TW202248247A - Adhesive composition, adhesive sheet, optical laminate, image display device, and method for producing adhesive sheet - Google Patents

Abstract

An adhesive composition provided herein includes a (meth)acrylic polymer (A) as a main component, and further includes a cross-linking agent (B) having a functional group reactive with a hydroxyl group, and a polyfunctional alcohol (C). The polyfunctional alcohol (C) has a molecular weight of at most 240. An added amount of the polyfunctional alcohol (C) is 0.5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A). The adhesive composition, which comprises a cross-linking agent having a functional group reactive with a hydroxyl group, is suitable for forming an adhesive sheet having excellent durability.

Description

Adhesive composition, adhesive sheet, optical laminate and image display device, and method for producing adhesive sheet

The present invention relates to an adhesive composition, an adhesive sheet, an optical laminate, an image display device, and a method for producing the adhesive sheet.

Various image display devices such as liquid crystal displays and organic EL displays generally have a laminated structure of an image-forming layer such as a liquid crystal layer, an organic EL light-emitting layer, and an optical laminate including an optical film and an adhesive sheet. Adhesive sheets are mainly used to join the films contained in the optical laminate or to join the image forming layer and the optical laminate. Patent Document 1 discloses an example of an optical layered body. prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2008-096734

The problem to be solved by the invention Excessive change in the size of the optical film with temperature changes will cause color unevenness in the image display device. In order to suppress dimensional changes, it is considered to increase the elastic modulus of the adhesive sheet and to blend a crosslinking agent for this purpose. As a crosslinking agent, the crosslinking agent which has a functional group (isocyanate group etc.) reactive with a hydroxyl group can be used, for example. However, according to studies by the present inventors, when the above-mentioned crosslinking agent is blended, it may be observed that the adhesive sheet's ability to follow the dimensional change of the optical film decreases, and the durability of the adhesive sheet decreases.

An object of the present invention is to provide an adhesive composition including a crosslinking agent having a functional group reactive with a hydroxyl group, and the adhesive composition is suitable for forming an adhesive sheet with excellent durability.

means to solve problems The inventors of the present invention studied diligently and found that when the above-mentioned crosslinking agent is mixed, the durability of the adhesive sheet changes with the seasons. Based on this knowledge, the present inventors have succeeded in suppressing the reduction in the durability of the adhesive sheet by adding a polyfunctional alcohol containing multiple hydroxyl groups per molecule and having a relatively small molecular weight to the adhesive composition.

The present invention provides an adhesive composition comprising (meth)acrylic polymer (A) as a main component, and further comprising: a crosslinking agent (B), which has a functional group reactive with a hydroxyl group; and, a polyfunctional alcohol (C); The molecular weight of the aforementioned polyfunctional alcohol (C) is 240 or less; The compounding quantity of the said polyfunctional alcohol (C) is 0.5 weight part or more and 20 weight part or less with respect to 100 weight part of said (meth)acryl-type polymers (A).

In another aspect, the present invention provides an adhesive sheet formed of the above-mentioned adhesive composition of the present invention.

In another aspect, the present invention provides an optical laminate comprising the above-mentioned adhesive sheet of the present invention and an optical film.

In another aspect, the present invention provides an image display device including the above-mentioned optical layered body of the present invention.

In another aspect, the present invention provides a method for manufacturing an adhesive sheet, comprising the following steps: Coating the above-mentioned adhesive composition of the present invention on a substrate to form a coating film; and The aforementioned coating film was dried.

Invention effect According to the adhesive composition of the present invention, it is an acrylic adhesive composition including a crosslinking agent, and the crosslinking agent has a functional group reactive with a hydroxyl group; and the adhesive composition is suitable for forming durability Excellent adhesive film.

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited by the embodiments shown below.

In this specification, "(meth)acrylic acid" means acrylic acid and methacrylic acid. Moreover, "(meth)acrylate" means acrylate and methacrylate.

[Adhesive composition] The adhesive composition (I) of this embodiment includes: a (meth)acrylic polymer (A); a crosslinking agent (B), which has a functional group reactive with a hydroxyl group; and, a polyfunctional alcohol (C ). The (meth)acrylic polymer (A) is contained in the adhesive composition (I) as a main component. In other words, the adhesive composition (I) is an acrylic adhesive composition. The molecular weight of polyfunctional alcohol (C) is 240 or less. We think that by setting the molecular weight to 240 or less, the diffusion ability in the adhesive composition (I) can be improved, and sufficient reactivity with the crosslinking agent (B) can be ensured. In the adhesive composition (I), the blending amount of the polyfunctional alcohol (C) is not less than 0.5 parts by weight and not more than 20 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A). According to the above blending amount, not only can it not only play a role in improving the uniformity of the reaction without being affected by the amount of moisture in the gas environment, but also suppress the precipitation of polyfunctional alcohol (C) in the formed adhesive sheet (typically segregation). Precipitation is also the main cause of the reduction in the durability of the adhesive sheet.

The main component means the component with the largest content in the composition. The content rate of the main component is, for example, 50% by weight or more, may be 60% by weight or more, 70% by weight or more, and may be 75% by weight or more.

[(Meth)acrylic polymer (A)] The (meth)acrylic polymer (A) preferably has, as a main unit, a structural unit derived from a (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. A (meth)acrylic-type polymer (A) may have 1 type, or 2 or more types of structural units derived from a (meth)acrylic-type monomer (A1). Examples of (meth)acrylic monomers (A1) are: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, secondary butyl (meth)acrylate, Tertiary butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, (meth)acrylic acid Isohexyl, 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), (meth)acrylate ) n-tridecyl acrylate and n-tetradecyl (meth)acrylate. In this specification, the "main unit" means, for example, a unit accounting for more than 50% by weight, preferably more than 60% by weight, more preferably more than 70% by weight of the total structural units of the polymer, and more preferably It is preferably a unit accounting for 80% by weight or more.

The (meth)acrylic-type polymer (A) may have the structural unit derived from the (meth)acrylic-type monomer (A1) which has a long-chain alkyl group in a side chain. An example of the monomer (A1) is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). In this specification, "long-chain alkyl" means an alkyl group having 6 to 30 carbon atoms.

When the (meth)acrylic polymer (A) is a homopolymer, it may also have a (meth)acrylic monomer (A1) with a glass transition temperature (Tg) in the range of -70~-20°C constituent unit. An example of the monomer (A1) is 2-ethylhexyl acrylate.

