JP2014071202A - Polarizing plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate which, when being incorporated in a liquid crystal display device, achieves high contrast and is free from tilt axis and light leakage and is less changed in color, though being a thin film.SOLUTION: A polarizer is held between two protection films, and at least one protection film is a biaxial film which has, as a main component, cellulose acylate having a total acyl substitution degree of 1.5 to 2.5 and has a film thickness of 45 μm or less, and a value (ΔRe) obtained by subtracting a value of Re (Retardation) at a wavelength of 450 nm from a value of Re at a wavelength of 630 nm satisfies an expression of -2.0≤ΔRe≤10.0. The polarizer and the biaxial films are bonded to each other with an active energy curable adhesive. When the polarizing plate having a length of 2 m is prepared, and from this polarizing plate, small sampling pieces are taken out from positions at every 50 cm interval in the longitudinal direction, and at every 20 cm interval in the width direction from the center line with respect to the width direction, and axis tilting values defined by formula (A): (an axis tilting value)=|(an angle formed between a retardation film slow axis and a polarizer absorption axis)-90°| are measured, the maximum value of the axis tilting values is 0.4° or less.

Description

  The present invention relates to a polarizing plate and a liquid crystal display device. In particular, the present invention relates to a polarizing plate suitable for a VA mode liquid crystal display device and having a retardation film as a polarizing plate protective film.

  In recent years, TV applications of liquid crystal display devices have progressed, and there has been an increasing demand for higher image quality and lower price as the screen size increases. In particular, a VA mode liquid crystal display device is the most common liquid crystal display device for TV because it has a relatively high contrast and a relatively high manufacturing yield. In liquid crystal display devices, there is an increasing demand for thinner panels. As a means for achieving a thin panel, it is conceivable to make the polarizing plate thin. For example, Patent Documents 1 and 2 disclose thinning a retardation film that also serves as a polarizing plate protective film.

International Publication WO2010 / 125835 Pamphlet JP 2011-186482 A

However, when the panel is thinned, there is a problem of corner light leakage of the panel due to contraction of the polarizing plate. Shrinkage of the polarizing plate can be suppressed by reducing the thickness of the retardation film. However, when the film is thinned, it becomes difficult to stabilize handling during processing of the polarizing plate, and axial misalignment tends to occur. For example, in the VA mode liquid crystal display device, the axis shift here means that the angle formed by the absorption axis of the polarizer and the slow axis of the retardation film is shifted from 90 °.
The polarizing plate is also required to have excellent contrast and color when incorporated in a liquid crystal display device.
On the other hand, in Patent Document 1, a cellulose ester having a high birefringence and a low total degree of acyl group substitution is used to make the retardation film thin, but the surface of the low-substitution cellulose ester deteriorates during saponification. Therefore, a method for changing the conditions for alkali saponification of the cellulose ester film used on both sides of the polarizer is disclosed. However, changing the saponification conditions for each film leads to an increase in size and complexity of the apparatus. Moreover, in patent document 2, it is disclosed that it can be bonded to a cell with favorable axial accuracy by using a firm film as a protective film of a polarizing plate. Patent Document 2 describes that triacetyl cellulose is particularly preferable, but an optical enhancer is required for a biaxial film using triacetyl cellulose having low expression. When an optical expression agent is mix | blended as described in the cited reference 2, a color change will become large. Further, the relationship between the absorption axis of the polarizer and the slow axis orientation of the retardation film is not mentioned.
The present invention has been made in view of the above prior art, and is intended to solve the above-described problems, and is a polarizing plate excellent in contrast and color when incorporated in a liquid crystal display device. An object of the present invention is to provide a polarizing plate that hardly causes axial misalignment.

  Under the above problems, the present inventors have found that a thin cellulose acylate film having a low total acyl substitution degree and a polarizer are bonded with an active energy curable adhesive. By adopting such means, it is possible to provide a polarizing plate that achieves a high contrast even in a thin film when it is incorporated in a liquid crystal display device, has no axial deviation or light leakage, and has little color change. As a result, the present invention has been completed.

Specifically, the above problem has been solved by the following means <1>, preferably by <2> to <8>.
<1> A polarizing plate having a polarizer sandwiched between two protective films,
At least one protective film is a biaxial film having a film thickness of 45 μm or less mainly composed of cellulose acylate having a total acyl substitution degree of 1.5 to 2.5,
A value (unit: nm) (ΔRe) obtained by subtracting the in-plane retardation value at a wavelength of 450 nm from the retardation value in the in-plane direction at a wavelength of 630 nm is −2.0 ≦ ΔRe ≦ 10.0,
The polarizer and the biaxial film are bonded with an active energy curable adhesive.
Take out the polarizing plate 2m, take out small pieces at intervals of 50cm in the longitudinal direction at intervals of 20cm from the center in the width direction of the polarizing plate, measure the axial deviation value shown by the following formula (A), the maximum value of the axial deviation value is A polarizing plate characterized by being 0.4 ° or less.
Formula (A)
(Axis misalignment value) = | (angle formed by retardation film retardation axis and polarizer absorption axis) −90 ° |
<2> The polarizing plate according to <1>, wherein the cellulose acylate is cellulose acetate.
<3> The polarizing plate according to <1> or <2>, wherein the biaxial film contains an ester oligomer represented by the following general formula (1).
General formula (1) B- (GA) _n -GB
(Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
<4> The polarizer and the biaxial film are bonded to each other with an adhesive layer having a thickness of 0.01 to 5 μm including an active energy curable adhesive, and any one of <1> to <3>. Polarizing plate.
<5> The polarizing plate according to any one of <1> to <4>, wherein the biaxial film is a single layer film.
<6> The polarized light according to any one of <1> to <5>, wherein the thickness of the protective film that is not the biaxial film is 10 to 40 μm, and the thickness of the polarizer is 3 to 20 μm. Board.
<7> A liquid crystal display device having the polarizing plate according to any one of <1> to <6>.
<8> A liquid crystal display device, wherein the biaxial film side of the polarizing plate according to any one of <1> to <6> is bonded to a VA liquid crystal cell via an adhesive.
<9> The polarized light according to any one of <1> to <6>, wherein the thickness of the protective film that is not the biaxial film is 10 to 40 μm, and the thickness of the polarizer is 3 to 20 μm. Board.

  According to the present invention, when incorporated in a liquid crystal display device, a polarizing plate that achieves high contrast even in a thin film, has no axial misalignment or light leakage, and has little color change is provided.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In this specification, “front side” means the display surface side, and “rear side” means the backlight side. In this specification, “front” means a normal direction relative to the display surface, and “front contrast” means a contrast calculated from white luminance and black luminance measured in the normal direction of the display surface. Shall.

  In this specification, “polarizing plate” is cut into a size to be incorporated into a long polarizing plate and a liquid crystal device unless otherwise specified (in this specification, “cutting” includes “punching” and “cutting out”. It is used in the meaning including both of the polarizing plates.

Polarizing plate The polarizing plate of the present invention is a polarizing plate in which a polarizer is sandwiched between two protective films, and at least one protective film has a total acyl substitution degree of 1.5 to 2.5. A value obtained by subtracting the in-plane retardation value at a wavelength of 450 nm from the retardation value in the in-plane direction at a wavelength of 630 nm (unit: nm) (ΔRe ) Is −2.0 ≦ ΔRe ≦ 10.0, the polarizer and the biaxial film are bonded with an active energy curable adhesive,
Take out the polarizing plate 2m, take out small pieces at intervals of 50cm in the longitudinal direction at intervals of 20cm from the center in the width direction of the polarizing plate, measure the axial deviation value shown by the following formula (A), the maximum value of the axial deviation value is It is 0.4 degrees or less.
By adopting such a polarizing plate, it is possible to provide a polarizing plate that achieves high contrast even in a thin film when incorporated in a liquid crystal display device, has no axial displacement or light leakage, and has little color change.
Hereinafter, the polarizing plate of the present invention will be described in detail.

