TWI435124B - Adhesive type polarizing plate and image display device - Google Patents

Description

Adhesive polarizing plate and image display device

The present invention relates to an adhesive polarizing plate having an adhesive layer on at least a single-layer layer of a polarizing plate, and an image display device using the same.

The liquid crystal display device has a configuration in which a liquid crystal panel in which at least one side of a liquid crystal cell is disposed with a polarizing plate and a light source such as a backlight are combined. Usually, the liquid crystal cell and the polarizing plate are laminated via an adhesive layer. Further, in an organic EL (Electro-Luminescence) display device, in order to shield the specular reflection of external light, a circular polarizing plate is bonded to the viewing side of the unit via an adhesive layer. When the image display device using the polarizing plate described above is used for practical use, especially when used in an environment of high temperature and high humidity, light leakage may occur at the end portion of the screen.

It is considered that the light leakage accompanying the environmental change is caused by a change in the size of each member due to a change in temperature, humidity, etc., and the phase difference of each member constituting the polarizing plate changes due to the stress at the interface. . That is, the reason for this is considered to be that the polarizing plate usually has a configuration in which a transparent protective film is laminated on the polarizing element via an adhesive, but the interface between the transparent protective film and the polarizing element and the transparent protection as the environment changes. The interface between the film and other members bonded to the transparent protective film generates stress, and the phase difference characteristic of the transparent protective film changes due to the photoelastic birefringence caused by the stress. In particular, at the end portion of the screen, since the dimensional change of each member is larger than the central portion of the screen, light leakage at the end portion tends to be conspicuous.

In addition, with the trend of increasing the size and brightness of image display devices in recent years, there is a tendency that the temperature inside the image display device rises due to heat generation of the light source. Further, there are various applications in which a thin image display device such as a liquid crystal display device or an organic EL display device is used, and the chance of being used in a severe environment such as high temperature and high humidity tends to increase. Therefore, light leakage at the end of the screen accompanying environmental changes is more easily recognized.

In order to suppress the light leakage at the end of the screen, a method of reducing the phase difference of the transparent protective film by using a transparent protective film having a small absolute value of the photoelastic coefficient has been proposed (for example, Patent Document 1). Further, it has been proposed to reduce the difference in tensile elastic modulus between the mechanical direction and the direction perpendicular to the mechanical direction in the production of the transparent protective film (for example, Patent Document 2), or to increase the coefficient of linear expansion and adhesion of the transparent protective film. The method of reducing the phase difference of the transparent protective film by setting the product of the elastic modulus of the agent layer to a specific range (for example, Patent Documents 3 and 4).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-352619

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-217021

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-122739

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2002-122740

As described in Patent Document 1, etc., the viewpoint of suppressing the change in the phase difference of the transparent protective film caused by the environment and suppressing the light leakage at the end portion of the screen is It is preferable that the absolute value of the photoelastic coefficient of the protective film is small, and it is theoretically considered that the problem of light leakage can be eliminated by using a transparent protective film having a photoelastic coefficient of substantially zero. However, according to the study by the inventors of the present invention, it is clarified that even when a transparent protective film having a small absolute value of the photoelastic coefficient is used, light leakage at the end of the screen accompanying the change in the use environment occurs.

In view of the above problems, an object of the present invention is to provide an adhesive polarizing plate which is less likely to cause light leakage of an image display device even when the use environment changes, and an image display device using the same.

The present inventors have studied the cause of light leakage even in the case of using a transparent protective film having a small photoelastic coefficient, and as a result, found a new finding by changing the adhesive layer of the laminated polarizing plate and the liquid crystal cell. The type can change the condition of light leakage. In addition, based on this finding, the research is based on the following estimation principle, that is, the light leakage in the use environment of the image display device is not only caused by the phase difference change of the transparent protective film, but also due to the phase difference of the adhesive layer, and it is found that The present invention can be completed by suppressing light leakage by a combination of a specific transparent protective film and an adhesive layer.

The present invention relates to an adhesive polarizing plate in which at least a single-layer layer of a polarizing element has a transparent protective film, and an adhesive layer is laminated on a side of the transparent protective film which is not laminated with the polarizing element. The above adhesive layer is formed of an adhesive containing an acrylic polymer containing an alkyl (meth)acrylate and a (meth) acrylate having an aromatic ring structure as a monomer unit.

The absolute value of the photoelastic coefficient X (m ² /N) of the transparent protective film is 50 × 10 ^-12 or less. In addition, when the content of the (meth) acrylate monomer unit having an aromatic ring structure in the acrylic polymer constituting the pressure-sensitive adhesive layer is Y%, X and Y satisfy the following formula.

-1×10 ¹¹ X+3≦Y≦-1×10 ¹¹ X+23

In the adhesive polarizing plate of the present invention, the transparent protective film preferably contains an acrylic resin, a cyclic olefin resin, a phenyl maleimide resin, a cellulose resin, and a modification. At least one resin selected from the group consisting of polycarbonate resins.

Further, the present invention relates to an image display device using the above-described adhesive polarizing plate.

