JPWO2009004998A1 - Polarizing plate and liquid crystal display device - Google Patents

Abstract

The first polarizing plate protective film, the polarizer and the orientation of the rod-like liquid crystal arranged on the surface opposite to the first polarizing plate protective film of the polarizer and oriented vertically on the second polarizing plate protective film A polarizing plate having an optical compensation film provided with a fixed layer, the retardation Ro represented by the following formulas 2 and 3 at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH of the optical compensation film, In the polarizing plate in which Rt is Ro: 30 to 130 nm, Rt: −100 to 65 nm, and | Rt | <| Ro / 2 |, the wavelength dispersion characteristic D ( R40) is 2.0 to 6.5 nm. Formula 1: D (R40) = R40 (630) -R40 (480) (wherein R40 represents a retardation value measured by tilting the in-plane fast axis in the plane of the optical compensation film by 40 °). 630) and (480) represent respective measurement wavelengths (nm).)

Description

  The present invention relates to a polarizing plate and a liquid crystal display device, and more particularly to a polarizing plate suitable for a transverse electric field switching mode type liquid crystal display device, a polarizing plate with reduced color change when the viewing angle is changed, and a liquid crystal using the same The present invention relates to a display device.

  The transverse electric field switching mode type liquid crystal display device is excellent in color, contrast, viewing angle and the like in the liquid crystal mode of other liquid crystal display devices, for example, the TN mode, and in the vertical alignment mode (VA, MVA, PVA, etc.). On the other hand, it is excellent in display performance such as viewing angle, and also has excellent effects such as less luminance change due to viewing angle and less drop in response speed in halftone, so-called IPS (In Plane Switching) mode type liquid crystal display device As it came to be actively offered to the market.

  Examples of the IPS mode type liquid crystal display device include an FFS (fringe field switching) mode and an FLC (ferroelectric liquid crystal) mode in addition to the so-called IPS mode.

  Conventionally, the IPS system has a feature that a liquid crystal cell itself does not need to be compensated, and a wide viewing angle can be obtained without a compensation film (see, for example, Patent Document 1).

  However, when the polarizing plate used in the liquid crystal display device changes the viewing angle in the crossed Nicols state in the direction of 45 ° with respect to the absorption axis, light leakage occurs, thereby reducing the peripheral contrast of the liquid crystal display device. Is happening.

  In view of this, for example, a technique has been devised in which a heat-shrinkable optical film such as Patent Document 2 or Patent Document 3 is laminated on a polarizing plate to suppress light leakage of the polarizing plate. However, in this method, since there is a difficulty in making the film uniform, there is a problem of color variation, so-called color shift.

In Patent Document 4, it has been proposed to use a rod-like liquid crystal compound as a retardation layer, but it is still insufficient for improving the color shift.
JP 2000-131700 A Japanese Patent Laying-Open No. 2005-31626 JP 2006-126770 A JP 2005-265889 A

  Accordingly, an object of the present invention is to provide a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, and to provide a polarizing plate with reduced color change when the viewing angle is changed, and a liquid crystal display device using the same. It is in.

  One of the aspects of the present invention for achieving the above object is that the first polarizing plate protective film, the polarizer and the polarizer are disposed on the surface opposite to the first polarizing plate protective film, A polarizing plate having an optical compensation film in which a vertically fixed rod-like liquid crystal orientation layer is provided on a polarizing plate protective film, the wavelength of the optical compensation film in an environment of 23 ° C. and 55% RH In the polarizing plate in which the retardations Ro and Rt represented by the following formulas 2 and 3 at 590 nm are Ro: 30 to 130 nm, Rt: −100 to 65 nm, and | Rt | <| Ro / 2 | The optical compensation film has a wavelength dispersion characteristic D (R40) represented by the following formula 1 in the range of 2.0 to 6.5 nm.

Formula 1: D (R40) = R40 (630) -R40 (480)
(In the formula, R40 represents a retardation value measured by tilting 40 ° with the in-plane fast axis of the optical compensation film as a rotation axis. (630) and (480) represent respective measurement wavelengths (nm). )

It is a schematic diagram which shows the structure of the polarizing plate and liquid crystal display device which concern on this invention.

  The above object of the present invention is achieved by the following configurations.

(1) A first polarizing plate protective film, a polarizer, and a rod-like liquid crystal that is disposed on a surface of the polarizer opposite to the first polarizing plate protective film and is oriented vertically on the second polarizing plate protective film A polarizing plate having an optical compensation film provided with a layer having a fixed orientation of the optical compensation film, wherein the optical compensation film is represented by the following formulas 2 and 3 at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. Foundation Ro, Rt
Ro: 30 to 130 nm
Rt: -100 to 65 nm
| Rt | <| Ro / 2 |
The polarizing plate according to claim 1, wherein the optical compensation film has a wavelength dispersion characteristic D (R40) represented by the following formula 1 of 2.0 to 6.5 nm.

Formula 1: D (R40) = R40 (630) -R40 (480)
(In the formula, R40 represents a retardation value measured by tilting 40 ° with the in-plane fast axis of the optical compensation film as a rotation axis. (630) and (480) represent respective measurement wavelengths (nm). )
Formula 2: Ro = (nx−ny) × d
Formula 3: Rt = ((nx + ny) / 2−nz) × d
(Wherein, the refractive index in the slow axis direction in the plane of the optical compensation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, d is the optical index Represents the thickness (nm) of the compensation film.)
(2) The second polarizing plate protective film has an acrylic polymer and a saccharide in which at least one of at least one of a pyranose structure or a furanose structure is 1 to 12 and all or a part of the OH groups of the structure is esterified It is a cellulose-ester film containing the at least 1 sort (s) compound chosen from an ester compound, The polarizing plate as described in said (1) characterized by the above-mentioned.

