JP2010078700A - Adhesive for polarizing plate, polarizing plate, method for manufacturing the same, optical film and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active energy ray curable adhesive for a polarizing plate, having an excellent adhesion property and water resistance. <P>SOLUTION: The active energy ray curable adhesive for the polarizing plate is used for disposing a transparent protective film on at least one face of a polarizer. The adhesive for the polarizing plate includes: a monofunctional monomer (A) containing an N-substituted amide-based monofunctional monomer (a) having a hydroxyl group; and a nonurethane-based multifunctional monomer (b) having at least two (meth)acrylate groups. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an active energy ray-curable polarizing plate adhesive. Moreover, this invention relates to the polarizing plate using the said adhesive agent for polarizing plates, and its manufacturing method. The polarizing plate can form an image display device such as a liquid crystal display device (LCD), an organic EL display device, a CRT, or a PDP alone or as an optical film in which the polarizing plate is laminated.

  Liquid crystal display devices are rapidly expanding in watches, mobile phones, PDAs, notebook computers, personal computer monitors, DVD players, TVs, and the like. The liquid crystal display device visualizes the polarization state by switching of the liquid crystal, and a polarizer is used from the display principle. In particular, in applications such as TV, higher brightness, higher contrast, and wider viewing angle are required, and polarizing plates are also required to have higher transmittance, higher degree of polarization, and higher color reproducibility.

  As a polarizer, for example, an iodine-based polarizer having a stretched structure obtained by adsorbing iodine to polyvinyl alcohol has a high transmittance and a high degree of polarization, and is therefore widely used as the most common polarizer. In general, a polarizing plate is used in which a transparent protective film is bonded to both sides of a polarizer with a so-called aqueous adhesive in which a polyvinyl alcohol-based material is dissolved in water. As the transparent protective film, triacetyl cellulose having a high moisture permeability is used.

  However, when a polarizing plate is manufactured as described above, when a water-based adhesive such as a polyvinyl alcohol-based adhesive is used, a drying step is required after the polarizer and the transparent protective film are bonded together. . The presence of a drying step in the production process of the polarizing plate is not preferable for improving the productivity of the polarizing plate.

  In addition, when using a water-based adhesive, in order to enhance the adhesion with the adhesive, the water content of the polarizer must be relatively high (usually the water content of the polarizer is about 30%) It is not possible to obtain a polarizing plate having good adhesion with an aqueous adhesive. However, the polarizing plate thus obtained has problems such as large dimensional changes at high temperatures and high temperatures and high humidity. On the other hand, in order to suppress the dimensional change, it is possible to reduce the moisture content of the polarizer or to use a transparent protective film having a low moisture permeability. However, when such a polarizer and a transparent protective film are bonded together using a water-based adhesive, the efficiency in the drying process is reduced, the polarization characteristics are reduced, or appearance defects occur, and a substantially useful polarizing plate is obtained. I can't.

  In addition, as represented by TVs in particular, as the screen size of image display devices has increased in recent years, it has become very important to increase the size of polarizing plates in terms of productivity and cost (yield and increase in number of products). Yes. However, in the polarizing plate using the water-based adhesive described above, the so-called light leakage (unevenness) that the polarizing plate causes a dimensional change due to the heat of the backlight and becomes uneven and the black display appears white in a part of the entire screen. ) Becomes prominent.

  For the reasons described above, it has been proposed to use an active energy ray curable adhesive (in particular, an ultraviolet curable adhesive) instead of the water-based adhesive. For example, an ultraviolet curable adhesive using an acrylic oligomer such as epoxy acrylate, urethane acrylate, or polyester acrylate as an adhesive, and an acrylic or methacrylic monomer as a diluent has been proposed (Patent Document 1). However, the performance required for polarizing plates has become strict, and when used in an active energy ray-curable adhesive, improvement in the adhesion between the polarizer and the transparent protective film is required.

  Further, it has been proposed to use urethane (meth) acrylate, hydroxy (meth) acrylate, and acrylamide derivatives as an active energy ray-curable adhesive for polarizing plates having good adhesion (Patent Document 2). However, although the adhesive for polarizing plate can improve the adhesiveness to some extent, the water resistance is not sufficient, and there is a problem that peeling occurs in a hydrothermal environment.

JP 61-246719 A JP 2007-177169 A

  An object of the present invention is to provide an active energy ray-curable adhesive for polarizing plates having good adhesion and water resistance.

  It is another object of the present invention to provide a polarizing plate in which a polarizer and a transparent protective film are bonded together with the polarizing plate adhesive, and have good adhesion and water resistance, and a method for producing the same.

  Another object of the present invention is to provide an optical film in which the polarizing plate is laminated, and to provide an image display device such as a liquid crystal display device using the polarizing plate and the optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following adhesive for polarizing plates and the like, and have completed the present invention.

That is, the present invention is an active energy ray curable polarizing plate adhesive used for providing a transparent protective film on at least one surface of a polarizer,
The polarizing plate adhesive is
A monofunctional monomer (A) containing an N-substituted amide monofunctional monomer (a) having a hydroxyl group and a non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups The present invention relates to an adhesive for polarizing plates.

