JP2005128520A - Polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate keeping a change of transmissivity and a degree of polarization caused by heat and humidity small and excellent in durability, and also to provide a liquid crystal display device having high display quality without causing trouble such as rise of the transmissivity of an entire screen and frame-shaped light leakage in black display. <P>SOLUTION: The polarizing plate is set so that the water-vapor permeability of a 1st protection film 34 is lower than that of a 2nd protection film 35 on a liquid crystal cell side in the polarizing plates 30 and 31 constituted by laminating the 1st protection film 34, a polarizer 33 and the 2nd protection film 35 in this order. In the liquid crystal display device, the polarizing plate is used as at least either polarizing plate 30 or 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

The liquid crystal display device is increasingly used year by year as an image display device with small power consumption and a small space. Conventionally, a large viewing angle dependency of an image has been a major drawback of a liquid crystal display device. However, in recent years, high viewing angle liquid crystal modes such as a VA mode and an IPS mode have been put into practical use. Demand for liquid crystal display devices is rapidly expanding even in markets where demand is high. Along with this, higher performance has begun to be demanded for polarizing plates used in liquid crystal display devices. In particular, improvement of durability against temperature and humidity is a big problem for polarizing plates.
The polarizing plate is produced by adsorbing iodine to a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol, or an ethylene / vinyl acetate copolymer partially saponified film and then stretching the film. It is common. However, these polarizing plates have a problem that, when used for a long period of time, the transmittance of the entire screen in black display increases, and a frame-like light leakage occurs.
The increase in the transmittance and the light leakage of the frame shape are due to relaxation of the stretched hydrophilic polymer and decomposition of iodine, and it is known that the amount of moisture permeation from the outside through the protective film greatly affects. It has been. On the other hand, Patent Document 1 and Patent Document 2 disclose a method of manufacturing a polarizing plate by bonding a protective film having low moisture permeability to a polarizer. However, although these methods can suppress moisture transmission from the outside after the polarizing plate is produced, the evaporation of moisture from the inside to the outside during drying in the polarizing plate making process is prevented, and the moisture content in the polarizer remains high. Since the polarizing plate is preserved, the durability improving effect was insufficient.
JP 2002-328223 A JP 2002-341135 A

An object of the present invention is to provide a polarizing plate having a small change in transmittance and polarization degree due to heat and humidity.
Another object of the present invention is to provide a liquid crystal display device with high display quality without causing problems such as light leakage by using a polarizing plate in which protective films having different moisture permeability are arranged on both sides of a polarizer in a liquid crystal display device. Is to provide.

As a result of intensive studies, the present inventor has found that moisture permeation from the outside through the protective film of the polarizing plate after the liquid crystal cell is bonded is mainly a protective film on the air interface side with respect to the polarizer (hereinafter referred to as the first protective film). The liquid crystal cell side protective film (hereinafter also referred to as a second protective film) has a water permeability that is large enough to allow the water in the polarizer to evaporate sufficiently during the production of the polarizing plate, It has been found that this problem can be solved by setting the interface-side protective film to a low water permeability so as not to allow moisture from entering the polarizer after bonding.
That is,

1) In a polarizing plate in which a first protective film, a polarizer, and a second protective film are laminated in this order, the second protective film is a liquid crystal cell-side protective film, and the moisture permeability of the first protective film Is lower than the water vapor transmission rate of the second protective film.
2) The difference in moisture permeability measured under the condition of 60 ° C. and 95% RH between the first protective film and the second protective film is 200 to 2000 g / m ² · 24 hr, according to 1) Polarizer.
3) The first and second protective films are the same type of polymer substrate film, and the difference in moisture permeability between the first and second protective films is caused by the type and / or amount of the additive. The polarizing plate as described in 1) or 2) above.
4) The polarizing plate according to any one of 1) to 3), wherein the first and second protective films are cellulose acylate films.
5) The first and second protective films are cellulose acylate films, and the difference in moisture permeability between the first and second protective films is caused by the type of cellulose acylate. ) Or 2).
6) The polarizing plate according to any one of 1) to 5), wherein the first protective film has a moisture permeability of 250 to 1000 g / m ² · 24 hr measured at 60 ° C. and 95% RH. .
7) The polarizing plate according to any one of 1) to 6), wherein the second protective film has a moisture permeability of 500 to 5000 g / m ² · 24 hr measured under conditions of 60 ° C. and 95% RH. .
8) The in-plane retardation Re at 25 ° C. and 60% RH of the second protective film is 60 nm or more and 200 nm or less, and the thickness direction retardation Rth is 100 nm or more and 400 nm or less. Polarizer.
9) The polarizing plate according to any one of 1) to 8), wherein the in-plane retardation Re and the thickness direction retardation Rth of the second protective film at 25 ° C. and 60% RH satisfy the following formulas (I) and (II): .
(I) 0 ≦ Re ₍₆₃₀₎ ≦ 10 and | Rth ₍₆₃₀₎ | ≦ 25
(II) | Re ₍₄₀₀₎ −Re ₍₇₀₀₎ | ≦ 10 and | Rth ₍₄₀₀₎ −Rth ₍₇₀₀₎ | ≦ 35
[In the formula, Re ₍ λ ₎ is an in-plane retardation measurement value (unit: nm) at a wavelength λnm, and Rth ₍ λ ₎ is a thickness direction retardation measurement value (unit: nm) at a wavelength λnm. ]
10) The thickness of the first and second protective films is 40 μm or more and 120 μm or less, and the ratio of the thickness of the first protective film and the second protective film is 0.5 or more and 2 or less 1) To 9).
11) A polarizing plate provided with an adhesive layer on the polarizing plate according to any one of 1) to 10).
12) The polarizing plate according to any one of 1) to 11), wherein an antiglare layer is provided on the first protective film.
13) The polarizing plate according to any one of 1) to 12), which has a reflective layer or a transflective layer.
14) The polarizing plate according to any one of 1) to 13), which has a retardation layer or a λ / 4 layer.
15) The polarizing plate according to any one of 1) to 14), which has a viewing angle compensation layer.
16) The polarizing plate according to any one of 1) to 15), which has a brightness enhancement layer.
17) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to any one of 1) to 16).
18) The liquid crystal display device according to 17), wherein the liquid crystal cell is a TN mode liquid crystal cell.
19) The liquid crystal display device according to 17), wherein the liquid crystal cell is an OCB mode liquid crystal cell.
20) The liquid crystal display device according to 17), wherein the liquid crystal cell is an IPS mode liquid crystal cell.
21) The liquid crystal display device according to 17), wherein the liquid crystal cell is a VA mode liquid crystal cell.

