JP2011154079A - Liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel wherein a pair of polarizing plates are respectively stuck to both surfaces of a liquid crystal cell via adhesive layers and a white void can be satisfactorily suppressed. <P>SOLUTION: In the liquid crystal panel, a first polarizing plate 21 is stuck to one surface of the rectangular liquid crystal cell 10 via a first adhesive layer 31 so that an absorption axis 21A thereof is made to form 45° to a long side 10A of the liquid crystal cell and a second polarizing plate 22 is stuck to the other surface of the liquid crystal cell 10 via a second adhesive layer 32 so that an absorption axis 22A thereof is made to be orthogonal to the absorption axis 21A of the first polarizing plate. At least one of the adhesive layers 31 and 32 is formed from a composition which contains 100 pts.wt. acrylic resin to be a copolymer formed by polymerizing a monomer mixture containing 35 to 79.9 wt.% alkyl (meth)acrylate, 20 to 60 wt.% aromatic ring-containing monomer and 0.1 to 5 wt.% polar functional group-containing monomer and having weight average molecular weigh of 1,000,000 to 2,000,000 and molecular weight distribution of 3 to 7 and 0.01 to 5 pts.wt. crosslinking agent and has 50 to 99 wt.% gel fraction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel in which polarizing plates are bonded to both surfaces of 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. The display device. When the liquid crystal panel with the polarizing plate bonded to the glass cell for liquid crystal display is exposed to a high temperature in this way, the distribution of residual stress acting on the polarizing plate becomes non-uniform and stress concentration occurs on the outer periphery of the polarizing plate. As a result, a phenomenon called white spots (also referred to as “light leakage”) in which the outer peripheral portion becomes whitish when black is displayed may occur, or color unevenness may occur. Therefore, suppression of such white spots and color unevenness is required.

  As one of countermeasures, JP 2007-138056 A (Patent Document 1) describes the weight average molecular weight Mw and the number average molecular weight Mn of a resin obtained by copolymerizing an aromatic ring-containing monomer with an alkyl acrylate. A technique for suppressing light leakage by widening the molecular weight distribution represented by the ratio Mw / Mn to 10 to 50 is disclosed. By using such a pressure-sensitive adhesive, light leakage is reduced, but it is not always sufficient, and a broad molecular weight distribution may cause foaming under high temperature conditions.

  On the other hand, 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 with the dimensional change 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, when a polarizing plate with an adhesive is bonded to a glass cell for liquid crystal display to make a liquid crystal panel, if there is any deficiency, the polarizing plate should be peeled off and then a new film will be 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 reworkability is also required, which does not cause fogging.

JP 2007-138056 A

  An object of the present invention is to provide a liquid crystal panel in which a pair of polarizing plates are bonded to both surfaces of a glass cell for liquid crystal display via an adhesive layer, respectively, and white spots can be sufficiently suppressed. .

  As a result of intensive studies to solve such problems, the present inventors have found that the first polarizing plate and the second polarizing plate are respectively disposed on both surfaces of a liquid crystal display glass cell having a rectangular display screen via an adhesive layer. A plate is attached, the first polarizing plate has an absorption axis of 45 ° with respect to the long side of the glass cell, and the second polarizing plate has an absorption axis that is absorbed by the first polarizing plate. In the liquid crystal panel orthogonal to the axis, by improving the pressure-sensitive adhesive layer, white spots can be effectively suppressed and a liquid crystal panel excellent in durability can be obtained. The present inventors have found that the reworkability is excellent and have reached the present invention. Specifically, this pressure-sensitive adhesive layer contains a structural unit derived from an unsaturated monomer having (meth) acrylic acid alkyl ester as a main component and having a polar functional group, and has an aromatic ring in the molecule. It has been found that it is effective to comprise a predetermined amount of a structural unit derived from a saturated monomer and a mixture of a predetermined amount of a crosslinking agent in an acrylic resin having a narrow molecular weight distribution.

  That is, the liquid crystal panel according to the present invention is a rectangular glass cell for liquid crystal display, and the absorption axis is 45 ° with respect to the long side of the glass cell via the first adhesive layer on one side of the glass cell. The first polarizing plate stuck so as to be attached to the other surface of the glass cell via the second pressure-sensitive adhesive layer so that the absorption axis is orthogonal to the absorption axis of the first polarizing plate. And at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer comprises an acrylic resin (A) and a crosslinking agent (B) shown below. It is formed from the adhesive composition to contain, and is comprised with what has a gel fraction of 50 to 99 weight%.

