JP2012167188A - Optical self-adhesive composition, optical self-adhesive layer and optical self-bondable laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical self-adhesive composition formable of an optical self-bondable layer achieving both self-bonding properties and a high refractive index; an optical self-adhesive layer; and an optical self-bondable laminate.SOLUTION: This optical self-adhesive composition includes 40-200 pts.mass tackifying resin having an aromatic ring and 20-220 pts.mass aromatic phosphate-based plasticizer relative to 100 pts.mass (meth)acrylate-based polymer obtained by polymerizing raw material monomers mainly comprising a (meth)acrylate having a 1-18C alkyl group or a 1-18C cycloalkyl group.

Description

  The present invention relates to an optical pressure-sensitive adhesive composition, an optical pressure-sensitive adhesive layer, and an optical pressure-sensitive adhesive laminate, and is suitable for use in bonding an optical member such as a polarizing plate to an adherend.

  In general, optical members such as a substrate, a polarizing plate, a retardation plate, an optical compensation film, a reflection sheet, a brightness enhancement film, and an optical recording medium substrate used in a liquid crystal panel are formed from an adhesive composition. It is often formed as an optical member by being bonded to an adherend through an adhesive layer or by bonding optical members to each other by an adhesive layer. However, the optical member often has a high refractive index (for example, 1.50 or more), whereas the acrylic pressure-sensitive adhesive layer has a low refractive index (for example, 1.47). For this reason, there is a problem that a difference in refractive index occurs at the interface between the optical member or each material of the optical member and the pressure-sensitive adhesive layer, reflection occurs at the interface, and light cannot be effectively used.

  Therefore, as an acrylic pressure-sensitive adhesive having a high refractive index, an acrylic pressure-sensitive adhesive to which a tackifier resin is added (see Patent Document 1), and an acrylic pressure-sensitive adhesive copolymerized with a monomer introduced with halogen such as bromine (Patent Document 2) And an acrylic pressure-sensitive adhesive obtained by copolymerizing a monomer having an aromatic ring (see Patent Document 3) has been proposed.

JP 2002-14225 A Special table 2003-535921 gazette JP 2002-173656 A

  However, the pressure-sensitive adhesive described in Patent Document 1 has a problem that when the addition amount of the tackifier is increased, compatibility is deteriorated and a whitening phenomenon occurs, and a problem that the adhesiveness is decreased due to an increase in elastic modulus. there were. The pressure-sensitive adhesive of Patent Document 2 is not preferable in consideration of the environmental response of halogen and the influence of halogen on an adherend. Further, the pressure-sensitive adhesive of Patent Document 3 has a problem that, when the copolymerization amount of the monomer having an aromatic ring is increased, the elastic modulus is increased, and thus the pressure-sensitive adhesive property is lowered.

  In view of such circumstances, the present invention provides an optical pressure-sensitive adhesive composition, an optical pressure-sensitive adhesive layer, and an optical pressure-sensitive adhesive laminate capable of forming an optical pressure-sensitive adhesive layer that has both adhesive properties and a high refractive index. The purpose is to do.

  According to a first aspect of the present invention for solving the above problems, a raw material monomer mainly composed of a (meth) acrylic acid ester having an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 1 to 18 carbon atoms is used. 40 to 200 parts by mass of an aromatic ring-containing tackifier resin and 20 to 220 parts by mass of an aromatic phosphate ester plasticizer with respect to 100 parts by mass of a (meth) acrylic acid ester polymer obtained by polymerization It is in the optical adhesive composition characterized by the above-mentioned.

  A second aspect of the present invention resides in the optical pressure-sensitive adhesive composition according to the first aspect, wherein the aromatic phosphate ester plasticizer is represented by the following general formula (1). .

(In general formula (1), n is an integer of 1 or 2, R ₁ is independently H or CH ₃ , and R ₂ may be added to the aromatic ring to which it is added, Each independently hydrogen, an alkyl group, an alkoxy group, or an alkyl ether group (however, the total number of carbon atoms of all R ₂ is 12 or less, and R ₂ may be linear or branched). .)

  According to a third aspect of the present invention, there is an optical pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition described in the first or second aspect.

  According to a fourth aspect of the present invention, there is provided the optical pressure-sensitive adhesive layer according to the third aspect, wherein the optical pressure-sensitive adhesive layer has a refractive index of 1.535 or more.

  According to a fifth aspect of the present invention, there is provided an optical pressure-sensitive adhesive laminate comprising the optical pressure-sensitive adhesive layer according to the third or fourth aspect on at least one surface of a support.

  The optical pressure-sensitive adhesive composition of the present invention includes a (meth) acrylic acid ester polymer, a tackifier resin having an aromatic ring, and an aromatic phosphate ester plasticizer in a specific ratio, It is possible to form a pressure-sensitive adhesive layer that achieves both adhesive properties and a high refractive index. In addition, according to the present invention, it is possible to provide an optical pressure-sensitive adhesive layer and an optical pressure-sensitive adhesive laminate that have both adhesive properties and a high refractive index.

  Hereinafter, the present invention will be described in detail by classifying into (1) an optical pressure-sensitive adhesive composition, (2) an optical pressure-sensitive adhesive layer, and (3) an optical pressure-sensitive adhesive laminate.

(1) Optical pressure-sensitive adhesive composition The optical pressure-sensitive adhesive composition of the present invention is mainly composed of a (meth) acrylic acid ester having a C 1-18 alkyl group or a C 1-18 cycloalkyl group. 40 to 200 parts by mass of a tackifier resin having an aromatic ring and 100 parts by mass of an aromatic phosphate ester plasticizer with respect to 100 parts by mass of a (meth) acrylic acid ester polymer obtained by polymerizing raw material monomers 20 to 220 parts by mass are included. Thus, by including a (meth) acrylic acid ester polymer, a tackifier resin having an aromatic ring, and an aromatic phosphoric ester plasticizer in a predetermined ratio, excellent adhesive properties, An optical pressure-sensitive adhesive layer having both a high refractive index can be formed.

  Here, in the present invention, the “raw monomer” is added to the reaction system in order to form the (meth) acrylate polymer in the process of obtaining the (meth) acrylate polymer. Refers to all monomers. That is, the (meth) acrylic acid ester polymer according to the present embodiment is obtained by using a raw material monomer containing an acrylic acid ester with a specified mass ratio. In the present invention, the “solid content” refers to a product obtained by removing the solvent when the (meth) acrylic acid ester polymer or the crosslinking agent is a solvent dilution. Moreover, (meth) acrylic acid is a general term for acrylic acid or methacrylic acid, and other “(meth)” conforms to this. The polymer is a general term for homopolymers and copolymers.