The inventor has succeeded in producing a polarizing plate excellent in durability against heat and humidity.
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, an IPS type, an HS type, and an IPS type. Can be used.

1. Configuration of Polarizing Plate First, a polarizer and a protective film constituting the polarizing plate of the present invention will be described.

(1) 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 generated 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 preferable. Can be used.

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. 2001-302817, and Japanese Patent Application Laid-Open No. 2002-144401.

  The degree of crystallinity of the PVA film is not particularly limited. However, in order to reduce the average crystallinity (Xc) of 50 to 75% by weight and the in-plane hue variation described in Japanese Patent No. 3251073, JP-A-2002 A PVA film having a crystallinity of 38% or less described in JP-A-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 No. 2002-228835, in order to obtain a high degree of polarization while avoiding cutting during stretching of the PVA film, the birefringence of the PVA film is set to 0.002 or more and 0.01 or less. Alternatively, as described in JP-A-2002-060505, the value of (nx + ny) / 2-nz may be set to 0.0003 or more and 0.01 or less. The retardation Re (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 described in Japanese Patent No. 3021494, 5 μm described in Japanese Patent Application Laid-Open No. 2001-316492. The PVA film in which the above optical foreign matters are 500 or less per 100 cm ² , the PVA film in which the hot water cutting temperature spot in the TD direction of the film described in JP-A No. 2002-030163 is 1.5 ° C. or less, Further, a PVA film formed from a solution in which 1 to 100 parts by weight of a tri- or hexavalent polyhydric alcohol such as glycerin or a plasticizer described in JP-A 06-289225 is mixed by 15% by weight or more is used. 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-2002-236212, 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.

Dichroic molecule I ₃ ^- or 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 Plates” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p39-p45. PVA can be dipped in a liquid and / or boric acid aqueous solution and 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 C.I. I. Direct Red 37, Congo Red (C.I. Direct Red 28), C.I. I. Direct Violet 12, C.I. I. Direct Blue 90, C.I. I. Direct Blue 22, C.I. I. Direct Blue 1, C.I. I. Direct Blue 151, C.I. I. Benzidines such as Direct Green 1, C.I. I. Direct Yellow 44, C.I. I. Direct Red 23, C.I. I. Diphenylurea such as Direct Red 79, C.I. I. Stilbene series such as Direct Yellow 12, C.I. I. Dinaphthylamines such as Direct Red31, C.I. I. Direct Red 81, C.I. I. Direct Violet 9, C.I. I. Mention may be made of J acid systems such as Direct Blue 78. In addition, C.I. I. Direct Yellow 8, C.I. I. Direct Yellow 28, C.I. I. Direct Yellow 86, C.I. I. Direct Yellow 87, C.I. I. Direct Yellow 142, C.I. I. Direct Orange 26, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Orange 106, C.I. I. Direct Orange 107, C.I. I. Direct Red 2, C.I. I. Direct Red 39, C.I. I. Direct Red 83, C.I. I. Direct Red 89, C.I. I. Direct Red 240, C.I. I. Direct Red 242, C.I. I. Direct Red 247, C.I. I. Direct Violet 48, C.I. I. Direct Violet 51, C.I. I. Direct Violet 98, C.I. I. Direct Blue 15, C.I. I. DirectBlue 67, C.I. I. Direct Blue 71, C.I. I. Direct Blue 98, C.I. I. Direct Blue 168, C.I. I. Direct Blue 202, C.I. I. Direct Blue 236, C.I. I. Direct Blue 249, C.I. I. Direct Blue 270, C.I. I. Direct Green 59, C.I. I. Direct Green 85, C.I. I. Direct Brown 44, C.I. I. Direct Brown 106, C.I. I. Direct Brown 195, C.I. I. Direct Brown 210, C.I. I. Direct Brown 223, C.I. I. Direct Brown 224, C.I. I. Direct Black 1, C.I. I. Direct Black 17, C.I. I. Direct Black 19, C.I. I. Direct Black 54 and the like are further disclosed in JP-A-62-70802, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105, The dichroic dyes described in JP-A-1-265205 and JP-A-7-261024 can also 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. 2002-082222.

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 of the thickness of the polarizer to the thickness of the protective film described later is set to 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0 as described in JP-A-2002-174727. A range of 16 is also preferable.

(2) Protective 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.
Moreover, it is preferable that the both sides of the 1st and 2nd protective film are substantially the same resin as the protective film of this invention. The fact that they are substantially the same means that the main component uses the same resin, and the additives other than the main component may be the same or different.
Among these, it is preferable to use a cellulose ester film, and it is most preferable to use cellulose acylate on both sides. The cellulose acylate film used in the present invention will be described below.

[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. . Further, the degree of acetyl substitution of 2.50 or more and 2.86 or less described in JP 2001-356214 A or 2.75 or more and 2.86 or less described in JP 2001-226495 A is also preferable. Can be used. If it 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 61.5%.
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).
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.
In the present invention, cellulose acylates having two or more types of acyl groups described in JP-A-8-231761 and JP-A-2003-170492 can also be preferably used.

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.
Cellulose acetate obtained by a synthesis method 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 the cellulose acylate and the 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 dissolves 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, when 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.

  A cellulose acylate film is produced from the prepared cellulose acylate solution (dope) 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.

  Regarding the drying method in the solvent cast 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 Japanese Patent Publication No. 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.

