JP5243197B2 - Optical member pressure-sensitive adhesive composition, optical member pressure-sensitive adhesive layer, pressure-sensitive adhesive optical member, and image display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition for optical members. Moreover, this invention relates to the adhesive layer for optical members formed with the said adhesive composition for optical members. Furthermore, the present invention relates to an adhesive optical member having the adhesive layer, and further to an image display device such as a liquid crystal display device, an organic EL display device, and a PDP using the adhesive optical member. Examples of the optical member include a polarizing plate, a retardation plate, an optical compensation film, a brightness enhancement film, and those in which these are laminated.

  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.

  In addition, when an optical member is stuck, if the foreign material bites into the bonding surface or the bonding position is misplaced, the optical member is removed from the liquid crystal cell and 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 inferior, and it is very difficult to achieve both durability and removability.

  On the other hand, if the stress due to the dimensional change rate of an optical member such as a polarizing plate under heating conditions or humidification conditions cannot be alleviated uniformly, residual stress remains on the optical member such as the polarizing plate, resulting in uneven color and white spots. There are cases where adverse effects such as

  Various materials have been proposed as pressure-sensitive adhesives used for such optical members. In addition, a high molecular weight polymer is blended with a low molecular weight polymer to improve the stress relaxation property of the pressure-sensitive adhesive.

  For example, an adhesive in which 20 to 200 parts by weight of a low molecular weight polymer having a weight average molecular weight of 30,000 or less is blended with 100 parts by weight of a high molecular weight polymer having a high functional group ratio has been proposed, and the adhesive has a cross-linked structure. By forming a three-dimensional structure with high molecular weight components, foaming and peeling at high temperature and high humidity are prevented, and internal stress associated with dimensional changes of the polarizing plate is absorbed by the low molecular weight polymer components to suppress color unevenness. It is disclosed that it can do (patent document 1). In addition, an adhesive in which 5 to 100 parts by weight of an acrylic oligomer having a weight average molecular weight of 1000 to 10000 and a bifunctional crosslinking agent is blended with 100 parts by weight of a high molecular weight polymer has been proposed. It is disclosed that it has excellent adhesion to the body and has good stress relaxation properties and no white spots (Patent Document 2). Further, a pressure-sensitive adhesive in which 10 to 100 parts by weight of a low molecular weight polymer having a glass transition point of 0 to −80 ° C. and a weight average molecular weight of 30,000 to 100,000 and a polyfunctional compound is added to 100 parts by weight of a high molecular weight polymer has been proposed. In addition, according to the pressure-sensitive adhesive, it is disclosed that it can cope with peeling, foaming, white spotting phenomenon, and is excellent in removability (Patent Document 3). In addition, the pressure-sensitive adhesive containing 10 to 50% of a low molecular weight polymer of 5 to 500,000 in a high molecular weight polymer of 1 to 1.5 million has no white spots or peripheral unevenness (white spots around the panel in a liquid crystal panel). (Patent Document 4). Further, it is disclosed that an adhesive in which 10 to 100 parts by weight of a polymer having a weight average molecular weight of less than 800,000 is blended with 100 parts by weight of a polymer having a weight average molecular weight of 800,000 or more exhibits an excellent effect on white spots ( Patent Document 5).

  On the other hand, a pressure-sensitive adhesive containing a component having a positive elastic modulus has been proposed with a different idea from the above, for example, in order to suppress peripheral unevenness (Patent Document 6). Moreover, it has been proposed that a diffusion function can be imparted to the pressure-sensitive adhesive with the same blending components as in Patent Document 6 (Patent Document 7). It has also been proposed to use an adhesive layer in which the absolute value of the photoelastic coefficient is controlled within a predetermined range (Patent Document 8). Further, it is disclosed that an adhesive using a copolymer obtained by copolymerizing a monomer having positive intrinsic birefringence as a base polymer or an adhesive containing a crosslinking agent having positive intrinsic birefringence can suppress peripheral unevenness. (Patent Documents 9 and 10). Moreover, it is disclosed that a retardation can be expressed by stretching a transparent adhesive (Patent Document 11).

JP-A-10-279907 JP 2001-335767 A JP 2002-121521 A JP 2006-77224 A JP 2006-282687 A JP-T-2004-516359 Japanese Patent Laid-Open No. 11-326637 JP 2006-259664 A JP 2008-144125 A JP 2008-144126 A JP 2006-47494 A

  In the pressure sensitive adhesives of Patent Documents 1 to 5 blended with low molecular weight components, the internal stress is absorbed by the low molecular weight components to disperse the stress throughout the pressure sensitive adhesive, thereby suppressing peripheral unevenness. Insufficient to suppress the contrast, the overall contrast may be lowered. There is also a problem that removability and durability are lowered.

  On the other hand, in order to suppress peripheral unevenness as in Patent Document 6, the pressure-sensitive adhesive may become cloudy because the composition range of the pressure-sensitive adhesive is limited for the pressure-sensitive adhesive containing a component having a positive elastic modulus. In many cases, there is a problem that the contrast is lowered by the diffusion function as described in Patent Document 7.

  Moreover, about the adhesive which prescribed | regulated the absolute value of the photoelastic coefficient like patent documents 8-10, since the monomer component with low adhesiveness was copolymerized by the copolymer which is a base polymer, durability Is often inferior, and there is a problem that adjustment is very complicated because it is necessary to change the polymer composition and the crosslinking agent in order to achieve both durability and peripheral unevenness. Moreover, in patent document 11, although the adhesive which gave the phase difference is disclosed, operation | movement itself to extend | stretch is required.

  The present invention is capable of suppressing color unevenness, and even after the optical member is attached to the liquid crystal cell, the liquid crystal can be easily obtained even after a long period of time has passed through various processes or stored at a high temperature. It can be peeled off from the cell and can be reused without damaging or contaminating the liquid crystal cell, and when bonded, it has excellent durability that does not peel off or float, resulting from changes in the dimensions of optical members such as polarizing plates. It aims at providing the adhesive composition for optical members which is excellent also in the ease with respect to the stress to do. Moreover, this invention aims at providing the adhesive layer for optical members formed with the said adhesive composition for optical members. Furthermore, an object of the present invention is to provide an adhesive optical member having the adhesive layer and an image display device using the adhesive optical member.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the above-described object can be achieved by the following pressure-sensitive adhesive composition for optical members, and have completed the present invention.

That is, the present invention
As a monomer unit, an acrylic polymer (A) having a weight average molecular weight of 500,000 or more, containing 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms,
Acrylic polymer (B) 10 to 100 having a weight average molecular weight of 0.2 to 100,000 showing positive birefringence, containing 30% by weight or more of a monomer capable of forming a homopolymer showing positive birefringence as a monomer unit Parts by weight,
It is related with the adhesive composition for optical members characterized by containing 0.01-1 weight part of silane coupling agents, and a crosslinking agent.

  In the above-mentioned pressure-sensitive adhesive composition for optical members, the acrylic polymer (A) is at least a carboxyl group-containing monomer 0.1 in addition to an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms as a monomer unit. A copolymer obtained by copolymerizing ˜5% by weight and / or 0.1-10% by weight of a hydroxyl group-containing monomer is preferable.

  In the pressure-sensitive adhesive composition for an optical member, the acrylic polymer (B) reacts with at least a functional group of the crosslinking agent in addition to a monomer that can form a homopolymer exhibiting positive birefringence as a monomer unit. A copolymer obtained by copolymerizing 0.2 to 10% by weight of a monomer having a functional group is preferable.