<Biaxial film>
The biaxial film provided on one side of the polarizer of the present invention is a biaxial film having a film thickness of 45 μm or less mainly composed of cellulose acylate having a total acyl substitution degree of 1.5 to 2.5. The value (unit: nm) (ΔRe) obtained by subtracting the in-plane retardation value at a wavelength of 450 nm from the retardation value in the in-plane direction at a wavelength of 630 nm is −2.0 ≦ ΔRe ≦ 10.0. Features.
Hereinafter, such a film will be described.

(Biaxial film)
The biaxial film in the present invention is a film having two optical axes. The biaxial film used in the present invention is a cellulose acylate film containing cellulose acylate as a main component. The cellulose acylate film includes cellulose acylate having an acyl group substitution degree of 1.5 to 2.5, and has a film thickness of 45 μm or less. In the present invention, by using cellulose acylate having a low degree of acyl substitution, desired optical properties have been successfully achieved with a thin film thickness of 45 μm or less.
Here, the main component refers to the cellulose acylate when the cellulose acylate used as the material of the film is one kind, and the cellulose acylate contained in the highest proportion when there are plural kinds. Say.
Hereinafter, the present invention will be specifically described with reference to preferred embodiments of the cellulose acylate film.

-Cellulose acylate-
Examples of the acylate raw material cellulose include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any raw material cellulose can be used, and in some cases, it may be mixed and used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Society of Invention and Innovation Technical Bulletin No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used.

  Only one kind of acyl group may be used for acylating the cellulose acylate of the biaxial film, or two or more kinds of acyl groups may be used. The biaxial film preferably has an acyl group having 2 to 4 carbon atoms as a substituent, and particularly preferably has an acyl group having 2 carbon atoms as a substituent from the viewpoint of cost. When two or more types of acyl groups are used, 50% by mass or more of the cellulose acylate used is preferably an acetyl group, and the acyl group having 2 to 4 carbon atoms is preferably a propionyl group or a butyryl group. With these films, a solution having a preferable solubility can be prepared, and in particular, in a non-chlorine organic solvent, a good solution can be prepared. Further, a solution having a low viscosity and good filterability can be produced.

  First, the cellulose acylate preferably used for the cellulose acylate film in the present invention will be described in detail. Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by acylating part or all of these hydroxyl groups with an acyl group. The degree of acyl substitution means the sum of the ratios of acylation of the hydroxyl groups of cellulose located at the 2-position, 3-position and 6-position (100% acylation at each position is substitution degree 1).

  In the present invention, in the biaxial film, the total acyl substitution degree of the cellulose acylate is 1.5 to 2.5, preferably 1.6 to 2.6, and preferably 2.0 to 2. 5 is more preferable. The cellulose acylate having a low degree of substitution is excellent in optical properties for a low price.

  The acyl group having 2 or more carbon atoms of cellulose acylate in the present invention may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these are acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group. Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group (when the cellulose acylate is cellulose acetate).

  In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

  The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their anhydrides. This is a method of acylating with a mixed organic acid component.

  The cellulose acylate used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804.

  The biaxial film may contain additives such as ester oligomers and sugar esters. Hereinafter, the additive will be described.

(Ester oligomer)
The cellulose acylate film preferably contains an ester oligomer, and more preferably contains an ester oligomer represented by the following general formula (1).

General formula (1): B- (GA) _n -GB
(In the formula, B is a hydroxyl group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In general formula (1), a hydroxyl group or a carboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, an alkylene dicarboxylic acid residue represented by A or It is composed of an aryl dicarboxylic acid residue, and can be obtained by the same reaction as a normal ester oligomer.

  Examples of the carboxylic acid component of the ester oligomer represented by the general formula (1) include acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, There are ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the ester oligomer represented by the general formula (1) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanedio 2, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the ester oligomer represented by the general formula (1) include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the ester oligomer represented by the general formula (1) include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. There exist acids etc., and these are used as 1 type, or 2 or more types of mixtures, respectively. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The ester oligomer represented by the general formula (1) has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl group (hydroxyl group) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl group (hydroxyl group) value is 15 mgKOH / g or less. Is.

  Although the specific compound of the ester oligomer represented by General formula (1) which can be used for this invention below is shown, this invention is not limited to this.

  It is preferable that 0.1-30 mass% of the said ester oligomer is included in the said cellulose acylate film of the said cellulose-ester film, It is preferable that 0.5-10 mass% is included especially.

(Sugar ester)
A sugar ester can be preferably used for the cellulose acylate film.
As the sugar ester compound, an ester compound in which 1 to 12 of at least one of a pyranose structure or a furanose structure and a part of the OH group in the structure are esterified and a mixture thereof can be preferably used.

  The ratio of esterification of an ester compound obtained by esterifying at least one of at least one pyranose structure or furanose structure and all or part of the OH groups of the structure is the OH group present in the pyranose structure or furanose structure. It is preferable that it is 70% or more.

  Examples of the ester compound used in the present invention include the following, but the present invention is not limited to these.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocate Acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p-coumaric Examples of the acid include benzoic acid and naphthylic acid.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or the furanose structure.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 type of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ , and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group further have a substituent. May be. Oligosaccharides can also be produced in the same manner as the sugar ester compound.

  Specific examples of the sugar ester compound are given below, but the present invention is not limited thereto.

  The cellulose acylate film preferably contains the sugar ester compound in an amount of 0.5 to 30% by mass of the cellulose ester film, and particularly preferably 2 to 15% by mass.

(Other additives)
In the cellulose acylate film, as an additive other than the ester oligomer and the sugar ester, a polycondensation polymer, a retardation adjusting agent (a retardation developing agent and a retardation reducing agent); a phthalate ester, a phosphate ester, etc. Additives such as a plasticizer; an ultraviolet absorber; an antioxidant; a matting agent may be added.

(Retardation expression agent)
The cellulose acylate film may contain a retardation enhancer in order to develop a retardation value. Although there is no restriction | limiting in particular as said retardation expression agent, What consists of a compound characterized by the structure represented by rod-shaped or a disk-shaped compound, or the general formula (II-1) mentioned later can be mentioned. As the rod-like or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developer.
The addition amount of the retardation developer composed of the rod-shaped compound is preferably 0.1 parts by mass or more and less than 3 parts by mass, and 0.5 parts by mass or more and less than 2 parts by mass with respect to 100 parts by mass of the cellulose acylate component. More preferably it is. The rod-shaped compound is a compound having a linear molecular structure, and means that the molecular structure of the rod-shaped compound is linear in the thermodynamically most stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation can be performed using molecular orbital calculation software (eg, WinMOPAC2000, manufactured by Fujitsu Limited) to determine the molecular structure that minimizes the heat of formation of the compound. The molecular structure being linear means that the angle of the molecular structure is 140 degrees or more in the thermodynamically most stable structure obtained by calculation as described above.
On the other hand, the discotic compound is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and 1 to 4% by mass with respect to the cellulose acylate. Is particularly preferred. A preferable addition amount of the compound having a characteristic in the structure represented by the general formula (II-1) described later to the cellulose acylate is the same as the preferable addition range of the discotic compound.
Since a discotic compound and a compound having a structure represented by the general formula (II-1) described below are superior to a rod-like compound in terms of Rth retardation expression, particularly when a large Rth retardation is required. Is preferably used. Two or more retardation developers may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

The discotic compound will be described. The discotic compound gives a sphere defined by the van der Waals radius to the discotic nucleus of the molecule of the compound, and the shape is defined with the three edges of the first rectangular parallelepiped that the molecule can enter as a, b, and c. When the shape of the mother nucleus is preferably a ≧ b> c and b ≧ 0.5a. As the discotic compound, a compound having at least two aromatic rings can be used.
In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring.
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, a benzene ring, a condensed benzene ring, and biphenyls are preferable. In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, compounds disclosed in JP-A No. 2001-166144 are preferably used.

