JP2022179181A - Adhesive composition, adhesive sheet, optical laminate and image display device - Google Patents

Abstract

Kind Code: A1 A pressure-sensitive adhesive composition suitable for forming a pressure-sensitive adhesive sheet capable of suppressing dimensional change of an optical film contained in an optical laminate and ensuring durability is provided.
A pressure-sensitive adhesive composition provided contains a (meth)acrylic polymer (A) as a main component, and further contains a cross-linking agent (B). The amount of the cross-linking agent (B) to be blended is 5 parts by weight or more per 100 parts by weight of the (meth)acrylic polymer (A). Assuming the self-polymer (C) of the cross-linking agent (B), the distance Ra of the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) is 12. 3 or less.
[Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, an adhesive sheet, an optical laminate and an image display device.

2. Description of the Related Art In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have rapidly spread. These various image display devices usually have a laminated structure of an image forming layer such as a liquid crystal layer and an EL light emitting layer, and an optical laminate including an optical film and an adhesive sheet. The pressure-sensitive adhesive sheet is mainly used for bonding between films included in the optical layered body and bonding between the image forming layer and the optical layered body. Examples of the optical film are a polarizing plate, a retardation film, and a polarizing plate with a retardation film in which the polarizing plate and the retardation film are integrated. Patent Documents 1 and 2 disclose an example of an optical layered body.

JP 2008-031214 A JP 2009-98665 A

Excessive changes in the dimensions of the optical film due to temperature changes cause light leakage and color unevenness in image display devices. Light leakage and color unevenness are particularly likely to occur in a relatively large-sized image display device using a polarizing plate with a retardation film. In addition, image display devices designed with a narrow bezel (narrow bezel) are becoming popular, and suppression of dimensional change is becoming more and more important. In order to suppress the dimensional change, it is conceivable to increase the elastic modulus of the pressure-sensitive adhesive sheet included in the optical layered body. However, simply increasing the elastic modulus may reduce the durability of the pressure-sensitive adhesive sheet, making it impossible to follow changes in dimensions.

An object of the present invention is to provide a pressure-sensitive adhesive composition suitable for forming a pressure-sensitive adhesive sheet in which the dimensions of an optical film included in an optical laminate can be suppressed and durability is ensured.

The present invention
(Meth) acrylic polymer (A) as a main component,
further comprising a cross-linking agent (B),
The amount of the cross-linking agent (B) is 5 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A),
Assuming the self-polymer (C) of the cross-linking agent (B), the distance Ra of the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) is 12.3 or less, a pressure-sensitive adhesive composition,
I will provide a.

In another aspect, the invention provides a
A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition of the present invention,
I will provide a.

In another aspect, the invention provides a
An optical laminate comprising the adhesive sheet of the present invention and an optical film,
I will provide a.

In another aspect, the invention provides a
an image display device comprising the optical layered body of the present invention;
I will provide a.

The pressure-sensitive adhesive composition according to the present invention is suitable for forming a pressure-sensitive adhesive sheet capable of suppressing dimensional change of the optical film contained in the optical laminate and ensuring durability.

FIG. 1 is a cross-sectional view schematically showing an example of the pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the optical layered body of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of the optical layered body of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of the optical layered body of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of the optical layered body of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of the image display device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown below.

As used herein, "(meth)acryl" means acryl and methacryl. Moreover, "(meth)acrylate" means acrylate and methacrylate.

[Adhesive composition]
The pressure-sensitive adhesive composition (I) of the present embodiment contains a (meth)acrylic polymer (A) and a cross-linking agent (B). The (meth)acrylic polymer (A) is contained in the pressure-sensitive adhesive composition (I) as a main component. In other words, the pressure-sensitive adhesive composition (I) is an acrylic pressure-sensitive adhesive composition. A main component means the component with the largest content rate also in a composition. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 73% by weight or more, or even 75% by weight or more.

The amount of the cross-linking agent (B) to be blended is 5 parts by weight or more per 100 parts by weight of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition (I) having a blending amount within the above range is suitable for forming a pressure-sensitive adhesive sheet having an increased elastic modulus.

According to the studies of the present inventors, when the blending amount reaches the above range, the cross-linking agent (B) reacts with each other during the formation of the pressure-sensitive adhesive sheet, facilitating the formation of a self-polymer of the cross-linking agent (B). The formation of the self-polymer increases the cohesive force of the adhesive sheet, thereby contributing to the formation of the adhesive sheet that can suppress the dimensional change of the optical film. However, according to further studies, when the compatibility between the (meth)acrylic polymer (A) and the self-polymer is low, the durability of the pressure-sensitive adhesive sheet tends to decrease. A possible reason for the decrease is that an independent region rich in self-polymer tends to occur inside the pressure-sensitive adhesive sheet. The formation of the above areas can cause voids and the like due to progress of peeling at the interfaces of the areas when the pressure-sensitive adhesive sheet is deformed by an external force. In the adhesive composition of the present embodiment, assuming the self-polymer (C) of the cross-linking agent (B), the Hansen solubility between the (meth)acrylic polymer (A) and the self-polymer (C) The parameter (HSP) distance Ra is 12.3 or less. The smaller the distance Ra, the higher the compatibility between the polymers. Therefore, the pressure-sensitive adhesive composition of the present embodiment is suitable for forming a pressure-sensitive adhesive sheet in which durability is ensured.

The Hansen Solubility Parameter (HSP) is the solubility parameter introduced by Hildebrand divided into three components: the dispersion term δD, the polarization term δP and the hydrogen bonding term δH. δD indicates the energy derived from the intermolecular dispersion force. δP indicates the energy derived from intermolecular polar forces. δH indicates energy derived from intermolecular hydrogen bonding force. The unit of each component is usually MPa ^1/2 . The three components define a point (vector) in a three-dimensional space known as Hansen's space. The distance Ra is defined by points (D _A , P _A , H _A ) corresponding to the (meth)acrylic polymer (A) and points (D _C , P _C , H _C ) and can be calculated by the formula: {4×(δD _A −δD _B ) ² +(δP _A −δP _B ) ² +(δH _A −δH _B ) ² } ^1/2 . Details of the Hansen Solubility Parameters are disclosed in "Hansen Solubility Parameters; A Users Handbook" (CRC Press, 2007). δD, δP and δH of the polymer can be determined by calculation using known software such as HSPiP (version 5) based on the constituent units possessed by the polymer and the content of such units in the polymer. More specifically, δD, δP and δH of each structural unit are individually calculated, and the weighted average value obtained by weighting the calculated δD, δP and δH by the content of the unit is used as the δD, δH of the polymer. δP and δH. However, the calculation is performed at a temperature of 23°C. Note that the calculated values of .delta.D, .delta.P and .delta.H may differ slightly depending on the software used. However, the difference is usually negligible in determining Ra. Hansen Solubility Parameters for crosslinkers are calculated only for those that form self-polymers.