The (meth)acrylic polymer (A) may have structural units other than the structural unit derived from the (meth)acrylic monomer (A1). The constituent unit is derived from a monomer (A2) copolymerizable with a (meth)acrylic monomer (A1). The (meth)acrylic polymer (A) may have 1 type, or 2 or more types of this structural unit.

An example of the monomer (A2) is an aromatic ring-containing monomer. The aromatic ring-containing monomer may also be an aromatic ring-containing (meth)acrylic monomer. Examples of aromatic ring-containing monomers are: phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, oxidized Vinyl modified nonylphenol (meth)acrylate, hydroxyethylated β-naphthol (meth)acrylate and biphenyl (meth)acrylate. The content of the structural unit derived from the aromatic ring-containing monomer in the (meth)acrylic polymer (A) is, for example, 0 to 25% by weight, or 1 to 25% by weight, 5 to 20% by weight, 8 to 25% by weight. 18% by weight, more preferably 10-15% by weight.

The monomer (A2) may also be a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may also 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 hydroxyalkyl (meth)acrylate and (4-hydroxy Methylcyclohexyl)-methacrylate. From the viewpoint of less likely to interfere with the action of the polyfunctional alcohol (C), the content of the structural unit derived from the hydroxyl group-containing monomer in the (meth)acrylic polymer (A) may be 1% by weight or less, or may be 0.5% by weight or less, more preferably 0.1% by weight or less, or 0% by weight (this structural unit may not be included).

The monomer (A2) may also be a carboxyl group-containing monomer, an amine 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 include N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide-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(methyl)acrylamide ) acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(methyl)acrylamide ) acrylamide and mercaptoethyl (meth)acrylamide and other acrylamide-based monomers; N-acryl heterocyclic monomers such as (meth)acrylpyrrolidine; body etc.

Monomer (A2) may also be a polyfunctional monomer. Examples of polyfunctional 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, Neopentyl Glycol Di(meth)acrylate, Neopentyl tetra Alcohol tri(meth)acrylate, Dineopentaerythritol hexa(meth)acrylate, Trimethylolpropane tri(meth)acrylate, Tetramethylolmethane tri(meth)acrylate, (Meth ) polyfunctional acrylates such as allyl acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate and urethane acrylate; and divinylbenzene. The multifunctional acrylate is preferably 1,6-hexanediol diacrylate and dipenteoerythritol hexa(meth)acrylate.

The total content of constituent units derived from carboxyl group-containing monomers, amine group-containing monomers, amide group-containing monomers, and polyfunctional monomers in the (meth)acrylic polymer (A) is preferably 20% by weight or less , more preferably 10% by weight or less, more preferably 8% by weight or less. When the (meth)acryl-type polymer (A) has this structural unit, the total content rate may be 0.01 weight% or more, for example, and may be 0.05 weight% or more. The (meth)acrylic polymer (A) may not contain a structural unit derived from a polyfunctional monomer.

Examples of other monomers (A2) are: 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, (methoxyethyl) Base) 3-methoxypropyl acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate and 4-ethoxybutyl (meth)acrylate, etc. (meth) Alkoxyalkyl acrylate; Epoxy-containing monomers such as (meth)glycidyl acrylate and methylglycidyl (meth)acrylate; sulfonic acid-containing monomers such as sodium vinyl sulfonate; Phosphate-containing monomers; (meth)acrylates with alicyclic hydrocarbon groups such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; vinyl acetate and Vinyl esters such as vinyl propionate; Aromatic vinyl compounds such as styrene and vinyltoluene; Olefins or dienes such as ethylene, propylene, butadiene, isoprene and isobutylene; Vinyl alkyl ethers, etc. vinyl ethers; and vinyl chloride.

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

The (meth)acrylic polymer (A) can be formed by polymerizing the above-mentioned 1 type or 2 or more types of monomers by a well-known method. Monomers can also be polymerized with partial polymers of monomers. Polymerization can be implemented by, for example, solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. Since an adhesive sheet with excellent optical transparency can be formed, solution polymerization and active energy ray polymerization are preferable. Polymerization should be carried out by avoiding contact of monomer and/or part of the polymer with oxygen. Therefore, for example, polymerization in an inert gas environment such as nitrogen, or polymerization in a state where oxygen is blocked by a resin film or the like can be used. The formed (meth)acrylic polymer (A) may be any form of a random copolymer, a block copolymer, a graft copolymer, etc.

The polymerization system forming the (meth)acrylic polymer (A) may contain one or two or more polymerization initiators. The type of polymerization initiator can be selected according to the polymerization reaction, for example, it can also be a thermal polymerization initiator or a photopolymerization initiator.

Solvents used in solution polymerization are, for example: 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; cyclohexane and methylcyclohexane Alicyclic hydrocarbons such as methyl ethyl ketone, methyl isobutyl ketone and other ketones. However, the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

The polymerization initiator used for solution polymerization is an azo type polymerization initiator, a peroxide type polymerization initiator, and a redox type polymerization initiator, for example. Peroxide-based polymerization initiators are, for example, dibenzoyl peroxide and tertiary butyl peroxymaleate. Among them, the azo-based polymerization initiator disclosed in Japanese Patent Application Laid-Open No. 2002-69411 is preferable. The azo-based polymerization initiator is, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2 -dimethylpropionate), 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The usage-amount of an azo type polymerization initiator is 0.05-0.5 weight part with respect to 100 weight part of total monomers, for example, and may be 0.1-0.3 weight part.

The active energy rays used for active energy ray polymerization are, for example, alpha rays, beta rays, gamma rays, neutron rays, ionizing radiation rays such as electron beams, and ultraviolet rays. The active energy rays are preferably ultraviolet rays. Polymerization by ultraviolet irradiation is also called photopolymerization. The polymerization system of active energy ray polymerization typically includes a photopolymerization initiator. The polymerization conditions of the active energy polymerization are not limited as long as the (meth)acrylic polymer (A) can be formed.

系光聚合引發劑。惟，光聚合引發劑不受上述例所限。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, photoactive oxime Photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, 9-oxosulfur

Department of photopolymerization initiator. However, the photopolymerization initiator is not limited to the above examples.