  In the optical member pressure-sensitive adhesive composition, the crosslinking agent is preferably contained in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer (A).

  Moreover, this invention relates to the adhesive layer for optical members formed by bridge | crosslinking the said adhesive composition for optical members.

  The cross-linked pressure-sensitive adhesive layer for an optical member preferably has a gel fraction of 35 to 90% by weight.

  The present invention also relates to a pressure-sensitive adhesive optical member, wherein the pressure-sensitive adhesive layer is formed on one side or both sides of the optical member.

  Furthermore, the present invention relates to an image display device using at least one of the above adhesive optical members.

  The pressure-sensitive adhesive composition for an optical member of the present invention is a positive compound for a high molecular weight acrylic polymer (A) containing 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms. A low molecular weight acrylic polymer (B) exhibiting refraction is blended, and a small amount of a silane coupling agent and a crosslinking agent are blended. The pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition is peeled off and foamed even if it is stored in a high-temperature and high-humidity state after the optical member is attached to the liquid crystal cell due to the effect of the low molecular weight acrylic polymer (B). High durability that does not occur can be expressed. Further, by using the low molecular weight acrylic polymer (B), birefringence due to stress caused by dimensional change of an optical member such as a polarizing plate can be alleviated, and peripheral unevenness due to color unevenness or white spotting can be suppressed. In addition, even when the adhesive optical member is peeled from the liquid crystal panel and the liquid crystal cell is reused, the increase in the adhesive strength of the adhesive layer is small, and the adhesive optical member can be easily peeled off without adversely affecting the liquid crystal cell. can do.

  As described above, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention has a positive birefringence and has a low-molecular weight acrylic polymer (B), which has an effect of suppressing peripheral unevenness. Although the details are unknown, when the optical member is bonded to a liquid crystal cell with an adhesive layer, the birefringence of the adhesive due to the stress applied to the adhesive layer as the optical member shrinks or expands due to temperature, etc. It is thought that this is because it can be controlled. The high molecular weight acrylic polymer (A) exhibits negative birefringence, while the low molecular weight acrylic polymer (B) exhibits positive birefringence, and in addition to the low molecular weight acrylic polymer ( B) is incorporated into the crosslinked structure of the high molecular weight acrylic polymer (A). As a result, even when stress is applied to the pressure-sensitive adhesive layer, the low molecular weight acrylic polymer (B) that is easy to move is oriented, and the birefringence due to the stress applied to the pressure-sensitive adhesive layer is quickly canceled, thereby relaxing the stress. It is estimated that

  The high molecular weight acrylic polymer (A) of the present invention contains 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms as a monomer unit. In the present invention, alkyl (meth) acrylate refers to alkyl acrylate and / or alkyl methacrylate. (Meta) has the same meaning.

  For example, the alkyl group having 4 or more carbon atoms preferably has 4 to 14 carbon atoms, and more preferably 4 to 12 carbon atoms from the viewpoint of tackiness. The alkyl group can be either linear or branched. Examples of the alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms include n-butyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl ( Specific examples include meth) acrylate and isomyristyl (meth) acrylate. The alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms can be used alone or in combination of two or more.

  The acrylic polymer (A) contains, as a monomer unit, 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms. The content of the alkyl (meth) acrylate is preferably 50 to 99.9% by weight, and more preferably 60 to 99.9% by weight. When the content of the alkyl (meth) acrylate is less than 50% by weight, the stress relaxation property is poor, which is not preferable.

  The acrylic polymer (A) is preferably a copolymer obtained by copolymerizing a carboxyl group-containing monomer and / or a hydroxyl group-containing monomer with an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like. These anhydrides can also be used. Of these, acrylic acid and methacrylic acid are particularly preferably used.

  As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate , 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, hydroxyalkyl (meth) acrylate such as 12-hydroxylauryl (meth) acrylate; hydroxyethyl (meth) acrylamide, and others (4-hydroxymethyl (Cyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-hydroxy (meth) acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxy Butyl vinyl ether, such as diethylene glycol mono vinyl ether. As the hydroxyl group-containing monomer, hydroxyalkyl (meth) acrylate is preferable. The alkyl group of the hydroxyalkyl group has 2 to 12 carbon atoms, but the alkyl group of the hydroxyalkyl group preferably has 4 to 8 carbon atoms because of excellent heat stability when a peroxide is used as the crosslinking agent. Furthermore, it is preferable that it is C4-C6. A hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 4 to 8 carbon atoms has a small decrease in gel fraction due to molecular chain breakage of a peroxide-crosslinked (meth) acrylic polymer.

  In the acrylic polymer (A), the proportion of the carboxyl group-containing monomer is preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, as a monomer unit. When the content of the carboxyl group-containing monomer exceeds 5% by weight, the adhesive force to the liquid crystal cell is excessively increased. On the other hand, when the content is less than 0.1% by weight, the durability is adversely affected.

  In the acrylic polymer (A), the proportion of the hydroxyl group-containing monomer is preferably 0.1 to 10% by weight, more preferably 0.2 to 3% by weight, as a monomer unit. When the content of the hydroxyl group-containing monomer exceeds 10% by weight, the adhesive force to the liquid crystal cell becomes excessively large. On the other hand, when the content is less than 0.1% by weight, the durability is adversely affected.

  In addition to the carboxyl group-containing monomer and the hydroxyl group-containing monomer described above as the copolymerization monomer, the acrylic polymer (A) includes a main monomer, an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms, and the like. These copolymerizable monomers can be copolymerized. The other copolymerization monomer is used in an amount of 50% by weight or less, further 40% by weight or less, further 30% by weight or less, and further 20% by weight or less of the total monomer units of the acrylic polymer (A). In addition, when using another copolymerization monomer, it is preferable that the ratio is 0.01 weight% or more, Furthermore, 0.05 weight% or more, Furthermore, it is 0.1 weight% or more.

  As another copolymerization monomer, the alkyl (meth) acrylate which has a C1-C3 alkyl group can be illustrated, for example. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and the like. Other copolymerization monomers include glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, 3,4-epoxycyclohexyl (meth) acrylate-containing monomers; sulfonic acid group-containing monomers, phosphate groups Monomers that can improve cohesion and heat resistance, such as containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, N-acryloyl, vinyl ether monomers Can be used to such an extent that stress relaxation properties do not deteriorate and excessive crosslinking is not caused.

  For the production of such an acrylic polymer (A), known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations can be appropriately selected. Further, the acrylic polymer (A) to be obtained may be any of a random copolymer, a block copolymer, a graft copolymer and the like. As the radical polymerization initiator, various known azo and peroxide initiators can be used. For example, in solution polymerization, a polymerization initiator such as azobisisobutyronitrile is used in an amount of about 0.01 to 0.2 parts by weight with respect to 100 parts by weight of the total amount of monomers. As the polymerization solvent, for example, ethyl acetate, toluene and the like are used. As a specific example of solution polymerization, the reaction is carried out in an inert gas stream such as nitrogen and a polymerization initiator is added, and the reaction is usually performed at about 50 to 70 ° C. under reaction conditions of about 8 to 15 hours.

  The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited and can be appropriately selected and used. The weight average molecular weight of the acrylic polymer (A) can be controlled by the amount of polymerization initiator, chain transfer agent used, and reaction conditions, and the amount used is appropriately adjusted according to these types.