The number of carbon atoms of the aromatic ring in the retardation enhancer is preferably 2-20, more preferably 2-12, still more preferably 2-8, and 2-6. Most preferred.
The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent.
Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group, and a non-aromatic heterocyclic group.

It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (for example, a hydroxy group, a carboxy group, an alkoxy group, an alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl, and 2- Each group of a diethylaminoethyl group is included.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.
The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include an acetoxy group.
The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (for example, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.
The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.
The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide.
The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamido group include a methanesulfonamido group, a butanesulfonamido group, and an n-octanesulfonamido group.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.
The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.
The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include a methylureido group.
Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.
The molecular weight of the retardation developer is preferably 300 to 800.

  In the present invention, it is preferable to use a triazine compound represented by the following general formula (I) as the discotic compound.

In the above general formula (I):
R ²⁰¹ each independently represents an aromatic ring or a heterocyclic ring having a substituent in at least one of the ortho, meta and para positions. X ²⁰¹ each independently represents a single bond or —NR ²⁰² —. Here, each R ²⁰² independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aryl group, or a heterocyclic group.

The aromatic ring represented by R ²⁰¹ is preferably phenyl or naphthyl, particularly preferably phenyl. The aromatic ring R ²⁰¹ represents may have at least one substituent at any substitutable position. Examples of the substituent include halogen atom, hydroxyl group, cyano group, nitro group, carboxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, Alkenyloxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamide group, carbamoyl, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide Groups, alkylthio groups, alkenylthio groups, arylthio groups and acyl groups.

The heterocyclic group represented by ^R201 preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent of the aryl moiety.
When X ²⁰¹ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms. Further, the heterocyclic group may have a hetero atom other than the nitrogen atom (for example, O, S). Examples of heterocyclic groups having free valences on nitrogen atoms are shown below. Here, -C ₄ H ₉ ⁿ represents a n-C ₄ H _9.

The alkyl group represented by R ²⁰² may be a cyclic alkyl group or a chain alkyl group, but a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. preferable. The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, further preferably 1-10, still more preferably 1-8, and 1-6. Most preferred. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (for example, methoxy group, ethoxy group) and an acyloxy group (for example, acryloyloxy group, methacryloyloxy group).

The alkenyl group represented by R ²⁰² may be a cyclic alkenyl group or a chain alkenyl group, but is preferably a chain alkenyl group and is more preferably a linear alkenyl group than a branched chain alkenyl group. More preferably it represents a group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent. Examples of the substituent are the same as those of the alkyl group described above.
The aromatic ring group and heterocyclic group represented by R ²⁰² are the same as the aromatic ring and heterocyclic ring represented by R ²⁰¹ , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent are the same as those of the aromatic ring and heterocyclic ring of ^R201 .

  The compound represented by the general formula (I) can be synthesized by a known method such as the method described in JP-A-2003-344655. Details of the retardation enhancer are described on page 49 of published technical bulletin 2001-1745.

  As the retardation developer, a polymer additive can be used as in the case of the low molecular compound. Here, the polymer used as the polycondensed ester in the present invention may also serve as a retardation developer. As the polymer-type retardation developing agent that is also the polycondensed ester, the aromatic polyester polymer and a copolymer of the aromatic polyester polymer and other resins are preferable.

(Retardation reducing agent)
In the present invention, compounds other than phosphoric acid ester compounds and known non-phosphoric acid ester compounds as additives for cellulose acylate films can be widely employed as retardation reducing agents.

  The polymer retardation reducing agent is selected from phosphoric acid-based polyester polymers, styrene polymers, acrylic polymers, and copolymers thereof, and acrylic polymers and styrene polymers are preferred. Moreover, it is preferable that at least one polymer having negative intrinsic birefringence, such as a styrene polymer and an acrylic polymer, is included.

  Examples of the low molecular weight retardation reducing agent which is a compound other than the non-phosphate ester compound include the following. These may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of an ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and a mixture of deterioration preventing agents are also possible. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the cellulose acylate solution (dope) preparation step, but it may be added by adding a preparation step to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  The low molecular weight retardation reducing agent which is a compound other than the non-phosphate ester compound is not particularly limited, but details are described in JP-A-2007-272177, [0066] to [0085].

The compound described as the general formula (1) in [0066] to [0085] of JP-A-2007-272177 can be prepared by the following method.
The compound of the general formula (1) of the publication can be obtained by a condensation reaction between a sulfonyl chloride derivative and an amine derivative.

  JP, 2007-272177, A The compound of general formula (2) is a dehydration condensation reaction of carboxylic acids and amines using a condensing agent (for example, dicyclohexylcarbodiimide (DCC) etc.), or a carboxylic acid chloride derivative, It can be obtained by a substitution reaction with an amine derivative.

  The retardation reducing agent is more preferably an Rth reducing agent from the viewpoint of realizing a suitable Nz factor. Among the retardation reducing agents, examples of the Rth reducing agent include acrylic polymers and styrene polymers, and low molecular compounds represented by general formulas (3) to (7) in JP-A-2007-272177, and the like. Of these, acrylic polymers and styrene polymers are preferred, and acrylic polymers are more preferred.

The retardation reducing agent is preferably added at a rate of 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, more preferably 0.1 to 10%, based on the cellulose resin. It is particularly preferable to add at a ratio of mass%.
By making the said addition amount 30 mass% or less, compatibility with a cellulose resin can be improved and whitening can be suppressed. When using two or more types of retardation reducing agents, the total amount is preferably within the above range.

(Plasticizer)
The cellulose acylate film may contain a plasticizer. As the plasticizer, many compounds known as cellulose acylate plasticizers can also be usefully used. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
Further, polycondensation of dicarboxylic acid such as terephthalic acid and phthalic acid and diol such as ethylene glycol and propylene glycol may be used.

(Deterioration inhibitor)
The cellulose acylate film is a known deterioration (oxidation) inhibitor such as 2,6-di-tert-butyl-4-methylphenol, 4,4′-thiobis- (6-tert-butyl-3-methyl). Phenol), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythrityl- A phenolic or hydroquinone antioxidant such as tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] can be added. Furthermore, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert) It is preferable to use a phosphorus-based antioxidant such as -butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The addition amount of the deterioration inhibitor is 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the cellulose resin.

(UV absorber)
The said cellulose acylate film may contain the ultraviolet absorber from a viewpoint of deterioration prevention, such as a polarizing plate or a liquid crystal. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include, for example, hindered phenol compounds, hydroxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds Etc. Examples of hindered phenol compounds include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like. Examples of benzotriazole compounds include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6 (2H-benzotriazol-2-yl) phenol), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5- Triazine, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4- Hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5 -Chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and the like. The addition amount of these ultraviolet light inhibitors is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm by mass in the entire optical film.