  In the polarizing plate adhesive, as the non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups, a hydrocarbon-based or hydrocarbon ether-based polyfunctional monomer is suitable.

  In the polarizing plate adhesive, the ratio of the monofunctional monomer (A) to the total amount of 100 parts by weight of the monofunctional monomer (A) and the polyfunctional monomer (b) is 20 to 99.5 parts by weight. The ratio of the polyfunctional monomer (b) is preferably 0.5 to 80 parts by weight.

  In the adhesive for polarizing plate, the ratio of the monofunctional monomer (a) of N-substituted amide type having a hydroxyl group to the total amount of 100 parts by weight of the monofunctional monomer (A) and the polyfunctional monomer (b) is 20 parts by weight or more is preferable.

  In the polarizing plate adhesive, the active energy ray curable type is preferably an ultraviolet curable or electron beam curable polarizing plate adhesive.

  Moreover, this invention is a polarizing plate by which the transparent protective film is provided in the at least one surface of the polarizer through the adhesive bond layer, Comprising: The said adhesive bond layer is formed with the said adhesive agent for polarizing plates. The present invention relates to a polarizing plate.

  In the polarizing plate, as the transparent protective film, at least one selected from cellulose resin, polycarbonate resin, cyclic polyolefin resin, and (meth) acrylic resin is preferably used.

Further, the present invention is a method for producing a polarizing plate, wherein a transparent protective film is provided on at least one surface of a polarizer with an adhesive layer,
After applying the polarizing plate adhesive to the surface of the polarizer forming the adhesive layer and / or the surface of the transparent protective film forming the adhesive layer, the polarizer and the transparent protective film are pasted. The process of combining,
Next, a step of curing the adhesive by active energy ray irradiation to form an adhesive layer,
The present invention relates to a method for producing a polarizing plate, comprising:

  The present invention also relates to an optical film in which at least one polarizing plate is laminated.

  Furthermore, this invention relates to the image display apparatus characterized by using the said polarizing plate or the said optical film.

  Since the active energy ray-curable adhesive for polarizing plate of the present invention is a solventless adhesive, the polarizer and the transparent protective film are bonded together without performing a drying step as in the case of an aqueous adhesive. be able to. In addition, since the active energy ray-curable adhesive forms an adhesive layer by irradiation with active energy rays, it can be produced at higher speed than an aqueous adhesive.

  On the other hand, the active energy ray-curable adhesive for polarizing plates may have insufficient adhesive force between the polarizer and the transparent protective film. If the adhesive force is insufficient, there is a risk of delamination between the polarizer and the transparent protective film when the polarizing plate is misaligned and reworked. Further, when the adhesive force is improved, a problem of water resistance occurs. The active energy ray curable polarizing plate adhesive of the present invention improves the adhesive force by using the N-substituted amide monofunctional monomer (a) having the hydroxyl group as the monofunctional monomer (A). By using the non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups in addition to the monofunctional monomer (a) and suppressing delamination in rework, for example, By forming a cross-linked structure based on a non-urethane main skeleton such as hydrocarbon or hydrocarbon ether, water resistance can be improved, which cannot be obtained by cross-linking with polyfunctional urethane (meth) acrylate. Prevents peeling in the environment.

  The active energy ray curable adhesive for polarizing plates can be used as an electron beam curable adhesive or an ultraviolet curable adhesive, but is preferably used as an electron beam curable adhesive. Electron beam curable adhesives are more productive than ultraviolet curable adhesives, and UV curing is achieved by using electron beams as a method for curing adhesives used to bond polarizers and transparent protective films. This eliminates the need for a heating step as in the method, and can greatly increase the productivity. Further, by using an electron beam curable adhesive, the durability of the polarizing plate can be improved as compared with the ultraviolet curable adhesive.

  In addition, when an active energy ray-curable adhesive for polarizing plates is applied as an electron beam-curable adhesive, for example, when a polarizer with a low moisture content is used, a material with low moisture permeability as a transparent protective film is also used. Even when is used, a good adhesiveness to these is exhibited, and as a result, a polarizing plate with good dimensional stability is obtained. A polarizing plate having a small dimensional change can easily cope with an increase in the size of the polarizing plate, and can suppress production costs from the viewpoint of yield and number of production. Further, since the polarizing plate obtained in the present invention has good dimensional stability, it is possible to suppress the occurrence of unevenness in the image display device due to the external heat of the backlight.

  The polarizing plate adhesive of the present invention is a non-urethane having a monofunctional monomer (A) containing an N-substituted amide monofunctional monomer (a) having a hydroxyl group and at least two (meth) acrylate groups. A polyfunctional monomer (b).

  The N-substituted amide monofunctional monomer (a) having a hydroxyl group has one (meth) acrylamide group and has at least one substituent as a substituent bonded to the nitrogen atom (N) forming the amide group. It has a hydroxyl group. The N-substituted amide-based monofunctional monomer (a) having a hydroxyl group exhibits good adhesion even to a polarizer having a low moisture content and a transparent protective film using a material having a low moisture permeability. The N-substituted amide monofunctional monomer (a) having a hydroxyl group can be selected from one kind or a combination of two or more kinds. In addition, (meth) acrylamide means an acrylamide group and / or a methacrylamide group. In the present invention, (meta) has the same meaning as described above.

