JP4535798B2 - Optical member pressure-sensitive adhesive composition, optical member pressure-sensitive adhesive layer, optical member pressure-sensitive adhesive sheet, pressure-sensitive adhesive optical member, and image display device - Google Patents

Description

  The present invention relates to an acrylic pressure-sensitive adhesive composition for optical members. More specifically, the present invention relates to a pressure-sensitive adhesive composition having excellent removability. The present invention also relates to an adhesive sheet for optical members having the adhesive layer, an optical member with an adhesive, and a liquid crystal display device, an organic EL display device, a PDP, etc. using the optical member with an adhesive. The present invention relates to a display device. In particular, the pressure-sensitive adhesive sheets of the present invention are used for the purpose of protecting the surface of an optical member such as a polarizing plate, a wave plate, a retardation plate, an optical compensation film, a reflection sheet, a brightness enhancement film, or a laminate of these. It is useful as a pressure-sensitive adhesive sheet.

  An optical member used for a liquid crystal display device or the like, for example, a polarizing plate or a retardation plate is attached to a liquid crystal cell using an adhesive. Since the material used for such an optical member has a large expansion and contraction under a heating condition or a humidifying condition, the material is likely to float or peel off after being attached. For this reason, the pressure-sensitive adhesive for optical members is required to have durability that can cope with heating conditions and humidification conditions.

  When the optical member is stuck, if a foreign object is caught in the bonding surface or the bonding position is misplaced, the optical member is removed from the liquid crystal cell and the liquid crystal cell is reused. When such an optical member is peeled off from the liquid crystal cell, it is necessary not to have an adhesive state that changes or breaks the gap of the liquid crystal cell. The However, if the technique of simply raising the adhesion state is employed with emphasis on the durability of the pressure-sensitive adhesive for optical members, the removability is poor.

  In addition, the pressure-sensitive adhesive for optical members is required to uniformly relieve stress caused by dimensional changes of optical members such as polarizing plates under heating conditions and humidification conditions. If the stress relaxation property is inferior, residual stress may remain in an optical member such as a polarizing plate, which may cause adverse effects such as color unevenness and white spots.

  Conventionally, solvent-type acrylic pressure-sensitive adhesives have been used for such applications, but since these solvent-type acrylic pressure-sensitive adhesives are synthesized in an organic solvent, volatilization of the solvent during coating is environmentally friendly. Therefore, conversion to a water-dispersed acrylic emulsion type adhesive is being attempted.

A (meth) acrylic polymer pressure-sensitive adhesive sheet containing a silane monomer as an essential constituent is known as a water-dispersed acrylic emulsion type pressure-sensitive adhesive (see, for example, Patent Document 1). However, in this pressure-sensitive adhesive sheet, a water-dispersed pressure-sensitive adhesive containing an aqueous dispersion obtained by copolymerization with a silane monomer and an aqueous system improves adhesive strength over time and develops a strong bonding force. It is difficult to combine re-peelability with the above-mentioned durability.
JP 2002-309212 A

  Accordingly, an object of the present invention is an acrylic pressure-sensitive adhesive that can be applied in water as an environmental measure in order to solve the problems in conventional acrylic pressure-sensitive adhesives, and has durability, removability, and stress relaxation properties. It is providing the adhesive composition for optical members which is excellent in it. Moreover, it is providing the adhesive layer for optical members formed with the said adhesive composition for optical members. Furthermore, it is providing the adhesive type optical member which has the said adhesive layer, and the image display apparatus using the said adhesive type optical member.

  As a result of intensive studies on the base polymer component in order to achieve the above object, the present inventors have found that a (meth) acrylic polymer (A) obtained by emulsion polymerization containing a specific amount of unsaturated carboxylic acid monomer units. ), A pressure-sensitive adhesive composition containing a (meth) acrylic polymer (B) having a specific carboxylic acid equivalent weight in the range of 2000 to 50000, and a small amount of a silane coupling agent. It has been found that a pressure-sensitive adhesive composition for an optical member that is excellent in properties, removability and stress relaxation properties can be obtained, and the present invention has been completed.

  That is, the pressure-sensitive adhesive composition of the present invention contains 0.2 to 2% by weight of unsaturated carboxylic acid as a monomer unit, (meth) acrylic polymer (A) 100 parts by weight obtained by emulsion polymerization, and as a monomer unit. (Meth) acrylic containing 1 to 7% by weight of unsaturated carboxylic acid, having a carboxylic acid equivalent greater than that of the (meth) acrylic polymer (A), and having a weight average molecular weight in the range of 2000 to 50000 It is characterized by containing 0.1 to 20 parts by weight of the polymer (B) and 0.01 to 1 part by weight of a silane coupling agent.

  The (meth) acrylic polymer in the present invention refers to an acrylic polymer and / or a methacrylic polymer, and (meth) acrylate refers to an acrylate and / or methacrylate.

  Further, the carboxylic acid equivalent of the (meth) acrylic polymer in the present invention is the amount of carboxylic acid groups per 1 g of the polymer. For example, when the carboxylic acid is derived from acrylic acid, the acrylic acid contained in 1 g of the polymer Is a value (equivalent / g) calculated by dividing the weight of the product by the molecular weight of acrylic acid.

  According to the present invention, as shown in the results of the examples, the (meth) acrylic polymer (A) obtained by emulsion polymerization containing a specific amount of the above-described unsaturated carboxylic acid monomer unit, the weight average molecular weight is The pressure-sensitive adhesive layer crosslinked with a pressure-sensitive adhesive composition containing a (meth) acrylic polymer (B) having a specific carboxylic acid equivalent in a range of 2000 to 50000 and a small amount of a silane coupling agent is durable. , Removability and stress relaxation properties are excellent. Although the details of the reason why the crosslinked product of the base polymer using the above components as the main component exhibits such characteristics are not clear, the (meth) acrylic polymer (B) is more hydrophilic than the (meth) acrylic polymer (A). Since it is large, it surrounds the outside of the emulsion particles, or moves to the interface between the liquid crystal cell and the pressure-sensitive adhesive to prevent an increase in adhesive force. As a result, the optical member is attached to the liquid crystal cell and then undergoes various processes. It is presumed that the optical member can be easily peeled from the liquid crystal cell without damaging or contaminating the liquid crystal cell even after a long period of time elapses or when stored in a high temperature and high humidity state.

  Said optical member adhesive composition contains 0.1-3 weight part of said (meth) acrylic-type polymer (B) with respect to 100 weight part of said (meth) acrylic-type polymers (A). Is preferred.