(Matting agent)
The cellulose acylate film may contain a matting agent from the viewpoint of film slipperiness and stable production. The matting agent may be an inorganic compound matting agent or an organic compound matting agent.
Specific examples of the inorganic compound matting agent include silicon-containing inorganic compounds (for example, silicon dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, etc.), titanium oxide, and zinc oxide. , Aluminum oxide, barium oxide, zirconium oxide, strongtium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin, calcium phosphate, etc., more preferably silicon-containing inorganic compounds and oxides Although it is zirconium, since the turbidity of a cellulose acylate film can be reduced, silicon dioxide is particularly preferably used. As the silicon dioxide fine particles, for example, commercially available products having trade names such as Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used. As the zirconium oxide fine particles, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.
Preferable specific examples of the organic compound matting agent include, for example, polymers such as silicone resin, fluorine resin and acrylic resin, and among them, silicone resin is preferably used. Of the silicone resins, those having a three-dimensional network structure are particularly preferable. A commercial product having a trade name can be used.

  When these matting agents are added to the cellulose acylate solution, the method is not particularly limited, and there is no problem as long as a desired cellulose acylate solution can be obtained by any method. For example, an additive may be contained at the stage of mixing cellulose acylate and a solvent, or an additive may be added after preparing a mixed solution with cellulose acylate and a solvent. Further, it may be added and mixed immediately before casting the dope, which is a so-called immediately preceding addition method, and the mixing is used by installing screw-type kneading online. Specifically, a static mixer such as an in-line mixer is preferable, and as the in-line mixer, for example, a static mixer SWJ (Toray static type in-pipe mixer HI-Mixer) (manufactured by Toray Engineering) is used. Is preferred. In addition, regarding in-line addition, in order to eliminate density unevenness, particle aggregation, and the like, Japanese Patent Application Laid-Open No. 2003-053752 mixes additive liquids having different compositions into the main raw material dope in a method for producing a cellulose acylate film. An invention is described in which the distance L between the tip of the addition nozzle and the start end of the in-line mixer is 5 times or less the inner diameter d of the main raw material pipe, thereby eliminating concentration unevenness and aggregation of matte particles. As a more preferred embodiment, the distance (L) between the tip opening of the additive liquid supply nozzle having a composition different from that of the main raw material dope and the starting end of the in-line mixer is 10 times or less the inner diameter (d) of the supply nozzle tip opening. And that the in-line mixer is a static unstirred in-tube mixer or a dynamic agitated in-tube mixer. More specifically, it is disclosed that the flow rate ratio of the cellulose acylate film main raw material dope / in-line additive solution is 10/1 to 500/1, preferably 50/1 to 200/1. Furthermore, the additive is also added to Japanese Patent Application Laid-Open No. 2003-014933 of the invention aiming at a retardation film with little additive bleed-out, no delamination phenomenon, excellent slipperiness and excellent transparency. As a method to do this, it may be added to the melting pot, or a solution in which additives or additives are dissolved or dispersed between the melting pot and the co-casting die may be added to the dope being fed. However, in the latter case, it is described that it is preferable to provide a mixing means such as a static mixer in order to improve the mixing property.

(Production method of biaxial film (cellulose acylate film))
The method for producing a cellulose acylate film includes a step of heating a cellulose acylate film containing an acylate having an acyl group substitution degree of 1.5 to 2.5 at a temperature of Tg−20 ° C. or more (provided that Tg is cellulose acylate). Including the glass transition temperature (unit: ° C.) of the rate film.
Although there is no restriction | limiting in particular as a manufacturing method of the cellulose acylate film containing the acylate whose acyl group substitution degree is 1.5-2.5, It is preferable to manufacture with the solvent cast method (solution casting film forming method). .
Hereinafter, the production method of the present invention will be described in detail.

  The cellulose acylate film can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  In the solution casting method, the cellulose acylate film is produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope on an endless metal support that moves indefinitely, It is performed by a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope is preferably a mixture of a good solvent and a poor solvent of cellulose ester and used in combination of two or more solvents in terms of production efficiency, and the more good solvent is in terms of the solubility of the cellulose ester. preferable.

 The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for dope (henceforth a cellulose ester solution) when carrying out solution casting of the said acylate film used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, Cyclohexanone or the like is preferably used.

As the poor solvent used in the cellulose ester solution, an alcohol having an average carbon number of 4 or less is preferably used from the viewpoint of solubility, and an alcohol having an average carbon number of 2 to 4 is preferably used from the viewpoint of the peeling load.
The preferable range of the mixing ratio of the good solvent and the poor solvent used in the cellulose ester solution is preferably 30% by mass or less from the viewpoint of solubility of the cellulose ester, and alcohol as the poor solvent from the viewpoint of reducing the peeling load. It is preferable to contain 15 mass% or more. It is more preferable that the dope solvent for forming the acylate film into a solution contains 15 to 30% by mass of alcohol.

Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.
The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos.

  A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Especially preferably, it is 0-0.01 mass% or less.

  In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the cellulose ester film, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  In order to impart the following desired retardations Re and Rth to the cellulose ester film, the cellulose ester film takes the configuration according to the present invention, and further controls the refractive index anisotropy by controlling the transport tension and stretching operation. It is preferable.

  For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

  Moreover, it is preferable to carry out biaxial stretching or uniaxial stretching sequentially or simultaneously with respect to the longitudinal direction (conveying direction) of the film and the direction orthogonal thereto in the film plane.

  The stretching ratios in the biaxial directions orthogonal to each other in the stretching step are preferably in the range of −20% to 50% in the transport direction and 0% to 150% in the direction orthogonal to the transport direction, and −10 in the transport direction. It is preferable to carry out within a range of 0% to 10% and 0% to 50% in the direction orthogonal to the transport direction.

  The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 150 ° C. to 200 ° C., and more preferably 150 ° C. to 190 ° C. or less.

  The residual solvent in the film at the start of stretching is preferably 30 to 0%, more preferably 15 to 0%.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or fast axis of the cellulose ester film is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1, More preferably, the angle is not less than ° and not more than + 0.5 °, and further preferably not less than −0.1 ° and not more than + 0.1 °.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

[Heating steam treatment]
In addition, the stretched film may be manufactured through a process of spraying steam heated to 100 ° C. or higher. By passing through this water vapor spraying step, the residual stress of the cellulose acylate film to be produced is relaxed, and the dimensional change is reduced, which is preferable. The temperature of the water vapor is not particularly limited as long as it is 100 ° C. or higher, but considering the heat resistance of the film, the temperature of the water vapor is 200 ° C. or lower.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. The winder used for producing the cellulose acylate film may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

  The length of the cellulose acylate film obtained as described above is preferably wound at 100 to 10000 m per roll, more preferably 500 to 7000 m, and further preferably 1000 to 6000 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

  In general, in a large-screen display device, since the decrease in contrast and coloration in an oblique direction become remarkable, the polarizing plate of the present invention produced using the cellulose acylate film is particularly large-screen liquid crystal display device. Suitable for use in. When used for a large-screen liquid crystal display device, for example, the cellulose acylate film width is preferably set to 1470 mm or more. In addition, the cellulose acylate film is produced not only in the form of a film piece cut into a size that can be incorporated into a liquid crystal display device as it is, but also in a long shape by continuous production and in a roll shape. A film in a rolled up form is also included. The cellulose acylate film of the latter mode is stored and transported in that state, and is cut into a desired size and used when it is actually incorporated into a liquid crystal display device or bonded to a polarizer or the like. Similarly, it is cut into a desired size when it is actually incorporated into a liquid crystal display device after being bonded to a polarizer or the like made of a polyvinyl alcohol film or the like that has been made into a long shape. Used. As an aspect of the cellulose acylate film wound up in a roll shape, an aspect in which the roll length is rolled up into a roll having a length of 2500 m or more can be mentioned.

