JP2012208248A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device that comprises polarizers attached to a glass cell for liquid crystal display through the intermediary of an adhesive layer and that achieves excellent display by fully preventing a white streak.SOLUTION: A liquid crystal display device according to the invention is formed by attaching polarizers on both surfaces of a glass cell for liquid crystal display through the intermediary of adhesive layers, in such a manner that absorption axes of the polarizers are mutually orthogonal. Each of the polarizers includes a polarizing film which is formed by applying adsorption orientation of dichroic dyes to a polyvinyl alcohol resin. At least one of the adhesive layers is formed with an adhesive composition that contains: (A) 100 pts.wt. of (meta) acrylic ester resin; (B) 0.2 to 5 pts.wt. of cross-linking agent; and (c) 0.03 to 1 pt.wt. of silane compound. With respect to the adhesive layers, a gel fraction is 70 to 99 wt.%, a storage elastic modulus is 0.8 to 10 MPa at a temperature of 23°C and a visual size is 350 mm×650 mm or more.

Description

  The present invention relates to a liquid crystal display device in which a polarizing plate is bonded to a glass cell for liquid crystal display via an adhesive layer.

  A polarizing plate is mounted on a liquid crystal display device and is widely used. A transparent protective film is laminated on both sides of a polarizing film, and an adhesive layer is formed on the surface of at least one protective film. It is distributed in the state where the release film is stuck to. Moreover, a retardation film may be laminated | stacked on the polarizing plate of the state by which the protective film was bonded on both surfaces of the polarizing film, and an adhesive layer / peeling film may be stuck on the retardation film side. Before bonding to the liquid crystal cell, the release film is peeled off from these polarizing plates, and the liquid crystal panel is bonded to the glass cell for liquid crystal display through the exposed pressure-sensitive adhesive layer. A display device is used. When the liquid crystal panel with the polarizing plate bonded to the liquid crystal display glass cell is exposed to high temperature, the distribution of residual stress acting on the polarizing plate becomes non-uniform, and stress concentration is concentrated on the outer periphery of the polarizing plate. As a result, a phenomenon called white spotting (also referred to as “light leakage”) in which the outer periphery becomes whitish during black display may occur, or color unevenness may occur. Therefore, suppression of such white spots and color unevenness is required.

  As one of countermeasures, Japanese Patent Application Laid-Open No. 2007-138056 (Patent Document 1) discloses a resin composition obtained by copolymerizing an aromatic ring-containing monomer with an alkyl acrylate as an adhesive composition for an optical film. A technique for suppressing light leakage by including an acrylic polymer having a molecular weight distribution represented by a ratio Mw / Mn of a weight average molecular weight Mw and a number average molecular weight Mn as wide as 10 to 50 is disclosed.

  Japanese Patent Application Laid-Open No. 2010-66756 (Patent Document 2) discloses (meth) acrylic acid in which (meth) acrylic acid alkyl ester having butyl acrylate as a representative example is represented by 2-methoxyethyl acrylate. An acrylic resin copolymerized with an alkoxyalkyl ester is combined with an ionic compound, particularly an ionic compound that is solid at room temperature, to form a pressure-sensitive adhesive layer. It has been disclosed to impart antistatic properties with excellent properties, particularly stability over time.

JP 2007-138056 A JP 2010-66756 A

  Even if the pressure-sensitive adhesive composition described in Patent Document 1 is used, the effect of reducing white spots may not be sufficient depending on, for example, the visual size of a liquid crystal display device, and foaming under high temperature conditions due to a wide molecular weight distribution. May occur.

  Furthermore, when the liquid crystal panel is placed under high temperature or high temperature and high humidity conditions, or when heating and cooling are repeated, foaming occurs in the pressure-sensitive adhesive layer along with changes in the size of the polarizing plate, or the polarizing plate and the pressure-sensitive adhesive. In some cases, floating or peeling may occur between the layers or between the pressure-sensitive adhesive layer and the liquid crystal cell. Therefore, it is also required that such a problem does not occur and the durability is excellent. In addition, if there is any problem when a polarizing plate with an adhesive is bonded to a glass cell for liquid crystal display to have a liquid crystal panel, the polarizing plate is removed and then a new film is pasted again. However, the pressure-sensitive adhesive layer is peeled off along with the polarizing plate at the time of peeling, so that the pressure-sensitive adhesive does not remain on the glass cell, and the so-called rework property is also excellent.

  The present invention provides a liquid crystal display device in which a polarizing plate is bonded to a glass cell for liquid crystal display via an adhesive layer, and white display is sufficiently suppressed and a liquid crystal display device capable of good display is provided. For the purpose.

  As a result of intensive studies to solve such problems, the present inventors have found that polarized light in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin on both surfaces of a glass cell for liquid crystal display via an adhesive layer. In the liquid crystal display device in which the polarizing plate having a film is bonded so that the absorption axes of the polarizing plates are orthogonal to each other, by adjusting the gel fraction and the storage elastic modulus of at least one of the pressure-sensitive adhesive layers to a specific range In a liquid crystal display device having a visual size of 350 mm × 650 mm or more, a white display can be effectively suppressed, and a liquid crystal display device having excellent durability can be obtained. Further, the pressure-sensitive adhesive layer is also excellent in reworkability of a polarizing plate. As a result, the present invention has been reached.

  That is, in the present invention, polarizing plates each having a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin are disposed on both surfaces of a liquid crystal display glass cell via an adhesive layer. At least one of the pressure-sensitive adhesive layers is (A) 100 parts of (meth) acrylate resin, (B) 0.2 to 5 parts by weight of a crosslinking agent, and (C). The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing 0.03 to 1 part by weight of a silane compound, and the pressure-sensitive adhesive layer has a gel fraction of 70 to 99% by weight and 0.8 to 10 MPa at 23 ° C. A liquid crystal display device having a storage elastic modulus and a visual size of 350 mm × 650 mm or more is provided.

  The (meth) acrylic ester resin (A) is preferably a polymer mainly composed of butyl acrylate. The (meth) acrylic ester resin (A) preferably has a polar functional group selected from the group consisting of a free carboxyl group, a hydroxyl group, an amino group, and an epoxy ring. The crosslinking agent (B) contains an isocyanate compound.

  In one embodiment, the pressure-sensitive adhesive composition further contains an active energy ray-curable compound (D), and the pressure-sensitive adhesive layer is formed by irradiating the pressure-sensitive adhesive composition with active energy rays.

  In one embodiment, the pressure-sensitive adhesive composition further contains 0.3 to 5 parts by weight of an antistatic agent (E).

  In one embodiment, the polarizing plate has a structure in which a transparent protective layer is laminated on both surfaces of a polarizing film via an adhesive.

  The transparent protective layer is preferably composed of a resin selected from a cellulose acetate resin and an olefin resin.

  In the present invention, polarizing plates each having a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin are orthogonal to each other on both surfaces of a glass cell for liquid crystal display via an adhesive layer. The pressure-sensitive adhesive layer contains a (meth) acrylic ester resin (A), a crosslinking agent (B), and a silane compound (C), and at least one gel component of the pressure-sensitive adhesive layer. By setting the rate to a specific range and the storage elastic modulus at 23 ° C. to a specific range, optical defects due to non-uniform stress distribution are prevented without impairing the durability of the pressure-sensitive adhesive layer, and white spots are suppressed. The Furthermore, this liquid crystal display device peels off the polarizing plate from the glass cell together with the pressure-sensitive adhesive layer when there is any defect after the polarizing plate is pasted on the glass cell for liquid crystal display via the pressure-sensitive adhesive layer. However, adhesive residue and cloudiness hardly occur on the surface of the glass cell after peeling, and the reworkability is excellent.

  This liquid crystal panel absorbs and relieves stress caused by dimensional changes of the polarizing plate and the glass cell under wet heat conditions, so that local stress concentration is reduced, and the pressure-sensitive adhesive layer from the glass cell is reduced. Floating and peeling are suppressed.

It is a disassembled perspective view which shows an example of the relationship between the layer structure of the liquid crystal display device which concerns on this invention, and an axial angle. It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate provided with the adhesive layer for sticking to the glass cell for liquid crystal displays. It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate provided with the adhesive layer for sticking to the glass cell for liquid crystal displays. It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate provided with the adhesive layer for sticking to the glass cell for liquid crystal displays. It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate provided with the adhesive layer for sticking to the glass cell for liquid crystal displays.

  Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. An example of the relationship between the layer configuration and the axial angle of the liquid crystal panel according to the present invention is shown in an exploded perspective view in FIG. Referring to FIG. 1, a liquid crystal display device to which the present invention is applied is a liquid crystal display glass cell 10 having a rectangular display surface (hereinafter simply referred to as “liquid crystal cell” or “glass cell”). The first polarizing plate 21 is attached to one side of the liquid crystal cell 10 via the first pressure-sensitive adhesive layer 31, and the second side of the liquid crystal cell 10 via the second pressure-sensitive adhesive layer 32. A polarizing plate 22 is attached. The pair of polarizing plates 21 and 22 are arranged so as to be crossed Nicols, that is, both absorption axes 21A and 22A are orthogonal to each other.

  Of the first adhesive layer 31 for adhering the first polarizing plate 21 to the liquid crystal cell 10 and the second adhesive layer 32 for adhering the second polarizing plate 22 to the liquid crystal cell 10, At least one of (A) (B) crosslinking agent 0.01 to 0.5 parts by weight and (C) silane compound 0.03 to 1 parts by weight with respect to 100 parts of (A) (meth) acrylic acid ester resin. The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition, and has a gel fraction of 70 to 99% by weight and a storage elastic modulus of 0.8 to 10 MPa at 23 ° C.

