, more preferably 60 to 90%, further preferably 65 to 85% from the viewpoint of foaming or peeling. Foaming can be suppressed if the gel fraction of the first pressure-sensitive adhesive layer 11 is equal to or greater than the lower limit, and sufficient adhesive strength can be imparted if the gel fraction is equal to or less than the upper limit. The gel fraction of the pressure-sensitive adhesive layer can be adjusted by a method for controlling the blending amount of the crosslinking agent. For example, an acrylic polymer having a weight average molecular weight of 1,500,000 (n-butyl acrylate / methyl acrylate / phenoxyethyl acrylate / 2-hydroxy acrylate = 60% by mass / 19% by mass / 20% by mass / 1% by mass) of tolylene diisocyanate In the case of crosslinking with trimethylolpropane adduct, an adhesive having a gel fraction exceeding 60% can be obtained by adding 0.2 to 1.0 part by mass of the crosslinking agent per 100 parts by mass of the acrylic polymer.

The gel fraction of the second pressure-sensitive adhesive layer 12 is preferably less than 60% and more preferably 40 to 55% from the viewpoint of preventing warpage and white spots. The gel fraction of the pressure-sensitive adhesive layer can be adjusted by, for example, a method for controlling the blending amount of the crosslinking agent. To explain with a specific example, when a urethane urea resin having a weight average molecular weight of 100,000 is crosslinked with a trimethylolpropane adduct of xylene diisocyanate, if the crosslinking agent is blended in an amount of 0.01 to 1 part by mass per 100 parts by mass of the urethane urea resin, An adhesive layer having a gel fraction of less than 60% is obtained.
The gel fraction is calculated by the following calculation formula from the weight change before and after the immersion after measuring 1 g of the pressure-sensitive adhesive immersed in 100 g of ethyl acetate for 4 days, taking out, and drying at 110 ° C. for 2 hours.
Gel fraction = (weight after immersion) / (weight before immersion) * 100 (%)

[Thickness]
The thickness of the first pressure-sensitive adhesive layer 11 is preferably 0.1 to 2.0 times the thickness of the second pressure-sensitive adhesive layer 12, and more preferably 0.3 to 1.0 times. If the thickness of the 1st adhesive layer 11 is more than the said lower limit of the thickness of the 2nd adhesive layer 12, the adhesiveness of the 1st adhesive layer 11 and an optical film will become more favorable, and the said upper limit If it is below the value, the stress relaxation performance of the second pressure-sensitive adhesive layer 12 is sufficiently functioned, and the deformation followability becomes better.
Moreover, it is preferable that the thickness of the 1st adhesive layer 11 is 1-20 micrometers, and it is more preferable that it is 5-15 micrometers. If the thickness of the 1st adhesive layer 11 is more than the said lower limit, the adhesiveness of the 1st adhesive layer 11 and an optical film will become more favorable, and if it is below the said upper limit, it will be 2nd adhesion. A double-sided pressure-sensitive adhesive sheet excellent in deformation followability can be provided without impairing the stress relaxation performance of the agent layer 12.

The thickness of the second pressure-sensitive adhesive layer 12 is preferably 1 to 30 μm, and more preferably 5 to 25 μm. If the thickness of the second pressure-sensitive adhesive layer 12 is less than or equal to the above upper limit value, it is difficult for deformation to occur during the punching process of the pressure-sensitive adhesive, and air bubbles and optical unevenness after bonding are less likely to occur, and the total thickness of the module increases. Not too much. On the contrary, if the thickness of the second pressure-sensitive adhesive layer 12 is not less than the above lower limit value, practical adhesive strength to the optical film can be easily obtained, and defects such as peeling and bubbles can be suppressed in the durability test. Moreover, since the double-sided pressure-sensitive adhesive sheet having excellent deformation followability can be provided without impairing the stress relaxation performance, it is difficult to cause a problem that causes optical defects such as white spots.

[Antistatic agent]
An antistatic agent may be contained in at least one pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet of the present invention. The double-sided pressure-sensitive adhesive sheet of the present invention is a thin film, and can exhibit antistatic performance by containing an antistatic agent in at least one pressure-sensitive adhesive layer. As an antistatic agent, an organic salt such as a metal salt or an ionic compound, which has been conventionally used for the purpose of reducing peeling charge, can be used. In the present invention, in particular, an antistatic agent is used in order to quickly neutralize the charge bias caused by the peeling electrification, so that a high electrical conductivity value is preferably 0.1 mS / cm or more.

<Double-sided PSA sheet with release sheet>
The double-sided pressure-sensitive adhesive sheet 10 is a double-sided sheet with a release sheet in which a release sheet is laminated on at least one side, preferably both sides, so that the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 are not exposed before use. It is the state of an adhesive sheet.
In FIG. 2, one Embodiment of the double-sided adhesive sheet with a peeling sheet by which the peeling sheet was laminated | stacked on the double-sided adhesive sheet 10 is shown. The double-sided pressure-sensitive adhesive sheet 20 with a release sheet of the present embodiment is a first release sheet 21 a laminated on the opposite side of the double-sided pressure-sensitive adhesive sheet 10 and the second pressure-sensitive adhesive layer 12 of the first pressure-sensitive adhesive layer 11. And the 2nd peeling sheet 21b laminated | stacked on the surface on the opposite side to the 1st adhesive layer 11 of the 2nd adhesive layer 12 is provided.