<Characteristics of biaxial film>
(Biaxial film layer structure)
The biaxial film may be a single layer film or may have a laminated structure of two or more layers, but is preferably a single layer film.

(Film thickness)
The biaxial film has a film thickness of 45 μm or less. By using such a thin biaxial film, a thin polarizing plate and a thin liquid crystal display device can be obtained. The film thickness of the biaxial film is preferably 15 μm or more. When the thickness is 45 μm or less, the warpage of the panel can be suppressed, and when the thickness is 15 μm or more, sufficient optical characteristics can be easily obtained by compensating the VA liquid crystal. When the biaxial film is a laminated film, the range of the total film thickness of the film is the preferred range.
The film thickness in the present invention refers to the average film thickness.

(Film width)
The biaxial film preferably has a film width of 1000 mm or more, more preferably 1500 mm or more, and particularly preferably 1800 mm or more.

(Re, Rth)
In the biaxial film, a value (unit: nm) (ΔRe) obtained by subtracting the in-plane retardation value at a wavelength of 450 nm from the in-plane direction retardation value at a wavelength of 630 nm is −2.0 ≦ ΔRe ≦ 10. 0, preferably 0 ≦ ΔRe ≦ 9.0, more preferably 1 ≦ ΔRe ≦ 9.0, and even more preferably 2 ≦ ΔRe ≦ 9.0.

The biaxial film preferably has an in-plane retardation at a wavelength of 550 nm and a film thickness direction satisfying the following formula.
30 nm ≦ Re (550) ≦ 200 nm
70 nm ≦ Rth (450) ≦ 300 nm
Re (550) is more preferably 45 to 100 nm. Rth (550) is more preferably 110 to 230 nm.

  Note that the film is biaxial means nx, ny and nz of the optical compensation film (nx represents the refractive index in the slow axis direction in the plane, and ny represents the refractive index in the direction perpendicular to nx in the plane. And nz represents the refractive index in the direction orthogonal to nx and ny), and in the present invention, it is more preferable that nx> ny> nz.

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. In the present specification, the wavelength λ is 550 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane) Is measured in 6 points from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the normal direction of the film. KOBRA 21ADH calculates based on the retardation value, the assumed average refractive index, and the input film thickness value. The retardation value is measured from any two directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), and the value Rth can also be calculated from the following formula (A) and formula (B) based on the assumed average refractive index and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

Here, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction, nx, ny, and nz represent refractive indexes in respective principal axis directions of the refractive index ellipsoid, and d represents a film. Represents thickness.
Rth = ((nx + ny) / 2−nz) × d Formula (B)
At this time, an average refractive index n is required as a parameter, and a value measured by an Abbe refractometer (“Abbe refractometer 2-T” manufactured by Atago Co., Ltd.) was used.

In this specification, the values of Re (λ) and Rth (λ) such as Re (450), Re (550), Re (630), Rth (450), Rth (550), and Rth (630) are , Measurement is performed using three or more different wavelengths (for example, λ = 479.2, 546.3, 628.3, 745.3 nm) by a measuring apparatus, and Re and Rth are calculated from the respective wavelengths. These values are approximated by Cauchy's equation (up to the third term, Re = A + B / λ ² + C / λ ⁴ ) to obtain values A, B, and C. From the above, Re and Rth at the wavelength λ can be re-plotted, and Re (λ) and Rth (λ) at each wavelength λ can be obtained therefrom.

(Internal haze)
The biaxial film of the present invention preferably has an internal haze of less than 0.08%.
The haze represents a haze value (%) measured according to JIS K7136.
The internal haze of the biaxial film is obtained by dropping a few drops of glycerin on both sides of the obtained biaxial film and sandwiching it from both sides with two 1.3 mm thick glass plates (MICRO SLIDE GLASS product number S9213, manufactured by MATSUNAMI). The value (%) obtained by subtracting the haze measured in a state where several drops of glycerin were dropped between two sheets of glass from the haze value (%) measured in an open state.
The haze of the biaxial film of the present invention was measured using a turbidimeter (NDH2000, Nippon Denshoku Industries Co., Ltd.) in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and a relative humidity of 55%. It was measured.

The internal haze of the biaxial film of the present invention is preferably 0.05% or less, and more preferably 0.03% or less.
A lower haze is generally preferred. Further, simply reducing the total haze is insufficient for improving the front contrast, and adjusting the inner haze to the above range is preferable from the viewpoint of improving the front contrast of the liquid crystal display device.

(Dimensional change rate)
As for a biaxial film, it is more preferable that the rate of dimensional change before and after the passage of 24 hours at 60 ° C. and 90% relative humidity satisfies the following formula (7) in the film transport direction and the direction perpendicular thereto.
−0.5% ≦ {(L′−L0) / L0} × 100 ≦ 0.5% (7)
The L0 represents the film length after conditioning for 2 hours or more in an atmosphere of 25 ° C. and a relative humidity of 60%, and L ′ is 24 hours at 60 ° C. and 90% relative humidity, and further conditioned for 2 hours. Represents film length.
When the dimensional change rate is within the range of the formula (7), the saponification treatment hardly causes dimensional change of the film, so that wrinkles and air can be prevented from being mixed in the polarizing plate bonding process. The dimensional change rate is more preferably −0.4 to 0.4%, and particularly preferably −0.2 to 0.2%.

(Average elastic modulus in the longitudinal and transverse directions)
In the present invention, the average value of the elastic modulus in the longitudinal direction (TD direction) and the elastic modulus in the transverse direction (MD direction) (hereinafter also referred to as the average elastic modulus) of the biaxial film is 3500 to 10,000 MPa. Preferably, it is 4000-8000 MPa.
The film of the present invention effectively suppresses unevenness and the like due to thinning by making the average elastic modulus within the above range.
The average elastic modulus can be measured using a Toyo Baldwin universal tensile tester (STM T50BP).

<Polarizing plate protective film>
Among the protective films of the polarizing plate of the present invention, a cellulose acylate film or a norbornene film can be preferably used as the protective film that is not a biaxial film. As such a protective film, for example, Fujitac TD80UF, manufactured by Fuji Film, ZF14, manufactured by Nippon Zeon, or the like can be used.
The thickness of the protective film is preferably 10 to 40 μm, and more preferably 20 to 40 μm.

<Active energy curable adhesive>
In the present invention, the polarizer and the biaxial film are bonded with an active energy curable adhesive. By bonding such a polarizer and a biaxial film using such an adhesive, the effect of not deteriorating the surface of a film mainly composed of a low-substituted cellulose ester can be obtained. In general, light is used as the active energy ray. Although the said light is not specifically limited, For example, a microwave, infrared rays, visible light, an ultraviolet-ray, X-ray | X_line, a gamma ray etc. are mentioned.

 An active energy curable adhesive adhesive layer made of an active energy curable adhesive is formed between the polarizer and the biaxial film. The thickness of the adhesive layer is preferably 0.01 to 5 μm, and more preferably 0.2 to 3 μm. When the thickness is 0.01 μm or more, good adhesion is obtained, and when the thickness is 5 μm or less, the warpage of the panel can be effectively suppressed.

An active energy curable adhesive is an adhesive that cures when irradiated with active energy rays and does not contain a solvent (solvent-free).
Here, “does not contain solvent” means that the adhesive used for applying to the adherend does not contain any solvent, or the solvent content is less than 2% by weight based on the total weight of the adhesive. Say. The solvent content in the adhesive can be measured by gas chromatography or the like.

  Solvents include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, propanol, isopropanol and n-butanol; acetone and butanone , Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate and butyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; halogenation such as methylene chloride and chloroform And hydrocarbons.

