JP2005181952A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which imparts high contrast and high display quality to a liquid crystal display and to provide a liquid crystal display device that has such a polarizing plate. <P>SOLUTION: In the polarizing plate in which protective films are stuck to both sides of a polarizer, at least one of the protective films is a color film in which the B, G, and R transmission density of a status M satisfy the following ranges: 0.02≤B transmission density≤0.4, 0.02≤G transmission density≤0.4, and 0.02≤R transmission density≤0.4. The liquid crystal display device has the polarizing plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polarizing plate and a liquid crystal display device.

The liquid crystal display device is increasingly used year by year as an image display device with small power consumption and a small space. In particular, in recent years, it has been used for televisions, and the demand for image quality has further increased.
As a means for improving the contrast of a liquid crystal display device, improvement of TFT technology, light shielding design, reduction of residual retardation of liquid crystal by using an optical film, and the like have been known so far.
Among them, various methods for reducing the residual retardation by the optical compensation film have been proposed according to the liquid crystal mode, for example, Patent Document 1 for TN mode, Patent Document 2 for IPS mode, and OCB mode. The use is disclosed in Patent Document 3, and the use for VA mode is disclosed in Patent Document 4. This prevented a decrease in contrast due to residual retardation, but these methods still had insufficient improvement effects.
JP-A-6-214116 Japanese Patent Laid-Open No. 10-54982 US Pat. No. 5,805,253 Japanese Patent No. 2866372

  An object of the present invention is to provide a polarizing plate that provides a liquid crystal display device with high contrast and high display quality, and a liquid crystal display device including such a polarizing plate.

As a result of intensive studies, the present inventors have found that the substantial contrast for the viewer of the liquid crystal display device is greatly reduced due to the influence of scattered light having a relatively long optical path length. In other words, the light transmitted through the neighboring white display unit is scattered and partially mixed with the light of the black display unit reaching the viewer. Furthermore, since the scattered light has a long optical path, the present inventors can remove the scattered light without greatly impairing the transmittance of straight light by providing a thin absorption layer between the light source and the viewer. We have found that there is a problem and can solve the problem by the following method.
That is, according to the present invention, a polarizing plate and a liquid crystal display device having the following constitution are provided to achieve the above object of the present invention.
(1) In the polarizing plate in which a protective film is bonded to both sides of a polarizer, at least one of the protective films is a colored film in which the B, G, and R transmission densities of Status M satisfy the following ranges. A polarizing plate.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4
(2) The polarizing film described in (1) above, wherein the colored film is a cellulose acylate film (3) The above (1) or (2), wherein an adhesive layer is provided on the polarizing plate The polarizing plate as described in.
(4) The above (1) to (1), wherein an antiglare layer is provided on the air side protective film.
(3) The polarizing plate in any one.
(5) The polarizing plate as described in any one of (1) to (4) above, which has an antireflection layer.
(6) The polarizing plate according to any one of (1) to (5) above, comprising a retardation layer.
(7) The polarizing plate according to any one of (1) to (6) above, which has a viewing angle compensation layer.
(8) The polarizing plate as described in any one of (1) to (7) above, which has a brightness enhancement layer.
(9) In a liquid crystal display device having a liquid crystal display element and a polarizing plate in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film, the transmission density of B, G, and R of status M is in the following range A liquid crystal display device comprising at least one colored film satisfying the above.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4
(10) A liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film, a pair of polarizing plates that sandwich both ends of the liquid crystal display element, and a backlight unit are provided. In liquid crystal display devices,
A liquid crystal display device comprising at least one colored film having a B, G, R transmission density of Status M satisfying the following range between a backlight unit and an observer.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4
(11) The liquid crystal display device according to (9) or (10), wherein the liquid crystal display device has at least one polarizing plate according to any one of (1) to (8).
(12) The liquid crystal display device according to (11), wherein the liquid crystal mode is any one of a TN mode, an OCB mode, an IPS mode, and a VA mode.
(13) The liquid crystal display device according to any one of (9) to (12), wherein the screen size is 15 inches or more.

  The liquid crystal display device including the polarizing plate having the optical compensation function of the present invention can obtain an image with high contrast and high display quality. The polarizing plate includes a TN (Twisted Nematic) type, an OCB (Optically Compensated Bend) type, an ECB (Electrically Controlled Birefringence) type, a VA (Vertically Aligned In) type, a IPS (Vertical Aligned In) type, an IPS type PS Can be used.

The liquid crystal display device of the present invention includes a liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film, and a polarizing plate. The colored film contains at least one colored film satisfying the following range.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4

Preferably, the transmission density of the colored film satisfies the following range.
0.03 ≦ B transmission concentration ≦ 0.3
0.03 ≦ G transmission density ≦ 0.3
0.03 ≦ R transmission density ≦ 0.3

The transmission density of the film can be measured with a densitometer X-Rite 310 manufactured by X Light.
The colored film is preferably at least one of protective films bonded to both sides of a polarizer bonded to a liquid crystal display element. Moreover, it is preferable to arrange | position a colored film in the position where the refractive index difference with an adjacent layer becomes large.
Accordingly, the polarizing plate of the present invention is a polarizing plate in which a protective film is bonded to both sides of the polarizer, and the transmission density of B, G, R of status M of at least one piece of the protective film satisfies the above range. .
When the transmission density exceeds 0.4, the white luminance decreases, and when it is less than 0.02, the contrast improvement effect becomes insufficient.

  The member that absorbs the entire visible light region can be provided in any part of the polarizing plate, but a dye or pigment can be added to the polarizing plate protective film to form the colored film, and this function can be provided. preferable.

  As the polarizing plate protective film, a cellulose acylate film is preferable. The cellulose acylate film of the present invention can adjust the absorbance of the film by adding an appropriate amount of yellow, magenta, cyan dye or pigment.

First, the dye preferably used in the present invention will be described.
As the cyan blue dye, a blue dye that can be dissolved in a dope solvent such as an anthraquinone dye, an azo dye, a triphenylmethane dye, or a quinoneimine dye can be used. In particular, anthraquinone dyes are preferred because of their good compatibility with cellulose esters.

  The anthraquinone dye can be substituted with an arbitrary substituent at positions 1 to 8 of anthraquinone. As a preferred substituent, an optionally substituted phenyl group, phenylamino group, hydroxy group, nitro group, amino group or hydrogen atom is represented. (These substituents are represented by R, and R positions are represented by R1 to R8 in correspondence with the accompanying characters.) At least one of R1 to R8 is preferably an optionally substituted phenylamino group.

  The substituent on the phenylamino group is represented by f, and is represented by f1 to f5 corresponding to the positions from the 1st position to the 5th position on the phenyl group. Examples of f1, f2, f3, f4, and f5 include a hydrogen atom, a halogen atom, an alkoxy group, an alkyl group, an allyloxy group, a hydroxyalkyl group, and a cyclohexylsulfonamide group. These may be further substituted.

Specific examples of the anthraquinone dyes are given below, but the present invention is not limited thereto.
Specific compounds
(1) 1,4-diphenylaminoanthraquinone (2) 1,4-di (2,4,6-trimethylphenyl) anthraquinone (3) 1,4-di (2,4-diethyl-4-methylphenyl) anthraquinone (4) 1,4-di (2,4,6-trimethyl-4-cyclohexylsulfonamidophenyl) anthraquinone (5) 1-methoxyphenylamino-4-hydroxy-5-methoxyphenylamino-8-hydroxyanthraquinone (6 ) 1,4-di (2,4,6-tripropylcyclohexylsulfonamidophenyl) anthraquinone (7) 1-ethoxyphenylamino-4-hydroxy-5-methoxyphenylamino-8-hydroxyanthraquinone (8) 1,4 -Di (2,4,6-trimethoxyphenylamino) anthraquinone (9) 1,4 Di (2,4,6-triethylphenyl) anthraquinone (10) 1,4-di (2,4-diisopropoxy-4-methylphenyl) anthraquinone (11) 1,4-di (2,4,6- Trichloro-4-cyclohexylsulfonamidophenyl) anthraquinone (12) 1- (2,4,6-trimethoxyphenylamino) -4-hydroxy-5- (2,4,6-trimethoxyphenylamino) -8-hydroxy Anthraquinone (13) 1,4-di (2,4,6-tripropylcyclohexylsulfonamidophenyl) anthraquinone (14) 1,5-dimethoxyphenylamino-4,8-dihydroxyanthraquinone (15) 1-methylamino-4 -(4-Methylphenylamino) anthraquinone

Moreover, as a cyan dye, the compound represented, for example by the following general formula (I) can be used.
Formula (I)

In the formula, Y represents a group necessary for forming a heterocyclic ring, L ¹ , L ² , L ³ , L ⁴ and L ⁵ each represents a methine group, and n represents 0 or 1.

  Specific examples of the dye represented by formula (I) are shown below, but the present invention is not limited thereto.

  Next, specific examples of the magenta dye and yellow dye used in the present invention will be shown, but the present invention is not limited thereto.

The addition amount of the dye of the present invention added to the cellulose acylate film is preferably 0.01 mg / m ² or more and 300 mg / m ² or less, more preferably 0.1 mg / m ² or more and 200 mg / m ² or less, and 5 mg / m ² or more and 100 mg / m ² or less is most preferable.

Next, the pigment added to the cellulose acylate film of the present invention will be described in detail.
As the pigment, either an inorganic pigment or an organic pigment can be preferably used. Examples thereof are described in, for example, Color Material Engineering Handbook and Asakura Shoten. The addition amount of the pigment of the present invention is preferably 0.01 mg / m ² or more and 300 mg / m ² or less, more preferably 0.1 mg / m ² or more and 200 mg / m ² or less, and 0.5 mg / m ² or more and 100 mg / m ^2. The following are most preferred.
The primary particle diameter of the pigment is preferably 0.01 μm or more and 1 μm or less, and more preferably 0.02 μm or more and 0.3 μm or less. By appropriately controlling the particle size of the pigment, scattered light can be effectively blocked.
In addition, water-soluble inks described in JP-A No. 2003-306623 can also be preferably used.
The dyes and pigments of the present invention can be added by various methods, but are preferably added to the dope (cellulose acylate solution) before casting.