  (3) The polarizing plate according to (2), wherein the cellulose ester film contains the acrylic polymer.

  (4) The polarizing plate according to (2), wherein the cellulose ester film contains the sugar ester compound.

  (5) The polarizing plate according to (2), wherein the cellulose ester film contains the acrylic polymer and the sugar ester compound.

  (6) The polarizing plate according to (2), wherein the cellulose ester film contains the sugar ester compound and the polyester compound.

  (7) On the side of the optical compensation film of the polarizing plate according to any one of (1) to (6), a transverse electric field switching mode liquid crystal cell, a third polarizing plate protective film, and a second polarized light And in this order, the in-plane slow axis of the optical compensation film of the polarizing plate and the alignment direction of the liquid crystal cell are parallel or perpendicular, And the 3rd polarizing plate protective film is Ro: 0-5nm, Rt: -10-10nm, The liquid crystal display device characterized by the above-mentioned.

  According to the present invention, a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, which reduces a change in tint when the viewing angle is changed, and has excellent wavelength dispersion and a liquid crystal display device using the same Can be provided.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  As a result of intensive studies on the above problems, the inventors of the present invention have found that in the transverse electric field switching mode type (also referred to as IPS mode type) liquid crystal display device, the wavelength dispersion characteristic of retardation of the polarizing plate protective film, particularly the film thickness direction. It has been confirmed that controlling the wavelength dispersion characteristics of the phase difference has a significant effect on the color change when the viewing angle is changed, and by further study, means that can control the color variation at the appropriate point of the viewing angle. Has been reached.

Hereinafter, the present invention will be described in detail for each element.
<Ro, Rt and wavelength dispersion of optical compensation film>
The first polarizing plate protective film, the polarizer, and the orientation of the rod-like liquid crystal disposed on the surface of the polarizer opposite to the first polarizing plate protective film and oriented vertically on the second polarizing plate protective film A polarizing plate having an optical compensation film provided with a fixed layer is disposed on the viewing side with respect to the liquid crystal cell.

The optical compensation film constituting the polarizing plate characterizing the present invention has retardation Ro and Rt represented by the following formulas 2 and 3 at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH.
Ro: 30 to 130 nm
Rt: -100 to 65 nm
| Rt | <| Ro / 2 |
It is.

  These Ro and Rt values are known as retardation necessary for the IPS mode liquid crystal display device.

  In the present invention, the optical compensation film further has a wavelength dispersion characteristic D (R40) represented by the following formula 1 in the range of 2.0 to 6.5 nm.

Formula 1: D (R40) = R40 (630) -R40 (480)
(In the formula, R40 represents a retardation value measured by tilting 40 ° with the in-plane fast axis of the optical compensation film as the rotation axis (tilt axis). (630) and (480) are the respective measured wavelengths (nm). )
Formula 2: Ro = (nx−ny) × d
Formula 3: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the slow axis direction in the plane of the optical compensation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, and d is the optical compensation film. (This represents the total thickness of the cellulose ester film and the rod-like liquid crystal layer).
Since the optical compensation film has this wavelength dispersion, the color shift is greatly improved in the IPS mode liquid crystal display device.

  In order for the optical compensation film of the present invention to have the above-described wavelength dispersion, the second polarizing plate protective film has at least one of an acrylic polymer and a pyranose structure or a furanose structure at least 12 A cellulose ester film containing at least one compound selected from sugar ester compounds obtained by esterifying all or part of the OH groups of the structure, wherein the alignment of rod-like liquid crystals aligned vertically on the film This is achieved by having a fixed layer.

  That is, at least one kind selected from an acrylic polymer and a sugar ester compound obtained by esterifying all or part of the OH groups of the structure having at least one of a pyranose structure or a furanose structure in the cellulose ester and at least one of the pyranose structure or the furanose structure By adding a compound, and further arranging a vertically aligned rod-like liquid crystal layer on the film, and adjusting the addition amount and the thickness of the layer, the retardation and wavelength dispersion of the optical compensation film are within a desired range. Can be adjusted. When a cellulose ester contains the said sugar ester compound, it is preferable to contain an acrylic polymer simultaneously. Moreover, it is also preferable to contain a sugar ester compound and polyester simultaneously.

  The optical compensation film of the present invention comprises a cellulose ester film and a layer in which the vertical alignment of the rod-like liquid crystal is fixed, and the respective retardation and wavelength dispersion are as follows.

Cellulose ester film 30 ≦ Ro ≦ 115 nm
100 ≦ Rt ≦ 250 nm
Vertically aligned rod-like liquid crystal layer
0 ≦ Ro ≦ 10nm
−400 ≦ Rt ≦ −100 nm
In the optical compensation film of the present invention, Ro and Rt are the sum of the values of the layers in which the orientation of the cellulose ester film and the rod-like liquid crystal is fixed.

<Cellulose ester>
The cellulose ester film used in the present invention contains 60 to 100% by mass of cellulose ester. It is preferable that the total acyl group substitution degree of the cellulose ester is 2.1 to 2.9.

  The cellulose ester used in the present invention is a carboxylic acid ester having about 2 to 22 carbon atoms or an aromatic carboxylic acid ester, and particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, as the cellulose ester, propionate group, butyrate group or phthalyl group is bonded in addition to acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate. A mixed fatty acid ester of cellulose can be used. The butyryl group forming butyrate may be linear or branched.

  As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are particularly preferably used.

  As a cellulose ester used by this invention, what satisfies the following formula (1) and (2) simultaneously is preferable.

Formula (1) 2.1 <= X + Y <= 2.9
Formula (2) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, and preferably 0.1 ≦ Y ≦ 1.5 and 2.1 ≦ X + Y ≦ 2.9. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  In addition, this measuring method can be used also as a measuring method of the other polymer in this invention.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester used in the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  Cellulose esters are also affected by trace metal components in cellulose esters.