系光聚合引發劑例如為：9-氧硫𠮿

、2-氯9-氧硫𠮿

、2-甲基9-氧硫𠮿

、2,4-二甲基9-氧硫𠮿

、異丙基9-氧硫𠮿

、2,4-二異丙基9-氧硫𠮿

、十二烷基9-氧硫𠮿

。Benzoin ether-based photopolymerization initiators are, for example: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy Base-1,2-diphenylethan-1-one, anisole methyl ether. Acetophenone-based photopolymerization initiators are, for example: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4 -Phenoxydichloroacetophenone, 4-(tertiary butyl)dichloroacetophenone. The α-ketol-based photopolymerization initiators include, for example, 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)benzene]-2-methylpropan-1-one. The aromatic sulfonyl chloride photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. The photoactive oxime-based photopolymerization initiator is, for example, 1-benzene-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. The benzoin-based photopolymerization initiator is, for example, benzoin. The benzyl group photopolymerization initiator is, for example, benzyl group. Benzophenone-based photopolymerization initiators are, for example, diphenyl ketone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxydiphenyl ketone, polyvinyl diphenyl ketone, α - Hydroxycyclohexyl phenyl ketone. The ketal photopolymerization initiator is, for example, benzyl dimethyl ketal. 9-oxosulfur

A photopolymerization initiator such as: 9-oxosulfur 𠮿

, 2-Chloro9-oxosulfur 𠮿

, 2-methyl 9-oxosulfur 𠮿

, 2,4-Dimethyl 9-oxosulfur 𠮿

, Isopropyl 9-oxosulfur

, 2,4-Diisopropyl 9-oxosulfur 𠮿

, dodecyl 9-oxosulfur 𠮿

.

The usage-amount of a photoinitiator is 0.01-1 weight part with respect to 100 weight part of total monomers, for example, and may be 0.05-0.5 weight part.

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is, for example, 1 million to 2.5 million, and from the viewpoint of durability and heat resistance of the adhesive sheet, it may be 1.2 million or more, and may be More than 1.4 million. The weight average molecular weight (Mw) of the polymer and oligomer in this specification is the value (polystyrene conversion) measured by GPC (gel permeation chromatography; Gel Permeation Chromatography).

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

[Crosslinking agent (B)] The crosslinking agent (B) has a functional group reactive with a hydroxyl group. The functional groups are typically isocyanate groups. The isocyanate group has excellent reactivity with the polyfunctional alcohol (C), and is especially suitable for improving the uniformity of the reaction.

Examples of cross-linking agents (B) having isocyanate groups include: toluene diisocyanate, chlorophenylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and aromatic polymethylene polyphenylisocyanate. Isocyanate compounds; alicyclic isocyanate compounds such as cyclopentyl diisocyanate, cyclohexylene diisocyanate, hydrogenated diphenylmethane diisocyanate and isophorone diisocyanate; and butylene diisocyanate, tetramethylene diisocyanate and aliphatic isocyanate compounds such as hexamethylene diisocyanate. The crosslinking agent (B) may also be: a compound (adduct) obtained by adding the above-mentioned isocyanate compound to a polyol compound such as trimethylolpropane; Compounds obtained by addition reaction of polyols such as acrylic polyols, polybutadiene polyols, and polyisoprene polyols; and derivatives of the above-mentioned isocyanate compounds such as isocyanurates. Specific examples of derivatives include trimethylolpropane/cresyl diisocyanate trimer adducts (such as CORONATE L manufactured by Nippon Polyurethane Industry), trimethylolpropane/hexamethylene diisocyanate trimer adducts (for example, CORONATE HL manufactured by Nippon Polyurethane Industry), trimer isocyanate body of hexamethylene diisocyanate (for example, CORONATE HX manufactured by Nippon Polyurethane Industry). From the viewpoint of more reliably suppressing the reduction in the durability of the adhesive sheet, the crosslinking agent (B) is preferably an aromatic isocyanate compound and its derivatives, more preferably cresyl diisocyanate and its derivatives, in other words, diisocyanate and its derivatives. Cresyl isocyanate (TDI) crosslinking agent.

The crosslinking agent (B) may be bifunctional or more polyfunctional, or may be trifunctional or more. In this case, especially when the polyfunctional alcohol (C) is trifunctional or more, the uniformity of the crosslinked structure constructed by reaction with a polyfunctional alcohol (C) can be improved more. An example of the 3-functional crosslinking agent (B) is: a trimer adduct of the above-mentioned isocyanate compound added to trimethylolpropane, preferably a trimer of diisocyanate toluene added to trimethylolpropane adducts.

In the adhesive composition (I), the blending amount of the crosslinking agent (B) is, for example, not less than 0.5 parts by weight and not more than 30 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A). 1 to 28 parts by weight, 5 to 25 parts by weight, 8 to 20 parts by weight, 10 to 18 parts by weight, more than 10 to 15 parts by weight Below, it can be more than 10 weight part and 13 weight part or less. When the blending amount is within the above range, the reduction in the durability of the adhesive sheet can be more reliably suppressed. In addition, in the adhesive composition (I), even if the blending amount of the crosslinking agent (B) is increased in order to further increase the elastic modulus of the adhesive sheet 1 (for example, 8 parts by weight or more, it may be 10 parts by weight or more , more than 10 parts by weight), can still suppress the durability of the adhesive sheet from decreasing.

The adhesive composition (I) may further contain other crosslinking agents. Examples of other crosslinking agents include peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelate compounds. When the adhesive composition (I) contains other crosslinking agents, the blending amount is, for example, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight relative to 100 parts by weight of the (meth)acrylic polymer (A). parts, 0.1 to 2 parts by weight, more preferably 0.1 to 1 parts by weight. The adhesive composition (I) may not contain other crosslinking agents.

[Polyfunctional Alcohol (C)] The molecular weight of polyfunctional alcohol (C) is 240 or less. The molecular weight may be 230 or less, 220 or less, 210 or less, 200 or less, 190 or less, 180 or less, 170 or less, 160 or less, and may be 150 or less. The lower limit of the molecular weight is, for example, 60 or more, may be 80 or more, 90 or more, and may be 100 or more.

Examples of polyfunctional alcohols (C) are: alkylene glycols such as ethylene glycol and propylene glycol and polymers thereof; glycol ethers such as diethylene glycol and polymers thereof; trimethylolethane; trimethylolpropane ; and sugar alcohols such as neopentylitol and sorbitol. The polyfunctional alcohol (C) is preferably trimethylolpropane, diethylene glycol or a polymer thereof, more preferably trimethylolpropane, from the viewpoint of more reliably suppressing the durability of the adhesive sheet.