  Moreover, in said adhesive composition for optical members, the said (meth) acrylic-type polymer (A) is an acrylic polymer obtained by emulsion polymerization using the reactive emulsifier containing a radically polymerizable functional group. Is preferred.

  On the other hand, the pressure-sensitive adhesive layer of the present invention is obtained by crosslinking the pressure-sensitive adhesive composition described above. According to the pressure-sensitive adhesive layer of the present invention, since the pressure-sensitive adhesive composition exhibiting the above-described effects is crosslinked, the pressure-sensitive adhesive layer is excellent in durability, removability, and stress relaxation properties. Therefore, it is particularly useful as a re-peelable pressure-sensitive adhesive layer.

  In addition, the pressure-sensitive adhesive sheet for optical members of the present invention is obtained by forming a pressure-sensitive adhesive layer produced by the above method on a support film. According to the pressure-sensitive adhesive sheet for optical members of the present invention, the pressure-sensitive adhesive sheet for optical members is excellent in durability, removability, and stress relaxation because it includes the pressure-sensitive adhesive layer having the above-described effects.

  Furthermore, the optical member with an adhesive of the present invention is characterized in that the above-mentioned adhesive layer for an optical member is formed on one side or both sides of the optical member. According to the optical member with an adhesive of the present invention, the optical member with an adhesive having excellent durability, removability, and stress relaxation properties is provided because the adhesive layer having the above-described effects is provided.

  Further, the image display device of the present invention is a liquid crystal display device, an organic EL display device, a PDP or the like using the optical member with an adhesive, and does not cause peeling or foaming even when stored in a high temperature and high humidity state. Even when the image display device is reused by peeling off the optical member due to durability, the adhesive force does not increase, and it has a function of easily peeling without adversely affecting the device.

  Hereinafter, embodiments of the present invention will be described in detail.

  The pressure-sensitive adhesive composition of the present invention contains 0.2 to 2% by weight of unsaturated carboxylic acid as a monomer unit, 100 parts by weight of (meth) acrylic polymer (A) obtained by emulsion polymerization, and unsaturated as a monomer unit. (Meth) acrylic polymer containing 1 to 7% by weight of carboxylic acid, having a carboxylic acid equivalent greater than that of the (meth) acrylic polymer (A), and having a weight average molecular weight in the range of 2000 to 50000 (B) 0.1 to 20 parts by weight and 0.01 to 1 part by weight of a silane coupling agent are contained.

  Examples of the (meth) acrylic polymer (A) include a homopolymer of (meth) acrylic acid alkyl ester, or a copolymer of this with another copolymerizable monomer.

  Examples of the (meth) acrylic acid alkyl ester used in the (meth) acrylic polymer (A) described above include (meth) acrylic monomers having an alkyl group having about 1 to 14 carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (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 , N-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate and the like, among which 2-ethylhexyl (meth) acrylate and the like are preferably used.

  The number of carbon atoms of the alkyl group of the (meth) acrylic alkyl ester is preferably about 1 to 14, more preferably 3 to 8, still more preferably 4 to 8. The larger the carbon number of the (meth) acrylic alkyl group, the better the effect of reducing adhesiveness at high speed peeling. On the other hand, when the number of carbon atoms exceeds 14, the pressure-sensitive adhesive layer becomes cloudy due to crystallization of the side chain, and the adhesiveness may be remarkably deteriorated.

  The (meth) acrylic polymer (A) used in the present invention contains 0.2 to 2% by weight, preferably 0.3 to 1.5% by weight of unsaturated carboxylic acid as a monomer unit. When the unsaturated carboxylic acid content is less than 0.2% by weight, the stress relaxation property tends to be lowered and the durability tends to be adversely affected. On the other hand, when the unsaturated carboxylic acid content exceeds 2% by weight, This is not preferable because the adhesive force to the liquid crystal cell tends to be too large.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Of these, acrylic acid and methacrylic acid are particularly preferably used.

  The polymerizable monomer other than the (meth) acrylic alkyl ester and the unsaturated carboxylic acid is a polymerizable monomer for adjusting the glass transition point or peelability of the (meth) acrylic polymer (A). It can be used as long as the effects of the present invention are not impaired.

  Examples of other polymerizable monomers used in the (meth) acrylic polymer (A) include aggregation of sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, and the like. Adhesive strength improvement and cross-linking of strength / heat resistance improving component, acid anhydride group-containing monomer, hydroxyl group-containing monomer, amide group-containing monomer, amino group-containing monomer, epoxy group-containing monomer, N-acryloylmorpholine, vinyl ether monomer, etc. A component having a functional group serving as a base point can be appropriately used. These monomer compounds may be used alone or in admixture of two or more.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth And acryloyloxynaphthalene sulfonic acid.

  Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloyl phosphate.

  Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethyl styrene, α-methyl styrene, and the like.

  Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl. (Meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-hydroxy (meth) acrylamide Vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like.

  Examples of the amide group-containing monomer include acrylamide and diethyl acrylamide.

  Examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N- (meth) acryloylmorpholine, and alkylaminoalkyl (meth) acrylate. Examples include esters.

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  In the present invention, other polymerizable monomers may be used alone or in admixture of two or more, but the total content is 100 parts by weight of the (meth) acrylic polymer. On the other hand, it is preferably 0 to 20 parts by weight, and more preferably 0.2 to 15 parts by weight.

  Furthermore, examples of copolymerizable monomers other than the above include silane monomers containing silicon atoms. Examples of the silane monomer include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, and 8-vinyloctyltrimethoxysilane. 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and the like.

  The silane monomer may be used alone, or two or more kinds may be mixed and used. However, the total content of the silane monomer is 0.1% relative to 100 parts by weight of the (meth) acrylic polymer. It is preferable that it is 1-3 weight part, and it is more preferable that it is 0.5-2 weight part. Copolymerization of a silane monomer is preferable for improving durability.

  The (meth) acrylic polymer (A) used in the present invention desirably has a weight average molecular weight of 500,000 or more, preferably 1,000,000 or more, and more preferably 1.8 million or more. When the weight average molecular weight is less than 500,000, the adhesive force tends to be generated due to the reduced cohesive force of the pressure-sensitive adhesive composition. A weight average molecular weight means what was obtained by measuring by GPC (gel permeation chromatography).