The distance Ra is 12.25 or less, 12.2 or less, 12.15 or less, 12.1 or less, 12.05 or less, 12.0 or less, 11.95 or less, 11.9 or less, 11.85 or less, 11 0.8 or less, 11.75 or less, or even 11.7 or less. The lower limit of the distance Ra is, for example, 6 or more.

[(Meth) acrylic polymer (A)]
The (meth)acrylic polymer (A) preferably has, as a main unit, a structural unit derived from the (meth)acrylic monomer (A1) having an alkyl group having 1 to 30 carbon atoms in the side chain. The alkyl group may be linear or branched. The (meth)acrylic polymer (A) may have one or more structural units derived from the (meth)acrylic monomer (A1). Examples of (meth) acrylic monomers (A1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate. , isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate ( Lauryl (meth)acrylate), n-tridecyl (meth)acrylate and n-tetradecyl (meth)acrylate. As used herein, the term "main unit" refers to the total structural units of the polymer, for example 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more. means unit.

The (meth)acrylic polymer (A) may have structural units derived from the (meth)acrylic monomer (A1) having a long-chain alkyl group in the side chain. An example of said monomer (A1) is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). As used herein, the term "long-chain alkyl group" means an alkyl group having 6 to 30 carbon atoms.

The (meth)acrylic polymer (A) is a structural unit derived from the (meth)acrylic monomer (A1) having a glass transition temperature (Tg) in the range of −70 to −20° C. when homopolymerized. may have An example of said monomer (A1) is n-butyl acrylate.

The (meth)acrylic polymer (A) may have structural units other than the structural unit derived from the (meth)acrylic monomer (A1). The structural unit is derived from the monomer (A2) copolymerizable with the (meth)acrylic monomer (A1). The (meth)acrylic polymer (A) may have one or more of these structural units.

Examples of monomers (A2) are aromatic ring-containing monomers. The aromatic ring-containing monomer may be an aromatic ring-containing (meth)acrylic monomer. Examples of aromatic ring-containing monomers include phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide-modified nonylphenol (meth) acrylate, hydroxyethylated β- naphthol (meth)acrylate and biphenyl (meth)acrylate. The content of structural units derived from aromatic ring-containing monomers in the (meth)acrylic polymer (A) is, for example, 0 to 50% by weight, 1 to 30% by weight, 5 to 25% by weight, 8 to 20% by weight. % by weight, 10-18% by weight, 12-16% by weight, or even 12-16% by weight. Having a structural unit derived from an aromatic ring-containing monomer in the (meth)acrylic polymer (A) is a phase between the (meth)acrylic polymer (A), the cross-linking agent (B), and its self-polymer. It can contribute to the improvement of solubility.

Another example of monomer (A2) is a hydroxyl-containing monomer. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylic monomer. Examples of hydroxyl-containing monomers are 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( hydroxyalkyl (meth)acrylates such as meth)acrylates, 10-hydroxydecyl (meth)acrylate and 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methylacrylate. In addition, the hydroxyl group can react with various cross-linking agents. From the viewpoint of improving the uniformity of the crosslinked structure to be formed, the content of structural units derived from hydroxyl group-containing monomers in the (meth)acrylic polymer (A) may be 1% by weight or less. It may be 5% by weight or less, further 0.1% by weight or less, or 0% by weight (without including the structural unit).

The monomer (A2) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of carboxyl group-containing monomers are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid. Examples of amino group-containing monomers are N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide group-containing monomers are (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N- Butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, mercaptomethyl (Meth) acrylamide-based monomers such as mercaptoethyl (meth) acrylamide; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

Monomer (A2) may be a polyfunctional monomer. Examples of multifunctional monomers are hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (Poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri( polyfunctional acrylates such as meth)acrylates, tetramethylolmethane tri(meth)acrylates, allyl (meth)acrylates, vinyl (meth)acrylates, epoxy acrylates, polyester acrylates and urethane acrylates; and divinylbenzene. Polyfunctional acrylates are preferably 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

The total content of structural units derived from the carboxyl group-containing monomer, amino group-containing monomer, amide group-containing monomer and polyfunctional monomer in the (meth)acrylic polymer (A) is preferably is 20% by weight or less, more preferably 10% by weight or less, and still more preferably 8% by weight or less. When the (meth)acrylic polymer (A) has the structural unit, the total content is, for example, 0.01% by weight or more, and may be 0.05% by weight or more. The (meth)acrylic polymer (A) may not contain structural units derived from polyfunctional monomers. When the (meth)acrylic polymer (A) has a structural unit derived from a carboxyl group-containing monomer, particularly acrylic acid, and/or a structural unit derived from an amide group-containing monomer, for example, cross-linking Self-polymerization of the agent (B) can be enhanced. Improvement of the self-polymerization of the cross-linking agent (B) can contribute to suppression of peeling of the pressure-sensitive adhesive sheet in a humidified environment, and stabilization of physical properties of the pressure-sensitive adhesive sheet in a system having a high content of the cross-linking agent (B). .

Examples of other monomers (A2) include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and 3-methoxy (meth)acrylate. Alkoxyalkyl (meth)acrylates such as propyl, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate and 4-ethoxybutyl (meth)acrylate; glycidyl (meth)acrylate and ( Epoxy group-containing monomers such as methyl glycidyl acrylate; sulfonic acid group-containing monomers such as sodium vinyl sulfonate; phosphoric acid group-containing monomers; cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate and (meth)acrylic acid esters having an alicyclic hydrocarbon group such as isobornyl (meth)acrylate; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; ethylene, propylene olefins, such as butadiene, isoprene and isobutylene, or dienes; vinyl ethers, such as vinyl alkyl ether; and vinyl chloride.

The total content of structural units derived from the other monomer (A2) in the (meth)acrylic polymer (A) is, for example, 30% by weight or less, and may be 10% by weight or less, or 0 % by weight (not including the structural unit).

The (meth)acrylic polymer (A) can be formed by polymerizing one or more of the above monomers by a known method. A monomer and a partial polymer of the monomer may be polymerized. Polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. Solution polymerization and active energy ray polymerization are preferred because they can form a pressure-sensitive adhesive sheet with excellent optical transparency. Polymerization is preferably carried out while avoiding contact of the monomer and/or partial polymer with oxygen. Polymerization in shutdown can be employed. The (meth)acrylic polymer (A) to be formed may be in any form such as a random copolymer, a block copolymer, or a graft copolymer.

The polymerization system forming the (meth)acrylic polymer (A) may contain one or more polymerization initiators. The type of polymerization initiator can be selected depending on the polymerization reaction, and may be, for example, a thermal polymerization initiator or a photopolymerization initiator.