A polyfunctional alcohol (C) may be trifunctional or more. The polyfunctional alcohol (C) with more than 3 functions is especially suitable for improving the uniformity of the crosslinked structure constructed by reacting with the crosslinking agent (B). An example of a trifunctional polyfunctional alcohol (C) is trimethylolpropane.

The polyfunctional alcohol (C) may not have a reactive group reactive with the crosslinking agent (B) other than the hydroxyl group. The reactive group is, for example, at least one selected from an amine group, a carboxyl group, and an epoxy group, especially an amine group.

In the adhesive composition (I), the blending amount of the polyfunctional alcohol (C) is not less than 0.5 parts by weight and not more than 20 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A). The upper limit of the compounding amount may be 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, and may be 3 parts by weight or less.

The equivalent ratio ([crosslinking agent]/[OH]) of the functional group of the crosslinking agent (B) to the hydroxyl group of the polyfunctional alcohol (C) is, for example, 1 to 5, or 1 to 4 or less, 1 or more and 3 or less, more preferably 1 or more and 2 or less.

[(Meth)acrylic oligomer] The adhesive composition (I) may further include a (meth)acrylic oligomer (D).

The (meth)acrylic oligomer (D) may have the same composition as the (meth)acrylic polymer (A) above except that the weight average molecular weight (Mw) differs. The weight average molecular weight (Mw) of a (meth)acryl-type oligomer (D) is 1000 or more, for example, 2000 or more, 3000 or more, and 4000 or more. The upper limit of the weight average molecular weight (Mw) of a (meth)acrylic oligomer is 30000 or less, for example, 15000 or less, 10000 or less, and 7000 or less.

The (meth)acrylic oligomer (D) has, for example, one or more constituent units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylate Propyl acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, Amyl (meth)acrylate, Isoamyl (meth)acrylate, Hexyl (meth)acrylate, 2-Ethylhexyl (meth)acrylate, Heptyl (meth)acrylate, (Meth)acrylic acid Octyl, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, (meth) Alkyl (meth)acrylates such as undecyl acrylate and dodecyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate Esters of (meth)acrylic acid and alicyclic alcohols such as esters; (meth)acrylates containing aromatic rings such as phenyl (meth)acrylate and benzyl (meth)acrylate; and alcohols derived from terpene compounds The resulting (meth)acrylate.

The (meth)acrylic oligomer (D) preferably has a structural unit derived from a (meth)acrylic monomer having a bulky structure. In this case, the adhesion of the adhesive sheet can be further improved. Examples of the acrylic monomers are: (meth)acrylic acid alkyl esters with branched alkyl groups such as isobutyl (meth)acrylate and tertiary butyl (meth)acrylate; Esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl acrylate, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate; phenyl (meth)acrylate and (meth)acrylic acid Aromatic ring-containing (meth)acrylate such as benzyl ester. The monomer preferably has a cyclic structure, and preferably has two or more cyclic structures. In addition, when the (meth)acrylic oligomer (D) is polymerized and/or when ultraviolet radiation is irradiated when the adhesive sheet is formed, the above-mentioned monomer is less likely to inhibit the progress of polymerization and/or formation. It is preferable not to have an unsaturated bond, for example, an alkyl (meth)acrylate having an alkyl group with a branched chain structure, an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

Specific examples of (meth)acrylic oligomers (D) are: copolymers of butyl acrylate, methyl acrylate and acrylic acid, copolymers of cyclohexyl methacrylate and isobutyl methacrylate, methacrylic acid Copolymer of cyclohexyl methacrylate and isobornyl methacrylate, copolymer of cyclohexyl methacrylate and acrylmorphin, copolymer of cyclohexyl methacrylate and diethylacrylamide, 1-acrylic acid Copolymer of adamantyl ester and methyl methacrylate, copolymer of dicyclopentyl methacrylate and isobornyl methacrylate, selected from dicyclopentyl methacrylate, cyclohexyl methacrylate, methyl Copolymer of isocamyl acrylate, isocamyl acrylate, and cyclopentyl methacrylate with methyl methacrylate, homopolymer of dicyclopentyl acrylate, 1-adamantyl methacrylate Homopolymer of ester and homopolymer of 1-adamantyl acrylate.

The polymerization method of the above-mentioned (meth)acrylic-type polymer (A) can be used for the polymerization of a (meth)acrylic-type oligomer (D).

When the adhesive composition (I) contains the (meth)acrylic oligomer (D), its compounding amount 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 weight part or less, and may be 40 weight part or less. The lower limit of the compounding quantity is 1 weight part or more with respect to 100 weight part of (meth)acryl-type polymers (A), For example, 2 weight part or more may be sufficient as 3 weight part or more. The adhesive composition (I) may not contain the (meth)acrylic oligomer (D).

[additive] The adhesive composition (I) may also contain other additives. Examples of additives are: silane coupling agents, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, Ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts of ionic compounds, ionic liquids, ionic solids, etc.), inorganic fillers, organic fillers, powders, particles, and foils such as metal powders.

When the adhesive composition (I) contains a silane coupling agent, its compounding amount is, for example, 5 parts by weight or less, or 3 parts by weight or less, 1 It may be less than or equal to 0.5 part by weight, or less than 0.1 part by weight. The adhesive composition (I) may also not contain a silane coupling agent.

The type of the adhesive composition (I) is, for example, latex type, solvent type (solution type), active energy ray (photocurable type), heat-melt type (hot-melt type), and the like. From the viewpoint of being able to form an adhesive sheet excellent in durability, the adhesive composition (I) may be a solvent type. The solvent-based adhesive composition (I) may not contain photocuring agents such as ultraviolet curing agents.

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

Regarding the solvent type, for example, the adhesive composition (I) or a mixture of the adhesive composition (I) and a solvent can be coated on a substrate film, and the formed coating film can be dried to form the adhesive sheet 1 . The adhesive composition (I) is thermally cured by heat during drying. For the active energy ray curing type, for example, the following mixture, which becomes the (meth)acrylic polymer (A) by polymerization, is coated on the base film and irradiated with active energy rays to form the adhesive sheet 1 Monomer (group), crosslinking agent (B) and polyfunctional alcohol (C), and optional monomer (group) of partial polymer, polymerization initiator, oligomer (D), other crosslinking Mixtures of agents, additives and solvents, etc. Before irradiating active energy rays, the solvent may also be removed by drying. The base film may also be a film (peeling film) whose coated surface has undergone release treatment.