[Production of cellulose acylate and cellulose acylate film]
The acyl group of the cellulose acylate film is not particularly limited, but an acetyl group, a propionyl group, or a butyryl group is preferably used, and an acetyl group is particularly preferable. The degree of substitution of all acyl groups is preferably 2.7 to 3.0, more preferably 2.8 to 2.95. When cellulose acetate in which all acyl groups are acetyl groups is used, the degree of acetyl substitution is preferably 2.7 to 2.95, more preferably 2.8 to 2.95, and most preferably 2.84 to 2.89. . Also, the degree of acetyl substitution described in JP-A No. 13-356214 is 2.50 or more and 2.86 or less, and 2.75 or more and 2.86 or less of acetyl described in JP-A No. 13-226495. The degree of substitution can also be preferably used. If the substitution degree of all acyl groups is too low, there is a problem that Re is likely to be larger than a desired value due to the conveyance tension at the time of casting, and in-plane variation is likely to occur. Further, the substitution degree of the acyl group at the 6-position is preferably 0.9 or more. When the degree of substitution is 0.9 or less, variations in Re and Rth tend to occur. In addition, the value computed according to ASTM D817 is employ | adopted for the substitution degree of the acyl group in this patent.
In the present invention, it is preferable to use cellulose acetate having an acetylation degree in the range of 59.0 to 62.5%.
The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).
The viscosity average degree of polymerization (DP) of cellulose acylate is preferably 250 or more, and more preferably 290 or more.
In addition, the cellulose acylate used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably in the range of 1.0 to 1.7, more preferably in the range of 1.3 to 1.65, and in the range of 1.4 to 1.6. Most preferably.
As cellulose acetate of the present invention, Synthesis Example 1 described in paragraph Nos. 0043 to 0044 of JP-A No. 11-5851, Synthesis Example 2 described in paragraph Nos. 0048 to 0049, and The cellulose acetate obtained by the synthesis method of Synthesis Example 3 described can be used.

[Manufacture of cellulose acylate film]
The cellulose acylate film of the present invention is produced by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more kinds of functional groups, the number of carbon atoms is preferably within the above-described preferable range of carbon atoms of the solvent having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is 40 to 60 mol%, and most preferably. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

A cellulose acylate solution can be prepared by a general method comprising processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.
The amount of cellulose acylate is adjusted so that it is contained in an amount of 10 to 40% by mass in the resulting solution. The amount of cellulose acylate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring cellulose acylate and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, the cellulose acylate and the organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil.
The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., more preferably 80 to 110 ° C.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, cellulose acylate can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose acylate with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.
In the cooling dissolution method, first, cellulose acylate is gradually added to an organic solvent at room temperature while stirring.
The amount of cellulose acylate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of cellulose acylate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The mixture of cellulose acylate and organic solvent is solidified by cooling.
The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached.

Furthermore, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), cellulose acylate is dissolved in the organic solvent. The temperature may be increased by simply leaving it at room temperature or in a warm bath.
The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. .
A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, if the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
In addition, according to the measurement by a differential scanning calorimeter (DSC), the 20 mass% solution which melt | dissolved cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by the cooling dissolution method is. In the vicinity of 33 ° C., there exists a quasi-phase transition point between a sol state and a gel state, and a uniform gel state is obtained below this temperature. Therefore, it is necessary to keep this solution at a temperature equal to or higher than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

From the prepared cellulose acylate solution (dope), a cellulose acylate film is produced by a solvent cast method. It is preferable to add the above-mentioned retardation increasing agent to the dope.
The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  Drying can be performed by blowing an inert gas for a time other than drying without wind in drying before peeling. The air temperature at this time is preferably 0 ° C to 180 ° C, more preferably 40 ° C to 150 ° C.

Regarding the drying method in the solvent casting method, U.S. Pat. Nos. 45-4554, 49-5614, JP-A-60-176834, JP-A-60-203430, and JP-A-62-115035. Drying on the band or drum can be performed by blowing an inert gas such as air or nitrogen.

  The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in JP-B-5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  Using the prepared cellulose acylate solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to produce a cellulose acylate film by a solvent cast method. The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.

  When casting a plurality of cellulose acylate solutions of two or more layers, it is possible to cast a plurality of cellulose acylate solutions, from a plurality of casting openings provided at intervals in the direction of travel of the support. The film may be produced while casting and laminating solutions containing cellulose acylate. For example, the methods described in JP-A Nos. 61-158414, 1-122419, and 11-198285 can be used. The film can also be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-134933. The method described in each publication can be used. Further, a cellulose acylate film is disclosed in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution, and the high- and low-viscosity cellulose acylate solution is simultaneously extruded. A casting method can also be used.

Also, using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side that is in contact with the support surface to produce the film. You can also For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned.
As the cellulose acylate solution to be cast, the same solution may be used, or different cellulose acylate solutions may be used. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Furthermore, the cellulose acylate solution of the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

  In the conventional single-layer solution, it is necessary to extrude a cellulose acylate solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In such a case, the stability of the cellulose acylate solution is poor and solid matter is generated, which often causes problems due to defects or poor flatness. As a solution to this problem, by casting a plurality of cellulose acylate solutions from the casting port, it is possible to simultaneously extrude a highly viscous solution onto the support, improving the flatness and providing an excellent planar film. Not only can be produced, but also the use of a concentrated cellulose acylate solution can reduce the drying load and increase the production speed of the film.

In order to improve the mechanical properties of the cellulose acylate film, the following plasticizers can be used. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
The addition amount of the plasticizer is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass of the amount of cellulose acylate.

  A degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the cellulose acylate film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by mass, bleeding-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

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

[Surface treatment of cellulose acylate film]
The cellulose acylate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. It is also preferable to provide an undercoat layer as described in JP-A-7-333433.
From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acylate film in these treatments is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.
When used as a protective film for a polarizing plate, it is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment for cellulose acylate, from the viewpoint of adhesiveness with a polarizer.
The surface energy is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less.

Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment of the cellulose acylate film is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried.
Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 mol / L, and preferably 0.5 to 2.0. More preferably, it is in the range of mol / L. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, and more preferably in the range of 40 to 70 ° C.

The surface energy of a solid can be determined by a contact angle method, a wet heat method, and an adsorption method as described in “Basics and Applications of Wetting” (issued by Realize 1989.12.10). In the case of the cellulose acylate film of the present invention, the contact angle method is preferably used.
Specifically, two types of solutions having known surface energies are dropped on a cellulose acylate film, and at the intersection of the surface of the droplet and the surface of the film, the angle formed by the tangent line drawn on the droplet and the surface of the film, The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

[Moisture permeability]
The moisture permeability is calculated as the amount of moisture (g) that evaporates in 24 hours per 1 m ^{2 of} area by measuring the moisture permeability of each sample in accordance with the method described in JIS Z 0208.
The moisture permeability of the cellulose acylate film can be adjusted by various methods.
The moisture permeability can be reduced by adding a hydrophobic compound to the cellulose acylate film and reducing the water absorption rate of the cellulose acylate film. In this case, an additive having a low compatibility with cellulose acylate and a small plasticizing effect is particularly preferable.
The water absorption rate of the cellulose acylate film can be evaluated by measuring the equilibrium water content at a constant temperature and humidity. The equilibrium moisture content at 25 ° C. and 80% RH of the cellulose acylate film is preferably 5% by mass or less, and more preferably 3% by mass or less. The equilibrium moisture content is calculated by measuring the moisture content of the sample that has reached equilibrium after being left at the temperature and humidity for 24 hours by the Karl Fischer method and dividing the moisture content (g) by the sample mass (g). .

The moisture permeability can also be lowered by stretching in the transport direction or the width direction during film formation, or by stretching in both directions to make the orientation of molecular chains of cellulose acylate dense.
Stretching can be uniaxial stretching or biaxial stretching.
Biaxial stretching includes simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of continuous production, and after casting the dope, the film is peeled off from the band or drum, After stretching in the width direction (longitudinal method), the film is stretched in the longitudinal direction (width direction).
Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, JP-A-4-298310, and JP-A-11-48271. Yes. The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying the film while holding it with a tenter and gradually widening the width of the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine). The stretch ratio of the film (the ratio of the increase due to stretching relative to the original length) is preferably in the range of 2 to 50%, more preferably in the range of 10 to 40%, and in the range of 15 to 35%. Most preferably.

[Hygroscopic expansion coefficient]
The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature.
In order to prevent frame-like transmittance increase, the hygroscopic expansion coefficient of the cellulose acylate film is preferably 30 × 10 ⁻⁵ /% RH or less, and preferably 15 × 10 ⁻⁵ /% RH or less. More preferably, it is most preferably 10 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably small, but usually it is 1.0 × 10 ⁻⁵ /% RH or more.
The method for measuring the hygroscopic expansion coefficient is shown below.
A sample having a width of 5 mm and a length of 20 mm is cut out from the produced cellulose acylate film (retardation plate), and one end is fixed and hung in an atmosphere of 25 ° C. and 20% RH (R0). A weight of 0.5 g is hung on the other end and left for 10 minutes to measure the length (L0). Next, with the temperature kept at 25 ° C., the humidity is set to 80% RH (R1), and the length (L1) is measured. The hygroscopic expansion coefficient is calculated by the following formula. The measurement is carried out 10 times for the same sample, and the average value is adopted.
Hygroscopic expansion coefficient [/% RH] = {(L1-L0) / L0} / (R1-R0)

In order to reduce the dimensional change due to moisture absorption, it is preferable to reduce the amount of residual solvent during film formation and to reduce the free volume in the polymer film.
A general method for reducing the residual solvent is to dry at a high temperature for a long time. However, if the time is too long, the productivity is naturally lowered. Accordingly, the amount of the residual solvent relative to the cellulose acylate film is preferably in the range of 0.01 to 1% by mass, more preferably in the range of 0.02 to 0.07% by mass, and 0.03 to 0%. The most preferable range is 0.05 mass%.
By controlling the amount of the residual solvent, a polarizing plate having optical compensation ability can be produced at low cost with high productivity.

The amount of residual solvent was measured using a gas chromatograph (GC18A, manufactured by Shimadzu Corporation) after dissolving a certain amount of sample in chloroform.
In the solution casting method, a film is produced using a solution (dope) obtained by dissolving a polymer material in an organic solvent. As will be described later, drying by the solution casting method is largely divided into drying on the drum (or band) surface and drying during film conveyance. When drying on the drum (or band) surface, it is preferable to dry slowly at a temperature that does not exceed the boiling point of the solvent being used (when the boiling point is exceeded, bubbles are formed). Further, it is preferable that the drying during film transportation is performed at a glass transition point of the polymer material ± 30 ° C., more preferably ± 20 ° C.

Moreover, it is preferable to add the compound which has a hydrophobic group as another method of making the dimensional change by the said moisture absorption small. The material having a hydrophobic group is not particularly limited as long as the material has a hydrophobic group such as an alkyl group or a phenyl group in the molecule. In particular, the corresponding material is preferably used. Examples of these preferable materials include triphenyl phosphate (TPP) and tribenzylamine (TBA).
The addition amount of the compound having a hydrophobic group is preferably in the range of 0.01 to 30% by mass, more preferably in the range of 0.1 to 20% by mass with respect to the solution (dope) to be adjusted. preferable.