Moreover, the active energy ray-curable solvent-free adhesive used in the present invention is excellent in adhesive applicability when the viscosity measured by a B-type viscometer at 23 ° C. is 200 to 5000 mPa · s.
As the solvent-free adhesive that is cured by the active energy ray, any known one can be used without particular limitation as long as it is colorless and transparent. Examples of the active energy ray-curable compound that is the main component of the active energy ray-curable solvent-free adhesive include radical polymerization by active energy rays such as compounds having a functional group such as acryloyl group, methacryloyl group, and allyl group. Cured (photo radical polymerizable compound); cured by a photocation reaction by an active energy ray of a compound having a functional group such as epoxy group, oxetane group, hydroxyl group, vinyl ether group, episulfide group, ethyleneimine group, etc. (Photo cationic polymerizable compound);

  As photoradical polymerizable compounds, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; hydroxyaryl acrylates such as 2-hydroxy-3-phenoxypropyl acrylate; 2-acryloyloxyethyl succinic acid, 2- Acrylic modified carboxylic acids such as acryloyloxyethylphthalic acid; polyethylene glycol diacrylates such as triethylene glycol diacrylate and tetraethylene glycol diacrylate; polypropylene glycol diacrylates such as dipropylene glycol diacrylate and tripropylene glycol diacrylate Other, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-no Diol diacrylate, bisphenol A ethylene oxide modified diacrylate, bisphenol A propylene oxide modified diacrylate, dimethylol tricyclodecane diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate Such as epoxy acrylate, urethane acrylate, other acrylates such as acrylic benzoic acid mixed ester of neopentyl glycol; methacrylates thereof, and the like.

  Bisphenol type epoxy resin such as bisphenol A type epoxy resin and bisphenol F type epoxy resin; novolak type epoxy resin such as phenol novolak type epoxy resin and cresol novolak type epoxy resin; aliphatic epoxy resin, alicyclic Type epoxy resin, heterocyclic epoxy resin, polyfunctional epoxy resin, biphenyl type epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin; alcohol such as hydrogenated bisphenol A type epoxy resin Type epoxy resin; halogenated epoxy resin such as brominated epoxy resin; rubber-modified epoxy resin, urethane-modified epoxy resin, epoxidized polybutadiene, epoxidized styrene-butadiene-styrene Compounds having an epoxy group, such as a polyblock copolymer, an epoxy group-containing polyester resin, an epoxy group-containing polyurethane resin, and an epoxy group-containing acrylic resin; phenoxymethyl oxetane, 3,3-bis (methoxymethyl) oxetane, 3,3- Bis (phenoxymethyl) oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3-{[3- (triethoxysilyl) Propoxy] methyl} oxetane, di [1-ethyl (3-oxetanyl)] methyl ether, oxetanylsilsesquioxane, phenol novolac oxetane, 1,4-bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} Compounds having an oxetanyl group such as benzene It is below.

  These active energy ray-curable compounds may be used alone or in combination.

  A polymerization initiator can be mix | blended with an active energy ray hardening-type adhesive in order to raise the curing reaction efficiency of the above-mentioned active energy ray hardening-type adhesive agent. The polymerization initiator is selected according to the type of active energy ray used. As the polymerization initiator, photo radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin alkyl ethers; aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metathelone compounds, benzoin sulfones Photocationic polymerization initiators such as acid esters; and the like. These can be used individually by 1 type or in combination of 2 or more types.

  As the acetophenone photopolymerization initiator, for example, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1- [ 4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone and the like.

Examples of the benzoin alkyl ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.
Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like.

  The cationic photopolymerization initiator may be an ionic photoacid-generating photocationic polymerization initiator or a nonionic photoacid-generating photocationic polymerization initiator. The photocationic polymerization initiator is a photocationic polymerization initiator that is activated by light having a wavelength of 350 nm or more because it can effectively initiate and advance the photocationic polymerization of the photocationically polymerizable compound. Is preferred.

  The ionic photoacid-generating photocationic polymerization initiator is not particularly limited. For example, onium salts such as aromatic diazonium salts, aromatic halonium salts, and aromatic sulfonium salts; organometallic complexes such as iron-allene complexes, titanocene complexes, and arylsilanol-aluminum complexes; tetrakis (pentafluorophenyl) borate Examples thereof include a photocationic polymerization initiator having a bulky counter anion. These ionic photoacid-generating photocationic polymerization initiators may be used alone or in combination of two or more.

  Examples of commercially available ionic photoacid-generating photocationic polymerization initiators include “Adekaoptomer” series such as “Adekaoptomer SP150” and “Adekaoptomer SP170” manufactured by Asahi Denka Kogyo Co., Ltd. , A trade name “UVE-1014” manufactured by General Electronics Co., Ltd., a product name “CD-1012” manufactured by Sartomer, and a product name “Photoinitiator 2074” manufactured by Rhodia.

  The nonionic photoacid-generating photocationic polymerization initiator is not particularly limited. For example, nitrobenzyl ester, sulfonic acid derivative, phosphoric acid ester, phenolsulfonic acid ester, diazonaphthoquinone, N-hydroxyimidophosphonate and the like can be mentioned. These nonionic photoacid-generating photocationic polymerization initiators may be used alone or in combination of two or more.

  The compounding quantity of a polymerization initiator is 0.5-10 weight part normally with respect to 100 weight part of active energy ray hardening compounds.

  Furthermore, the active energy ray-curable adhesive contains a photosensitizer, an antistatic agent, an infrared absorber, an ultraviolet absorber, an antioxidant, organic particles, inorganic oxide particles, a pigment, a dye, and the like. Also good.

  By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured adhesive can be improved. The photosensitizer is not particularly limited, and examples thereof include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes.

  Specific examples of the photosensitizer include benzoin methyl ether, benzoin isopropyl ether, benzoin derivatives such as α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, Benzophenone derivatives such as 4,4′-bis (dimethylamino) benzophenone and 4,4′-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; 2-chloroanthraquinone, 2- Anthraquinone derivatives such as methyl anthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone; other, α, α-diethoxyacetophenone, benzyl, fluorenone, xanthone, urine Sulfonyl compound, such as halogen compounds, but the invention is not limited thereto. These may be used alone or in combination. The photosensitizer is preferably contained within a range of 0.1 to 20 parts by weight when the active energy ray-curable compound is 100 parts by weight.

<Polarizer>
In the present invention, a general linear polarizer can be used as the polarizer. The polarizer may be a stretched film or a layer formed by coating. Examples of the former include a film obtained by dyeing a stretched film of polyvinyl alcohol with iodine or a dichroic dye. Examples of the latter include a layer in which a composition containing a dichroic liquid crystalline dye is applied and fixed in a predetermined alignment state.
In the present specification, the term “polarizer” means a linear polarizer.
In the polarizing plate of this invention, it is preferable that the film thickness of a polarizer is 3-30 micrometers, and it is more preferable that it is 5-25 micrometers.

<Production method of polarizing plate>
The polarizing plate of the present invention is a biaxial film in which a biaxial film is bonded to one surface of a polarizer via the active energy ray-curable adhesive, and then irradiated with active energy rays to cure the adhesive. It is obtained by fixing the film to a polarizer.

  There is no particular limitation on the method of applying the adhesive to the polarizer, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

  Prior to the bonding of the biaxial film to the polarizer, the bonding surface may be subjected to an easy adhesion process such as a saponification process, a corona process, a primer process, or an anchor coating process.

  In the present invention, light is usually used as the active energy ray. Although the said light is not specifically limited, For example, a microwave, infrared rays, visible light, an ultraviolet-ray, X-ray | X_line, a gamma ray etc. are mentioned. In particular, ultraviolet rays are preferably used because of easy handling and relatively high energy.