  These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small.

  The iron (Fe) component is preferably 1 ppm or less. As for the calcium (Ca) component, it is easy to form a coordination compound, that is, a complex with an acidic component such as carboxylic acid or sulfonic acid, and many ligands. Starch, turbidity).

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter.

  Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After being performed, it can be analyzed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

<Acrylic polymer>
It is preferable that the cellulose-ester film used for the polarizing plate protective film which concerns on this invention contains the acrylic polymer whose weight average molecular weight which shows negative orientation birefringence with respect to a extending | stretching direction is 500-30000.

  By controlling the composition of the polymer so that the weight average molecular weight of the polymer is 500 or more and 30000 or less, the compatibility between the cellulose ester and the polymer can be improved.

  In the present invention, the acrylic polymer refers to a homopolymer or copolymer of acrylic acid or methacrylic acid ester.

  The polymer has a weight average molecular weight of 500 or more and 30000 or less, and it is desirable to use a polymerization method capable of making the molecular weight uniform.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like.

  The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring.

  The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl) and the like can be mentioned, but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  Among acrylic polymers having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. % Is preferable.

  The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

  In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and preferably 50 to 80% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in the acrylic polymer in an amount of 2 to 20% by mass.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

  The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, low moisture permeability, and polarized light. It is particularly excellent in adhesiveness with a polarizer as a plate protective film, and has the effect of improving the durability of the polarizing plate.

  The method of having a hydroxyl group at at least one terminal of the main chain of the acrylic polymer is not particularly limited as long as it has a hydroxyl group at the terminal of the main chain, but azobis (2-hydroxyethylbutyrate) A method using a radical polymerization initiator having such a hydroxyl group, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and terminating a hydroxyl group by living ion polymerization. A compound having one thiol group and a secondary hydroxyl group as disclosed in JP 2000-128911 A or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination The method described in the above publication is particularly preferred.

  The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  The acrylic polymer used in the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule, and an ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group. A polymer X having a weight average molecular weight of 5,000 to 30,000, obtained by copolymerizing the above, or a polymer Y having a weight average molecular weight of 500 to 3,000, obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. Preferably there is.

(Polymer X, Polymer Y)
The polymer X used in the present invention comprises an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. It is a polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization.

  Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-(Xa) m- (Xb) n- (Xc) p-
More preferably, it is a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2) -] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
(In the formula, R 1 and R ₃ represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R ₄ represents —CH ₂ —, —C ₂ H ₄ — or —C _3. Represents H _6- , Xc represents a monomer unit that can be polymerized to Xa and Xb, m, n, and p represent a molar composition ratio, where m and n are not 0 at the same time, m + n + p = 100 .)
Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-ethoxyethyl) ) Or the like, or those obtained by replacing the acrylic ester with a methacrylic ester.

  Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high.

  Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because the cellulose ester film has advantages such as less dimensional change under high temperature and high humidity and less curling as a polarizing plate protective film.

  When the weight average molecular weight is 30000 or less, the compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity, and further haze generation immediately after film formation is suppressed.

  The weight average molecular weight of the polymer X used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually room temperature to 130 ° C., preferably 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be based on the same method as the case of the said cellulose ester.

  The polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring.

  A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance.

  Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
-(Ya) k- (Yb) q-
More preferably, it is a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6) -] k- [Yb] q-
(Wherein, R5 is, .Yb .R6 representing H or CH ₃ is representing an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms, .k and q represents the Ya and copolymerizable monomer units, This represents the molar composition ratio, where k ≠ 0 and k + q = 100.)
Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In this case, the terminal of the polymer X and the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. By this terminal residue, the compatibility between the polymers X and Y and the cellulose ester can be adjusted.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C.

  After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained.

  The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimensional stability. Are better.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y sufficiently act to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<Ester compound in which at least one of pyranose structure or furanose structure is 1 or more and 12 or less and all or part of OH groups of the structure are esterified>
The cellulose ester film used in the present invention includes an ester compound having at least one pyranose structure or at least one furanose structure and esterifying all or part of the OH groups of the structure. To do. In the present invention, ester compounds are collectively referred to as sugar ester compounds.

  Examples of the sugar ester compound according to the present invention include the following, but the present invention is not limited thereto.

  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 groups in the pyranose structure or furanose structure of the present invention is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, An aromatic 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, serotic 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-pyroca Succinic 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- Although coumaric acid can be mentioned, benzoic acid is particularly preferable.

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

  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, and xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₃₁ > -R < ₃₅ >, R < ₄₁ > -R < ₄₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent an integer of 0-12, respectively, and m + n represents an integer of 1-12.

R _{31 to} R ₃₅ and R _{41 to} R ₄₅ are particularly preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₄₆ (p is 0 to 5), and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and further, these alkyl groups, alkenyl groups, and phenyl groups. May have a substituent. Oligosaccharides can also be produced in the same manner as the sugar ester compound according to the present invention.

  Next, an example of the manufacture example of a sugar ester compound is described.

  Acetic anhydride (200 ml) was added dropwise to a solution obtained by adding pyridine (100 ml) to glucose (29.8 g, 166 mmol), and allowed to react for 24 hours. Thereafter, the solution was concentrated by evaporation and poured into ice water. After standing for 1 hour, the mixture was filtered through a glass filter to separate the solid and water. The solid on the glass filter was dissolved in chloroform and separated with cold water until it became neutral.

  The organic layer was separated and dried over anhydrous sodium sulfate. After removing anhydrous sodium sulfate by filtration, chloroform was removed by evaporation and further dried under reduced pressure to obtain glycolose pentaacetate (58.8 g, 150 mmol, 90.9%). In addition, the above-mentioned monocarboxylic acid can be used instead of the acetic anhydride.