  Examples of the N-substituted amide monofunctional monomer (a) having a hydroxyl group include N-hydroxyalkyl (meth) acrylamides such as N-hydroxyethyl (meth) acrylamide and N-hydroxymethyl (meth) acrylamide, N- (2,2-dimethoxy-1-hydroxyethyl)-(meth) acrylamide, p-hydroxyphenyl (meth) acrylamide and the like can be mentioned. Among these, N-hydroxyalkyl (meth) acrylamide is preferable because of good adhesion to the polarizer, and N-hydroxyethyl (meth) acrylamide is particularly preferable.

  Examples of the other monofunctional monomer (A) other than the N-substituted amide monofunctional monomer (a) having a hydroxyl group include, for example, a compound having a (meth) acryloyl group, and a polymerizable group such as a vinyl group. And a monofunctional compound having one carbon-carbon double bond. These monofunctional compounds used as the curable component can be used by selecting one kind or appropriately combining two or more kinds.

As the other monofunctional monomer (A), for example, an N-substituted amide monofunctional monomer other than the hydroxyl group-containing monofunctional monomer (a) is preferably used. The N- substituted amide monomers represented by the general formula ^{_{(1): CH 2 = C}} (R 1) -CONR 2 (R 3) (R 1 represents a hydrogen atom or a methyl group, ^{R 2} represents a hydrogen atom or a mercapto group Represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have an amino group or a quaternary ammonium group, and R ³ represents a hydrogen atom or a linear or branched chain having 1 to 4 carbon atoms Represents an alkyl group, except that R ² and R ³ are simultaneously hydrogen atoms, or R ² and R ³ are bonded to form a 5-membered or 6-membered ring which may contain an oxygen atom. ). Examples of the linear or branched alkyl group having 1 to 4 carbon atoms for R ² or R ³ in the general formula (1) include a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of the alkyl group having an amino group include an aminomethyl group and an aminoethyl group. Moreover, when R < ² >, R < ³ > couple | bonds together and forms the 5-membered ring or 6-membered ring which may contain an oxygen atom, it has a heterocyclic ring which has nitrogen. Examples of the heterocyclic ring include morpholine ring, piperidine ring, pyrrolidine ring, piperazine ring and the like.

  Specific examples of the N-substituted amide monomer include, for example, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N- Butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaapt Examples thereof include methyl (meth) acrylamide and mercaptoethyl (meth) acrylamide. Examples of the heterocycle-containing monomer having a heterocycle include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine and the like. These N-substituted amide monomers can be used singly or in combination of two or more.

  As the monofunctional monomer (A), an N-substituted amide monofunctional monomer (a) having a hydroxyl group and an N-substituted amide monofunctional monomer (A) represented by the general formula (1) are used. When used in combination, a combination of N-hydroxyethyl (meth) acrylamide and N-acryloylmorpholine is preferable from the viewpoint of coatability.

  Further, as the N-substituted amide monofunctional monomer (a) having a hydroxyl group, in addition to the above, as a compound having a (meth) acryloyl group, for example, various epoxy (meth) acrylates and urethane (meth) Examples include acrylates, polyester (meth) acrylates, and various (meth) acrylate monomers. Among these, epoxy (meth) acrylates, particularly monofunctional (meth) acrylates having an aromatic ring and a hydroxy group are preferably used.

  As the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, various monofunctional (meth) acrylates having an aromatic ring and a hydroxy group can be used. The hydroxy group may exist as a substituent of the aromatic ring, but in the present invention, it exists as an organic group (bonded to a hydrocarbon group, particularly an alkylene group) that bonds the aromatic ring and the (meth) acrylate. Those that do are preferred.

  Examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include a reaction product of a monofunctional epoxy compound having an aromatic ring and (meth) acrylic acid. Examples of the monofunctional epoxy compound having an aromatic ring include phenyl glycidyl ether, t-butylphenyl glycidyl ether, and phenyl polyethylene glycol glycidyl ether. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-t-butylphenoxypropyl (meth) Examples thereof include acrylate and 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate.

  In addition, as the urethane (meth) acrylate, a hydroxyl group at one end of a (meth) acrylate having an isocyanate group and a diol compound such as polyurethane diol, polyester diol, polyether diol, polyether glycol, polyethylene glycol, polypropylene glycol or the like polyalkylene glycol And the like.

  Moreover, a carboxyl group monomer is mention | raise | lifted as a compound which has a (meth) acryloyl group. A carboxyl group monomer is also preferable in terms of adhesiveness. Examples of the carboxyl group monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and the like. Of these, acrylic acid is preferred.