  Examples of the polymerization initiator 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, VA-057) and other azo initiators, and persulfates such as potassium persulfate and ammonium persulfate , Di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl -Oxydicarbonate, 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) ) Peroxides such as cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, peroxides and sodium bisulfite, peroxides and sodium ascorbate Redox initiators combined with Not intended to be.

  The polymerization initiator may be used alone or in combination 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 0.6 parts by weight.

  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. The chain transfer agent may be used alone or in combination of two or more, but the total content is 0.1 parts by weight with respect to 100 parts by weight of the total amount of monomer components. Less than or equal to

  Examples of the emulsifier used in emulsion polymerization 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 polyoxy Nonionic emulsifiers such as ethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer are listed. These emulsifiers may be used alone or in combination of two or more.

  Further, 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 (all of which are manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria soap SE10N (manufactured by 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 from the viewpoint of polymerization stability and mechanical stability with respect to 100 parts by weight of the total amount of monomer components.

  The weight average molecular weight of the acrylic polymer (A) is 500,000 or more, preferably 600,000 or more, more preferably 700,000 or more, and further preferably 800,000 or more. When the weight average molecular weight is less than 500,000, the durability tends to be poor, and the adhesive force tends to occur due to the reduced cohesive force of the pressure-sensitive adhesive composition, which is not preferable from the viewpoint of removability and workability. On the other hand, the weight average molecular weight of the acrylic polymer (A) is preferably 2 million or less, more preferably 1.8 million or less from the viewpoint of workability. It should be noted that the polymer obtained by emulsion polymerization is difficult to measure by GPC, and there is no problem in workability even in the range exceeding 2 million.

The weight average molecular weight of the acrylic polymer (A) was measured under the following conditions of a GPC (gel permeation chromatography) method.
Analyzer: HLC-8120GPC manufactured by Tosoh Corporation.
Column: Tosoh G7000HXL-H + GMHXL-H + GMHXL.
Column size: 7.8 mmφ × 30 cm each 90 cm in total.
Column temperature: 40 ° C.
Flow rate: 0.8 ml / min.
Eluent: tetrahydrofuran.
Solution concentration: about 0.1% by weight.
Injection volume: 100 μl.
Detector: Suggested refractometer (RI).
Standard sample: polystyrene.
Data processor: Tosoh GPC-8020.

  The acrylic polymer (B) contains 30% by weight or more of a monomer capable of forming a homopolymer exhibiting positive birefringence as a monomer unit. In addition, the acrylic polymer (B) is such that the acrylic polymer (B) itself exhibits positive birefringence by copolymerizing monomers capable of forming a homopolymer exhibiting positive birefringence. . In addition, the positive and negative of the polymer birefringence means that when the polymer is stretched, the slow axis (the direction in which the refractive index resulting from the anisotropy of the polarizability in the molecule increases) is the same as the stretching direction. A polymer having a positive birefringence, on the other hand, a polymer having a slow axis in the direction perpendicular to the stretching direction is judged as a polymer having a negative birefringence. The positive and negative birefringence can be measured by an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments).

  Monomers capable of forming a homopolymer exhibiting positive birefringence are monomers having a polymerizable carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group, and a substituent that gives positive birefringence. It is. Examples of such monomers include monomers described in “Polymer optical properties” (Publisher: Kyoritsu Shuppan Co., Ltd., page 25). Specifically, (meth) acrylate having a fluorinated alkyl group such as trifluoroethyl (meth) acrylate, trihydroperfluoropropyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate and the like. And (meth) acrylate having an aromatic ring such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and naphthylmethyl (meth) acrylate. These may be used individually by 1 type and may use 2 or more types together.

  The acrylic polymer (B) contains 30% by weight or more of a monomer capable of forming a homopolymer exhibiting positive birefringence as a monomer unit so that the acrylic polymer (B) exhibits positive birefringence. It is preferable to use 35% by weight or more, more preferably 40% by weight or more. On the other hand, in order to improve the compatibility with the acrylic polymer (A), the ratio of the monomer capable of forming a homopolymer exhibiting positive birefringence is preferably 70% by weight or less as a monomer unit. Preferably it is 65 weight% or less, More preferably, it is 60 weight% or less.

  Moreover, in order to improve compatibility with an acrylic polymer (A) as an acrylic copolymer (B), in order to improve compatibility with an acrylic polymer (A), the (meth) acrylic acid alkyl which has a C4 or more alkyl group is included in an acrylic polymer (B). Can be used. The alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms is preferably 30% by weight or more, more preferably 35% by weight or more, and further preferably 40% by weight or more as a monomer unit. However, an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms has a negative birefringence in its homopolymer, so the ratio is such that the resulting acrylic polymer (B) itself has a positive birefringence. Used in the range shown. Usually, the proportion of alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms is 70% by weight or less, preferably 65% by weight or less, more preferably 60% by weight or less, as a monomer unit.

  The acrylic polymer (B) is a monomer having a functional group that reacts with the functional group of the crosslinking agent as a monomer unit so that the acrylic polymer (A) is incorporated into the crosslinked structure when the acrylic polymer (A) is crosslinked. What copolymerized 0.2 to 10 weight% is suitable. The ratio of the monomer having a functional group to react is preferably 0.5 to 5% by weight. The monomer having a functional group can be appropriately selected depending on the type of the crosslinking agent. For example, when the crosslinking agent is an isocyanate crosslinking agent, it is preferable to use a hydroxyl group-containing monomer as the monomer having the functional group. As the hydroxyl group-containing monomer, the same ones as exemplified for the acrylic polymer (A) can be used. When the crosslinking agent is an epoxy crosslinking agent, it is preferable to use a carboxyl group-containing monomer as the monomer having the functional group.

  In addition to the copolymerization monomer, the acrylic polymer (B) includes the carboxyl group-containing monomer, an alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms, and an acrylic polymer (A). The acrylic monomer (B) itself can be used in a range that gives positive birefringence.

  The weight average molecular weight of the acrylic polymer (B) is 0.2 to 100,000, preferably 0.5 to 60,000. When the weight average molecular weight is less than 20,000, the durability is lowered. On the other hand, when the weight average molecular weight of the acrylic polymer (B) exceeds 100,000, the adhesive force to the liquid crystal cell increases, which is not preferable.

The weight average molecular weight of the acrylic polymer (B) was measured under the following conditions of GPC (gel permeation chromatography) method.
Analyzer: HLC-8120GPC manufactured by Tosoh Corporation.
Column: manufactured by Tosoh Corporation, GMH _HR -H + GMH _HR -H + G2000H _HR .
Column size: 7.8 mmφ × 30 cm each 90 cm in total.
Column temperature: 40 ° C.
Flow rate: 0.8 ml / min.
Eluent: tetrahydrofuran.
Solution concentration: about 0.1% by weight.
Injection volume: 100 μl.
Detector: Suggested refractometer (RI).
Standard sample: polystyrene.
Data processor: Tosoh GPC-8020.

  The production of the acrylic polymer (B) can employ the same method as that for the acrylic polymer (A). The weight average molecular weight can be adjusted by using a large amount of a polymerization initiator or a chain transfer agent such as mercaptan.