(A) (A-1) 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)
(Meth) acrylic acid alkyl ester represented by 35 to 79.9% by weight,
(A-2) Unsaturated monomer having one olefinic double bond and at least one aromatic ring in the molecule (hereinafter sometimes referred to as “aromatic ring-containing monomer”) 20-60 And (A-3) an unsaturated monomer having a polar functional group (hereinafter sometimes referred to as “polar functional group-containing monomer”) 0.1 to 5% by weight
A weight average molecular weight Mw in the range of 1,000,000 to 2,000,000, and a molecular weight distribution represented by a ratio Mw / Mn between the weight average molecular weight Mw and the number average molecular weight Mn is 100 parts by weight of an acrylic resin in the range of 3 to 7, and (B) 0.01 to 5 parts by weight of a crosslinking agent.

  Thus, in the present invention, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer for adhering the first polarizing plate and the second polarizing plate disposed on both surfaces of the glass cell for liquid crystal display to the glass cell, respectively. At least one of the pressure-sensitive adhesive layers is a (meth) acrylic acid alkyl ester (A-1) represented by the above formula (I), an aromatic ring-containing monomer (A-2), and a polar functional group-containing monomer. It is formed from an acrylic resin (A) which is a copolymer of a monomer mixture containing (A-3), and a pressure-sensitive adhesive composition containing a crosslinking agent (B), and the gel fraction is within a predetermined range. By making it possible to effectively suppress white spots, both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are formed from a pressure-sensitive adhesive composition that satisfies the above requirements, Satisfying the above gel fraction is one of the reasons for suppressing white spots. Preferred.

  In these liquid crystal panels, the aromatic ring-containing monomer (A-2) is preferably an aromatic ring-containing (meth) acrylic compound represented by 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.

  In each of these liquid crystal panels, the polar functional group-containing monomer (A-3) preferably has a free carboxyl group, a hydroxyl group, an amino group, or an epoxy ring as the polar functional group.

  Furthermore, in each of these liquid crystal panels, it is preferable that the crosslinking agent (B) constituting the pressure-sensitive adhesive composition contains an isocyanate compound. In particular, when the polar functional group-containing monomer (A-3) has a polar functional group selected from the above-mentioned free carboxyl group, hydroxyl group, amino group, and epoxy ring, at least an isocyanate group is used as the crosslinking agent (B). It is preferable to use a compound.

  Furthermore, the adhesive composition for forming the adhesive layer prescribed | regulated by this invention can contain 0.03-1 weight part of (C) silane type compounds.

  In each of these liquid crystal panels, each of the first polarizing plate and the second polarizing plate can be configured as a protective film / polarizing film / protective film. In particular, at least one polarizing plate has such a layer configuration. It is preferable to do.

  In such a polarizing plate having a layer structure of protective film / polarizing film / protective film, one preferred form is a film located on the side farther from the liquid crystal display glass cell among the two protective films sandwiching the polarizing film. However, the film which consists of cellulose acetate type-resins and is located in the glass cell side for liquid crystal displays is comprised by the optical compensation film formed by application | coating of the substance which expresses optical anisotropy. The optical compensation film in this case can be a film that exhibits optical anisotropy by application and orientation of a liquid crystalline compound, a film that exhibits optical anisotropy by application of an inorganic layered compound, and the like.

  In the present invention, a pair of polarizing plates is bonded to both surfaces of the glass cell for liquid crystal display via a pressure-sensitive adhesive layer so as to be crossed Nicol, that is, the absorption axes of the two polarizing plates are orthogonal to each other, In the liquid crystal panel arranged so that the absorption axis of the polarizing plate is 45 ° with respect to the long side of the glass cell, the acrylic resin (A) for forming the pressure-sensitive adhesive layer is replaced with an aromatic ring-containing single amount. By making the copolymer containing a predetermined amount of units derived from the body (A-2) and having the weight average molecular weight Mw and the molecular weight distribution Mw / Mn in a specific range, optical properties resulting from non-uniform stress distribution Defects are prevented and white spots are suppressed.

  Moreover, the durability of the pressure-sensitive adhesive layer is improved by setting the gel fraction of the pressure-sensitive adhesive layer in the range of 50 to 99% by weight, and this liquid crystal panel is subjected to tests such as heat resistance, moisture heat resistance and heat shock resistance. The appearance change at the time is suppressed. In addition, this liquid crystal panel can be attached to the glass cell for liquid crystal display through the above-mentioned pressure-sensitive adhesive layer and then peeled off from the glass cell together with the pressure-sensitive adhesive layer if there is any problem. In addition, adhesive residue and fogging 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 the layer structure and axial angle relationship of the liquid crystal panel which concern on this invention. 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. FIG. 1 is an exploded perspective view showing the relationship between the layer configuration and the axial angle of the liquid crystal panel according to the present invention. Referring to FIG. 1, a liquid crystal panel to which the present invention is applied has a liquid crystal display glass cell 10 (hereinafter simply referred to as “liquid crystal cell” or “glass cell”) having a rectangular display surface. 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 polarized light is applied to the other side of the liquid crystal cell 10 via the second pressure-sensitive adhesive layer 32. The plate 22 is affixed. 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, and the first polarizing plate 21 has the absorption axis 21A of the liquid crystal cell 10. It is arrange | positioned so that it may become 45 degrees with respect to 10 A of long sides. Therefore, the second polarizing plate 22 is disposed so that the absorption axis 22 </ b> A is 135 ° with respect to the long side 10 </ b> A of the liquid crystal cell 10.