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

Compound 23
Of the eight substituents R3 present in the “Compound 3”, 0 to 3 R3 are substituted with hydrogen atoms.

  The cellulose ester film used in the present invention may contain the sugar ester compound according to the present invention in an amount of 1 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. In particular, 5 to 30% by mass is preferably included. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out.

<Bar-shaped liquid crystal layer vertically aligned on cellulose ester film>
The optical compensation film of the present invention is obtained by applying a liquid crystal material or a liquid crystal solution to a cellulose ester film constituting the second polarizing plate protective film, drying and heat-treating (also referred to as orientation treatment), and performing ultraviolet curing or thermal polymerization. The liquid crystal alignment is fixed, and it has a retardation layer of rod-like liquid crystal aligned in the vertical direction. The rod-like liquid crystal layer according to the present invention is also called a rod-like liquid crystal cured layer.

  Here, “orienting in the vertical direction” means that the rod-like liquid crystal is within a range of 70 to 90 ° (the vertical direction is 90 °) with respect to the film surface. The rod-like liquid crystal may be oriented obliquely or the orientation angle may be gradually changed. Preferably it is the range of 80-90 degrees.

  The rod-like liquid crystal layer according to the present invention is a retardation layer made of rod-like liquid crystal aligned in the vertical direction in which Ro is in the range of 0 to 10 nm and Rt is in the range of −100 to −400 nm. Further, Ro is more preferably in the range of 0 to 5 nm.

  When a rod-like liquid crystal layer is formed by aligning rod-like liquid crystals, an alignment film coated with a vertical alignment agent that aligns so-called liquid crystal materials in the vertical direction is used, and the liquid crystal material is vertically oriented and then fixed. be able to.

  When the liquid crystal material itself is aligned in the vertical direction at the air interface, the alignment regulating force extends to the interface opposite to the air interface, and the alignment film is not particularly necessary, and this is also preferable from the viewpoint of simplifying the configuration. preferable.

  As a specific method for vertically aligning the liquid crystal material, an alignment film composed of a cross-linked product of a block polymer composition containing a (meth) acrylic block polymer described in JP-A-2005-148473 and the like is used. Known methods such as a method of using, a method of using a vertical alignment film described in JP 2005-265889 A, and a method of using an air interface vertical alignment agent can be used.

  In order to bring the rod-shaped liquid crystal layer into the above range, it is preferable to control the alignment of the rod-shaped liquid crystal layer, the film thickness control, the temperature during UV curing, the tilt angle control, and the pretilt angle at the support / air interface.

  The liquid crystal layer is formed by curing a liquid crystal material capable of forming a liquid crystal phase at a predetermined temperature with a predetermined liquid crystal regularity. The upper limit of the temperature showing the liquid crystal phase is not particularly limited as long as the cellulose ester film of the base material is not damaged.

  Specifically, a temperature of 120 ° C. or lower is preferable from the viewpoint of easy control of process temperature and maintenance of dimensional accuracy, and a liquid crystal material that becomes a liquid crystal phase at a temperature of 100 ° C. or lower is preferably used. On the other hand, the lower limit of the temperature showing the liquid crystal phase can be said to be a temperature at which the liquid crystal material can maintain the alignment state when used as a polarizing plate.

  As the liquid crystal material used for the rod-like liquid crystal layer according to the present invention, a polymerizable liquid crystal material is preferably used. The polymerizable liquid crystal material can be used by being polymerized by irradiating with predetermined actinic radiation. In the polymerized state, the vertical alignment state is fixed.

  As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and they can also be mixed with each other.

  Of the above, a polymerizable liquid crystal monomer is preferably used as the polymerizable liquid crystal material because of its high sensitivity during alignment and easy vertical alignment.

  Specific examples of the polymerizable liquid crystal monomer include a rod-like liquid crystal compound (I) represented by the following general formula (1) and a rod-like liquid crystal compound (II) represented by the following general formula (2). be able to. As the compound (I), two or more compounds included in the general formula (1) can be mixed and used. Similarly, the compound (II) is included in the general formula (2). Two or more kinds of compounds may be mixed and used. In addition, one or more compounds (I) and one or more compounds (II) may be mixed and used.

In the general formula (1) representing the compound (I), R ¹ and R ² each represent hydrogen or a methyl group, but R ¹ and R ² are both hydrogen due to the wide temperature range showing the liquid crystal phase. preferable.

  X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably chlorine or a methyl group.

  Moreover, a and b which show the chain length of the alkylene group which is a spacer with the (meth) acryloyloxy group of both ends of the molecular chain of a compound (I), and an aromatic ring are respectively arbitrary integers in the range of 2-12. Although it can take, it is preferable that it is the range of 4-10, and it is more preferable that it is the range of 6-9.

  In addition to the above, in the present invention, conventionally known materials can be appropriately selected and used as the polymerizable liquid crystal oligomer and the polymerizable liquid crystal polymer.

  In the present invention, a photopolymerization initiator is used as required in addition to the polymerizable liquid crystal material. When polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary. However, in the case of curing by, for example, ultraviolet (UV) irradiation, which is generally used, photopolymerization is usually performed. An initiator is used to promote polymerization.

  As photopolymerization initiators, benzyl (also called bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-benzoyl-4'-methyldiphenyl sulfide, benzylmethyl ketal, dimethylamino Methylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4 -(Methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2- Droxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2- Examples include methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, or 1-chloro-4-propoxythioxanthone. it can.

  In general, the addition amount of the photopolymerization initiator is preferably 0.01% to 20%, more preferably 0.1% to 10%, and still more preferably 0.5% to 5%. Can be added to the polymerizable liquid crystal material used in the present invention.

  In addition to the photopolymerization initiator, a sensitizer can be added as long as the object of the present invention is not impaired.

  The film thickness of the liquid crystal layer in the present invention is preferably in the range of 0.1 μm to 20 μm, and more preferably in the range of 0.2 to 10 μm.