  The pressure-sensitive adhesive composition for an optical member of the present invention comprises the high molecular weight acrylic polymer (A), a low molecular weight acrylic polymer (B), a silane coupling agent, and a crosslinking agent. The compounding quantity of an acrylic polymer (B) is 10-100 weight part with respect to 100 weight part of acrylic polymer (A), Preferably it is 15-80 weight part, More preferably, it is 20-70 weight part. If the blending of the acrylic polymer (B) exceeds 100 parts by weight, the durability is adversely affected. If it is less than 10 parts by weight, the effect of peripheral unevenness is lost, which is not preferable.

  As the silane coupling agent, those conventionally known can be used without particular limitation. For example, epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-amino Propyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyl Amino group-containing silane coupling agents such as trimethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane; 3-acryloxypropyltrimethoxysilane, 3-methacrylic Roxypropyltriethoxysilane Any (meth) acrylic group-containing silane coupling agent; isocyanate group-containing silane coupling agent such as 3-isocyanatopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene), 3-tri And ethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine. Such a silane coupling agent is preferable for improving durability.

  Moreover, although a silane coupling agent may be used individually by 1 type and may mix and use 2 or more types, content as a whole is 100 weight part of acrylic polymers (A). The amount is 0.01 to 1 part by weight, preferably 0.02 to 0.6 part by weight, more preferably 0.05 to 0.3 part by weight. If the content of the silane coupling agent exceeds 1 part by weight, the adhesion to the liquid crystal cell increases and the removability is poor, and if it is less than 0.01 part by weight, it is difficult to improve the durability.

  The crosslinking agent is used for increasing the heat resistance of the mixture of the high molecular weight acrylic polymer (A), the low molecular weight acrylic polymer (B) and the silane coupling agent, and the low molecular weight acrylic polymer (B). Is incorporated into the crosslinked structure of the high molecular weight acrylic polymer (A).

  Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, a peroxide crosslinking agent, an imine crosslinking agent, an aziridine crosslinking agent, a melamine compound, a metal salt, and a metal chelate.

  The amount of the crosslinking agent used is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, with respect to 100 parts by weight of the acrylic polymer (A). If it is less than 0.01 part by weight, the cohesive force may be insufficient, which is not preferable. On the other hand, if it exceeds 2 parts by weight, the gel fraction after crosslinking becomes too high, and this is not preferable in that it is difficult to control physical properties such as a decrease in adhesiveness.

  As said crosslinking agent, an isocyanate type crosslinking agent and a peroxide crosslinking agent are preferable, and it is especially preferable to use together an isocyanate type crosslinking agent and a peroxide crosslinking agent. In addition, when an aqueous polymer such as an emulsion prepared by emulsion polymerization is used as the acrylic polymer (A) and / or the acrylic polymer (B), the reactivity with water is controlled as an isocyanate crosslinking agent. Blocked isocyanate crosslinking agents can be used. As the peroxide crosslinking agent, an organic peroxide crosslinking agent is preferably used.

  Examples of the isocyanate-based crosslinking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

  More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, 2,4-tolylene diisocyanate, Aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, polymethylene polyphenyl isocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.), tri Methylolpropane / hexamethylene diisocyanate trimer adduct (product name: Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), hexamethylene diiso Isocyanurate of anate (product name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.), polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, isocyanurate bond, burette bond And polyisocyanates polyfunctionalized with allophanate bonds.

  The isocyanate-based crosslinking agent may be used alone or in combination of two or more, but the total content is 100 parts by weight of the acrylic polymer (A). On the other hand, it is preferable to contain 0.01 to 2 parts by weight of the isocyanate-based crosslinking agent, more preferably 0.015 to 1.7 parts by weight, and 0.02 to 1.5 parts by weight. More preferably, If it is less than 0.01 part by weight, the cohesive force may be insufficient, which is not preferable. On the other hand, if it exceeds 2 parts by weight, the gel fraction after crosslinking becomes too high, which is not preferable in terms of difficulty in controlling physical properties.

  The peroxide can be used as appropriate as long as it generates radical active species by heating or light irradiation to cause the crosslinking of the base polymer of the pressure-sensitive adhesive composition, but considering workability and stability. Thus, it is preferable to use a peroxide having a half-life temperature of 80 ° C. to 160 ° C., and more preferable to use a peroxide having a 90 ° C. to 140 ° C. If the half-life temperature for 1 minute is too low, the reaction proceeds at the time of storage before coating and drying, and the viscosity may become high and the coating may become impossible. On the other hand, if the half-life temperature is too high, Since the temperature becomes high, side reactions occur, and a large amount of unreacted peroxide remains, which may cause cross-linking over time.

  Examples of the organic peroxide used in the present invention include di (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature: 90.6 ° C.), di (4-t-butylcyclohexyl) peroxydicarbonate. (1 minute half-life temperature: 92.1 ° C.), di-sec-butyl peroxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butyl peroxyneodecanoate (1 minute half-life temperature : 103.5 ° C), t-hexyl peroxypivalate (half-life temperature for 1 minute: 109.1 ° C), t-butyl peroxypivalate (half-life temperature for 1 minute: 110.3 ° C), dilauroyl par Oxide (1 minute half-life temperature: 116.4 ° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4 ° C.), 1,1,3,3-tetramethylbutyrate Peroxy-2-ethylhexanoate (1 minute half-life temperature: 124.3 ° C), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C), dibenzoyl peroxide (half-minute for 1 minute) Period temperature: 130.0 ° C.), t-butyl peroxyisobutyrate (1 minute half-life temperature: 136.1 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (1 minute half-life temperature: 149.2 ° C.). Especially, since the crosslinking reaction efficiency is excellent, di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life temperature: 92.1 ° C.), dilauroyl peroxide (1 minute half-life temperature: 116. 4 ° C), dibenzoyl peroxide (1 minute half-life temperature: 130.0 ° C) and the like are preferably used.

  The peroxide half-life is an index representing the decomposition rate of the peroxide, and means the time until the remaining amount of peroxide is reduced to half. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in a manufacturer catalog, for example, “Peroxide Catalog 9th Edition ( May 2003) ”and the like.

  The peroxide may be used alone or in combination of two or more, but the total content is 100 parts by weight of the acrylic polymer (A). The peroxide is 0.02 to 2 parts by weight, preferably 0.04 to 1.5 parts by weight, and more preferably 0.05 to 1 part by weight. If it is less than 0.02 parts by weight, the cross-linking is insufficient and the durability is not sufficient. On the other hand, when the amount exceeds 2 parts by weight, the amount of crosslinking becomes excessive and the adhesiveness becomes insufficient.

  In addition, when a peroxide is used as a polymerization initiator, it is possible to use the remaining peroxide for the crosslinking reaction without being used in the polymerization reaction. If necessary, it can be added again and used in a predetermined amount of peroxide.

  In addition, as a measuring method of the peroxide decomposition amount which remained after the reaction process, it can measure by HPLC (high performance liquid chromatography), for example.

  More specifically, for example, about 0.2 g of the pressure-sensitive adhesive composition after the reaction treatment is taken out, immersed in 10 ml of ethyl acetate, extracted by shaking at 25 ° C. and 120 rpm for 3 hours with a shaker, and then at room temperature. Leave for 3 days. Next, 10 ml of acetonitrile was added, shaken at 120 rpm at 25 ° C. for 30 minutes, and about 10 μl of the extract obtained by filtration through a membrane filter (0.45 μm) was injected into the HPLC for analysis. The amount of peroxide can be set.