  In the present invention, a pressure-sensitive adhesive layer having a high refractive index can be formed by having both a tackifier resin having an aromatic ring and an aromatic phosphate ester plasticizer. In addition, a (meth) acrylic acid ester-based polymer having high adhesive properties, a tackifier resin having an aromatic ring, and an aromatic phosphate ester plasticizer are included, thereby including a tackifier resin having an aromatic ring. An increase in the elastic modulus of the pressure-sensitive adhesive layer can be suppressed by the aromatic phosphate ester plasticizer, and high pressure-sensitive adhesive characteristics can be maintained. As a result, an optical pressure-sensitive adhesive composition having both excellent adhesive properties and a high refractive index is obtained.

  When the aromatic phosphate ester plasticizer is not included, the pressure-sensitive adhesive composition cannot form a high-refractive index pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer formed from this pressure-sensitive adhesive composition In some cases, the elastic modulus is increased and the adhesive strength is remarkably lowered. On the other hand, when the tackifier resin having an aromatic ring is not provided, a pressure-sensitive adhesive layer having a high refractive index cannot be formed.

  The (meth) acrylic acid ester polymer according to the present invention is a raw material monomer mainly composed of a (meth) acrylic acid ester having an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 1 to 18 carbon atoms. It is obtained by polymerizing. Specifically, it is a polymer obtained by polymerizing a raw material monomer mainly composed of (meth) acrylic acid ester. As the raw material monomer, any monomer having (meth) acrylic acid ester as a main component may be used, but it is preferable to include a monomer having a crosslinkable functional group that reacts with a crosslinking agent. Moreover, it is good also as what contains another copolymerizable monomer.

  The ratio of the (meth) acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 1 to 18 carbon atoms is preferably 50% by mass to 100% by mass in the raw material monomer. 70 mass% to 99.9 mass% is more preferable, and 70 mass% to 99 mass% is even more preferable. Examples of the (meth) acrylic acid ester having an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 1 to 18 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylic acid 2-methoxyethyl, (meth) acrylic acid n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid pentyl, (meth) acrylic acid hexyl, (meth) acrylic acid cyclohexyl, (meth) 2-ethylhexyl acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid n-dodecyl, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate (Meth) myristyl acrylate, and (meth) acrylate, palmityl (meth) acrylate and stearyl (meth) acrylate and the like. These may be used alone or in combination of two or more. Of these, (meth) acrylic acid esters having a C 2-10 alkyl group or a C 2-10 cycloalkyl group are preferred.

  As will be described later, the optical pressure-sensitive adhesive composition of the present invention contains an extremely large amount of an aromatic phosphate ester plasticizer. In such an optical pressure-sensitive adhesive composition, the (meth) acrylic acid ester polymer has an aromatic phosphate ester type as the average carbon number of the alkyl group of the (meth) acrylic acid ester monomer is lower. The present inventors have confirmed that the compatibility with the plasticizer is increased, the transparency of the formed optical pressure-sensitive adhesive layer is maintained, and the change in pressure-sensitive adhesive property is easily suppressed over time. This effect is achieved by the fact that most of the raw material monomers of the (meth) acrylic acid ester-based polymer have a (meth) acrylic acid ester monomer having a C 1-18 alkyl group or a C 1-18 cycloalkyl group. (For example, 90% by mass or more). The raw material monomer of the (meth) acrylic acid ester polymer is, for example, an alkyl group of a (meth) acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 1 to 18 carbon atoms. The average value of the number of carbon atoms is preferably 5.0 or less, and more preferably 4.0 or less. Thus, by lowering the average value of the carbon number of the alkyl group of the (meth) acrylic acid ester monomer, the transparency, which is an important characteristic in the use of the optical pressure-sensitive adhesive layer, may be higher. it can.

  The other copolymerizable monomer is not particularly limited as long as it is a compound copolymerizable with a (meth) acrylic acid ester having a C 1-18 alkyl group or a C 1-18 cycloalkyl group. .

  Examples of other copolymerizable monomers include monomers having a crosslinkable functional group in the molecule, and the functional group includes at least one of a hydroxyl group, an amino group, an amide group, an isocyanate group, and an epoxy group. Those are preferred. Specific examples of the monomer having a crosslinkable functional group in the molecule include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth ) (Meth) acrylic acid hydroxyalkyl esters such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; acrylamide, methacrylamide, N-methylacrylamide, N- Acrylamides such as methyl methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, acryloylmorpholine; monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate (Meth) acrylic acid monoalkylaminoalkyl such as (meth) acrylic acid monoethylaminopropyl; methacryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate; di An acryloyl monoisocyanate compound obtained by reacting an isocyanate compound or polyisocyanate compound with hydroxyethyl (meth) acrylate; a diisocyanate compound or polyisocyanate compound, a polyol compound, and hydroxyethyl (meth) acrylate; Acryloyl monoisocyanate compound obtained by reaction of glycidyl (meth) acrylate, alicyclic epoxy-containing (meth) acrylate, epoxy group-containing urea (Meth) acrylate, vinyl glycidyl ether; and the like. Of these, (meth) acrylic acid hydroxyalkyl ester is preferable in that it hardly causes alteration of the aromatic phosphate plasticizer. These may be used alone or in combination of two or more. The monomer having a crosslinkable functional group is preferably 0.1 to 10% by mass and more preferably 1 to 5% by mass in the raw material monomer of the (meth) acrylic acid ester.

  Moreover, it is preferable that a (meth) acrylic acid ester-type polymer does not contain the monomer which has a carboxyl group as another copolymerizable monomer. A monomer having a carboxyl group may cause alteration of the aromatic phosphate plasticizer when an optical pressure-sensitive adhesive layer is formed, and may cause a change in the pressure-sensitive adhesive property of the optical pressure-sensitive adhesive layer over time. Because there is. Examples of the monomer having a carboxyl group include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid.