  In addition, the glass transition temperature (Tg) of the (meth) acrylic polymer (A) is 0 ° C. or lower (usually −100 ° C. or higher), preferably −10 ° C. or lower, because it is easy to balance the adhesive performance. Is desirable. When the glass transition temperature is higher than 0 ° C., the polymer is difficult to flow and the wetting to the polarizing plate is insufficient, and there is a tendency to cause blisters generated between the polarizing plate and the pressure-sensitive adhesive composition layer of the pressure-sensitive adhesive sheet. is there. The glass transition temperature (Tg) of the (meth) acrylic polymer (A) can be adjusted within the above range by appropriately changing the monomer component and composition ratio to be used.

  The polymerization method of the (meth) acrylic polymer (A) used in the present invention is limited to emulsion polymerization (emulsion polymerization). In addition, the obtained copolymer may be any of a random copolymer, a block copolymer, and the like.

  In the present invention, the polymerization initiator, the emulsifier and the like are not particularly limited and can be appropriately selected and used.

  Examples of the polymerization initiator used in the present invention include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- ( 5-methyl-2-imidazolin-2-yl) propane) dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) ), 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), azo initiators, potassium persulfate, ammonium persulfate Persulfate such as di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di sec-butyl peroxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1, 1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di (t- Hexylperoxy) peroxide initiators such as cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, peroxides such as a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate, Examples include redox initiators combined with reducing agents. The present invention is not limited to, et al.

  The polymerization initiator may be used alone or as a mixture of two or more, but the total content is 0.005 to 1 part by weight with respect to 100 parts by weight of the monomer. Is preferably about 0.02 to 0.5 parts by weight.

  In the present invention, a chain transfer agent may be used in the polymerization. By using a chain transfer agent, the molecular weight of the acrylic polymer can be appropriately adjusted.

  Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol.

  These chain transfer agents may be used alone or in admixture of two or more, but the total content is 0.01 to 0. 0 with respect to 100 parts by weight of the monomer. About 5 parts by weight.

  Examples of the emulsifier used in the present invention include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and polyoxyethylene. Nonionic emulsifiers such as alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene-polyoxypropylene block polymers, and the like can be mentioned. These emulsifiers may be used alone or in combination of two or more.

  Furthermore, as reactive emulsifiers, as emulsifiers into which radical polymerizable functional groups such as propenyl groups and allyl ether groups are introduced, specifically, for example, Aqualon HS-10, HS-20, KH-10, BC-05 BC-10, BC-20 (Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria Soap SE10N (Asahi Denka Kogyo Co., Ltd.) and the like. Reactive emulsifiers are preferable because they are incorporated into the polymer chain after polymerization and thus have improved water resistance. The amount of the emulsifier used is more preferably 0.3 to 5 parts by weight and 0.5 to 1 part by weight with respect to 100 parts by weight of the monomer in view of polymerization stability and mechanical stability.

  As an example of the polymerization operation, for example, the above-mentioned monomers and copolymerization monomers are first mixed, and after emulsifying and water are added thereto, the mixture is emulsified to prepare an emulsion. The monomer at this time may be blended in whole or in part with the total amount used, and the remainder may be dropped during the polymerization. Next, a polymerization initiator and, if necessary, water are added to this emulsion to carry out emulsion polymerization (emulsion polymerization).

  In addition, water may be blended only at the time of preparing the emulsion, or may be further blended thereafter, and can be appropriately selected according to the polymerization method described later. The amount of water is not particularly limited, but the solid content concentration of the acrylic polymer (A) after emulsion polymerization (emulsion polymerization) is 30 to 75% by weight, preferably 35 to 70% by weight. Prepare to be.

  The method of emulsion polymerization (emulsion polymerization) is not particularly limited, and can be appropriately selected from a batch polymerization method, a total amount dropping method, a two-stage polymerization method combining these, and the like.

  In the batch polymerization method, for example, a monomer mixture, an emulsifier, and water are charged into a reaction vessel and emulsified by stirring and mixing to prepare an emulsion, and then a polymerization initiator and water as necessary are added to the reaction vessel to perform emulsion polymerization ( Emulsion polymerization).

  In addition, in the total amount dropping method, first, a monomer mixture, an emulsifier and water are added and emulsified by stirring and mixing to prepare a dropping solution, and a polymerization initiator and water are charged into a reaction vessel, and then the dropping solution is added to the reaction vessel. It is dripped in and emulsion polymerization (emulsion polymerization) is carried out.

  As additives after emulsion polymerization, for example, known ones such as pH buffering agents, neutralizing agents, antifoaming agents and stabilizers can be appropriately used.

  The (meth) acrylic polymer (B) used in the present invention contains, as monomer units, 70% by weight or more of (meth) acrylic acid alkyl ester and 1 to 7% by weight of unsaturated carboxylic acid. The acrylic polymer (A) has a carboxylic acid equivalent larger than that of the carboxylic acid equivalent.

  As the (meth) acrylic acid alkyl ester used in the (meth) acrylic polymer (B) described above, known ones can be appropriately used without particular limitation. Among them, an alkyl group having about 1 to 4 carbon atoms can be used. The (meth) acrylic monomer is preferable from the viewpoint of hydrophilicity and flexibility. As the (meth) acrylic monomer having an alkyl group having about 1 to 4 carbon atoms, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, And isobutyl (meth) acrylate. The (meth) acrylic monomer having an alkyl group having 1 to 4 carbon atoms is preferably 50% by weight or more, and more preferably 60% by weight of the (meth) acrylic acid alkyl ester. These compounds may be used alone or in combination of two or more.

  The (meth) acrylic acid alkyl ester may be used alone or in combination of two or more, but the content of the polymer as a whole is 70% by weight or more, and 80 to 96 It is preferable that it is weight%. If the content is less than 70% by weight, the hydrophilicity of the (meth) acrylic polymer (B) may become poor, which is not preferable.

  The (meth) acrylic polymer (B) used in the present invention contains 1 to 7% by weight, preferably 2 to 6% by weight of unsaturated carboxylic acid as a monomer unit. When the unsaturated carboxylic acid content is less than 1% by weight, the stress relaxation property is lowered and the durability tends to be adversely affected. On the other hand, when the unsaturated carboxylic acid content exceeds 7% by weight, the liquid crystal Since the adhesive force to the cell tends to be too large, it is not preferable.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Of these, acrylic acid and methacrylic acid are particularly preferably used.