  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. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

  The pressure-sensitive adhesive layer for optical members of the present invention is formed from the pressure-sensitive adhesive composition for optical members. The pressure-sensitive adhesive layer preferably has a gel fraction of 35 to 90% by weight from the viewpoint of workability that can satisfy the light releasability of the separator. The gel fraction is preferably 45 to 85% by weight, and more preferably 50 to 80% by weight. When the gel fraction is less than 35% by weight, the cohesive force tends to be inferior, and when it exceeds 90% by weight, the adhesiveness tends to be inferior. The gel fraction is a value measured by the method described in the examples.

  The pressure-sensitive adhesive layer is formed by the crosslinking agent. In forming the pressure-sensitive adhesive layer, it is necessary to adjust the addition amount of the crosslinking agent and sufficiently consider the influence of the crosslinking treatment temperature and the crosslinking treatment time. As a crosslinking agent, it shows below about an isocyanate type crosslinking agent and a peroxide.

  For example, when the pressure-sensitive adhesive composition contains a peroxide, the adjustment of the crosslinking treatment temperature and the crosslinking treatment time is preferably set so that the decomposition amount of the peroxide is 50% by weight or more. % Is more preferable, and it is further preferable to set the value to be 60% by weight or more. If the amount of peroxide decomposed is less than 50% by weight, the amount of peroxide remaining in the pressure-sensitive adhesive composition will increase, and the cross-linking reaction over time will occur even after heat treatment. The ratio may exceed 90% by weight, which is not preferable.

  More specifically, for example, at a crosslinking treatment temperature of 1 minute half-life temperature, the decomposition amount of peroxide is 50% by weight in 1 minute, and the decomposition amount of peroxide is 75% by weight in 2 minutes. A crosslinking treatment time of 1 minute or more is required. For example, if the half-life (half-life time) of the peroxide at the cross-linking treatment temperature is 30 seconds, a cross-linking treatment time of 30 seconds or more is required. For example, the half-life of the peroxide at the cross-linking treatment temperature If the (half time) is 5 minutes, a crosslinking treatment time of 5 minutes or more is required.

  Thus, the crosslinking treatment temperature and crosslinking treatment time can be calculated by theoretical calculation from the half-life (half-life time) assuming that the peroxide is linearly proportional to the peroxide used. It can be adjusted as appropriate. On the other hand, the higher the temperature, the higher the possibility of side reactions, so the crosslinking treatment temperature is preferably 170 ° C. or lower.

  Moreover, this crosslinking process may be performed at the temperature at the time of the drying process of an adhesive layer, and may be performed by providing a crosslinking process process separately after a drying process.

  The crosslinking treatment time can be set in consideration of productivity and workability, but is usually about 0.2 to 20 minutes, preferably about 0.5 to 10 minutes.

  The pressure-sensitive adhesive layer for an optical member can be formed by applying a heat treatment to the substrate and then curing it. In the pressure-sensitive adhesive optical member of the present invention, a pressure-sensitive adhesive layer is formed on at least one surface of the optical member with the pressure-sensitive adhesive.

  As a method for forming the pressure-sensitive adhesive layer, for example, using a separator or the like that has been peeled off as a base material, the pressure-sensitive adhesive composition is applied to the separator, the polymerization solvent or the like is removed by drying, and the pressure-sensitive adhesive is cured. There is a method of transferring to an optical member after forming the layer. Further, as a method of forming the pressure-sensitive adhesive layer, for example, using an optical member as a base material, the pressure-sensitive adhesive composition is directly applied to the optical member, and the polymerization solvent and the like are removed by drying and cured to be pressure-sensitive adhesive A method for forming the layer on the optical member is exemplified. In applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be added as appropriate.

  Examples of the solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, methanol, ethanol, n-propanol, isopropanol, water, and the like. These solvents may be used independently and may mix 2 or more types.

  In preparing the pressure-sensitive adhesive optical member of the present invention, an anchor layer may be formed on the surface of the optical member, or a pressure-sensitive adhesive layer may be formed after various easy adhesion treatments such as corona treatment and plasma treatment. it can. Moreover, you may perform an easily bonding process on the surface of an adhesive layer.

  Various methods are used as a method of forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples thereof include an extrusion coating method.

  The thickness of the pressure-sensitive adhesive layer (after drying) is not particularly limited, and is, for example, about 2 to 500 μm, preferably 5 to 100 μm.

  When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a sheet (separator) that has been subjected to a release treatment until practical use.

  Furthermore, the haze value of the pressure-sensitive adhesive layer is preferably 20% or less, more preferably 19% or less, and further preferably 18% or less. If the haze value exceeds 20%, the transmittance is greatly reduced when laminated on the optical member, which is not preferable. In the present invention, the acrylic polymer (A) is mixed with the acrylic polymer (B) that exhibits positive birefringence. By blending the acrylic polymer (B) in the above blending amount, The acrylic polymer (A) and the acrylic polymer (B) can be uniformly mixed without causing the haze value to increase and the transmittance to hardly decrease. . For this reason, what uses the range of the said haze value can be easily obtained by using the adhesive composition and adhesive layer of this invention.

  Examples of the constituent material of the separator include, 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. A thin film can be used, but a plastic film is preferably used because of its excellent surface smoothness.

  The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, and a vinyl chloride co-polymer are used. Examples thereof include a polymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

  The thickness of the separator is usually 5 to 200 μm, preferably about 5 to 100 μm. For the separator, if necessary, mold release and antifouling treatment with a silicone type, fluorine type, long chain alkyl type or fatty acid amide type release agent, silica powder, etc., coating type, kneading type, vapor deposition type It is also possible to carry out antistatic treatment such as. 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, or fluorine treatment on the surface of the separator. The pressure-sensitive adhesive layer of the present invention is suitable for a separator that has been subjected to a release treatment, and is particularly suitable for a separator that has been subjected to a release treatment by a silicone treatment.

  In addition, the sheet | seat which carried out the peeling process used in preparation of said adhesive type optical member can be used as a separator of an adhesive type optical member as it is, and can simplify in a process surface.

  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. A polarizing plate having a transparent protective film on one or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of polarizers include dichroic iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include polyene-based oriented films such as those obtained by adsorbing 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 prepared, for example, by immersing 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 or 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, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

  As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. A transparent protective film is bonded to one side of the polarizer by an adhesive layer. On the other side, as a transparent protective film, (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  Moreover, as a transparent protective film, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, (A) thermoplastic resin which has a substituted and / or unsubstituted imide group in a side chain, ( B) Resin compositions containing thermoplastic resins having substituted and / or unsubstituted phenyl and nitrile groups in the side chains. 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. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a transparent 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. The transparent protective film is particularly suitable when the thickness is 5 to 150 μm.

  In addition, when providing a transparent protective film on 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.

  As the transparent protective film of the present invention, it is preferable to use at least one selected from cellulose resin, polycarbonate resin, cyclic polyolefin resin, and (meth) acrylic resin.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercial products of triacetyl cellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “UZ” manufactured by Fuji Film Co., Ltd. -TAC "and" KC series "manufactured by Konica. In general, these triacetyl celluloses have an in-plane retardation (Re) of almost zero, but a thickness direction retardation (Rth) of about 60 nm.

  In addition, the cellulose resin film with a small thickness direction phase difference is obtained by processing the said cellulose resin, for example. For example, a base film such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, at 80 to 150 ° C. for about 3 to 10 minutes). ) And then peeling the base film; a solution obtained by dissolving norbornene resin, (meth) acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc. is applied to a general cellulose resin film and dried by heating ( For example, a method of peeling the coated film after 80 to 150 ° C. for about 3 to 10 minutes is mentioned.