(First release sheet and second release sheet)
The first release sheet 21a and the second release sheet 21b are sheets having releasability on at least one side.
As the first release sheet 21a and the second release sheet 21b, a peelable laminated sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a low polarity group Examples of the material include polyolefin films such as polyethylene films and polypropylene films.
Papers and polymer films are used as the release sheet substrate in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone 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 silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, 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 that is an organosilicon compound having a SiO ₂ unit and (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, KS-3800, X92-183, manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

The first release sheet 21a and the second release sheet 21b are preferably different in peelability in order to facilitate peeling. That is, if the peelability of the first release sheet 21a from the first pressure-sensitive adhesive layer 11 and the peelability of the second release sheet 21b from the second pressure-sensitive adhesive layer 12 are different, the peelability is higher. It becomes easy to peel only the release sheet. In that case, what is necessary is just to adjust the peelability of the 1st peeling sheet 21a and the peelability of the 2nd peeling sheet 21b according to the bonding method and the bonding order.
A gas-generating base material that generates gas when heated, such as polycarbonate or polymethyl methacrylate, or a water-release base material that releases water, such as triacetyl cellulose, and a base material that does not generate gas, such as polyethylene terephthalate or glass When using a double-sided pressure-sensitive adhesive sheet, when pasting the double-sided pressure-sensitive adhesive sheet 10 on a gas-generating base material or moisture-releasing base material first, It is preferable that the peelability of the first release sheet 21a is lower than the peelability of the second release sheet 21b.
On the other hand, when pasting on a gas generating base material or moisture releasing base material after pasting to a base material that does not generate gas first, the peelability of the first release sheet 21a is the second release sheet. It is preferably higher than the peelability of 21b.
Usually, since it often sticks to a gas generating base material or a moisture releasing base material first, it may be preferable that the peelability of the first release sheet 21a is lower than the peelability of the second release sheet 21b. Many. The peelability is adjusted depending on the type of the release agent.

<Method for producing double-sided PSA sheet with release sheet>
As a manufacturing method of the said double-sided adhesive sheet with a peeling sheet, the following manufacturing methods (1), (2) etc. are mentioned, for example. In the present invention, the production method (2) is particularly preferred because it can be produced with a small number of steps.
Manufacturing method (1): The process which coats the coating liquid for the 1st adhesive layer formation on a peeling sheet, the 1st adhesive layer by heating the applied coating liquid for the 1st adhesive layer formation A step of forming an adhesive layer, a step of applying a second adhesive layer-forming coating solution on another release sheet, and heating the applied second adhesive layer-forming coating solution. The manufacturing method of the double-sided adhesive sheet with a peeling sheet including the process of forming 2 adhesive layers, and the process of pile | stacking and crimping | bonding so that a 1st adhesive layer and a 2nd adhesive layer may contact.
Production method (2): a step of simultaneously applying a first pressure-sensitive adhesive layer-forming coating solution and a second pressure-sensitive adhesive layer-forming coating solution onto a release sheet, and a first pressure-sensitive adhesive applied A double-sided pressure-sensitive adhesive sheet with a release sheet, comprising: heating a layer-forming coating liquid and a second pressure-sensitive adhesive layer-forming coating liquid to form a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer. Production method.
The production method (2) further includes a release sheet different from the release sheet on which the first pressure-sensitive adhesive layer-forming coating liquid and the second pressure-sensitive adhesive layer-forming coating liquid are simultaneously multilayer-coated, You may have the process of laminating | stacking on the formed double-sided adhesive sheet.

The production method (1) will be described in more detail by taking as an example the case of producing the double-sided pressure-sensitive adhesive sheet 20 with a release sheet shown in FIG. The said double-sided adhesive sheet 20 with a peeling sheet is manufactured with the following manufacturing methods, for example.
First, an acrylic polymer and a crosslinking agent and a solvent, a polyester polymer and a crosslinking agent and a solvent, or an epoxy resin, a crosslinking agent and a solvent are formed on the surface of the first release sheet 21a having releasability. And coating a first pressure-sensitive adhesive layer-forming coating solution. Here, the coating method of the first adhesive layer forming coating solution is appropriately selected from knife coaters, micro bar coaters, air knife coaters, reverse roll coaters, reverse gravure coaters, vario gravure coaters, die coaters, curtain coaters, etc. can do.
Next, by heating the coated first pressure-sensitive adhesive layer forming coating liquid, the solvent of the pressure-sensitive adhesive layer forming coating liquid is evaporated, and an acrylic polymer and a crosslinking agent or a polyester polymer are evaporated. And a crosslinking agent or an epoxy resin and a crosslinking agent are reacted to form a first pressure-sensitive adhesive layer 11 to obtain a first pressure-sensitive adhesive sheet A.
Moreover, the 2nd coating liquid for adhesive layer formation containing a urethane urea resin, a crosslinking agent, and a solvent is applied to the surface which has the mold release property of the 2nd peeling sheet 21b. Here, the coating method of the 2nd adhesive layer formation coating liquid can apply the method similar to the coating method of the 1st adhesive layer formation coating liquid.
Next, by heating the applied second adhesive layer forming coating liquid, the solvent of the adhesive layer forming coating liquid is evaporated, and the urethane urea resin and the crosslinking agent are allowed to react with each other. The second pressure-sensitive adhesive layer B is obtained.
Next, the first pressure-sensitive adhesive sheet A and the second pressure-sensitive adhesive sheet B are stacked and pressure-bonded so that the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 are in contact with each other. Get 20.