  The (meth) acrylic acid ester-based polymer may contain a copolymerizable monomer having a polar group other than a carboxyl group in the raw material monomer. As described above, the optical pressure-sensitive adhesive layer of the present invention contains a large amount of an aromatic phosphate ester plasticizer, and the compatibility is poor depending on the raw material monomer composition of the (meth) acrylate ester copolymer. Although the (meth) acrylic acid ester polymer contains a copolymerizable monomer having a polar group other than a carboxyl group in the raw material monomer, an aromatic phosphate plasticizer The compatibility in the optical pressure-sensitive adhesive layer can be made high. Examples of the polar group of the copolymerizable monomer having a polar group other than the carboxyl group include a hydroxyl group, an amino group, an amide group, and a phenyl group, and a copolymerizable group having a hydroxyl group, an amino group, and an amide group. As the monomer, the same monomers as those mentioned above as the monomer having a crosslinkable functional group can be used, and in some cases, the copolymerizable monomer having these polar groups is crosslinkable. It also functions as a monomer having a functional group. As the copolymerizable monomer having a phenyl group, phenyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, (Meth) acrylic acid ester having an aromatic ring such as ethoxylated o-phenylphenol acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide modified cresol (meth) acrylate, ethylene oxide (EO) modified nonylphenol (meth) acrylate; vinyl benzoate Examples thereof include aromatic vinyl compounds such as acid, styrene, α-methylstyrene, and vinylbenzyl methyl ether. A copolymerizable monomer having a phenyl group is preferable because it has an effect of increasing the refractive index of the optical pressure-sensitive adhesive layer. In particular, a (meth) acrylic acid ester having an aromatic ring is preferable because it does not increase the elastic modulus of the optical pressure-sensitive adhesive layer and is less likely to lower the adhesive properties than an aromatic vinyl compound. These copolymerizable monomers having a polar group other than a carboxyl group may be used alone or in combination of two or more.

  Other copolymerizable monomers include vinyl ether compounds such as monovinyl ether and divinyl ether; conjugated diene compounds such as butadiene and isoprene; olefin compounds such as ethylene, propylene and α-methylolefins; vinyl acetate, Condensates of vinyl compounds such as vinylacetamide and acids; Nitrile compounds such as (meth) acrylonitrile;

  The (meth) acrylic acid ester polymer according to the present invention preferably has a weight average molecular weight (Mw) of 10,000 to 1,000,000, more preferably 60,000 to 900,000. Thereby, it can be set as the optical adhesive composition which can prevent bleeding out and can form the optical adhesive layer excellent in adhesive physical property. In addition, a weight average molecular weight means what was obtained by measuring by GPC (gel permeation chromatography).

  In addition, the (meth) acrylic acid ester-type polymer concerning this invention can be manufactured by arbitrary well-known polymerization methods, such as solution polymerization and block polymerization. Examples of the initiator used in the polymerization include azobisisobutylnitrile, benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide and the like.

  The form of the copolymer is not particularly limited, and any of random, block, and graft copolymers may be used.

  Examples of tackifying resins having an aromatic ring according to the present invention include styrene resins, xylene resins, aromatic modified terpene resins, terpene phenol resins, aromatic petroleum resins, coumarone / indene resins, phenol resins, and disproportionation. Examples thereof include rosin resin and rosin-modified phenol resin. These may be used alone or in combination of two or more.

  In the present invention, as described above, by blending an aromatic phosphate plasticizer, not only can the pressure-sensitive adhesive composition form a pressure-sensitive adhesive layer, but also a tackifier resin is blended. An increase in the elastic modulus of the pressure-sensitive adhesive layer can be suppressed.

Examples of the aromatic phosphate plasticizer according to the present invention include those represented by the following general formula (1). By using the aromatic phosphate plasticizer represented by the following general formula (1) as the aromatic phosphate plasticizer, an adhesive that easily achieves both excellent adhesive properties and a high refractive index. It can be set as the optical adhesive composition which can form a layer. In addition, as an aromatic phosphate ester plasticizer, 2 or more types in which the value of n of the aromatic phosphate ester plasticizer represented by the following general formula (1) and the substituents of R ₁ and R ₂ are different are used. You may use it in combination. In the following formula, if the total number of carbon atoms of all R ₂ is larger than 12, the effect of improving the refractive index is lowered, which is not preferable. This is because the effect of improving the refractive index of the aromatic phosphate ester plasticizer increases as the number of aromatic rings per unit weight increases, but the number of aromatic rings per unit weight increases the total number of carbon atoms of R _2. This is because of the decrease.

(In general formula (1), n is an integer of 1 or 2, R ₁ is independently H or CH ₃ , and R ₂ may be added to the aromatic ring to which it is added, Each independently hydrogen, an alkyl group, an alkoxy group, or an alkyl ether group (however, the total number of carbon atoms of all R ₂ is 12 or less, and R ₂ may be linear or branched) .).)

As the alkyl group, since the total carbon number of R ₂ is 12 or less, a functional group having a carbon number smaller than that of the dodecyl group can be appropriately selected. preferable. Similarly, an alkoxy group having 12 or less carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group can be selected. As the alkyl ether group, an alkyl ether group having 12 or less carbon atoms can be appropriately selected.

A typical example of the aromatic phosphate plasticizer represented by the general formula (1) is bisphenol A bis (diphenyl phosphate) (n = 1, R ₁ is a methyl group, and R ₂ is hydrogen). It is done. In addition, you may use independently, you may combine this and the thing of the other structure represented by General formula (1), and combine this with another aromatic phosphate ester plasticizer. Also good.

  Further, as other aromatic phosphate ester plasticizers, non-condensation type such as tricresyl phosphate, trixylenyl phosphate cresyl diphenyl phosphate, cresyl 2,6-xylenyl phosphate, 2-ethylhexyl diphenyl phosphate, etc. Liquid aromatic phosphate ester; non-condensable solid aromatic phosphate ester such as triphenyl phosphate; condensed liquid aroma such as 1,3-phenylene bis (dixylenyl phosphate) and bisphenol A bis (diphenyl phosphate) An aromatic phosphoric acid ester; a condensed solid aromatic phosphoric acid ester such as 1,3-phenylenebis (diphenyl phosphate). As these aromatic phosphate ester plasticizers, when a solid aromatic phosphate ester plasticizer is used, it is preferably used in combination with a liquid aromatic phosphate ester plasticizer. When these aromatic phosphate ester plasticizers are used, for example, the mass ratio of the solid aromatic phosphate ester plasticizer to the liquid aromatic phosphate ester plasticizer is 0: 100 to 60:40. It is preferable that This is because if the mass ratio of the solid aromatic phosphate exceeds 60%, the solid aromatic phosphate may be precipitated. In addition, as a phrase indicating the properties of the aromatic phosphate plasticizer, “solid” indicates a solid at 25 ° C., and “liquid” indicates a liquid at 25 ° C.