  As the (meth) acrylic polymer (B) used in the present invention, a polymer having a carboxylic acid equivalent larger than that of the (meth) acrylic polymer (A) is used. For example, it can be carried out by adjusting the content of the unsaturated carboxylic acid. When the carboxylic acid equivalent of the (meth) acrylic polymer (B) is smaller than the carboxylic acid equivalent of the (meth) acrylic polymer (A), the adhesive force to the liquid crystal cell tends to be too large, which is not preferable.

  The polymerizable monomer other than the (meth) acrylic alkyl ester and the unsaturated carboxylic acid is a polymerizable monomer for adjusting the glass transition point or peelability of the (meth) acrylic polymer (B). It can be used as long as the effects of the present invention are not impaired.

  Examples of other polymerizable monomers used in the (meth) acrylic polymer (B) include aggregation of sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, and the like. Adhesive strength improvement and cross-linking of strength / heat resistance improving component, acid anhydride group-containing monomer, hydroxyl group-containing monomer, amide group-containing monomer, amino group-containing monomer, epoxy group-containing monomer, N-acryloylmorpholine, vinyl ether monomer, etc. A component having a functional group serving as a base point can be appropriately used. These monomer compounds may be used alone or in admixture of two or more.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth And acryloyloxynaphthalene sulfonic acid.

  Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloyl phosphate.

  Examples of the cyano group-containing monomer include acrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethyl styrene, α-methyl styrene, and the like.

  Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl. (Meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-hydroxy (meth) acrylamide Vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like.

  Examples of the amide group-containing monomer include acrylamide and diethyl acrylamide.

  Examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N- (meth) acryloylmorpholine, and alkylaminoalkyl (meth) acrylate. Examples include esters.

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  In the present invention, other polymerizable monomers may be used alone or in admixture of two or more, but the total content is 100 parts by weight of the (meth) acrylic polymer. On the other hand, it is preferable that it is 0-30 weight part, and it is more preferable that it is 0-15 weight part.

  For the (meth) acrylic polymer (B) used in the present invention, a (meth) acrylic polymer having a weight average molecular weight in the range of 2000 to 50000 is used. More preferably. When the weight average molecular weight is less than 2000, the durability tends to decrease. On the other hand, when the weight average molecular weight exceeds 50000, the adhesive force to the liquid crystal cell tends to increase. A weight average molecular weight means what was obtained by measuring by GPC (gel permeation chromatography).

  In addition, the glass transition temperature (Tg) of the (meth) acrylic polymer (B) is 0 ° C. or lower (usually −100 ° C. or higher), preferably −10 ° C. or lower because the adhesive performance is easily balanced. Is desirable. When the glass transition temperature is higher than 0 ° C., the polymer is difficult to flow and the wetting to the polarizing plate is insufficient, and there is a tendency to cause blisters generated between the polarizing plate and the pressure-sensitive adhesive composition layer of the pressure-sensitive adhesive sheet. is there. In addition, the glass transition temperature (Tg) of a (meth) acrylic-type polymer (B) can be adjusted in the said range by changing the monomer component and composition ratio to be used suitably.

  The polymerization method of the (meth) acrylic polymer (B) used in the present invention is not particularly limited, and can be polymerized by a known method such as solution polymerization, emulsion polymerization (emulsion polymerization), bulk polymerization, suspension polymerization or the like. However, in consideration of environmental measures, it is preferable to use a method that does not use an organic solvent. The weight average molecular weight may be adjusted by using a large amount of polymerization initiator or a chain transfer agent such as mercaptan. In addition, the obtained copolymer may be any of a random copolymer, a block copolymer, and the like.

  In the present invention, the polymerization initiator, the emulsifier and the like are not particularly limited, and known ones can be appropriately selected and used.

  A well-known thing can be suitably used for the silane coupling agent used for this invention without a restriction | limiting in particular. For example, epoxy such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Group-containing silane coupling agent, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propyl Amino group-containing silane coupling agents such as amines, (meth) acryl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane, and 3-isocyanatopropyltriethoxysilane Insiane Such as preparative group-containing silane coupling agent. Use of such a silane coupling agent is preferable for improving durability.

  The silane coupling agent may be used alone or in combination of two or more, but the total content is based on 100 parts by weight of the monomer mixture of the (meth) acrylic polymer. The content is preferably 0.01 to 1 part by weight, and more preferably 0.03 to 0.5 part by weight. When the amount is less than 0.01 part by weight, it is difficult to improve the durability. On the other hand, when the amount exceeds 1 part by weight, the adhesion to the liquid crystal cell tends to increase and the removability is poor.

  The pressure-sensitive adhesive composition of the present invention has the above (meth) acrylic polymer as a base polymer.

  The pressure-sensitive adhesive composition of the present invention is more excellent in heat resistance by appropriately crosslinking a (meth) acrylic polymer. Examples of the crosslinking agent used in the present invention include a blocked isocyanate compound having a protective group, an epoxy compound, an oxazoline compound, a melamine resin, an aziridine derivative, and a metal chelate compound. Among these, an epoxy compound is particularly preferably used mainly from the viewpoint of obtaining an appropriate cohesive force. These compounds may be used alone or in combination. In addition, it is difficult to use a normal isocyanate compound due to stability problems in water.

  Examples of the blocked isocyanate compound with a protecting group include Elastolon BN-4 (Daiichi Kogyo Seiyaku Co., Ltd.), Takenate WB-700 (Mitsui Takeda Chemical Co., Ltd.) and the like. These compounds may be used alone or in combination.

  Examples of the oxazoline compound include 2-oxazoline, 3-oxazoline, 4-oxazoline, 5-keto-3-oxazoline, and Epocros (manufactured by Nippon Shokubai Co., Ltd.). These compounds may be used alone or in combination.

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

  Examples of the melamine resin include hexamethylol melamine. Examples of the aziridine derivative include a commercially available product name HDU (manufactured by Mutual Pharmaceutical Company), a product name TAZM (manufactured by Mutual Pharmaceutical Company), and a product name TAZO (manufactured by Mutual Pharmaceutical Company). These compounds may be used alone or in combination.

  Examples of the metal chelate compound include aluminum, iron, tin, titanium, and nickel as metal components, and acetylene, methyl acetoacetate, and ethyl lactate as chelate components. These compounds may be used alone or in combination.

  The content of the crosslinking agent used in the present invention is usually about 0.01 to 5 weights with respect to 100 parts by weight of the (meth) acrylic polymer.

The gel fraction of the pressure-sensitive adhesive composition in the present invention means the weight W ₂ after drying the pressure-sensitive adhesive layer after immersing the dry weight W ₁ (g) of the pressure-sensitive adhesive layer in ethyl acetate, and drying the pressure-sensitive adhesive layer from ethyl acetate. (G) is measured, and is a value calculated as (W ₂ / W ₁ ) × 100 (% by weight).