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

A known method can be used for coating on a base film. Coating can be performed by, for example, roll coating, touch roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, rod coating, knife coat, air knife coating Cloth, curtain coating, lip coating, extrusion coating using a die coater, etc. are performed.

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

Compositions and mixtures applied to substrate films preferably have a viscosity suitable for handling and coating. Therefore, regarding the active energy ray curing type, the coating mixture preferably contains a partial polymer of the monomer (group).

As an example of a peeling film, the coated surface is peeled off with polysiloxane.

The thickness of the adhesive sheet 1 is, for example, 1-200 µm, 5-150 µm, or 10-100 µm.

The storage elastic modulus G'(25°C) of the adhesive sheet 1 may be 0.5 MPa or more, 0.7 MPa or more, 0.9 MPa or more, and may be 1.0 MPa or more. According to the adhesive sheet 1 having a high elastic coefficient with a storage elastic modulus G' within the above-mentioned range, it is possible to more reliably suppress the change in the size of the optical laminate due to temperature.

The storage elastic modulus (25° C.) of the adhesive sheet 1 can be evaluated by the following method. First, a measurement sample made of the material constituting the adhesive sheet 1 is prepared. The shape of the sample for measurement is disc-shaped. The diameter of the bottom surface of the sample for measurement is 8 mm, and the thickness is 1 mm. The sample for measurement may be a laminate obtained by laminating a plurality of adhesive sheets 1 and punched out into a disc shape. Next, dynamic viscoelasticity measurement was performed on the sample for measurement. For dynamic viscoelasticity measurement, for example, ARES-G2 manufactured by TA Instruments can be used. The storage elastic modulus G' of the adhesive sheet 1 at 25°C can be determined from the results of the dynamic viscoelasticity measurement. In addition, the conditions of dynamic viscoelasticity measurement are as follows. ・Measurement conditions Frequency: 1Hz Deformation Mode: Twist Measuring temperature: -70℃~150℃ Heating rate: 5°C/min

The gel fraction of the adhesive sheet 1 is, for example, 60% or more, may be 65% or more, and may be 70% or more. The upper limit of the gel fraction is, for example, 95% or less, and may be 90% or less. A gel fraction within the above range contributes to suppressing the reduction in durability of the adhesive sheet 1 . The gel fraction of the adhesive sheet 1 can be evaluated by the following method. First, about 0.2 g was scraped off from the adhesive sheet 1 to obtain small pieces. Next, the obtained small pieces were covered with stretched porous polytetrafluoroethylene membranes (NTF1122 manufactured by Nitto Denko, with an average pore diameter of 0.2 µm) and bound with kite strings to prepare test pieces. Next, the weight A of the obtained test piece was measured. Weight A is the total weight of small pieces of adhesive sheet, extended porous film and kite string. The total weight B of the extended porous membrane and the kite string used is measured in advance. Next, the test piece was dipped in a container with an inner volume of 50 mL filled with ethyl acetate, and left to stand at 23° C. for one week. After standing still, the test piece was taken out from the container and dried for 2 hours in a dryer set at 130° C., and then the weight C of the test piece was measured. From the measured weight A, weight B, and weight C, the gel fraction of the adhesive sheet 1 was calculated by gel fraction (weight %)=(C-B)/(A-B)×100(%).

The weight average molecular weight (Mw) of the sol part in the adhesive sheet 1 is, for example, 50,000 or more, may be 80,000 or more, 100,000 or more, 150,000 or more, and may be 200,000 or more. The upper limit of the weight average molecular weight (Mw) of a sol part is 1.2 million or less, for example. The weight average molecular weight (Mw) of the sol part within the above-mentioned range contributes to suppressing the reduction in durability of the adhesive sheet 1 .

The adhesive sheet 1 can be used for optical applications, for example. The adhesive sheet 1 can also be used for an optical laminate.

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

Examples of the optical film 2 are a polarizing plate, a retardation film, and a laminated film including a polarizing plate and/or a retardation film. However, the optical film 2 is not limited to the above examples. The optical film 2 may also include a glass film.

The polarizing plate includes polarizers. A polarizer protective film may also be bonded to at least one side of the polarizer. When bonding the polarizer and the polarizer protective film, any adhesive or adhesive can be used. The adhesive sheet 1 can also be used for bonding. The polarizer is typically a polyvinyl alcohol (PVA) film with iodine oriented by stretching in the air (dry stretching), boric acid underwater stretching, etc.

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

The retardation film can also be a λ/4 plate, a λ/2 plate, a retardation film for anti-reflection (for example, refer to paragraphs 0221, 0222, and 0228 of Japanese Patent Application Laid-Open No. 2012-133303), a retardation film for viewing angle compensation ( For example, refer to paragraphs 0225 and 0226 of Japanese Patent Application Laid-Open No. 2012-133303), and oblique orientation retardation film for viewing angle compensation (for example, refer to paragraph 0227 of Japanese Patent Application Laid-Open No. 2012-13303). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and/or in the thickness direction. There are also no restrictions on the retardation value, arrangement angle, 3-dimensional birefringence, single layer or multilayer of the retardation film. As the retardation film, known films can be used.

The thickness of the optical film 2 is, for example, 1-200 μm. The thickness of the optical film 2 used as a polarizer is, for example, 1-50 µm, or less than 20 µm, or even less than 10 µm.

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 can also be used for joining the layers.

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

The release liner 3 is typically a resin film. Examples of the resin constituting the release liner 3 are polyester such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyamide imine. The surface of the release liner 3 that is in contact with the adhesive sheet 1 can also be peeled off. The peeling treatment is, for example, treatment by polysiloxane. However, the release liner 3 is not limited to the above examples. When using the optical layered body 10B, the release liner 3 will be peeled, for example, when sticking to an image forming layer.

Another example of the optical layered body of this embodiment is shown in FIG. 4 . The optical laminate 10C in FIG. 4 has the following laminate structure: a release liner 3 , an adhesive sheet 1 , a retardation film 2A, an interlayer adhesive 4 and a polarizing plate 2B are laminated in sequence. The optical layered body 10C can be used after peeling off the release liner 3, for example, by sticking to an image forming layer.

A well-known adhesive can be used for the interlayer adhesive 4. The adhesive sheet 1 can also be used for the interlayer adhesive 4 .