  The first polarizing plate 21 and the second polarizing plate 22 have a pressure-sensitive adhesive composition defined in the present invention for a liquid crystal display device in which the absorption axes 21A and 22A are arranged so as to be orthogonal to each other. It has been found that applying a pressure-sensitive adhesive layer formed from the product is particularly effective. At least one of the pressure-sensitive adhesive layers 31 and 32 disposed on both surfaces of the liquid crystal cell 10 is formed from the specific pressure-sensitive adhesive composition described above, the gel fraction is in a specific range, and the visual size is in a specific range. By doing so, the desired effect is exhibited, but as described above, both of the adhesive layers 31 and 32 arranged on both surfaces of the liquid crystal cell 10 are constituted by such a thing. However, it is preferable from the viewpoint of suppressing white spots.

Hereinafter, each member constituting the liquid crystal display device of the present invention will be described in order from the liquid crystal display glass cell 10.
[Glass cell for liquid crystal display]
The glass cell 10 for liquid crystal display is composed of two transparent glass substrates 11 and 12, and a liquid crystal (not shown) is sandwiched between them. The liquid crystal sealed between the two glass substrates 11 and 12 is twisted nematic (TN), vertical alignment (VA), and lateral electric field (In-Plane Switching: IPS) depending on the alignment method. There are various types of systems. The present invention can be applied to any type of liquid crystal cell as long as the pair of polarizing plates are arranged in crossed Nicols above and below the liquid crystal cell. Although illustration is omitted, on the liquid crystal layer side of the transparent glass substrates 11 and 12, an alignment film for aligning the liquid crystal, a transparent electrode for turning on and off the voltage to control the alignment, and a color display may be used. For example, a color filter is also arranged.

As the glass substrates 11 and 12 constituting the liquid crystal cell 10, soda lime glass, low alkali glass, non-alkali glass, and the like can be applied. Particularly, non-alkali glass or low alkali glass is preferably used.
[Adhesive layer (adhesive composition)]
Next, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layers 31 and 32 will be described. This pressure-sensitive adhesive composition basically comprises an acrylic resin and a crosslinking agent. In the present invention, the first pressure-sensitive adhesive layer 31 for adhering the first polarizing plate to both surfaces of the liquid crystal cell 10 and the second pressure-sensitive adhesive layer 32 for adhering the second polarizing plate, respectively. At least one of these is the specific copolymer described above, and (A) (meth) acrylic ester resin 100 parts of (B) a crosslinking agent and (C) a silane compound are mixed in a predetermined amount It is formed from the agent composition, has a gel fraction of 70 to 99% by weight, and has a storage elastic modulus of 0.8 to 10 MPa at 23 ° C. Each component which comprises this adhesive composition is demonstrated.

<(Meth) acrylic ester resin (A)>
In the liquid crystal panel of the present invention, the (meth) acrylic ester resin (A) used in the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layers 31 and 32 is represented by the following formula (I):

(Wherein, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 1 to 14 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms)
The main component is a structural unit derived from the (meth) acrylic acid alkyl ester (A-1) represented by the formula (1), in addition to the structural unit derived from the (meth) acrylic acid alkyl ester (A-1). The structural unit derived from the aromatic ring-containing monomer (A-2) and the structural unit derived from the polar functional group-containing monomer (A-3) may be included. Here, (meth) acrylic acid means that either acrylic acid or methacrylic acid may be used, and “(meth)” when referred to as (meth) acrylate, (meth) acryloyl, etc. has the same meaning. is there.

In the above formula (I), which is the main structural unit of the (meth) acrylic ester resin (A), R ₁ is a hydrogen atom or a methyl group, and R ₂ is an alkyl group having 1 to 14 carbon atoms. In the alkyl group represented by R ₂ , a hydrogen atom in each group may be substituted with an alkoxy group having 1 to 10 carbon atoms.

Of the (meth) acrylic acid ester (A) represented by the formula (I), R ₂ is an unsubstituted alkyl group, specifically, methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid Linear alkyl acrylate esters such as n-butyl, n-octyl acrylate, and lauryl acrylate; branched alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate Esters; linear alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and lauryl methacrylate; isobutyl methacrylate, 2-methacrylic acid 2- Ethylhexyl and isooctyl methacrylate Examples thereof include branched alkyl methacrylates and the like.

  Among these, n-butyl acrylate is preferable. Specifically, among all monomers constituting the (meth) acrylic ester resin, n-butyl acrylate is 50% by weight or more, and It is preferable to satisfy the above-mentioned regulations regarding the (meth) acrylic ester resin (A).

As the (meth) acrylic acid ester represented by the formula (I) when R ₂ is an alkyl group substituted with an alkoxy group, that is, an alkoxyalkyl group, specifically, 2-methoxyethyl acrylate, acrylic Examples thereof include ethoxymethyl acid, 2-methoxyethyl methacrylate, ethoxymethyl methacrylate and the like.

  These (meth) acrylic acid esters can be used alone or in combination with a plurality of different ones.

  An unsaturated monomer having an olefinic double bond and at least one aromatic ring in the molecule (aromatic ring-containing monomer) having a structural unit derived from the aromatic ring-containing monomer (A-2) Are preferably those having a (meth) acryloyl group as a group containing an olefinic double bond. Examples thereof include benzyl (meth) acrylate, neopentyl glycol benzoate (meth) acrylate, and the like. Preferred examples include the following formula (II):

(In the formula, R ₃ represents a hydrogen atom or a methyl group, n is an integer of 1 to 8, and R ₄ represents a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group.)
It is an aromatic ring containing (meth) acryl compound shown by these.

  In the above formula (II) representing an aromatic ring-containing (meth) acrylic compound, when R4 is an alkyl group, its carbon number can be about 1 to 9, and when it is an aralkyl group, its carbon number is In the case of an aryl group of about 7 to 11, the carbon number can be about 6 to 10. As an alkyl group having 1 to 9 carbon atoms, methyl, butyl, nonyl, etc., as an aralkyl group having 7 to 11 carbon atoms, benzyl, phenethyl, naphthylmethyl and the like, and as an aryl group having 6 to 10 carbon atoms, phenyl, Examples include tolyl and naphthyl.

Specific examples of the aromatic ring-containing (meth) acrylic compound of the formula (II) include (meth) acrylic acid 2-phenoxyethyl, (meth) acrylic acid 2- (2-phenoxyethoxy) ethyl, ethylene oxide-modified nonylphenol ( And (meth) acrylic acid ester, (meth) acrylic acid 2- (o-phenylphenoxy) ethyl, and the like. These aromatic ring-containing monomers may be used alone or in combination of a plurality of different ones. Among these, 2-phenoxyethyl (meth) acrylate [compound of R ₄ = H and n = 1 in the above formula (II)], 2- (o-phenylphenoxy) ethyl (meth) acrylate [the above formula In (II), R ₄ = o-phenyl, compound of n = 1], 2- (2-phenoxyethoxy) ethyl (meth) acrylate [in the above formula (II), R ₄ = H, n = 2 Compound] is preferably used as one of the aromatic ring-containing monomers constituting the acrylic resin (A).

  In the structural unit derived from the polar functional group-containing monomer (A-3), the polar functional group can be a free carboxyl group, a hydroxyl group, an amino group, a heterocyclic group including an epoxy ring, and the like. The polar functional group-containing monomer is preferably a (meth) acrylic acid compound having a polar functional group. Examples include unsaturated monomers having free carboxyl groups such as acrylic acid, methacrylic acid, and β-carboxyethyl acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, Unsaturated monomers having a hydroxyl group, such as 2- or 3-chloro-2-hydroxypropyl (meth) acrylate and diethylene glycol mono (meth) acrylate; acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, Non-cyclic heterocyclic groups such as tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, and 2,5-dihydrofuran. Sum monomer; N, such as N- dimethylaminoethyl (meth) acrylate, and the like unsaturated monomer having a different amino group and heterocyclic. The polar functional group is preferably a free carboxyl group, a hydroxyl group, an amino group, or an epoxy ring. These polar functional group-containing monomers may be used alone or in a plurality of different types.

  Among these, it is preferable to use the unsaturated monomer which has a hydroxyl group as one of the structural units derived from the polar functional group containing monomer which comprises (meth) acrylic ester resin (A). In addition to the unsaturated monomer having a hydroxyl group, it is also effective to use an unsaturated monomer having another polar functional group, for example, an unsaturated monomer having a free carboxyl group.

  In the (meth) acrylic acid ester resin (A), the content of the (meth) acrylic acid alkyl ester represented by the above formula (I) is 80 to 96% by weight, preferably 85% by weight or more. Further, it is preferably 95% by weight or less. The content of the structural unit (A-2) derived from the aromatic ring-containing monomer is 3 to 15% by weight, preferably 5% by weight or more, and preferably 13% by weight or less. The content of the structural unit (A-3) derived from the polar functional group-containing monomer is 0.1 to 5% by weight, preferably 0.5% by weight or more, and preferably 3% by weight. It is as follows.

  The (meth) acrylic acid ester resin (A) used in the present invention is a (meth) acrylic acid alkyl ester represented by the formula (I) described above, an aromatic ring-containing monomer and a polar functional group-containing monomer. A structural unit derived from a monomer different from the monomer may be included. Examples of these include structural units derived from (meth) acrylic acid esters having an alicyclic structure in the molecule, structural units derived from styrene monomers, structural units derived from vinyl monomers, molecules Examples thereof include a structural unit derived from a monomer having a plurality of (meth) acryloyl groups.

  The alicyclic structure is a cycloparaffin structure having usually 5 or more carbon atoms, preferably about 5 to 7 carbon atoms. Specific examples of the acrylate ester having an alicyclic structure include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, cyclododecyl acrylate, methyl cyclohexyl acrylate, trimethyl cyclohexyl acrylate, and tert-butyl acrylate. Specific examples of methacrylic acid esters having an alicyclic structure include cyclohexyl, α-ethoxyacrylic acid cyclohexyl, cyclohexyl phenyl acrylate, etc. Specific examples of methacrylic acid ester having an alicyclic structure include isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, methacrylic acid. Cyclododecyl, methyl cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, tert-butyl cyclohexyl methacrylate, cyclohexyl methacrylate Phenyl and the like.