More specifically, a solution of a pressure-sensitive adhesive composition to a release-treated on the film was applied and dried for 5 minutes at 110 ° C., then after 24 hours aging treatment at 50 ° C., the resulting pressure-sensitive adhesive layer W ₁ (G) (about 500 mg) was collected. Next, the pressure-sensitive adhesive layer was immersed in ethyl acetate at about 23 ° C. for 7 days, and then the pressure-sensitive adhesive layer was taken out and dried at 130 ° C. for 2 hours. W ₂ (g) of the obtained pressure-sensitive adhesive layer (About 500 mg) was measured. The gel fraction (% by weight) was determined by applying W ₁ and W ₂ to the above formula.

  Furthermore, the pressure-sensitive adhesive composition of the present invention may contain other known additives, such as powders such as colorants and pigments, dyes, surfactants, plasticizers, tackifiers, Use surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, foils, etc. It can be added appropriately depending on the application.

  On the other hand, the pressure-sensitive adhesive layer of the present invention is obtained by crosslinking the pressure-sensitive adhesive composition as described above. The pressure-sensitive adhesive sheets of the present invention are formed by forming such a pressure-sensitive adhesive layer on a support film. At that time, the pressure-sensitive adhesive composition is generally crosslinked after application of the pressure-sensitive adhesive composition, but the pressure-sensitive adhesive layer comprising the crosslinked pressure-sensitive adhesive composition can be transferred to a support film or the like. is there.

  The method for forming the pressure-sensitive adhesive layer on the film is not particularly limited. For example, the pressure-sensitive adhesive composition is applied to a release-treated support film, and the polymerization solvent is dried and removed to form the pressure-sensitive adhesive layer on the optical member. It is produced by a method or a method in which the pressure-sensitive adhesive composition is applied onto an optical member, a polymerization solvent or the like is removed by drying, and a pressure-sensitive adhesive layer is formed on the optical member. Thereafter, curing may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction. Further, when the pressure-sensitive adhesive composition is coated on a support film or the like to produce a pressure-sensitive adhesive sheet, one or more solvents other than the polymerization solvent are added to the composition so that the pressure-sensitive adhesive composition can be uniformly coated on the support film or the like. You may add a new one.

  Moreover, as a formation method of the adhesive layer of this invention, the well-known method used for manufacture of adhesive sheets is used. Specific examples include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, and the like.

  The pressure-sensitive adhesive layer is prepared to have a thickness of 2 to 500 μm, preferably about 5 to 100 μm.

  In addition, the pressure-sensitive adhesive sheet for optical members of the present invention is obtained by forming a pressure-sensitive adhesive layer produced by the above method on a support film.

  Examples of the constituent material of the support film used in the present invention include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foamed sheets, metal foils, and the like. Appropriate thin-leaf bodies such as laminates are available.

  The thickness of the support film which comprises the adhesive sheets in this invention is 5-200 micrometers normally, Preferably it is about 10-100 micrometers.

  For the support film, if necessary, mold release and antifouling treatment with a silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., acid treatment, alkali treatment, primer treatment Further, anti-adhesion treatment such as corona treatment, plasma treatment and ultraviolet treatment, coating type, kneading type, vapor deposition type and the like can be carried out.

  The support film is preferably a plastic substrate having heat resistance and solvent resistance and flexibility. When the support film has flexibility, the pressure-sensitive adhesive composition can be applied by a roll coater or the like, and can be wound into a roll.

  The plastic substrate is not particularly limited as long as it can be formed into a sheet shape or a film shape. For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene・ Polypropylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, polyolefin film such as ethylene / vinyl alcohol copolymer, polyethylene terephthalate, polyethylene naphthalate, Polyester film such as polybutylene terephthalate, polyacrylate film, polystyrene film, nylon 6, nylon 6,6, polyamide film such as partially aromatic polyamide, polyvinyl chloride film, polyvinylidene chloride film, polymer film Carbonate film, polyfluoroethylene film, a polyimide film, such as polyvinyl alcohol film.

  The pressure-sensitive adhesive sheets of the present invention can be bonded with a separator (release sheet) on the pressure-sensitive adhesive surface for the purpose of protecting the pressure-sensitive adhesive surface, if necessary. As a constituent material of the separator (release sheet), for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and laminates thereof An appropriate thin leaf body such as a body is exemplified, and a plastic film is preferably used from the viewpoint of excellent surface smoothness. The film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer. Examples thereof include a coalesced film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

  The thickness of the separator (release sheet) is usually about 5 to 200 μm, preferably about 5 to 100 μm. For the separator (release sheet), if necessary, release agent and antifouling treatment with silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., coating type, kneading An antistatic treatment such as a mold or a vapor deposition mold can also be performed. In particular, the release property from the pressure-sensitive adhesive layer can be further improved by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment on the surface of the separator (release sheet).

  The optical member with pressure-sensitive adhesive of the present invention is formed by forming the above-mentioned pressure-sensitive adhesive layer for optical members on one side or both sides of the optical member.

  As the optical member, those used for forming an image display device such as a liquid crystal display device are used, and the type thereof is not particularly limited. For example, the optical member includes a polarizing plate. As the polarizing plate, one having a transparent protective film on one side or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride and the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed with dyeing after iodine. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a non-substituted phenyl and a thermoplastic resin having a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  Hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of light transmitted through the polarizing plate. For example, a roughening method using a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include a conductive material made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle diameter of 0.5 to 50 μm. Transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, etc. may be used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  The optical member of the present invention includes, for example, a liquid crystal display device such as a reflecting plate, a semi-transmissive plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), a viewing angle compensation film, and a brightness enhancement film. What becomes an optical layer which may be used for formation of this is mention | raise | lifted. These can be used alone as the optical member of the present invention, and can be used by laminating the polarizing plate for practical use, or one or more layers.

  In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate is further laminated with a reflecting plate or a semi-transmissive reflecting plate, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is further laminated on a polarizing plate, a polarizing plate A wide viewing angle polarizing plate in which a viewing angle compensation film is further laminated on a plate, or a polarizing plate in which a brightness enhancement film is further laminated on a polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer having a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film can be formed by, for example, depositing a metal by an appropriate method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the transparent protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and also has an antireflection function.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymer, norbornene resin, or binary, ternary copolymer, graft copolymer Examples thereof include polymers and blends. These polymer materials become oriented products (stretched films) by stretching or the like.