About a manufacturing method (2), the case where the double-sided adhesive sheet 20 with a peeling sheet is manufactured is mentioned as an example, and it demonstrates in detail. The said double-sided adhesive sheet 20 with a peeling sheet is manufactured with the following manufacturing methods, for example.
First, an acrylic polymer and a crosslinking agent and a solvent, a polyester polymer and a crosslinking agent and a solvent, or an epoxy resin, a crosslinking agent and a solvent are formed on the surface of the first release sheet 21a having releasability. And a first pressure-sensitive adhesive layer-forming coating solution containing, and a second pressure-sensitive adhesive layer-forming coating solution containing a urethane urea resin, a crosslinking agent, and a solvent. Here, examples of the simultaneous multilayer coating method of the first pressure-sensitive adhesive layer forming coating solution and the second pressure-sensitive adhesive layer forming coating solution include a die coating method, a slide beat coating method, and a curtain coating method. It is done. Among these, the die coating method is preferable because the risk of clogging due to drying of the coating liquid is small, and a relatively thick layer is easily formed as compared with other coating methods. Coating by each coating method can be performed using a known coating apparatus.
Then, the first adhesive layer forming coating solution and the second adhesive layer forming coating solution are heated to evaporate the solvent of each adhesive layer forming coating solution, respectively. The first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 are formed by reacting the polymer or resin with a crosslinking agent. Thereby, the laminated body C by which the 1st peeling sheet 21a was laminated | stacked on the 1st adhesive layer 11 of the double-sided adhesive sheet 20 is obtained.
Subsequently, the 2nd peeling sheet 21b is laminated | stacked on the 2nd adhesive layer 12 of the laminated body C, and the double-sided adhesive sheet 20 with a peeling sheet is obtained.
Here, an example in which the laminate C is formed by simultaneously applying the first pressure-sensitive adhesive layer forming coating liquid and the second pressure-sensitive adhesive layer forming coating liquid onto the first release sheet 21a. Although shown, the second pressure-sensitive adhesive layer-forming coating liquid and the first pressure-sensitive adhesive layer-forming coating liquid are simultaneously coated on the second release sheet 21b to form the second adhesive sheet 20 second. A laminated body in which the second release sheet 21 b is laminated on the adhesive layer 12 may be formed, and then the first release sheet 21 a may be laminated on the first adhesive layer 11.

<Transparent laminate>
Next, an embodiment of the transparent laminate of the present invention will be described. In the transparent laminate 30 of the present embodiment, a first transparent substrate 40 and a second transparent substrate 50 are bonded by the double-sided pressure-sensitive adhesive sheet 10 (see FIG. 3). The first pressure-sensitive adhesive layer 11 is in contact with the first transparent base material 40, and the second pressure-sensitive adhesive layer 12 is in contact with the second transparent base material 50.

Examples of the first transparent substrate 40 include a polycarbonate single layer sheet, a polymethyl methacrylate single layer sheet, a polycarbonate / polymethyl methacrylate laminate sheet, a triacetyl cellulose sheet, and a cycloolefin polymer sheet. A polycarbonate single-layer sheet, a polymethyl methacrylate single-layer sheet, a polycarbonate-polymethyl methacrylate laminated sheet, and a cycloolefin polymer sheet are gas-generating base materials that may generate gas when heated. The triacetylcellulose sheet is a moisture-releasing substrate that releases moisture according to environmental humidity.
When the first transparent substrate 40 is any one of a polycarbonate single layer sheet, a polymethyl methacrylate single layer sheet, and a polycarbonate / polymethyl methacrylate laminated sheet, it is used as a front plate having a protective function. The thickness of the first transparent substrate 40 used as the front plate is preferably 0.03 to 3 mm. If the thickness of the 1st transparent base material 40 is more than the said lower limit, it has sufficient rigidity and hardness, and if it is below the said upper limit, transparency will become higher.
When the 1st transparent base material 40 is a triacetyl cellulose sheet and a cycloolefin polymer sheet, it comprises a part of polarizing plate.

In the present embodiment, the second transparent base material 50 is a conductive sheet for a position input device used for a touch panel in which a conductive layer 52 is provided on one side of an insulating base material 51. Examples of the insulating base 51 constituting the conductive sheet include a glass plate and a polyethylene terephthalate film.

(Function and effect)
In the transparent laminate 30, since the double-sided pressure-sensitive adhesive sheet 10 includes the first pressure-sensitive adhesive layer 11 mainly composed of any one of an acrylic pressure-sensitive adhesive, a polyester pressure-sensitive adhesive, and an epoxy pressure-sensitive adhesive, the first transparent group Since the second adhesive layer 12 having a urethane adhesive as a main component is provided with excellent adhesion to the material 40, the deformation of the first transparent substrate 40 can be followed.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these Examples. Further, “parts” and “%” in the examples are “parts by mass” and “% by mass”, respectively, unless otherwise specified.
Moreover, the weight average molecular weight Mw is measured using a gel permeation chromatography (pump: PU-980, detector: RI-2031P1us, manufactured by JASCO Corporation) on a sample in which THF (tetrahydrofuran) is dissolved. This is the value obtained in.
The gel fraction was calculated by the following formula from the weight change before and after immersion after measuring the weight of 1 g of pressure-sensitive adhesive immersed in 100 g of ethyl acetate for 4 days, taking out and drying at 110 ° C. for 2 hours. The
Gel fraction = (weight after immersion) / (weight before immersion) * 100 (%)