In the adhesive polarizing plate of the present invention, the acrylic polymer constituting the adhesive layer contains a specific amount of a (meth) acrylate monomer unit (component B) having an aromatic ring structure. The content Y of the component B can be determined according to the value of the photoelastic coefficient X of the transparent protective film. When the phase difference of the transparent protective film is changed due to environmental changes such as heating, the adhesive layer can be produced and transparently protected. The phase difference of the opposite sign of the film is changed in such a manner as to change.

According to the above configuration, the phase difference of the adhesive layer is also changed in the vicinity of the end portion of the screen where the phase difference of the transparent protective film is largely changed (wherein the phase difference of the adhesive layer changes with the phase difference of the transparent protective film) In contrast, in the entire surface of the adhesive polarizing plate, the phase difference change of the transparent protective film and the phase difference change of the adhesive layer cancel each other. Therefore, the image display device to which the adhesive polarizing plate of the present invention is bonded can realize image display with less light leakage even when exposed to a heating environment or the like.

Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, the adhesive polarizing plate 10 of the present invention includes a first transparent protective film 2 on one surface of a polarizing element 1, and an adhesive layer 5 on the transparent protective film 2. The polarizing element 1 and the first transparent protective film 2 are laminated via an adhesive layer (not shown). Moreover, it is preferable that the second transparent protective film 3 is laminated on the surface of the polarizing element 1 on the side opposite to the side on which the first transparent protective film 2 is laminated via an adhesive layer (not shown).

When the image display device 100 is formed by using the adhesive polarizing plate 10 of the present invention, as shown in FIG. 2, the surface on the side where the first transparent protective film 2 is disposed is bonded to the image display via the adhesive layer 5. On unit 20. That is, the first transparent protective film and the adhesive layer 5 are disposed between the image display unit 20 and the polarizing element 1. Further, in FIG. 2, the adhesive display type polarizer 10 is bonded to both surfaces of the image display unit 20, and the adhesive polarizing plate may be attached to only one side of the image display unit 20.

[Polarizing element]

The polarizing element 1 is not particularly limited, and various types can be used. Examples of the polarizing element include adsorption of iodine, dichroic dye, and the like on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene/vinyl acetate copolymer partial saponified film. The dichroic substance is uniaxially stretched, a dehydration treatment of polyvinyl alcohol, a polyene-based alignment film such as a dechlorination treatment of polyvinyl chloride, or the like. Among them, a polarizing element comprising a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of the polarizing elements is not particularly limited, but is usually about 5 to 80 μm.

Dyeing of polyvinyl alcohol film with iodine and uniaxial stretching The optical element can be produced, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine to carry out dyeing and extending to 3 to 7 times the original length. If necessary, it may be immersed in boric acid or an aqueous solution containing potassium iodide such as zinc sulfate or zinc chloride. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, the surface of the polyvinyl alcohol-based film can be washed with dirt or an anti-caking agent, and the polyvinyl alcohol-based film can be swollen to prevent unevenness in dyeing unevenness. The extension may be carried out after dyeing with iodine, or may be extended on one side of the dyeing, and may also be dyed with iodine after stretching. It can also be extended in an aqueous solution or a water bath such as boric acid or potassium iodide.

[Transparent protective film]

As the first transparent protective film 2 disposed on one main surface of the polarizing element, the absolute value of the photoelastic coefficient can be 50×10 ^-12 m ² /N or less. When the photoelastic coefficient is too large, when stress is applied to the first protective film, there is a tendency that unevenness is likely to occur in image display. Further, the photoelastic coefficient can be used to determine the phase difference value in the case where a specific tension is applied to the film, and is obtained from the slope obtained by plotting the stress and the phase difference. Regarding the sign of the photoelastic coefficient, when the tensile stress is given, the phase difference increase is defined as positive, and the phase difference decrease is defined as negative.

(material)

The material for forming the first transparent protective film is not particularly limited as long as the photoelastic coefficient is in the above range, and is preferably excellent in transparency, mechanical strength, thermal stability, water barrier properties, isotropy, and the like. As a material for forming the first transparent protective film, a cyclic polyolefin resin or an acrylic tree can be preferably used. A fat, a phenyl maleimide-based resin, a cellulose resin, a modified polycarbonate resin, or the like.

The above-mentioned cyclic polyolefin-based resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit, and examples thereof include Japanese Patent Laid-Open No. Hei No. 1-240517, Japanese Patent Laid-Open No. Hei No. Hei No. 3-148882, and Japanese Patent No. The resin described in Kaikai No. 3-122137 or the like. Specific examples thereof include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (typically random). a copolymer) and a graft modified product obtained by modifying the unsaturated carboxylic acid or a derivative thereof, and the like. Specific examples of the cyclic olefin include a norbornene-based monomer.

Examples of the norbornene-based monomer include norbornene, an alkyl group thereof, and/or an alkylene substituent. Further, as the cyclic polyolefin-based resin, other cyclic olefins which can be subjected to ring-opening polymerization other than the above can be used in combination within the range not impairing the object of the present invention.

Various products are commercially available as the above cyclic polyolefin resin. Specific examples include the product names "Zeonex" and "Zeonor" manufactured by JAPAN ZEON, the product name "Arton" manufactured by JSR, the product name "Topas" manufactured by TICONA, and the product name "Apel" manufactured by Mitsui Chemicals.