  Specific examples of the styrenic monomer include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, and octyl styrene. Alkyl styrene; halogenated styrene such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; and nitrostyrene, acetylstyrene, methoxystyrene, divinylbenzene, and the like.

  Specific examples of the vinyl monomer include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl fatty acid esters such as vinyl laurate; vinyl halides such as vinyl chloride and vinyl bromide; Vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyls such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; conjugated diene monomers such as butadiene, isoprene, and chloroprene; and acrylonitrile, methacrylonitrile, etc. be able to.

  Specific examples of the monomer having a plurality of (meth) acryloyl groups in the molecule include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonane. Two diols in the molecule, such as diol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and tripropylene glycol di (meth) acrylate A monomer having a (meth) acryloyl group; a monomer having three (meth) acryloyl groups in the molecule, such as trimethylolpropane tri (meth) acrylate;

  The monomers different from the (meth) acrylic acid alkyl ester represented by the formula (I), the aromatic ring-containing monomer, and the polar functional group-containing monomer as described above may be used alone or in combination of two or more. Can be used in combination. In the (meth) acrylic acid ester resin (A) used for the pressure-sensitive adhesive, it is derived from a monomer different from the (meth) acrylic acid alkyl ester, the aromatic ring-containing monomer and the polar functional group-containing monomer. The structural unit is usually contained in an amount of 0 to 20 parts by weight, preferably 0 to 10 parts by weight, with respect to 100 parts by weight of the nonvolatile content of the resin.

  The resin component which comprises an adhesive composition is the above (meth) acrylic-acid alkylester (A-1) shown by Formula (I), an aromatic ring containing monomer (A-2), and polarity. Two or more kinds of acrylic resins containing a structural unit derived from the functional group-containing monomer (A-3) may be included. In addition, the (meth) acrylic acid ester resin (A) defined in the present invention has a structural unit derived from an acrylic resin different from that, for example, a (meth) acrylic acid alkyl ester of the formula (I), and polar You may mix and use the acrylic resin etc. which do not contain a functional group. Structural unit derived from (meth) acrylic acid alkyl ester (A-1) represented by formula (I), aromatic ring-containing monomer (A-2), and polar functional group-containing monomer (A-3) The (meth) acrylic acid ester resin (A) containing is preferably 80% by weight or more, more preferably 90% by weight or more, based on the whole (meth) acrylic acid ester resin.

  (Meth) acrylic acid ester-based resin which is a copolymer of a monomer mixture containing a (meth) acrylic acid alkyl ester represented by formula (I), an aromatic ring-containing monomer and a polar functional group-containing monomer ( A) employs those having a standard polystyrene equivalent weight average molecular weight Mw in the range of 1,000,000 to 2,000,000 by gel permeation chromatography (GPC). When the weight average molecular weight in terms of standard polystyrene is 1 million or more, the adhesiveness under high temperature and high humidity is improved, and the possibility of occurrence of floating or peeling between the liquid crystal cell and the pressure-sensitive adhesive layer tends to be low. And reworkability tends to be improved. Further, when the weight average molecular weight is 2 million or less, even if the size of the polarizing plate attached to the pressure-sensitive adhesive layer changes, the pressure-sensitive adhesive layer fluctuates following the dimensional change. This is preferable because there is no difference between the brightness of the peripheral portion and the brightness of the central portion, and white spots and color unevenness tend to be suppressed.

  Moreover, it is preferable that the said (meth) acrylic acid ester-type resin (A) has the glass transition temperature in the range of -10-60 degreeC for adhesive expression. The glass transition temperature of the resin can generally be measured with a differential scanning calorimeter.

  The (meth) acrylic ester resin (A) constituting the pressure-sensitive adhesive composition can be produced by various known methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. . In the production of this acrylic resin, a polymerization initiator is usually used. The polymerization initiator is used in an amount of about 0.001 to 5 parts by weight with respect to a total of 100 parts by weight of all monomers used in the production of the acrylic resin.

  As the polymerization initiator, a thermal polymerization initiator, a photopolymerization initiator, or the like is used. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone. Examples of the thermal polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl-2,2'-azobis (2-methylpropio) And azo compounds such as 2,2'-azobis (2-hydroxymethylpropionitrile); lauryl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroper Oxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, te Organic peroxides such as t-butyl peroxyneodecanoate, tert-butyl peroxypivalate, and (3,5,5-trimethylhexanoyl) peroxide; potassium persulfate, ammonium persulfate, and hydrogen peroxide Inorganic peroxides such as A redox initiator using a peroxide and a reducing agent in combination can also be used as the polymerization initiator.

  As a method for producing the (meth) acrylic acid ester resin, the solution polymerization method is preferable among the methods shown above. A specific example of the solution polymerization method will be described. A desired monomer and an organic solvent are mixed, and a thermal polymerization initiator is added under a nitrogen atmosphere, and is about 40 to 90 ° C, preferably about 60 to 80 ° C. And a method of stirring for about 3 to 10 hours. Moreover, in order to control reaction, you may add a monomer and a thermal-polymerization initiator continuously or intermittently during superposition | polymerization, or may be added in the state melt | dissolved in the organic solvent. Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as propyl alcohol and isopropyl alcohol; acetone, methyl ethyl ketone, and methyl isobutyl. Ketones such as ketones can be used.

<Crosslinking agent (B)>
The crosslinking agent (B) is a compound that reacts with a structural unit derived from the polar functional group-containing monomer (A-3) in the (meth) acrylic ester resin (A) to crosslink the acrylic resin. . Specific examples include isocyanate compounds, aziridine compounds, metal chelate compounds, and the like. Among these, the isocyanate compound and the aziridine compound have at least two functional groups capable of reacting with the polar functional group in the (meth) acrylic ester resin (A) in the molecule.

  Isocyanate compounds are compounds having at least two isocyanato groups (-NCO) in the molecule, such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, Examples thereof include hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. In addition, adducts obtained by reacting these isocyanate compounds with polyols such as glycerol and trimethylolpropane, and those obtained by converting isocyanate compounds into dimers, trimers, and the like can also be used as crosslinking agents for pressure-sensitive adhesives. Two or more isocyanate compounds can be mixed and used.

  An aziridine-based compound is a compound having at least two skeletons of a three-membered ring composed of one nitrogen atom and two carbon atoms, also called ethyleneimine, for example, diphenylmethane-4,4′-bis ( 1-aziridinecarboxamide), toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1- (2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene -1,6-bis (1-aziridinecarboxamide), trimethylolpropane tris-β-aziridinylpropionate, tetramethylolmethane tris-β-aziridinylpropionate, and the like.

  Examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetoacetate is coordinated to a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Is mentioned.

  Among these crosslinking agents, isocyanate compounds, especially xylylene diisocyanate, tolylene diisocyanate or hexamethylene diisocyanate, or adducts obtained by reacting these isocyanate compounds with polyols such as glycerol and trimethylolpropane, and these A dimer, a trimer, or the like of an isocyanate compound or a mixture of these isocyanate compounds is preferably used. In particular, when the polar functional group-containing monomer (A-3) has a polar functional group selected from a free carboxyl group, a hydroxyl group, an amino group and an epoxy ring, at least one of the crosslinking agents (B) is an isocyanate group. It is preferable to use a compound. Among the above-mentioned preferred isocyanate compounds, tolylene diisocyanate, an adduct obtained by reacting tolylene diisocyanate with a polyol, a dimer of tolylene diisocyanate, and a trimer of tolylene diisocyanate, hexamethylene diisocyanate, hexa Examples thereof include adducts obtained by reacting methylene diisocyanate with polyol, dimers of hexamethylene diisocyanate, and trimers of hexamethylene diisocyanate.

  A crosslinking agent (B) is mix | blended in the ratio of 0.2-5 weight part with respect to 100 weight part of (meth) acrylic acid ester-type resin (A). The amount of the crosslinking agent (B) relative to 100 parts by weight of the (meth) acrylic ester resin (A) is preferably 0.2 parts by weight or more because the durability of the pressure-sensitive adhesive layer tends to be improved, The amount of 5 parts by weight or less is preferable because white spots on the liquid crystal panel are not noticeable.

<Silane compound (C)>
A crosslinking agent (B) and a silane compound (C) are blended with the (meth) acrylic ester resin (A) as described above to obtain a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer in the present invention preferably contains a silane compound (C) in order to improve the adhesion between the pressure-sensitive adhesive layer and the glass cell. It is preferable to contain the silane compound (C) in the acrylic resin before blending the agent.

  Examples of the silane compound (C) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- ( 2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxy (Cyclohexyl) ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimeth Shishiran, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl dimethoxymethyl silane, such as 3-glycidoxypropyl ethoxy dimethyl silane. Two or more silane compounds (C) may be used.

  The silane compound (C) may be of a silicone oligomer type. When the silicone oligomer is shown in the form of (monomer)-(monomer) copolymer, for example, the following can be mentioned.

  3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane copolymer, and 3-mercaptopropyltriethoxysilane-tetraethoxy A copolymer containing a mercaptopropyl group, such as a silane copolymer;

  Mercaptomethyl groups such as mercaptomethyltrimethoxysilane-tetramethoxysilane copolymer, mercaptomethyltrimethoxysilane-tetraethoxysilane copolymer, mercaptomethyltriethoxysilane-tetramethoxysilane copolymer, and mercaptomethyltriethoxysilane-tetraethoxysilane copolymer. Containing copolymers;

  3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane -Tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-Methacryloyloxypropylmethyldiethoxysilane-tetra Toki bell Ranco polymers such as, methacryloyloxypropyl group containing copolymers;

  3-acryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane -Tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane Rimmer such as, acryloyloxypropyl group-containing copolymer;

  Vinyltrimethoxysilane-tetramethoxysilane copolymer, vinyltrimethoxysilane-tetraethoxysilane copolymer, vinyltriethoxysilane-tetramethoxysilane copolymer, vinyltriethoxysilane-tetraethoxysilane copolymer, vinylmethyldimethoxysilane-tetramethoxysilane copolymer, Vinyl group-containing copolymers such as vinylmethyldimethoxysilane-tetraethoxysilane copolymer, vinylmethyldiethoxysilane-tetramethoxysilane copolymer, and vinylmethyldiethoxysilane-tetraethoxysilane copolymer;

  3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetraethoxysilane Copolymer, 3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-aminopropylmethyldiethoxy Amino group-containing copolymers such as silane-tetraethoxysilane copolymers.