  In addition to the above, compounds having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl. Alkyl (meth) acrylates having 1 to 12 carbon atoms such as (meth) acrylate and lauryl (meth) acrylate; (meth) acrylic acid alkoxyalkyl systems such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl Monomer: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy (meth) acrylate Octyl, (meth) acrylic acid 10-H Hydroxyl-containing monomers such as loxydecyl, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone addition of acrylic acid Products; sulfones such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid Acid group-containing monomers; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. (Meth) acrylamide; maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc .; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate , (Meth) acrylic acid alkylaminoalkyl monomers such as (meth) acrylic acid t-butylaminoethyl, 3- (3-pyridinyl) propyl (meth) acrylate; N- (meth) acryloyloxymethylene succinimide and N- ( And nitrogen-containing monomers such as succinimide monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

  The polarizing plate adhesive of the present invention has at least 2 (meth) acrylate groups in addition to the monofunctional monomer (A) containing the N-substituted amide monofunctional monomer (a) having the hydroxyl group. A non-urethane polyfunctional monomer (b). The non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups has at least two (meth) acrylate groups and is a polyhydric alcohol in which a main skeleton ((meth) acrylate group is introduced). Various compounds in which the residue) does not have a urethane bond can be used. The number of (meth) acrylate groups is preferably 2 to 5 and more preferably 2 to 4 from the viewpoint of adhesion by crosslinking. The said polyfunctional monomer (b) can select 1 type, or can be used in combination of 2 or more type.

  Examples of the non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups include hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers. A hydrocarbon-based or hydrocarbon ether-based polyfunctional monomer is a compound in which a hydroxyl group of a polyhydric alcohol having a main skeleton of a hydrocarbon group having 10 to 100 carbon atoms or a hydrocarbon ether group is (meth) acrylated. From the viewpoint of adhesiveness due to crosslinking. Examples of the hydrocarbon group of the polyhydric alcohol include a linear or branched aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and a hydrocarbon group obtained by combining these hydrocarbon groups. Examples of the hydrocarbon ether group include etherification of the hydrocarbon group. In addition, examples of the polyhydric alcohol having a hydrocarbon ether group as a main skeleton include compounds (addition number 1 to 30) obtained by adding an alkylene oxide having 2 to 4 carbon atoms to the polyhydric alcohol, And polyalkylene glycols (addition number 1 to 30) obtained from alkylene oxide.

  Specific examples of the hydrocarbon-based bifunctional monomer include, for example, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) ) Diacrylates of alkylene glycols such as acrylates and neopentyl glycol di (meth) acrylates; Alicyclic carbonizations such as cyclohexanedimethanol di (meth) acrylates and tricyclodecane dimethanol di (meth) acrylates Di (meth) acrylate of a diol compound having a hydrogen group; di (meth) acrylate of a diol compound having an aromatic hydrocarbon group such as bisphenol A di (meth) acrylate.

  Specific examples of the hydrocarbon ether-based bifunctional monomer include, for example, alkoxylated hexanediol di (meth) acrylate, alkoxylated cyclohexanedimethanol di (meth) acrylate, and alkoxylated di (meth) acrylate. , Dialkyl diol compounds obtained by adding alkylene oxide to alkylene glycol or diol compounds described in the above hydrocarbon-based bifunctional monomers such as alkoxylated neopentyl glycol di (meth) acrylate and alkoxylated bisphenol A di (meth) acrylate (Meth) acrylate and the like. Specific examples of the hydrocarbon ether-based bifunctional monomer include diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Examples thereof include di (meth) acrylates of polyalkylene glycols such as tripropylene glycol di (meth) acrylate and dipropylene glycol di (meth) acrylate, and dioxane glycol di (meth) acrylate.

  In addition, as a hydrocarbon-based or hydrocarbon ether-based trifunctional monomer or tetrafunctional monomer, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, glyceryl tri (meth) acrylate, Tri (meth) acrylate or tetra (meth) acrylate of a tri- or tetraol compound such as pentaerythritol tetra (meth) acrylate or trimethylolpropane tetra (meth) acrylate, or an alkylene oxide added to the above tri- or tetraol compound Examples of the compound include tri (meth) acrylate and tetra (meth) acrylate.

  Further, as the non-urethane polyfunctional monomer (b) other than the hydrocarbon type or hydrocarbon ether type, polyester poly (meth) acrylate having two or more (meth) acrylate groups at the terminal, epoxy (meth) acrylate Etc.

  In the adhesive for polarizing plate of the present invention, the ratio of the monofunctional monomer (A) and the polyfunctional monomer (b) is the ratio of the monofunctional monomer (A) to the total amount of 100 parts by weight. Is 20 to 99.5 parts by weight, and the ratio of the polyfunctional monomer (b) is preferably 0.5 to 80 parts by weight. The proportion of the polyfunctional monomer (b) is further preferably 5 to 70 parts by weight, and more preferably 5 to 60 parts by weight. When the proportion of the polyfunctional monomer (b) is less than 0.5 parts by weight, sufficient water resistance may not be obtained. On the other hand, when it is more than 80 parts by weight, sufficient adhesion is obtained. It may not be possible. Corresponding to the proportion of the polyfunctional monomer (b), the proportion of the monofunctional monomer (A) is preferably 30 to 95 parts by weight, more preferably 40 to 95 parts by weight.