  The optical pressure-sensitive adhesive composition of the present invention has a total solid content of the tackifying resin having an aromatic ring of 40 to 200 parts by mass with respect to 100 parts by mass of the solid content of the (meth) acrylic acid ester polymer described above. The total solid content of the aromatic phosphate plasticizer is blended in an amount of 20 to 220 parts by mass. Thereby, it becomes the optical adhesive composition which can form the optical adhesive layer which made the outstanding adhesive characteristic and high refractive index compatible.

  As above-mentioned, the total amount of solid content of tackifying resin which has an aromatic ring is 40-200 mass parts with respect to 100 mass parts of (meth) acrylic acid ester polymer. If the tackifier resin having an aromatic ring is less than 40 parts by mass, a sufficiently high refractive index cannot be obtained, and if the tackifier resin having an aromatic ring is more than 200 parts by mass, sufficient adhesive properties are obtained. It becomes impossible. Further, the tackifier resin having an aromatic ring is more preferably 50 to 170 parts by mass and further preferably 60 to 150 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer. By making the pressure-sensitive adhesive resin having an aromatic ring 60 parts by mass or more, a higher refractive index can be realized, and the influence of the plastic effect of the aromatic phosphate plasticizer contributes to the improvement of the adhesive strength. In addition, it becomes easy to control the adhesive property of the optical adhesive layer. Specifically, as in Example 2 described later, when 50 parts by mass of the tackifier resin having an aromatic ring and 200 parts of a solid aromatic phosphate ester plasticizer are added in a large amount, the refractive index Is 1.5479, but as in Example 4 and Example 9 described later, if the tackifier resin having an aromatic ring is 60 parts by mass or more, the equivalent or less aromatic phosphate ester plasticizer Even if it is a compounding quantity, the optical adhesive layer which has a high refractive index of 1.55 or more can be formed.

  Moreover, as above-mentioned, the total amount of solid content of an aromatic phosphate ester plasticizer is 20-220 mass parts with respect to 100 mass parts of (meth) acrylic acid ester polymer. When the amount of the aromatic phosphate plasticizer is less than 20 parts by mass, a sufficiently high refractive index cannot be obtained, and when the amount of the aromatic phosphate ester plasticizer is more than 220 parts by mass, sufficient adhesive properties are obtained. It becomes impossible. The aromatic phosphate ester plasticizer is more preferably 40 to 160 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer. Since the optical pressure-sensitive adhesive composition of the present invention contains a predetermined amount of an aromatic phosphate ester plasticizer, in order to increase the refractive index of the optical pressure-sensitive adhesive layer, the amount of tackifying resin having an aromatic ring is increased. Even if it exists, the raise of the elasticity modulus of an optical adhesive layer can be suppressed, and a strong adhesive characteristic can be maintained.

  Furthermore, in the optical pressure-sensitive adhesive composition, if necessary, an ultraviolet absorber, a plasticizer (softener) other than the aromatic phosphate plasticizer, a curing accelerator, a filler, an anti-aging agent, a pigment, Various additives such as dyes and coupling agents can be added. Examples of the softening agent include liquid polyether, glycol ester, liquid polyterpene, liquid polyacrylate, phthalic acid ester, trimellitic acid ester, and the like. Moreover, you may add tackifiers other than the tackifier resin which has an aromatic ring. Examples of the tackifier other than the tackifier resin having an aromatic ring include rosin and derivatives thereof, polyterpene, and petroleum resins. However, tackifiers other than these tackifying resins having an aromatic ring may decrease the refractive index of the optical pressure-sensitive adhesive layer as the blending amount increases, so add them within a range that does not impair the effects of the invention. Can do. Examples of the plasticizer other than the aromatic phosphate ester include non-aromatic phosphate ester plasticizer, liquid polyether, glycol ester, liquid polyterpene, liquid polyacrylate, phthalate ester, trimellitic acid ester, and the like. However, unlike aromatic phosphate ester plasticizers, these may cause a decrease in the refractive index of the optical pressure-sensitive adhesive composition when added, and therefore can be added within a range that does not impair the effects of the invention.

  Furthermore, the optical pressure-sensitive adhesive composition may contain a solvent such as an organic solvent if necessary. When the optical pressure-sensitive adhesive composition contains a solvent, solid components ((meth) acrylic acid ester polymer according to the present invention, tackifying resin having an aromatic ring, aromatic phosphoric acid ester plasticizer, crosslinking agent) Etc.) is not particularly limited, and may be a concentration that can be applied to a predetermined substrate as it is, or a concentration that is used after dilution.

  Examples of such solvents include ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate, propyl acetate, and butyl acetate; 1,2-dimethoxyethane, tetrahydrofuran, 1,4- Ether solvents such as dioxane; halogen solvents such as chloroform, carbon tetrachloride and chlorobenzene; aromatic hydrocarbon solvents such as benzene, toluene and xylene; N, N-dimethylformamide, N, N-dimethylacetamide, Amide solvents such as N-methylpyrrolidone; Aliphatic hydrocarbon solvents such as pentane, hexane and heptane; Alicyclic hydrocarbon solvents such as cyclopentane and cyclohexane; and a mixed solvent composed of two or more of these solvents And so on.

  The optical pressure-sensitive adhesive composition of the present invention becomes an optical pressure-sensitive adhesive layer by being diluted as necessary and then coated on a support such as a predetermined substrate. In addition, when applying an optical adhesive composition, it is preferable to adjust a density | concentration using these organic solvents etc. for viscosity adjustment. The concentration is preferably adjusted to be in the range of 10 to 60% by mass.

  The optical pressure-sensitive adhesive composition may be applied after being prepared in advance and stored for a certain period of time. For example, by adding only a crosslinking agent several hours before the coating, the optical pressure-sensitive adhesive composition After completion of the product, it may be applied without leaving the day, or two or more liquids may be mixed with a static mixer or the like, and the completion of the optical pressure-sensitive adhesive composition and application may be performed continuously.

  As described above, the optical pressure-sensitive adhesive composition of the present invention is capable of forming an optical pressure-sensitive adhesive layer having both adhesive properties and a high refractive index. Further, since this optical pressure-sensitive adhesive composition does not use halogen or the like, there is no problem of contamination of the adherend or the like and environmental pollution.

(2) Optical pressure-sensitive adhesive layer The optical pressure-sensitive adhesive layer of the present invention is formed from the optical pressure-sensitive adhesive composition described above.