  These silane compounds (C) are often liquids. The compounding amount of the silane compound (C) in the pressure-sensitive adhesive composition is 0.1% with respect to 100 parts by weight of the nonvolatile content of the (meth) acrylic acid ester resin (A) (when two or more types are used, the total amount). It is about 03 to 1 part by weight. It is preferable that the amount of the silane compound with respect to 100 parts by weight of the nonvolatile content of the acrylic resin (A) is 0.03 parts by weight or more because adhesion between the pressure-sensitive adhesive layer and the glass cell is improved. Moreover, it is preferable for the amount to be 1 part by weight or less because bleeding out of the silane compound tends to be suppressed from the pressure-sensitive adhesive layer.

<Active energy curable compound (D)>
In the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer in the present invention, the active energy ray-curable compound (D) can be contained and irradiated with active energy rays. Examples of the active energy ray-curable compound (D) include epoxy compounds and acrylic compounds.

  The epoxy compound is a compound having at least two epoxy groups in the molecule, for example, bisphenol A type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether. 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N, N-diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis ( N, N'-diglycidylaminomethyl) cyclohexane and the like. Two or more types of epoxy compounds can be mixed and used.

  The acrylic compound is a compound having at least two acrylic unsaturated double bonds in the molecule, and is composed of 2-hydroxy-3-acryloyloxypropyl methacrylate, ethoxylated bisphenol A diacrylate, tricyclodecane dimethanol dimer. Examples include acrylate, dipropylene glycol diacrylate, and a diacrylate of an acetal compound of hydroxypivalaldehyde and trimethylpropane. Two or more kinds of acrylic compounds can be mixed and used.

  Examples of the active energy rays include ultraviolet rays and electron beams. The ultraviolet rays are obtained with a high-pressure mercury lamp, an electrodeless lamp, a xenon lamp or the like, while the electron beam is obtained with an electron beam accelerator or the like. Among these active energy rays, ultraviolet rays are particularly preferable.

<Antistatic agent (E)>
The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer in the present invention may contain an ionic compound as the antistatic agent (E). In particular, the aromatic ring-containing monomer (A-2) constituting the (meth) acrylic ester resin (A) is an aromatic ring-containing (meth) acrylic compound represented by the above formula (II), When n in 2) is 2 or more, it is more effective in suppressing white spots, and an ionic compound is added to the pressure-sensitive adhesive composition containing an acrylic resin copolymerized with this monomer. Thus, good antistatic properties can be imparted while maintaining a high white spot suppression effect. The ionic compound here is a compound that exists in a combination of a cation and an anion, and each cation and anion may be inorganic or organic, but a (meth) acrylic ester. From the viewpoint of compatibility with the resin (A), at least one of the cation and the anion is preferably an ionic compound containing an organic group.

  Examples of the cation constituting the ionic compound include a lithium cation, a pyridinium cation represented by the following formula (III), and a quaternary ammonium cation represented by the following formula (IV).

In formula (III), R _{5 to} R ₉ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ₁₀ represents an alkyl group having 1 to 16 carbon atoms;
In formula (IV), R ₁₁ represents an alkyl group having 1 to 12 carbon atoms, and R ₁₂ , R ₁₃ and R ₁₄ each independently represents an alkyl group having 6 to 12 carbon atoms.

The pyridinium cation represented by the above formula (III) has a total carbon number of 6 or more. Among them, the total carbon number is 8 or more, particularly 10 or more, from the viewpoint of compatibility with the acrylic resin (A). To preferred. The total number of carbon atoms is preferably 36 or less, more preferably 30 or less. Among the pyridinium-based cations represented by the formula (III), R ₇ bonded to the 4-position carbon atom of the pyridine ring is an alkyl group, and R ₅ , R ₆ , R bonded to other carbon atoms of the pyridine ring. _{One in which 8} and R ₉ are each a hydrogen atom is one of the preferred cations. Specific examples of the pyridinium cation represented by the formula (III) include the following.

N-methyl-4-hexylpyridinium cation,
N-butyl-4-methylpyridinium cation,
N-butyl-2,4-diethylpyridinium cation,
N-butyl-2-hexylpyridinium cation,
N-hexyl-2-butylpyridinium cation,
N-hexyl-4-methylpyridinium cation,
N-hexyl-4-ethylpyridinium cation,
N-hexyl-4-butylpyridinium cation,
N-octyl-4-methylpyridinium cation,
N-octyl-4-ethylpyridinium cation,
N-octylpyridinium cation and the like.

  The ammonium cation represented by the above formula (IV) is a tetraalkylammonium cation, and this tetraalkylammonium cation has a total carbon number of 20 or more, more preferably 22 or more, in phase with the acrylic resin (A). It is preferable from the viewpoint of solubility. The total number of carbon atoms is preferably 36 or less, more preferably 30 or less. Specific examples of the tetraalkylammonium cation represented by the formula (IV) include the following.

Tetrahexyl ammonium cation,
Tetraoctyl ammonium cation,
Tributylmethylammonium cation,
Trihexylmethylammonium cation,
Trioctylmethylammonium cation,
Tridecylmethylammonium cation,
Trihexylethylammonium cation,
Trioctylethylammonium cation, etc.

On the other hand, examples of anions constituting an ionic compound include the following.
Chloride anion [Cl ⁻ ],
Bromide anion [Br ⁻ ],
Iodide anion [I ⁻ ],
Tetrachloroaluminate anion [AlCl ₄ ⁻ ],
Heptachlorodialuminate anion [Al ₂ Cl ₇ ⁻ ],
Tetrafluoroborate anion [BF ₄ ⁻ ],
Hexafluorophosphate anion [PF ₆ ⁻ ],
Perchlorate anion [ClO ₄ ⁻ ],
Nitrate anion [NO ₃ ⁻ ],
Acetate anion [CH ₃ COO ⁻ ],
Trifluoroacetate anion [CF ₃ COO ⁻ ],
Methanesulfonate anion [CH ₃ SO ₃ ⁻ ],
Trifluoromethanesulfonate anion [CF ₃ SO ₃ ⁻ ],
Bis (fluorosulfonyl) imide anion [(FSO ₂ ) ₂ N ⁻ ],
Bis (trifluoromethanesulfonyl) imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ],
Tris (trifluoromethanesulfonyl) methanide anion [(CF ₃ SO ₂ ) ₃ C ⁻ ],
Hexafluoroarsenate anion [AsF ₆ ⁻ ],
Hexafluoroantimonate anion [SbF ₆ ⁻ ],
Hexafluoroniobate anion [NbF ₆ ⁻ ],
Hexafluorotantalate anion [TaF ₆ ⁻ ],
(Poly) hydrofluorofluoride anion [F (HF) _n ⁻ ] (n is about 1 to 3),
Thiocyanate anion [SCN ^-]
Dicyanamide anion [(CN) ₂ N ⁻ ],
Perfluorobutanesulfonate anion [C ₄ F ₉ SO ₃ ⁻ ],
Bis (pentafluoroethanesulfonyl) imide anion [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ],
Perfluorobutanoate anion [C ₃ F ₇ COO ⁻ ],
(Trifluoromethanesulfonyl) (trifluoromethanecarbonyl) imide anion [(CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ ] and the like.

  Specific examples of the ionic compound can be appropriately selected from the combination of the above cation and anion. Specific examples of the ionic compound that is a combination of a cation and an anion include the following.

Lithium bis (fluorosulfonyl) imide,
Lithium bis (trifluoromethanesulfonyl) imide,
Lithium hexafluorophosphate,
Lithium iodide (lithium iodide),
N-methyl-4-hexylpyridinium bis (fluorosulfonyl) imide,
N-butyl-2-methylpyridinium bis (fluorosulfonyl) imide,
N-hexyl-4-methylpyridinium bis (fluorosulfonyl) imide,
N-octyl-4-methylpyridinium bis (fluorosulfonyl) imide,
N-methyl-4-hexylpyridinium bis (trifluoromethanesulfonyl) imide,
N-butyl-2-methylpyridinium bis (trifluoromethanesulfonyl) imide,
N-hexyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide,
N-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide,
N-methyl-4-hexylpyridinium hexafluorophosphate,
N-butyl-2-methylpyridinium hexafluorophosphate,
N-hexyl-4-methylpyridinium hexafluorophosphate,
N-octyl-4-methylpyridinium hexafluorophosphate,
N-methyl-4-hexylpyridinium perchlorate,
N-butyl-2-methylpyridinium perchlorate,
N-hexyl-4-methylpyridinium perchlorate,
N-octyl-4-methylpyridinium perchlorate,
Tetrahexylammonium bis (fluorosulfonyl) imide,
Tributylmethylammonium bis (fluorosulfonyl) imide,
Trihexylmethylammonium bis (fluorosulfonyl) imide,
Trioctylmethylammonium bis (fluorosulfonyl) imide,
Tetrahexylammonium bis (trifluoromethanesulfonyl) imide,
Tributylmethylammonium bis (trifluoromethanesulfonyl) imide,
Trihexylmethylammonium bis (trifluoromethanesulfonyl) imide,
Trioctylmethylammonium bis (trifluoromethanesulfonyl) imide,
Tetrahexylammonium hexafluorophosphate,
Tributylmethylammonium hexafluorophosphate,
Trihexylmethylammonium hexafluorophosphate,
Trioctylmethylammonium hexafluorophosphate,
Tetrahexylammonium perchlorate,
Tributylmethylammonium perchlorate,
Trihexylmethylammonium perchlorate,
Trioctylmethylammonium perchlorate.