  A polymerizable liquid crystal material is prepared by using a composition for forming a liquid crystal layer by blending a photopolymerization initiator, a sensitizer, etc., if necessary, and coating on a substrate to form a liquid crystal layer forming layer. To do.

  As a method of forming a layer in which the alignment of liquid crystal is fixed, for example, a dry film or the like is formed in advance and a layer in which the alignment of liquid crystal is fixed is laminated on a substrate, or a liquid crystal composition is dissolved. Alternatively, it is possible to use a method of melting and coating on a substrate, but in the present invention, a liquid crystal composition is added with a solvent and a coating composition in which other components are dissolved is used. It is preferable to form a layer in which the orientation of the liquid crystal is fixed by coating on the substrate and removing the solvent. This is simple in terms of process as compared with other methods.

  The solvent is not particularly limited as long as it is a solvent capable of dissolving the above-described polymerizable liquid crystal material and the like and does not deteriorate the properties of the transparent resin film. Specifically, benzene, Hydrocarbons such as toluene, xylene, n-butylbenzene, diethylbenzene, tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene, diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or 2,4- Ketones such as pentanedione; ethyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, or γ-butyrolactone Amides solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, or dimethylacetamide; chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, or orthodichlorobenzene Halogen solvents such as t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve, or butyl cellosolve; phenols, One or more of phenols such as parachlorophenol can be used.

  If only a single type of solvent is used, the solubility of the polymerizable liquid crystal material or the like may be insufficient, or the substrate may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents.

  Of the above-mentioned solvents, preferred as a single solvent are a hydrocarbon solvent and a glycol monoether acetate solvent, and a preferred mixed solvent is a mixed system of ethers or ketones and glycols. It is.

  The concentration of the solution depends on the solubility of the polymerizable liquid crystal material or the like and the film thickness of the liquid crystal layer to be produced, but cannot be defined unconditionally, but is usually preferably 1% to 60%, more preferably 3% to It is adjusted within the range of 40%.

  Compounds other than those described above can be added to the composition for forming a liquid crystal layer used in the present invention within a range not impairing the object of the present invention.

  Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amine epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like (meth) Ak Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting le acid, or a photopolymerizable liquid crystal compound, and the like having an acrylic group or methacrylic group.

  The amount of these compounds added to the composition for forming a liquid crystal layer according to the present invention is selected within a range that does not impair the purpose of the present invention, and is generally 40% or less of the composition for forming a liquid crystal layer according to the present invention. And more preferably 20% or less.

  Addition of these compounds improves the curability of the liquid crystal material in the present invention, increases the mechanical strength of the resulting liquid crystal layer, and improves its stability.

  In addition, a surfactant or the like can be added to the composition for forming a liquid crystal layer containing a solvent in order to facilitate coating. Examples of surfactants that can be added include cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides and polyamine derivatives; polyoxyethylene-polyoxypropylene condensates, primary or secondary Alcohol ethoxylates, alkylphenol ethoxylates, polyethylene glycol and esters thereof, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonates, alkyl phosphates, aliphatic or aromatic sulfonic acid formalin condensates, etc. Anionic surfactants; amphoteric surfactants such as laurylamidopropylbetaine and laurylaminoacetic acid betaine; nonionics such as polyethylene glycol fatty acid esters and polyoxyethylene alkylamine Surfactant: Perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl trimethyl ammonium salt, perfluoroalkyl group / hydrophilic group-containing oligomer, perfluoroalkyl / lipophilic group Fluorosurfactants such as containing oligomer perfluoroalkyl group-containing urethanes.

  The amount of surfactant added depends on the type of surfactant, the type of liquid crystal material, the type of solvent, and the type of alignment film on which the solution is applied. 10 ppm to 10% is preferable, more preferably 100 ppm to 5%, and still more preferably 0.1 to 1%.

  As a method for coating the composition for forming a liquid crystal layer, a spin coating method, a roll coating method, a printing method, a dip pulling method, a die coating method, a casting method, a bar coating method, a blade coating method, a spray coating method, a gravure coating method , Reverse coating method or extrusion coating method.

  The method for removing the solvent after coating the composition for forming a liquid crystal layer is performed, for example, by air drying, heat removal, or removal under reduced pressure, or a combination thereof. By removing the solvent, a layer in which the alignment of the liquid crystal is fixed is formed.

  In the step of curing the polymerizable liquid crystal material, energy for curing the polymerizable liquid crystal material is given, and thermal energy may be used, but it is usually performed by irradiation with ionizing radiation capable of causing polymerization.

  If necessary, a polymerization initiator may be contained in the polymerizable liquid crystal material. The ionizing radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus, and the wavelength. Is preferably from 150 to 500 nm, more preferably from 250 to 450 nm, and even more preferably from 300 to 400 nm.

  In the present invention, a method of performing radical polymerization by irradiating ultraviolet rays (UV) as actinic radiation and generating radicals from the polymerization initiator with ultraviolet rays is preferable. Since the method using UV as the actinic radiation is an already established technique, it can be easily applied to the present invention including the polymerization initiator to be used.

  As a light source for irradiating ultraviolet rays, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), or a short arc discharge lamp (ultra-high-pressure mercury lamp, xenon) Lamp, mercury xenon lamp) and the like.

  In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity may be appropriately adjusted depending on the composition of the polymerizable liquid crystal material used for forming the layer in which the alignment of the liquid crystal is fixed and the amount of the photopolymerization initiator.

  The alignment fixing step by irradiation with actinic radiation may be performed at the processing temperature in the step of forming the liquid crystal layer forming layer described above, that is, the temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, It may be performed at a lower temperature.