Example 1
[Synthesis of the pressure-sensitive adhesive solution of the first pressure-sensitive adhesive layer] Nitrogen gas was sealed in a reactor equipped with an acrylic pressure-sensitive adhesive solution stirrer, thermometer, reflux condenser, dripping device, and nitrogen inlet tube, and then with a solvent. 105 parts by weight of ethyl acetate was added. Next, in the reactor, 55 parts by mass of methyl acrylate as a monomer component, 45 parts by mass of 2-ethylhexyl acrylate, 5.0 parts by mass of 4-hydroxybutyl acrylate, azobisisobutyro as an initiator 0.12 parts by mass of nitrile (hereinafter referred to as “AIBN”) was added to ethyl acetate so that the monomer concentration was about 50% by mass. Then, after stirring at 50 ° C. for 8 hours in a nitrogen gas stream while stirring, the polymerization reaction was stopped by quenching in an ice water bath to obtain an acrylate copolymer solution having a weight average molecular weight Mw of 1,500,000. .
0.4 parts by mass of hexamethylene diisocyanate trifunctional adduct [Asahi Kasei Co., Ltd .: P301-75E] as a cross-linking agent is added to 100 parts by mass of the solid content of this copolymer solution. It diluted so that it might become a solution with a density | concentration of 25 mass%, and the solution of adhesive A-1 was obtained.

[Synthesis of pressure-sensitive adhesive solution of second pressure-sensitive adhesive layer] Urethane-based pressure-sensitive adhesive solution 25 parts by mass of isophoronediamine (IPDA), 25 parts by mass of toluene, 19 parts by mass of 4-hydroxybutyl acrylate and 19 parts by mass of butyl acrylate After the addition, the mixture was reacted at 80 ° C. for 2 hours, and then 63 parts of toluene was added to adjust the solid content to 50% by mass to obtain an amino compound solution.
After nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube, 589 parts by weight of bifunctional polypropylene glycol, 161 parts by weight of isophorone diisocyanate, 2188 parts by weight of toluene, and dibutyl as a catalyst After 0.06 parts by mass of tin dilaurate was added and reacted at 100 ° C. for 2 hours, the mixture was cooled to 40 ° C., 804 parts by mass of ethyl acetate and 3.12 parts by mass of acetylacetone were added, and then the amino compound solution 78 described above was added. 3 parts by mass were added and aged for 1 hour.
Further, 3.5 parts by mass of 2-amino-2-methyl-propanol and 200 parts by mass of ethyl acetate were added to obtain a urethane urea resin having a weight average molecular weight Mw of 100,000.
With respect to 100 parts by mass of the solid content of the urethane urea resin, 0.7 parts by mass of diisocyanate as a crosslinking agent, 0.5 parts by mass of a silane coupling agent, and an ionic solid as an antistatic agent [manufactured by 3M, FC-4400] 0.4 mass part was mix | blended and the solution of adhesive B-1 was obtained.

[Production of double-sided PSA sheet]
As a first release sheet, prepare a release film [Oji F-Tex Co., Ltd., 38RL-07 (L)] provided with a release agent layer on a PET film, and the release agent layer of the first release sheet, The pressure-sensitive adhesive A-1 solution is applied with a knife coater to a dry film thickness of 10 μm, heated at 100 ° C. for 3 minutes to form a first pressure-sensitive adhesive layer, and a first pressure-sensitive adhesive sheet is obtained. It was. The gel fraction of this pressure-sensitive adhesive layer was 70%. In addition, as a second release sheet, a release film [38RL-07 (2)] manufactured by Oji F-Tex Co., Ltd., provided with a release agent layer having a higher release force than the first release sheet is provided on the PET film. Then, the adhesive B-1 solution was applied to the release agent layer of the second release sheet with a knife coater to a dry film thickness of 10 μm, heated at 100 ° C. for 3 minutes, and the second adhesive A layer was formed to obtain a second pressure-sensitive adhesive sheet. The gel fraction of this pressure-sensitive adhesive layer was 55%.
Subsequently, the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet are quickly overlapped and pressure-bonded so that the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are in contact with each other to obtain a double-sided pressure-sensitive adhesive sheet with a release sheet. It was.

(Example 2)
[Production of double-sided PSA sheet]
Exfoliation was carried out in the same manner as in Example 1 except that the solution of adhesive A-1 was applied to a dry film thickness of 5 μm and the solution of adhesive B-1 was applied to a dry film thickness of 15 μm. A double-sided PSA sheet with a sheet was obtained.

Example 3
[Production of double-sided PSA sheet]
Exfoliation was carried out in the same manner as in Example 1 except that the solution of adhesive A-1 was applied to a dry film thickness of 14 μm and the solution of adhesive B-1 was applied to a dry film thickness of 7 μm. A double-sided PSA sheet with a sheet was obtained.

Example 4
[Production of double-sided PSA sheet]
Peeling is performed in the same manner as in Example 1 except that the solution of the pressure-sensitive adhesive A-1 is applied so as to have a dry film thickness of 16 μm, and the solution of the pressure-sensitive adhesive B-1 is coated so as to have a dry film thickness of 4 μm. A double-sided PSA sheet with a sheet was obtained.