Solvents used for solution polymerization include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. However, the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

Polymerization initiators used for solution polymerization are, for example, azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators. Peroxide polymerization initiators are, for example, dibenzoyl peroxide and t-butyl permaleate. Among them, the azo polymerization initiator disclosed in JP-A-2002-69411 is preferable. The azo polymerization initiator, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis (2-methylpropion acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The amount of the azo polymerization initiator used is, for example, 0.05 to 0.5 parts by weight, and may be 0.1 to 0.3 parts by weight, per 100 parts by weight of the total amount of the monomers.

Active energy rays used for active energy ray polymerization include, for example, ionizing radiation such as α rays, β rays, γ rays, neutron beams and electron beams, and ultraviolet rays. The active energy rays are preferably ultraviolet rays. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. A polymerization system for active energy ray polymerization typically contains a photopolymerization initiator. Polymerization conditions for active energy polymerization are not limited as long as the (meth)acrylic polymer (A) is formed.

Photopolymerization initiators include, for example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, and photoactive oxime-based photopolymerization initiators. , a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. However, the photopolymerization initiator is not limited to the above examples.

Benzoin ether-based photopolymerization initiators include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, anisolemethyl is ether. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-butyl)dichloro Acetophenone. Examples of α-ketol photopolymerization initiators are 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. The aromatic sulfonyl chloride photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. A photoactive oxime-based photopolymerization initiator is, for example, 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. A benzoin-based photopolymerization initiator is, for example, benzoin. A benzylic photopolymerization initiator is, for example, benzyl. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. A ketal photopolymerization initiator is, for example, benzyl dimethyl ketal. Thioxanthone-based photopolymerization initiators are, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

The amount of the photopolymerization initiator used is, for example, 0.01 to 1 part by weight, and may be 0.05 to 0.5 part by weight, per 100 parts by weight of the total amount of the monomers.

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is, for example, 1,000,000 to 2,800,000, and from the viewpoint of the durability and heat resistance of the pressure-sensitive adhesive sheet, it is 1,200,000 or more, further 1,400,000 or more. may be The weight average molecular weight (Mw) of polymers and oligomers in this specification is a value (converted to polystyrene) based on GPC (gel permeation chromatography) measurement.

The content of the (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition (I) is, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, and further 80% by weight in terms of solid content. or more. The upper limit of the content is, for example, 99% by weight or less, and may be 97% by weight or less, 95% by weight or less, 93% by weight or less, or even 90% by weight or less.

[Crosslinking agent (B)]
Cross-linking agent (B) is typically a polyfunctional cross-linking agent having two or more cross-linking reactive groups per molecule. The cross-linking agent (B) may be a tri- or higher functional cross-linking agent having 3 or more cross-linking reactive groups per molecule. The tri- or higher functional cross-linking agent (B) tends to form a self-polymer. The upper limit of the number of cross-linking reactive groups per molecule is 5, for example.

The cross-linking agent (B) is, for example, an isocyanate-based cross-linking agent. The isocyanate-based cross-linking agent contains an isocyanate group as a cross-linking reactive group. The isocyanate-based cross-linking agent (B) may be an aromatic isocyanate compound, an alicyclic isocyanate compound, or an aliphatic isocyanate compound.

Examples of aromatic isocyanate compounds that can be used for the cross-linking agent (B) include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, and 4,4′-diphenylmethane. diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate and 1,5-naphthalene diisocyanate, xylylene diisocyanate.

Examples of alicyclic isocyanate compounds that can be used for the cross-linking agent (B) include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xyloxy diisocyanate, hydrogenated tolylene diisocyanate and hydrogenated tetramethylxylylene diisocyanate.

Examples of aliphatic isocyanate compounds that can be used as the cross-linking agent (B) include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, and dodecamethylene diisocyanate. and 2,4,4-trimethylhexamethylene diisocyanate.

The cross-linking agent (B) may be a derivative of the above isocyanate compound. Examples of derivatives include multimers (dimers, trimers, pentamers, etc.), adducts (adducts) obtained by adding polyhydric alcohols such as trimethylolpropane, urea modified products, and biuret modified products. , allophanate-modified, isocyanurate-modified, carbodiimide-modified, and urethane prepolymers obtained by addition to polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, and the like.

The cross-linking agent (B) is preferably an aromatic isocyanate compound or a derivative thereof, more preferably tolylene diisocyanate or a derivative thereof (in other words, a tolylene diisocyanate-based (TDI-based) cross-linking agent). TDI-based cross-linking agents are superior to xylylene diisocyanate and its derivatives (in other words, xylylene diisocyanate-based (XDI-based) cross-linking agents) in terms of reaction uniformity. An example of a TDI-based cross-linking agent is an adduct of tolylene diisocyanate and a polyfunctional alcohol, and a more specific example is a trimethylolpropane/tolylene diisocyanate trimer adduct.

Commercially available products can be used as the cross-linking agent (B). Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL and Coronate HX (manufactured by Tosoh; all trade names), Takenate D-102 and Takenate D. -103, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500 and Takenate 600 (manufactured by Mitsui Chemicals; Both are trade names). As the cross-linking agent (B), Coronate L, Takenate D-102 and Takenate D-103 (all of which are trimethylolpropane/tolylene diisocyanate trimer adducts) can be preferably used.

The amount of the cross-linking agent (B) in the adhesive composition (I) is 5 parts by weight or more, 6 parts by weight or more, and 7 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). , 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, more than 10 parts by weight, or even 11 parts by weight or more. The upper limit of the compounding amount is, for example, 30 parts by weight or less, 28 parts by weight or less, 25 parts by weight or less, 23 parts by weight or less, 20 parts by weight or less, 19 parts by weight or less, 18 parts by weight or less, and further 15 parts by weight or less. may be

The pressure-sensitive adhesive composition (I) may contain one or more cross-linking agents (B). When two or more cross-linking agents (B) are included, at least one cross-linking agent (B), for example, the self-polymer (C) of the cross-linking agent (B) with the largest blending amount, the distance Ra as long as it satisfies the range. The distance Ra may satisfy the above range for all self-polymers (C) of cross-linking agents (B) contained.

The self-polymer (C) assumed in the calculation of the distance Ra is a single polymer composed of structural units derived from the cross-linking agent (B). However, the self-polymer of the cross-linking agent (B) actually contained in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (I) contains structural units other than the structural units derived from the cross-linking agent (B). sometimes

The pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (I) has an interpenetrating network (IPN) structure of a cross-linked product of the (meth)acrylic polymer (A) and a self-polymer of the cross-linking agent (B). may be The IPN structure is suitable for improving the durability of the adhesive sheet.