<< First and fourth polarizing plate protective films >>
As a base material used for the first and fourth polarizing plate protective films, a transparent cellulose ester film or a cycloolefin film is preferable, and a cellulose ester film in a retardation range not particularly limited to the above cellulose ester film is used. can do.

  The term “transparent” as used in the present invention means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  Examples of the commercially available cellulose ester film that can be used in the first or fourth polarizing plate protective film of the present invention include Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4FR, KC8UY-HA, KC8UX-RHA (manufactured by Konica Minolta Opto) and the like can be mentioned.

  These films may be films produced by melt casting film formation or films produced by solution casting film formation.

<Third polarizing plate protective film>
The third polarizing plate protective film of the present invention preferably has retardation Ro in the range of 0 to 5 nm and Rt in the range of -10 to 10 nm.

  The material of the third polarizing plate protective film of the present invention is not limited as long as it has the above-mentioned retardation, but is preferably a cellulose ester film from the viewpoint of easy adjustment of the retardation.

For adjusting the retardation of the cellulose ester film, a sugar ester in which at least one of the above-mentioned acrylic polymer, pyranose structure or furanose structure is 1 to 12 and all or part of the OH groups of the structure is esterified. This can be done by adding a compound.
<Other additives>
The cellulose ester film used in the present invention can appropriately contain additives as necessary.

(Plasticizer)
The cellulose ester film used in the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer, phosphate ester plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula _{(a) R 1 - (OH} ) n
However, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as alkyl group, methoxy group or ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula _{(b) R 2 (COOH)} m (OH) n
(Wherein R ₂ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improving the retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The polyester plasticizer (polyester compound) is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by the following general formula (c) can be used.

General formula (c) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic 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 the general formula (c), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer that can be used in the present invention 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-penta Diol, 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.

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as a seed or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. 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 polyester plasticizer used in the present invention 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 value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Hereinafter, synthesis examples of aromatic terminal ester plasticizers that can be used in the present invention will be shown.

<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst. While refluxing the monohydric alcohol, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Next, the distillate was removed at 200-230 ° C. under reduced pressure of 1.33 × 10 4 Pa to 4 × 10 2 Pa or less, and then filtered to obtain an aromatic terminal ester plasticizer having the following properties. .

Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2
Although the specific compound of the aromatic terminal ester plasticizer which can be used for this invention below is shown, this invention is not limited to this.

(UV absorber)
The cellulose ester film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  The fine particles used in the present invention include, as examples of inorganic compounds, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering) or SWJ (Toray static type in-tube mixer Hi-Mixer) is preferably used.
<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose-ester film concerning this invention is demonstrated.

  The cellulose ester film according to the present invention 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.

  The cellulose ester film according to the present invention is prepared by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support, and casting the dope. Is performed by a step of drying as a web, a step of peeling from a 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 may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  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 (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 this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably.

  Moreover, it is preferable that 0.01-2 mass% of water contains in dope. 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 does not boil under pressure, in order to prevent the formation of massive undissolved materials called gels and mamacos.

  Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  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.

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

Residual solvent amount (% by mass) = {(MN) / N} × 100
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 according to the present invention, 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.

  Although the film thickness of a cellulose-ester film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  The cellulose ester film according to the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

"Polarizer"
The first polarizing plate protective film, the polarizer, and the orientation of the rod-like liquid crystal disposed on the surface of the polarizer opposite to the first polarizing plate protective film and oriented vertically on the second polarizing plate protective film A polarizing plate having an optical compensation film provided with a fixed layer (hereinafter referred to as polarizing plate 1) is disposed on the viewing side with respect to the liquid crystal cell, and includes a third polarizing plate protective film, a second polarizer, and A polarizing plate in which the fourth polarizing plate protective film is arranged in this order (hereinafter referred to as polarizing plate 2) is arranged on the backlight side with respect to the liquid crystal cell.

  These polarizing plates can be produced by a general method. For example, a polyvinyl alcohol film is formed and uniaxially stretched and dyed or dyed and then uniaxially stretched, and then a polarizer preferably subjected to a durability treatment with a boron compound is used with a polyvinyl alcohol adhesive. It can be manufactured by pasting with a saponified cellulose ester film.

<Display device>
In the liquid crystal display device according to the present invention, the polarizing plate 1 is disposed on the viewing side of the liquid crystal cell, the polarizing plate 2 is disposed on the backlight side of the liquid crystal cell, and the optical compensation film (vertically on the second polarizing plate protective film). A film provided with a layer in which the orientation of the oriented rod-like liquid crystal is fixed) and the third polarizing plate protective film are respectively positioned on the liquid crystal cell side.

  In the liquid crystal display device according to the present invention, the slow axis of the optical compensation film and the alignment direction of the liquid crystal cell (the same direction as the rubbing axis of the liquid crystal cell) are parallel or perpendicular, and preferably parallel.

  Here, “parallel” and “perpendicular” mean within a range of ± 20 ° with respect to a strict angle, and preferably within a range of ± 10 °.

  The absorption axis of the polarizing plate 1 of the present invention and the slow axis of the optical compensation film are preferably perpendicular.

  The polarizing plate 1 and the polarizing plate 2 are arranged in a crossed Nicols state as usual. That is, the absorption axis of the polarizing plate 1 and the absorption axis of the polarizing plate 2 are perpendicular.

  In the present invention, the slow axis of the polarizing plate protective film can be known by an automatic birefringence meter (manufactured by KOBRA 21DH Oji Scientific Co., Ltd.).

  The polarizing plate according to the present invention is suitably used for an IPS mode liquid crystal display device. In particular, even a large-screen liquid crystal display device having a 30-inch or larger screen has an effect of high contrast, particularly suppressing a change in color depending on the viewing angle, and preventing eyes from being tired even during long-time viewing.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<< Measurement of retardation and chromatic dispersion >>
In the examples, retardation measurement was performed in an environment of 23 ° C., 55% RH, and wavelength of 590 nm using KOBRA 21ADH manufactured by Oji Scientific Instruments. Further, when calculating the retardation in the thickness direction, a value obtained by measuring the refractive index of each layer using an Abbe refractometer was used.