(Example 5)
[Synthesis of the pressure-sensitive adhesive solution of the first pressure-sensitive adhesive layer] After sealing nitrogen gas into a reaction apparatus equipped with a polyester-based pressure-sensitive adhesive solution stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube, isophthalic acid 215.7 parts by mass, sebacic acid 232.76 parts by mass, 1,4-butanediol 53.4 parts by mass, 1,6-hexanediol 70.65 parts by mass, 2-butyl-2-ethyl-1,3- 96.22 parts by mass of propanediol, 77.67 parts by mass of 2-methyl-1,3-propanediol and 3.61 parts by mass of trimethylolpropane were charged, and the temperature was raised to 160 ° C. while stirring. After confirming dehydration at 160 ° C., the temperature was raised by 10 ° C. every 30 minutes, and the temperature was raised to 250 ° C. to conduct a dehydration reaction. The reaction was further continued at 250 ° C, and when the acid value became 15 mgKOH / g or less, the temperature was lowered to 150 ° C. At 150 ° C., 0.1 part by mass of tetrabutyl titanate was added, the temperature was raised to 240 ° C., and when the temperature reached 240 ° C., the pressure was gradually reduced, and a dediol reaction was performed at 5 mmHg or less for 5 hours. The reaction was terminated after confirming that the molecular weight was reached. This polyester was dissolved in a methyl ethyl ketone / ethyl acetate mixed solution (mass ratio = 1/1) and adjusted to a solid content of 50% to obtain a polyester solution.
Toluene was added to 100 parts by mass of this polyester solution, and the solid content was adjusted to 40%. Next, 2.5 parts by mass of TDI / TMP (trimethylolpropane adduct of tolylene diisocyanate) as a crosslinking agent and 0.5 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent may be added. By stirring, a solution of adhesive C-1 was obtained.

[Production of double-sided PSA sheet]
Except having formed the 1st adhesive layer using the solution of adhesive C-1, it carried out similarly to Example 1, and obtained the double-sided adhesive sheet with a peeling sheet. The gel fraction of the pressure-sensitive adhesive layer of the first pressure-sensitive adhesive layer was 70%.

(Example 6)
[Production of double-sided PSA sheet]
As a second release sheet, prepare a release film [38RL-07 (2), manufactured by Oji F-Tex Co., Ltd.], which is provided with a release agent layer having a higher release force than the first release sheet on the PET film. The above-mentioned adhesive B-1 solution and the above-mentioned adhesive A-1 solution were applied to the release agent layer of the second release sheet with a simultaneous multilayer die head coater so that the dry film thickness was 10 μm respectively. Layer configuration of second release sheet / adhesive B-1 / adhesive A-1], after heating at 100 ° C. for 3 minutes, the first release sheet [manufactured by Oji F-Tex Co., Ltd., 38RL-07 ( L)] was bonded to the exposed adhesive layer of A-1, and a double-sided PSA sheet with a release sheet was obtained in the same manner as in Example 1.

(Comparative Example 1)
On the release agent layer of the first release sheet, the solution of the adhesive A-1 was applied with a knife coater so as to have a dry film thickness of 20 μm, heated at 100 ° C. for 3 minutes, and the first adhesive layer was Formed. Next, the second release sheet was stacked on the obtained first pressure-sensitive adhesive layer and pressure-bonded to obtain a double-sided pressure-sensitive adhesive sheet with a release sheet.
The gel fraction of the pressure-sensitive adhesive layer was 70%.

(Comparative Example 2)
Except having changed the solution of adhesive A-1 into the solution of adhesive B-1, it carried out similarly to the comparative example 1, and obtained the double-sided adhesive sheet with a peeling sheet. The gel fraction of the pressure-sensitive adhesive layer was 55%.

(Comparative Example 3)
[Synthesis of the pressure-sensitive adhesive solution of the second pressure-sensitive adhesive layer] Nitrogen gas was sealed in a reactor equipped with an acrylic pressure-sensitive adhesive solution stirrer, thermometer, reflux condenser, dripping device, and nitrogen introduction tube, and then with a solvent. 105 parts by weight of ethyl acetate was added. Next, in the reactor, 55 parts by mass of methyl acrylate as a monomer component, 45 parts by mass of 2-ethylhexyl acrylate, 5.0 parts by mass of 4-hydroxybutyl acrylate, azobisisobutyro as an initiator Nitrile (hereinafter referred to as “AIBN”) 0.12 parts by mass was added to ethyl acetate so that the monomer concentration was about 50% by mass. Then, after stirring at 50 ° C. for 8 hours in a nitrogen gas stream while stirring, the polymerization reaction was stopped by quenching in an ice water bath to obtain an acrylate copolymer solution having a weight average molecular weight Mw of 1,500,000. .
0.1 parts by mass of hexamethylene diisocyanate-based trifunctional adduct [Asahi Kasei Co., Ltd .: P301-75E] as a crosslinking agent with respect to 100 parts by mass of the solid content of this copolymer solution, ions as an antistatic agent 0.4 part by mass of a functional solid [manufactured by 3M, FC-4400] was added and diluted with ethyl acetate to a solution with a concentration of 25% by mass to obtain a solution of adhesive A-2.