  Moreover, as a cellulose resin film with a small thickness direction retardation, the fatty acid cellulose resin film which controlled the fat substitution degree can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8. Preferably, the Rth can be reduced by controlling the acetic acid substitution degree to 1.8 to 2.7. Rth can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, acetyltriethyl citrate to the fatty acid-substituted cellulose resin. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulose resin.

  Specific examples of the cyclic polyolefin resin are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying these with a carboxyl group-containing monomer or derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, product names “ARTON” manufactured by JSR Corporation, “TOPAS” manufactured by TICONA, and product names manufactured by Mitsui Chemicals, Inc. “APEL”.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability. From (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  The (meth) acrylic resin having a lactone ring structure preferably has a ring pseudo structure represented by the following general formula (Formula 1).

(Chemical formula 1)

^Wherein, R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the general formula (Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, More preferably, it is 10 to 60% by weight, and particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness are low. May be insufficient. If the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, molding processability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, and particularly preferably. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, it is not preferable from the viewpoint of moldability.

  The (meth) acrylic resin having a lactone ring structure preferably has a Tg of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. Since Tg is 115 ° C. or higher, for example, when incorporated into a polarizing plate as a transparent protective film, it has excellent durability. Although the upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  As the transparent protective film, one having a front phase difference of less than 40 nm and a thickness direction retardation of less than 80 nm is usually used. The front phase difference Re is represented by Re = (nx−ny) × d. The thickness direction retardation Rth is represented by Rth = (nx−nz) × d. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny). [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. In addition, it is preferable that a transparent protective film has as little color as possible. A protective film having a thickness direction retardation value 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 transparent 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.

  On the other hand, as the transparent protective film, a phase difference plate having a phase difference with a front phase difference of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a transparent protective film, so that the thickness can be reduced.

  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, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose resin, cyclic polyolefin resin (norbornene resin), or any of these binary, ternary copolymers, graft copolymers Examples thereof include polymers and blends. These polymer materials become an oriented product (stretched film) by stretching or the like.

  Examples of the liquid crystal 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. . Specific examples of the main chain type liquid crystal polymer include a nematic alignment polyester liquid crystal polymer, a discotic polymer, and a cholesteric polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment-providing para-substitution through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogenic part composed of a cyclic compound unit. These liquid crystal polymers can be prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment surface such as a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or an oblique deposition of 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 those for the purpose of compensating for various wavelength plates or birefringence of liquid crystal layers and compensation of viewing angle, etc. It may be one in which retardation plates are stacked and optical characteristics such as retardation are controlled.

  The retardation plate has a relationship of nx = ny> nz, nx> ny> nz, nx> ny = nz, nx> nz> ny, nz = nx> ny, nz> nx> ny, nz> nx = ny. What is satisfactory is selected and used according to various applications. Note that ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.

  For example, in a phase difference plate that satisfies nx> ny> nz, a surface plate having a front phase difference of 40 to 100 nm, a thickness direction phase difference of 100 to 320 nm, and an Nz coefficient of 1.8 to 4.5 is used. Is preferred. For example, in a retardation plate (positive A plate) that satisfies nx> ny = nz, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, for a retardation plate (negative A plate) that satisfies nz = nx> ny, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, in a retardation plate satisfying nx> nz> ny, it is preferable to use a retardation plate having a front phase difference of 150 to 300 nm and an Nz coefficient exceeding 0 to 0.7. As described above, for example, a material satisfying nx = ny> nz, nz> nx> ny, or nz> nx = ny can be used.

  The transparent protective film can be appropriately selected according to the applied liquid crystal display device. For example, in the case of VA (including Vertical Alignment, MVA, and PVA), it is desirable that at least one of the polarizing plates (cell side) has a retardation. As specific phase differences, it is desirable that Re = 0 to 240 nm and Rth = 0 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> ny> nz, nx> nz> ny, nx = ny> nz (positive A plate, biaxial, negative C plate) are desirable. In the VA type, it is preferable to use a combination of a positive A plate and a negative C plate, or one biaxial film. When polarizing plates are used above and below the liquid crystal cell, both the upper and lower sides of the liquid crystal cell may have a phase difference, or any one of the upper and lower transparent protective films may have a phase difference.

  For example, in the case of IPS (including In-Plane Switching, FFS), both cases where the transparent protective film on one side of the polarizing plate has a phase difference and does not have a phase difference can be used. For example, when there is no phase difference, it is desirable that the liquid crystal cell does not have a phase difference both above and below (cell side). In the case where the liquid crystal cell has a phase difference, it is desirable that the liquid crystal cell has a phase difference in the upper and lower sides, or the upper and lower sides have a phase difference (for example, nx> nz> ny on the upper side). Biaxial film satisfying the relationship, when there is no retardation on the lower side, positive A plate on the upper side, and positive C plate on the lower side). When it has a phase difference, it is desirable that Re = −500 to 500 nm and Rth = −500 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> nz> ny, nz> nx = ny, nz> nx> ny (positive A plate, biaxial, positive C plate) are desirable.

  In addition, the film which has the said phase difference can be separately bonded to the transparent protective film which does not have a phase difference, and the said function can be provided.

  The transparent protective film may be subjected to surface modification treatment in order to improve adhesiveness with the polarizer before applying the adhesive. Specific examples of the treatment include corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, and treatment with a coupling agent. Further, an antistatic layer can be appropriately formed.

  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.

  The 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 is used. 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. In addition, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer (for example, a backlight-side diffusion plate).

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by 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 conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 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.

  An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. The said adhesive agent is normally used as an adhesive agent which consists of aqueous solution, and contains 0.5 to 60 weight% of solid content normally. In addition to the above, examples of the adhesive between the polarizer and the transparent protective film include an ultraviolet curable adhesive and an electron beam curable adhesive. The electron beam curable polarizing plate adhesive exhibits suitable adhesion to the various transparent protective films. The adhesive used in the present invention can contain a metal compound filler.

  In addition, as an optical member, for example, for forming a liquid crystal display device such as a reflection plate, an anti-transmission plate, the retardation plate (including wavelength plates such as 1/2 and 1/4), a visual compensation film, and a brightness enhancement film. The optical layer which may be used is mentioned. These can be used alone as an optical member, or can be laminated on the polarizing plate for practical use and used as one layer or two 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 visual compensation film is further laminated on a plate, or a polarizing plate in which a luminance 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. In addition, the transparent protective film may contain fine particles to form 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. Moreover, the 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 of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by, for example, applying metal to the surface of the transparent protective layer 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 attaching directly to the screen.

  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 of a type that displays an image using a built-in power 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 can be used to form liquid crystal display devices that can save energy when using a light source such as a backlight in a bright atmosphere and can be used with a built-in power supply 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 an image is displayed in color, and also has an antireflection function.