  The proportion of the monofunctional monomer (A) in the polarizing plate adhesive of the present invention is as described above with respect to 100 parts by weight of the total amount of the monofunctional monomer (A) and the polyfunctional monomer (b). Although it is 20-99.5 weight part, the ratio of the N-substituted amide type monofunctional monomer (a) which has a hydroxyl group contained in the said monofunctional monomer (A) is the said adhesiveness and water resistance. From the viewpoint of the characteristics, etc., 20 to 95 parts by weight is preferable with respect to 100 parts by weight of the total amount of the monofunctional monomer (A) and the polyfunctional monomer (b), and more preferably 40 to 95 parts by weight. Further, 80 to 95 parts by weight are preferable.

  In addition, in the adhesive agent for polarizing plates of this invention, in addition to the said polyfunctional monomer (b), it may contain the other polyfunctional compound which has two or more polymerizable carbon-carbon double bonds. it can. The ratio of another polyfunctional compound can be contained in the range which does not impair the effect of a polyfunctional monomer (b).

  The polarizing plate adhesive of the present invention comprises a monofunctional monomer (A) containing the N-substituted amide monofunctional monomer (a) having the hydroxyl group as a curable component, and a (meth) acrylate group. The non-urethane polyfunctional monomer (b) having at least two is included, but if necessary, additives may be added in addition to the above components. The active energy ray curable adhesive can be used in an electron beam curable type or an ultraviolet curable type. When the adhesive is used as an electron beam curable type, it is not particularly necessary for the adhesive to contain a photopolymerization initiator, but when used as an ultraviolet curable type, a photopolymerization initiator is used. .

  As the photopolymerization initiator, a radical photopolymerization initiator and / or a cationic photopolymerization initiator are used. Examples of these are 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, methoxyacetophenone, 2,2-dimethoxy-2-phenyl. Acetophenone compounds such as acetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1, benzoin ethyl ether, benzoin Benzoin ether compounds such as isopropyl ether and anisoin methyl ether, α-ketol compounds such as 2-methyl-2-hydroxypropiophenone, ketal compounds such as benzyldimethyl ketal, 2-naphthalenesulfonyl chloride Aromatic sulfonyl chloride compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime, photoactive oxime compounds such as benzophenone and benzoylbenzoic acid, 3,3'-dimethyl- Examples thereof include photopolymerization initiators such as benzophenone compounds such as 4-methoxybenzophenone. The amount of the photopolymerization initiator used is usually about 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, more preferably 1 to 4 parts by weight per 100 parts by weight of the curable component.

  Examples of additives include sensitizers that increase the curing speed and sensitivity by electron beams typified by carbonyl compounds, adhesion promoters typified by silane coupling agents and ethylene oxide, and wettability with transparent protective films. Such as acryloxy group compounds and hydrocarbons (natural and synthetic resins), additives that improve mechanical strength and processability, UV absorbers, anti-aging agents, dyes, and processing aids , Ion trapping agents, antioxidants, tackifiers, fillers, metal compound fillers, plasticizers, leveling agents, foaming inhibitors, antistatics and the like.

  As for the polarizing plate of this invention, the polarizer and the transparent protective film are bonded together through the adhesive bond layer formed with the said adhesive agent for polarizing plates.

  In the bonding step in the manufacturing method, the adhesive is applied to the surface of the polarizer where the adhesive layer is formed and / or the surface of the transparent protective film where the adhesive layer is formed, and then the polarizer and the transparent protection are applied. Step of bonding the film with the polarizing plate adhesive; Next, active energy rays (electron beam, ultraviolet ray) with respect to the polarizer and the transparent protective film bonded together with the polarizing plate adhesive Etc.) to form an adhesive layer.

  The polarizer and the transparent protective film may be subjected to surface modification treatment before the adhesive is applied. Specific examples of the treatment include corona treatment, plasma treatment, and saponification treatment.

  The adhesive coating method is appropriately selected depending on the viscosity of the adhesive and the target thickness. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, and the like. In addition, for coating, a method such as a dapping method can be appropriately used.

  A polarizer and a transparent protective film are bonded together through the adhesive applied as described above. The polarizer and the transparent protective film can be bonded together using a roll laminator or the like.

  After bonding a polarizer and a transparent protective film, an active energy ray (an electron beam, ultraviolet rays, etc.) is irradiated and an adhesive agent is hardened. The irradiation direction of active energy rays (electron beam, ultraviolet ray, etc.) can be irradiated from any appropriate direction. Preferably, it irradiates from the transparent protective film side. When irradiated from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, etc.).

  The active energy ray curable adhesive is preferably used as an electron beam curable adhesive. Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, There is a risk of damaging the polarizer. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent protective film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can cure | harden the said adhesive agent. The dose of ultraviolet rays is preferably from 50~1500mJ / cm ² in accumulated light quantity, and even more preferably 100 to 500 mJ / cm ^2.