[Film retardation]
The Re retardation value and Rth retardation value of the film are defined by the following formulas (I) and (II), respectively.
Formula (I): Re = (nx−ny) × d
Formula (II): Rth = {(nx + ny) / 2−nz} × d
In the above formulas (I) and (II), nx is the refractive index in the slow axis direction (direction in which the refractive index becomes maximum) in the film plane. ny is the refractive index in the fast axis direction (the direction in which the refractive index is minimum) in the film plane. nz is the refractive index in the thickness direction of the film. d is the thickness of the film whose unit is nm.

The cellulose acylate film of the present invention can be preferably used as a retardation film corresponding to various liquid crystal modes.
The preferred optical properties of the cellulose acylate film vary depending on the liquid crystal mode.
For the OCB mode, Re is preferably 10 to 100, more preferably 20 to 70. Rth is preferably from 50 to 300, more preferably from 100 to 250.
For the VA mode, Re is preferably 20 to 100, more preferably 30 to 70. Rth is preferably 50 to 250, more preferably 80 to 180.
For TN, Re is preferably 0-50, more preferably 2-30. Rth is preferably 10-200, more preferably 30-150.
In the OCB mode and the TN mode, an optically anisotropic layer can be applied on the cellulose acylate film having the retardation value and used as an optical compensation film.

In addition, it is preferable that the birefringence ((DELTA) n: nx-ny) of a cellulose acylate film exists in the range of 0.00 thru | or 0.002 micrometer. The birefringence {(nx + ny) / 2-nz} in the thickness direction of the support film and the opposing film is preferably in the range of 0.00 to 0.04.
The thickness (dry film thickness) of the cellulose acylate film is 120 μm or less, preferably 20 to 110 μm, more preferably 40 to 100 μm.

[Photoelasticity]
The photoelastic coefficient of the protective film of the present invention is preferably 60 × 10 ⁻⁸ cm ² / N or less, and more preferably 20 × 10 ⁻⁸ cm ² / N or less. The photoelastic coefficient can be determined by an ellipsometer.

[Glass-transition temperature]
The glass transition temperature of the protective film of the present invention is preferably 120 ° C. or higher, and more preferably 140 ° C. or higher. The glass transition temperature is a temperature at which the baseline derived from the glass transition of the film begins to change and a temperature at which the glass returns to the baseline again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). Is obtained as an average value of.

Next, the polarizing plate of the present invention will be described.
1. First, the protective film and the polarizer constituting the polarizing plate of the present invention will be described.
In addition to the polarizer and the protective film, the polarizing plate of the present invention may have an adhesive layer (sometimes referred to as an adhesive layer) and a separate film as constituent elements.

(1) Protective film The polarizing plate of the present invention has a total of two protective films, one on each side of the polarizer, and at least one of them preferably has a function as a retardation film.
The protective film of the present invention is preferably a polymer film produced from norbornene resin, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyarylate, polysulfone, cellulose acylate and the like.
Of these, a polymer film produced from the cellulose acylate is most preferred.

(2) Polarizer The polarizer of the present invention is preferably composed of polyvinyl alcohol (PVA) and a dichroic molecule. However, as described in JP-A-11-248937, PVA or polyvinyl chloride is used. A polyvinylene polarizer in which a polyene structure is produced by dehydration and dechlorination and oriented is also usable.

  PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.

The saponification degree of PVA is not particularly limited, but is preferably 80 to 100 mol%, particularly preferably 90 to 100 mol% from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494 is also preferably used. it can.
After PVA is formed into a film, it is preferable to introduce a dichroic molecule to constitute a polarizer. As a method for producing a PVA film, a method of forming a film by casting a stock solution obtained by dissolving a PVA resin in water or an organic solvent is generally preferably used. The density | concentration of the polyvinyl alcohol-type resin in a stock solution is 5-20 mass% normally, and a PVA film with a film thickness of 10-200 micrometers can be manufactured by forming this stock solution with a casting method. The PVA film can be produced with reference to Japanese Patent No. 3342516, Japanese Patent Application Laid-Open No. 09-328593, Japanese Patent Application Laid-Open No. 13-302817, and Japanese Patent Application Laid-Open No. 14-144401.

The crystallinity of the PVA film is not particularly limited. However, in order to reduce the average crystallinity (Xc) of 50 to 75% by mass described in Japanese Patent No. 3251073 and the in-plane hue variation, Japanese Patent Application Laid-Open No. Hei 14- PVA films having a crystallinity of 38% or less described in No. 236214 can be used.
The birefringence (Δn) of the PVA film is preferably small, and a PVA film having a birefringence of 1.0 × 10 ⁻³ or less described in Japanese Patent No. 3342516 can be preferably used. However, as described in JP-A-14-228835, in order to obtain a high degree of polarization while avoiding cutting during stretching of the PVA film, the birefringence of the PVA film may be set to 0.02 or more and 0.01 or less. Alternatively, as described in JP-A-14-060505, the value of (nx + ny) / 2-nz may be set to 0.0003 or more and 0.01 or less. The retardation (in-plane) of the PVA film is preferably from 0 nm to 100 nm, and more preferably from 0 nm to 50 nm. Moreover, 0 nm or more and 500 nm or less are preferable, and, as for Rth (film thickness direction) of a PVA film, 0 nm or more and 300 nm or less are more preferable.

In addition, the polarizing plate of the present invention includes a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less as described in Japanese Patent No. 3021494, and 5 μm or more as described in JP-A No. 13-316492. A PVA film having 500 or less optical foreign matter per 100 cm ² , a PVA film having a hot-water cutting temperature spot in the TD direction of 1.5 ° C. or less of the film described in JP-A No. 14-030163, and glycerin A PVA film formed from a solution containing 1 to 100 parts by mass of a trivalent to hexavalent polyhydric alcohol such as, or a mixture of 15% by mass or more of a plasticizer described in JP-A-06-289225. It can be preferably used.

  Although the film thickness before extending | stretching of a PVA film is not specifically limited, 1 micrometer-1 mm are preferable and 20-200 micrometers is especially preferable from a viewpoint of stability of film holding | maintenance and the uniformity of extending | stretching. As described in JP-A No. 14-236212, a thin PVA film may be used in which the stress generated when stretching 4 to 6 times in water is 10 N or less.

The dichroic molecules, I ₃ ^- and I ₅ ^- can be preferably used an iodine ion or a dichroic dye higher such. In the present invention, higher-order iodine ions are particularly preferably used. Higher-order iodine ions were obtained by dissolving iodine in an aqueous potassium iodide solution as described in “Applications of Polarizing Plate” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p39-p45. PVA can be immersed in a liquid and / or boric acid aqueous solution, and can be produced in a state of being adsorbed and oriented in PVA.
When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and a bisazo dye and a trisazo dye are particularly preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt.

Specific examples of such dichroic dyes include, for example, CIDirect Red 37, Congo Red (CI Direct Red 28), CIDirect Violet 12, CIDirect Blue 90, CIDirect Blue 22, CIDirect Blue 1, CIDirect Blue 151, CIDirect Green 1st benzidine series, CIDirect Yellow 44, CIDirect Red 23, CIDirect Red 79 etc. diphenylurea series, CIDirect Yellow 12 etc. stilbene series, CIDirect Red 31 etc. dinaphthylamine series, CIDirect Red 81, CIDirect Violet 9, CIDirect Blue 78 And the like can be mentioned.
In addition, CIDirect Yellow 8, CIDirect Yellow 28, CIDirect Yellow 86, CIDirect Yellow 87, CIDirect Yellow 142, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 72, CIDirect Orange 106, CIDirect Orange 107, CIDirect Red 2, CIDirect Red 39, CIDirect Red 83, CIDirect Red 89, CIDirect Red 240, CIDirect Red 242, CIDirect Red 247, CIDirect Violet 48, CIDirect Violet 51, CIDirect Violet 98, CIDirect Blue 15, CIDirect Blue 67, CIDirect Blue 71, CIDirectBlue 98, CIDirect Blue 168, CIDirect Blue 202, CIDirect Blue 236, CIDirect Blue 249, CIDirect Blue 270, CIDirect Green 59, CIDirect Green 85, CIDirect Brown 44, CIDirect Brown 106, CIDirect Brown 195, CIDirect Brown 210, CIDirect Brown 223, CIDirect Brown 224, CIDirect Black 1, CIDirect Black 17, CIDirect Black 19, CIDirect Black 54, etc. are further disclosed in JP-A-62-270802, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105. And dichroic dyes described in JP-A-1-265205 and JP-A-7-261024 can be preferably used. In order to produce dichroic molecules having various hues, two or more of these dichroic dyes may be blended. When a dichroic dye is used, the adsorption thickness may be 4 μm or more as described in JP-A No. 14-082222.

If the content of the dichroic molecule in the film is too small, the degree of polarization is low, and if it is too large, the single-plate transmittance is lowered. Therefore, the polyvinyl alcohol polymer constituting the film matrix is usually used. On the other hand, it is adjusted in the range of 0.01% by mass to 5% by mass.
A preferable film thickness of the polarizer is preferably 5 μm to 40 μm, and more preferably 10 μm to 30 μm. The ratio between the thickness of the polarizer and the thickness of the protective film described later is 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0.16 described in JP-A No. 14-174727. A range is also preferable.
The crossing angle between the slow axis of the protective film and the absorption axis of the polarizer may be any value, but is preferably parallel or an azimuth angle of 45 ± 20 °.

2. Next, the manufacturing process of the polarizing plate of the present invention will be described.
The production process of the polarizing plate in the present invention is preferably composed of a swelling process, a dyeing process, a hardening process, a stretching process, a drying process, a protective film bonding process, and a post-bonding drying process. The order of the dyeing step, the hardening step, and the stretching step may be arbitrarily changed, or several steps may be combined and performed simultaneously. Further, as described in Japanese Patent No. 3331615, washing with water after the hardening step can be preferably performed.

  In the present invention, it is particularly preferable to sequentially perform the swelling process, the dyeing process, the hardening process, the stretching process, the drying process, the protective film bonding process, and the drying process after bonding in the order described. An on-line surface inspection step may be provided during or after the above-described steps.

The swelling step is preferably performed only with water, but as described in JP-A-10-153709, for the purpose of stabilizing optical performance and avoiding wrinkling of the polarizing plate substrate in the production line. It is also possible to manage the degree of swelling of the polarizing plate substrate by swelling the polarizing plate substrate with an aqueous boric acid solution.
Moreover, although the temperature and time of a swelling process can be defined arbitrarily, 10 to 60 degreeC and 5 to 2000 second are preferable.

  For the dyeing step, the method described in JP-A-2002-86554 can be used. Further, as a dyeing method, not only immersion but any means such as application or spraying of iodine or a dye solution can be used. Further, as described in JP-A-2001-290025, a method of dyeing while stirring the concentration of iodine, the dyeing bath temperature, the draw ratio in the bath, and the bath liquid in the bath may be used.