Another example of the optical layered body of this embodiment is shown in FIG. 5 . The optical laminate 10D in FIG. 5 has the following laminate structure: a release liner 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 sequence. The optical layered body 10D can be used after peeling off the release liner 3, for example, by sticking to the image forming layer.

The protective film 5 has the 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 into an image display device. In addition, in a state where an image display device is incorporated, the protective film 5 functioning as a window to the external space may also be used. The 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 including a glass film. Surface treatments such as anti-glare, anti-reflection, and anti-static can also be applied to the protective film 5 .

The protective film 5 can also be bonded to the optical film 2 by any adhesive. It can also be joined by the adhesive sheet 1 .

The optical layered body of the present embodiment can be distributed and stored in the form of, for example, a tape-shaped optical layered body wound into a roll, or a single-sheet-shaped optical layered body.

Typically, the optical layered body of this embodiment can be used for an image display device. The image display device is, for example, a liquid crystal display or an organic EL display.

[image display device] An example of the image display device of this embodiment is shown in FIG. 6 . The image display device 11 of FIG. 6 has the following laminated structure: a substrate 7, an image forming layer (such as an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, and a polarizing plate are laminated in sequence. 2B and protective film 5. The image display device 11 has the optical laminates 10A, 10B, 10C, and 10D shown in FIGS. 2 to 5 (except for the release liner 3 ). The substrate 7 and the image forming layer 6 may each have the same configuration as the substrate and image forming layer of a known image display device.

The image display device 11 in FIG. 6 can 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 can also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display) and the like. The image display device 11 can also be used in home appliances, in-vehicle applications, public information display (PID) applications, and the like.

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

Example Hereinafter, the present invention will be described in more detail using examples. The present invention is not limited by the Examples shown below.

First, evaluation methods of (meth)acrylic polymers and adhesive sheets produced in Examples and Comparative Examples will be shown.

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

[the humidification durability] The humidity durability of the adhesive sheet (corresponding to the accelerated test of durability) was evaluated by the following method. First, an adhesive sheet-attached circular polarizing plate was formed, which was equipped with each of the adhesive sheets produced in Examples and Comparative Examples on one exposed surface. Next, a circular polarizing plate was fixed on the surface of a glass plate (made by Corning, Eagle XG) through the above-mentioned adhesive sheet. The fixation of the circular polarizer is carried out in an air environment of 23°C and 50% RH. Then, after 15 minutes in an autoclave at 50°C and 5 atmospheres (absolute pressure), let it cool down to 23°C to stabilize the circular polarizing plate and the glass plate, then heat and humidify the gas at 60°C and 95% RH Placed in the environment for 500 hours. After standing, return to the gas environment of 23°C and 50%RH, check with the naked eye whether the circular polarizing plate is peeled off from the glass plate or whether there is foaming between the glass plate and the circular polarizing plate, and evaluate the humidity durability as follows. A: No change in appearance such as foaming or peeling was observed. B: Slight peeling or foaming was observed at the edge, but practically within the range of no problem. C: Peeling or foaming was observed at the edge, and there was also a practical problem. D: Significant peeling was observed at the edge, and there was a practical problem.

A method of forming a circular polarizing plate with an adhesive sheet for evaluation of humidity durability is shown below.

＜Production of polarizing plate P1＞ (production of polarizer) A long strip of polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name "PE3000", thickness 30µm) was uniaxially stretched in the longitudinal direction with a roll stretcher (total stretch ratio: 5.9 times), and the above resin Swelling, dyeing, cross-linking, washing and drying are performed on the film sequentially to produce a polarizer with a thickness of 12µm. In the swelling treatment, the above-mentioned resin film was stretched 2.2 times while being treated with pure water at 20°C. In the dyeing process, the above-mentioned resin film was stretched 1.4 times while being treated with a 30° C. aqueous solution containing iodine and potassium iodide at a weight ratio of 1:7. The concentration of iodine in the aqueous solution was adjusted so that the single transmittance of the manufactured polarizer could be 45.0%. The cross-linking treatment system adopts 2-stage treatment. In the first stage of cross-linking treatment, the above-mentioned resin film was stretched 1.2 times while treating with a 40° C. aqueous solution in which boric acid and potassium iodide were dissolved. In the aqueous solution used for the first-stage crosslinking treatment, the content of boric acid was 5.0% by weight, and the content of potassium iodide was 3.0% by weight. In the second stage of cross-linking treatment, the above-mentioned resin film was stretched 1.6 times while treating with a 65° C. aqueous solution in which boric acid and potassium iodide were dissolved. In the aqueous solution used for the second-stage crosslinking treatment, the content of boric acid was 4.3% by weight, and the content of potassium iodide was 5.0% by weight. A potassium iodide aqueous solution at 20°C is used for cleaning. In the aqueous solution used for the cleaning treatment, the content of potassium iodide was 2.6% by weight. The drying treatment is carried out under the drying conditions of 70° C. and 5 minutes.

(Production of Polarizer 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 through a polyvinyl alcohol-based adhesive. However, for the TAC film bonded to one main surface, a hard coat layer (thickness 7 µm) was formed on the main surface opposite to the polarizer side. In the above-mentioned manner, the polarizing plate P1 having the composition of protective layer with hard coat/polarizer/protective layer (no hard coat) was obtained.

＜Production of Retardation Film R1＞ (Production of the first retardation film) 26.2 parts by weight of isosorbide (ISB), 100.5 parts by weight of 9,9-[4-(2-hydroxyethoxy)phenyl] fennel (BHEPF), 1,4-cyclohexanedimethanol (1,4 -CHDM) 10.7 parts by weight, diphenyl carbonate (DPC) 105.1 parts by weight, and cesium carbonate (0.2% by weight aqueous solution) as a catalyst 0.591 parts by weight were put into the reaction vessel and dissolved under nitrogen atmosphere (about 15 minutes) . At this time, the temperature of the heat medium in the reaction container was set to 150° C., and stirring was performed as necessary. Next, the pressure in the reaction container was reduced to 13.3 kPa, and the temperature of the heat medium was raised to 190° C. within 1 hour. Phenol generated as the temperature of the heat medium rises is discharged to the outside of the reaction container (the same applies hereinafter). Next, after maintaining the temperature in the reaction container at 190° C. for 15 minutes, the pressure in the reaction container was changed to 6.67 kPa, and the temperature of the heat medium was raised to 230° C. within 15 minutes. When the stirring torque of the stirrer equipped in the reaction vessel was increased, the temperature of the heat medium was raised to 250° C. within 8 minutes, and the pressure in the reaction vessel was further reduced to 0.200 kPa or less. After the predetermined stirring torque is reached, the reaction is ended, and the generated reactant is extruded into water to pelletize it. In the above manner, a polycarbonate resin having a composition of BHEPF/ISB/1,4-CHDM=47.4 mol %/37.1 mol %/15.5 mol % was obtained. The glass transition temperature of the obtained polycarbonate resin was 136.6° C., and the reduced viscosity was 0.395 dL/g.