The light source used for irradiating ultraviolet rays is not particularly limited, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, and a metal halide lamp. The irradiation intensity is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is preferably 0.1 to 100 mW / cm ² . When the light irradiation intensity is less than 0.1 mW / cm ² , the reaction time becomes too long, and when it exceeds 100 mW / cm ² , the adhesive is yellowed or polarized due to radiation heat from the lamp, polymerization reaction heat, or the like. The child itself may be deteriorated. The light irradiation time is appropriately selected according to the curing state and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ / cm ^2. It is preferable to set to.

  Like the film of the present invention, the polarizing plate of the present invention is not only a polarizing plate in the form of a film piece cut into a size that can be incorporated into a liquid crystal display device as it is, but also in a long form by continuous production. The polarizing plate of the aspect (for example, aspects with roll length 2500m or more, 3900m or more) wound up in roll shape is also contained. In order to use for a large-screen liquid crystal display device, the width of the polarizing plate is preferably 1470 mm or more as described above.

<Axis misalignment>
In this invention, as above-mentioned, the polarizer and the biaxial film are adhere | attached with the active energy curable adhesive, 2 m of polarizing plates are taken out, and it is 20 cm intervals from the center of the width direction of a polarizing plate every 50 cm of longitudinal directions. The small piece is taken out and the axial deviation value represented by the following formula (A) is measured, and the maximum value of the axial deviation value is 0.4 ° or less.
Formula (A)
(Axis misalignment value) = | (angle formed by retardation film retardation axis and polarizer absorption axis) −90 ° |
The axial deviation is preferably 0.3 ° or less.

<Liquid crystal display device>
The liquid crystal display device of the present invention includes at least one polarizing plate of the present invention. Since the liquid crystal display device of the present invention includes the polarizing plate of the present invention including the cellulose acylate film of the present invention, the contrast in the front direction and the color change in the viewing angle direction are remarkably improved.
In the liquid crystal display device of the present invention, the glass constituting the liquid crystal cell preferably has a thickness of 50 to 500 μm. By using such glass, the thickness of the liquid crystal display device can be reduced.
The liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein at least one of the polarizing plates is the polarizing plate of the present invention. An IPS, OCB or VA mode liquid crystal display device is preferable.
There is no restriction | limiting in particular as a concrete structure of the liquid crystal display device of this invention, A well-known structure is employable. For example, the configuration shown in FIG. 2 of Japanese Patent Application Laid-Open No. 2008-262161 can also be preferably employed.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

[Example 1]
<Preparation of cellulose ester film 1>
<Fine particle dispersion>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass 89 parts by mass of ethanol The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Cellulose ester A (see Table 5) was added to the dissolution tank containing methylene chloride and heated to completely dissolve, then, this was added to Azumi filter paper No. 3 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

-99 parts by mass of methylene chloride-4 parts by mass of cellulose ester A-11 parts by mass of a fine particle dispersion Cellulose ester A was used to prepare a main dope liquid having the following composition (dope of solution structure 1 in the following table).

  First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and the sugar ester compound A-5 was further added and dissolved in 8% by mass of the cellulose ester A and 3% by mass of the ester oligomer B-15 as a plasticizer. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

2 parts by mass of the fine particle additive solution is added to 100 parts by mass of the main dope solution and mixed thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ). It was cast uniformly on the band support.
In the obtained web (film), the solvent was evaporated until the residual solvent amount became 110%, and the web was peeled off from the stainless steel band support.
Subsequently, using a tenter, the film was stretched by 30% at 160 ° C. in a direction perpendicular to the film conveying direction with a residual solvent amount of 10%. After stretching, the width is maintained for several seconds, the tension in the width direction is relaxed, the holding is released, and further, the sheet is transported for 30 minutes in a drying zone set at 125 ° C. and dried. A cellulose ester film 1 having a thickness of 40 μm and a knurling having a width of 1 m and a height of 8 μm at the end was prepared.

<Composition of main dope solution (dope of solution structure 1 in the following table)>
Methylene chloride: 390 parts by mass Ethanol: 80 parts by mass Cellulose ester A: 100 parts by mass Sugar ester compound A-5: 8 parts by mass Ester oligomer B-15: 3 parts by mass Cellulose used above The contents of the ester A and the cellulose ester used in the following examples are shown.

(Production of cellulose ester films 1 to 7 and 9)
Other cellulose ester films were produced in the same manner as described above except that the dope solution configuration and production conditions were changed as shown in the following table.

(Preparation of cycloolefin film 8)
ZF14-100 (manufactured by ZEON Corporation) is stretched by 40% at 140 ° C in the film transport direction and 70% in the direction perpendicular to the film transport direction, and then held for several seconds while maintaining its width to ease the tension in the width direction. Then, the holding was released to obtain a film 8 having a film thickness of 40 μm.

(Re, Rth)
Re (550) and Rth (550) measured and calculated by the above method are shown as Re and Rth in the following table.

(ΔRe)
Similarly, (Re (630) −Re (450)) measured and calculated by the above method was defined as ΔRe (unit: nm).

(MD / TD elastic modulus average)
The average elastic modulus of each cellulose ester film was measured in the film transport direction (MD direction) and the film width direction (TD direction) using Toyo Baldwin Universal Tensile Tester (STM T50BP), and the average was calculated. did.

表中、ＥＧはエチレングリコール、ＰＧは、プロピレングリコール、ＴＰＡはテレフタル酸、ＰＡは、フタル酸、ＡＡはアジピン酸、およびＳＡはコハク酸を表す。

In the table, EG represents ethylene glycol, PG represents propylene glycol, TPA represents terephthalic acid, PA represents phthalic acid, AA represents adipic acid, and SA represents succinic acid.

(Production of polarizer)
A polyvinyl alcohol film having a refractive index of 1.545 at a wavelength of 380 nm and a refractive index of 1.521 at a wavelength of 780 nm and a thickness of 75 μm is uniaxially stretched 2.5 times to obtain 0.2 g of iodine and 60 g of potassium iodide. Was immersed in an aqueous solution containing 30 g / L for 30 seconds and then immersed in an aqueous solution containing 70 g / L of boric acid and 30 g / L of potassium iodide and simultaneously uniaxially stretched 6.0 times and held for 5 minutes. Finally, it was dried at room temperature for 24 hours to obtain a polarizer P having an average thickness of 30 μm and a polarization degree of 99.95%.

(Preparation of active energy ray-curable adhesive 1)
95 parts by weight of 3-ethyl-3 [(phenoxy) methyl] oxetane (“PhOX” manufactured by Toagosei Co., Ltd.), 3 parts by weight of a polybutadiene-based epoxy compound, 3 parts by weight of an alicyclic epoxy compound (“ERL4206” manufactured by Union Carbide) And 3 parts by weight of an antimony sulfonium salt compound (“SP-170” manufactured by Asahi Denka Kogyo Co., Ltd.) were mixed to obtain an active energy ray-curable adhesive 1.

(Preparation of active energy ray-curable adhesive 2)
High-purity hydrogenated epoxy agent ("jER YX8000" manufactured by Mitsubishi Chemical Corporation) 35 parts by weight, triarylsulfonyl salt compound ("CPI-100P" manufactured by San Apro) 4 parts by weight, 1 mass of benzoin methyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) Part was mixed and the active energy ray hardening-type adhesive 2 was obtained.

(Examples 1-9, Comparative Examples 1-4: Production of Polarizing Plate)
The polarizer P is sandwiched between the cellulose ester film 1 and FUJITAC TD80UF (Fuji Film Co., Ltd.) via the active energy ray curable adhesive 1, and a protective film is bonded to irradiate ultraviolet rays with an integrated light quantity of 3000 mJ / cm ^2. Thus, a polarizing plate 1 was obtained.