  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 is formed from a pressure-sensitive adhesive composition containing 0.01 to 5 parts by weight of the crosslinking agent (B) with respect to 100 parts by weight of the specific acrylic resin (A), and the gel fraction is 50 to 99 parts by weight. %.

  The first polarizing plate 21 is arranged such that the absorption axis 21A is 45 ° with respect to the long side 10A of the liquid crystal cell 10, and the second polarizing plate 22 has the absorption axis 22A of the liquid crystal cell 10. It is particularly effective to apply a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition defined in the present invention to a liquid crystal panel arranged at 135 ° with respect to the long side 10A. It was issued. By forming at least one of the pressure-sensitive adhesive layers 31 and 32 disposed on both surfaces of the liquid crystal cell 10 from the above-mentioned specific pressure-sensitive adhesive composition and making the gel fraction within a specific range, Although the effect of the period is expressed, as described above, it is possible to configure both of the pressure-sensitive adhesive layers 31 and 32 arranged on both surfaces of the liquid crystal cell 10 from such a viewpoint of suppressing white spots. Is preferable.

  Hereinafter, each member constituting the liquid crystal panel 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 horizontal electric field (In-Plane Switching: IPS) depending on the alignment method. There are various types of systems. The present invention is applied to a liquid crystal panel in which a pair of polarizing plates are arranged in crossed Nicols above and below the liquid crystal cell, and the absorption axis of one polarizing plate is arranged at 45 ° with respect to the long side of the glass cell. The Since such a liquid crystal panel is employed in a TN liquid crystal cell in which the alignment direction of the liquid crystal is rotated by 90 degrees between the two transparent glass substrates 11 and 12, the present invention provides such a TN liquid crystal cell. It is effective against. 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 them is the specific copolymer described above, and an adhesive in which a predetermined amount of a crosslinking agent (B) is blended with an acrylic resin (A) having a weight average molecular weight Mw and a molecular weight distribution Mw / Mn within a predetermined range. It is formed from an agent composition and the gel fraction is 50 to 99% by weight. Each component which comprises this adhesive composition is demonstrated.

<Acrylic resin (A)>
In the liquid crystal panel of the present invention, the acrylic resin (A) used in the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layers 31 and 32 is derived from the (meth) acrylic acid alkyl ester represented by the formula (I). Containing a structural unit as a main component, derived from a structural unit derived from an aromatic ring-containing monomer and a monomer containing a polar functional group, in addition to the structural unit derived from the (meth) acrylic acid alkyl ester Including structural units. 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 formula (I), which is the main structural unit of the acrylic 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.

Among the (meth) acrylic acid alkyl ester (A-1) represented by the formula (I), as R ₂ is an unsubstituted alkyl group, specifically, methyl acrylate, ethyl acrylate, propyl acrylate Linear alkyl acrylates, such as n-butyl acrylate, n-octyl acrylate, and lauryl acrylate; branched, such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate Alkyl acrylates; linear alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and lauryl methacrylate; isobutyl methacrylate, methacrylic acid 2-ethylhexyl acid and methacrylic acid Sookuchiru such as, such as branched alkyl methacrylate are exemplified.

  Among these, n-butyl acrylate is preferable. Specifically, among all monomers constituting the acrylic resin (A), n-butyl acrylate is 50% by weight or more and the above-described ( It is preferable that the meth) acrylic acid alkyl ester (A-1) is satisfied.

As the (meth) acrylic acid alkyl 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, Examples include ethoxymethyl acrylate, 2-methoxyethyl methacrylate, ethoxymethyl methacrylate, and the like.

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

  The unsaturated monomer (aromatic ring-containing monomer) (A-2) having one olefinic double bond and at least one aromatic ring in the molecule is a group containing an olefinic double bond ( Those having a (meth) acryloyl group are preferred. Examples thereof include benzyl (meth) acrylate, neopentyl glycol benzoate (meth) acrylate, and the like, and preferred are aromatic ring-containing (meth) acrylic compounds represented by the formula (II).