  These ionic compounds can be used alone or in combination of two or more. When mix | blending an ionic compound as an antistatic agent (E), the quantity becomes like this. Preferably it is 0.3-5 weight part with respect to 100 weight part of (meth) acrylic acid ester-type resin (A).

  The pressure-sensitive adhesive composition described above may further contain a crosslinking catalyst, weathering stabilizer, tackifier, plasticizer, softener, dye, pigment, inorganic filler, resin other than acrylic resin, and the like. It is also useful to form a harder pressure-sensitive adhesive layer by blending the pressure-sensitive adhesive with an ultraviolet curable compound and forming the pressure-sensitive adhesive layer by irradiating it with ultraviolet rays and curing it. In addition, if a crosslinking catalyst is blended with the crosslinking agent in the pressure-sensitive adhesive, the pressure-sensitive adhesive layer can be prepared by aging in a short time, and the resulting pressure-sensitive adhesive polarizing plate floats between the polarizing plate and the pressure-sensitive adhesive layer. Occurrence of peeling or peeling or foaming in the pressure-sensitive adhesive layer can be suppressed, and reworkability can be further improved. Examples of the crosslinking catalyst include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resin, and melamine resin. . When an amine compound is added to the adhesive as a crosslinking catalyst, an isocyanate compound is suitable as the crosslinking agent.

  These components constituting the pressure-sensitive adhesive are essential components (meth) acrylic ester resin (A), crosslinking agent (B) and silane compound (C) in a state dissolved in a solvent as necessary. And can be mixed with a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition can be applied on a suitable substrate and dried to form a pressure-sensitive adhesive layer.

<Gel fraction of adhesive layer>
In the present invention, as described above, the pressure-sensitive adhesive layer has a gel fraction of 70 to 99% by weight. When the gel fraction of the pressure-sensitive adhesive layer is 70% by weight or more, the durability of the pressure-sensitive adhesive layer is preferably improved, and when the gel fraction is 99% by weight or less, it is preferable because the production is easy. Here, the gel fraction is a value measured according to the following (1) to (4).

  (1) An adhesive layer having an area of about 8 cm × about 8 cm and a metal mesh made of SUS304 (its weight is Wm) of about 10 cm × about 10 cm are bonded together.

  (2) Weigh the pasted material obtained in (1) above, set the weight to Ws, then fold it 4 times so as to wrap the adhesive layer and weigh it with a stapler (stapler). The weight is Wb.

  (3) The mesh stapled in (2) above is placed in a glass container, and 60 mL of ethyl acetate is added and immersed, and then the glass container is stored at room temperature for 3 days.

(4) The mesh is taken out from the glass container, dried at 120 ° C. for 24 hours, weighed, and its weight is defined as Wa.
Gel fraction (% by weight) = [{Wa− (Wb−Ws) −Wm} / (Ws−Wm)] × 100
Calculate the gel fraction based on

  The gel fraction of the pressure-sensitive adhesive layer can be adjusted by, for example, the type of (meth) acrylic acid ester resin (A) that is an active ingredient of the pressure-sensitive adhesive composition and the amount of the crosslinking agent (B). Specifically, the amount of the polar functional group-containing monomer (A-3) in the (meth) acrylic ester resin (A) is increased, or the amount of the crosslinking agent (B) in the pressure-sensitive adhesive composition is increased. If the amount is increased, the gel fraction becomes high, and the gel fraction may be adjusted by the amount of the polar functional group-containing monomer and / or the crosslinking agent. For the polar functional group-containing monomer (A-3), the amount of the structural unit derived from the polar functional group-containing monomer (A-3) in the (meth) acrylic ester resin (A), From the range of 0.1 to 5% by weight, in combination with other components constituting the (meth) acrylic ester resin (A), and further in combination with the type and amount of the crosslinking agent, the gel fraction is the above Select and adjust the range. On the other hand, about the quantity of a crosslinking agent (C), the compounding quantity of the crosslinking agent with respect to 100 weight part (the total amount when using 2 or more types) of the non volatile matter of the acrylic resin which comprises an adhesive layer is 0.2-5. It is preferable to select according to the kind of acrylic resin from the range of about parts by weight.

<Storage modulus of adhesive layer>
In the present invention, as described above, the pressure-sensitive adhesive layer has a storage elastic modulus of 0.8 to 10 MPa at 23 ° C. When the storage elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer is 0.8 MPa or more, due to contraction of the polarizing plate when the liquid crystal panel in a state where the polarizing plate is bonded to the glass cell for liquid crystal display is exposed to high temperature or the like. It is preferable because white spots can be suppressed, and is preferably 10 MPa or less because durability is not easily lowered due to a decrease in adhesive force.

The storage elastic modulus is obtained by laminating an adhesive having a thickness of 30 μm to produce a cylindrical test piece having a thickness of 8 mmφ × 3 mm, and measuring it by the torsional shear method under the following conditions.

Measuring device: rheometric dynamic viscoelasticity measuring device “DYNAMIC ANALYZER RDAII”
Frequency: 1Hz
Temperature: 23 ° C
The pressure-sensitive adhesive layers 31 and 32 on the polarizing plates 21 and 22 are formed by, for example, applying the above-mentioned pressure-sensitive adhesive composition on a release film to form a pressure-sensitive adhesive layer. , 22 and a method of applying the pressure-sensitive adhesive composition on the polarizing plates 21 and 22 to form a pressure-sensitive adhesive layer and attaching a release film to the surface of the pressure-sensitive adhesive to protect it. be able to. The release film used here is made of, for example, a film made of various transparent resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, and the like on the bonding surface with the adhesive layer of the substrate, such as silicone treatment. It can be constituted by a mold release treatment.

  Although the thickness of the adhesive layers 31 and 32 is not particularly limited, it is usually preferably 30 μm or less, more preferably 10 μm or more, and further preferably 15 to 25 μm. When the thickness of the pressure-sensitive adhesive layer is 30 μm or less, the adhesiveness under high temperature and high humidity is improved, and the possibility of occurrence of floating or peeling between the glass cell and the pressure-sensitive adhesive layer tends to be reduced. Moreover, it is preferable because reworkability tends to be improved, and if the thickness is 10 μm or more, the adhesive layer follows the change in dimensions even if the size of the polarizing plate bonded thereto changes. Therefore, it is preferable that there is no difference between the brightness of the peripheral edge of the liquid crystal cell and the brightness of the central portion, and white spots and color unevenness tend to be suppressed. Conventionally, in general, the thickness of the pressure-sensitive adhesive layer adhered to the glass cell for liquid crystal display has been 25 μm as a standard, but in the present invention, even if the thickness is 20 μm or less, sufficient performance as a pressure-sensitive adhesive layer To demonstrate.

  When the polarizing plate provided with the pressure-sensitive adhesive layer defined in the present invention is attached to a liquid crystal cell to form a liquid crystal panel, and when there is some trouble and the polarizing plate is peeled off from the liquid crystal cell, the pressure-sensitive adhesive layer is Because the surface of the liquid crystal cell that has been peeled off with the polarizing plate and is in contact with the pressure-sensitive adhesive layer hardly causes fogging or adhesive residue, the polarizing plate with the pressure-sensitive adhesive layer is attached again to the liquid crystal cell after peeling. Is easy. That is, it is excellent in so-called reworkability.

[Polarizer]
Each of the first polarizing plate 21 and the second polarizing plate 22 shown in FIG. 1 transmits linearly polarized light having a certain vibration surface out of light perpendicularly incident on the surface thereof, and has a vibration surface orthogonal to that. A polarizing film that absorbs linearly polarized light is included. Such a polarizing film is usually produced by adsorbing and orienting a dichroic dye composed of iodine or a dichroic organic dye on a polyvinyl alcohol resin film. The polarizing film itself is prone to tear because it is highly stretched to orient the dichroic dye. Therefore, usually, a transparent protective layer is provided on at least one surface of the polarizing film as described above to form a polarizing plate.

  Examples of the layer structure of a polarizing plate provided with a pressure-sensitive adhesive layer for adhering to a liquid crystal cell, suitable for application to the present invention, are shown in cross-sectional schematic views in FIGS. 2 to 5, reference numerals 20 are given to the polarizing plates to mean both the first polarizing plate 21 and the second polarizing plate 22 shown in FIG. 1. Moreover, in order to mean both the 1st adhesive layer 31 and the 2nd adhesive layer 32 which are shown in FIG. 1, the reference mark 30 is attached | subjected to the adhesive layer used for sticking to a liquid crystal cell. . The first polarizing plate 21 and the second polarizing plate 22 may have the same layer configuration or different layer configurations.

  As shown in FIG. 2, one form of the polarizing plate 20 is one in which transparent protective layers 26 and 27 are provided on both surfaces of a polarizing film 25, and a surface (in the illustrated example) that is attached to the liquid crystal cell. On the outer surface of the transparent protective layer 27, a pressure-sensitive adhesive layer 30 for attaching a liquid crystal cell is provided. In another form, as shown in FIG. 3, transparent protective layers 26 and 27 are provided on both surfaces of the polarizing film 25, and the surface on the liquid crystal cell side (the outer surface of the transparent protective layer 27 in the illustrated example) An optical compensation film 28 having a phase difference film as a representative example is laminated, and an adhesive layer 30 to be attached to a liquid crystal cell is provided outside the optical compensation film 28. In this case, an interlayer adhesive 29 is usually used for bonding the transparent protective layer 27 and the optical compensation film 28.