  The thickness of the adhesive layer in the polarizing plate of the present invention obtained as described above is 0.01 to 7 μm. Preferably it is 0.01-5 micrometers, More preferably, it is 0.01-2 micrometers, More preferably, it is 0.01-1 micrometer. When the thickness is less than 0.01 μm, the cohesive force of the adhesive force itself cannot be obtained, and the adhesive strength may not be obtained. If the thickness of the adhesive layer exceeds 7 μm, the polarizing plate cannot satisfy the durability.

  Electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or under a condition in which a small amount of oxygen is introduced. Depending on the material of the transparent protective film, by appropriately introducing oxygen, the transparent protective film surface where the electron beam first hits can be obstructed to prevent oxygen damage and prevent damage to the transparent protective film. An electron beam can be irradiated efficiently.

  When performing the said manufacturing method by a continuous line, although it depends on the hardening time of an adhesive agent, Preferably it is 1-500 m / min, More preferably, it is 5-300 m / min, More preferably, it is 10-100 m / min. When the line speed is too low, productivity is poor, or damage to the transparent protective film is too great, and a polarizing plate that can withstand a durability test or the like cannot be produced. When the line speed is too high, the adhesive is not sufficiently cured, and the target adhesiveness may not be obtained.

  In the polarizing plate of the present invention, a polarizer and a transparent protective film are bonded via an adhesive layer formed by the polarizing plate adhesive, but between the transparent protective film and the adhesive layer. An easy-adhesion layer can be provided. The easy adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Moreover, you may add another additive for formation of an easily bonding layer. Specifically, a stabilizer such as a tackifier, an ultraviolet absorber, an antioxidant, and a heat resistance stabilizer may be used.

  The easy adhesion layer is usually provided in advance on a transparent protective film, and the easy adhesion layer side of the transparent protective film and the polarizer are bonded together with an adhesive layer. The easy-adhesion layer is formed by coating and drying the material for forming the easy-adhesion layer on the transparent protective film by a known technique. The material for forming the easy-adhesion layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying and the smoothness of coating. The thickness of the easy adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. Note that a plurality of easy-adhesion layers can be provided, but also in this case, the total thickness of the easy-adhesion layers is preferably in the above range.

  The polarizer is formed from a polyvinyl alcohol-based resin. The polarizer is a uniaxially stretched film obtained by dyeing a polyvinyl alcohol resin film with a dichroic substance (typically iodine or a dichroic dye). The degree of polymerization of the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is preferably 100 to 6000, more preferably 2000 to 6000. If the degree of polymerization is too low, the film tends to be stretched when performing predetermined stretching, and if the degree of polymerization is too high, tension may be abnormally required for stretching, and mechanical stretching may not be possible.

  The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any appropriate method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). Although the thickness of a polarizer is suitably set according to the objective and use of LCD with which a polarizing plate is used, it is about 5-80 micrometers normally.

  As a manufacturing method of the polarizer, any appropriate method is adopted depending on the purpose, material used, conditions and the like. For example, the system which uses the said polyvinyl alcohol-type resin film for a series of manufacturing processes including a swelling, dyeing | staining, bridge | crosslinking, extending | stretching, a water washing, and a drying process is employ | adopted normally. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol-based resin film in a liquid containing a solution used in each step. The order, number of times, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing and drying can be appropriately set according to the purpose, materials used and conditions. For example, several processes may be performed simultaneously in one step, and the swelling process, the dyeing process, and the crosslinking process may be performed simultaneously. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. For example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath filled with water. By this treatment, dirt on the surface of the polyvinyl alcohol-based resin film and an anti-blocking agent can be washed, and unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based resin film. Glycerin, potassium iodide or the like is appropriately added to the swelling bath. The temperature of the swelling bath is usually about 20 to 60 ° C., and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

  The dyeing process is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. A dichroic substance is normally used in the ratio of 0.1-1 weight part with respect to 100 weight part of solvents. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.02 to 20 parts by weight, more preferably 2 to 10 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The temperature of the dyeing bath is usually about 20 to 70 ° C., and the immersion time in the dyeing bath is usually about 1 to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polyvinyl alcohol-based resin film in a treatment desire containing a crosslinking agent. Arbitrary appropriate crosslinking agents are employ | adopted as a crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. A crosslinking agent is normally used in the ratio of 1-10 weight part with respect to 100 weight part of solvents. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot be obtained. When the concentration of the cross-linking agent exceeds 10 parts by weight, the stress generated in the film during stretching increases, and the resulting polarizing plate may shrink. It is desirable that the solution of the crosslinking bath further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as those in the dyeing process. The temperature of the crosslinking bath is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polyvinyl alcohol-based resin film is usually 5 times or more. Preferably it is 5 to 7 times, more preferably 5 to 6.5 times. When the cumulative draw ratio is less than 5 times, it is difficult to obtain a polarizing plate having a high degree of polarization. When the cumulative draw ratio exceeds 7 times, the polyvinyl alcohol-based resin film may be easily broken. Arbitrary appropriate methods are employ | adopted as a specific method of extending | stretching. For example, when a wet stretching method is employed, a polyvinyl alcohol resin film is stretched at a predetermined magnification in a treatment bath. As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polyvinyl alcohol-based resin film subjected to the above-described various treatments in a treatment bath. The unnecessary residue of the polyvinyl alcohol-based resin film can be washed away by the water washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide, sodium iodide, etc.). The concentration of the aqueous iodide solution is preferably 0.1 to 10% by weight. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is 1 second to 1 minute. The washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process are adjusted suitably. For example, the water washing step includes a step of immersing the polyvinyl alcohol resin film subjected to the above various treatments in an aqueous potassium iodide solution (0.1 to 10% by weight, 10 to 60 ° C.) for about 1 second to 1 minute, and pure water. Including rinsing process. In the water washing step, an organic solvent having compatibility with water (for example, ethanol) may be added as appropriate in order to improve the surface of the polarizer and increase the drying efficiency of the polarizer.