The prepared polycarbonate resin pellets were vacuum-dried at 80° C. for 5 hours. After that, a single-screw extruder (manufactured by Isuzu Chemical Industries Co., Ltd., screw diameter 25 mm, cylinder set temperature 220 ℃), T-die (width 200mm, set temperature 220°C), cooling roll (set temperature 120~130°C) and film-making device of coiler to obtain a long strip of resin film with a thickness of 120µm. Next, the obtained resin film was stretched in the width direction at a stretching temperature of 137-139° C. and a stretching ratio of 2.5 times using a tenter stretcher to obtain a first retardation film.

(Production of the second retardation film) 20 parts by weight of the side chain type liquid crystal polymer (weight average molecular weight 5000) shown in the following chemical formula (I) (wherein, 65 and 35 are the mole % of each constituent unit) shows the polymerization of the nematic liquid crystal phase Liquid crystal (manufactured by BASF, trade name "PaliocolorLC242") 80 parts by weight and photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name "IRGACURE 907") 5 parts by weight were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal Coating solution. Next, the prepared liquid crystal coating solution was applied to the surface of a northylene-based resin film (manufactured by ZEON Japan, trade name "ZEONEX") of the substrate film using a bar coater, and then heated and dried at 80°C for 4 Minutes to align the liquid crystal contained in the coating film. Next, the coating film was cured by ultraviolet irradiation, and a liquid crystal solidified layer (thickness: 0.58 µm) was formed as a second retardation film on the base film. The in-plane retardation Re of the liquid crystal solidified layer to light with a wavelength of 550nm is 0nm, and the retardation Rth in the thickness direction is -71nm (nx=1.5326, ny=1.5326, nz=1.6550), and the liquid crystal solidified layer exhibits nz>nx=ny the refractive index properties.

[chemical formula 1]

(Manufacturing of Retardation Film R1) The retardation film R1 was produced by bonding one side of the above-produced first retardation film and the liquid crystal solidified layer of the second retardation film through an adhesive.

＜Production of circular polarizing plate with adhesive sheet＞ (Production of interlayer adhesive) In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler, feed 79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid and 0.1 part by weight of 4-hydroxybutyl acrylate monomer mixture. Next, with respect to 100 parts by weight of the monomer mixture, 0.1 part by weight of 2,2'-azoisobutyronitrile and ethyl acetate were added together as a polymerization initiator, and nitrogen gas was introduced into the flask while stirring slowly to replace nitrogen in the flask. , The liquid temperature in the flask was kept at around 55° C. and the polymerization reaction was carried out for 7 hours. Next, ethyl acetate was added to the obtained reaction liquid to adjust to a solid content concentration of 30% by weight, thereby obtaining a solution of a (meth)acrylic polymer used as an interlayer adhesive. The weight average molecular weight of the obtained polymer was 2.2 million.

Next, in the obtained (meth)acrylic polymer solution, a trimethylolpropane/cresyl diisocyanate trimer adduct (manufactured by Tosoh, 0.5 part by weight of product name "CORONATE L", 0.1 part by weight of benzoyl peroxide as a peroxide crosslinking agent, silane coupling agent containing epoxy group (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") ) 0.2 parts by weight and 0.5 parts by weight of a polyether compound having a reactive silicon group (manufactured by Kaneka, Silyl SAT10) to obtain an adhesive composition PSA1 for bonding the interlayer adhesive of the polarizing plate P1 and the retardation film R1 .

(Manufacture of polarizing plate with interlayer adhesive layer) Apply the above-prepared adhesive composition PSA1 on a release film treated with silicone on the peeling surface, that is, on a polyethylene terephthalate (PET) film with a thickness of 38 µm (manufactured by Mitsubishi Polyester Film, MRF38) so that the layer thickness after drying will be 12µm, and dry at 155°C for 1 minute to form an interlayer adhesive layer. Next, the formed interlayer adhesive layer was transferred to the protective layer (no hard coat layer) side of the polarizing plate P1 to obtain a polarizing plate with an interlayer adhesive layer.

(Production of circular polarizing plate with adhesive sheet) Each of the adhesive sheets produced in Examples and Comparative Examples was transferred from the release film and attached to the second retardation film side of the retardation film R1 (when making the second retardation film, the film used as the substrate film will be Vinyl resin film peeling off). Next, the above-prepared polarizer with an interlayer adhesive layer was attached to the first retardation film side of the retardation film R1 through the interlayer adhesive layer to obtain a circular polarizer with an adhesive sheet. The attachment of the retardation film R1 and the polarizing plate with the interlayer adhesive layer is based on the counterclockwise direction of 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 It is implemented in a 45-degree manner.

[Storage elastic modulus G'(25℃)] The evaluation of the storage elastic modulus G' of the adhesive sheet at 25°C was carried out by the above-mentioned method. The dynamic viscoelasticity measurement was performed using ARES-G2 manufactured by TA Instruments.

Next, the manufacturing method of each adhesive sheet of an Example and a comparative example is demonstrated.

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 HBA: 4-Hydroxybutyl Acrylate HEA: 2-Hydroxyethyl Acrylate AIBN: 2,2'-Azobisisobutyronitrile C/L: Trimethylolpropane/cresyl diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry, CORONATE L) TMP: Trimethylolpropane PP200: polyoxypropylene glycol (manufactured by Sanyo Chemical Industry, SANNIX PP200) GP250: polyoxypropylene triol (manufactured by Sanyo Chemical Industry, SANNIX GP250) GP400: polyoxypropylene triol (manufactured by Sanyo Chemical Industry, SANNIX GP400) GP1000: polyoxypropylene triol (manufactured by Sanyo Chemical Industry, SANNIX GP1000) Placcel 303: polycaprolactone triol (manufactured by Daicel, Placcel 303) PEG300: polyethylene glycol (molecular weight 300)

The molecular weight, the number of hydroxyl groups per molecule and the hydroxyl value of the polyfunctional alcohols used are shown in Table 1 below.