Examples of the acrylic resin include poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, and methyl methacrylate-(meth)acrylate. Copolymer, methyl methacrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example) Methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, a poly(meth)acrylic acid C1-6 alkyl ester such as poly(methyl) acrylate is used. More preferably, the methyl (meth) acrylate resin containing methyl (meth) acrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

Specific examples of the acrylic resin include, for example, an acrylic resin having a ring structure in the molecule described in the Japanese Patent Publication No. 2004-70296, the ACRYPET VH or the ACRYPET VRL20A manufactured by Mitsubishi Rayon. A high Tg acrylic resin obtained by intramolecular crosslinking or intramolecular cyclization.

Further, as the acrylic resin, a (meth)acrylic resin having a lactone ring structure can also be preferably used. The (meth)acrylic resin having a lactone ring structure is preferred in terms of high heat resistance, high transparency, and high mechanical strength by biaxial stretching.

Examples of the (meth)acrylic resin having a lactone ring structure include JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, and JP-A. A (meth)acrylic resin having a lactone ring structure described in JP-A-2005-146084, and the like.

The phenyl maleimide-based resin may be one obtained by polymerizing a monomer having a substituted or unsubstituted phenyl group bonded to a nitrogen atom of maleimide. Examples of the raw material monomer of the phenyl maleic acid imide resin include N-phenyl maleimide and N-(2-methylphenyl) maleimide. , N-(2-ethylphenyl) maleimide, N-(2-propylphenyl)maleimide, N-(2-isopropylphenyl)maleimide, N-(2,6-dimethylphenyl) Maleimide, N-(2,6-dipropylphenyl)maleimide, N-(2,6-diisopropylphenyl)maleimide , N-(2-methyl-6-ethylphenyl) maleimide, N-(2-chlorophenyl) maleimide, N-(2,6-dichloride Phenyl) maleimide, N-(2-bromophenyl)maleimide, N-(2,6-dibromophenyl)maleimide, N- (2-biphenyl) maleimide, N-(2-cyanophenyl) maleimide, and the like. The above maleimide-based monomer can be obtained, for example, from Tokyo Chemical Industry Co., Ltd. or the like.

Further, in order to improve brittleness, moldability, heat resistance and the like, the phenyl maleimide-based resin may be a material obtained by copolymerizing a monomer other than the phenyl maleimide-based monomer. Examples of other monomer components used for the above purpose include ethylene, propylene, 1-butene, 1,3-butadiene, 2-methyl-1-butene, and 2-methyl-1- An olefin such as pentene or 1-hexene, acrylonitrile, methyl acrylate, methyl methacrylate, maleic anhydride, vinyl acetate or the like. The above phenyl maleimide-olefin copolymer is available, for example, from Tosoh Corporation.

The cellulose resin is preferably an ester of cellulose and a fatty acid. Specific examples of the cellulose ester include triethyl fluorenyl cellulose, diethyl fluorenyl cellulose, tripropyl fluorenyl cellulose, and dipropyl fluorenyl cellulose. Among them, it is especially preferred to be triethylsulfonyl cellulose.

Moreover, as a film containing a cellulose resin, a commercial item can also be used. Examples of the commercially available product of the triethylenesulfonated cellulose film include Fujifilm (product name "UV-50", "UV-80", "SH-80", and "TD-80U" manufactured by Fujifilm. , "TD-TAC", "UZ-TAC", or "KC Series" made by Konica Minolta.

As the modified polycarbonate resin, in addition to 4,4'-(propane-2,2-diyl)diphenol (bisphenol A), the bisphenol component may contain a bisphenol component which exhibits negative birefringence. The photoelastic coefficient is reduced as a monomer unit. As such a bisphenol component which exhibits a negative birefringence of the modified polycarbonate, for example, a bisphenol having a fluorene structure can be mentioned.

As the above-mentioned modified polycarbonate resin, for example, Japanese Patent Laid-Open Publication No. 2001-194530, Japanese Patent Laid-Open No. 2001-139676, No. WO 01/081959 International Publication No. WO WO 01/041190 The polycarbonate resin described in the specification and the like.

As a film containing a modified polycarbonate resin, a commercial item can also be used. As such a modified polycarbonate film, for example, the product name "PURE-ACE WR series" manufactured by Teijin Chemical Co., Ltd., and the like can be mentioned.

The first transparent protective film 2 may be an optically isotropic film having substantially no phase difference, or may be an optically anisotropic film having a phase difference. However, since it is disposed between the image display unit 20 and the polarizing element 1, Therefore, it is preferable that the phase difference is small and the optical uniformity is high. When the optically anisotropic film is used as the first transparent protective film, the first transparent protective film functions as a protective film for the polarizing element and functions as a phase difference plate. For example, when the adhesive polarizing plate of the present invention is used in a liquid crystal display device, the first protective film functions as an optical compensation film. Further, when the adhesive polarizing plate of the present invention is used in an organic EL display device, a circular polarizing plate can be produced by using a quarter-wave plate as the first protective film.

The thickness of the first transparent protective film can be appropriately determined, and it is usually about 1 to 500 μm in terms of workability such as strength and workability, and film properties. Especially good is 5~200μm.