When higher-order iodine ions are used as the dichroic molecule, in order to obtain a high-contrast polarizing plate, it is preferable to use a solution obtained by dissolving iodine in an aqueous potassium iodide solution in the dyeing step. In this case, iodine in the iodine-potassium iodide aqueous solution is preferably 0.05 to 20 g / L, potassium iodide is 3 to 200 g / L, and the mass ratio of iodine and potassium iodide is preferably 1 to 2000. The dyeing time is preferably 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, iodine is 0.5-2 g / L, potassium iodide is 30-120 g / L, mass ratio of iodine and potassium iodide is 30-120, dyeing time is 30-600 seconds, and liquid temperature is 20-50 degreeC is good.
Further, as described in Japanese Patent No. 3145747, boron compounds such as boric acid and borax may be added to the dyeing solution.

In the hardening step, it is preferable to immerse in the crosslinking agent solution or apply the solution to contain the crosslinking agent. Further, as described in JP-A-11-52130, the hardening process can be performed in several steps.
As the cross-linking agent, those described in US Reissue Patent No. 232897 can be used, and as described in Japanese Patent No. 3357109, a polyvalent aldehyde is used as the cross-linking agent in order to improve dimensional stability. However, boric acids are most preferably used.
When boric acid is used as a crosslinking agent used in the hardening step, metal ions may be added to the boric acid-potassium iodide aqueous solution. Zinc chloride is preferable as the metal ion. However, as described in JP-A No. 2000-35512, zinc halide such as zinc iodide, zinc sulfate such as zinc acetate is used instead of zinc chloride. It can also be used.

In the present invention, it is preferable to prepare a boric acid-potassium iodide aqueous solution to which zinc chloride has been added, and perform dura- tion by immersing the PVA film. Boric acid is preferably 1-100 g / L, potassium iodide is 1-120 g / L, zinc chloride is 0.01-10 g / L, hardening time is preferably 10-1200 seconds, and liquid temperature is preferably 10-60 ° C. . More preferably, boric acid is 10 to 80 g / L, potassium iodide is 5 to 100 g / L, zinc chloride is 0.02 to 8 g / L, hardening time is 30 to 600 seconds, and liquid temperature is 20 to 20 g / L. 50 ° C is preferable.
For the stretching step, it is preferable to use a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515 or the like, or a tenter method as described in JP-A-2002-86554. it can. A preferable draw ratio is 2 times or more and 12 times or less, more preferably 3 times or more and 10 times or less. Moreover, the relationship between the draw ratio, the thickness of the original fabric and the thickness of the polarizer is described in JP-A-2002-040256 (polarizer film thickness / raw film thickness after bonding of the protective film) × (total draw ratio) )> 0.17 or the relationship between the width of the polarizer when leaving the final bath and the width of the polarizer when bonding the protective film is 0.80 ≦ (protective film) described in JP-A-2002-040247 The width of the polarizer at the time of bonding / the width of the polarizer at the time of leaving the final bath) ≦ 0.95 can also be preferably set.

  As the drying step, a method known in JP-A-2002-86554 can be used, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. Further, as described in Japanese Patent No. 3148513, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or as described in Japanese Patent Application Laid-Open Nos. 07-325215 and 07-325218. Aging in an atmosphere controlled in temperature and humidity is also preferable.

The protective film laminating step is a step of laminating both surfaces of the above-described polarizer that has gone through the drying step with two protective films. A method of bonding with a pair of rolls is preferably used so that the adhesive liquid is supplied immediately before bonding and the polarizer and the protective film are overlapped. Further, as described in JP-A-2001-296426 and JP-A-2002-86554, in order to suppress the groove-like unevenness of the record due to the stretching of the polarizer, It is preferable to adjust the moisture content. In the present invention, a moisture content of 0.1% to 30% is preferably used.
The adhesive between the polarizer and the protective film is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 5 μm after drying, and particularly preferably 0.05 to 3 μm.
Moreover, in order to improve the adhesive force of a polarizer and a protective film, it is preferable to perform adhesion after surface-treating the protective film to make it hydrophilic. The surface treatment method is not particularly limited, and a known method such as a saponification method using an alkaline solution or a corona treatment method can be used. Further, an easy-adhesion layer such as a gelatin undercoat layer may be provided after the surface treatment. As described in JP-A-14-267839, the contact angle of the protective film surface with water is preferably 50 ° or less.

  The drying conditions after bonding are in accordance with the method described in JP-A-2002-86554, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. It is also preferable to perform aging in an atmosphere with temperature and humidity control as described in JP-A-07-325220.

The element content in the polarizer is as follows: iodine 0.1-3.0 g / m ² , boron 0.1-5.0 g / m ² , potassium 0.1-2.0 g / m ² , zinc 0-2. It is preferably 0 g / m ² .
Further, the potassium content may be 0.2% by mass or less as described in JP-A No. 2001-166143, and the zinc content in the polarizer is described in JP-A No. 2000-035512. It is good also as 0.04 mass%-0.5 mass%.

  As described in Japanese Patent No. 3323255, in order to increase the dimensional stability of the polarizing plate, an organic titanium compound and / or an organic zirconium compound is added and used in any of the dyeing process, stretching process and hardening process And at least 1 type of compound chosen from the organic titanium compound and the organic zirconium compound can also be contained. A dichroic dye may be added to adjust the hue of the polarizing plate.

Next, the adhesive used for the adhesive layer of this invention is demonstrated.
As the pressure-sensitive adhesive, a pressure-sensitive adhesive using a base polymer such as acrylic acid, methacrylic acid, butyl rubber, or silicone can be used. Although not particularly limited, (meth) acrylate base polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and (meth) acrylate-2-ethylhexyl Alternatively, a copolymer base polymer using two or more of these (meth) acrylic acid esters is preferably used. In the pressure-sensitive adhesive, a polar monomer is usually copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylamide, and N, N-dimethylaminoethyl (meth). Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as acrylate and glycidyl (meth) acrylate.

  The pressure-sensitive adhesive usually contains a crosslinking agent. Crosslinking agents include those that generate divalent or polyvalent metal ions and carboxylate metal salts, those that form amide bonds with polyamine compounds, those that form ester bonds with polyepoxy compounds and polyols, polyisocyanate compounds and amides. Examples of these compounds include one that forms a bond, and these compounds are used as a cross-linking agent in one or more kinds and mixed with a base polymer.

  The thickness of the pressure-sensitive adhesive layer of the present invention is preferably 2 to 50 μm. It is a normal form that a separate film is bonded to the surface of the pressure-sensitive adhesive layer opposite to the polarizing plate in order to protect the pressure-sensitive adhesive layer. As the separate film, a polyester film that has been subjected to a release treatment with a silicone resin or the like is used. This separate film is peeled and removed at the time of bonding with a liquid crystal cell or another optical functional film.

As an index representing the softness of the pressure-sensitive adhesive, a relaxation elastic modulus and the like can be used.
The relaxation elastic modulus will be described. In general, when a strain γ0 is momentarily applied to a viscoelastic body and then kept constant, the stress σ (t) decreases with the passage of time t and approaches a constant value, which is called stress relaxation. At this time, the stress σ (t) that relaxes with the passage of time t can be expressed as σ (t) = G (t) · γ0. G (t) is an elastic modulus depending on time t, and this is called relaxation elastic modulus. Since this equation can be rewritten as G (t) = σ (t) / γ0, the relaxation modulus G (t) is the stress σ (t) that decreases with time t and the constant strain γ0 applied from the outside. Is the ratio.

Thus, although the relaxation elastic modulus G (t) is a function of the time t, the relaxation elastic modulus G (100) after 100 seconds is in the range of 3 × 10 ^{5 to} 5 × 10 ⁶ dyn / cm ² . If there is, it is good from the viewpoint of eliminating white spots, but if it is a relatively low value within this range, it is inferior in terms of adhesive residue and reworkability. Therefore, the relaxation elastic modulus G (100) after 100 seconds is preferably in the range of 6 × 10 ^{5 to} 5 × 10 ⁶ dyn / cm ^{2 from} the viewpoint of adhesive residue and reworkability. More preferably, it is in the range of 0.5 × 10 ^{5 to} 5 × 10 ⁶ dyn / cm ² .

3. Characteristics of polarizing plate (1) Transmittance and degree of polarization The preferred single plate transmittance of the polarizing plate of the present invention is 42.5% or more and 49.5% or less, more preferably 42.8% or more and 49.0%. It is as follows. A preferable range of the degree of polarization defined by the following formula 4 is 99.900% or more and 99.999% or less, and more preferably 99.940% or more and 99.995% or less. A preferable range of the parallel transmittance is 36% or more and 42% or less, and a preferable range of the orthogonal transmittance is 0.001% or more and 0.05% or less. A preferable range of the dichroic ratio defined by Formula 5 is 48 or more and 1215 or less, and more preferably 53 or more and 525 or less.
The above-described transmittance is defined by Equation 2 based on JIS Z 8701.

Formula 2

  Here, K, S (λ), y (λ), and τ (λ) are as follows.

Formula 3

S (λ): spectral distribution of standard light used for color display y (λ): color matching function in XYZ system τ (λ): spectral transmittance

Formula 4

Formula 5

The iodine concentration and the single plate transmittance may be within the ranges described in JP-A-2002-258051.
The parallel transmittance may be small in wavelength dependency as described in Japanese Patent Application Laid-Open No. 2001-083328 and Japanese Patent Application Laid-Open No. 2002-022950. The optical characteristics when the polarizing plates are arranged in crossed Nicols may be in the range described in Japanese Patent Laid-Open No. 2001-091136, and the relationship between parallel transmittance and orthogonal transmittance is disclosed in Japanese Patent Laid-Open No. 2002-174728. It may be within the range described in the publication.

  As described in Japanese Patent Laid-Open No. 2002-221618, the standard deviation of the parallel transmittance every 10 nm when the light wavelength is between 420 and 700 nm is 3 or less, and the light wavelength is between 420 and 700 nm. The minimum value of (parallel transmittance / orthogonal transmittance) every 10 nm may be 300 or more.

  The parallel transmittance and the orthogonal transmittance at a wavelength of 440 nm of the polarizing plate, the parallel transmittance, the parallel transmittance and the orthogonal transmittance at a wavelength of 550 nm, the parallel transmittance and the orthogonal transmittance at a wavelength of 610 nm are disclosed in JP-A-2002-258042. It is also preferable to set the range described in Japanese Unexamined Patent Publication No. 2002-258043.

(2) Hue The hue of the polarizing plate of the present invention is preferably evaluated using the lightness index L ^* and the chromaticness index a ^* and b ^* in the L ^* a ^* b ^* color system recommended as the CIE uniform perceptual space. Is done.
L ^* , a ^* , and b ^* are defined by Equation 6 using X, Y, and Z described above.