In the above formula (II) representing a suitable aromatic ring-containing (meth) acrylic compound, when R ₄ is an alkyl group, its carbon number can be about 1 to 9, and when it is also an aralkyl group, The number of carbon atoms is about 7 to 11, and in the case of an aryl group, the number of carbon atoms 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, (meth) acrylic acid 2-phenoxyethyl [compound of the above formula (II), R ₄ = H, n = 1], or (meth) acrylic acid 2- (o-phenylphenoxy) ethyl [above In formula (II), R ₄ = o-phenyl, n = 1 compound] is preferably used as one of the aromatic ring-containing monomers (A-2) constituting the acrylic resin (A).

  In the polar functional group-containing monomer (A-3), the polar functional group may be a free carboxyl group, a hydroxyl group, an amino group, a heterocyclic group including an epoxy ring, or 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 an unsaturated monomer having a hydroxyl group as one of the polar functional group-containing monomers (A-3) constituting the acrylic 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 acrylic resin (A), the amount of the structural unit derived from the (meth) acrylic acid alkyl ester (A-1) represented by the formula (I) is 35 to 79.9% by weight, preferably 50. % By weight or more, and preferably 70% by weight or less. The amount of the structural unit derived from the aromatic ring-containing monomer (A-2) is 20 to 60% by weight, preferably 25% by weight or more, more preferably 30% by weight or more, especially 35% by weight or more. Further, it is preferably 55% by weight or less, more preferably 50% by weight or less, particularly 45% by weight or less. The amount of the structural unit derived from the polar functional group-containing monomer (A-3) is 0.1 to 5% by weight, preferably 0.5% by weight or more, and preferably 3% by weight or less. It is.

  The acrylic resin (A) used in the present invention comprises (meth) acrylic acid alkyl ester (A-1), aromatic ring-containing monomer (A-2) and polarity represented by the formula (I) described above. A structural unit derived from a monomer different from the functional group-containing monomer (A-3) 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, 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. Such as cyclododecyl, methyl cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, tert-butyl cyclohexyl methacrylate, cyclohexyl phenyl methacrylate And so on.

  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;

  (Meth) acrylic acid alkyl ester (A-1), aromatic ring-containing monomer (A-2) and polar functional group-containing monomer (A-3) represented by formula (I) as described above Different monomers can be used alone or in combination of two or more. In the acrylic resin (A) used for the adhesive, (meth) acrylic acid alkyl ester (A-1), aromatic ring-containing monomer (A-2) and polar functional group-containing monomer (A-3) The structural unit derived from a different monomer is usually contained in an amount of 0 to 20 parts by weight, preferably 0 to 10 parts by weight, based on 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 acrylic resin (A) defined in the present invention has an acrylic resin different from that, for example, an acrylic resin having a structural unit derived from a (meth) acrylic acid alkyl ester of the formula (I) and containing no polar functional group You may mix and use resin etc. 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 acrylic resin (A) containing is preferably 80% by weight or more, more preferably 90% by weight or more, based on the whole acrylic resin.

  Monomer mixture containing (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) As the acrylic resin (A), a copolymer having a weight average molecular weight Mw in terms of standard polystyrene by gel permeation chromatography (GPC) in the range of 1,000,000 to 2,000,000 is employed. 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.

  The molecular weight distribution represented by the ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn is in the range of 3-7. By setting the molecular weight distribution Mw / Mn in the range of 3 to 7, it is possible to prevent defects such as white spots from occurring even when the liquid crystal panel or the liquid crystal display device is exposed to a high temperature.

  Moreover, it is preferable that the glass transition temperature of the said acrylic resin (A) exists 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 acrylic resin (A) constituting the pressure-sensitive adhesive composition can be produced by various known methods such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method. 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, diisopropylperoxydicarbonate, dipropylperoxydicarbonate, tert-butylperoxide Organic peroxides such as xineodecanoate, tert-butyl peroxypivalate, and (3,5,5-trimethylhexanoyl) peroxide; inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide An oxide etc. can be mentioned. 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 acrylic 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, a thermal polymerization initiator is added under a nitrogen atmosphere, and 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)>
A crosslinking agent (B) is mix | blended with the above acrylic resins (A), and it is set as an adhesive composition. The crosslinking agent (B) is a compound having in the molecule at least two functional groups capable of crosslinking with a structural unit derived from the polar functional group-containing monomer (A-3) in the acrylic resin (A), Specific examples thereof include an isocyanate compound, an epoxy compound, a metal chelate compound, and an aziridine compound.

  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.

  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.

  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.

  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.

  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 0.01-5 weight part with respect to 100 weight part of acrylic resins (A). The amount of the crosslinking agent (B) is preferably about 0.1 to 5 parts by weight, more preferably about 0.2 to 3 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is preferable that the amount of the crosslinking agent (B) with respect to 100 parts by weight of the acrylic resin (A) is 0.01 parts by weight or more, particularly 0.1 parts by weight or more because the durability of the pressure-sensitive adhesive layer tends to be improved. Moreover, it is preferable that it is 5 parts by weight or less because white spots on the liquid crystal panel are not noticeable.