  As shown in FIG. 4, the polarizing plate 20 is provided with a transparent protective layer 26 on one side of a polarizing film 25. When the polarizing plate 20 is directly attached to a liquid crystal cell in this state, the polarizing film An adhesive layer 30 to be attached to the liquid crystal cell is provided on the other surface of 25. In another form, as shown in FIG. 5, a transparent protective layer 26 is provided on one side of a polarizing film 25, and a retardation film is used as a representative example via an interlayer adhesive 29 on the other side. The optical compensation film 28 is laminated, and an adhesive layer 30 to be attached to the liquid crystal cell is provided outside the optical compensation film 28.

  The transparent protective layers 26 and 27 can be formed by, for example, resin coating, but in general, the transparent protective layers 26 and 27 are often configured by pasting a transparent protective film through an adhesive. As a transparent protective film, various transparent resin films, such as a cellulose resin film, an olefin resin film, an olefin resin film, an acrylic resin film, a polyester resin film, can be used, for example.

  When a cellulose resin film is used as the protective film, a cellulose acetate resin in which at least a part of cellulose is acetated is suitable. For example, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate and the like can be mentioned. As such a cellulose acetate-based resin film, an appropriate commercially available product can be used. For example, “Fujitac TD80”, “Fujitac TD80UF” and “Fujitac TD80UZ” sold by FUJIFILM Corporation, “KC8UX2M” and “KC8UY” sold by Konica Minolta Opto Co., Ltd. Name) is preferred.

  The olefin resin is, for example, a thermoplastic resin having a cycloolefin monomer unit represented by norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene) or a derivative thereof. In addition to being a hydrogenated product of a ring-opening polymer or a ring-opening copolymer using two or more kinds of cycloolefins, addition copolymers of cycloolefins with aromatic compounds having a chain olefin or vinyl group It may be. In addition, a polar group may be introduced.

  Examples of commercially available thermoplastic olefin resins include “ARTON” (ARTON) sold by JSR Corporation, “ZEONEX” and “ZEONOR” (ZEONOR) sold by Nippon Zeon Corporation. ), “TOPAS” produced by TOPAS ADVANCED POLYMERS GmbH in Germany and sold by Polyplastics Co., Ltd. in Japan, “Apel” sold by Mitsui Chemicals Co., Ltd. (all trade names) There is.

  In forming such a film by forming such an olefin-based resin, a known film forming method such as a solvent casting method or a melt extrusion method is appropriately used for film formation. A formed olefin resin film and an olefin resin film further stretched and provided with a phase difference are also commercially available. For example, "Arton Film" sold by JSR Corporation, "Zeonor Film" sold by Nippon Zeon Corporation, "Essina" and "SCA40" sold by Sekisui Chemical Co., Ltd. (Both are trade names) and these can be used preferably.

  As described above, the protective film as described above is laminated on at least one surface of the polarizing film, usually at least on the surface farther from the liquid crystal cell 10 with reference to FIG.

  As shown in FIG. 2, a transparent protective film 27 can be laminated on the surface of the polarizing film 25 on the liquid crystal cell side via an adhesive. Further, as shown in FIG. The optical compensation film 28 can also be bonded via 29. Further, on this surface, an adhesive layer 30 to be adhered to a liquid crystal cell is directly formed as shown in FIG. 4, or an optical compensation film 28 is bonded through an interlayer adhesive 29 as shown in FIG. You can do it. Here, the pressure-sensitive adhesive layer 30 directly attached to the liquid crystal cell 10 is preferably formed from the pressure-sensitive adhesive composition specified in the present invention described above, but the optical compensation film 28 is bonded to the protective film 27. Alternatively, the interlayer adhesive 29 for bonding the optical compensation film 28 to the polarizing film 25 may be formed from other adhesive compositions. The interlayer adhesive 29 used for adhering the optical compensation film 28 to the protective film 27 or the polarizing film 25 is, for example, in the above description except that the aromatic ring-containing monomer (A-2) is not copolymerized. It can be formed from an acrylic pressure-sensitive adhesive composition in which a cross-linking agent is blended with a similar acrylic resin.

  In the liquid crystal panel shown in FIG. 1, at least one of the first polarizing plate 21 and the second polarizing plate 22 has a configuration of protective film 26 / polarizing film 25 / protective film 27 as shown in FIG. Is preferred.

From the viewpoint of ease of providing the surface treatment layer and optical characteristics, the protective film 26 disposed on the side far from the liquid crystal cell of the polarizing film 25 is composed of a cellulose acetate resin film including a triacetyl cellulose film. It is preferable. In particular, a cellulose acetate-based resin film having an in-plane retardation value R ₀ in the range of ₀ to 20 nm and a thickness direction retardation value R _th in the range of 20 to 80 nm should be directly produced by the solvent casting method. Therefore, it is one of the preferable protective films disposed on the side far from the liquid crystal cell.

Here, the film exhibiting optical anisotropy, in-plane retardation value R ₀ and the thickness direction retardation R _th is the refractive index in a slow axis direction in a plane and n _x, the slow axis in the plane When the refractive index in the orthogonal direction (the fast axis direction) is n _y , the refractive index in the thickness direction is n _z , and the thickness is d, the following equations (5) and (6) are used.

_{R 0 = (n x -n y} ) × d (5)
_Rth = [( _nx + _ny ) / 2- _nz ] × d (6)
In general liquid crystal display devices, an optical compensation film 28 is disposed on the liquid crystal cell side of the polarizing plate 20 as shown in FIGS. 3 and 5 in order to obtain excellent display performance. It is preferable to provide a compensation function by, for example, giving a retardation to the protective film 27 itself on the liquid crystal cell side of the polarizing plate 20 in the example. As the retardation value in the optical compensation film or the protective film provided with the retardation, an appropriate value can be arbitrarily selected according to the mode of the liquid crystal, the target image quality, and the like.

  For example, when a polarizing plate is provided with a compensation function for a vertical alignment (VA) mode liquid crystal display device, a protective film disposed on the liquid crystal cell side of the light incident side polarizing plate, and a liquid crystal cell side of the light emitting side polarizing plate. It is preferable that at least one of the protective films to be disposed has a function of a retardation film. In this case, the protective film having the function of the retardation film has a slow axis and a fast axis in the plane. The slow axis and the fast axis are in a relationship orthogonal to each other in the plane.

When an effective compensation function is given to the VA mode liquid crystal cell, at least one of the protective films 27 positioned on the liquid crystal cell side of each of the light incident side polarizing plate and the light emitting side polarizing plate is in-plane position. It is preferable that the phase difference value R ₀ is in the range of 30 to 80 nm, and the thickness direction retardation value R _th is in the range of 80 to 250 nm. Further, in this case, it is preferable that the slow axis direction of the protective film 27 having a phase difference is arranged so as to be substantially orthogonal to the absorption axis direction of the polarizing film 25 bonded thereto. It is more preferable that both of the protective films 27 positioned on the liquid crystal cell side of the polarizing plates arranged on both surfaces of the liquid crystal cell are made of films having such retardation values.

In a polarizing plate used by being attached to a VA mode liquid crystal cell, if the in-plane retardation value R ₀ of the protective film on the liquid crystal cell side is less than 30 nm, the viewing angle compensation of the polarization axis becomes insufficient, resulting in black display. There is a tendency that light omission from the oblique angle increases and the viewing angle narrows. On the other hand, if the value exceeds 80 nm, the viewing angle may be overcompensated to adversely affect light leakage. Also, the retardation value _Rth in the thickness direction, like the in-plane retardation value, tends to be in a state where the viewing angle compensation of the liquid crystal layer is insufficient if it is too small, and overcompensated if it is too large.

  The cellulose acetate-based resin film can be given an arbitrary retardation value by stretching. As a cellulose acetate resin film in which a phase difference suitable for optical compensation of a VA mode liquid crystal cell is expressed, a film in which a biaxially oriented phase difference is expressed by stretching is commercially available. For example, there are “KC8UCR-5”, “KC4FR-T”, “KC4HR-T” (all are trade names) sold by Konica Minolta Opto Co., Ltd. The cellulose acetate-based resin film provided with such a phase difference can be preferably applied as a protective film [protective film 27 in FIG. 2] on the liquid crystal cell side.

  In addition, the olefin resin film can be given an arbitrary retardation value by stretching. Stretching is usually performed continuously while unwinding the film from the roll, and is stretched in the heating furnace in the direction of travel of the roll or in a direction perpendicular to the direction of travel. As the temperature of the heating furnace, a range from the vicinity of the glass transition temperature of the cycloolefin resin to the glass transition temperature + 100 ° C. is usually employed. Preferably, the film is stretched so that the direction perpendicular to the traveling direction of the roll is the main stretching axis, that is, the stretching is mainly performed in the transverse direction. The draw ratio is usually about 1.1 to 6 times, preferably 1.1 to 3.5 times in the main draw axis direction. A cycloolefin resin film to which such a phase difference is imparted can also be preferably applied as a protective film [protective film 27 in FIG. 2] on the liquid crystal cell side.

In one preferred form of the VA mode liquid crystal panel, at least one of the first polarizing plate 21 and the second polarizing plate 22 shown in FIG. 1 has a protective film 26 / polarizing film 25 as shown in FIG. / The protective film 27 is configured. And in one more preferable form in this case, the protective film 26 which is the side far from the liquid crystal cell among the two protective films sandwiching the polarizing film 25 has an in-plane retardation value R _{0 of 0} to 20 nm and a thickness direction. the retardation value _{R th} is composed of a cellulose acetate-based resin is 20 to 80 nm, the protective film 27 made of the liquid crystal cell side is a retardation value in the thickness direction retardation value _{R 0} in the plane 30 to 80 nm R _It is composed of a cellulose acetate resin whose _th is 80 to 250 nm.