Formula 6

Here, X ₀ , Y ₀ , and Z ₀ represent tristimulus values of the illumination light source. In the case of the standard light C, X ₀ = 98.072, Y ₀ = 100, Z ₀ = 118.225, In the case of the light D ₆₅ , X ₀ = 95.045, Y ₀ = 100, Z ₀ = 108.892.

The preferable range of a ^* for a single polarizing plate is −2.5 or more and 0.2 or less, and more preferably −2.0 or more and 0 or less. A preferable range of b ^* of the single polarizing plate is 1.5 or more and 5 or less, and more preferably 2 or more and 4.5 or less. The preferable range of a ^* of the parallel transmitted light of the two polarizing plates is −4.0 to 0, and more preferably −3.5 to −0.5. The preferred range of b ^* of the parallel transmitted light of the two polarizing plates is 2.0 or more and 8 or less, more preferably 2.5 or more and 7 or less. The preferable range of a ^* of the orthogonally transmitted light of the two polarizing plates is −0.5 or more and 1.0 or less, and more preferably 0 or more and 2 or less. The preferable range of b ^* of the orthogonally transmitted light of the two polarizing plates is −2.0 or more and 2 or less, and more preferably −1.5 or more and 0.5 or less.

The hue may be evaluated by the chromaticity coordinates (x, y) calculated from the aforementioned X, Y, and Z. For example, the chromaticity (x _p , y _p ) of the parallel transmitted light of the two polarizing plates. And the chromaticity (x _c , y _c ) of the orthogonal transmitted light may be within the ranges described in JP 2002-214436 A, JP 2001-166136 A, JP 2002-169024 A, It is also preferable to make the absorbance relationship within the range described in JP-A-2001-311827.

(3) Viewing angle characteristics When a polarizing plate is arranged in crossed Nicol and light with a wavelength of 550 nm is incident, when vertical light is incident, from a azimuth of 45 degrees with respect to the polarization axis, 40 degrees with respect to the normal line It is also preferable that the transmittance ratio and the xy chromaticity difference when the light is incident at an angle of within the range described in Japanese Patent Application Laid-Open Nos. 2001-166135 and 2001-166137. In addition, as described in JP-A-10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminate having the crossed Nicols arrangement and the light transmission in the direction inclined by 60 ° from the normal line of the laminate The ratio (T ₆₀ / T ₀ ) to the rate (T ₆₀ ) is 10000 or less, or as described in JP-A No. 2002-139625, the polarizing plate is at an arbitrary angle from the normal to an elevation angle of 80 degrees. When natural light is incident, the transmittance difference of transmitted light within a wavelength range of 20 nm within the wavelength range of 520 to 640 nm of the transmission spectrum is set to 6% or less, or a film described in JP-A-08-248201 It is also preferable that the brightness difference of the transmitted light at an arbitrary place 1 cm above is within 30%.

(4) Durability (4-1) Damp heat durability Light transmittance and polarization before and after standing in an atmosphere of 60 ° C. and 90% RH for 500 hours as described in JP 2001-116922 A It is preferable that the rate of change of the degree is 3% or less based on the absolute value. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value. Further, as described in JP-A-07-0777608, it is also preferable that the degree of polarization after standing at 80 ° C. and 90% RH for 500 hours is 95% or more and the single transmittance is 38% or more.

(4-2) Dry durability It is preferable that the light transmittance and the rate of change of the degree of polarization before and after leaving in a dry atmosphere at 80 ° C. for 500 hours are also 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value.
(4-3) Other durability Further, as described in JP-A-06-167611, the shrinkage after standing at 80 ° C. for 2 hours is 0.5% or less, or the both sides of the glass plate are crossed. The x and y values after leaving the Nicol-arranged polarizing plate laminate in an atmosphere of 69 ° C. for 750 hours are within the ranges described in JP-A-10-068818, or an atmosphere of 80 ° C. and 90% RH. the change in spectral intensity ratio of the 105 cm ^-1 and 157cm ^-1 after 200 hours standing processing by Raman spectroscopy at medium, it is also preferable to fall within the range as described in JP-a-08-094834 and JP-a-09-197127 It can be carried out.

(5) Orientation degree The higher the degree of orientation of PVA, the better the polarization performance. However, the order parameter value calculated by means such as polarization Raman scattering or polarization FT-IR is preferably 0.2 to 1.0. It is. Also, as described in JP-A-59-133509, the difference between the orientation coefficient of the polymer segment in the entire amorphous region of the polarizer and the orientation coefficient of the occupied molecule (0.75 or more) is at least 0. 15, the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85, as described in JP-A No. 04-204907, or the higher order iodine ions of I ₃ ⁻ and I ₅ ⁻ The degree of orientation can be preferably set to 0.8 to 1.0 as an order parameter value.

(6) Other characteristics As described in JP-A-2002-006133, the contraction force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is 4.0 N / cm or less. As described in Kai 2002-236213, when the polarizing plate is placed under heating at 70 ° C. for 120 hours, the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarization axis direction of the polarizing plate are Both can be preferably performed within ± 0.6%, or the moisture content of the polarizing plate can be 3% by mass or less as described in JP-A-2002-090546. Further, as described in JP-A 2000-249832, the surface roughness in the direction perpendicular to the stretching axis is 0.04 μm or less based on the centerline average roughness, or described in JP-A-10-268294. It is also preferable to make the refractive index n ₀ in the transmission axis direction larger than 1.6, or to make the relationship between the thickness of the polarizing plate and the thickness of the protective film within the range described in JP-A-10-111411. be able to.

4). Functionalization of Polarizing Plate The polarizing plate of the present invention is an LCD viewing angle widening film, a retardation film such as a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, and brightness. It is preferably used as a functionalized polarizing plate combined with an improvement film, an optical film having a functional layer such as a hard coat layer, a forward scattering layer, and an antiglare (antiglare) layer.
A configuration example in which the polarizing plate of the present invention and the above-described functional optical film are combined is shown in FIG. The functional optical film 3 and the polarizer 2 may be bonded via an adhesive as a protective film on one side of the polarizing plate 5 (FIG. 1A), and the protective films 1a and 1b are attached to both surfaces of the polarizer 2. The functional optical film 3 may be bonded to the polarizing plate 5 ′ provided with the adhesive layer 4 via the adhesive layer 4 (FIG. 1B). In the former case, any transparent protective film may be used for the other protective film 1, but the colored film of the present invention is preferred. Moreover, in the polarizing plate of this invention, it is also preferable to stick an optical functional layer to a protective film through an adhesion layer, and to set it as the structure of FIG. The peel strength between layers such as the functional layer and the protective film is preferably 4.0 N / 25 mm or more as described in JP-A No. 2002-311238. The functional optical film is preferably disposed on the liquid crystal module side according to the intended function, or on the side opposite to the liquid crystal module, that is, on the display side or the backlight side.

  The functional optical film used in combination with the polarizing plate of the present invention will be described below.

(1) Viewing Angle Enlargement Film The polarizing plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Bend), VA (Vertically Aligned), ECB (Electrically Bold). It can be used in combination with a viewing angle widening film proposed for the display mode.

As the viewing angle widening film for TN mode, Journal of the Japan Printing Society, Vol. 36, No. 3 (1999) p40-44, Monthly Display August (2002) p20-24, JP-A-4-229828, JP-A-6- A WV film (manufactured by Fuji Photo Film Co., Ltd.) described in JP-A-75115, JP-A-6-214116, JP-A-8-50206 and the like is preferably used in combination.
A preferred configuration of the viewing angle widening film for the TN mode has an alignment layer and an optically anisotropic layer in this order on the polymer film of the present invention. Although a viewing angle expansion film may be used by being bonded to a polarizing plate via an adhesive, SID'00 Dig. As described in p551 (2000), it is particularly preferable from the viewpoint of thinning that the protective film for the polarizer is also used as one of the protective films.

  The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, or formation of a layer having a microgroup. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. It is preferable that the absorption axis direction and the rubbing direction of the polarizer are substantially parallel. As the polymer used for the alignment layer, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in JP-A-9-152509, and the like can be preferably used. The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer preferably contains a liquid crystalline compound. The liquid crystal compound used in the present invention particularly preferably has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like a triphenylene derivative of D-1 having the following structure, and has a structure in which side chains extend radially therefrom. In order to impart stability over time, it is also preferable to further introduce a group that reacts with heat, light or the like. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.

D-1

  The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented so that they are perpendicular to the plane on the opposite air side. doing. The discotic liquid crystal layer as a whole has a hybrid alignment, and this layer structure can realize a wide viewing angle of a TN mode TFT-LCD.

  The optically anisotropic layer is generally formed by applying a solution obtained by dissolving a discotic compound and other compounds (for example, polymerizable monomer, photopolymerization initiator) in a solvent onto the alignment layer, drying, and then forming a discotic nematic phase. After heating to temperature, it is obtained by polymerization by irradiation with UV light or the like, and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

  In addition to the discotic compound added to the optically anisotropic layer, the compound has compatibility with the discotic compound and can give a preferable change in tilt angle to the liquid crystalline discotic compound or inhibit the alignment. Any compound can be used as long as it is not. Among these, polymerizable monomers (eg, compounds having a vinyl group, vinyloxy group, acryloyl group and methacryloyl group), orientation control additives such as fluorine-containing triazine compounds, cellulose acetate, cellulose acetate propio And polymers such as nates, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.

  The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.

  A preferred embodiment of the viewing angle widening film is composed of a cellulose acylate film as a base film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer. The optically anisotropic layer is crosslinked by UV light irradiation.

  In addition to the above, when the viewing angle widening film and the polarizing plate of the present invention are combined, for example, as described in JP-A-07-198942, a compound having an optical axis in the direction intersecting the plate surface is used. It is also preferable to laminate with a retardation plate exhibiting anisotropy in refraction, or to make the dimensional change rate of the protective film and the optically anisotropic layer substantially the same as described in JP-A No. 2002-258052. It can be carried out. Further, as described in JP-A No. 2000-258632, the moisture content of the polarizing plate bonded to the viewing angle widening film is set to 2.4% or less, or as described in JP-A No. 2002-267839. Further, the contact angle with water on the surface of the viewing angle widening film can be preferably set to 70 ° or less.

  The viewing angle widening film for an IPS mode liquid crystal cell is used for optical compensation of liquid crystal molecules aligned in parallel to the substrate surface and for improving the viewing angle characteristics of the orthogonal transmittance of the polarizing plate during black display without an electric field. In the IPS mode, black is displayed when no electric field is applied, and the transmission axes of the pair of upper and lower polarizing plates are orthogonal. However, when observed from an oblique direction, the crossing angle of the transmission axes is not 90 °, and leakage light is generated, resulting in a decrease in contrast. When the polarizing plate of the present invention is used in an IPS mode liquid crystal cell, the in-plane retardation as described in JP-A-10-54982 is close to 0 and the thickness direction is reduced in order to reduce leakage light. It is preferably used in combination with a viewing angle widening film having a phase difference.