  When forming the optical pressure-sensitive adhesive layer using the optical pressure-sensitive adhesive composition described above, it is preferable to crosslink the optical pressure-sensitive adhesive composition with a crosslinking agent.

  The type of the crosslinking agent is not particularly limited, and specific examples include isocyanate compounds, epoxy compounds, metal chelate compounds, melamine resins, aziridine compounds, metal alkoxides, metal salts and the like. From the viewpoint of obtaining an appropriate cohesive force, an isocyanate compound or an epoxy compound is particularly preferably used. These compounds may be used alone or in combination of two or more.

  As the isocyanate compound, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4-tolylene diisocyanate, 4,4 '-Diphenylmethane diisocyanate, aromatic diisocyanates such as xylylene diisocyanate; trimethylolpropane / tolylene diisocyanate 3 adduct (for example, Nippon Polyurethane Industry, trade name: Coronate L, Toyo Ink, trade name: BHS- 8515, manufactured by Soken Chemical Co., Ltd., trade name: L-45), trimethylolpropane / hexamethylene diisocyanate 3 adduct (for example, Nippon Polyurethane Industry) Ltd., trade name: Coronate HL), an isocyanurate of hexamethylene diisocyanate (for example, Nippon Polyurethane Industry Co., Ltd., trade name: Coronate HX) isocyanate adducts and the like; and the like. These isocyanate compounds may be used alone or in combination of two or more.

  Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine (for example, Mitsubishi Gas Chemical Company, trade name: TETRAD-X), and 1,3-bis (N, N-dioxy). Examples include glycidylaminomethyl) cyclohexane (for example, trade name: TETRAD-C manufactured by Mitsubishi Gas Chemical Company, Inc.). These compounds may be used alone or in combination of two or more.

  These crosslinking agents may be previously contained in the optical pressure-sensitive adhesive composition of the present invention. The amount of these crosslinking agents used is preferably 0.01 to 15 parts by mass, and 0.1 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer according to the present invention. More preferably, it is contained in part. By setting the crosslinking agent in the above range, good adhesion and durability can be obtained. When the content of the cross-linking agent is less than 0.01 parts by mass, the cross-linking is insufficient and the cohesive force of the optical pressure-sensitive adhesive composition is reduced, which may cause adhesive residue. On the other hand, when the content is more than 15 parts by mass, the cohesive force is increased, the fluidity is lowered, the wetness to the adherend is insufficient, and peeling may be caused.

  The optical pressure-sensitive adhesive layer formed by the optical pressure-sensitive adhesive composition of the present invention has a high refractive index. For example, it is irradiated with sodium D rays in an atmosphere at 23 ° C., and Abbe refractometer (( The refractive index measured by Atago Co., Ltd.:ABBE REFRACTO METER DR-M2) can be 1.535 or more.

  In this invention, when the compounding quantity of tackifying resin which has an aromatic ring with respect to 100 mass parts of (meth) acrylic acid ester-type polymers is increased in the optical adhesive composition, the refractive index of an optical adhesive layer becomes this. The present inventors have confirmed that it rises monotonously with this. In addition, it has been confirmed that the refractive index of the optical pressure-sensitive adhesive layer monotonously increases as the blending amount of the aromatic phosphate plasticizer with respect to 100 parts by mass of the (meth) acrylate polymer is increased. . From this, the refractive index of the optical pressure-sensitive adhesive composition of the present invention is desired by appropriately adjusting the blending amount of the tackifier resin having an aromatic ring and / or the blending amount of the aromatic phosphate plasticizer. For example, 1.535 or more.

  The preferred adhesive properties of the optical pressure-sensitive adhesive layer of the present invention vary depending on the application in which it is used, but a 20 μm optical pressure-sensitive adhesive layer is provided based on a 50 μm polyethylene terephthalate film, and conforms to JIS Z0237: 2000. The adhesive force measured within 1 minute from sticking is preferably 0.5 N / 25 mm to 25 N / 25 mm, and more preferably 1.5 N / 25 mm to 20 N / 25 mm.

  The optical pressure-sensitive adhesive layer of the present invention preferably has a refractive index of 1.535 or more and 1.540 or more in that the difference in refractive index from the high refractive index optical member to be bonded can be reduced. Is more preferable.

  Since the optical pressure-sensitive adhesive layer of the present invention exhibits a high refractive index, when the optical member is bonded to another member or the optical members are bonded to each other, the difference in refractive index from the adjacent layer is low. The reflection of light at the interface between the adjacent layer and the optical pressure-sensitive adhesive layer can be reduced. Since the optical pressure-sensitive adhesive layer of the present invention has a high refractive index (for example, 1.535 or more), the layer adjacent to the optical pressure-sensitive adhesive layer of the present invention is made of a material having a refractive index of 1.535 or more. Even if it is, it can be in a state where there is no difference in refractive index between adjacent layers or the difference in refractive index can be remarkably reduced, and it is possible to achieve both suppression of reflection at the interface and adhesive properties, which is preferable. Can be used. The optical pressure-sensitive adhesive layer of the present invention can also be used when the adjacent layer has a refractive index of less than 1.535.

(3) Optical adhesive laminate The optical adhesive laminate of the present invention has the optical adhesive layer of the present invention on at least one surface of a support. The support herein includes a release sheet in addition to the base substrate. The base substrate is added to the optical adhesive laminate without being removed even after the optical adhesive laminate is used for the intended use, and the core material, protective material, non-permeable material, It plays a role as an optical member or the like.

  The optical pressure-sensitive adhesive laminate may or may not have a base substrate. Specific examples include those having an optical pressure-sensitive adhesive layer on at least one side of the base substrate, those having an optical pressure-sensitive adhesive layer on both sides of the base substrate, and the release treatment surface of the release sheet instead of the base substrate. What has an optical adhesive layer is mentioned. Moreover, you may stick a peeling sheet on the optical adhesive layer (exposed surface of an optical adhesive layer) as needed. The release sheet can protect the optical pressure-sensitive adhesive layer.

  The base substrate is not particularly limited. For example, polyaddition of a compound having an unsaturated carbon bond of polyvinyl alcohol, polymethyl methacrylate, polystyrene, polyvinyl chloride, polyethylene, polypropylene, and an ethylene / vinyl acetate copolymer. Cycloolefin polymer; Polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polyarylate; Polycarbonate; Polyethersulfone; Polyphenylene sulfide, Polynorbornene resin; Triacetyl cellulose; Polyurethane resin; Polyimide resin The plastic material which made the sheet form the single or 2 types or more mixture, or these laminated bodies is mentioned. The base substrate may be provided with a coat layer, a vapor deposition layer, and the like, and may be physically modified such as corona treatment and electron beam treatment. The base substrate is appropriately selected depending on the use of the optical adhesive laminate. The thickness of such a base substrate is usually 6 to 300 μm, preferably 12 to 200 μm.