<Other components constituting the 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 usually 0.01 to 10 parts by weight with respect to 100 parts by weight of the nonvolatile content of the acrylic resin (A) (the total amount when two or more types are used). The ratio is preferably about 0.03 to 1 part by weight. Adhesiveness between the pressure-sensitive adhesive layer and the glass cell is improved when the amount of the silane compound relative to 100 parts by weight of the acrylic resin (A) is 0.01 parts by weight or more, particularly 0.03 parts by weight or more. To preferred. Moreover, it is preferable that the amount is 10 parts by weight or less, particularly 1 part by weight or less because bleeding out of the silane compound tends to be suppressed from the pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive composition described above may further contain a crosslinking catalyst, weathering stabilizer, tackifier, plasticizer, softener, dye, pigment, inorganic filler, antistatic agent, resin other than acrylic resin, and the like. . It is also useful to add an ultraviolet curable compound to the pressure-sensitive adhesive and cure it by irradiating it with ultraviolet light after forming the pressure-sensitive adhesive layer to form a harder pressure-sensitive adhesive layer. 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 can be mixed with essential acrylic resin (A) and cross-linking agent (B) in a state dissolved in a solvent as necessary to obtain a pressure-sensitive adhesive composition. . This can be applied on a suitable substrate and dried to form an adhesive layer.

<Gel fraction of adhesive layer>
In the present invention, as described above, the pressure-sensitive adhesive layer has a gel fraction of 50 to 99% by weight. When the gel fraction of the pressure-sensitive adhesive layer is 50% by weight or more, the durability of the pressure-sensitive adhesive layer is improved, and when the gel fraction is 99% by weight or less, it is preferable because the production is easy. This gel fraction is preferably 60% by weight or more. Here, the gel fraction is a value measured according to the following (I) to (IV).

(I) An adhesive layer having an area of about 8 cm × about 8 cm and a metal mesh made of SUS304 (with a weight of Wm) of about 10 cm × about 10 cm are bonded together.
(II) Weigh the pasted material obtained in (I) above, weigh it Ws, then fold it 4 times to wrap the adhesive layer and weigh it with a stapler (stapler). The weight is Wb.
(III) The mesh stapled in (II) 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.
(IV) The mesh is taken out from the glass container, dried at 120 ° C. for 24 hours, weighed, the weight is taken as Wa, and the gel fraction is calculated based on the following formula.
Gel fraction (% by weight) = [{Wa− (Wb−Ws) −Wm} / (Ws−Wm)] × 100

  The gel fraction of an adhesive layer can be adjusted with the kind of acrylic resin (A) which is an active ingredient of an adhesive composition, and the quantity of a crosslinking agent (B), for example. Specifically, if the amount of the polar functional group-containing monomer (A-3) in the acrylic resin (A) is increased or the amount of the crosslinking agent (B) in the pressure-sensitive adhesive composition is increased, the gel content Since the rate increases, the gel fraction may be adjusted by the amount of the polar functional group-containing monomer and / or the crosslinking agent. About the polar functional group containing monomer (A-3), the quantity of the structural unit derived from the said polar functional group containing monomer (A-3) in an acrylic resin (A) is 0.1-5 weight. From the range of%, the combination with other components constituting the acrylic resin (A), and further the combination with the type and amount of the cross-linking agent may be selected and adjusted so that the gel fraction falls within the above 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 acrylic resin which comprises an adhesive layer is 0.1-5. It is preferable to select according to the kind of acrylic resin from the range of about parts by weight.

  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, for example, a film made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, and the like, and the bonding surface with the pressure-sensitive adhesive layer of the substrate is separated by a silicone treatment. It can be configured with a mold treatment.

  The thickness of the pressure-sensitive adhesive layers 31 and 32 is not particularly limited, but 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 dimensions of the polarizing plate bonded thereto change. 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 attached to the glass cell for liquid crystal display has been 25 μm as a standard. However, in the present invention, even if the thickness is 20 μm or less, sufficient performance as a pressure-sensitive adhesive layer is achieved. 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 there is some inconvenience 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.

  An example of the layer structure of a polarizing plate provided with an adhesive layer for adhering to a liquid crystal cell, which is suitable for application to the present invention, is shown in a schematic cross-sectional view in FIG. In FIG. 2, in order to mean both the 1st polarizing plate 21 and the 2nd polarizing plate 22 which are shown in FIG. 1, the reference mark 20 is attached | subjected to the polarizing plate. 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.