  The OCB mode viewing angle widening film for liquid crystal cells is intended to improve the viewing angle characteristics of black display by optically compensating the liquid crystal layer that is vertically aligned at the center of the liquid crystal layer by applying an electric field and tilted near the substrate interface. used. When the polarizing plate of the present invention is used in an OCB mode liquid crystal cell, it is preferably used in combination with a viewing angle widening film in which a discotic liquid crystalline compound as described in US Pat. No. 5,805,253 is hybrid-aligned.

The viewing angle widening film for a liquid crystal cell in the VA mode improves the viewing angle characteristics of black display in a state where liquid crystal molecules are vertically aligned with respect to the substrate surface in the absence of an electric field.
Such a viewing angle widening film is a film having an in-plane retardation close to 0 and having a retardation in the thickness direction as described in Japanese Patent No. 2866372, or a discotic compound. In order to prevent the deterioration of orthogonal transmittance in the oblique direction of the polarizing plate It is preferably used in combination with a laminate of films made of such rod-like compounds.

(2) Retardation film The polarizing plate of the present invention preferably has a retardation layer. The retardation layer in the present invention is preferably a λ / 4 plate, and can be used as a circularly polarizing plate by laminating the polarizing plate of the present invention and the λ / 4 plate. The circularly polarizing plate has a function of converting incident light into circularly polarized light, and is preferably used for a reflective liquid crystal display device, a transflective liquid crystal display device such as an ECB mode, or an organic EL element.

  The λ / 4 plate used in the present invention is a retardation film having a retardation (Re) of approximately ¼ of the wavelength in the visible light wavelength range in order to obtain almost perfect circularly polarized light in the visible light wavelength range. It is preferable that "Retardation of approximately 1/4 in the wavelength range of visible light" means that the longer the wavelength is from 400 to 700 nm, the larger the retardation, and the retardation value (Re450) measured at a wavelength of 450 nm is 80 to 125 nm. And the range which satisfies the relationship whose retardation value (Re590) measured by wavelength 590nm is 120 to 160 nm is shown. It is more preferable that Re590-Re450 ≧ 5 nm, and it is particularly preferable that Re590-Re450 ≧ 10 nm.

  The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied. For example, in Japanese Patent Laid-Open Nos. 5-27118, 10-68816, and 10-90521 Lambda / 4 plate in which a plurality of polymer films described above are laminated, Lambda / 4 plate obtained by stretching one polymer film described in WO00 / 65384, WO00 / 26705, JP 2000-284126 A A known λ / 4 plate such as a λ / 4 plate in which at least one optically anisotropic layer is provided on a polymer film described in JP-A-2002-31717 can be used. Moreover, the direction of the slow axis of the polymer film and the orientation direction of the optically anisotropic layer can be arranged in any direction according to the liquid crystal cell.

  In the circularly polarizing plate, the slow axis of the λ / 4 plate and the transmission axis of the polarizer can intersect at an arbitrary angle, but preferably intersect within a range of 45 ° ± 20 °. However, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may intersect within a range other than the above.

  When the λ / 4 plate is formed by laminating the λ / 4 plate and the λ / 2 plate, as described in Japanese Patent No. 3236304 and Japanese Patent Laid-Open No. 10-68816, the λ / 4 plate and The λ / 2 plate is preferably bonded so that the angle formed between the slow axis in the plane of the λ / 2 plate and the transmission axis of the polarizing plate is substantially 75 ° and 15 °.

(3) Antireflection film The polarizing plate of the present invention can be used in combination with an antireflection film. As the antireflection film, either a film having a reflectivity of about 1.5% only by applying a single layer of a low refractive index material such as a fluorine-based polymer, or a film having a reflectivity of 1% or less using multilayer interference of a thin film is used. it can. In the present invention, a structure in which a low refractive index layer and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a middle refractive index layer) is laminated on the support is preferably used. . Also, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28, JP-A No. 2002-301783, and the like can also be preferably used.
The refractive index of each layer satisfies the following relationship.

  Refractive index of the high refractive index layer> Refractive index of the medium refractive index layer> Refractive index of the support> Refractive index of the low refractive index layer

  As the support used for the antireflection film, a polymer film used for the protective film of the above-mentioned polarizer can be preferably used.

The refractive index of the low refractive index layer is 1.20 to 1.55, preferably 1.30 to 1.50. The low refractive index layer is preferably used as an outermost layer having scratch resistance and antifouling properties. In order to improve the scratch resistance, it is also preferable to impart slipperiness to the surface using a material containing a silicone group or fluorine.
Examples of the fluorine-containing compound include paragraph numbers [0018] to [0026] of JP-A-9-222503, paragraph numbers [0019] to [0030] of JP-A-11-38202, and paragraph numbers of JP-A-2001-40284. [0027] to [0028], compounds described in JP-A No. 2000-284102 and the like can be preferably used.
The silicone-containing compound is preferably a compound having a polysiloxane structure, but reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane at both ends (JP-A-11-258403), etc. An organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent may be cured by a condensation reaction in the presence of a catalyst (Japanese Patent Laid-Open No. 58-142958). Gazettes, 58-147483, 58-147484, JP-A-9-157582, 11-106704, JP-A-2000-117902, 2001-48590, 2002-2002. 53804).

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as fillers (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as additives other than the above. Inorganic compounds having a low refractive index, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820), silane coupling agents, slip agents, surfactants, and the like are preferably added. be able to.
The low refractive index layer may be formed by a vapor phase method (vacuum vapor deposition method, sputtering method, ion plating method, plasma CVD method, etc.), but is preferably formed by a coating method because it can be manufactured at low cost. . As the coating method, dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, and micro gravure can be preferably used.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

The medium refractive index layer and the high refractive index layer preferably have a constitution in which ultrafine particles of high refractive index having an average particle size of 100 nm or less are dispersed in a matrix material. The inorganic compound fine particles having a high refractive index include inorganic compounds having a refractive index of 1.65 or more, for example, oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and metal atoms thereof. A composite oxide or the like can be preferably used.
Such ultrafine particles may be obtained by treating the surface of the particles with a surface treatment agent (silane coupling agent, etc .: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds or (Organic metal coupling agent: JP-A No. 2001-310432, etc.), core-shell structure with a high refractive index particle as a core (JP-A No. 2001-166104, etc.), or a specific dispersant (eg, JP-A No. 11- No. 153703, Patent No. US62010858B1, Japanese Patent Laid-Open No. 2002-27776069, etc.).
As the matrix material, conventionally known thermoplastic resins, curable resin films, and the like can be used, but JP-A-2000-47004, 2001-315242, 2001-31871, and 2001-296401. It is also possible to use a curable film obtained from a polyfunctional material described in a gazette or the like or a metal alkoxide composition described in JP-A-2001-293818 or the like.
The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(4) Brightness improving film The polarizing plate of this invention can be used in combination with a brightness improving film.
The brightness enhancement film has a function of separating circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and reflects or scatters one circularly polarized light or linearly polarized light back to the backlight side. Re-reflected light from the backlight part partially changes the polarization state and partially transmits when re-entering the brightness enhancement film and the polarizing plate, so the light utilization rate is improved by repeating this process. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection system and an anisotropic scattering system are known, and both can be combined with the polarizing plate of the present invention.

  In the anisotropic reflection system, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers and increasing the refractive index difference in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal systems (European Patent No. 606940A2, Japanese Patent Laid-Open No. Hei 8- No. 271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. Are preferably used in the present invention. For NIPOCS, see Nitto Giho, vol. 38, no. 1, may, 2000, pages 19 to 21 and the like.

  Further, in the present invention, the positive values described in the specifications of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226 and JP-A-9-274108 and 11-174231 are described. It is also preferable to use it in combination with a brightness enhancement film of an anisotropic scattering method in which an intrinsic birefringent polymer and a negative intrinsic birefringent polymer are blended and uniaxially stretched. As the anisotropic scattering system brightness enhancement film, DRPF-H (manufactured by 3M) is preferable.

  The polarizing plate and the brightness enhancement film of the present invention are preferably used as an integrated type in which one of the polarizing film and the protective film of the polarizing plate is bonded via an adhesive.

(5) Other functional optical films The polarizing plate of the present invention further includes a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, a gas barrier layer, a sliding layer, an antistatic layer, an undercoat layer, a protective layer, and the like. It is also preferred to use it in combination with a functional optical film provided with These functional layers are preferably used in combination with each other or in the same layer as the above-described antireflection layer, optically anisotropic layer, or the like.

(5-1) Hard Coat Layer The polarizing plate of the present invention is preferably combined with a functional optical film provided on the surface of the support in order to impart mechanical strength such as scratch resistance. Is called. When the hard coat layer is applied to the above-described antireflection film, it is particularly preferable to provide it between the support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of the curable compound by light and / or heat. The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound. As specific constitutional compositions of the hard coat layer, for example, those described in JP-A Nos. 2002-144913, 2000-9908 and WO0 / 46617 can be preferably used.
The film thickness of the hard coat layer is preferably 0.2 to 100 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group or a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferred examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol. Polyacrylates of polyols such as hexaacrylate; epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether; obtained by reaction of polyisocyanate and hydroxyl group-containing acrylate such as hydroxyethyl acrylate Examples of preferred compounds include urethane acrylates. Moreover, as a commercially available compound, EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (above, Daicel UCB Co., Ltd. product), UV -6300, UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.
Preferred examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, glycerol triglycidyl ether as glycidyl ethers. Triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin, etc. Celoxide 2021P, Celoxide 2081, Epoxide GT-301, Epolide GT-401, EHPE3150CE (above, IXETA 121, OXT-221, OX-SQ, PNOX-1009 (above, manufactured by Toagosei Co., Ltd.) and the like as oxetanes such as polyisocyanate epoxy methyl ether of phenolic novolak resin) Can be mentioned. In addition, a polymer of glycidyl (meth) acrylate or a copolymer of a monomer that can be copolymerized with glycidyl (meth) acrylate may be used for the hard coat layer.

  In the hard coat layer, fine particles of oxide such as silicon, titanium, zirconium, and aluminum are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and reduce curling of the hard coat treated article of the present invention. It is also preferable to add crosslinked fine particles such as crosslinked fine particles such as polyethylene, polystyrene, poly (meth) acrylic acid esters, polydimethylsiloxane, etc., and fine organic particles such as fine crosslinked rubber particles such as SBR and NBR. These crosslinked fine particles preferably have an average particle size of 1 nm to 20000 nm. Further, the shape of the crosslinked fine particles can be used without any particular limitation, such as a spherical shape, a rod shape, a needle shape, or a plate shape. The addition amount of the fine particles is preferably 60% by volume or less, more preferably 40% by volume or less of the hard coat layer after curing.