  In the case of a laminate, the average value of the refractive index of each layer was used. The following formula 1, formula 2, and formula 3 were used for calculation of retardation and wavelength dispersion characteristic D (R40).

Formula 1: D (R40) = R40 (630) -R40 (480)
(In the formula, R40 represents a retardation value measured by tilting 40 ° with the slow axis in the plane of the sample as the rotation axis. (630) and (480) represent the respective measurement wavelengths (nm).)
Formula 2: Ro = (nx−ny) × d
Formula 3: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the fast axis direction in the plane of the optical compensation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, and d is the optical compensation film. Represents the thickness (nm).)
<< Production of Optical Compensation Films 101-125, 201-205 >>
<Preparation of cellulose ester film>
A cellulose ester film 101 serving as a substrate of the optical compensation film 101 was produced according to the following.

<Synthesis of acrylic polymer>
(Synthesis of polymer X)
Polymer X was synthesized with reference to the method described in JP-A-2003-12859. That is, a monomer mixture obtained by mixing methyl methacrylate (MMA): 2-hydroxyethyl methacrylate (HEMA) at a mass ratio of 95: 5 into a glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer. 40 g, a chain transfer agent of 3.0 g of mercaptopropionic acid and 30 g of toluene were charged, and the temperature was raised to 90 ° C.

  Thereafter, 60 g of the monomer mixture was dropped from one dropping funnel over 3 hours, and 0.6 g of azobisisobutyronitrile dissolved in 14 g of toluene was dropped from the other funnel over 3 hours.

  Thereafter, 0.6 g of azobisisobutyronitrile dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain polymer X. The weight average molecular weight was 8000.

(Dope solution A for cellulose ester)
Cellulose ester (acetyl group substitution degree: 2.9, Mn: 110000, Mw / Mn = 2.0) 100 parts by mass Polymer X 5 parts by mass Polymer Y 10 parts by mass Sugar ester compound (Compound 3) 5 parts by mass Methylene chloride 430 40 parts by mass of ethanol 40 parts by mass or more of ethanol was put into a sealed container, heated, stirred and completely dissolved, and produced by Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. 24, and the dope liquid A was prepared. The dope solution A was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line.

  The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film on the metal support (which is called a web after casting on the stainless steel belt) is dried by applying hot air of 44 ° C., and the residual solvent in the peeling is peeled off at 120 mass%. The film was stretched to a stretching ratio of 1.1 times in the casting direction by applying a tension of, and then adjusted so that the residual solvent amount was 4 mass% and the temperature was 123 ° C., and the web end was gripped with a tenter. The film was stretched so as to have a stretching ratio of 1.1 times in the width direction.

  After stretching, the film was held for several seconds while maintaining its width, then the tension in the width direction was relaxed, the width was released, and the film was dried at 120 ° C. The cellulose ester film 101 which is the second polarizing plate protective film having a film thickness of 41 μm and a width of 1.5 m produced as described above was wound around a core.

  Next, the following rod-like liquid crystal layer was provided on the cellulose ester film 101.

  45% by mass of the compound of the following formula (a)

  45% by mass of the compound of the following formula (b)

  10% by mass of the compound of the following formula (d)

A polymerizable liquid crystal composition (H) comprising: The polymerizable liquid crystal composition (H) had a nematic-isotropic liquid phase transition temperature of 73 ° C.

  Polymerizability obtained by adding 0.2% of photopolymerization initiator Lucillin TPO (manufactured by Basf) and 0.1% of hindered amine LS-765 (manufactured by Sankyo Lifetech Co., Ltd.) to 99.7% of the polymerizable liquid crystal composition (H). A liquid crystal composition (H1) was prepared.

  Next, a xylene solution containing 33% of the polymerizable liquid crystal composition (H1) was prepared. This xylene solution was applied to each film with a thickness of 5 μm by a die coater. The coated film was irradiated with an ultraviolet ray of 250 mJ / mm at an oxygen concentration of 0.2% and a temperature of 38 ° C. for 80 seconds to cure the polymerizable liquid crystal composition (H1) to form an alignment fixed layer of rod-like liquid crystals. As described above, an optical compensation film 101 (a cellulose ester film with a rod-like liquid crystal orientation fixing layer) was obtained.

  Moreover, without changing the composition ratio of the compounds represented by formula (a), formula (b), and formula (d), a polymerizable liquid crystal composition was prepared by changing the film thickness. An alignment cured layer of rod-like liquid crystal was prepared.

  Furthermore, the cellulose ester described in Table 1, the polymer X and polymer Y (described in Table 2), the type of the sugar ester compound (compounds 1 to 23), the plasticizer, and the alignment fixed layer of the rod-shaped liquid crystal are changed to the optical compensation film 101. Similarly, optical compensation films 102 to 125 having the retardations shown in Table 3, Table 4, and Table 5 and a third polarizing plate protective film were produced. In addition, the addition amount of the acrylic polymer in Table 3 and Table 4, a sugar ester compound, and a plasticizer represents the value with respect to 100 mass parts of cellulose esters.

  For comparison, an optical compensation film 201 using the second retardation region 1 described in Example columns [0072] to [0076] of JP-A-2005-265889 was prepared.

  In addition, the coating liquid in which the second retardation region 1 was prepared was diluted twice with methyl ethyl ketone and applied with a # 3.5 wire bar, and the coating liquid in which the second retardation region 1 was prepared. Compensation film 203 prepared by applying # 5 with a wire bar, and the optical compensation film 203 prepared by diluting the coating solution prepared with the second retardation region 1 2.1 times with methyl ethyl ketone and applying with a wire bar # 3 An optical compensation film 205 was prepared in the same manner by applying the coating liquid prepared with the film 204 and the second retardation region 1 with a # 3.5 wire bar.