  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 visual compensation film is a film for widening the viewing angle so that the 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. Examples of such a visual compensation phase difference plate include a phase difference plate, an alignment film such as a liquid crystal polymer, and a film in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film that is uniaxially stretched in the plane direction, whereas a retardation plate used as a visual compensation film is biaxially stretched 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 shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. can give. 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.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference 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 with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device 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 accordingly, the amount of light that can be used for liquid crystal image display or the like is reduced and the image becomes dark. The brightness enhancement film reflects light that has a polarization direction that is absorbed by the polarizer without being incident on the polarizer, and is reflected by the brightness enhancement film, and then inverted through a reflective layer or the like provided behind the brightness enhancement film. The brightness enhancement film transmits only the polarized light in which the polarization direction of the light reflected and inverted between the two is allowed to pass through the polarizer. Since the light is supplied to the polarizer, 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 light in the natural light state is directed toward the reflection layer or the like, reflected through the reflection layer or the like, and again passes through the diffusion plate and reenters the brightness enhancement film. In this way, by providing a diffuser plate that returns polarized light to the original natural light between the brightness enhancement film and the reflective layer, the brightness of the display screen is maintained, and at the same time, the brightness of the display screen is reduced and uniform. Can provide a bright screen. 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.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, 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 with the polarization axis aligned as it is, 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 transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is. 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 at a wide wavelength in the visible light region or the like exhibits, for example, a retardation plate that functions as a quarter-wave plate for light-colored light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method in which a phase difference layer, for example, a phase difference layer that functions as a half-wave plate is superimposed. 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, a cholesteric liquid crystal layer having a reflection structure that reflects circularly polarized light in a wide wavelength range such as a visible light range can be obtained by combining two or more layers with different reflection wavelengths to form 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 more optical layers as in 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-described reflective polarizing plate or semi-transmissive 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 or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an 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 retardation characteristics.

  In addition, each layer such as an optical member or an adhesive layer of the pressure-sensitive adhesive optical member of the present invention includes, for example, ultraviolet rays such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex compound. What gave the ultraviolet absorptivity by systems, such as a system processed with an absorber, 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. That is, 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 particular limitation except that an adhesive type optical member is used, and the conventional method can be applied. As the liquid crystal cell, any type such as a TN type, STN type, π type, VA type, IPS type, or the like 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 or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. The optical member (polarizing plate or the like) of the present invention can also be applied to an organic EL display device. Generally, 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 and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer is known. It has been.

  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.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, all the parts and% in each example are based on weight.

(Gel fraction)
As for the gel fraction, about 0.1 g of the pressure-sensitive adhesive layer immediately after the crosslinking treatment was taken and weighed to measure the weight (W1). Subsequently, this was immersed in about 50 ml of ethyl acetate at 23 ° C. for 7 days to extract soluble components. Thereafter, the pressure-sensitive adhesive layer was taken out and dried at 120 ° C. for 2 hours, and the total weight (W2) of the pressure-sensitive adhesive layer from which soluble components were removed was measured.
From these measured values, the gel fraction (% by weight) of the adhesive layer was determined according to the following formula.
Gel fraction (% by weight) = {(W2) / (W1)} × 100.

(Refractive index)
Under an atmosphere of 25 ° C., sodium D line was irradiated, and the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, DR-M2).

(Haze value)
A reflection / transmittance meter manufactured by Murakami Color Research Laboratory Co., Ltd. under an atmosphere of 25 ° C. using a sample obtained by cutting the pressure-sensitive adhesive layer provided on the polyethylene terephthalate obtained in each example into a width of 40 mm. In (HR-100 type), the haze value (%) was measured in accordance with JISK-7136 using D-65 light.

Production Example 1
(Preparation of high molecular weight acrylic polymer (A1))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 98 parts of n-butyl acrylate, 1 part of acrylic acid, 1 part of 4-hydroxybutyl acrylate, and 2,2-azobisiso After 0.1 part of butyronitrile and 200 parts of ethyl acetate were charged and sufficiently purged with nitrogen, the polymerization reaction was carried out at 55 ° C. for 12 hours with stirring under a nitrogen stream, and an acrylic polymer (A1 having a weight average molecular weight of 820,000) ) Was obtained. The acrylic polymer (A1) had negative birefringence.

Production Example 2
(Preparation of high molecular weight acrylic polymer (A2))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser, 30 parts of 2-ethylhexyl acrylate, 69 parts of n-butyl acrylate, 0.5 part of acrylic acid, 4-hydroxybutyl acrylate 5 parts, and 0.1 parts of 2,2-azobisisobutyronitrile and 200 parts of ethyl acetate were charged, and after sufficiently purging with nitrogen, a polymerization reaction was performed at 55 ° C. for 12 hours with stirring under a nitrogen stream. A solution of an acrylic polymer (A2) having a weight average molecular weight of 770,000 was obtained. The acrylic polymer (A2) had negative birefringence.

Production Example 3
(Preparation of high molecular weight acrylic polymer (A3))
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 99 parts of n-butyl acrylate, 0.5 part of acrylic acid, 0.5 part of 4-hydroxybutyl acrylate, and 2,2 -After charging 0.1 parts of azobisisobutyronitrile and 200 parts of ethyl acetate and sufficiently purging with nitrogen, the mixture was subjected to a polymerization reaction at 55 ° C for 12 hours with stirring under a nitrogen stream, and an acrylic having a weight average molecular weight of 800,000 A solution of the polymer (A3) was obtained. The acrylic polymer (A3) had negative birefringence.

Production Example 4
(Preparation of high molecular weight acrylic polymer (A4))
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 71 parts of n-butyl acrylate, 27 parts of benzyl acrylate, 1 part of acrylic acid, 1 part of 4-hydroxybutyl acrylate, and 2, After charging 0.1 part of 2-azobisisobutyronitrile and 200 parts of ethyl acetate and sufficiently purging with nitrogen, a polymerization reaction was performed at 55 ° C. for 12 hours with stirring under a nitrogen stream, and a weight average molecular weight of 730,000 was obtained. A solution of acrylic polymer (A4) was obtained. The acrylic polymer (A4) exhibited positive birefringence.

Production Example 5
(Preparation of low molecular weight acrylic polymer (B1))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser, n-butyl acrylate 48 parts, benzyl acrylate 50 parts, 4-hydroxybutyl acrylate 2 parts, lauryl mercaptan 3 parts, and 2, After charging 0.1 part of 2-azobisisobutyronitrile and sufficiently purging with nitrogen, the reaction was carried out at 55 ° C. for 12 hours with stirring under a nitrogen stream, and an acrylic polymer having a weight average molecular weight of 13,000 ( A solution of B1) was obtained. The acrylic polymer (B1) exhibited positive birefringence.

Production Example 6
(Preparation of low molecular weight acrylic polymer (B2))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, n-butyl acrylate 50 parts, phenoxyethyl acrylate 50 parts, lauryl mercaptan 4 parts, and 2,2-azobisisobutyro After 0.1 part of nitrile was charged and sufficiently purged with nitrogen, the reaction was carried out at 55 ° C. for 12 hours with stirring under a nitrogen stream to obtain a solution of an acrylic polymer (B2) having a weight average molecular weight of 9000. . The acrylic polymer (B2) did not have a crosslinkable functional group and had positive birefringence.

Production Example 7
(Preparation of low molecular weight acrylic polymer (B3))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 90 parts of n-butyl acrylate, 10 parts of benzyl acrylate, 2 parts of lauryl mercaptan, and 2,2-azobisisobutyronitrile After 0.1 part was charged and sufficiently purged with nitrogen, the mixture was reacted at 55 ° C. for 12 hours with stirring under a nitrogen stream to obtain a solution of an acrylic polymer (B3) having a weight average molecular weight of 15,000. The acrylic polymer (B3) had a negative birefringence and had no crosslinkable functional group.