[Production of double-sided PSA sheet]
Except having formed the 2nd adhesive layer using the solution of adhesive A-2, it carried out similarly to Example 1, and obtained the double-sided adhesive sheet with a peeling sheet. The gel fraction of the second pressure-sensitive adhesive layer was 55%.

(Comparative Example 4)
Peeling is performed in the same manner as in Example 1 except that the first pressure-sensitive adhesive layer is formed using the solution of pressure-sensitive adhesive B-1 and the second pressure-sensitive adhesive layer is formed using the solution of pressure-sensitive adhesive A-1. A double-sided PSA sheet with a sheet was obtained.
(Comparative Example 5)
[Synthesis of pressure-sensitive adhesive solution of second pressure-sensitive adhesive layer] Urethane-based pressure-sensitive adhesive solution 25 parts by mass of isophoronediamine (IPDA), 25 parts by mass of toluene, 19 parts by mass of 4-hydroxybutyl acrylate and 19 parts by mass of butyl acrylate After the addition, the mixture was reacted at 80 ° C. for 2 hours, and then 63 parts of toluene was added to adjust the solid content to 50% by mass to obtain an amino compound solution.
After nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube, 589 parts by weight of bifunctional polypropylene glycol, 161 parts by weight of isophorone diisocyanate, 2188 parts by weight of toluene, and dibutyl as a catalyst After 0.06 parts by mass of tin dilaurate was added and reacted at 100 ° C. for 2 hours, the mixture was cooled to 40 ° C., 804 parts by mass of ethyl acetate and 3.12 parts by mass of acetylacetone were added, and then the amino compound solution 78 described above was added. 3 parts by mass were added and aged for 1 hour.
Further, 3.5 parts by mass of 2-amino-2-methyl-propanol and 200 parts by mass of ethyl acetate were added to obtain a urethane urea resin having a weight average molecular weight Mw of 100,000.
With respect to 100 parts by mass of the solid content of this urethane urea resin, 1.4 parts by mass of diisocyanate as a crosslinking agent, 0.5 parts by mass of a silane coupling agent, and an ionic solid as an antistatic agent [manufactured by 3M, FC-4400] 0.4 mass part was mix | blended and the solution of adhesive B-2 was obtained.
[Production of double-sided PSA sheet]
Peeling is performed in the same manner as in Example 1 except that the first pressure-sensitive adhesive layer is formed using the solution of pressure-sensitive adhesive A-2, and the second pressure-sensitive adhesive layer is formed using the solution of pressure-sensitive adhesive B-2. A double-sided PSA sheet with a sheet was obtained. The gel fraction of the second pressure-sensitive adhesive layer was 70%.

(Comparative Example 6)
The prepared first pressure-sensitive adhesive sheet and second pressure-sensitive adhesive sheet were each aged for 7 days in an environment of 23 ° C. and 50%, and then the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet were combined with the first pressure-sensitive adhesive layer. A double-sided pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1 except that the double-sided pressure-sensitive adhesive sheet with a release sheet was produced by overlapping and pressing so that the second pressure-sensitive adhesive layer was in contact.

(Evaluation)
Interlaminar strength of each example and each comparative example, adhesive surface resistance value of the double-sided PSA sheet, polarizing plate adhesion of the first PSA layer, measurement of adhesion of the second PSA layer to glass, blank test, polarized light The plate durability test was evaluated as follows. The evaluation results are shown in Table 1.

[Evaluation 1: Interlayer strength]
The prepared double-sided PSA sheet with release sheet was cut to 25 mm x 50 mm, and the first PSA layer exposed by peeling the first release sheet was cut to 30 mm x 150 mm [Easily-adhesive PET film [manufactured by Toyobo Co., Ltd.] , Cosmo Shine A4300 (100 μm)], and the second pressure-sensitive adhesive layer exposed by peeling the second release sheet was bonded to the same adhesive PET film with a roll. This was subjected to autoclave treatment at 50 ° C., 0.5 MPa, and 20 min using an autoclave apparatus (YK-350S type, manufactured by Kurihara Seisakusho Co., Ltd.). Using the tensile tester [manufactured by Shimadzu Corp., Autograph], the obtained sample was measured for 180-degree peel adhesive force by a measuring method based on JIS Z0237.

[Evaluation 2: Adhesive surface resistance]
The prepared double-sided pressure-sensitive adhesive sheet with a release sheet was cut into 50 mm × 50 mm, and left still for one day in an environment of 23 ° C. and 50%. Next, the pressure-sensitive adhesive layer peeled off from the first release sheet was adhered by a measuring method based on JIS K6911 using a resistance value measuring machine (manufactured by Mitsubishi Chemical Corporation, Hiresta-UP, MCP-HT450). The surface resistance value of the agent layer was measured and evaluated according to the following criteria.
A: The glue surface resistance is very low. 10-30GΩ / □
○: Low glue surface resistance. 30 ~ 70GΩ / □
(Triangle | delta): The adhesive surface resistance value is high. 70GΩ / □ or more

[Evaluation 3: Adhesiveness of polarizing plate of first adhesive layer]
The first pressure-sensitive adhesive layer exposed by peeling off the first release sheet and the COP surface of a commercially available polarizing plate [manufactured by Nitto Denko Corporation, NPF-G1225DUNAGS1], a desktop corona treatment device [manufactured by Kasuga Denki Co., Ltd., TEC] -4AX], the corona treatment is performed so that the corona irradiation amount is 500 W · min / m ² , and the first pressure-sensitive adhesive layer is bonded to the polarizing plate COP surface with a roll to obtain a transparent laminate A. It was. The pressure-sensitive adhesive layer exposed by peeling off the second release sheet of the obtained transparent laminate A was rubbed 50 times with a load of 300 gf using a neoprene rubber (Model HS60, manufactured by Kureha Elastomer Co., Ltd.). The length of the layer peeled from the polarizing plate was measured and evaluated according to the following criteria.
○: Good adhesion between the pressure-sensitive adhesive layer and the polarizing plate. The peeled length is 20 mm or less.
X: Adhesiveness between the pressure-sensitive adhesive layer and the polarizing plate is poor. The peeled length is 20 mm or more.