  Arbitrary appropriate methods (For example, natural drying, ventilation drying, heat drying) may be employ | adopted for a drying process. For example, the drying temperature in the case of heat drying is usually about 20 to 80 ° C., and the drying time is usually about 1 to 10 minutes. A polarizer is obtained as described above.

  The polarizer used in the present invention has a moisture content of preferably 20% by weight or less, more preferably 0 to 15% by weight, and still more preferably 1 to 15% by weight. When the moisture content is larger than 20% by weight, the dimensional change of the obtained polarizing plate becomes large, which may cause a problem that the dimensional change at high temperature or high temperature and high humidity becomes large.

  The moisture content of the polarizer of the present invention may be adjusted by any appropriate method. For example, there is a method of controlling by adjusting the conditions of the drying process in the manufacturing process of the polarizer.

  The moisture content of the polarizer is measured by the following method. That is, the polarizer was cut out to a size of 100 × 100 mm, and the initial weight of this sample was measured. Subsequently, this sample was dried at 120 ° C. for 2 hours, the dry weight was measured, and the moisture content was measured by the following formula. Moisture content (% by weight) = {(initial weight−dry weight) / initial weight} × 100. The weight was measured three times, and the average value was used.

  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 with 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. The adhesive for electron beam curable polarizing plates of the present invention exhibits suitable adhesion to the various transparent protective films. In particular, the electron beam curable polarizing plate adhesive of the present invention exhibits good adhesion to acrylic resins that have been difficult to satisfy adhesiveness.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of such cellulose ester resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available cellulose triacetate are trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “UZ” manufactured by Fuji Photo Film Co., Ltd. -TAC "and" KC series "manufactured by Konica. In general, these cellulose triacetates 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.

  A specific example of the cyclic polyolefin resin is preferably a norbornene resin. 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 them with an unsaturated carboxylic acid or a 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, trade names “ARTON” manufactured by JSR Corporation, “TOPASS” manufactured by TICONA, and trade 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 lower from the viewpoint of moldability and the like. From the (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.

  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 retardation value (Rth) in the thickness direction 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.

  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 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 (uniaxial, biaxial, Z-ized, negative C plate) is desirable. 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 or not 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). When the liquid crystal cell has a phase difference, it is desirable that the liquid crystal cell has a phase difference on both the upper and lower sides. When there is no phase difference, or when the A plate is on the upper side and the positive C plate is 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 (uniaxial, Z conversion, positive C plate, positive A plate) are desirable.

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

  The surface of the transparent protective film where the polarizer is not adhered (the surface on which the easy adhesion layer is not provided) is subjected to a hard coat layer, antireflection treatment, anti-sticking treatment, or treatment for diffusion or anti-glare. There may be.

  An optical film in which the optical layer is laminated on a 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 other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various 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, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. 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 a polarizing plate or an optical film 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 polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film 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.

  Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

(Polarizer)
A polyvinyl alcohol film having an average polymerization degree of 2400, a saponification degree of 99.9 mol%, and a thickness of 75 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Subsequently, the film was stretched to 3.5 times while dyeing in an iodine solution of 0.3 wt% (weight ratio: iodine / potassium iodide = 0.5 / 8) at 30 ° C. for 1 minute. Thereafter, the total draw ratio was stretched to 6 times while being immersed in a 4% by weight boric acid aqueous solution at 65 ° C. for 0.5 minutes. After stretching, drying was performed in an oven at 70 ° C. for 3 minutes to obtain a polarizer having a thickness of 26 μm. The moisture content of the polarizer was 13.5% by weight.

(Transparent protective film)
A lactonized polymethyl methacrylate film (lactonization rate 20%, thickness 30 μm, Re = 0 nm, Rth = 0 nm) was used.

(Phase difference value)
The phase difference value was measured using a phase difference meter based on the parallel Nicol rotation method (manufactured by Oji Scientific Instruments, product name “KOBRA21-ADH”) at a wavelength of 590 nm, nx, ny , Nz, and film thickness (d), front phase difference Re, thickness direction phase difference Rth, and Nz were determined. [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. ].

Example 1
(Adhesive for polarizing plate)
A polarizing plate adhesive was prepared by blending 100 parts by weight of 2-hydroxyethyl acrylate and 11 parts by weight of ditrimethylolpropane tetraacrylate (manufactured by Sartomer Japan, trade name SR355).