  Two or more layers can be cast using the prepared cellulose acylate solution (dope) 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. You may produce a film, casting and laminating the solution containing a cellulose acylate, respectively. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. It can also be formed into a film 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 in a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solution is extruded simultaneously. 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 was in contact with the support surface to produce a 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 absorption 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 extrude a highly viscous solution onto the support at the same time, improving the flatness and improving the 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 addition amount exceeds 1% by mass, bleed-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, in these treatments, the temperature of the cellulose acylate film is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.

When using as a transparent protective film of 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 potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N, and in the range of 0.5 to 2.0N. More preferably it is. 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, it is preferable to use a contact angle method.

  Specifically, two kinds 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 between the tangent line drawn on the droplet and the film surface, The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

[Moisture permeability]
Any resin may be used for the protective film used in the polarizing plate of the present invention as long as the moisture permeability is different, but the first and second protective films may be the same type of polymer substrate film. preferable. More preferably, the difference in moisture permeability between the first and second protective films is caused by the type and / or amount of the additive.
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 protective film can be adjusted by various methods. Furthermore, 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 compounds represented by the following general formulas (I) to (III) can be particularly preferably used.
Next, the compound represented by formula (I) used in the present invention will be described in detail.
Formula (I)

In the general formula (I), R ²¹ , R ²² and R ²³ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms (for example, methyl, ethyl, propyl, isopropyl, butyl, amyl, Isoamyl), and at least one of R ²¹ , R ²² and R ²³ is particularly preferably an alkyl group having 1 to 3 carbon atoms (eg, methyl, ethyl, propyl, isopropyl). X ²¹ represents a single bond, —O—, —CO—, an alkylene group (preferably having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms such as methylene, ethylene, propylene) or an arylene group (preferably carbon). It is preferably a group having 6 to 24 atoms, more preferably 6 to 12. For example, it is preferably a divalent linking group formed from one or more groups selected from phenylene, biphenylene, naphthylene, -O-, A divalent linking group formed from one or more groups selected from an alkylene group or an arylene group is particularly preferable. Y ²¹ represents a hydrogen atom or an alkyl group (preferably having 2 to 25 carbon atoms, more preferably 2 to 20 carbon atoms. For example, ethyl, isopropyl, t-butyl, hexyl, 2-ethylhexyl, t-octyl, dodecyl, Cyclohexyl, dicyclohexyl, adamantyl), an aryl group (preferably having 6 to 24 carbon atoms, more preferably 6 to 18. For example, phenyl, biphenyl, terphenyl, naphthyl) or an aralkyl group (preferably having 7 to 7 carbon atoms). 30, more preferably 7 to 20. For example, benzyl, cresyl, t-butylphenyl, diphenylmethyl, triphenylmethyl) is preferable, and an alkyl group, aryl group, or aralkyl group is particularly preferable. Examples of the combination of -X ²¹ -Y ^21, preferably has a total carbon number of -X ²¹ -Y ²¹ is 0 to 40, more preferably 1 to 30, and most preferably from 1 to 25 .
Preferred examples of the compound represented by the general formula (I) are shown below, but the present invention is not limited to these specific examples.

Next, the compound represented by formula (II) will be described.
Formula (II)

In the general formula (II), R ¹ represents an alkyl group or an aryl group, and R ² and R ³ each independently represent a hydrogen atom, an alkyl group, or an aryl group. Further, the total number of carbon atoms of R ¹ , R ² and R ³ is particularly preferably 10 or more. As the substituent, a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are preferable, and an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are particularly preferable. Further, the alkyl group may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 6 to 25, and more preferably 6 to 20 (E.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclooctyl, nonyl, adamantyl, decyl, t-octyl, undecyl, Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred. As the aryl group, those having 6 to 30 carbon atoms are preferable, and those having 6 to 24 carbon atoms (for example, phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, triphenylphenyl) are particularly preferable.
Although the preferable example of a compound represented by general formula (II) is shown below, this invention is not limited to these specific examples.

Next, the compound of the general formula (III) used in the present invention will be described in detail.
General formula (III)

In the above general formula (III), X ² represents B, C—R (R represents a hydrogen atom or a substituent), N, P, P═O. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ are hydrogen atoms or substituents Represents.

X ² represents B, C—R (R represents a hydrogen atom or a substituent), N, P, P═O, and X ² is preferably B, C—R (R is preferably an aryl group, substituted) Or unsubstituted amino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, Mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom) and carboxyl group, more preferably aryl group, alkoxy group, aryloxy group, hydroxy group and halogen atom, still more preferably alkoxy A hydroxy group, particularly preferably a hydroxy group), N and P = O, more preferably C—R and N, and particularly preferably C—R.

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ are hydrogen atoms or substituents The substituent T described later can be applied as the substituent. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ are preferably alkyl groups, Alkenyl, alkynyl, aryl, substituted or unsubstituted amino, alkoxy, aryloxy, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, acylamino, alkoxycarbonylamino, aryloxycarbonyl Amino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine) Atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group , Hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having a carbon number of 1-30, more preferably 1-12. Examples of the heteroatom include a nitrogen atom, an oxygen atom, a sulfur atom, Specific examples include imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, etc.), and silyl groups, more preferably alkyl groups, aryl groups, substituted or unsubstituted. A substituted amino group, an alkoxy group and an aryloxy group are preferred, and an alkyl group, an aryl group and an alkoxy group are more preferred. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