Other examples of cross-linking agents (B) are peroxide-based cross-linking agents, epoxy-based cross-linking agents, imine-based cross-linking agents and polyfunctional metal chelates. However, the cross-linking agent (B) is preferably isocyanate-based. When the pressure-sensitive adhesive composition (I) contains a cross-linking agent (B) other than an isocyanate type, the total amount is 0.1 to 5 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A). parts are preferred, and 0.1 to 3 parts by weight, 0.1 to 2 parts by weight and 0.1 to 1 part by weight, in that order, are more preferred. The pressure-sensitive adhesive composition (I) may not contain a cross-linking agent (B) other than an isocyanate-based cross-linking agent, such as an epoxy-based cross-linking agent.

[(Meth) acrylic oligomer]
The pressure-sensitive adhesive composition (I) may further contain a (meth)acrylic oligomer (D).

The (meth)acrylic oligomer (D) can have the same composition as the (meth)acrylic polymer (A) described above, except that the weight average molecular weight (Mw) is different. The weight average molecular weight (Mw) of the (meth)acrylic oligomer (D) is, for example, 1000 or more, and may be 2000 or more, 3000 or more, or even 4000 or more. The upper limit of the weight average molecular weight (Mw) of the (meth)acrylic oligomer is, for example, 30,000 or less, and may be 15,000 or less, 10,000 or less, or even 7,000 or less.

The (meth)acrylic oligomer (D) has, for example, one or more structural units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, propyl ( meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, Alkyl (meth)acrylates such as isodecyl (meth)acrylate, undecyl (meth)acrylate and dodecyl (meth)acrylate; (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate Esters of acrylic acid and alicyclic alcohols; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.

The (meth)acrylic oligomer (D) preferably has structural units derived from a (meth)acrylic monomer having a relatively bulky structure. In this case, the adhesiveness of the adhesive sheet can be further enhanced. Examples of the acrylic monomer include alkyl (meth)acrylates having a branched alkyl group such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. and esters of (meth)acrylic acid and alicyclic alcohols such as dicyclopentanyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate. The monomer preferably has a cyclic structure, more preferably two or more cyclic structures. In addition, when the (meth)acrylic oligomer (D) is polymerized and/or the pressure-sensitive adhesive sheet is formed when UV irradiation is performed, the progress of polymerization and/or formation is hardly inhibited. It preferably does not have an unsaturated bond, and for example, an alkyl (meth)acrylate having an alkyl group with a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

Specific examples of the (meth)acrylic oligomer (D) include a copolymer of butyl acrylate, methyl acrylate and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, and a copolymer of cyclohexyl methacrylate and isobornyl methacrylate. Copolymers of cyclohexyl methacrylate and acryloylmorpholine, copolymers of cyclohexyl methacrylate and diethylacrylamide, copolymers of 1-adamantyl acrylate and methyl methacrylate, copolymers of dicyclopentanyl methacrylate and isobornyl methacrylate. Polymer, copolymer of methyl methacrylate and at least one selected from dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate and cyclopentanyl methacrylate, homopolymer of dicyclopentanyl acrylate , a homopolymer of 1-adamantyl methacrylate and a homopolymer of 1-adamantyl acrylate.

For the polymerization of the (meth)acrylic oligomer (D), the above-described polymerization method for the (meth)acrylic polymer (A) can be employed.

When the pressure-sensitive adhesive composition (I) contains the (meth)acrylic oligomer (D), the amount thereof is, for example, 70 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer (A), It may be 50 parts by weight or less, or even 40 parts by weight or less. The lower limit of the amount to be blended is, for example, 1 part by weight or more, 2 parts by weight or more, and may be 3 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition (I) may not contain the (meth)acrylic oligomer (D).

[Additive]
The pressure-sensitive adhesive composition (I) may contain other additives. Examples of additives include silane coupling agents, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, rework improvers, softeners, antioxidants, aging Inhibitors, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (ionic compounds such as alkali metal salts, ionic liquids, ionic solids, etc.), inorganic fillers, organic fillers, powders such as metal powders , particles, and foils. The additive can be blended in an amount of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 1 part by weight or less per 100 parts by weight of the (meth)acrylic polymer (A).

Examples of silane coupling agents are 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 2-(3,4-epoxycyclohexyl)ethyl Epoxy group-containing silane coupling agents such as trimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3 -dimethylbutylidene)propylamine and amino group-containing silane coupling agents such as N-phenyl-γ-aminopropyltrimethoxysilane; ) acrylic group-containing silane coupling agents; and isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane.

When the pressure-sensitive adhesive composition (I) contains a silane coupling agent, the amount is, for example, 5 parts by weight or less, 3 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A), It may be 1 part by weight or less, 0.5 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, or even 0.05 parts by weight or less. The adhesive composition (I) may not contain a silane coupling agent.

Types of the pressure-sensitive adhesive composition (I) are, for example, emulsion type, solvent type (solution type), active energy ray-curable type (photocurable type), and heat-melting type (hot-melt type). The pressure-sensitive adhesive composition (I) may be solvent-based from the viewpoint of forming a pressure-sensitive adhesive sheet with superior durability. The solvent-based pressure-sensitive adhesive composition (I) may not contain a photocuring agent such as an ultraviolet curing agent.

[Adhesive sheet]
An example of the adhesive sheet of this embodiment is shown in FIG. The pressure-sensitive adhesive sheet 1 in FIG. 1 is formed from the pressure-sensitive adhesive composition (I). The adhesive sheet 1 contains, for example, a crosslinked product of (meth)acrylic polymer (A). The adhesive sheet 1 can be formed from the adhesive composition (I) as follows.

For the solvent type, for example, the pressure-sensitive adhesive composition (I) or a mixture of the pressure-sensitive adhesive composition (I) and a solvent is applied to the base film, and the formed coating film is dried to form the pressure-sensitive adhesive sheet 1. . The pressure-sensitive adhesive composition (I) is thermally cured by heat during drying. For the active energy ray-curable type (photocurable type), for example, a monomer (group) that becomes a (meth)acrylic polymer (A) by polymerization, a cross-linking agent (B), and, if necessary, a monomer A mixture of the partial polymer of (group), polymerization initiator, oligomer (D), other cross-linking agent, additive, solvent, etc. is applied to the substrate film and irradiated with active energy rays to form a pressure-sensitive adhesive sheet 1. . The solvent may be removed by drying before irradiation with active energy rays. The base film may be a film (release film) whose coating surface has been subjected to release treatment.

The adhesive sheet 1 formed on the base film can be transferred to any layer. Moreover, the base film may be an optical film, and in this case, an optical laminate including the adhesive sheet 1 and the optical film is obtained.