  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 as shown in FIG. In this example, an adhesive layer 30 for attaching a liquid crystal cell is provided on the outer surface of the transparent protective layer 27. In another form, as shown in FIG. 2 (B), transparent protective layers 26 and 27 are provided on both surfaces of the polarizing film 25, and the surfaces on the liquid crystal cell side (the outer surface of the transparent protective layer 27 in the illustrated example). Further, an optical compensation film 28 having a retardation 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. 2 (C), another form of the polarizing plate 20 is provided with a transparent protective layer 26 on one side of the polarizing film 25. In this state, the polarizing plate 20 is directly attached to a liquid crystal cell. The pressure-sensitive adhesive layer 30 to be attached to the liquid crystal cell is provided on the other surface of the polarizing film 25. In another form, as shown in FIG. 2D, a transparent protective layer 26 is provided on one side of the polarizing film 25, and a retardation film is provided on the other side through an interlayer adhesive 29. An optical compensation film 28 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.

  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, a cycloolefin resin film, an acrylic resin film, a polyester resin film, can be used, for example.

  In particular, in a polarizing plate bonded to a TN liquid crystal cell to which the present invention is suitably applied, a cellulose acetate-based resin film is preferably used as the protective film 26 on the side far from the liquid crystal cell. The cellulose acetate-based resin is one in which at least a part of cellulose is acetated, and examples thereof include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and the like. 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 Fuji Film Co., Ltd., “KC8UX2M” and “KC8UY” sold by Konica Minolta Opto Co., Ltd. Name) is preferred.

  The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film. The saponification treatment is performed by immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

  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 made of cellulose acetate-based resin is usually 20 to 200 μm, preferably 30 to 150 μm, and more preferably 40 to 100 μm.

  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), a transparent protective film 27 can be laminated on the surface on the liquid crystal cell side of the polarizing film 25 via an adhesive, and as shown in FIG. 2 (B), The optical compensation film 28 can also be bonded to the outside via an interlayer adhesive 29. Further, on this surface, an adhesive layer 30 to be adhered to the liquid crystal cell is directly formed as shown in FIG. 2 (C), or the optical layer is interposed through the interlayer adhesive 29 as shown in FIG. 2 (D). The compensation film 28 can be bonded. 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 a protective film 26 / a polarizing film 25 / a protective film 27 as shown in FIG. It is preferable that

  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, as described above, cellulose acetate including triacetyl cellulose. It is preferable to use a film made of a resin. In particular, a cellulose acetate-based resin film having an in-plane retardation value Ro in the range of 0 to 20 nm and a thickness direction retardation value Rth in the range of 20 to 80 nm can be directly produced by a solvent casting method. Therefore, it is one of the preferable protective films arranged on the side far from the liquid crystal cell.

Here, the film exhibiting optical anisotropy, in-plane retardation value Ro and the thickness direction retardation value Rth is orthogonal refractive index in a slow axis direction in a plane n _x, the slow axis in the plane It is defined by the following formulas (1) and (2) where n _{y is} the refractive index in the direction (fast axis direction), n _{z is} the refractive index in the thickness direction, and d is the thickness.
_{Ro = (n x -n y)} × d (1)
Rth = _{[(n x + n y) /} 2-n z ] × d (2)

  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. 2B and 2D 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 shown in FIG. 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.

  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 composed of an optically anisotropic film having a phase difference, stretching mainly composed of transverse stretching. It is preferable to manufacture by operation, and in this case, the slow axis is the width direction of the roll film, so that the roll film is bonded to the polarizing film whose longitudinal direction (flow direction) is the absorption axis. Thus, the absorption axis of the polarizing film and the slow axis of the protective film are orthogonal to each other.

  Further, the protective film 26 located on the side far from the liquid crystal cell is composed of a film made of cellulose acetate resin, and the protective film 27 located on the liquid crystal cell side is formed by application of a substance that exhibits optical anisotropy. It is also a preferred form that the optical compensation film is used. In this case, as described above, the cellulose acetate-based resin film serving as the protective film 26 positioned on the side far from the liquid crystal cell has an in-plane retardation value Ro in the range of 0 to 20 nm, and a retardation value Rth in the thickness direction. Is preferably in the range of 20 to 80 nm. On the other hand, the optical compensation film to be the protective film 27 positioned on the liquid crystal cell side is, for example, one that exhibits optical anisotropy by coating / alignment of a liquid crystalline compound, or optical anisotropy by coating an inorganic layered compound. It can be composed of expressed ones.

  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. In particular, it is effective to use a film that has been subjected to such a surface treatment for the protective film that is on the side farther from the liquid crystal cell of the viewing side polarizing plate.

[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.

  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.

  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 is 4 columns of “TSKgel XL” manufactured by Tosoh Corp. as a column in a GPC device and “Shodex GPC sold by Showa Denko Co., Ltd. sold by Shoko Tsusho Co., Ltd.” One KF-802 ”, 5 in total, are arranged 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.