  In the case of adding the inorganic fine particles described above, since the affinity with the binder polymer is generally poor, it contains a metal such as silicon, aluminum, titanium, etc., and an alkoxide group, carboxylic acid group, sulfonic acid group, phosphonic acid group, etc. It is also preferable to perform a surface treatment using a surface treatment agent having a functional group of

  The hard coat layer is preferably cured using heat or active energy rays. Among them, active energy rays such as radiation, gamma rays, alpha rays, electron rays, and ultraviolet rays are more preferred, and safety and productivity are improved. In view of the above, it is particularly preferable to use an electron beam or an ultraviolet ray. In the case of curing with heat, in consideration of the heat resistance of the plastic itself, the heating temperature is preferably 140 ° C. or lower, more preferably 100 ° C. or lower.

(5-2) Forward scattering layer The forward scattering layer is used to improve the viewing angle characteristics (hue and luminance distribution) in the vertical and horizontal directions when the polarizing plate of the present invention is applied to a liquid crystal display device. In the present invention, a configuration in which fine particles having different refractive indexes are dispersed in a binder is preferable. The construction of JP-A No. 199809, JP-A No. 2002-107512 that defines the haze value as 40% or more can be used. In addition, in order to control the viewing angle characteristics of haze, the polarizing plate of the present invention is also preferably used in combination with “Lumisty” described in Sumitomo Chemical's technical report “Photofunctional Films” on pages 31-39. be able to.

(5-3) Antiglare layer The antiglare (antiglare) layer is used to scatter reflected light and prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
The method for forming irregularities on the film surface is, for example, a method of adding fine particles to form irregularities on the film surface (for example, JP-A No. 2000-271878), relatively large particles (particle size 0.05 to 2 μm). ) Is added in a small amount (0.1 to 50% by mass) (for example, JP-A Nos. 2000-281410, 2000-95893, 2001-100004, and 2001). No. 281407, etc.), a method of physically transferring the concavo-convex shape onto the film surface (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Etc.) can be preferably used.

  These functional layers can be used by providing either one side or both sides of the polarizer side and the opposite side of the polarizer.

Next, the liquid crystal display device of the present invention will be described.
FIG. 2 shows an example of the liquid crystal display device of the present invention.

  The liquid crystal display device shown in FIG. 2 includes a liquid crystal cell (15 to 19) and an upper polarizing plate 11 and a lower polarizing plate 22 that are disposed with the liquid crystal cell (15 to 19) interposed therebetween. The polarizing plate is sandwiched between a polarizer and a pair of protective films, but is shown as an integrated polarizing plate in FIG. The liquid crystal cell includes a liquid crystal layer formed of an upper substrate 15 and a lower substrate 18 and liquid crystal molecules 17 sandwiched therebetween. The liquid crystal cell has different alignment states of liquid crystal molecules that perform ON / OFF display, and includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend), VA (Vertical Aligned Electrified), ECB (Etc. Although the polarizing plate of the present invention can be used in any display mode regardless of the transmissive and reflective types, it is preferable for the TN mode, IPS mode, VA mode, and OCB mode. Further, the contrast effect of the film of the present invention is greatly exhibited when the size of the display device is large. The size of the display device is preferably 15 inches or more, preferably 22 inches or more, and most preferably 25 inches or more.

  An alignment film (not shown) is formed on the surface of the substrates 15 and 18 in contact with the liquid crystal molecules 17 (hereinafter also referred to as “inner surface”), and by rubbing treatment or the like applied on the alignment film, The alignment of the liquid crystal molecules 17 in the state where no electric field is applied or the state where a low voltage is applied is controlled. Further, on the inner surfaces of the substrates 15 and 18, a transparent electrode (not shown) capable of applying an electric field to the liquid crystal layer made of the liquid crystal molecules 17 is formed.

The rubbing direction of the TN mode is applied in directions perpendicular to each other on the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle (twist angle) of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm was added so that the twist angle was 90 °.
The twist angle is in the vicinity of 90 ° (85 to 95 °) in the case of a notebook computer, a personal computer monitor, and a liquid crystal display device for a television, and is 0 to 70 ° in the case of use as a reflective display device such as a mobile phone. Set. In the IPS mode and the ECB mode, the twist angle is 0 °. In the IPS mode, electrodes are disposed only on the lower substrate 18 and an electric field parallel to the substrate surface is applied. In the OCB mode, there is no twist angle and the tilt angle is increased, and in the VA mode, the liquid crystal molecules 17 are aligned perpendicular to the upper and lower substrates.

Here, the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn changes the brightness during white display. Therefore, in order to obtain the maximum brightness, the range is set for each display mode.
In general, the crossing angle of the absorption axis 12 of the upper polarizing plate 11 and the absorption axis 23 of the lower polarizing plate 22 is generally perpendicular to obtain a high contrast. The crossing angle between the absorption axis 12 of the upper polarizing plate 11 of the liquid crystal cell and the rubbing direction of the upper substrate 15 varies depending on the liquid crystal display mode, but is generally set to be parallel or vertical in the TN and IPS modes. In OCB and ECB modes, it is often set to 45 °. However, the optimum value differs in each display mode for adjusting the color tone and viewing angle of the display color, and the present invention is not limited to this range.

  The liquid crystal display device in which the polarizing plate of the present invention is used is not limited to the configuration of FIG. 2, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizer. In addition, the above-described viewing angle widening films 13 and 20 may be separately disposed between the liquid crystal cell and the polarizing plate. The polarizing plates 11 and 22 and the viewing angle widening films 13 and 20 may be arranged in a laminated form bonded with an adhesive, or a so-called integrated elliptical polarization using one of the liquid crystal cell side protective films for widening the viewing angle. It may be arranged as a plate.

  When used as a transmissive display device, a cold cathode or hot cathode fluorescent tube, or a backlight using a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. Further, the liquid crystal display device in which the polarizing plate of the present invention is used may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back of the liquid crystal cell or under the liquid crystal cell. A reflective film is installed on the inner surface of the side substrate. Of course, a front light using the light source may be provided on the liquid crystal cell observation side.

[Example 1: Production of cellulose acetate film 1]
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acetate solution A was prepared.

<Composition of cellulose acetate solution A>
Cellulose acetate having an acetylation degree of 61.0% 100 parts by weight Triphenyl phosphate (plasticizer) 8.1 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.6 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (No. 1) 2 solvents) 54 parts by mass 1-butanol 11 parts by mass

  In a separate mixing tank, the following composition was charged into the mixing tank, stirred while heating to dissolve each component, and an additive solution B was prepared.

<Additive solution B composition>
Methylene chloride 100 parts by weight Methanol 20 parts by weight UV absorber (A) 2 parts by weight UV absorber (B) 4 parts by weight cyan dye (15): 1-methylamino-4- (4-methylphenylamino) anthraquinone 012 parts by mass Magenta dye: M-1 0.003 parts by mass Yellow dye: Y-19 0.006 parts by mass

<Preparation of cellulose acetate film 1>
A dope was prepared by adding 474 parts by mass of the cellulose acetate solution A and 40 parts by mass of the additive solution B and stirring sufficiently. The dope was cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off at a solvent content of 70% by mass, and both ends in the width direction of the film are fixed with a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3 to 5% by mass. Then, it was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was 3%. Then, it dried further by conveying between the rolls of a heat processing apparatus, and produced the 80-micrometer-thick cellulose acetate film 1. FIG.

[Example 2: Production of cellulose acetate films 2 to 4]
Cellulose acetate films 2 to 4 were produced in the same manner as the cellulose acetate film 1 except that the addition amount of the dye was changed to the amount shown in Table 1 in the production of the cellulose acetate film 1.

(Measurement of optical properties: measurement of retardation value)
The retardation value of the produced cellulose acetate film was measured by the following method. The results are shown in Table 1.
In-plane retardation Re (0) was measured at 25 ° C. and 60% RH using an ellipsometer (M-150, manufactured by JASCO Corporation). Retardation Re (40) and Re (-40) were measured with the in-plane slow axis as the tilt axis at 40 ° and -40 °. Using the film thickness and the refractive index nx in the slow axis direction as parameters, the refractive index ny and the thickness direction in the fast axis direction are fitted to these measured values Re (0), Re (40), Re (−40). The refractive index nz was determined by calculation to determine the Rth retardation value. The measurement wavelength was 632.8 nm.

[Example 3: Production of polarizing plate (1)]
(Saponification treatment)
Cellulose acetate films 1 to 4 were immersed in a 1.5 mol / L sodium hydroxide aqueous solution at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing bath, and neutralized using 0.05 mol / L sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of the cellulose acetate film was saponified.
Furthermore, a WV film manufactured by Fuji Photo Film was saponified under the same conditions and used for the following sample preparation.

(Preparation of polarizing plate)
A polarizer was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the cellulose acetate film 1 prepared in Example 1 was attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizer and the slow axis of the cellulose acetate film were arranged in parallel.
Further, the WV film saponified in Example 3 was attached to the opposite side of the polarizer using a polyvinyl alcohol-based adhesive. In this way, a polarizing plate (1) was produced.

[Example 4: Production of polarizing plates (2) to (4)]
Polarizing plates (2) to (4) were produced in the same manner as in Example 3 except that the cellulose acetate films 2 to 4 were used instead of the cellulose acetate film 1.

[Example 5: Mounting of polarizing plate to liquid crystal display device]
A pair of polarizing plates provided on a 20-inch liquid crystal display device (LC-20V1, manufactured by Sharp Corporation) using a TN type liquid crystal cell was peeled off, and the polarizing plates prepared in Examples 3 and 4 (1 ) To (4) were attached to the observer side and the backlight side one by one through an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be orthogonal to each other. Only the central portion of about 2 cm × 2 cm was black and the other portions were displayed as white images, and the contrast and white luminance of the central portion were measured with a TOPCON BM-5.
In addition, the transmission density | concentration of the protective film of Table 2 is the value measured by X-Rite 310 by X-Light before attaching a cellulose acetate film to a polarizer.
The results are shown in Table 2.

  From Table 2, it can be seen that the liquid crystal display device using the cellulose acetate film of the transmission density of the present invention gives a high contrast image while maintaining the white luminance. On the other hand, when a cellulose acylate film having a R, G, B transmission density exceeding 0.4 in Status M was used, the white luminance was lowered.

[Example 6]
(Preparation of cellulose acetate solution)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acetate solution C.