A known method can be employed for application to the substrate film. Coating is, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, or the like. can be implemented by

For the solvent type, the drying temperature after coating is, for example, 40-200°C. The drying temperature may be 160° C. or lower, 150° C. or lower, 130° C. or lower, 120° C. or lower, or even 100° C. or lower. By setting the drying temperature to 130° C. or lower, 120° C. or lower, or further 100° C. or lower, the adhesive sheet 1 having excellent durability can be obtained. In other words, the adhesive sheet 1 may be obtained by drying the coating film of the adhesive composition (I) at a temperature of 130° C. or lower, 120° C. or lower, or further 100° C. or lower. The drying time is, for example, 5 seconds to 20 minutes, and may be 5 seconds to 10 minutes, or even 10 seconds to 5 minutes. For the active energy ray-curable type, the drying temperature and drying time when drying after coating may be within the above ranges.

Compositions and mixtures applied to the base film preferably have a viscosity suitable for handling and application. Therefore, for the active energy ray-curable type, the mixture to be applied preferably contains a partial polymer of the monomer (group).

In one example of the release film, the coated surface is subjected to release treatment with a silicone compound.

The thickness of the adhesive sheet 1 is, for example, 1 to 200 μm, may be 5 to 150 μm, and may be 10 to 100 μm.

The storage elastic modulus G′ (25° C.) of the adhesive sheet 1 is, for example, 0.15 MPa or higher, 0.2 MPa or higher, 0.25 MPa or higher, 0.3 MPa or higher, 0.4 MPa or higher, 0.5 MPa or higher, 0.5 MPa or higher, and 0.2 MPa or higher. It may be 6 MPa or more, 0.7 MPa or more, 0.8 MPa or more, 0.9 MPa or more, 1.0 MPa or more, 1.1 MPa or more, or even 1.2 MPa or more. The upper limit of the storage modulus G' (25°C) is, for example, 5 MPa or less, and may be 3.0 MPa or less, 2.5 MPa or less, or even 2.0 MPa or less. The pressure-sensitive adhesive sheet 1 having a storage elastic modulus G' within the above range is more suitable for suppressing changes in the dimensions of the optical film.

The storage elastic modulus (25° C.) of PSA Sheet 1 can be evaluated by the following method. First, a sample for measurement made of the material constituting the adhesive sheet 1 is prepared. The shape of the measurement sample is disc-shaped. The measurement sample has a bottom diameter of 8 mm and a thickness of 2 mm. A sample for measurement may be obtained by punching a disc-shaped laminate from a laminate in which a plurality of pressure-sensitive adhesive sheets 1 are laminated. Next, a dynamic viscoelasticity measurement is performed on the measurement sample. For dynamic viscoelasticity measurement, for example, ARES-G2 manufactured by TA Instruments can be used. From the results of the dynamic viscoelasticity measurement, the storage elastic modulus G' of the pressure-sensitive adhesive sheet 1 at 25°C can be specified. The conditions for the dynamic viscoelasticity measurement are as follows.
・Measurement conditions Frequency: 1Hz
Deformation mode: Torsion Measurement temperature: -70°C to 150°C
Heating rate: 5°C/min

The gel fraction of the adhesive sheet 1 is, for example, 60% or more, 65% or more, and may be 70% or more. The upper limit of the gel fraction is, for example, 99% or less, and may be 98% or less, or even 95% or less. The adhesive sheet 1 having a gel fraction within the above range is more suitable for suppressing dimensional change of the optical film.

The gel fraction of the adhesive sheet 1 can be evaluated by the following method. First, about 0.2 g is scraped from Adhesive Sheet 1 to obtain a small piece. Next, the obtained small piece is wrapped with an expanded porous membrane of polytetrafluoroethylene (NTF1122 manufactured by Nitto Denko, average pore size 0.2 μm) and tied with a kite string to obtain a test piece. Next, the weight A of the obtained test piece is measured. Weight A is the sum of the weights of the adhesive sheet piece, the stretched porous membrane and the kite string. The total weight B of the stretched porous membrane and the kite string used is measured in advance. Next, the test piece is immersed in a container with an internal volume of 50 mL filled with ethyl acetate and allowed to stand at 23° C. for one week. After standing still, the test piece is taken out from the container, dried for 2 hours in a dryer set at 130° C., and then the weight C of the test piece is measured. From the measured weight A, weight B and weight C, the gel fraction of the pressure-sensitive adhesive sheet 1 is calculated by the formula: gel fraction (% by weight) = (C - B) / (A - B) x 100 (%). .

The haze of the adhesive sheet 1 when the thickness is 15 μm is, for example, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, and further 0.6%. % or less. The lower limit of haze is, for example, 0.1% or more.

The adhesive sheet 1 can be used for optical applications, for example. The pressure-sensitive adhesive sheet 1 may be used for optical laminates and/or image display devices. The pressure-sensitive adhesive sheet 1 is suitable for use in image display devices, such as an image display device with a narrow frame and an image display device with a relatively large screen size, for which suppression of dimensional change in the optical film is particularly required. . By using these in image display devices, for example, peeling of the film included in the optical layered body is suppressed.

[Optical laminate]
An example of the optical laminate of this embodiment is shown in FIG. The optical layered body 10A of FIG. 2 includes an adhesive sheet 1 and an optical film 2. As shown in FIG. The adhesive sheet 1 and the optical film 2 are laminated together. 10 A of optical laminated bodies can be used as an optical film with an adhesive sheet.

Examples of the optical film 2 are polarizing plates, retardation films, and laminated films containing polarizing plates and/or retardation films. However, the optical film 2 is not limited to the above examples. The optical film 2 may contain a film made of glass.

A polarizing plate includes a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any pressure-sensitive adhesive or adhesive can be used for joining the polarizer and the polarizer protective film. The adhesive sheet 1 may be used for bonding. A polarizer is typically a polyvinyl alcohol (PVA) film in which iodine is oriented by stretching such as stretching in air (dry stretching) or stretching in boric acid solution.

A retardation film is a film having birefringence in the in-plane direction and/or the thickness direction. A retardation film is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

The retardation film includes a λ / 4 plate, a λ / 2 plate, an antireflection retardation film (see, for example, paragraphs 0221, 0222, 0228 of JP-A-2012-133303), a viewing angle compensation retardation film (for example, JP-A-2012-133303, paragraphs 0225 and 0226), obliquely oriented retardation film for viewing angle compensation (eg, JP-A-2012-13303, paragraph 0227). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and/or the thickness direction. The retardation value of the retardation film, the arrangement angle, the three-dimensional birefringence, whether it is a single layer or a multilayer, and the like are not limited. A known film can be used as the retardation film.

The thickness of the optical film 2 is, for example, 1-200 μm. The thickness of the optical film 2, which is a polarizing plate, is, for example, 1 to 150 μm, and may be 100 μm or less, 75 μm or less, 50 μm or less, 20 μm or less, or even 15 μm or less. The lower limit of the thickness may be 10 μm or more, 20 μm or more, 50 μm or more, 75 μm or more, or even 100 μm or more.

The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the adhesive sheet 1 may be used for joining the layers.