  The aforementioned substituent T will be described below. Examples of the substituent T include an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms such as methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably carbon number). 2 to 8, for example, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably carbon number). 2-8, for example, propargyl, 3-pentynyl, etc.), aryl groups (preferably having 6-30 carbon atoms) More preferably, it has 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl and the like, and a substituted or unsubstituted amino group (preferably having 0 to 0 carbon atoms). 20, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, etc.), an alkoxy group (preferably having a carbon number) 1 to 20, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, such as methoxy, ethoxy, butoxy, etc.), an aryloxy group (preferably 6 to 20 carbon atoms, more Preferably it has 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyloxy, 2-naphthyloxy and the like. An acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include acetyl, benzoyl, formyl, and pivaloyl). An alkoxycarbonyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, etc.), an aryloxycarbonyl group ( Preferably it has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 10 carbon atoms, and examples thereof include phenyloxycarbonyl, etc.), an acyloxy group (preferably 2 to 20 carbon atoms, More preferably, it has 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms. Nzoyloxy and the like. ), An acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino), alkoxycarbonylamino group (Preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino), aryloxycarbonylamino group (preferably having carbon number) 7 to 20, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino, and the like, and sulfonylamino groups (preferably 1 to 20 carbon atoms, more preferably Has 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. And sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl and methylsulfamoyl). , Dimethylsulfamoyl, phenylsulfamoyl, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as carbamoyl). , Methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc.), an alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio, Ethylthio etc.), arylthio group (preferably Has 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, and a sulfonyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl, tosyl, etc.), sulfinyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably Has 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.), ureido group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms). For example, ureido, methylureido, phenylureido, etc.), phosphoric acid amide group (preferably having 1 to 20 carbon atoms) More preferably, it is C1-C16, Most preferably, it is C1-C12, for example, diethyl phosphoric acid amide, phenylphosphoric acid amide etc. are mentioned. ), Hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, Heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom, a sulfur atom, specifically, for example, imidazolyl, pyridyl, quinolyl, furyl, piperidyl , Morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, etc.), silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, and particularly preferably 3 to 24 carbon atoms). For example, trimethylsilyl, triphenylsilyl, etc.) . These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

  Hereinafter, the compound represented by formula (III) will be described in detail with specific examples, but the present invention is not limited to the following specific examples.

  The compounds represented by the general formulas (I) to (III) are used in an amount of 0.01 to 20 parts by mass, preferably 0.5 to 10 parts by mass, with respect to 100 parts by mass of the cellulose ester. By using the compound within this range, the retardation and water permeability of the film can be appropriately controlled. When the amount is less than 0.01 parts by mass, the retardation and water permeability are not sufficiently controlled. Use exceeding 20 parts by mass makes it difficult for the additive to be compatible with the cellulose ester and makes it easy to crystallize in the film.

In addition, a discotic compound disclosed in JP-A No. 2001-166144 can be particularly preferably used.
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.

The moisture permeability can also be lowered by stretching in the transport direction and / or the width direction during film formation and by densely aligning the molecular chains of cellulose acylate.
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-2842211, JP-A-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 while holding the width of the film 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 5 to 50%, more preferably in the range of 10 to 40%, and in the range of 15 to 35%. Most preferably.

  It is also possible to reduce the moisture permeability by treating the cellulose acylate film at a high temperature to increase the crystallinity. The treatment needs to be performed at such a temperature and time that the volatilization of the low molecular weight compound and the thermal decomposition of the cellulose acylate film itself are not problematic. The treatment temperature is preferably from 100 ° C. to 260 ° C., more preferably from 140 ° C. to 240 ° C. The treatment time is preferably from 5 minutes to 2 hours, more preferably from 10 minutes to 1 hour.

The moisture permeability measured under the condition of 60 ° C. and 95% RH of the cellulose acylate film used for the first protective film of the present invention is preferably 250 g / m ² · 24 hr to 1000 g / m ² · 24 hr, preferably 400 g / m. ² · 24 hr or more 1000g / m ² · 24hr or less is more preferable. In addition, the moisture permeability of the cellulose acylate film used in the second protective film of the present invention measured at 60 ° C. and 95% RH is preferably 500 g / m ² · 24 hr to 5000 g / m ² · 24 hr, preferably 700 g. / M ² · 24 hr or more and 3000 g / m ² · 24 hr or less is more preferable.
Further, the difference in moisture permeability measured under the condition of 60 ° C. and 95% RH between the air interface side protective film and the liquid crystal cell side protective film is preferably 200 g / m ² · 24 hr or more and 2000 g / m ² · 24 hr, preferably 250 g / m ^2. · More preferably 24 hr or more and 1500 g / m ² · 24 hr. If this difference is too large, the curling of the polarizing plate becomes large, which causes a problem when the polarizing plate is bonded to the liquid crystal cell.

  [Film retardation]

  In the present invention, the air interface side protective film having any retardation value can be used. On the other hand, the liquid crystal cell-side protective film having various retardation values can be used depending on the application.

  It is also possible to use the liquid crystal cell side protective film itself as an optically anisotropic film. In this case, for the OCB mode, Re is preferably 10 to 100, and 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 60 to 2000, more preferably 60 to 150. Rth is preferably from 100 to 400, more preferably from 150 to 300.
For TN, Re is preferably 0-50, more preferably 2-30. Rth is preferably 10-200, more preferably 30-150.

Moreover, it is also possible to use it as an optical compensation film by applying an optically anisotropic layer on the liquid crystal cell side protective film. In this case, as for the optical characteristics of the liquid crystal cell side protective film alone, Re is preferably 0 to 10 and more preferably 0 to 5 for IPS / VA mode. Rth is preferably 0-20, and more preferably 0-10.
In the OCB mode and the TN mode, an optically anisotropic layer can be applied on the liquid crystal cell-side protective film having the retardation value and used as an optical compensation film.

The birefringence (Δn: nx−ny) of the protective film is preferably in the range of 0.00 to 0.002 μm. The birefringence {(nx + ny) / 2−nz} in the thickness direction of the support film and the counter film is preferably in the range of 0.00 to 0.04.
Moreover, the thickness (dry film thickness) of the transparent protective film is 120 μm or less, preferably 20 to 110 μm, and more preferably 40 to 100 μm.

  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 °.

[Retardation raising agent]
In order to increase the retardation of the liquid crystal cell side protective film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent. Examples of the retardation increasing agent include aromatic compounds having at least two aromatic rings such as triazines (triphenyl-1,3,5-triazine, tri-m-tolyl-1,3,5-triazine, etc.). , Trans-1,4-cyclohexanedicarboxylic acid diesters (p-n-hexylphenol diester, pn-amylphenol diester, etc.).