On the other hand, in the case where a polarizing plate is provided with an effective compensation function for a liquid crystal cell in a transverse electric field (IPS) mode, each of the light incident side polarizing plate and the light emitting side polarizing plate is a protective film positioned on the liquid crystal cell side. At least one of the in-plane retardation value R ₀ is preferably in the range of ₀ to 10 nm, the thickness direction retardation value R _th is in the range of −25 to 25 nm, and R _th is substantially zero. It is more preferable to use a non-oriented film. It is even more preferable that both of the protective films positioned on the liquid crystal cell side of the polarizing plates arranged on both surfaces of the liquid crystal cell have such retardation values. By setting the in-plane retardation value R ₀ and the thickness direction retardation value R _th within the above ranges, the amount of light leakage in the oblique direction is small, and clear display is possible.

As a film suitable for compensation of the IPS mode as described above, a cellulose acetate resin film or a cycloolefin resin film can be preferably used. Films with substantially zero retardation value R _th in the thickness direction by adding a retardation reducing agent in a cellulose acetate-based resin are commercially available, for example, sold by Konica Minolta Opto (Ltd.) "KC4UEW "Or" KC4UESW "(both are trade names). Such a cellulose acetate-based resin film in which the phase difference is controlled can be preferably applied as a protective film [protective film 27 in FIG. 2] on the liquid crystal cell side.

Further, as the olefin resin film in which the in-plane retardation value R ₀ and the thickness direction retardation value R _th are reduced as much as possible, the in-plane and thickness remaining in the film with respect to the above-described commercially available olefin resin film. What was produced by methods, such as relaxing the distortion of a direction by heat processing, can be applied.

Also in the IPS mode liquid crystal panel, in one preferred embodiment, at least one of the first polarizing plate 21 and the second polarizing plate 22 shown in FIG. 1 is a protective film 26 / polarizing film as shown in FIG. 25 / protective film 27. In a more preferred form in this case, the protective film 26 on the side farther from the liquid crystal cell among the two protective films sandwiching the polarizing film 25 has an in-plane retardation value R _{0 of 0} to 20 nm and a thickness direction position. The protective film 27 made of a cellulose acetate-based resin having a retardation value of 20 to 80 nm and on the liquid crystal cell side has an in-plane retardation value R _{0 of 0} to 10 nm and a thickness direction retardation value R _th of −25. It is comprised with the cellulose acetate type-resin which is -25nm.

  When at least one of the first polarizing plate 21 and the second polarizing plate 22 shown in FIG. 1 has the configuration of the protective film 26 / polarizing film 25 / protective film 27 as shown in FIG. Then, the protective film 26 on the side far from the liquid crystal cell is made of cellulose acetate resin, and the protective film 27 on the liquid crystal cell side is made of olefin resin.

  When the liquid crystal cell side protective film of the light incident side polarizing plate has a retardation, and when the liquid crystal cell side protective film of the light emitting side polarizing plate has a phase difference, the polarizing film and the liquid crystal cell constituting the light incident side polarizing plate The side protective film, and the polarizing film and the liquid crystal cell side protective film constituting the light emission side polarizing plate are such that the absorption axis of the polarizing film and the in-plane slow axis of the protective film are substantially in parallel or orthogonal to each other. What is necessary is just to arrange. In particular, it is preferable from the viewpoint of productivity to arrange the two so as to be substantially orthogonal. That is, when the liquid crystal cell side protective film of the light incident side polarizing plate and / or the liquid crystal cell side protective film of the light emitting side polarizing plate is constituted by a refractive index anisotropic film having a phase difference, the transverse stretching is mainly used. It is preferable to produce by stretching operation. In this case, since the slow axis is the width direction of the roll film, the polarizing film and roll-to-roll bonding are performed in which the longitudinal direction (flow direction) of the roll film is the absorption axis. By doing so, the absorption axis of the polarizing film and the slow axis of the protective film become orthogonal.

  The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  In the protective film used for the polarizing plate, it is preferable that the thickness is small, but if it is too thin, the strength tends to decrease and the processability tends to be poor, and if it is too thick, the transparency decreases or the weight of the polarizing plate. Tend to grow. From such a viewpoint, the thickness of the protective film is usually 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm in the case of a protective film made of a cycloolefin resin, and from the cellulose acetate resin. In the case of the protective film to be formed, it is usually 20 to 200 μm, preferably 30 to 150 μm, more preferably 40 to 100 μm.

The protective film that constitutes the polarizing plate is a surface that is subjected to surface treatment such as antiglare treatment, hard coat treatment, antistatic treatment, antireflection treatment on the surface opposite to the surface to be attached to the polarizing film. Also good. Moreover, the coating layer which consists of a liquid crystalline compound, its high molecular weight compound, etc. may be formed in the surface on the opposite side to the surface stuck to the polarizing film of a protective film.
[Liquid Crystal Display]
The liquid crystal panel shown in FIG. 1 can be a liquid crystal display device in which a backlight is disposed outside either the first polarizing plate 21 or the second polarizing plate 22. Various known optical layers such as a condensing layer, a light diffusion layer, and a brightness enhancement layer may be disposed between the backlight and the polarizing plate in accordance with display characteristics required for the liquid crystal display device.

  The visual size of the liquid crystal display device using the liquid crystal panel of the present invention is the occurrence of white spots due to the contraction of the polarizing plate when the liquid crystal panel in a state where the polarizing plate is bonded to the glass cell for liquid crystal display is exposed to high temperature. From the viewpoint of suppressing the thickness, it is set to 350 mm × 650 mm or more.

  A liquid crystal display device using the liquid crystal panel of the present invention includes, for example, a notebook type, a desktop type, a personal computer liquid crystal display including a personal digital assistant (PDA), a television, an in-vehicle display, an electronic dictionary, It can be used for digital cameras, digital video cameras, electronic desk calculators, watches, and the like. This is particularly effective for liquid crystal televisions and liquid crystal displays for personal computers.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “parts” and “%” representing the amounts used or contents are based on weight unless otherwise specified.

  In the following examples, the weight average molecular weight and the number average molecular weight are the GPC apparatus, and four “TSKgel XL” made by Tosoh Corporation as a column and Showa Denko Co., Ltd. sold by Shoko Tsusho Co., Ltd. One “Shodex GPC KF-802” is connected in series, a total of 5 are connected in series, tetrahydrofuran is used as the eluent, sample concentration is 5 mg / mL, sample introduction amount is 100 μL, temperature is 40 ° C., flow rate is 1 mL / min. It is the value measured by standard polystyrene conversion on condition of this.

First, the manufacture example of the acrylic resin used as the main component of an adhesive composition is shown.
[Polymerization Example 1]
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 81.8 parts of ethyl acetate, 98.4 parts of butyl acrylate as (A-1), 2-phenoxy acrylate as (A-3) 1.0 part of ethyl and 0.6 part of acrylic acid were charged, and the internal temperature was raised to 55 ° C. while substituting air in the apparatus with nitrogen gas so as not to contain oxygen. Thereafter, a total amount of a solution obtained by dissolving 0.14 part of azobisisobutyronitrile as a polymerization initiator in 10 parts of ethyl acetate was added. The temperature was maintained at this temperature for 1 hour after the addition of the initiator, and then ethyl acetate was continuously added into the reaction vessel at an addition rate of 17.3 parts / hr while maintaining the internal temperature at 54 to 56 ° C. When the concentration reached 35%, the addition of ethyl acetate was stopped, and the temperature was kept at this temperature until 12 hours had elapsed from the start of the addition of ethyl acetate. Finally, ethyl acetate was added to adjust the acrylic resin concentration to 20%. The obtained acrylic resin had a polystyrene equivalent weight average molecular weight Mw by GPC of 1,480,000. This is designated as acrylic resin A.

[Polymerization Example 2]
Acetic acid of acrylic resin in the same manner as in Polymerization Example 1 except that the monomer composition was changed to 98.0 parts butyl acrylate as (A-1) and 2.0 parts acrylic acid as (A-3). An ethyl solution was obtained. The obtained acrylic resin is referred to as “acrylic resin B”.

[Polymerization Examples 3 to 4]
The monomer composition was changed as shown in Table 1, and the others were the same as in Polymerization Example 1 to obtain an ethyl acetate solution of an acrylic resin. The acrylic resins are referred to as acrylic resins C to D as described in Table 1.

  Next, examples and comparative examples in which pressure-sensitive adhesive compositions were prepared using acrylic resins A to D produced in Polymerization Examples 1 to 4, applied to polarizing plates, and further prepared for liquid crystal panels were shown. . In these Examples and Comparative Examples, the following were used as the crosslinking agent, the silane compound, and the active energy ray-curable compound (all are trade names).

<Crosslinking agent>
Coronate L: Obtained from an ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75%), Nippon Polyurethane Co., Ltd.

  Coronate HXR: Isocyanurate of hexamethylene diisocyanate, obtained from Nippon Polyurethane Co., Ltd.

<Silane compounds>
KBM-403: Glycidoxypropyltrimethoxysilane (liquid), obtained from Shin-Etsu Chemical Co., Ltd.

<Active energy ray-curable compound>
Tetrad C: 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, obtained from Mitsubishi Gas Chemical Co., Inc.

  A-DOG: It has the structure of the following formula. Obtained from Shin-Nakamura Chemical Co., Ltd.

<Photopolymerization initiator>
Irgacure 500: A mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a mass ratio of 1: 1, obtained from BASF Japan.

[Example 1]
(A) Preparation of pressure-sensitive adhesive composition To 100 parts of the solid content of acrylic resin A (20% ethyl acetate solution) obtained in Polymerization Example 1, 0.6 part of the above-mentioned silane compound (KBM-403), light 1.9 parts of a polymerization initiator (Irgacure 500), 3.8 parts of a crosslinking agent (Coronate L) and 25 parts of an active energy ray-curable compound (A-DOG) are mixed, and the solid content concentration is 13%. Ethyl acetate was added so as to obtain an adhesive composition.