Production Example 8
(Preparation of low molecular weight acrylic polymer (B4))
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube and condenser, n-butyl acrylate 48 parts, benzyl acrylate 50 parts, 4-hydroxybutyl acrylate 2 parts, lauryl mercaptan 0.4 parts, and After charging 0.1 part of 2,2-azobisisobutyronitrile and sufficiently purging with nitrogen, the mixture was reacted at 55 ° C. for 12 hours with stirring under a nitrogen stream, and an acrylic polymer having a weight average molecular weight of 120,000 ( A solution of B4) was obtained. The acrylic polymer (B4) exhibited positive birefringence.

Example 1
(Preparation of pressure-sensitive adhesive composition for optical members)
With respect to 100 parts of the acrylic polymer (A1) solution (solid content), 20 parts of the acrylic polymer (B1) solution (solid content), N-phenyl-3-aminopropyltrimethoxysilane 0 as a silane coupling agent .2 parts, trimethylolpropane hexamethylene diisocyanate adduct 0.3 part as an isocyanate-based cross-linking agent, and dibenzoyl peroxide 0.3 part as a peroxide are uniformly mixed to form an adhesive composition for an optical member (1) was prepared.

(Creation of adhesive optical member)
The pressure-sensitive adhesive composition (1) was applied to one side of a 38 μm-thick polyethylene terephthalate film (Mitsubishi Resin Co., Ltd., 38 μm thickness) subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive layer was 25 μm. And heated at 150 ° C. for 5 minutes to form an adhesive layer. The pressure-sensitive adhesive layer was transferred to a polarizing plate and aged at 50 ° C. for 24 hours to obtain a pressure-sensitive adhesive optical member. The pressure-sensitive adhesive layer immediately after drying had a gel fraction of 66%, a refractive index of 1.472, and a haze of 1.5%.

Examples 2-4, Comparative Examples 1-3
In Example 1, except that the acrylic polymer (A), the acrylic polymer (B), the silane coupling agent, the isocyanate crosslinking agent, the type of peroxide or the amount used were changed as shown in Table 1. In the same manner as in Example 1, a pressure-sensitive adhesive composition for optical members was prepared. Moreover, the adhesive optical member was created like Example 1 using the obtained adhesive composition. Table 1 shows the gel fraction, refractive index, and haze immediately after drying of the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive optical member. In Comparative Example 2, the refractive index could not be measured.

  The following evaluation was performed about the adhesion type optical member (polarizing plate) obtained by the Example and the comparative example. The results are shown in Table 1.

(Adhesiveness)
The pressure-sensitive adhesive optical member (sample) cut to a width of 25 mm was attached to an alkali-free glass plate (# 1737 manufactured by Corning Co., Ltd.) by one reciprocation of a 2 kg roll, and treated for 30 minutes in an autoclave at 50 ° C. and 0.5 Mpa. Next, the sample was allowed to stand under conditions of 23 ° C. and 50% RH for 3 hours, and then the peel adhesive force (initial adhesive force: N / 25 mm) was measured at a peel angle of 90 ° and a peel speed of 300 mm / min. After autoclaving, the sample is allowed to stand for 48 hours at 70 ° C. and further for 3 hours under conditions of 23 ° C. and 50% RH, and then peeled and bonded at a peeling angle of 90 ° and a peeling speed of 300 mm / min. The force (treatment adhesive force: N / 25 mm) was measured. It is desired that the adhesive force does not increase the initial adhesive force and the processing adhesive force after the heat treatment.

(durability)
The adhesive optical member cut into a 12-inch size was attached to a non-alkali glass (Corning # 1737) having a thickness of 0.5 mm, treated in an autoclave at 50 ° C. and 0.5 Mpa for 30 minutes, and then at 60 ° C. It was put in an atmosphere of 90% RH for 500 hours. Thereafter, the state of the adhesive optical member was visually observed and evaluated according to the following criteria.
○: There is no peeling or floating of the optical member.
X: There is peeling or floating of the optical member.

(Color unevenness)
The adhesive optical member cut into a 12-inch size was pasted on both sides of a 0.5 mm-thick alkali-free glass (Corning # 1737) so that the absorption axes of the polarizing plates were orthogonal to each other at 50 ° C. and 0.5 MPa. After processing for 30 minutes in an autoclave, it was put in an atmosphere at 90 ° C. for 500 hours. Thereafter, the color unevenness of the adhesive optical member was visually observed and evaluated according to the following criteria.
○: There is no color unevenness compared to before 90 ° C.
X: Color unevenness is present as compared to before introduction at 90 ° C.
In addition, “XX” in Comparative Example 2 indicates that light leakage is observed from the initial stage and color unevenness is present.

  In Table 1, among the items of the silane coupling agent, * 1 is N-phenyl-3-aminopropyltrimethoxysilane, * 2 is a methacryl group-containing silicone alkoxy oligomer (X-40-2655A manufactured by Shin-Etsu Silicone), * 3 represents 3-glycidoxypropyltrimethoxysilane. In each example, hexamethylene diisocyanate adduct of trimethylolpropane was used as the isocyanate crosslinking agent, and dibenzoyl peroxide was used as the peroxide in each example.

  It can be seen that the pressure-sensitive adhesive optical member of the present invention has a small difference between the initial adhesive strength and the 70 ° C. treated adhesive strength, and there is no increase in the adhesive strength when attached to the liquid crystal cell. In addition, it can be seen that even when treated at 90 ° C., the increase in the adhesive force is small, so that the adhesive force is small even after pasting for a long time such as disposal and glass and the optical member can be easily separated. Therefore, the removability is good regardless of the processing conditions, and it is easy to reuse the liquid crystal cell by re-peeling the optical member without destroying the adhesive residue or the liquid crystal cell. Moreover, durability and color unevenness can be satisfied even for a long-term severe test. On the other hand, the adhesive optical member of the comparative example does not satisfy durability and color unevenness.

Claims (6)

100 parts by weight of an acrylic polymer (A) having a weight average molecular weight of 500,000 or more and containing 50% by weight or more of an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms as a monomer unit Whereas
10-100 parts by weight of an acrylic polymer (B) having a weight average molecular weight of 0.2-100,000, which contains 30% by weight or more of a (meth) acrylate having an aromatic ring as a monomer unit and exhibits positive birefringence,
Ri Na contain a silane coupling agent 0.01 to 1 part by weight of a crosslinking agent,
In addition to the alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms as a monomer unit, the acrylic polymer (A) is at least 0.1 to 5% by weight of a carboxyl group-containing monomer and / or a hydroxyl group-containing monomer. A copolymer obtained by copolymerizing 0.1 to 10% by weight;
In addition to the (meth) acrylate having an aromatic ring as the monomer unit, the acrylic polymer (B) contains at least 0.2 to 10% by weight of a monomer having a functional group that reacts with the functional group of the crosslinking agent. an optical member for a pressure-sensitive adhesive composition characterized copolymer der Rukoto copolymerized. The pressure-sensitive adhesive composition for optical members according to claim 1 , wherein the crosslinking agent is contained in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer (A). The adhesive layer for optical members formed by bridge | crosslinking the adhesive composition for optical members of Claim 1 or 2 . The pressure-sensitive adhesive layer for an optical member according to claim 3 , wherein the gel fraction of the crosslinked pressure-sensitive adhesive layer for an optical member is 35 to 90% by weight. An adhesive optical member, wherein the pressure-sensitive adhesive layer according to claim 3 or 4 is formed on one surface or both surfaces of the optical member. An image display device using at least one adhesive optical member according to claim 5 .