<Production of polarizing plate>
A 120 μm-thick polyvinyl alcohol film was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 6 times at 50 ° C. to produce a 25 μm-thick polarizer.

  The optical compensation film 101 was alkali-treated with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes and saponified to obtain an alkali-treated film, and the polarizer and KC4UY (Konica Minolta Opto The polarizing plate 1 was produced using a 5% aqueous solution of a completely saponified polyvinyl alcohol as an adhesive. Similarly, the polarizing plate 1 which has the optical compensation films 102-125 and 201-205, respectively was produced.

  Similarly, a third polarizing plate protective film not provided with a saponified rod-like liquid crystal layer, the above-prepared polarizer, and KC4UY (fourth polarizing plate protective film) are laminated in this order to form polarized light on the backlight side. Plate 2 was prepared.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

The pre-bonded polarizing plate of VIERA TH26LX60 manufactured by Matsushita Electric, which is an IPS mode type liquid crystal display device, is peeled off, and the polarizing plate on the viewing side and the backlight side prepared above is applied to the glass surface of the liquid crystal cell in the configuration of FIG. The IPS mode type liquid crystal display devices 101 to 125 and 201 to 205 were prepared by bonding. In addition, the name of each part in FIG. 1 is as follows.
DESCRIPTION OF SYMBOLS 1 1st polarizing plate protective film 2 Polarizer of polarizing plate 1 3 Optical compensation film of this invention (The cellulose-ester film, a rod-shaped liquid crystal layer, and a rod-shaped liquid crystal layer are distribute | arranged to the liquid crystal cell side)
4 Horizontal electric field mode type liquid crystal cell 5 Third polarizing plate protective film 6 Polarizer of polarizing plate 2 7 Fourth polarizing plate protective film a Absorption axis of polarizer of polarizing plate 1 b Slow axis of optical compensation film c Liquid crystal Cell orientation direction d Absorption axis of polarizer of polarizing plate 2 The in-plane slow axis of the optical compensation film of polarizing plate 1 and the orientation direction of the liquid crystal cell were parallel.

<Evaluation of liquid crystal display device>
(Front contrast)
The front contrast of the liquid crystal display device produced as described above was measured by EZ-contrast 160D manufactured by ELDIM. The front contrast was calculated from the ratio of the amount of light in the normal direction to the white and black display cells of the liquid crystal cell.

(Color)
The color measurement at the time of black display was performed with Topcon SR-UL1.

Perform color measurement of the front and oblique inclination angle of 60 ° (azimuth angle of 45 degrees) (front standard), a ^{1/2 ((U'-u ')} 2 + (V'-v') 2) evaluated.

  * In the formula, front: (U ', V'), diagonal: (u ', v'), and all represent CIE1976 chromaticity diagram coordinates.

  The results obtained are shown in Table 6.

  In this measurement, the liquid crystal display devices 101 to 125 of the present invention have a viewing angle (contrast of 100 or more) exceeding 50 degrees, a front contrast exceeding 1000, and a color change being 0.1 or less. It turns out to be superior to the example.

  Further, even when the liquid crystal display device was lit continuously for 1000 hours, the liquid crystal display device of the present invention did not show corner unevenness in which the four corners look white.

  According to the present invention, a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, which reduces a change in tint when the viewing angle is changed, and has excellent wavelength dispersion and a liquid crystal display device using the same Can be provided.

Claims (7)

The first polarizing plate protective film, the polarizer, and the orientation of the rod-like liquid crystal disposed on the surface of the polarizer opposite to the first polarizing plate protective film and oriented vertically on the second polarizing plate protective film A polarizing plate having an optical compensation film provided with a fixed layer, the retardation Ro represented by the following formulas 2 and 3 at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH of the optical compensation film, Rt is
Ro: 30 to 130 nm
Rt: -100 to 65 nm
| Rt | <| Ro / 2 |
The polarizing plate according to claim 1, wherein the optical compensation film has a wavelength dispersion characteristic D (R40) represented by the following formula 1 of 2.0 to 6.5 nm.
Formula 1: D (R40) = R40 (630) -R40 (480)
(In the formula, R40 represents a retardation value measured by tilting the in-plane fast axis in the plane of the optical compensation film by 40 °. (630) and (480) represent respective measurement wavelengths (nm). )
Formula 2: Ro = (nx−ny) × d
Formula 3: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the slow axis direction in the plane of the optical compensation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, and d is the optical index. Represents the thickness (nm) of the compensation film.) The second polarizing plate protective film is an acrylic polymer and a sugar ester compound in which at least one of a pyranose structure or a furanose structure is 1 to 12, and all or part of the OH groups of the structure are esterified, The polarizing plate according to claim 1, which is a cellulose ester film containing at least one compound selected from the group consisting of: The polarizing plate according to claim 2, wherein the cellulose ester film contains the acrylic polymer. The polarizing plate according to claim 2, wherein the cellulose ester film contains the sugar ester compound. The polarizing plate according to claim 2, wherein the cellulose ester film contains the acrylic polymer and the sugar ester compound. The polarizing plate according to claim 2, wherein the cellulose ester film contains the sugar ester compound and the polyester compound. A lateral electric field switching mode type liquid crystal cell, a third polarizing plate protective film, a second polarizer, and a second polarizing plate are disposed on the optical compensation film side of the polarizing plate according to any one of claims 1 to 6. 4 in this order, the in-plane slow axis of the optical compensation film of the polarizing plate and the alignment direction of the liquid crystal cell are parallel or perpendicular, and the third The polarizing plate protective film is Ro: 0-5 nm, Rt: -10-10 nm, The liquid crystal display device characterized by the above-mentioned.