<Cellulose acetate solution C composition>
Cellulose acetate with an acetylation degree of 60.9% 100.0 parts by weight Triphenyl phosphate 8.0 parts by weight Biphenyl phosphate 4.0 parts by weight Methylene chloride (first solvent) 402.0 parts by weight Methanol (second solvent) 60.0 parts by mass

(Preparation of matting agent solution)
The following composition was charged into a disperser and stirred to dissolve each component to prepare a cellulose acetate solution.
<Matting agent solution composition>
Silica particles having an average particle diameter of 16 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd. 2.0 parts by mass Methylene chloride (first solvent) 76.3 parts by weight Methanol (second solvent) 11.4 parts by weight Cellulose acetate solution C 10 .3 parts by mass

(Preparation of additive solution)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
<Additive solution composition>
The following additive (I) 19.8 parts by weight Methylene chloride (first solvent) 58.4 parts by weight Methanol (second solvent) 8.7 parts by weight Cellulose acetate solution C 12.8 parts by weight Cyan dye (15):
1-methylamino-4- (4-methylphenylamino) anthraquinone
0.017 parts by mass Magenta dye M-1: 0.004 parts by mass Yellow dye Y-19: 0.009 parts by mass Additive (I)

(Preparation of cellulose acetate film 11)
94.6 parts by mass of the cellulose acetate solution C, 1.3 parts by mass of the matting agent solution, and 4.1 parts by mass of the retardation increasing agent solution were mixed after filtration, and cast using a band casting machine. The mass ratio of the retardation increasing agent to cellulose acetate was 4.6%. The film was peeled off from the band with a residual solvent amount of 30%, and the film with a residual solvent amount of 13% by mass was stretched at a stretching ratio of 28% using a tenter under the condition of 130 ° C. Hold at 30 ° C. for 30 seconds. Thereafter, the clip was removed and dried at 140 ° C. for 40 minutes to produce a cellulose acetate film. The resulting cellulose acetate film had a residual solvent amount of 0.2% and a film thickness of 92 μm.

[Example 7]
(Production of cellulose film films 12 to 14)
Cellulose acetate films 12 to 14 were produced in the same manner except that the amount of the dye in the additive solution was changed to the contents shown in Table 3.

(Measurement of optical properties)
The retardation value of the produced cellulose acetate film was measured by the method described above. The results are shown in Table 3.

[Example 8: Production of polarizing plate and attachment to liquid crystal display device]
(Saponification treatment)
On the cellulose acetate film 11 produced in Example 6, 5.2 ml / m ^{2 of the following} composition was applied and dried at 60 ° C. for 10 seconds. The surface of the film was washed with running water for 10 seconds, and air at 25 ° C. was blown to dry the film surface.
<Saponification solution composition>
Isopropyl alcohol 818 parts by weight Water 167 parts by weight Propylene glycol 187 parts by weight Potassium hydroxide 68 parts by weight

(Formation of alignment film)
On the saponified cellulose acetate film 11, a coating solution having the following composition was applied at 24 ml / m ² with a # 14 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.
Next, the film formed was rubbed in the direction of 45 ° with the stretching direction of the cellulose acetate film (support) (substantially coincident with the slow axis).

<Alignment film coating solution composition>
The following modified polyvinyl alcohol 20 parts by mass Water 360 parts by mass Methanol 120 parts by mass Glutaraldehyde (crosslinking agent) 1.0 part by mass

(Formation of optically anisotropic layer)
On the alignment film, 91 parts by mass of the following discotic liquid crystalline molecules (I), 9 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531- 1, 1.5 parts by mass of Eastman Chemical Co., Ltd., 3 parts by mass of a photopolymerization initiator (Irgacure 907, Ciba Geigy), 1 part by mass of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.), A coating solution prepared by dissolving 1.0 part by mass of a citrate ester mixture of the following formula in 214.2 parts by mass of methyl ethyl ketone was applied at a temperature of 25 ° C. with a # 3.6 wire bar coater at 6.2 ml / m ² . . This was affixed to a metal frame and heated in a constant temperature bath at 140 ° C. for 2 minutes to align the discotic liquid crystalline molecules. Next, using a 120 W / cm high-pressure mercury lamp at 90 ° C., UV irradiation was performed for 1 minute to polymerize the discotic liquid crystalline molecules. Then, it stood to cool to room temperature, the optically anisotropic layer was formed, and the optical compensation sheet was produced.

Discotic liquid crystalline molecules (I)

(Preparation of polarizing plate)
A polarizer was prepared by adsorbing iodine to a stretched polyvinyl alcohol film.
Next, the cellulose acetate film 11 (support) side of the produced optical compensation sheet was attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. The slow axis of the support and the transmission axis of the polarizer were arranged in parallel.
A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was saponified in the same manner as in Example 3, and the other side of the polarizer (with an optical compensation sheet attached) using a polyvinyl alcohol-based adhesive. Pasted on the side that did not exist).
In this way, a polarizing plate (11) was produced.

(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 5.7 μm. A bend-aligned liquid crystal cell was prepared by injecting a liquid crystal compound (ZLI1132, manufactured by Merck & Co., Inc.) having a Δn of 0.1396 into the cell gap.

(Production of liquid crystal display device)
Two produced polarizing plates (11) were bonded so as to sandwich the produced bend alignment cell. The optically anisotropic layer of the polarizing plate faced the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were antiparallel.

[Example 9]
Polarizing plates (12) to (14) were prepared in the same manner as in Example 8 except that the cellulose acetate film was changed to 12 to 14 in the polarizing plate (11). Arranged in a liquid crystal display device.
In the same manner as in Example 5, only the central portion of about 2 cm × 2 cm was displayed in black, and the other portions were displayed as white images, and the contrast and white luminance of the black display portion were measured with BM-5 manufactured by TOPCON. The permeation density of the cellulose acetate film, which is a protective film, is a value measured using an X-Rite 310 manufactured by X-Rite before forming the alignment film.
The results are shown in Table 4 including the case of the polarizing plate (11).

  From the results of Table 4, it can be seen that the liquid crystal display device using the polarizing plate of the present invention can obtain a high-contrast image without impairing the white luminance.

[Example 10: Evaluation of mounting on VA liquid crystal display device]
A pair of polarizing plates provided in a 22-inch liquid crystal display device (manufactured by Sharp Corporation) using a VA type liquid crystal cell is peeled off, and the polarizing plate (11) produced in Example 8 is optically anisotropic instead. The adhesive layer was attached to the viewer side and the backlight side one by one so as to be on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be orthogonal to each other.
It was found that the liquid crystal display device using the polarizing plate of the present invention has a high contrast and is preferable.

[Example 12: Evaluation of mounting on IPS liquid crystal display device]
An optical compensation film obtained by uniaxially stretching a polycarbonate film was bonded to the polarizing plate (2) of the present invention produced in Example 4 to provide an optical compensation function. At this time, by making the slow axis of the in-plane retardation of the optical compensation film orthogonal to the transmission axis of the polarizing plate, the visual characteristics can be improved without changing the front characteristics at all. An optical compensation film having an in-plane retardation Re of 274 nm and a thickness direction retardation Rth of 45 nm was used.
A 15-inch display device was produced in which the laminate of the polarizing plate (2) and the optical compensation film produced as described above, the IPS type liquid crystal cell, and the polarizing plate (2) were stacked and assembled in this order. . At this time, the transmission axes of the upper and lower polarizing plates are orthogonal to each other, and the transmission axis of the upper polarizing plate is parallel to the molecular long axis direction of the liquid crystal cell (that is, the slow axis of the optical compensation layer and the molecular long axis direction of the liquid crystal cell are orthogonal). ). The liquid crystal cell, electrode, and substrate used in the past as IPS were used as they were (the liquid crystal cell was aligned horizontally, the liquid crystal had positive dielectric anisotropy, and was used for IPS liquid crystal. Developed and marketed). The physical properties of the liquid crystal cell were as follows: Δn of liquid crystal: 0.099, cell gap of liquid crystal layer: 3.0 μm, pretilt angle: 5 degrees, rubbing direction: 75 degrees on both upper and lower sides of the substrate.
Evaluation similar to Example 5 was performed about the liquid crystal display device produced as mentioned above. When the contrast at the time of black display was measured only at the central part in the azimuth direction 45 degrees and the polar angle direction 70 degrees from the front of the apparatus, it was found that the liquid crystal display device using the polarizing plate of the present invention had high contrast and was preferable. .
Further, when 13-inch and 22-inch liquid crystal display devices were produced in the same manner as described above, the contrast of the liquid crystal display device of the present invention was improved as the display size was increased. It turns out that it is obtained.

(A) is a schematic sectional drawing which shows the example which adhere | attached the functional optical film on both surfaces, (B) on the one side of the polarizing plate of this invention. It is the schematic which shows the liquid crystal display device using the polarizing plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Protective film 2 Polarizer 3 Functional optical film 4 Adhesive layer 5, 5 'Polarizing plate 11 Upper polarizing plate 12 Upper polarizing plate Absorption axis 13 Upper viewing angle expansion film 14 Upper optical anisotropic layer orientation control direction 15 Liquid crystal Cell upper electrode substrate 16 Upper substrate alignment control direction 17 Liquid crystal molecule 18 Liquid crystal cell lower electrode substrate 19 Lower substrate alignment control direction 20 Lower viewing angle widening film 21 Lower optical anisotropic layer alignment control direction 22 Lower polarizing plate 23 Lower polarizing plate absorption axis

Claims (12)

A polarizing plate in which a protective film is bonded to both sides of a polarizer, and at least one of the protective films is a colored film having a B, G, R transmission density of Status M satisfying the following range: Board.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4   The polarizing film according to claim 1, wherein the colored film is a cellulose acylate film.   The polarizing plate according to claim 1, wherein an adhesive layer is provided on the polarizing plate.   The polarizing plate according to claim 1, wherein an antiglare layer is provided on the air-side protective film.   The polarizing plate according to claim 1, further comprising an antireflection layer.   A polarizing plate according to claim 1, comprising a retardation layer.   It has a viewing angle compensation layer, The polarizing plate in any one of Claims 1-6 characterized by the above-mentioned.   The polarizing plate according to claim 1, further comprising a brightness enhancement layer. In a liquid crystal display device having a liquid crystal display element and a polarizing plate in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film, the transmission densities of B, G, and R of status M satisfy the following range A liquid crystal display device comprising at least one colored film.
0.02 ≦ B transmission density ≦ 0.4
0.02 ≦ G transmission density ≦ 0.4
0.02 ≦ R transmission density ≦ 0.4   The liquid crystal display device according to claim 9, comprising at least one polarizing plate according to claim 1.   The liquid crystal display device according to claim 10, wherein the liquid crystal mode is any one of a TN mode, an OCB mode, an IPS mode, and a VA mode.   The liquid crystal display device according to claim 9, wherein the screen size is 15 inches or more.

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