  Other polarizing plates were produced in the same manner as in Example 1 except that the conditions described in the following table were changed. However, in Comparative Example 5, a retardation film and a protective film were bonded so as to sandwich the polarizer by the following method. In Comparative Example 6, a polarizing plate was produced in the same manner as Comparative Example 5 except that the conditions described in the following table were changed.

(Comparative Examples 5 and 6: Production of polarizing plate)
A polarizing plate of Comparative Example 5 was produced from the produced cellulose ester film 1 and cellulose ester film 7 in accordance with the following steps 1 to 5.
Step 1: Soaked in a 2 mol% sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried to obtain cellulose ester film 1 and cellulose ester film 7 saponified on the side to be bonded to the polarizer.
Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.
Step 3: The excess adhesive adhered to the polarizer in Step 2 was gently wiped off, and the cellulose ester film 1 and the cellulose ester film 7 treated in Step 1 were laminated and arranged.
Step 4: Step 3 was laminated cellulose ester film 1 on the back side (the cellulose ester film 7 side) pressure 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.
Process 5: The sample which bonded the polarizer produced in the process 4, and the cellulose-ester film 1 and the cellulose-ester film 7 was dried for 5 minutes in a 80 degreeC dryer, and the polarizing plate of the comparative example 5 was produced.

(Axis shift of polarizing plate)
The obtained polarizing plate was taken out 2 m in the longitudinal direction, and a small piece of the polarizing plate was cut out at intervals of 20 cm from the center at equal intervals in the width direction every 50 cm in the longitudinal direction, and all of the cut out small piece samples were cut using Axoscan (manufactured by Axometrics). The angle between the slow axis of the film and the absorption axis of the polarizer was measured. Moreover, the axis | shaft deviation value of each small piece sample was calculated using Formula (X), and it judged as follows by the maximum value of the axis deviation value.
Formula (X) (axis misalignment) = | Angle −90 ° |
A: 0 ° ≦ (Maximum shaft misalignment) ≦ 0.3 °
B: 0.3 ° <(maximum value of shaft misalignment) ≦ 0.4 °
C: 0.4 ° <(maximum value of shaft misalignment)

[Manufacture of liquid crystal display devices]
The obtained polarizing plate of each Example and Comparative Example was bonded to the following panel.
Evaluation was made by removing the front and rear polarizing plates from the LC-46LV3 liquid crystal display of Sharp Corporation (hereinafter also referred to as a panel), and the polarizing plates of Example 1 were used for the front and rear sides of the liquid crystal panel. The liquid crystal display device of Example 1 was manufactured. In addition, the polarizing plates of the other examples and the comparative examples were arranged on the front side and the rear side of the liquid crystal panel to manufacture the liquid crystal display devices of the other examples and the comparative examples.

(Corner light leakage evaluation method)
The prepared liquid crystal panel mounted with the polarizing plate is placed in an environment of 40 ° C. and 95% for 24 hours, then placed in a 40 ° C. dry environment for 2 hours, and then lighted for 24 hours in an environment of 25 ° C. and 60%. did. A and B are practical levels.
A: There is no light leakage at the four corners of the panel, or light leakage is very weak.
B: Light leakage is observed at the four corners of the panel, but the boundary is unclear and light leakage is not noticeable.
C: Light leakage is observed at the four corners of the panel, and the part where the boundary is clear and the light leaks can be clearly seen.

(In-panel variation of front contrast)
Using a measuring device (BM5A, manufactured by TOPCON), a display device conditioned at 25 ° C. and a relative humidity of 60% for 24 hours, in a dark room, in a 0 degree polar angle direction and an azimuth angle 0 degree direction The luminance value of black display and white display was measured, and the contrast (white luminance / black luminance) was calculated to measure the front contrast of the liquid crystal display device. An area at the center of the panel corresponding to an area of 50% with respect to the total area of the panel was measured at intervals of 5 cm in length and width, and the obtained results were judged according to the following criteria. A and B are practical levels.
A (Front contrast minimum value) / (Front contrast maximum value) ≧ 0.70
B 0.70> (front contrast minimum value) / (front contrast maximum value) ≧ 0.50
C (Minimum value of front contrast) / (Maximum value of front contrast) <0.50
If the in-panel variation of the front contrast is evaluated as B or higher, there is no practical problem.

(Color change)
About each liquid crystal display device produced above, the hue | tone change (DELTA) u'v 'at the time of black display was each measured based on the following formula. Here, u′max (v′max) is the maximum of u ′ (v ′) and u′min (v′min) among the values measured in the range of azimuth angle 0 to 360 ° when the polar angle is 60 °. Is the smallest u ′ (v ′) among the values measured in the range of azimuth angle 0 to 360 ° at a polar angle of 60 °. The results are shown in the table below. A and B are practical levels.

Evaluation was performed as follows.
A: Δu′v ′ ≦ 0.10
B: 0.10 <Δu′v ′ <0.20
C: Δu′v ′ ≧ 0.20

  From the above table, the liquid crystal display devices using the polarizing plates that satisfy the requirements of the present invention (Examples 1 to 9) achieve high contrast even with a thin film, no axial misalignment or corner light leakage, and high front contrast, It can be seen that the color change is small. On the other hand, it can be seen that the liquid crystal display devices using the polarizing plates of Comparative Examples 1 to 6 are inferior to those of the Examples in terms of axial misalignment, corner light leakage, front contrast, and color change.

22 Protective film 12 Viewing side polarizer 15 Retardation film 13 Liquid crystal layer 14 Retardation film 11 Backlight side polarizer 21 Protective film

Claims (8)

A polarizing plate having a polarizer sandwiched between two protective films,
At least one protective film is a biaxial film having a film thickness of 45 μm or less mainly composed of cellulose acylate having a total acyl substitution degree of 1.5 to 2.5,
A value (unit: nm) (ΔRe) obtained by subtracting the in-plane retardation value at a wavelength of 450 nm from the retardation value in the in-plane direction at a wavelength of 630 nm is −2.0 ≦ ΔRe ≦ 10.0,
The polarizer and the biaxial film are bonded with an active energy curable adhesive.
Take out the polarizing plate 2m, take out small pieces at intervals of 50cm in the longitudinal direction at intervals of 20cm from the center in the width direction of the polarizing plate, measure the axial deviation value shown by the following formula (A), the maximum value of the axial deviation value is A polarizing plate characterized by being 0.4 ° or less.
Formula (A)
(Axis misalignment value) = | (angle formed by retardation film retardation axis and polarizer absorption axis) −90 ° | The polarizing plate according to claim 1, wherein the cellulose acylate is cellulose acetate. The polarizing plate according to claim 1 or 2, wherein the biaxial film contains an ester oligomer represented by the following general formula (1).
General formula (1) B- (GA) _n -GB
(Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.) The polarizing plate according to any one of claims 1 to 3, wherein the polarizer and the biaxial film are bonded with an adhesive layer having a thickness of 0.01 to 5 µm containing an active energy curable adhesive. . The polarizing plate according to claim 1, wherein the biaxial film is a single layer film. The polarizing plate according to claim 1, wherein the thickness of the protective film that is not the biaxial film is 10 to 40 μm, and the thickness of the polarizer is 3 to 20 μm. The liquid crystal display device which has a polarizing plate of any one of Claims 1-6. A liquid crystal display device, wherein the biaxial film side of the polarizing plate according to claim 1 is bonded to a VA liquid crystal cell via an adhesive.