The release sheet is not particularly limited, and it is possible to use a sheet such as paper or film that has been subjected to a release treatment with a release agent. Examples of the paper include high-density base paper such as glassine paper, clay-coated paper, kraft paper, or paper obtained by laminating a film such as polyethylene on high-quality paper. As a film, the film which consists of resin, such as a polyethylene terephthalate, a polypropylene, polyethylene, or those foamed films is mentioned, for example. Examples of the release agent include a fluororesin, a silicone resin, and a long chain alkyl group-containing carbamate resin. A release agent is suitably used as a release sheet by applying a release agent to a sheet so that the dry mass is about 0.1 to 3 g / m ² and providing a release layer by heat curing or UV curing.

  Examples of the adherend to which the optical pressure-sensitive adhesive laminate of the present invention is adhered include a display substrate, a polarizing plate, a retardation plate, an optical compensation film, a reflective sheet, a brightness enhancement film, a contrast enhancement film, and an optical recording medium. An optical member such as a substrate for use. Examples of the material used for these include the same materials as those for the base substrate.

  Since the optical pressure-sensitive adhesive layer of the present invention used in the optical pressure-sensitive adhesive laminate of the present invention exhibits a high refractive index, the support and / or the adherend is variously selected depending on the application. Also, the difference in refractive index can be made small, and the reflection of light at the interface between the support and / or the adherend and the optical pressure-sensitive adhesive layer can be made low.

  Specific refractive index values of the materials constituting the support and / or the adherend of the optical pressure-sensitive adhesive laminate of the present invention are, for example, 1.49 to 1.53 for polyvinyl alcohol and 1 for polymethyl methacrylate. .49, polystyrene 1.59, polyvinyl chloride 1.53, polyethylene 1.53-1.54, cycloolefin polymer 1.53, polyethylene terephthalate 1.60, polyarylate 1.61, polycarbonate Is 1.585, polyethersulfone is 1.63, triacetylcellulose is 1.49, and fluorine-based polyimide is 1.53. In the optical pressure-sensitive adhesive laminate of the present invention, the optical pressure-sensitive adhesive layer has a high refractive index. Therefore, when the support and / or the adherend is made of a material having a refractive index of 1.535 or more, the support and / or While maintaining the high refractive index of the adherend, it is possible to realize a substrate and / or an adhesive having excellent adhesion between the adherend and the optical pressure-sensitive adhesive layer. Further, since the refractive index of the optical pressure-sensitive adhesive layer can be easily controlled, even when the support and / or the adherend is made of a material having a refractive index of less than 1.535, the support and / or the adherend is used. The difference in the refractive index at the interface between the body and the optical pressure-sensitive adhesive layer is small, and it is possible to realize a material having excellent adhesion between the support and / or the adherend and the optical pressure-sensitive adhesive layer.

  The manufacturing method of the optical adhesive laminated body of this invention is demonstrated.

  First, an optical pressure-sensitive adhesive composition coating solution is prepared by fluidizing an optical pressure-sensitive adhesive composition by previously containing an organic solvent, diluting with an organic solvent, or heating.

  Then, the obtained optical pressure-sensitive adhesive composition coating liquid may be directly applied to the surface of the base substrate to form an optical pressure-sensitive adhesive layer on the base substrate, or the optical pressure-sensitive adhesive layer may be formed on the release sheet. After the pressure-sensitive adhesive composition coating liquid is applied to form an optical pressure-sensitive adhesive layer, it may be transferred to a base substrate or another release sheet. The method for applying the optical adhesive composition coating liquid is not particularly limited, and examples thereof include a roll knife coater, a die coater, a roll coater, a bar coater, a gravure roll coater, a reverse roll coater, and a dipping method. After applying the optical pressure-sensitive adhesive composition coating solution by these methods, the optical pressure-sensitive adhesive layer may be heat-treated in order to promote crosslinking and / or remove the solvent when it contains a solvent, The heat treatment temperature is, for example, 50 to 150 ° C. The thickness of the optical pressure-sensitive adhesive layer is not particularly limited and is appropriately selected depending on the application, but is usually preferably about 1 to 200 μm and more preferably about 10 to 100 μm in a dry state.

  The optical pressure-sensitive adhesive laminate of the present invention comprises an optical pressure-sensitive adhesive layer comprising the above-mentioned optical pressure-sensitive adhesive composition, and has both excellent adhesive properties and a high refractive index.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, these do not restrict | limit the scope of the present invention at all.

Example 1
95 parts by mass of n-butyl acrylate (described as BA in Table 1), 5 parts by mass of 2-hydroxyethyl acrylate (described as HEA in Table 1), 0.6 parts by mass of azobisisobutyronitrile, acetic acid 150 parts by mass of ethyl was mixed and polymerized at 60 ° C. for 18 hours in a nitrogen atmosphere to obtain an acrylate copolymer solution (solid content: 35% by mass) having a mass average molecular weight of 500,000. The mass average molecular weight of the polymer was measured by GPC (polystyrene conversion).

  17.5 parts by mass of α-methylstyrene-based tackifier resin (1) (solid content: 100% by mass) (manufactured by Eastman Chemical Co .: Picotex LC) with respect to 100 parts by mass of the obtained copolymer solution 35 parts by mass of bisphenol A bis (diphenyl phosphate) (solid content: 100% by mass) (described as BPBDPP in Table 1) (manufactured by Daihachi Chemical Industry Co., Ltd .: CR-741) as a liquid phosphate ester plasticizer 2.7 parts by mass of a range isocyanate cross-linking agent (solid content: 35.0% by mass) (manufactured by Toyo Ink Manufacturing Co., Ltd .: BXX5640) was blended to obtain an adhesive composition.

  This pressure-sensitive adhesive composition is applied to the release-treated surface of a release film (manufactured by Lintec Corporation: SP-PET 381031) using a roll knife coater, and heated and dried at 90 ° C. for 1 minute, thereby giving an adhesive having a thickness of about 20 μm. A pressure-sensitive adhesive layer was prepared by laminating a polyethylene terephthalate film 50 μm (manufactured by Toray Industries Inc .: Lumirror 50T60) on the surface of the pressure-sensitive adhesive layer.