When the second transparent protective film 3 is included in the adhesive polarizing plate, the second protective film is not particularly limited, but a transparent film excellent in transparency, mechanical strength, thermal stability, water barrier, and the like is preferably used. As a material for forming the second protective film, those exemplified as the material for forming the first protective film can be preferably used.

The surface of the second transparent protective film that is not attached to the polarizing element may be subjected to a treatment such as hard coating or anti-reflection treatment, anti-adhesion, diffusion or anti-glare. The antireflection layer, the anti-adhesion layer, the diffusion layer, the antiglare layer, and the like may be provided as the transparent protective film itself, or may be provided as a separate optical layer different from the transparent protective film.

It is preferable that the polarizing element 1 and the transparent protective films 2 and 3 are laminated using an adhesive. As the adhesive, a water-based adhesive or the like can be preferably used. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, an ethylene-based latex, an aqueous polyurethane, and an aqueous polyester. Further, when the polarizing element and the transparent protective film are bonded, the transparent protective film can be subjected to an activation treatment. The activation treatment may be carried out by various methods such as saponification treatment, corona treatment, low pressure UV treatment, plasma treatment, and the like.

[Adhesive layer]

The adhesive layer 5 is formed of an adhesive. As the matrix polymer of the adhesive, an acrylic system containing a (meth)acrylic acid alkyl ester monomer unit (component A) and a (meth) acrylate monomer unit (component B) having an aromatic ring structure can be used. polymer. Furthermore, in the scope of this specification and the patent application, "(A The term "acrylic ester" means "acrylate and/or methacrylate".

The content Y (%) of the (meth) acrylate (component B) having an aromatic ring structure in the acrylic polymer as the matrix polymer is relative to the photoelastic coefficient X (m ² /N) of the first transparent protective film. , satisfying -1 × 10 ¹¹ X + 3 ≦ Y ≦ - 1 × 10 ¹¹ X + 23.

In the present invention, the content Y of the component B is set to the above range so that the absolute value of the change in the phase difference of the adhesive polarizing plate when exposed to a heating environment is reduced. The smaller the absolute value of the phase difference change of the adhesive polarizing plate, the better. Specifically, the phase difference change is preferably within ±2 nm, and more preferably within ±1 nm.

In this way, the (meth) acrylate having an aromatic ring structure in the acrylic polymer is reduced in terms of reducing the phase difference change of the adhesive polarizing plate and suppressing light leakage at the end of the screen of the image display device. The content Y (%) is preferably -1 × 10 ¹¹ X + 4 or more, more preferably -1 × 10 ¹¹ X + 5 or more, still more preferably -1 × 10 ¹¹ X + 6 or more. Further, Y is preferably -1 × 10 ¹¹ X + 21 or less, more preferably -1 × 10 ¹¹ X + 20 or less, still more preferably - 1 × 10 ¹¹ X + 19 or less. In this manner, by adjusting the content Y of the B component in the acrylic polymer corresponding to the value of the photoelastic coefficient X of the first transparent protective film, the photoelastic birefringence of the transparent protective film can be offset by the birefringence of the adhesive layer. And the phase difference of the entire adhesive polarizing plate is reduced. Further, the absolute value of the photoelastic coefficient X (m ² /N) of the first transparent protective film is preferably 30 × 10 ^-12 or less, more preferably 20 × 10 ^-12 or less, still more preferably 10 × 10 ^-12 the following.

The alkyl group of the (meth)acrylic acid alkyl ester (component A) in the acrylic polymer forming the adhesive layer has a carbon number of about 1 to 18, preferably a carbon number of 1 to 9, and the alkyl group may be a linear chain. Any of the branches. As a (meth)acrylic acid alkyl ester Examples of the method include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. Isobutyl acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, (meth) acrylate Octyl ester, decyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and the like. These may be used singly or in combination. The average carbon number of the alkyl groups is preferably from 4 to 12.

Examples of the aromatic ring structure of the (meth) acrylate (component B) having an aromatic ring structure in the acrylic polymer forming the pressure-sensitive adhesive layer include a benzene ring, a naphthalene ring, a thiophene ring, a pyridine ring, and a pyrrole ring. Furan ring and the like. Examples of the (meth) acrylate having an aromatic ring structure include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and phenoxy-2-hydroxypropyl (meth)acrylate. , phenol ethylene oxide modified (meth) acrylate, 2-naphthyloxyethyl (meth) acrylate, 2-(4-methoxy-1-naphthalenyloxy) (meth) acrylate , phenoxypropyl (meth)acrylate, phenoxyethylene (meth) acrylate, thiophene (meth) acrylate, pyridyl (meth) acrylate, pyrrolyl (meth) acrylate, ( Phenyl methacrylate, styrene poly(meth)acrylate, and the like.

In this manner, the reason why the change in phase difference can be reduced by causing the acrylic polymer to contain a specific amount of the (meth) acrylate component (component B) having an aromatic ring structure is not determined, but it is presumed that Since the B component has an aromatic ring structure having a high polarizability in the side chain, the birefringence tends to be significantly different from the alkyl (meth)acrylate component (component A).

Further, the acrylic polymer constituting the adhesive is composed of the above A component and B. In addition to the fraction, other monomer units (component C) may be contained as a monomer unit.