  Examples of the liquid crystalline polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. It is done. Specific examples of main-chain liquid crystalline polymers include nematic-oriented polyester-based liquid crystalline polymers, discotic polymers, and cholesteric polymers that have a structure in which a mesogenic group is bonded to a spacer portion that imparts flexibility. It is done. Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers are prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment surface such as those obtained by rubbing the surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or by obliquely depositing silicon oxide. This is done by developing and heat treatment.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for coloring or viewing angle due to birefringence of various wavelength plates and liquid crystal layers, for example. In this case, the retardation plate may be laminated to control optical characteristics such as retardation.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical member such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a phase difference plate, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and contracting the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Is mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light having a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident by a backlight of a liquid crystal display device or the like or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  As the brightness enhancement film, for example, a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy, such as a characteristic that transmits linearly polarized light having a predetermined polarization axis and reflects other light. Such as a cholesteric liquid crystal polymer alignment film or a film substrate whose alignment liquid crystal layer is supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate ones such as those shown can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate as it is with the polarization axis aligned, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that emits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but the circularly polarized light is converted into linearly polarized light through a retardation plate in order to suppress absorption loss. It is preferably incident on the polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region has, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. The phase difference layer shown, for example, the phase difference layer which functions as a half-wave plate, etc. can be obtained by the method of superimposing. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  The optical member in which the optical layer is laminated on the polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device and the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as a pressure-sensitive adhesive layer can be used. When adhering the polarizing plate and the other optical layer, their optical axes can be set at an appropriate arrangement angle in accordance with the target phase difference characteristic.

  In addition, in each layer such as an optical member and an adhesive layer of the adhesive optical member of the present invention, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc. What gave the ultraviolet absorptivity by systems, such as a system processed with a ultraviolet absorber, etc. may be used.

  The pressure-sensitive adhesive optical member of the present invention can be preferably used for forming various image display devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. In other words, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an adhesive optical member, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the optical member by invention, It can apply to the former. As the liquid crystal cell, for example, an arbitrary type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive optical member is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical member by this invention can be installed in the one side or both sides of a liquid crystal cell. When optical members are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer of appropriate parts such as a diffuser plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffuser plate, and a backlight at an appropriate position. Alternatively, two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. In general, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Or a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer. Are known.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described, but the present invention is not limited to these. In addition, the evaluation item in an Example etc. measured as follows.

<Measurement of weight average molecular weight of (meth) acrylic polymer>
The weight average molecular weight of the produced polymer was measured by GPC (gel permeation chromatography). In addition, about (meth) acrylic-type polymer (A), although molecular weight was not able to be measured large, it is estimated that it is about 3 million or more.

Apparatus: Tosoh Corporation, HLC-8120GPC
column:
Sample column; manufactured by Tosoh Corporation, GMH _HR -H + GMH _HR -H + G2000H _HR
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
Flow rate: 0.8ml / min
Injection volume: 100 μl
Column temperature: 40 ° C
Eluent: THF
Injection sample concentration: 0.1% by weight
Detector: differential refractometer The weight average molecular weight was calculated in terms of polystyrene.

<Measurement of adhesive strength>
Each of the prepared optical members with pressure-sensitive adhesive for evaluation was cut into a size of 25 mm in width and pressure-bonded to a non-alkali glass plate (Corning Corp., 1737, thickness: 1 mm) to obtain a sample for evaluating adhesive force (crimping conditions) : Roller of 2 kg in weight, speed 5 m / min, one reciprocating process).

  This evaluation sample was treated in an autoclave at 50 ° C. × 0.5 MPa for 30 minutes, then treated in an environment of 23 ° C. × 50% RH for 3 hours, and then peeled off at a peel angle of 90 ° with a universal tensile tester. The adhesive strength (initial adhesive strength: N / 25 mm, peeling speed: 300 mm / min) was measured.

  Furthermore, after the autoclave treatment, the treatment was performed at 60 ° C. for 20 hours, and then the treatment was performed for 3 hours in an environment of 23 ° C. × 50 RH. : N / 25 mm, peeling speed: 300 mm / min). In addition, it is desired that the process adhesive force after the heat treatment does not increase with the initial adhesive force.

<Evaluation of occurrence of adhesive residue>
The pressure-sensitive adhesive optical member after the autoclave treatment was further treated at 90 ° C. for 300 hours, then treated in an environment of 23 ° C. × 50% RH for 3 hours, and then peeled off at 90 ° by a universal tensile tester. The state of contamination on the surface of the stainless steel plate was observed with the naked eye at the time of peeling (peeling speed: 300 mm / min). The evaluation criteria are as follows.

When no glue residue is found: ○
When adhesive residue is observed: ×

<Durability evaluation>
The produced optical member with a pressure-sensitive adhesive was cut into a size of 26 cm wide × 20 cm long and pressure-bonded to a non-alkali glass plate (Corning Corp., 1737, thickness: 0.7 mm) with a laminator to obtain a sample for evaluation.

  This evaluation sample was treated in an autoclave at 50 ° C. × 0.5 MPa for 30 minutes and then treated in an environment of 60 ° C. × 90% RH for 500 hours, and then the state of the evaluation sample was visually observed. The evaluation criteria are as follows.

When the optical member is not peeled off or lifted: ○
When peeling or lifting of the optical member is recognized: ×

<Evaluation of occurrence of color unevenness>
The produced optical member with pressure-sensitive adhesive is cut into a size of 26 cm wide × 20 cm long so that the absorption axis of the polarizing plate is perpendicular to both surfaces of a non-alkali glass plate (Corning Corp., 1737, thickness: 0.7 mm). A sample for evaluation was prepared by pressure bonding with a laminator.

  This evaluation sample was treated in an autoclave of 50 ° C. × 0.5 MPa for 30 minutes and then treated at 90 ° C. for 500 hours, and then the state of the evaluation sample was visually observed. The evaluation criteria are as follows.

If no color unevenness is found: ○
When color unevenness is observed: ×

[Example 1]
(Preparation of acrylic polymer (A1))
In a homomixer, 80 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of butyl acrylate, 1 part by weight of acrylic acid, 0.10 parts by weight of 3-acryloxypropyltriethoxysilane, Aqualon HS-20 as a reactive emulsifier (Daiichi Kogyo) An emulsion was prepared by charging 2.0 parts by weight (manufactured by Pharmaceutical Co., Ltd.) and 25 parts by weight of ion exchange water and emulsifying them.