Other specific examples are described in JP-A Nos. 2000-1111914, 2000-275434, pamphlet of International Publication No. 00/065384, and the like.
Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.
The molecular weight of the retardation increasing agent is preferably 300 to 800.

  When a cellulose acylate film is used as the liquid crystal cell-side protective film, the aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate.

[Retardation lowering agent]
The liquid crystal cell-side protective film can be lowered in retardation by an additive. The compounds of the general formulas (I) to (III) can be preferably used for this purpose.
When a cellulose acylate film is used as the liquid crystal cell-side protective film, the compounds of the general formulas (I) to (III) are used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate. . The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate.

[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 . 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, 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.

  The polarizing plate of this invention may have an adhesive layer, a separate film, and a protective film as a component other than the above-mentioned polarizer and protective film.

2. Next, the manufacturing process of the polarizing plate of the present invention will be described.
The manufacturing process of the polarizing plate in the present invention comprises a polarizer swelling process, a polarizer dyeing process, a polarizer hardening process, a polarizer stretching process, a polarizer drying process, a protective film bonding process, and a drying process after bonding. It is preferable. 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 weight 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 to 2 g / l, potassium iodide is 30 to 120 g / l, the weight ratio of iodine and potassium iodide is 30 to 120, dyeing time is 30 to 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 crosslinking agent, those described in US Reissued Patent No. 232897 can be used. As described in Japanese Patent No. 3357109, a polyvalent aldehyde is used as a crosslinking agent in order to improve dimensional stability. Although it can be used, 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 to 100 g / l, potassium iodide is 1 to 120 g / l, zinc chloride is preferably 0.01 to 10 g / l, hardening time is preferably 10 to 1200 seconds, and liquid temperature is preferably 10 to 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 50 ° C is preferable.

  For the stretching step, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515 or a tenter method as described in JP-A-2002-86554 can be preferably used. A preferable draw ratio is 2 times or more and 12 times or less, and 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 No. 2002-040256 (polarizer film thickness after protective film bonding / raw film thickness) × (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 ≦ (protection) described in JP-A-2002-040247 It is also preferable to set the polarizer width at the time of film bonding / the width of the polarizer when leaving the final bath) ≦ 0.95.

  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, a heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or it is described in Japanese Patent Laid-Open Nos. 07-325215 and 07-325218. As described above, aging in an atmosphere in which the temperature and humidity are controlled can be preferably performed.

  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-2002-267839, 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.

Element content in the polarizer, iodine 0.1 to 3.0 g / m ^2, boron 0.1 to 5.0 g / m ^2, potassium 0.1 to 2.0 g / m ^2, zinc 0-2. It is preferably 0 g / m ² . Further, the potassium content may be 0.2% by weight 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 weight%-0.5 weight% currently made.

  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 in any of the dyeing process, the stretching process, and the hardening process. It is also possible to use and contain at least one compound selected from organic titanium compounds and organic zirconium compounds. A dichroic dye may be added to adjust the hue of the polarizing plate.

3. Characteristics of polarizing plate (1) Transmittance and degree of polarization 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 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 the following formula based on JISZ8701.

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

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

  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 Application Laid-Open No. 2001-091736, and the relationship between parallel transmittance and orthogonal transmittance is disclosed in Japanese Patent Application 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 420 to 700 nm is 3 or less, and the light wavelength is 420 to 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.

Here, X ₀ , Y ₀ , 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, and the standard light D _In the case of ₆₅ , X ₀ = 95.045, Y ₀ = 100, and Z ₀ = 108.892.

The preferable range of a ^* for a single polarizing plate is −2.5 to 0.2, and more preferably −2.0 to 0. 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. A preferable range of b ^* of parallel transmitted light of the two polarizing plates is 2.0 or more and 8 or less, and 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 are 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 to set the transmittance ratio and the xy chromaticity difference in the range described in Japanese Patent Laid-Open Nos. 2001-166135 and 2001-166137 when the light is incident at an angle of. Further, as described in JP-A-10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminated body arranged in a crossed Nicols state and the light in the direction inclined by 60 ° from the normal line of the laminated body The ratio (T ₆₀ / T ₀ ) with the transmittance (T ₆₀ ) is 10000 or less, or as described in JP-A No. 2002-139625, the polarizing plate has an arbitrary range from the normal to an elevation angle of 80 degrees. When natural light is incident at an angle, 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 described in JP-A-08-248201. It is also preferable that the difference in luminance of transmitted light at an arbitrary 1 cm distance on the film 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., 90% RH and 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 No. 06-167611, the shrinkage rate after leaving at 80 ° C. for 2 hours is 0.5% or less, or on both surfaces of the glass plate. The x- and y-values after leaving the crossed Nicol-arranged polarizing plate laminate in an atmosphere of 69 ° C. for 750 hours are within the range described in JP-A-10-068818, or 80 ° C. and 90% RH. the change in spectral intensity ratio of the 105 cm ^-1 and 157cm ^-1 by Raman spectroscopy after 200 hours standing process in an atmosphere of a range described in JP-a-08-094834 and JP 09-197127 It can also be preferably performed.

(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. Further, 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, or the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85 as described in Japanese Patent Application Laid-Open No. 04-204907, or higher iodine ions of I ₃ and I ₅ It is also preferable to set the degree of orientation to 0.8 to 1.0 as the 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 Japanese Unexamined Patent Publication No. 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 polarizing axis direction of the polarizing plate are In addition, it can be preferably carried out within a range of ± 0.6% or by setting the moisture content of the polarizing plate to 3% by weight or less as described in JP-A-2002-090546. Further, as described in JP 2000-249832 A, the surface roughness in the direction perpendicular to the stretching axis is 0.04 μm or less based on the center line average roughness, or in JP 10-268294 A As described, the refractive index n ₀ in the transmission axis direction is made larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film is within the range described in JP-A-10-111411. Can also be preferably performed.