[Table 1]

[Production of (meth)acrylic polymer (A)] (Synthesis Example 1) 81.9 parts by weight of BA, 13.2 parts by weight of BzA, 4.8 parts by weight of AA, and 0.1 parts by weight of HBA were fed into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction pipe, and a cooler. Next, 0.1 part by weight of AIBN was added as a polymerization initiator to 100 parts by weight of the mixture of BA, BzA, AA, and HBA, and nitrogen gas was introduced while stirring slowly to replace nitrogen in the flask, and the liquid temperature in the flask was maintained at 55 The polymerization reaction was carried out at around ℃ for 7 hours. Next, ethyl acetate was added to the obtained reaction liquid, and the solution of the (meth)acrylic-type polymer (A-1) was obtained by adjusting to solid content concentration 12 weight%. The weight average molecular weight (Mw) of (meth)acryl-type polymer (A-1) was 2.2 million.

(Synthesis Example 2) A solution of (meth)acrylic polymer (A-2) was obtained in the same manner as in Synthesis Example 1 except that the monomers used were changed to 77.0 parts by weight of BA, 20.0 parts by weight of BzA, and 3.0 parts by weight of AA. The weight average molecular weight (Mw) of a (meth)acrylic-type polymer (A-2) was 2.2 million.

(Synthesis Example 3) Except having changed the monomer used into 85.0 weight part of BA, 15.0 weight part of AA, and 15 weight part of HEA, it carried out similarly to the synthesis example 1, and obtained the solution of (meth)acrylic-type polymer (A-3). The weight average molecular weight (Mw) of a (meth)acrylic-type polymer (A-3) was 2.2 million.

The types and feeding amounts of the monomers and polymerization initiators used in Synthesis Examples 1 to 3, and the weight average molecular weight (Mw) of the obtained polymers are summarized in Table 2 below.

[Table 2]

[Production of adhesive composition and adhesive sheet] (Examples 1 to 4, Comparative Examples 1 to 6, Reference Examples 1 and 2) The (meth)acrylic polymer (A), the crosslinking agent (B), and the polyfunctional alcohol were mixed so as to have the composition shown in Table 3 below, to obtain a solvent-based adhesive composition. In addition, no polyfunctional alcohol was blended in the reference example.

[table 3]

Next, after applying the obtained adhesive composition to the peeling surface of a PET film (manufactured by Mitsubishi Polyester Film, MRF38) with a thickness of 38 μm of a peeling film that has been subjected to a silicone treatment, the adhesive composition is set to a predetermined temperature and relative humidity. Dry it in an air-circulating constant temperature oven for 2 minutes to form the adhesive sheets of Examples 1-4, Comparative Examples 1-6, and Reference Examples 1 and 2 (adhesive thickness: 15 µm). The coating of the adhesive composition uses a fountain coating machine. The drying conditions and the evaluation results of the produced adhesive sheets are shown in Table 4 below. In addition, the drying condition with a dew point of 15°C corresponds to summer, and the dry condition of 2°C corresponds to winter.

[Table 4]

As shown in Table 4, for the reference examples not containing polyfunctional alcohols, their durability decreased under dry conditions corresponding to a winter dew point of 2°C. On the other hand, in the examples containing polyfunctional alcohols with a molecular weight of 200 or less in a predetermined blending amount, the durability of the adhesive sheet was suppressed without being affected by seasonal fluctuations.

Industrial availability The adhesive composition of the present invention can be used to manufacture adhesive sheets for image display devices.

1: Adhesive sheet 2: Optical film 2A: Retardation film 2B: polarizer 3: Peel off the lining 4: interlayer adhesive 5: Protective film 6: Image forming layer 7: Substrate 10A, 10B, 10C, 10D: optical laminates 11: Image display device

Fig. 1 is a cross-sectional view schematically showing an example of the 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.

1: Adhesive sheet

Claims (17)

An adhesive composition comprising a (meth)acrylic polymer (A) as a main component, and further comprising: a crosslinking agent (B), which has a functional group reactive with a hydroxyl group; and, a polyfunctional alcohol (C); The molecular weight of the aforementioned polyfunctional alcohol (C) is 240 or less; The compounding quantity of the said polyfunctional alcohol (C) is 0.5 weight part or more and 20 weight part or less with respect to 100 weight part of said (meth)acryl-type polymers (A). The adhesive composition according to claim 1, wherein the polyfunctional alcohol (C) is more than trifunctional. The adhesive composition according to claim 1, wherein the polyfunctional alcohol (C) is trimethylolpropane. The adhesive composition according to any one of claims 1 to 3, wherein the aforementioned functional group of the aforementioned crosslinking agent (B) is an isocyanate group. The adhesive composition according to any one of claims 1 to 4, wherein the aforementioned crosslinking agent (B) is diisocyanate toluene. The adhesive composition according to any one of claims 1 to 5, wherein the aforementioned crosslinking agent (B) is more than trifunctional. The adhesive composition according to any one of Claims 1 to 6, wherein the blending amount of the aforementioned crosslinking agent (B) is 0.5 parts by weight relative to 100 parts by weight of the aforementioned (meth)acrylic polymer (A). Above and below 30 parts by weight. The adhesive composition according to any one of claims 1 to 7, wherein the (meth)acrylic polymer (A) contains a structural unit derived from an aromatic ring-containing monomer. The adhesive composition according to any one of claims 1 to 8, wherein the (meth)acrylic polymer (A) contains a constituent unit derived from a hydroxyl group-containing monomer in a content of 1% by weight or less. The adhesive composition according to any one of claims 1 to 9, wherein the equivalent ratio of the functional groups of the crosslinking agent (B) to the hydroxyl groups of the polyfunctional alcohol (C) is 1 to 5. The adhesive composition according to any one of Claims 1 to 10, which is a solvent type. An adhesive sheet formed of the adhesive composition according to any one of Claims 1 to 11. As in the adhesive sheet of claim 12, the storage elastic modulus G' at 25°C is 0.5 MPa or more. An optical laminate comprising the adhesive sheet and optical film according to claim 12 or 13. An image display device comprising the optical laminate according to claim 14. A method of manufacturing an adhesive sheet, comprising the following steps: Coating the adhesive composition according to any one of claims 1 to 11 on the substrate to form a coating film; and The aforementioned coating film was dried. The manufacturing method according to claim 16, which is to dry the aforementioned coating film at a temperature of 130° C. or lower.

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