Next, a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, a cooler, and a dropping funnel was purged with nitrogen for 1 hour, and then 30 parts by weight of water and 2,2′- as a polymerization initiator were added to the flask. Add 0.10 parts by weight of azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), and add the emulsion obtained above to the system. Was dropped over 5 hours while maintaining the temperature at 60 ° C. to cause a polymerization reaction. After completion of the polymerization reaction, the pH was adjusted to 8 by adding ammonia to obtain an acrylic polymer (A1) solution. The carboxylic acid equivalent of the acrylic polymer (A1) was 1.37 × 10 ⁻⁴ equivalent / g.

(Preparation of acrylic polymer (B1))
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 80 parts by weight of butyl acrylate, 15 parts by weight of 2-ethylhexyl acrylate, 5.0 parts by weight of acrylic acid, 0.80 weight by weight of lauryl mercaptan Part, 2,2'-azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) 0.10 parts by weight as a polymerization initiator was added, and after sufficient nitrogen substitution, the inside of the system was around 58 ° C under a nitrogen stream The polymerization reaction was carried out for 10 hours while stirring and an acrylic polymer (B1) was obtained. The acrylic polymer (B1) had a carboxylic acid equivalent of 6.89 × 10 ⁻⁴ equivalent / g and a weight average molecular weight of 2.9 × 10 ⁴ .

(Preparation of pressure-sensitive adhesive composition for optical members)
With respect to 100 parts by weight (solid content) of the acrylic polymer (A1) solution, 0.50 part by weight of the acrylic polymer (B1) and 0.20 weight by weight of 3-crisidoxypropyltrimethoxysilane as a silane coupling agent Parts were added, and these were uniformly mixed to prepare an adhesive composition for an optical member.

(Preparation of optical member with adhesive for evaluation)
The pressure-sensitive adhesive composition solution is applied onto a polyethylene terephthalate (PET) film (Toray Industries, Inc., thickness: 38 μm) subjected to silicone release treatment, and dried at 110 ° C. for 5 minutes to remove the solvent and remove the pressure-sensitive adhesive layer ( The thickness after drying was 25 μm). The gel fraction was 76%. The said adhesive layer was transcribe | transferred to the polarizing plate and the optical member with an adhesive for evaluation was produced.

[Example 2]
The pressure-sensitive adhesive composition for optical members was prepared in the same manner as in Example 1, except that 5.0 parts by weight of the acrylic polymer (B1) was used instead of 0.50 parts by weight of the acrylic polymer (B1). Prepared.

  Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 72%.

Example 3
A pressure-sensitive adhesive composition for an optical member was prepared in the same manner as in Example 1 except that 15 parts by weight of the acrylic polymer (B1) was used instead of 0.50 part by weight of the acrylic polymer (B1). .

  Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 67%.

Example 4
(Preparation of acrylic polymer (A2))
To a homomixer, 90 parts by weight of 2-ethylhexyl acrylate, 8.0 parts by weight of butyl acrylate, 2 parts by weight of acrylonitrile, 0.5 parts by weight of acrylic acid, 0.10 parts by weight of 2-hydroxyethyl acrylate, 3-acryloxypropyltri An emulsion was prepared by charging 0.10 parts by weight of ethoxysilane, 2.0 parts by weight of Aqualon HS-20 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive emulsifier, and 25 parts by weight of ion-exchanged water, and emulsifying them. .

Next, a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, a cooler, and a dropping funnel was purged with nitrogen for 1 hour, and then 30 parts by weight of ion-exchanged water and 2,2 as a polymerization initiator were added to the flask. '-Azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057) was added in an amount of 0.10 parts by weight, and the emulsion obtained above was While maintaining the inside of the system at 60 ° C., it was dropped over 5 hours to cause a polymerization reaction. After completion of the polymerization reaction, the pH was adjusted to 8 by adding ammonia to obtain an acrylic polymer (A2) solution. The carboxylic acid equivalent of the acrylic polymer (A2) was 0.69 × 10 ⁻⁴ equivalent / g.

(Preparation of acrylic polymer (B2))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 100 parts by weight of butyl acrylate, 5.0 parts by weight of acrylic acid, 1.0 part by weight of lauryl mercaptan, 2, as a polymerization initiator After adding 0.10 parts by weight of 2′-azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) and sufficiently purging with nitrogen, the system was polymerized for 12 hours while stirring and maintaining the system at around 55 ° C. under a nitrogen stream. Reaction was performed to obtain an acrylic polymer (B2) solution. The acrylic polymer (B2) had a carboxylic acid equivalent of 6.55 × 10 ⁻⁴ equivalent / g and a weight average molecular weight of 3.5 × 10 ⁴ .

(Preparation of pressure-sensitive adhesive composition for optical members)
With respect to 100 parts by weight (solid content) of the acrylic polymer (A2) solution, 1.0 part by weight of the acrylic polymer (B2) and 0.20 weight of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent Parts were added, and these were uniformly mixed to prepare an adhesive composition for an optical member.

(Preparation of optical member with adhesive for evaluation)
The pressure-sensitive adhesive composition solution is applied onto a polyethylene terephthalate (PET) film (Toray Industries, Inc., thickness: 38 μm) subjected to silicone release treatment, and dried at 110 ° C. for 5 minutes to remove the solvent and remove the pressure-sensitive adhesive layer ( The thickness after drying was 25 μm). The gel fraction was 75%. The said adhesive layer was transcribe | transferred to the polarizing plate and the optical member with an adhesive for evaluation was produced.

Example 5
A pressure-sensitive adhesive composition for an optical member was prepared in the same manner as in Example 4 except that 15 parts by weight of the acrylic polymer (B2) was used instead of 1.0 part by weight of the acrylic polymer (B2). .

  Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 65%.

[Comparative Example 1]
An adhesive composition for an optical member was prepared by the same method as in Example 1 except that the acrylic polymer (B1) was not used, and then an adhesive layer and an optical member with an adhesive for evaluation were prepared. . The gel fraction of the pressure-sensitive adhesive layer was 60%.

[Comparative Example 2]
A pressure-sensitive adhesive composition for an optical member was prepared in the same manner as in Example 1 except that 30 parts by weight of the acrylic polymer (B1) was used instead of 0.50 part by weight of the acrylic polymer (B1). .

  Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 60%.