[Evaluation 4: Adhesive strength of second adhesive layer to glass]
The 1st adhesive layer which peeled and exposed the 1st peeling sheet to the cycloolefin type | system | group phase difference film [the JSR company make, ARTON] was bonded with the roll, and the transparent laminated body B was obtained. The obtained transparent laminate B was cut into 25 mm × 150 mm, and the second pressure-sensitive adhesive layer exposed by peeling the second release sheet was bonded to a commercially available soda glass with a roll with a load of 2 kgf. This was subjected to autoclave treatment at 50 ° C., 0.5 MPa, and 20 min using an autoclave apparatus (YK-350S type, manufactured by Kurihara Seisakusho Co., Ltd.). The obtained transparent laminate B was allowed to stand for 1 day in an environment of 23 ° C. and 50%. Then, the adhesive force of 180 degree | times peel was measured with the measuring method based on JISZ0237 using the tensile tester [The Shimadzu Corporation make, autograph]. The adhesive residue on the glass was evaluated according to the following criteria.
: There is no adhesive residue on the glass.
Δ: Almost no adhesive residue on the glass.
X: There is adhesive residue on the entire surface of the glass.
XCF: There is adhesive residue on the entire glass surface, and the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are delaminated.

[Evaluation 5: White spot test]
The first pressure-sensitive adhesive layer exposed by peeling the first release sheet to the cycloolefin phase difference film [manufactured by JSR, ARTON] is bonded with a roll, and then the second release sheet is peeled off. The exposed second pressure-sensitive adhesive layer was bonded to a glass having a thickness of 1.1 mm with a roll. Thereafter, autoclaving was performed at 50 ° C., 0.5 MPa, and 20 min, to obtain a transparent laminate C of retardation film / adhesive layer / glass. A polarizing plate with an adhesive [F1205DU, manufactured by Nitto Denko Corporation] is further bonded onto the cycloolefin-based retardation film of the transparent laminate C to obtain a polarizing plate / adhesive layer / retardation film / adhesive layer / A transparent laminate D of glass was obtained. Two sheets of this transparent laminate D were prepared and left for 500 hours in an environment of 60 ° C. and 90%, and then placed on the upper and lower surfaces of the liquid crystal panel (made by Binitto) so as to have a crossed Nicol positional relationship. The backlight was exposed to light, and the white spots were visually observed from the top surface. Evaluation was made according to the following criteria.
○: No white spots were observed on the polarizing plate.
Δ: Slight white spots were observed on the polarizing plate.
X: White spots were observed on the polarizing plate.

[Evaluation 6: Polarizing plate durability test]
The transparent adhesive body A produced in Evaluation 1 was cut to 60 mm × 100 mm, and the second pressure-sensitive adhesive layer that was exposed by peeling off the second release sheet was coated with 0.7 mm-thick alkali-free glass [NSG -Made by Precision Co., Ltd., Corning glass, 0.7 t x 70 mm x 120 mm]. Then, the autoclave process was performed at 50 degreeC, 0.5 Mpa, and 20 min, and it left still for one day in 23 degreeC50% environment, and the transparent laminated body E was obtained. The obtained transparent laminate E was allowed to stand for 1000 hours in an 85 ° C. environment, and then evaluated according to the following criteria.
(Floating, peeling)
○: The polarizing plate or the polarizing plate / adhesive layer is not lifted from the alkali-free glass. Not peeled off.
X: The polarizing plate or the polarizing plate / adhesive layer is floating from the non-alkali glass. It is peeling off. (Foamed state)
○: No bubbles are generated at the polarizing plate / adhesive layer interface or the adhesive layer / non-alkali glass interface.
X: Bubbles are generated at the polarizing plate / adhesive layer interface or the adhesive layer / non-alkali glass interface. (Sledge)
A: When the alkali-free glass surface of the transparent laminate E is placed on a flat glass plate, the average value of the warp height at the eight outer circumferences warped from the flat glass plate is 0.05 mm or less.
(Triangle | delta): When the alkali free glass surface of the transparent laminated body E is set | placed on the flat glass plate, the curvature height average value of the outer periphery 8 point which has curved from the flat glass plate is 0.05 mm-0.2 mm.
X: When the non-alkali glass surface of the transparent laminate E is placed on a flat glass plate, the average value of the warp height at the eight outer circumferences warped from the flat glass plate is 0.2 mm or more.

The above evaluation results are summarized in Table 1.