Another example of the optical laminate of this embodiment is shown in FIG. The optical layered body 10B of FIG. 3 has a layered structure in which a separator 3, an adhesive sheet 1 and an optical film 2 are layered in this order. By peeling off the separator 3, the optical laminate 10B can be used as an optical film with an adhesive sheet.

Separator 3 is typically a resin film. Examples of the resin forming the separator 3 are polyester such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. A peeling treatment may be performed on the surface of the separator 3 that is in contact with the adhesive sheet 1 . The release treatment is, for example, treatment with a silicone compound. However, the separator 3 is not limited to the above example. The separator 3 is peeled off when the optical layered body 10B is used, for example, when attached to the image forming layer.

Another example of the optical laminate of this embodiment is shown in FIG. The optical layered body 10C of FIG. 4 has a laminated structure in which a separator 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4 and a polarizing plate 2B are laminated in this order. After peeling off the separator 3, the optical layered body 10C can be used by attaching it to, for example, an image forming layer.

A known adhesive can be used for the interlayer adhesive 4 . The adhesive sheet 1 may be used as the interlayer adhesive 4 .

Another example of the optical laminate of this embodiment is shown in FIG. The optical layered body 10D of FIG. 5 has a laminated structure in which a separator 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B and a protective film 5 are laminated in this order. After peeling off the separator 3, the optical layered body 10D can be used by attaching it to, for example, an image forming layer.

The protective film 5 has a function of protecting the outermost optical film 2 (polarizing plate 2B) during distribution and storage of the optical layered body 10D and when the optical layered body 10D is incorporated in an image display device. Moreover, it may be the protective film 5 that functions as a window to an external space when incorporated in the image display device. Protective film 5 is typically a resin film. The resin constituting the protective film 5 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, acrylic, cycloolefin, polyimide, and polyamide, preferably polyester. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminated film containing a glass film. The protective film 5 may be subjected to surface treatments such as antiglare, antireflection, and antistatic.

The protective film 5 may be bonded to the optical film 2 with any adhesive. Bonding with the adhesive sheet 1 is also possible.

The optical layered body of this embodiment can be distributed and stored, for example, as a wound body obtained by winding a band-shaped optical layered body, or as a sheet-shaped optical layered body.

The optical laminate of this embodiment is typically used in an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display and an inorganic EL display.

[Image display device]
An example of the image display device of this embodiment is shown in FIG. The image display device 11 in FIG. 6 includes a substrate 7, an image forming layer (for example, an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B and a protective film 5 in this order. It has a laminated structure. The image display device 11 has the optical laminates 10A, 10B, 10C, and 10D shown in FIGS. 2 to 5 (excluding the separator 3). The substrate 7 and the image forming layer 6 may have the same configurations as those of the substrate and the image forming layer provided in a known image display device.

The image display device 11 in FIG. 6 may be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example. The image display device 11 may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), or the like. The image display device 11 may be used for home appliance use, vehicle use, public information display (PID) use, and the like.

The image display device of this embodiment can have any configuration as long as it includes the optical layered body of this embodiment.

EXAMPLES The present invention will be described in more detail below with reference to examples. The invention is not limited to the examples shown below.

First, evaluation methods for the (meth)acrylic polymers and pressure-sensitive adhesive sheets produced in Examples and Comparative Examples are described.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) of the (meth)acrylic polymer was evaluated by GPC under the following conditions.
・ Analyzer: Acquity APC manufactured by Waters
・Column: G7000HXL+GMHXL+GMHXL manufactured by Tosoh
・Column temperature: 40°C
・Eluent: tetrahydrofuran (acid added)
・Flow rate: 0.8 mL/min ・Injection volume: 100 μL
・Detector: Differential refractometer (RI)
・ Standard sample: Polystyrene (PS) manufactured by Agilent

[Distance Ra]
The distance Ra was calculated by the method described above. HSPiP (version 5) was used as software.

[Storage elastic modulus G' (25°C)]
The storage elastic modulus G' (25°C) of the pressure-sensitive adhesive sheet was evaluated by the method described above. However, a sample for measurement was prepared by punching out a laminate obtained by stacking the produced pressure-sensitive adhesive sheets into a disc shape. ARES-G2 manufactured by TA Instruments was used for the dynamic viscoelasticity measurement of the measurement sample.

[Haze]
The haze of the pressure-sensitive adhesive sheet (15 μm thick) was measured in an atmosphere of 25° C. using a haze meter HZ-V3 manufactured by Suga Test Instruments in accordance with JIS K7136:1981. In addition, the measurement was performed in a state in which the pressure-sensitive adhesive sheet (thickness: 15 μm) to be evaluated was laminated on a slide glass S012140 (thickness: 1.3 mm) manufactured by Matsunami Glass Industry.

[Humidification durability]
Humidification durability (corresponding to an accelerated durability test) of the PSA sheet was evaluated by the following method. First, a pressure-sensitive adhesive sheet-attached circularly polarizing plate having the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples on one exposed surface was formed. Next, a circularly polarizing plate was fixed to the surface of a glass plate (Eagle XG manufactured by Corning) via the adhesive sheet. Fixing of the circularly polarizing plate was performed in an atmosphere of 23° C. and 50% RH. Next, after treatment in an autoclave at 50 ° C. and 5 atmospheres (absolute pressure) for 15 minutes, it was left to stand until it cooled to 23 ° C., and after stabilizing the bonding of the circularly polarizing plate to the glass plate, it was heated at 60 ° C. and 95 ° C. It was left for 500 hours in a heated and humidified atmosphere of % RH. After standing, the atmosphere was returned to 23° C. and 50% RH, and the circularly polarizing plate was visually checked for peeling from the glass plate and bubbles between the glass plate and the circularly polarizing plate. Humidification durability was evaluated as follows.
A: No change in appearance such as foaming or peeling is observed.
B: Single peeling or foaming is slightly observed at the edge, but within a practically acceptable range.
C: Slight continuous peeling or foaming is observed at the edge, but within a practically acceptable range.
D: Significant peeling or foaming is observed at the edge, which is problematic in practice.

The method for forming the pressure-sensitive adhesive sheet-attached circularly polarizing plate used for evaluating the durability to humidification is described below.