  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, 78.6 parts of butyl acrylate as (A-1), 2-phenoxy acrylate as (A-2) 20.0 parts of ethyl, 1.0 part of 2-hydroxyethyl acrylate and 0.4 part of acrylic acid as (A-3) were charged, and the inside of the apparatus was replaced with nitrogen gas to make it oxygen-free. The temperature was raised to 55 ° C. Thereafter, a total amount of a solution prepared by dissolving 0.14 part of azobisisobutyronitrile as a polymerization initiator in 10 parts of ethyl acetate was added. The temperature was kept at this temperature for 1 hour after the initiator was added, 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 resin concentration reached 35%, the addition of ethyl acetate was terminated, and the temperature was maintained at this temperature until 12 hours passed from the start of 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 of 1,370,000 and Mw / Mn of 4.4 by GPC. This is designated as acrylic resin A. The structural unit derived from 2-phenoxyethyl acrylate which is an aromatic ring-containing monomer in acrylic resin A is 20%, and the structural unit derived from 2-hydroxyethyl acrylate which is a hydroxyl group-containing monomer is The structural unit derived from acrylic acid which is 1% and carboxyl group-containing monomer is 0.4%.

[Polymerization Examples 2 to 5]
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 weight average molecular weights Mw and Mw / Mn in terms of polystyrene by GPC of the obtained acrylic resins are as shown in Table 1, and the acrylic resins are referred to as acrylic resins B to E as shown in Table 1. In addition, the polymerization examples 4 and 5 are examples in which the amount of the aromatic ring-containing monomer is not satisfying the requirements of the acrylic resin (A) defined in the present invention.

  Next, Examples and Comparative Examples in which a pressure-sensitive adhesive composition was prepared using the acrylic resin produced above, applied to a polarizing plate, and a liquid crystal panel compatible product were produced. In these examples and comparative examples, the following were used as the crosslinking agent and the silane compound (both 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.
<Silane compounds>
KBM-403: Glycidoxypropyltrimethoxysilane (liquid), obtained from Shin-Etsu Chemical Co., Ltd.

[Examples 1-3 and Comparative Examples 1-2]
(A) Preparation of pressure-sensitive adhesive composition For each 100 parts of solid content of 20% ethyl acetate solution of acrylic resins A to E obtained in Polymerization Examples 1 to 5, 0 silane compound (KBM-403) was added. .5 parts and a crosslinking agent (Coronate L) were mixed in respective amounts shown in Table 2, and ethyl acetate was added so that the solid content concentration was 13% to prepare a pressure-sensitive adhesive composition.

(B) Preparation of polarizing plate with pressure-sensitive adhesive Each of the pressure-sensitive adhesive compositions prepared in (a) above was obtained from a release-treated polyethylene terephthalate film (trade name “PET 3811”, Lintec Corporation, The sheet-like pressure-sensitive adhesive was prepared by applying an applicator to the mold-release treated surface so that the thickness after drying was 20 μm and drying at 90 ° C. for 1 minute. 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 These surfaces (adhesive surface) were pasted together with a laminator and then 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.

(C) Bonding to glass substrate and evaluation The separator is peeled off from the polarizing plate with the adhesive prepared in (b) above on both sides of the glass substrate for liquid crystal cell ["Eagle XG" (trade name) manufactured by Corning]. The paste was pasted on the adhesive side. At this time, the absorption axis of the second polarizing plate is on the other side of the glass substrate so that the absorption axis of the first polarizing plate is 45 ° with respect to the long side of the glass substrate on one side of the glass substrate. It stuck so that it might be orthogonal to the absorption axis of one polarizing plate. 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 (Dried at 80 ° C.)” in Table 2.

<Expression of white spots>
A: No white spots are observed.
○: White spots are hardly noticeable.
Δ: White spots are slightly noticeable.
X: 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. 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>
A: No change in appearance such as floating, peeling or foaming is observed.
○: Almost no change in appearance such as floating, peeling or foaming.
Δ: Appearance changes such as floating, peeling and foaming are slightly noticeable.
X: Remarkable changes in appearance such as floating, peeling, foaming, etc.

(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 an adhesive was cut into a test piece having a size of 25 mm × 150 mm. Next, the test piece was attached to the glass substrate for a liquid crystal cell on the pressure-sensitive adhesive side using a sticking device ["Lami Packer" (trade name) manufactured by Fuji Plastics Co., Ltd.], 50 ° C., 5 kg / cm ² ( At 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 the adhesion test piece at 300 mm / min in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. 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>
A: No fogging or the like is observed on the glass plate surface.
A: Almost no fogging or the like is observed on the glass plate surface.
(Triangle | delta): Cloudiness etc. are recognized by the glass plate surface.
X: The remainder of an adhesive is recognized by the glass plate surface.