4). Functionalization of Polarizing Plate The polarizing plate of the present invention is a retardation plate, a λ / 4 plate, a reflective layer, a semi-transparent plate for application to an LCD viewing angle widening film (viewing angle compensation layer), a reflective or transflective LCD. Composite with optical layer having functional layers such as transmissive layer, antireflection film for improving visibility of display, brightness enhancement film (brightness enhancement layer), hard coat layer, forward scattering layer, antiglare (antiglare) layer It is preferably used as a functionalized polarizing plate.

  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. As a protective film on one side of the polarizing plate, a functional optical film and a polarizer may be bonded via an adhesive (FIG. 1A), or it adheres to a polarizing plate provided with protective films on both sides of the polarizer. A functional optical film may be bonded through an agent (FIG. 1B). In the former case, any transparent protective film can be used as the other protective film. 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-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, the 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-6-6 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 transparent polymer film. The viewing angle widening film may be used by being bonded to a polarizing plate via an adhesive, but SID'00 Dig. , P551 (2000), it is particularly preferable from the viewpoint of thinning that it is used also as one of the protective films of the polarizer.

  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 molecules have a disk-shaped core portion and 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.

  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 a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) dissolved in a solvent, coated on the alignment layer, dried, and then discotic nematic. After heating to the phase formation 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, additives for controlling the orientation on the air interface side such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), fluorine-containing triazine compounds are cellulose acetate, cecellulose acetate. Mention may be made of polymers such as propionate, 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, and 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 transparent substrate film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer And 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, it has an optical axis in a direction intersecting the plate surface. It is laminated with a retardation plate exhibiting anisotropy in birefringence, or the dimensional change rate of the protective film and the optically anisotropic layer is substantially the same as described in JP-A-2002-258052. Can also be preferably performed. Further, as described in JP 2000-258632 A, the moisture content of the polarizing plate bonded to the viewing angle widening film is set to 2.4% or less, or described in JP 2002-267839 A. It is also preferable to make the contact angle with water on the surface of the viewing angle widening film 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 liquid crystal cells 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. For such a viewing angle widening film, 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 disk-shaped compound is a substrate. In order to prevent the deterioration of the orthogonal transmittance in the oblique direction of the polarizing plate, the film in which the films arranged in parallel to each other, the stretched film having the same in-plane retardation value are laminated so that the slow axes are orthogonal, It is preferably used in combination with a laminate of films made of such rod-like compounds.

(2) λ / 4 plate The polarizing plate of the present invention can be used as a circularly polarizing plate laminated with a 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. “Retardation of approximately ¼ in the wavelength range of visible light” means that the longer the wavelength from 400 to 700 nm, the larger the retardation, and the retardation value Re ₍₄₅₀₎ measured at a wavelength of 450 nm is 80 to 125 nm. The retardation value Re ₍₅₉₀₎ measured at a wavelength of 590 nm satisfies a relationship satisfying the relationship of 120 to 160 nm. Re ₍₅₉₀₎ -Re ₍₄₅₀₎ more preferably from ≧ 5nm, Re ₍₅₉₀₎ is particularly preferably a -Re ₍₄₅₀₎ ≧ 10nm.

  The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied, but for example, described in JP-A-5-27118, JP-A-10-68816, and JP-A-10-90521. Λ / 4 plate in which a plurality of polymer films are laminated, λ / 4 plate obtained by stretching one polymer film described in WO00 / 65384 pamphlet, WO00 / 26705 pamphlet, JP, A known λ / 4 plate such as a λ / 4 plate in which at least one optically anisotropic layer is provided on the polymer film described in JP-A No. 2000-284126 and JP-A No. 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 / 4 plate / 2 It is preferable to bond the plate so that the angle formed by the slow axis in the plane of the 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 a transparent support is preferably used. The In addition, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28, JP-A-2002-301783, and the like can also be preferably used. The refractive index of each layer satisfies the following relationship.

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

  As the transparent support used for the antireflection film, the transparent polymer film used for the protective film of the polarizing layer 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 JP-A-2001-40284. The compounds described in paragraph Nos. [0027] to [0028] and JP-A No. 2000-284102 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. And a low refractive index inorganic compound, organic fine particles described in paragraphs [0020] to [0038] of JP-A No. 11-3820, silane coupling agents, slip agents, surfactants, and the like are also preferably included. 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 particle surface with a surface treatment agent (silane coupling agent or the like: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds or (Organic metal coupling agent: JP-A No. 2001-310432, etc.), a core-shell structure with high refractive index particles as a core (JP-A No. 2001-166104, etc.), or a specific dispersant (eg, JP-A No. 11- No. 153703, U.S. Pat. No. 6,210,858, and JP-A-2002-27776069) can be used.

  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 pamphlets of International Publication No. 95/17691, International Publication No. 95/17692, International Publication No. 95/17699) and cholesteric liquid crystal systems (European patent applications) Publication No. 606940 and JP-A-8-271731 are 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, pamphlets of International Publication No. 97/32223, International Publication No. 97/32224, International Publication No. 97/32225, International Publication No. 97/32226, and Japanese Patent Laid-Open Nos. 9-274108 and 11- It is also preferable to use in combination with a brightness enhancement film of an anisotropic scattering system in which a positive intrinsic birefringent polymer and a negative intrinsic birefringent polymer are blended and uniaxially stretched as described in each publication of JP1741741. 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 protective film of the polarizing plate 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 transparent support in order to impart mechanical strength such as scratch resistance. Done. When the hard coat layer is applied to the above-described antireflection film, it is particularly preferable to provide it between the transparent 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 a specific constituent composition of the hard coat layer, for example, those described in JP-A-2002-144913, JP-A-2000-9908, WO 00/46617, etc. 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, Oxetane, OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, manufactured by Toagosei Co., Ltd.), etc. 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 forming irregularities on the film surface by adding fine particles (for example, JP-A No. 2000-271878), relatively large particles (particle size 0.05-2 μm). ) Is added in a small amount (0.1 to 50% by mass) (for example, Japanese Patent Application Laid-Open Nos. 2000-281410, 2000-95893, 2001-100004, and 2001). 281407, etc.), a method of physically transferring the uneven 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.