Examples of the C component include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyl (meth)acrylate. Hexyl ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate or (4-hydroxymethylcyclohexyl)-methyl (acrylic acid) a monomer containing a hydroxyl group such as an ester; (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, croton a monomer having a carboxyl group such as an acid; an acid anhydride group-containing monomer such as maleic anhydride or itaconic anhydride; a caprolactone adduct of acrylic acid; allylsulfonic acid and 2-(meth)acrylamide- a monomer containing a sulfonic acid group such as 2-methylpropanesulfonic acid, (meth)acrylamide, propanesulfonic acid or sulfopropyl (meth)acrylate; and a phosphate group such as 2-hydroxyethylpropenyl phosphate Monomers, etc.

Further, examples of the C component include a nitrogen-containing vinyl monomer. For example, the following monomer may be cited as a monomer for modification purposes: maleimide, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N - diethyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-butyl (N-substituted) guanamine monomer such as (meth) acrylamide or N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide; (methyl Aminoethyl acrylate, aminopropyl (meth) acrylate, N,N-dimethylaminoethyl (meth) acrylate, tert-butylaminoethyl (meth) acrylate, etc. Alkylaminoalkyl acrylate monomer; methoxyethyl (meth) acrylate, alkoxyalkyl (meth) acrylate, etc. ;N-(methyl) Propylene methoxymethylene succinimide, N-(methyl) propylene fluorenyl-6-oxyhexamethylene succinimide, N-(methyl) propylene fluorenyl-8-oxy VIII An amber quinone imine monomer such as methylene amber imine.

Further, as the component C, vinyl such as vinyl acetate, vinyl propionate, N-vinylcarboxylic acid decylamine, styrene, α-methylstyrene or N-vinyl caprolactam may be used. Monomer; nitrile monomer such as acrylonitrile or methacrylonitrile; epoxy group-containing acrylic monomer such as glycidyl (meth)acrylate; polyethylene glycol (meth) acrylate or polypropylene glycol ( a diol-based acrylate monomer such as methyl acrylate, methoxyethylene glycol (meth) acrylate or methoxy polypropylene glycol (meth) acrylate; fluorine (meth) acrylate, polyoxyl A (meth) acrylate monomer such as (meth) acrylate or 2-methoxyethyl acrylate.

In order to modify the matrix polymer, the above C component can be used arbitrarily. One or two or more kinds of the above C components can be used. The ratio of the component C is preferably 10% by weight or less, and more preferably 6% by weight or less, as the monomer unit in the acrylic polymer. When the ratio of the component C exceeds 10% by weight, the flexibility as an adhesive may be impaired.

As the above-mentioned component C, a monomer having a carboxyl group, particularly acrylic acid, can be preferably used in terms of good adhesion. In the case of using a monomer having a carboxyl group, the ratio thereof is about 0.1 to 10% by weight, preferably 0.5 to 8% by weight, and more preferably 1 to 6% by weight. Further, since it can be a crosslinking point with an isocyanate crosslinking agent, a monomer having a hydroxyl group can be preferably used. In the case of using a monomer having a hydroxyl group, the ratio thereof is about 0.1 to 10% by weight, preferably 0.5 to 8% by weight, and more preferably 1 to 6% by weight.

The above acrylic polymer can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo-based or peroxide-based compounds can be used. The reaction temperature is usually set to about 50 to 80 ° C, and the reaction time is set to 1 to 8 hours. Further, in the above production method, a solution polymerization method is preferred, and as the solvent of the acrylic polymer, ethyl acetate, toluene or the like can be usually used. The solution concentration is usually set to about 20 to 80% by weight. Further, the acrylic polymer can be obtained in the form of an aqueous emulsion.

The weight average molecular weight of the acrylic polymer is preferably from 1,000,000 to 3,000,000. The weight average molecular weight of the acrylic polymer is more preferably from 2,000,000 to 3,000,000, and further preferably from 2.1 million to 2.7 million. When the weight average molecular weight is too small, birefringence which cancels the degree of birefringence of the transparent protective film on the adhesive layer may not occur, and the suppression of light leakage may be insufficient. On the other hand, when the weight average molecular weight exceeds 3,000,000, the adhesiveness tends to decrease.

The adhesive forming the adhesive layer of the present invention may contain a crosslinking agent in addition to the above acrylic polymer as a matrix polymer. The adhesion and durability to the optical film can be improved by the crosslinking agent, and the reliability at high temperatures and the shape retention of the adhesive itself can be achieved. As the crosslinking agent, an isocyanate type, an epoxy type, a peroxide type, a metal chelate type, or the like can be suitably used. Oxazoline and the like. These crosslinking agents can be used alone or in combination of two or more. The crosslinking agent is preferably a crosslinking agent containing a functional group reactive with a hydroxyl group, and particularly preferably an isocyanate crosslinking agent.

The amount of the crosslinking agent used is 10 parts by weight or less, preferably 0.01 to 5 parts by weight, more preferably 0.02 to 3 parts by weight, per 100 parts by weight of the base polymer. When the ratio of use of the crosslinking agent exceeds 10 parts by weight, the crosslinking tends to proceed excessively and the adhesion tends to decrease.