  In all of Examples 1 to 6, the interlayer strength was 15 N / 25 mm, but in Comparative Example 5 where the gel fraction of the first pressure-sensitive adhesive layer was smaller than the gel fraction of the second pressure-sensitive adhesive layer, it was 2 N / 25 mm. It was a low value. Therefore, in Comparative Example 5, delamination occurred between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer in Evaluation 4, and there was adhesive residue on the entire glass surface. Since Comparative Example 6 also had an interlayer strength of 1 N / 25 mm, delamination occurred between the first adhesive layer and the second adhesive layer as in Comparative Example 5.

In Examples 1, 2, 3, 5, and 6, even when the second pressure-sensitive adhesive layer did not contain an antistatic agent, a sufficient antistatic function could be provided.

The transparent laminate D of Examples 1, 2, 3, 5 and 6 had better white spots than the transparent laminate D of Comparative Examples 1 and 3. This means that even when the optical film is adhered using the double-sided pressure-sensitive adhesive sheet of the present invention and then placed under high temperature and high humidity for a long time, the pressure-sensitive adhesive layer follows the dimensional change of the film with stress relaxation. This shows that the film is not distorted and the influence on the optical characteristics can be suppressed.

The transparent laminated body E of Examples 1-6 had favorable polarizing plate durability compared with the transparent laminated body E of Comparative Examples 1-6. This is because the use of the double-sided pressure-sensitive adhesive sheet of the present invention comprising the first pressure-sensitive adhesive layer having good adhesion to the polarizing plate and the second pressure-sensitive adhesive layer having good stress relaxation properties makes it possible to obtain a good transparent laminate that does not float or peel off. Shows that the body can be provided.

The double-sided pressure-sensitive adhesive sheet of the present invention can provide a transparent laminate in which the double-sided pressure-sensitive adhesive sheet is in close contact with the optical film while maintaining the display performance of the liquid crystal display device while being a thin film. This high stress relaxation property and adhesion are characterized by the main component of the first pressure-sensitive adhesive layer being one of acrylic pressure-sensitive adhesive, polyester pressure-sensitive adhesive, and epoxy pressure-sensitive adhesive, and the main component of the second pressure-sensitive adhesive layer. Can be achieved by using a urethane adhesive. Adhesive sheets with adhesive layers with different main components were thought to be difficult to produce due to poor interlayer adhesion and delamination, but increasing the interlayer strength by adjusting the gel fraction of each adhesive layer It is thought that you can. The double-sided pressure-sensitive adhesive sheet of the present invention can be effectively used for production of a display device that requires bonding of an optical film, and has high industrial applicability.

10: Double-sided pressure-sensitive adhesive sheet 11: First pressure-sensitive adhesive layer 11a: Bonding surface 12 of the first pressure-sensitive adhesive layer and second pressure-sensitive adhesive layer 12: Second pressure-sensitive adhesive layer 20: Double-sided pressure-sensitive adhesive sheet 21a with release sheet 21b: Release sheet 30: Transparent laminate 40: First transparent substrate 50: Second transparent substrate 51: Insulating substrate 52: Conductive layer

Claims (9)

A double-sided pressure-sensitive adhesive sheet for bonding a first transparent substrate and a second transparent substrate,
The double-sided PSA sheet has a first PSA layer and a second PSA layer,
The main component of the first pressure-sensitive adhesive layer is any one of an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and an epoxy-based pressure-sensitive adhesive, and the main component of the second pressure-sensitive adhesive layer is a urethane-based pressure-sensitive adhesive.
The gel fraction of the first adhesive layer is greater than the gel fraction of the second adhesive layer,
The interlayer strength between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is 5 N / 25 mm or more,
The first pressure-sensitive adhesive layer is in contact with the first transparent base material, the second pressure-sensitive adhesive layer is in contact with the second transparent base material, and the first transparent base material is a polycarbonate single layer sheet, a polymethyl methacrylate single layer. A double-sided pressure-sensitive adhesive sheet, which is any one of a sheet, a polycarbonate / polymethyl methacrylate laminate sheet, a triacetyl cellulose sheet, and a cycloolefin polymer sheet. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the first pressure-sensitive adhesive layer has a thickness of 1 to 20 µm, and the second pressure-sensitive adhesive layer has a thickness of 1 to 30 µm. The gel fraction of the first pressure-sensitive adhesive layer is 60% or more,
The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the gel fraction of the second pressure-sensitive adhesive layer is less than 60%. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the first pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein an antistatic agent is contained in at least one of the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer. A double-sided pressure-sensitive adhesive sheet with a release sheet, wherein the release sheet is laminated on at least one side of the double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5. The step of coating the first adhesive layer forming coating solution on the release sheet, and heating the applied first adhesive layer forming coating solution to form the first adhesive layer. A step of coating a second pressure-sensitive adhesive layer-forming coating solution on the other release sheet, and heating the second pressure-sensitive adhesive layer-forming coating solution to form the second pressure-sensitive adhesive. The double-sided pressure-sensitive adhesive sheet with a release sheet according to claim 6, comprising a step of forming a layer, and a step of overlapping and pressure-bonding so that the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are in contact with each other. Production method. A step of simultaneously applying a first pressure-sensitive adhesive layer-forming coating liquid and a second pressure-sensitive adhesive layer-forming coating liquid on a release sheet, and a first pressure-sensitive adhesive layer-forming coating liquid applied And a step of heating the second pressure-sensitive adhesive layer-forming coating solution to form the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer. A method for producing an adhesive sheet. The transparent laminated body by which the 1st transparent base material and the 2nd transparent base material were bonded by the double-sided adhesive sheet of any one of Claims 1-5.

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