(Creation of polarizing plate)
A transparent protective film with an adhesive, wherein the adhesive is coated on the transparent protective film to a thickness of 5 μm using a micro gravure coater (gravure roll: # 300, rotational speed 140% / line speed). It was. Subsequently, the transparent protective film with an adhesive was bonded to this from both sides of the polarizer by a roll machine. An electron beam was irradiated from the bonded transparent protective film side (both sides) to obtain a polarizing plate having a transparent protective film on both sides of the polarizer. The line speed was 20 m / min, the acceleration voltage was 250 kV, and the irradiation dose was 20 kGy.

Examples 2-9, Comparative Examples 1-4
In Example 1, the preparation of the adhesive for polarizing plate was the same as Example 1 except that the monofunctional monomer (A), the type of the polyfunctional monomer, or the amount used thereof was changed as shown in Table 1. Then, a polarizing plate adhesive was prepared, and a polarizing plate was prepared using the adhesive.

[Evaluation]
The following evaluation was performed about the polarizing plate obtained by the Example and the comparative example. The results are shown in Table 1.

<Water resistance>
The obtained polarizing plate was cut into a size of 25 mm × 150 mm to obtain a sample. After immersing the sample in warm water at 60 ° C. for 6 hours, the amount of peeling (mm) from the end of the polarizing plate was measured. The amount of peeling is preferably 10 mm or less.

<Adhesive strength>
The obtained polarizing plate was cut into a size of 15 mm × 150 mm to obtain a sample. The sample was affixed on the glass plate with a double-sided adhesive tape (Nitto Denko Corporation, No. 500). The sample (polarizing plate) is preliminarily provided with a gap between the transparent protective film and the polarizer. It was measured. The measurement conditions were normal temperature (23 ° C.), peel angle: 90 degrees, and peel speed: 3000 mm / min. A value obtained by averaging data between 50 mm and 100 mm of the obtained measurement data is shown. An adhesive having a peel strength of 2 N / 15 mm or more is good.

In Table 1,
HEAA: N-hydroxyethylacrylamide,
ACMO: N-acryloylmorpholine,
AAm: acrylamide,
SR355: ditrimethylolpropane tetraacrylate (manufactured by Sartomer Japan, trade name SR355),
SR295: Pentaerythritol tetraacrylate (manufactured by Sartomer Japan, trade name SR355),
SR338F: 1,6-hexanediol diacrylate (manufactured by Sartomer Japan, trade name SR338F),
SR833: Tricyclodecane dimethanol diacrylate (manufactured by Sartomer Japan, trade name SR833),
CN996: Polyfunctional aliphatic urethane acrylate (manufactured by Sartomer Japan, trade name CN996).

Claims (10)

An active energy ray-curable adhesive for polarizing plates used for providing a transparent protective film on at least one side of a polarizer,
The polarizing plate adhesive is
A monofunctional monomer (A) containing an N-substituted amide monofunctional monomer (a) having a hydroxyl group and a non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups An adhesive for polarizing plates, characterized by:   2. The polarizing plate according to claim 1, wherein the non-urethane polyfunctional monomer (b) having at least two (meth) acrylate groups is a hydrocarbon-based or hydrocarbon ether-based polyfunctional monomer. adhesive.   The ratio of the monofunctional monomer (A) is 20 to 99.5 parts by weight with respect to 100 parts by weight of the total amount of the monofunctional monomer (A) and the polyfunctional monomer (b), and the polyfunctional monomer (b) The adhesive for polarizing plates according to claim 1, wherein the ratio is 0.5 to 80 parts by weight.   The ratio of the N-substituted amide monofunctional monomer (a) having a hydroxyl group to the total amount of 100 parts by weight of the monofunctional monomer (A) and the polyfunctional monomer (b) is 20 parts by weight or more. The adhesive for polarizing plates of Claim 3 characterized by these.   The adhesive for polarizing plate according to claim 1, wherein the active energy ray curable type is an ultraviolet ray curable type or an electron beam curable type.   It is a polarizing plate by which the transparent protective film is provided in the at least one surface of the polarizer through the adhesive bond layer, Comprising: The said adhesive bond layer adhesive for polarizing plates in any one of Claims 1-5 A polarizing plate characterized by being formed by the following.   The polarizing plate according to claim 6, wherein the transparent protective film is at least one selected from a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, and a (meth) acrylic resin. The method for producing a polarizing plate according to claim 6 or 7, wherein a transparent protective film is provided on at least one surface of the polarizer via an adhesive layer,
After apply | coating the adhesive agent for polarizing plates in any one of Claims 1-5 on the surface which forms the said adhesive bond layer of the said polarizer, and / or the surface which forms the said adhesive bond layer of the said transparent protective film, Bonding the polarizer and the transparent protective film;
Next, a step of curing the adhesive by active energy ray irradiation to form an adhesive layer,
The manufacturing method of the polarizing plate characterized by having.   8. An optical film, wherein at least one polarizing plate according to claim 6 or 7 is laminated. An image display device comprising the polarizing plate according to claim 6 or 7, or the optical film according to claim 9.