<Preparation of polarizing plate P1>
(Production of polarizer)
A long polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name “PE3000”, thickness 30 μm) is uniaxially stretched in the longitudinal direction using a roll stretching machine (total stretching ratio 5.9 times) at the same time. , swelling, dyeing, cross-linking, washing and drying were sequentially performed on the resin film to prepare a polarizer having a thickness of 12 μm. In the swelling treatment, the resin film was stretched 2.2 times while being treated with pure water at 20°C. In the dyeing treatment, the resin film was stretched 1.4 times while being treated with an aqueous solution containing iodine and potassium iodide at a weight ratio of 1:7 at 30°C. The iodine concentration in the aqueous solution was adjusted so that the single transmittance of the polarizer to be produced was 45.0%. A two-step process was employed for the cross-linking treatment. In the first-stage cross-linking treatment, the resin film was stretched 1.2 times while being treated with an aqueous solution of boric acid and potassium iodide at 40°C. The content of boric acid in the aqueous solution used for the first-stage cross-linking treatment was 5.0% by weight, and the content of potassium iodide was 3.0% by weight. In the second-stage cross-linking treatment, the resin film was stretched 1.6 times while being treated with an aqueous solution of boric acid and potassium iodide at 65°C. The content of boric acid in the aqueous solution used in the second-stage cross-linking treatment was 4.3% by weight, and the content of potassium iodide was 5.0% by weight. A potassium iodide aqueous solution at 20° C. was used for the cleaning treatment. The content of potassium iodide in the aqueous solution used for the cleaning treatment was 2.6% by weight. The drying treatment was performed under drying conditions of 70° C. and 5 minutes.

(Preparation of polarizing plate P1)
A triacetyl cellulose (TAC) film (manufactured by Konica Minolta, product name “KC2UA”, thickness 25 μm) was attached to each main surface of the polarizer prepared above with a polyvinyl alcohol-based adhesive. However, in the TAC film attached to one main surface, a hard coat (7 μm thick) was formed on the main surface opposite to the polarizer side. Thus, a polarizing plate P1 having a structure of protective layer with hard coat/polarizer/protective layer (no hard coat) was obtained.

<Preparation of retardation film R1>
(Preparation of first retardation film)
Isosorbide (ISB) 26.2 parts by weight, 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF) 100.5 parts by weight, 1,4-cyclohexanedimethanol (1,4-CHDM) 10 .7 parts by weight, 105.1 parts by weight of diphenyl carbonate (DPC), and 0.591 parts by weight of cesium carbonate (0.2% by weight aqueous solution) as a catalyst were charged into a reaction vessel and dissolved under a nitrogen atmosphere ( about 15 minutes). At this time, the temperature of the heat medium in the reaction vessel was set at 150° C., and stirring was carried out as necessary. Next, the pressure inside the reaction vessel was reduced to 13.3 kPa, and the temperature of the heat medium was raised to 190° C. in 1 hour. Phenol generated as the temperature of the heat medium increased was discharged out of the reaction vessel (the same applies hereinafter). Next, after maintaining the temperature in the reaction vessel at 190° C. for 15 minutes, the pressure in the reaction vessel was changed to 6.67 kPa, and the temperature of the heat medium was raised to 230° C. in 15 minutes. When the stirring torque of the stirrer provided in the reaction vessel increased, the temperature of the heat medium was raised to 250° C. in 8 minutes, and the pressure in the reaction vessel was reduced to 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, and the produced reaction product was extruded into water and pelletized. Thus, a polycarbonate resin having a composition of BHEPF/ISB/1,4-CHDM=47.4 mol %/37.1 mol %/15.5 mol % was obtained. The obtained polycarbonate resin had a glass transition temperature of 136.6° C. and a reduced viscosity of 0.395 dL/g.

After vacuum drying the prepared polycarbonate resin pellets at 80 ° C. for 5 hours, a single screw extruder (manufactured by Isuzu Kakoki, screw diameter 25 mm, cylinder set temperature 220 ° C.), T die (width 200 mm, set temperature 220 ° C.), chill roll A long resin film having a thickness of 120 μm was obtained using a film forming apparatus equipped with a set temperature of 120 to 130° C. and a winder. Next, the obtained resin film was stretched in the width direction with a tenter stretching machine at a stretching temperature of 137 to 139° C. and a stretching ratio of 2.5 times to obtain a first retardation film.

(Production of second retardation film)
20 parts by weight of a side chain type liquid crystal polymer (weight average molecular weight 5000) represented by the following chemical formula (I) (where 65 and 35 are mol% of each structural unit), a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF) , trade name “Paliocolor LC242”) 80 parts by weight, and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name “Irgacure 907”) 5 parts by weight are dissolved in 200 parts by weight of cyclopentanone to form a liquid crystal coating liquid. prepared. Next, the surface of a norbornene-based resin film (manufactured by Nippon Zeon, trade name “Zeonex”), which is a base film, is coated with the prepared liquid crystal coating liquid using a bar coater, and then heated at 80 ° C. for 4 minutes. By drying, the liquid crystal contained in the coating film was oriented. Next, the coating film was cured by irradiation with ultraviolet rays to form a liquid crystal solidified layer (thickness: 0.58 μm) as a second retardation film on the substrate film. The in-plane retardation Re of the liquid crystal solidified layer for light with a wavelength of 550 nm is 0 nm, and the thickness direction retardation Rth is -71 nm (nx = 1.5326, ny = 1.5326, nz = 1.6550). The solidified layer exhibited refractive index properties of nz>nx=ny.

(Preparation of retardation film R1)
One surface of the first retardation film prepared above and the liquid crystal solidified layer of the second retardation film were pasted together via an adhesive to prepare a retardation film R1.

<Preparation of circularly polarizing plate with adhesive sheet>
(Production of interlayer adhesive)
79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid and 0.5 parts by weight of 4-hydroxybutyl acrylate were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. A monomer mixture containing 1 part by weight was charged. Next, 0.1 part by weight of 2,2'-azoisobutyronitrile as a polymerization initiator was added to 100 parts by weight of the monomer mixture together with ethyl acetate, and nitrogen gas was introduced while gently stirring. After the inside of the flask was replaced with nitrogen, the polymerization reaction was allowed to proceed for 7 hours while maintaining the liquid temperature in the flask around 55°C. Next, ethyl acetate was added to the resulting reaction solution to adjust the solid content concentration to 30% by weight to obtain a solution of a (meth)acrylic polymer used as an interlaminar pressure-sensitive adhesive. The weight average molecular weight of the obtained polymer was 2,200,000.

Next, in the solution of the obtained (meth)acrylic polymer, trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh, trade name "Coronate L") is added to 100 parts by weight of the solid content of the solution. ) 0.5 parts by weight, 0.1 parts by weight of benzoyl peroxide which is a peroxide cross-linking agent, epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403) 0.2 parts by weight, And a polyether compound having a reactive silyl group (manufactured by Kaneka, Silyl SAT10) 0.5 parts by weight is mixed, and an adhesive composition used as an interlayer adhesive for bonding the polarizing plate P1 and the retardation film R1 The product PSA1 was obtained.