5). Next, a liquid crystal display device using the polarizing plate of the present invention will be described. FIG. 2 is an example of a liquid crystal display device in which the polarizing plate of the present invention is used.

  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 transparent 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 is different in the alignment state 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 Electron), ECB (Etc. However, the polarizing plate of the present invention can be used in any display mode regardless of the transmissive and reflective types.

  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 23 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 viewing angle widening. It may be arranged as a plate.

  When used as a transmission type, a cold cathode or hot cathode fluorescent tube, or a backlight having a light emitting diode, field emission element, or 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 acylate film (1) (3) (4) (6))
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acylate solution A.

<Composition of cellulose acylate solution A>
Cellulose acetate having an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 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

The following composition was put into another mixing tank and stirred while heating to dissolve each component to prepare additive solutions B-1 to B-4.
<Additive solution B-1 to B-4 composition>

<Preparation of cellulose acylate film (1)>
A dope was prepared by adding cellulose acylate solution A to 474 parts by mass and 20 parts by mass of additive solution B-1 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. In this state, the film 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 the heat processing apparatus, and produced the 80-micrometer-thick cellulose acylate film (1).

<Production of cellulose acylate films (3), (4), (6)>
The cellulose acylate films (3), (4) and (6) were prepared in the same manner as the cellulose acylate film (1) except that the additive solution was changed to the one shown in Table 2 in the preparation of the cellulose acylate film (1). Produced.

[Example 2]
(Production of cellulose acylate film (8) (10) (11) (13) (15))
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acylate solution B was prepared.

<Composition of cellulose acylate solution B>
Cellulose acetate having an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.0 parts by weight Biphenyl diphenyl phosphate (plasticizer) 4.0 parts by weight Methylene chloride (first solvent) 402 parts by weight Methanol (No. 1) 2 solvents) 60 parts by mass

<Preparation of cellulose acylate film (8)>
A dope was prepared by adding 573 parts by mass of cellulose acylate solution B and 24 parts by mass of additive solution B-1 and stirring sufficiently.
The obtained dope was cast using a band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 70 ° C. for 1 minute, and the film was peeled off from the band. Next, the film was dried with a drying air at 140 ° C. for 10 minutes to prepare a cellulose acylate film (8) having a residual solvent amount of 0.3% by mass and a thickness of 80 μm.

<Production of Cellulose Acylate Film (10), (11), (13)>
The cellulose acylate films (10), (11), (13) were prepared in the same manner as the cellulose acylate film (8) except that the additive solution and thickness were changed to those shown in Table 2 in the production of the cellulose acylate film (8). ) Was produced.

<Preparation of cellulose acylate film (15)>
In the production of the cellulose acylate film (10), the cellulose acetate of the cellulose acylate solution B was changed to cellulose acetate propionate having an acetylation degree of 1.80 and a propionylation degree of 0.90 (cellulose acylate solution C) In the same manner, a cellulose acylate film (15) was produced.

[Example 3]
(Preparation of cellulose acylate film (16))
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution D.

<Composition of cellulose acylate solution D>
Cellulose acylate with a degree of acetylation of 1.80 and a degree of propionylation of 0.90
100 parts by weight Triphenyl phosphate (plasticizer) 9.0 parts by weight Ethylphthalyl ethyl glycolate (plasticizer) 3.5 parts by weight Methylene chloride (first solvent) 442 parts by weight Ethanol (second solvent) 20 parts by weight

<Preparation of matting agent solution>
The following composition was charged into a disperser and stirred to dissolve each component to prepare a matting agent solution.

――――――――――――――――――――――――――――――――――
Matting agent composition ――――――――――――――――――――――――――――――――――
Silica particles having an average particle diameter of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2.0 parts by mass Methylene chloride (first solvent) 83.0 parts by mass Ethanol (second solvent) 4.7 parts by mass Cellulose acylate solution C 10.3 parts by mass ――――――――――――――――――――――――――――――――――

<Preparation of UV absorber solution>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare an ultraviolet absorber solution.

――――――――――――――――――――――――――――――――――
UV absorber solution composition ――――――――――――――――――――――――――――――――――
UV absorbent C 14.0 parts by weight UV absorbent D 6.0 parts by weight Methylene chloride (first solvent) 64.4 parts by weight Ethanol (second solvent) 2.7 parts by weight Cellulose acylate solution D 12.8 parts by weight Department ――――――――――――――――――――――――――――――――――

  94.5 parts by mass of the cellulose acylate solution D, 1.3 parts by mass of the matting agent solution, and 3.4 parts by mass of the ultraviolet absorber solution were mixed after filtration, and cast using a band casting machine. After peeling the film from the band with a residual solvent content of 31%, and using the tenter to stretch the film at a temperature of 160 ° C. at a stretching time of 5 seconds and a stretching speed of 6.0% / second, and then stretching it to 130%. , And was held at 140 ° C. for 30 seconds. The residual solvent content at the start of stretching was 15%. Thereafter, the clip was removed and dried at 130 ° C. for 40 minutes to produce a cellulose acylate film (16). The resulting cellulose acylate film (16) had a residual solvent amount of 0.2%, a film thickness of 80 μm, Re of 40 nm, and Rth of 132 nm.

[Example 4]
(Saponification treatment)
The cellulose acylate film was immersed in an aqueous 1.5 N sodium hydroxide solution at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing tub, and neutralized using 0.1 N 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 acylate film was saponified.

[Example 5]
<Production of Polarizing Plate (1)>
A polarizer is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using a polyvinyl alcohol-based adhesive, a cellulose acylate film (6) prepared in Example 1 and saponified in Example 4 is used as a polarizer. Pasted on one side. The transmission axis of the polarizer and the slow axis of the cellulose acylate film were arranged in parallel.
Further, the cellulose acylate film (15) produced in Example 2 and saponified in Example 4 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 6]
<Preparation of polarizing plates (2) to (13)>
Polarizing plates (2) to (13) were produced in the same manner as the polarizing plate (1) of Example 5 with the cellulose acylate film combinations shown in Table 3.