(B) Preparation of polarizing plate with pressure-sensitive adhesive The polyethylene terephthalate film (trade name “PET 3811”, obtained from Lintec Co., Ltd., referred to as a separator) was subjected to release treatment from the pressure-sensitive adhesive composition prepared in (a) above. The release-treated surface was coated with an applicator so that the thickness after drying was 20 μm, and dried at 90 ° C. for 1 minute to prepare a sheet-like pressure-sensitive adhesive. Next, on one side of a polarizing plate having a three-layer structure in which both sides of a polarizing film in which iodine is adsorbed and oriented to polyvinyl alcohol are sandwiched between protective films made of triacetyl cellulose, the side opposite to the separator of the sheet-like adhesive obtained above After the surfaces (adhesive side) were bonded together with a laminator, UV light was applied to the polarizing plate with adhesive using a Fusion UV lamp system (Fusion UV Systems Co., Ltd.) D bulb with an integrated light quantity of 1500 mJ / cm ² to adhere The agent was cured. Next, the film was cured for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 65% to prepare a polarizing plate with an adhesive. For the pressure-sensitive adhesive layer after curing, the gel fraction was measured by the method described above, and the results are summarized in Table 2.

(C) Bonding to glass substrate and evaluation The polarizing plate with an adhesive produced in the above (b) was cut into a size of 400 mm × 710 mm. Next, what peeled off the separator from this cut polarizing plate was bonded on the adhesive surface of a glass substrate for liquid crystal cells ["Eagle 2000" (trade name) manufactured by Corning). At this time, the absorption axis of the second polarizing plate is the first polarized light on the other surface of the glass substrate so that the absorption axis of the first polarizing plate is parallel to the long side of the glass substrate on one side of the glass substrate. It stuck so that it might orthogonally cross the absorption axis of a board. The obtained laminate was subjected to a heat resistance test for 96 hours under drying at a temperature of 80 ° C. Thereafter, the appearance of white spots when light was incident from one polarizing plate side was visually observed. The results were classified according to the following criteria, and are shown in the column of “White Leakage (80 ° C. Drying)” in Table 2.

<Expression of white spots>
1: White spots are hardly noticeable.
2: White spots are slightly noticeable.
3: White spots are noticeable.

  In addition, a heat resistance test (denoted as “heat resistance” in Table 2) stored for 300 hours under drying at a temperature of 80 ° C., a temperature of 60 ° C., relative to a laminate having polarizing plates attached to both surfaces of a glass substrate in the same manner as described above. One cycle of humidity and heat resistance test (stored as “moisture and heat resistance” in Table 2) for storage for 300 hours at 90% humidity, and the process of lowering the temperature from −70 ° C. to 70 ° C. and then increasing the temperature to 70 ° C. As (1 hour), a heat shock resistance test (represented as “HS resistance” in Table 2) was repeated for 100 cycles. And the laminated body after each test was observed visually, the result was classified by the following references | standards, and it put together in the column of "Durability" of Table 2.

<Evaluation criteria for heat resistance test, moist heat resistance test and heat shock resistance test>
1: Almost no change in appearance such as floating, peeling or foaming.
2: Appearance changes such as floating, peeling, and foaming are slightly noticeable.
3: Appearance changes such as floating, peeling and foaming are remarkably recognized.
(D) Evaluation of reworkability of polarizing plate with pressure-sensitive adhesive The reworkability of the polarizing plate with pressure-sensitive adhesive prepared in the above (b) was evaluated as follows. First, the polarizing plate with the adhesive was cut into a test piece having a size of 25 mm × 150 mm. Next, this test piece was stuck on the glass substrate for liquid crystal cells on the adhesive side using a sticking device ["Lamipacker" (trade name) manufactured by Fuji Plastics Co., Ltd.], 50 ° C., 5 kg / cm ² ( (490.3 kPa) for 20 minutes. Furthermore, after heat-treating at 70 ° C. for 2 hours and subsequently storing in an oven at 50 ° C. for 48 hours, the polarizing plate was removed from this adhesion test piece at 300 mm / min in an atmosphere of 23 ° C. and 50% relative humidity. The film was peeled in the direction of 180 ° at a speed of 1, and the state of the glass plate surface was observed and classified according to the following criteria. The results are also shown in Table 2.

<Evaluation criteria for reworkability>
1: No fogging or the like is observed on the glass plate surface.
2: Cloudiness etc. are recognized on the glass plate surface.
3: The remainder of an adhesive is recognized by the glass plate surface.

[Example 2]
Acrylic resin A is changed to acrylic resin B, and 0.5 part of the above-mentioned silane compound (KBM-403), 1.5 part of photopolymerization initiator (Irgacure 500) and cross-linking are performed on 100 parts of acrylic resin B. In the same manner as in Example 1 except that 1.0 part of the agent (Coronate HXR) and 0.5 part of Tetrad C instead of A-DOG were mixed as the active energy ray-curable resin, the gel fraction, the storage elastic modulus, White spots, durability and reworkability were evaluated. The results are shown in Table 2.

[Comparative Example 1]
Acrylic resin A is changed to acrylic resins C and D, the photopolymerization initiator (Irgacure 500) is not used, the addition amount of silane compound (KBM-403) is 0.5 parts, and the crosslinking agent (Coronate L). A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of was changed to 1.8 parts.

  Thickness after drying the prepared pressure-sensitive adhesive composition on the release-treated surface of a release-treated polyethylene terephthalate film (trade name “PET 3811”, obtained from Lintec Co., Ltd., called a separator) using an applicator. Was applied to a thickness of 20 μm and dried at 90 ° C. for 1 minute to prepare a sheet-like pressure-sensitive adhesive. Next, on one side of a polarizing plate having a three-layer structure in which both sides of a polarizing film in which iodine is adsorbed and oriented to polyvinyl alcohol are sandwiched between protective films made of triacetyl cellulose, the side opposite to the separator of the sheet-like adhesive obtained above The surface (adhesive surface) was bonded together with a laminator. Next, the film was cured for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 65% to prepare a polarizing plate with an adhesive. Other than that was carried out similarly to Example 1, and evaluated the gel fraction, the storage elastic modulus, whitening, durability, and reworkability. The results are shown in Table 2.

  As can be seen from Table 2, a pressure-sensitive adhesive composition is prepared by blending a predetermined amount of a crosslinking agent with a specific range of acrylic resin having a gel fraction and a storage elastic modulus specified in the present invention. On one side of a glass cell substrate (corresponding to a liquid crystal cell or a liquid crystal display screen), one polarizing plate has the absorption axis parallel to the long side of the glass substrate, and the other polarizing plate In Examples 1 and 2 adhered so as to be crossed with a plate, results excellent in white spot prevention, durability and reworkability were obtained.

  On the other hand, Comparative Example 1 using an acrylic resin whose gel fraction and storage elastic modulus are not specified in the present invention is insufficient in white spot prevention.

  In the above examples and comparative examples, experiments were conducted by attaching polarizing plates to the front and back of a glass substrate without liquid crystal sandwiched between them, but white spots occur due to expansion and contraction of the polarizing plates caused by heat. Little affected by the presence or absence of layers. Moreover, since each test of heat resistance, moisture heat resistance, and heat shock looks at the state of the pressure-sensitive adhesive layer adhered to the glass substrate, it is not affected by the presence or absence of the liquid crystal layer in the liquid crystal cell.

  DESCRIPTION OF SYMBOLS 10 Glass cell for liquid crystal display (liquid crystal cell), 11, 12 Transparent glass substrate, 10A Long side of glass cell for liquid crystal display, 20 Polarizing plate, 21 First polarizing plate, 21A Absorption axis of first polarizing plate, 22 2nd polarizing plate, 22A Absorption axis of 2nd polarizing plate, 25 Polarizing film, 26, 27 Transparent protective layer, 28 Optical compensation film (retardation film), 29 Interlayer adhesive, 30 Adhesion sticking to liquid crystal cell Agent layer (whether first or second), 31 first adhesive layer, 32 second adhesive layer.

Claims (8)

A polarizing plate having a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin is stuck on both surfaces of a liquid crystal display glass cell via an adhesive layer so that the absorption axes of the polarizing plates are orthogonal to each other. And at least one of the pressure-sensitive adhesive layers is
(A) 100 parts of (meth) acrylic ester resin (B) 0.2 to 5 parts by weight of crosslinking agent (C) It is formed from a pressure-sensitive adhesive composition containing 0.03 to 1 part by weight of silane compound. The pressure-sensitive adhesive layer has a gel fraction of 70 to 99% by weight and a storage elastic modulus of 0.8 to 10 MPa at 23 ° C., and has a visual size of 350 mm × 650 mm or more. apparatus.   The liquid crystal display device according to claim 1, wherein the (meth) acrylic acid ester-based resin (A) is a polymer mainly composed of butyl acrylate.   The liquid crystal display device according to claim 1, wherein the (meth) acrylic ester resin (A) has a polar functional group selected from the group consisting of a free carboxyl group, a hydroxyl group, an amino group, and an epoxy ring.   The liquid crystal display device according to claim 1, wherein the crosslinking agent (B) contains an isocyanate compound.   The pressure-sensitive adhesive composition further contains an active energy ray-curable compound (D), and the pressure-sensitive adhesive layer is formed by irradiating the pressure-sensitive adhesive composition with active energy rays. The liquid crystal display device according to any one of the above.   The liquid crystal display device according to claim 1, wherein the pressure-sensitive adhesive composition further contains 0.3 to 5 parts by weight of an antistatic agent (E).   The said polarizing plate is a liquid crystal display device in any one of Claims 1-6 which has a structure where the transparent protective layer was laminated | stacked through the adhesive agent on both surfaces of the polarizing film, respectively.   The liquid crystal display device according to claim 7, wherein the transparent protective layer is made of a resin selected from a cellulose acetate-based resin and an olefin-based resin.

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