(Preparation of polarizing plate with interlayer pressure-sensitive adhesive layer)
The pressure-sensitive adhesive composition PSA1 prepared above is applied to the release surface of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) having a thickness of 38 μm, which is a release film having a silicone-treated release surface. It was coated so that the thickness of the layer after drying was 12 μm, and dried at 155° C. for 1 minute to form an interlayer pressure-sensitive adhesive layer. Next, the formed interlayer pressure-sensitive adhesive layer was transferred to the protective layer (no hard coat) side of the polarizing plate P1 to obtain a polarizing plate with an interlayer pressure-sensitive adhesive layer.

(Preparation of circularly polarizing plate with adhesive sheet)
On the second retardation film side of the retardation film R1 (the norbornene-based resin film used as the base film when producing the second retardation film is peeled off), each pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was transferred from the release film and pasted. Next, the polarizing plate with an interlayer pressure-sensitive adhesive layer prepared above was attached to the first retardation film side of the retardation film R1 via the interlayer pressure-sensitive adhesive layer to obtain a circularly polarizing plate with an pressure-sensitive adhesive sheet. The attachment of the retardation film R1 and the polarizing plate with an interlayer pressure-sensitive adhesive layer is performed by adjusting the angle formed by the slow axis of the first retardation film and the absorption axis of the polarizer when viewed from the side of the first retardation film. was 45 degrees counterclockwise.

Next, the method for producing each pressure-sensitive adhesive sheet of Examples and Comparative Examples will be described.

The correspondence between the abbreviations or names shown in the following description and the compounds is as follows.
BA: n-butyl acrylate BzA: benzyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate NVP: N-vinylpyrrolidone AIBN: 2,2'-azobisisobutyronitrile C/L: trimethylolpropane/tri Diisocyanate trimer adduct (isocyanate cross-linking agent; manufactured by Tosoh Corporation, Coronate L)
TetradC: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (polyfunctional epoxy-based cross-linking agent; manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrad C)
KBM403: 3-glycidoxypropyltriethoxysilane (silane coupling agent; manufactured by Shin-Etsu Chemical Co., Ltd., KBM403)

[Preparation of (meth)acrylic polymer (A)]
(Synthesis example 1)
94.9 parts by weight of BA, 5.0 parts by weight of AA, and 0.1 part by weight of HBA were charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Next, 0.1 part by weight of AIBN as a polymerization initiator was added to 100 parts by weight of a mixture of BA, AA and HBA, and nitrogen gas was introduced while gently stirring to replace the inside of the flask with nitrogen. The polymerization reaction was allowed to proceed for 7 hours while maintaining the temperature of the liquid in the vicinity of 55°C. Next, ethyl acetate was added to the resulting reaction solution to adjust the solid content concentration to 12% by weight to obtain a solution of (meth)acrylic polymer (A-1). The (meth)acrylic polymer (A-1) had a weight average molecular weight (Mw) of 2,200,000.

(Synthesis example 2)
A (meth)acrylic polymer (meth)acrylic polymer ( A-2) solution was obtained. The (meth)acrylic polymer (A-2) had a weight average molecular weight (Mw) of 2,200,000.

(Synthesis Example 3)
A (meth)acrylic polymer (meth)acrylic polymer ( A-3) solution was obtained. The (meth)acrylic polymer (A-3) had a weight average molecular weight (Mw) of 2,300,000.

(Synthesis Example 4)
(Meth)acrylic polymer (A- A solution of 4) was obtained. The (meth)acrylic polymer (A-4) had a weight average molecular weight (Mw) of 2,500,000.

(Synthesis Example 5)
(Meth)acrylic polymer (A- A solution of 5) was obtained. The (meth)acrylic polymer (A-5) had a weight average molecular weight (Mw) of 2,600,000.

(Synthesis Example 6)
A solution of (meth)acrylic polymer (A-6) was prepared in the same manner as in Synthesis Example 1, except that the monomers used were changed to 89.9 parts by weight of BA, 10.0 parts by weight of AA and 0.1 parts by weight of HBA. got The (meth)acrylic polymer (A-6) had a weight average molecular weight (Mw) of 2,600,000.

The types and charged amounts of the monomers and polymerization initiators used in Synthesis Examples 1 to 6, and the weight average molecular weights (Mw) of the obtained polymers are summarized in Table 1 below.

[Preparation of adhesive composition and adhesive sheet]
(Examples 1 to 7, Comparative Examples 1 to 3)
As shown in Table 2 below, 100 parts by weight of the solid content of the (meth)acrylic polymer (A) was mixed with a crosslinking agent and the like to obtain a solvent-type pressure-sensitive adhesive composition.

Next, after applying the obtained pressure-sensitive adhesive composition to the release surface of a 38 μm thick PET film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38), which is a release film having a silicone-treated release surface. , and dried for 60 seconds in an air circulating constant temperature oven set at 155° C. to form pressure-sensitive adhesive sheets (thickness: 15 μm) of Examples 1-7 and Comparative Examples 1-3. A fountain coater was used to apply the adhesive composition. Evaluation results of each HSP component (δD, δP, δH) and the HSP distance Ra between the two for the self-polymer (C) of the (meth)acrylic polymer (A) and the cross-linking agent (B), and the prepared pressure-sensitive adhesive sheets are shown in Table 3 below. Note that Tetrad-C did not form a self-polymer.

As shown in Table 3, the pressure-sensitive adhesive sheets of Examples in which the amount of the cross-linking agent (B) was 5 parts by weight or more and the distance Ra was 12.3 or less had a larger dimension than the pressure-sensitive adhesive sheets of Comparative Examples. It is suitable for suppressing changes in the temperature and exhibits high durability.

According to the pressure-sensitive adhesive composition of the present invention, for example, a pressure-sensitive adhesive sheet for use in image display devices can be formed.

REFERENCE SIGNS LIST 1 adhesive sheet 2 optical film 10A, 10B, 10C, 10D optical laminate 11 image display device

Claims (11)

(Meth) acrylic polymer (A) as a main component,
further comprising a cross-linking agent (B),
The amount of the cross-linking agent (B) is 5 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A),
Assuming the self-polymer (C) of the cross-linking agent (B), the distance Ra of the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) is 12.3 or less. The pressure-sensitive adhesive composition according to claim 1, wherein the cross-linking agent (B) is isocyanate-based. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the cross-linking agent (B) is tolylene diisocyanate-based. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the cross-linking agent (B) is trifunctional or higher. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth)acrylic polymer (A) contains a structural unit derived from an aromatic ring-containing monomer. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the (meth)acrylic polymer (A) contains 1% by weight or less of structural units derived from a hydroxyl group-containing monomer. . The pressure-sensitive adhesive composition according to any one of claims 1 to 6, which is solvent-based. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 7. The pressure-sensitive adhesive sheet according to claim 8, which has a storage elastic modulus G' at 25°C of 0.5 MPa or more. An optical laminate comprising the adhesive sheet according to claim 8 or 9 and an optical film. An image display device comprising the optical laminate according to claim 10 .

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