In the adhesive, if necessary, an adhesive imparting agent, a plasticizer, a glass fiber, a glass bead, a metal powder, a filler containing other inorganic powder, a pigment, and a coloring can be suitably used without departing from the object of the present invention. Various additives such as a agent, a filler, an antioxidant, a UV absorber, and a decane coupling agent. Further, an adhesive layer containing fine particles and exhibiting light diffusibility may be formed.

As the above additive, a decane coupling agent is preferred. Examples of the decane coupling agent include 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, and 2-(3,4-epoxycyclohexyl). a decane coupling agent having an epoxy structure such as ethyltrimethoxydecane; 3-aminopropyltrimethoxydecane, N-(2-aminoethyl) 3-aminopropyltrimethoxydecane, N -(2-Aminoethyl) 3-aminopropylmethyldimethoxydecane, 3-triethoxydecyl-N-(1,3-dimethylbutylidene)propylamine, etc. Alkylene-based decane coupling agent; 3-methacryloxypropyltrimethoxydecane, 3-methylpropenyloxypropyltriethoxydecane, etc. 3-octane cyanide-containing decane coupling agent such as 3-isocyanate propyl triethoxy decane; 3-chloropropyltrimethoxydecane; trimethoxydecane containing acetamidine. The decane coupling agent may be used singly or in combination of two or more. The amount of the decane coupling agent is 0.01 to 2 parts by weight, preferably 0.02 to 1 by weight based on 100 parts by weight of the acrylic polymer. Share.

[Formation of Adhesive Polarizing Plate]

The adhesive polarizing plate 10 of the present invention can be produced by forming an adhesive layer on the first transparent protective film 2 with the above-mentioned adhesive. The formation of the adhesive layer and There is no particular limitation, and a method of applying an adhesive solution by a suitable spreading method such as a casting method or a coating method on a transparent protective film and drying it; and transferring it by a release sheet provided with an adhesive layer The method of printing, etc. The coating method may be a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a spray coating method, a dip coating method, a spray coating method, or the like. After the application of the adhesive solution, the solvent or water is volatilized in the drying step, thereby obtaining an adhesive layer of a specific thickness.

The thickness of the adhesive layer can be appropriately determined depending on the purpose of use or the adhesion, and is usually 1 to 500 μm, preferably 1 to 50 μm. More preferably, it is 1 to 40 μm, further preferably 5 to 30 μm, and particularly preferably 10 to 25 μm. When it is thinner than 1 μm, durability is deteriorated, and if it is thick, it is likely to be swelled or peeled off by foaming or the like, and it is likely to cause poor appearance.

Further, in the formation of the adhesive layer, the UV-curable adhesive syrup can be applied to the release film and irradiated with radiation such as an electron beam or UV to form the acrylic polymer. Adhesive layer. At this time, since the adhesive contains a crosslinking agent, the reliability at a high temperature and the shape retention of the adhesive itself can be achieved.

Further, in addition to the drying step and the UV irradiation step, the crosslinking of the adhesive layer may be selected to promote cross-linking such as crosslinking by drying in a heated state or at room temperature after drying. .

Before the exposed surface of the adhesive layer 5 of the adhesive polarizing plate of the present invention is attached to an image display unit or the like for practical use, it is preferable to temporarily cover the separator for the purpose of preventing contamination of the adhesive layer or the like. . Thereby, contact with the adhesive layer in a normal operation state can be prevented. As a partition, For example, a plastic film, a rubber sheet, a paper, a cloth, a non-woven fabric, a mesh, a foamed sheet or a metal foil, and a laminate such as the laminate may be used, and if necessary, it may be used in the form of polyfluorene or long. A suitable release agent such as an alkyl group, a fluorine type or a molybdenum sulfide is coated and treated, and the like is based on a material suitable for the prior art.

[Image display device]

The adhesive polarizing plate of the present invention can be preferably used in various image display devices such as a liquid crystal display device or an organic EL display device. The image display device of the present invention can be configured similarly to the conventional image display device except that the adhesive polarizing plate of the present invention is used.

The liquid crystal display device can be manufactured by, for example, assembling an optical member such as a liquid crystal cell, an optical member such as a polarizing plate of the present invention, and an optional illumination system (such as a backlight) into a driving circuit. The configuration of the liquid crystal display device is not particularly limited as long as the adhesive polarizing plate of the present invention can be used on one side or both sides of the liquid crystal cell.

When a liquid crystal display device in which a polarizing plate is disposed on both the viewing side and the light source side of the liquid crystal cell as in the case of a transmissive liquid crystal display device, it is preferable to use a substrate disposed on both sides of the liquid crystal cell from the viewpoint of suppressing light leakage. The composition of the adhesive polarizing plate of the invention.

The organic EL display device can be produced, for example, by disposing the adhesive polarizing plate of the present invention on the viewing side of the organic EL unit (organic light-emitting layer). In particular, as described above, by using a quarter-wave plate as the first transparent protective film, deterioration in visibility due to reflection of external light can be suppressed. Furthermore, it is also possible to use no 1/4 wavelength plate as a transparent protective film, and to additionally deposit 1/4 of the polarizing plate of the present invention. A polarizing plate is formed on the wavelength plate to be disposed on the viewing side of the organic EL unit.