  As can be seen from Tables 1 and 2, a specific amount of a crosslinking agent is blended with a specific acrylic resin defined in the present invention to constitute a pressure-sensitive adhesive composition, which is used as a pressure-sensitive adhesive layer of a polarizing plate, and a glass cell substrate ( One polarizing plate is crossed with the one polarizing plate so that the absorption axis of one polarizing plate is 45 ° with respect to the long side of the glass substrate. In Examples 1 to 3 adhered so as to be Nicol, results excellent in whitening prevention, durability and reworkability were obtained. In particular, Example 2 having 40% of a structural unit derived from an aromatic ring-containing monomer in the acrylic resin shows excellent performance in preventing white spots.

  On the other hand, Comparative Examples 1 and 2 in which the content of the structural unit derived from the aromatic ring-containing monomer is less than 20% in the acrylic resin is insufficient in white spot prevention.

  Here, an experiment was conducted by attaching polarizing plates to the front and back of a glass substrate that does not sandwich liquid crystal, but white spots are caused by the expansion and contraction of the polarizing plate accompanying heat, so that it is not significantly affected by the presence or absence of the liquid crystal layer in the liquid crystal cell. . In addition, each test of heat resistance, moisture heat resistance and heat shock is not affected by the presence or absence of the liquid crystal layer in the liquid crystal cell because it looks at the state of the pressure-sensitive adhesive layer adhered to the glass substrate.

  The liquid crystal panel of the present invention exhibits excellent white spot prevention and durability, and is excellent in reworkability. Therefore, a liquid crystal display device to which this liquid crystal panel is applied can give good display quality and maintain the good display quality for a long period of time.

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 (whether first or second),
21 …… First polarizing plate,
21A: Absorption axis of the first polarizing plate,
22 …… Second polarizing plate,
22A: Absorption axis of the second polarizing plate,
25: Polarizing film,
26, 27 ... Transparent protective layer,
28 …… Optical compensation film (retardation film),
29 …… Interlayer adhesive,
30 ... Adhesive layer for sticking to liquid crystal cell (whether first or second),
31 …… First adhesive layer,
32: Second adhesive layer.

Claims (8)

A rectangular glass cell for liquid crystal display;
A first polarizing plate attached to one side of the glass cell via a first pressure-sensitive adhesive layer so that the absorption axis is 45 ° with respect to the long side of the glass cell;
A second polarizing plate attached to the other surface of the glass cell via a second pressure-sensitive adhesive layer so that the absorption axis is orthogonal to the absorption axis of the first polarizing plate;
At least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is:
(A) (A-1) 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)
(Meth) acrylic acid alkyl ester represented by 35 to 79.9% by weight,
(A-2) 20 to 60% by weight of an unsaturated monomer having one olefinic double bond and at least one aromatic ring in the molecule, and (A-3) an unsaturated monomer having a polar functional group 0.1 to 5% by weight
A weight average molecular weight Mw in the range of 1,000,000 to 2,000,000, and a molecular weight distribution represented by a ratio Mw / Mn between the weight average molecular weight Mw and the number average molecular weight Mn is It is formed from a pressure-sensitive adhesive composition containing 100 parts by weight of an acrylic resin in the range of 3 to 7 and (B) 0.01 to 5 parts by weight of a crosslinking agent, and has a gel fraction of 50 to 99% by weight. A liquid crystal panel characterized by that.   Both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer comprise a pressure-sensitive adhesive composition containing 100 parts by weight of the acrylic resin (A) and 0.01 to 5 parts by weight of the crosslinking agent (B). The liquid crystal panel according to claim 1, which is formed and has a gel fraction of 50 to 99% by weight. The unsaturated monomer (A-2) has the following formula (II)
(Wherein 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)
The liquid crystal panel of Claim 1 or 2 which is an aromatic ring containing (meth) acryl compound shown by these.   The liquid crystal panel according to claim 1, wherein the unsaturated monomer (A-3) 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 panel according to claim 1, wherein the crosslinking agent (B) contains an isocyanate compound.   The said adhesive composition is a liquid crystal panel in any one of Claims 1-5 containing 0.03-1 weight part of (C) silane type compounds further.   The liquid crystal panel according to claim 1, wherein at least one of the first polarizing plate and the second polarizing plate has a configuration of protective film / polarizing film / protective film.   Of the two protective films sandwiching the polarizing film, the film located on the side far from the liquid crystal display glass cell is made of cellulose acetate resin, and the film located on the liquid crystal display glass cell side has optical anisotropy. The liquid crystal panel according to claim 7, wherein the liquid crystal panel is an optical compensation film formed by coating a substance that develops.