(Example 2)
An adhesive laminate was produced in the same manner as in Example 1 except that 70 parts by mass of bisphenol A bis (diphenyl phosphate) was used.

(Example 3)
An adhesive laminate was produced in the same manner as in Example 1 except that the α-methylstyrene-based tackifying resin (1) was changed to 24.5 parts by mass.

Example 4
An adhesive laminate was prepared in the same manner as in Example 1 except that 24.5 parts by mass of the α-methylstyrene-based tackifier resin (1) and 70 parts by mass of bisphenol A bis (diphenyl phosphate) were used.

(Example 5)
An adhesive laminate was produced in the same manner as in Example 1 except that 35 parts by mass of the α-methylstyrene-based tackifying resin (1) and 17.5 parts by mass of bisphenol A bis (diphenyl phosphate) were used.

(Example 6)
An adhesive laminate was produced in the same manner as in Example 1 except that 35 parts by mass of the α-methylstyrene-based tackifying resin (1) was changed.

(Example 7)
An adhesive laminate was prepared in the same manner as in Example 1 except that 45.5 parts by mass of the α-methylstyrene-based tackifier resin (1) and 10.5 parts by mass of bisphenol A bis (diphenyl phosphate) were used. .

(Example 8)
An adhesive laminate was produced in the same manner as in Example 1 except that 45.5 parts by mass of the α-methylstyrene-based tackifying resin (1) and 17.5 parts by mass of bisphenol A bis (diphenyl phosphate) were used. .

Example 9
A tacky laminate was prepared in the same manner as in Example 1 except that 56 parts by mass of the α-methylstyrene tackifying resin (1) was used.

(Example 10)
α-methylstyrene-based tackifier resin (1) Instead of 35 parts by mass, styrene-based tackifier resin (2) (solid content: 100% by mass) (SX-100) manufactured by Yasuhara Chemical Co., Ltd .: 24.5 parts by mass An adhesive laminate was prepared in the same manner as in Example 1 except that was used.

(Example 11)
Instead of bisphenol A bis (diphenyl phosphate), cresyl 2,6-xylenyl phosphate (solid content: 100% by mass), which is a non-condensed liquid phosphate ester (denoted as CDXP in Table 1) (Daihachi Chemical Industry) Co., Ltd .: PX-110) 31.5 parts by mass, α-methylstyrene-based tackifier resin (1) 31.5 parts by mass, xylene diisocyanate-based crosslinking agent 1.4 parts by mass A tacky laminate was produced in the same manner as in Example 1 except that.

(Example 12)
Instead of bisphenol A bis (diphenyl phosphate), 21 parts by mass of cresyl 2,6-xylenyl phosphate (manufactured by Daihachi Chemical Industry Co., Ltd .: PX-110) which is a non-condensable liquid phosphate ester and condensed solid phosphorus 1,3-phenylenebis (dixylenyl phosphate) which is an acid ester (solid content: 100% by mass) (described as PDXP in Table 1) (manufactured by Daihachi Chemical Industry Co., Ltd .: PX-200) 28 mass In the same manner as in Example 1, except that 28 parts by mass of the α-methylstyrene-based tackifying resin (1) and 1.4 parts by mass of the xylene diisocyanate-based crosslinking agent are used. Was made.

(Comparative Example 1)
Example except that n-butyl acrylate was 98 parts by mass, 2-hydroxyethyl acrylate was 2 parts by mass, and α-methylstyrene-based tackifier resin (1) and bisphenol A bis (diphenyl phosphate) were not used. In the same manner as in Example 1, an adhesive laminate was produced.

(Comparative Example 2)
98 parts by mass of n-butyl acrylate and 2 parts by mass of 2-hydroxyethyl acrylate are used, and 10.5 mass of styrene-based tackifier resin (2) is used instead of α-methylstyrene-based tackifier resin (1). The adhesive laminate was prepared in the same manner as in Example 1 except that bisphenol A bis (diphenyl phosphate) was not used, but the acrylic ester copolymer and the styrenic tackifier resin (2) The phases were separated and an adhesive layer could not be obtained.

(Comparative Example 3)
98 parts by mass of n-butyl acrylate and 2 parts by mass of 2-hydroxyethyl acrylate, instead of α-methylstyrene type tackifying resin (1), aromatic modified terpene type tackifying resin (3) (Yasuhara Chemical) Co., Ltd .: TO125) (solid content: 100% by mass) 9.7 parts by mass, except that bisphenol A bis (diphenyl phosphate) was not used, the adhesive laminate was produced in the same manner as in Example 1. However, the acrylic ester copolymer and the aromatic-modified terpene-based tackifier resin (3) were phase-separated and the pressure-sensitive adhesive layer could not be obtained.

(Comparative Example 4)
98 parts by mass of n-butyl acrylate, 2 parts by mass of 2-hydroxyethyl acrylate, 3.6 parts by mass of α-methylstyrene-based tackifier resin (1), and bisphenol A bis (diphenyl phosphate) A pressure-sensitive adhesive laminate was produced in the same manner as in Example 1 except that there was not.

(Comparative Example 5)
98 parts by mass of n-butyl acrylate, 2 parts by mass of 2-hydroxyethyl acrylate, 10.6 parts by mass of α-methylstyrene-based tackifier resin (1), and bisphenol A bis (diphenyl phosphate) A pressure-sensitive adhesive laminate was produced in the same manner as in Example 1 except that there was not.

(Comparative Example 6)
98 parts by mass of n-butyl acrylate, 2 parts by mass of 2-hydroxyethyl acrylate, 10.6 parts by mass of α-methylstyrene-based tackifier resin (1), and 35 bisphenol A bis (diphenyl phosphate) An adhesive laminate was produced in the same manner as in Example 1 except that the content was 2 parts by mass.

(Comparative Example 7)
An adhesive laminate was produced in the same manner as in Example 1 except that bisphenol A bis (diphenyl phosphate) was not used.

(Comparative Example 8)
An adhesive laminate was produced in the same manner as in Example 3 except that bisphenol A bis (diphenyl phosphate) was not used.

(Comparative Example 9)
An adhesive laminate was produced in the same manner as in Example 5 except that bisphenol A bis (diphenyl phosphate) was not used.

(Comparative Example 10)
An adhesive laminate was produced in the same manner as in Example 7 except that bisphenol A bis (diphenyl phosphate) was not used.

(Comparative Example 11)
An adhesive laminate was produced in the same manner as in Example 9 except that bisphenol A bis (diphenyl phosphate) was not used.