The image display device of the present invention can be used in any suitable application. Examples of the use thereof include OA equipment such as desktop computers, notebook computers, and photocopiers; mobile phones, clocks, digital cameras, personal digital assistants (PDAs), portable game machines, and the like; and home appliances such as cameras, televisions, and electronic stoves. ; rear monitors, car navigation system monitors, car audio equipment and other in-vehicle equipment; commercial shop information monitors and other display equipment; surveillance monitors and other security equipment; nursing monitors, medical monitors and other care / Medical equipment, etc.

[Examples]

Hereinafter, the examples and comparative examples will be further described, but the present invention is not limited to the examples.

[Example 1] (Preparation of adhesive)

97 parts by weight of butyl acrylate, 5 parts by weight of benzyl acrylate and 2,2'-azobisisobutyronitrile were added together with 140 parts by weight of ethyl acetate in a 4-neck flask equipped with a condenser tube, a stirring blade and a thermometer. After 0.1 part by weight, the mixture was purged with nitrogen gas, and the mixture was reacted at 55 ° C for 8 hours while stirring under a nitrogen stream to obtain a solution of an acrylic polymer having a weight average molecular weight of 2,000,000. 0.45 parts by weight of a crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L") was added to the solid content of 100 parts by weight of the solution of the acrylic polymer, and decane was added thereto. 0.1 parts by weight of a coupling agent (manufactured by Shin-Etsu Silicones, trade name "KBM 403") was used to prepare an adhesive solution.

(formation of adhesive layer)

The obtained adhesive solution was applied to the separator including the polyester film (thickness: 38 μm) which had been subjected to the release treatment by a reverse roll coating method so that the thickness of the adhesive layer after drying became 20 μm. The mixture was heat-treated at ° C for 3 minutes to volatilize the solvent to obtain an adhesive layer.

(production of polarizing plate)

A polymer film having a polymerization degree of 2400 and a saponification degree of 99.9 mol% as a main component was stretched and conveyed while being dyed at different peripheral speeds to obtain a polyvinyl alcohol-based polarizing element. First, the polyvinyl alcohol film was immersed in a water bath at 30 ° C for 1 minute to swell, and was extended to 1.2 times in the transport direction, and then immersed in an aqueous solution having a potassium iodide concentration of 0.03 wt% and an iodine concentration of 0.3 wt% at 30 ° C for 1 minute. By this, one side of the dyeing is extended to three times in the conveying direction with respect to the film which is completely unstretched (original length). Subsequently, it was immersed in an aqueous solution having a boric acid concentration of 4% by weight and a potassium iodide concentration of 5% by weight at 60 ° C for 30 seconds, and was extended to 6 times in the transport direction with respect to the original length. Then, the obtained stretched film was dried at 70 ° C for 2 minutes, whereby a polarizing element was obtained. Further, the thickness of the polarizing element was 30 μm.

A modified methyl methacrylate-based resin film (manufactured by Toyo Steel Co., Ltd., trade name "Fine Cast Film RZ-30NA-S", light was bonded to both surfaces of the polarizing element obtained in this manner via a polyvinyl alcohol-based adhesive. Elastic coefficient: 1.5 × 10 ^-12 m ² /N), a polarizing plate in which a transparent protective film is laminated on a polarizing element.

(Production of adhesive polarizer)

The primer was applied to the surface of the transparent protective film of the above polarizing plate by a bar to form an undercoat layer (thickness: 100 nm). The primer is made of polyethyleneimine (day) This catalyst system, EPOMIN P-1000). Then, a release sheet in which the above-mentioned adhesive layer was formed was bonded to the undercoat layer to form an adhesive polarizing plate.

[Examples 2 to 3, Comparative Examples 1 to 4]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1.

[Examples 4 to 6 and Comparative Examples 5 to 8]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1. Further, in the production of the polarizing plate of the first embodiment, a cyclic olefin resin film (manufactured by JAPAN ZEON, trade name "Zeonor Film ZB14-55124", photoelastic coefficient: 4.0 × 10 ^-12 m ² /N) was used instead. A methyl methacrylate resin film is used as a transparent protective film. An adhesive polarizing plate was produced in the same manner as in Example 1 except the above.

[Examples 7 to 9 and Comparative Examples 9 to 12]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1. Further, in the production of the polarizing plate of Example 1, a triethylenesulfonated cellulose film (manufactured by Fujifilm, trade name "FUJITAC TD80UL", photoelastic coefficient: 16 × 10 ^-12 m ² /N) was used instead of the modification. A methyl methacrylate resin film is used as a transparent protective film. An adhesive polarizing plate was produced in the same manner as in Example 1 except the above.

[Examples 10 to 12, Comparative Examples 13 to 16]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1. Further, in the production of the polarizing plate of Example 1, a triethylenesulfonated cellulose film (manufactured by Konica Minolta, trade name "KC4KR-1", photoelastic coefficient: 21.8 × 10 ^-12 m ² /N was used. An alternative modified methyl methacrylate resin film is used as the transparent protective film. An adhesive polarizing plate was produced in the same manner as in Example 1 except the above.