[Comparative Example 3]
A pressure-sensitive adhesive composition for an optical member was prepared in the same manner as in Example 1 except that the above-mentioned 3-crisidoxypropyltrimethoxysilane, which was a silane coupling agent, was not used. An optical member with a pressure-sensitive adhesive was prepared. The gel fraction of the pressure-sensitive adhesive layer was 75%.

[Comparative Example 4]
An optical member was produced in the same manner as in Example 1 except that 3.0 parts by weight of 3-crisidoxypropyltrimethoxysilane was used instead of 0.20 parts by weight of 3-crisidoxypropyltrimethoxysilane. A pressure-sensitive adhesive composition was prepared.

  Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 75%.

[Comparative Example 5]
(Preparation of acrylic polymer (A3))
An acrylic polymer (A3) solution was obtained in the same manner as in Example 4 except that 5.0 parts by weight of acrylic acid was used instead of 0.50 parts by weight of acrylic acid. The carboxylic acid equivalent of the acrylic polymer (A3) was 6.61 × 10 ⁻⁴ equivalent / g.

(Preparation of pressure-sensitive adhesive composition for optical members)
An optical member was prepared in the same manner as in Example 4 except that 100 parts by weight (solid content) of the acrylic polymer (A3) solution was used instead of 100 parts by weight (solid content) of the acrylic polymer (A2) solution. A pressure-sensitive adhesive composition was prepared.

(Preparation of optical member with adhesive for evaluation)
Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 80%.

[Comparative Example 6]
(Preparation of acrylic polymer (B3))
An acrylic polymer (B3) was obtained in the same manner as in Example 1 except that 1.0 part by weight of the acrylic acid was used instead of 5.0 parts by weight of the acrylic acid. The acrylic polymer (B 3) a carboxylic acid equivalent of 1.45 × ^{10 -4} eq / g, a weight average molecular weight was 8.5 × 10 ^5.

(Preparation of pressure-sensitive adhesive composition for optical members)
The pressure-sensitive adhesive composition for optical members was prepared in the same manner as in Example 1 except that 0.50 part by weight of the acrylic polymer (B3) was used instead of 0.50 part by weight of the acrylic polymer (B1). Prepared.

(Preparation of optical member with adhesive for evaluation)
Moreover, except having used the said adhesive composition for optical members, the adhesive layer and the optical member with an adhesive for evaluation were produced by the method similar to Example 1. FIG. The gel fraction of the pressure-sensitive adhesive layer was 72%.

  In accordance with the above methods, adhesive strength measurement, generation of adhesive residue, durability, and generation of color unevenness were evaluated. The obtained results are shown in Table 1.

上記表１の結果より、本発明によって作製された粘着剤付光学部材を用いた場合（実施例１〜５）、いずれの実施例においても、初期接着力と６０℃処理後の接着力との差が小さく、また６Ｎ／２５ｍｍ以下の小さな値に抑えられているため、液晶セルに貼り付けた際の接着力の増加がないことがわかる。したがって、通常の処理条件下においては、再剥離性がよく、糊残りや液晶セルを破損等することなく光学部材を再剥離して液晶セルを再利用することが容易となる。また、いずれの実施例においても、９０℃保存した際の接着力が小さく１０Ｎ／２５ｍｍ以下に抑えられているため、廃棄時などの長期間貼り付け後でも接着力が小さく、ガラス部と光学部材を分別するのが容易となることがわかる。さらに、いずれの実施例においても、長期の過酷試験に対しても良好な耐久性を有し、光学部材（偏光板）の寸法変化に起因する応力に対する緩和性にも優れており、液晶表示状態への悪影響（色ムラ）もない。

From the results of Table 1 above, when using the optical member with pressure-sensitive adhesive prepared according to the present invention (Examples 1 to 5), in any of the examples, the initial adhesive force and the adhesive force after 60 ° C. treatment Since the difference is small and the value is suppressed to a small value of 6 N / 25 mm or less, it can be seen that there is no increase in adhesive strength when it is attached to the liquid crystal cell. Therefore, the removability is good under normal processing conditions, and it becomes easy to reuse the liquid crystal cell by re-peeling the optical member without damaging the adhesive residue or the liquid crystal cell. In any of the examples, since the adhesive strength when stored at 90 ° C. is small and is suppressed to 10 N / 25 mm or less, the adhesive strength is small even after pasting for a long time such as disposal, and the glass portion and the optical member It can be seen that it becomes easy to separate the. Furthermore, in any of the examples, it has good durability against a long-term severe test, and has excellent relaxation properties against stress caused by the dimensional change of the optical member (polarizing plate). There is no negative effect (color unevenness).

  On the other hand, in any of Comparative Examples 1 to 6, the adhesive strength when stored at 90 ° C. is small and larger than 10 N / 25 mm, and all of the suppression of the occurrence of adhesive residue, the durability, and the suppression of the occurrence of color unevenness. It was difficult to line up in a balanced manner. Therefore, it was revealed that the comparative examples were inferior to the re-peelable pressure-sensitive adhesive composition for optical members of the pressure-sensitive adhesive sheets.

Therefore, the pressure-sensitive adhesive composition of the present invention is an acrylic pressure-sensitive adhesive that can be applied in water as an environmental measure, and is a pressure-sensitive adhesive composition for optical members that is excellent in durability, removability, and stress relaxation properties. I was able to confirm.

Claims (6)

100 parts by weight of (meth) acrylic polymer (A) obtained by emulsion polymerization , containing 0.3 to 1.5 % by weight of unsaturated carboxylic acid as a monomer unit,
It contains 2 to 6 % by weight of unsaturated carboxylic acid as a monomer unit, has a carboxylic acid equivalent larger than that of the (meth) acrylic polymer (A), and has a weight average molecular weight in the range of 2000 to 50000. (Meth) acrylic polymer (B) 0.1-3 parts by weight, and
A pressure-sensitive adhesive composition for an optical member, comprising 0.01 to 1 part by weight of a silane coupling agent. The pressure-sensitive adhesive composition for an optical member according to claim 1, wherein the (meth) acrylic polymer (A) is an acrylic polymer obtained by emulsion polymerization using a reactive emulsifier containing a radical polymerizable functional group. The adhesive layer for optical members formed by bridge | crosslinking the adhesive composition for optical members in any one of Claim 1 or 2. The adhesive sheet for optical members formed by forming the adhesive layer formed by bridge | crosslinking the adhesive composition for optical members in any one of Claim 1 or 2 on a support film. An optical member with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer for an optical member according to claim 3 is formed on one side or both sides of the optical member. An image display device using at least one optical member with an adhesive layer according to claim 5.