  Evaluation of the adhesive laminated body of each said Example and each comparative example was performed as follows. The results are shown in Tables 1 and 2.

<Refractive index>
The refractive index of the pressure-sensitive adhesive layer was irradiated with sodium D rays in an atmosphere of 23 ° C., and the refractive index was measured with an Abbe refractometer (manufactured by Atago Co., Ltd .: ABBE REFRACTO METER DR-M2). In addition, a refractive index is not measured about the thing which the tackifier resin which has an acrylate ester copolymer and an aromatic ring, and the adhesive layer was not obtained, and it describes as "-" in Table 2. .

<Adhesion measurement>
The release film of the adhesive laminate was peeled off, and the adhesive strength of the test adhesive laminate with the PET film as a support to the SUS plate # 360 was measured according to JIS Z 0237. In addition, the measurement was performed within 1 minute after application (23 ° C. × 50% RH). In the adhesive force measurement, when zipping occurs, it is described as “Z” in Tables 1 and 2, and when adhesive residue occurs due to cohesive failure, it is described as “Cf” in Table 1, and the adhesive layer is When peeled off from the support, it was described as “AT” in Tables 1 and 2. Moreover, when these generate | occur | produced slightly, it described as "LL." In addition, a refractive index is not measured about the thing which the tackifier resin which has an acrylate ester copolymer and an aromatic ring, and the adhesive layer was not obtained, and it describes as "-" in Table 2. .

(Summary of results)
The pressure-sensitive adhesive layer of Comparative Example 1 formed from a pressure-sensitive adhesive resin containing an aromatic and a pressure-sensitive adhesive composition not containing an aromatic phosphate plasticizer had a refractive index of 1.4664.

  On the other hand, each of the pressure-sensitive adhesive layers of Examples 1 to 12 in which an aromatic-containing tackifier resin and an aromatic phosphate plasticizer are blended at a predetermined ratio have excellent adhesive properties. At the same time, it had a high refractive index (refractive index of 1.5358 or more).

  As for the adhesive layer of Examples 1-12, the refractive index rose all compared with the adhesive layer which does not contain the aromatic phosphate ester plasticizer. Specifically, the pressure-sensitive adhesive layers of Examples 1 and 2 had a refractive index increased by 0.0277 or more as compared with the pressure-sensitive adhesive layer of Comparative Example 7 in which no phosphate ester plasticizer was blended. . The refractive index of the pressure-sensitive adhesive layers of Examples 3 and 4 increased by 0.0218 or more compared to the pressure-sensitive adhesive layer of Comparative Example 8 in which no phosphate ester plasticizer was blended. The refractive index of the pressure-sensitive adhesive layers of Examples 5 and 6 increased by 0.0102 or more as compared with the pressure-sensitive adhesive layer of Comparative Example 9 in which no phosphate ester plasticizer was blended. In the pressure-sensitive adhesive layers of Examples 7 and 8, the refractive index was increased by 0.0036 or more as compared with the pressure-sensitive adhesive layer of Comparative Example 10 in which no phosphate ester plasticizer was blended. The refractive index of the pressure-sensitive adhesive layer of Example 9 was increased by 0.0112 compared to the pressure-sensitive adhesive layer of Comparative Example 11 in which no phosphate ester plasticizer was blended.

  Further, in the pressure-sensitive adhesive layer of Comparative Example 6 containing an aromatic phosphate ester plasticizer and the amount of the tackifying resin having an aromatic ring being less than 40% by mass, an aromatic phosphate ester plasticizer is added. Although the refractive index increased compared with Comparative Example 5 that was not, it did not have a sufficient refractive index of, for example, 1.535 or more.

  The pressure-sensitive adhesive layers of Comparative Example 10 and Comparative Example 11 that did not contain an aromatic phosphate ester plasticizer had a high refractive index, but the pressure-sensitive adhesive layer had become hard, so the adhesive strength was It was low. From this, it was found that when a large amount of a tackifier resin having an aromatic ring was blended without blending an aromatic phosphate ester plasticizer, the tackiness characteristics were greatly lowered.

  As mentioned above, the (meth) acrylic acid ester obtained by polymerizing the monomer mixture which has as a main component the (meth) acrylic acid ester which has a C1-C18 alkyl group or a C1-C18 cycloalkyl group. An optical pressure-sensitive adhesive composition containing 40 to 200 parts by mass of a tackifier resin having an aromatic ring and 20 to 220 parts by mass of an aromatic phosphate ester plasticizer with respect to 100 parts by mass of a polymer is an excellent adhesive. It was found that an optical pressure-sensitive adhesive layer having both characteristics and a high refractive index can be formed.

Moreover, in the Example mentioned above, the outstanding adhesive characteristic and high refractive index were obtained by using the acrylate ester copolymer which used n-butyl acrylate and 2-hydroxyethyl acrylate as a raw material monomer. It has been confirmed that a compatible optical pressure-sensitive adhesive layer can be formed, but the effect of the present invention is also achieved when a (meth) acrylic acid ester having an alkyl group or cycloalkyl group having another carbon number is used. Unless a special material that impairs the optical properties is used, it is expected that an optical pressure-sensitive adhesive layer having both excellent adhesive properties and a high refractive index can be formed.

Claims (5)

A (meth) acrylic acid ester polymer obtained by polymerizing a raw material monomer mainly composed of a (meth) acrylic acid ester having a C 1-18 alkyl group or a C 1-18 cycloalkyl group An optical pressure-sensitive adhesive composition comprising 40 to 200 parts by mass of a tackifying resin having an aromatic ring and 20 to 220 parts by mass of an aromatic phosphate plasticizer with respect to 100 parts by mass. The optical pressure-sensitive adhesive composition according to claim 1, wherein the aromatic phosphate ester plasticizer is represented by the following general formula (1).

(In general formula (1), n is an integer of 1 or 2, R ₁ is independently H or CH ₃ , and R ₂ may be added to the aromatic ring to which it is added, Each independently hydrogen, an alkyl group, an alkoxy group, or an alkyl ether group (however, the total number of carbon atoms of all R ₂ is 12 or less, and R ₂ may be linear or branched). .) An optical pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition according to claim 1. The optical pressure-sensitive adhesive layer according to claim 3, wherein the optical pressure-sensitive adhesive layer has a refractive index of 1.535 or more. An optical pressure-sensitive adhesive laminate comprising the optical pressure-sensitive adhesive layer according to claim 3 or 4 on at least one surface of a support.