[Examples 13 to 15 and Comparative Examples 17 to 20]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1. Further, in the production of the polarizing plate of Example 1, a phenyl maleimide-based resin film (manufactured by Tosoh Corporation, trade name "TI-160α", and a photoelastic coefficient: -14 was used. ×10 ^-12 m ² /N) Instead of the modified methyl methacrylate resin film as a transparent protective film. An adhesive polarizing plate was produced in the same manner as in Example 1 except the above.

[Examples 16 to 18, Comparative Examples 21 to 24]

An adhesive solution was prepared in the same manner as in Example 1 except that the addition ratio of butyl acrylate to benzyl acrylate was changed in the preparation of the adhesive of Example 1. Further, in the production of the polarizing plate of Example 1, a modified polycarbonate film (manufactured by Teijin Chemical Co., Ltd., trade name "PURE-ACE WR", photoelastic coefficient: -30 × 10 ^-12 m ² /N) was used instead. The modified methyl methacrylate resin film was used as a transparent protective film. An adhesive polarizing plate was produced in the same manner as in Example 1 except the above.

[Production of LCD panel]

A liquid crystal panel (manufactured by Sony, trade name "BRAVIA") containing a liquid crystal cell of VA (Vertical Alignment) and IPS (In-Plane Switching) mode is used to remove the liquid crystal panel, and the polarizing plate disposed above and below the liquid crystal cell is removed. Wash the glass surface (surface and back) of the liquid crystal cell. Then, the adhesive polarizing plates produced in the above respective Examples and Comparative Examples were bonded to both surfaces of the liquid crystal cell.

[Evaluation] (Measurement of brightness in the center of the screen and the corner of the screen)

The liquid crystal panel to which the adhesive polarizing plates of the respective examples and comparative examples were bonded was placed in an air circulating type thermostatic chamber at 95 ° C for 24 hours, and then the liquid crystal panel was taken out and placed on a backlight having a brightness of 10000 cd/m ^{2 to} be placed thereon. The black color is displayed, and the luminance in the front direction of the center portion of the screen and the corner portion (four corners) of the screen is measured by a luminance measuring device (manufactured by TOPCON, trade name "BM-5A").

(Measurement of in-plane brightness deviation)

Further, the liquid crystal panel placed in an air circulating type thermostatic chamber at 95 ° C for 24 hours was placed on a backlight having a brightness of 10000 cd/m ² to display black, and the in-plane luminance measuring device (product name: I-SYSTEM) "Eye Scale-4W") measures the in-plane brightness of the screen.

The measurement results of the brightness are shown in Table 1 together with the adhesive composition of the adhesive polarizing plate of each of the examples and the comparative examples and the photoelastic coefficient of the transparent protective film. In addition, in Table 1, X represents the photoelastic coefficient of the transparent protective film, and Y represents the content (% by weight) of the (meth) acrylate monomer unit having an aromatic ring structure in the acrylic polymer constituting the adhesive. . Further, the brightness of the corner portion is the average value of the corners of the screen, and the "brightness difference" indicates the difference between the center portion and the corner portion of the screen. Table 1 represents the variation of △ σ inner surface of the front of the high temperature test input luminance deviation σ _0h inner surface of the rear of the high-temperature test [sigma] input luminance difference △ _24h of σ = σ _24h -σ _0h.

As shown in Table 1, it is understood that in the liquid crystal display device using the adhesive polarizing plate of the embodiment, the difference in luminance between the center and the corner of the screen is small, and variations in the in-plane luminance before and after the heating test are also suppressed. So, using the present invention The liquid crystal display device of the adhesive type polarizing plate is less likely to cause light leakage and brightness change caused by changes in the use environment.

1‧‧‧Polarized elements

2, 3‧‧‧ transparent protective film

5‧‧‧Adhesive layer

10‧‧‧Adhesive polarizer

20‧‧‧Image display unit

100‧‧‧Image display device

1 is a schematic cross-sectional view showing an adhesive polarizing plate according to an embodiment of the present invention; and FIG. 2 is a schematic cross-sectional view showing an image display device according to an embodiment of the present invention.

1‧‧‧Polarized elements

2, 3‧‧‧ transparent protective film

5‧‧‧Adhesive layer

10‧‧‧Adhesive polarizer

Claims (3)

An adhesive polarizing plate which is provided with a transparent protective film on at least a single-layer layer of a polarizing element, and an adhesive layer is laminated on a side of the transparent protective film which is not laminated with the polarizing element, and the adhesive layer is It is formed of an adhesive containing an acrylic polymer containing an alkyl (meth)acrylate and a (meth) acrylate having an aromatic ring structure as a monomer unit; when the photoelastic coefficient of the transparent protective film is set When the content of the (meth) acrylate monomer unit having an aromatic ring structure in X (m ² /N) or the above acrylic polymer is Y%, the absolute value of X is 14×10 ^-12 to 50. ×10 ^-12 , and X and Y satisfy -1 × 10 ¹¹ X + 3 ≦ Y ≦ - 1 × 10 ¹¹ X + 23. The adhesive polarizing plate of claim 1, wherein the transparent protective film comprises an acrylic resin, a cyclic olefin resin, a phenyl maleimide resin, a cellulose resin, and a modified polycarbonate. At least one resin selected from the group consisting of ester resins. An image display apparatus using the adhesive type polarizing plate of claim 1 or 2.