[Example 7]
[Durability of polarizing plate]
The polarizing plate produced in this manner was attached to a glass plate so that the cellulose acylate film on the liquid crystal side was on the glass side and aged for 1000 hours at 60 ° C. and 90% RH, and then parallel transmittance and Shimadzu UV2200 spectrophotometer were used. The orthogonal transmittance was measured, and the degree of polarization was calculated by the above (Formula 4). Further, the curl strength of the polarizing plate was visually determined. The results are shown in Table 4.

  From this result, it is understood that the polarizing plate of the present invention has a small change in the degree of polarization with respect to heat and humidity, a small curl, and excellent durability.

[Example 8]
[Production and evaluation of TN liquid crystal display]
A pair of polarizing plates provided in a 20-inch liquid crystal display device (LC-20V1, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and the produced polarizing plates (1) to (13) are used instead. Then, the liquid crystal cell side cellulose acylate film was attached to the viewer side and the backlight side one by one via an adhesive so that the liquid crystal cell side film would be on the liquid crystal cell side (FIG. 3). 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. Under an environmental condition of a temperature of 25 ° C. and a relative humidity of 60%, the backlight was continuously turned on for 400 hours, and the entire black display state was visually observed in a dark room to evaluate light leakage. As a result, in the polarizing plate of the comparative example, frame-like light leakage was observed on the display screen of the liquid crystal display device, but not in the polarizing plate of the present invention.

[Example 9]
(Production of cellulose acylate film (21))
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acylate solution E was prepared.

<Composition of cellulose acylate solution E>
Acetylation degree 0.65, butyrylation degree 1.65
Cellulose acetate butyrate 100 parts by weight Methylene chloride (first solvent) 250 parts by weight Ethanol (second solvent) 80 parts by weight

<Preparation of matting agent solution>
The following composition was put into a disperser and stirred to dissolve each component to prepare a cellulose acetate solution.

――――――――――――――――――――――――――――――――――
Matting agent composition ――――――――――――――――――――――――――――――――――
Silica particles having an average particle size of 16 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2.0 parts by mass Methylene chloride (first solvent) 76.3 parts by mass Methanol (second solvent) 11.4 parts by mass Cellulose acylate solution E 10.3 parts by mass ――――――――――――――――――――――――――――――――――

<Preparation of retardation increasing agent solution>
The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-11 was prepared.
<Retardation raising agent solution composition>
Methylene chloride 64 parts by mass Ethanol 16 parts by mass Retardation increasing agent (I) 20 parts by mass

<Production of Cellulose Acylate Film (21)>
94.6 parts by mass of the cellulose acylate solution E, 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 acylate was 4.6%. The film was peeled off from the band with a residual solvent amount of 30%, and a 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 130 ° C. for 40 minutes to produce a cellulose acetate film. The resulting cellulose acetate film had a residual solvent amount of 0.1%, a film thickness of 85 μm, and a moisture permeability measured under the conditions of 60 ° C. and 95% RH was 1700 g / m ² · 24 hr. The in-plane retardation (Re) was 90 nm and the thickness direction retardation (Rth) was 190 nm.

Re and Rth were measured by the following method at 25 ° C. and 60% RH.
In-plane retardation Re (0) was measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). 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), and Re (−40). The refractive index nz was determined by calculation to determine the Rth retardation value. The measurement wavelength was 590 nm.

<Preparation of polarizing plate (21)>
The cellulose acylate film (6) and the cellulose acylate film (21) were saponified in the same manner as in Example 4.
Further, iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizer, and a saponified cellulose acylate film (6) 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 acylate film were arranged in parallel.
Further, a saponified cellulose acylate film (21) was attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive. In this way, a polarizing plate (21) was produced.

[Example 10]
[Production and evaluation of VA liquid crystal display]
The liquid crystal display device of FIG. 4 was produced. That is, the upper polarizing plate 30, the VA mode liquid crystal cell 31 (upper substrate, liquid crystal layer, lower substrate) and the lower polarizing plate 32 were laminated from the observation direction (upper), and a backlight light source was further arranged. In the following example, a commercially available polarizing plate (HLC2-5618) is used for the upper polarizing plate, and the polarizing plate of the present invention is used for the lower polarizing plate.

<Production of liquid crystal cell>
The liquid crystal cell has a cell gap between substrates of 3.6 μm, and a liquid crystal material having negative dielectric anisotropy (“MLC6608”, manufactured by Merck & Co., Inc.) is dropped and sealed between the substrates. Prepared by forming a layer. The retardation of the liquid crystal layer (that is, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn) was set to 300 nm. The liquid crystal material was aligned so as to be vertically aligned.

A commercially available super high contrast product (HLC2-5618 manufactured by Sanlitz Co., Ltd.) is used for the upper polarizing plate of the liquid crystal display device (FIG. 4) using the vertical alignment type liquid crystal cell, and Example 9 is used for the lower polarizing plate. The polarizing plate (21) prepared in step 1 was observed on the viewer side and the backlight side via an adhesive so that the cellulose acylate film (21) was on the liquid crystal cell side and the cellulose acylate film (6) was on the air interface side. Affixed to each. The crossed Nicols were arranged so that the transmission axis of the polarizing plate on the viewer side was in the vertical direction and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction.
It has been found that the liquid crystal display device of the present invention has excellent display quality because light leakage is small even when continuously lit under high humidity.

[Example 11]
(Production of cellulose acylate film (31))
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acylate solution F was prepared.

<Cellulose acylate solution F composition>
Acetylation degree 1.0, propynylation degree 1.95
Cellulose acetate propionate 100 parts by weight Methylene chloride (first solvent) 250 parts by weight Ethanol (second solvent) 80 parts by weight Triphenylformate 6 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight

<Preparation of matting agent solution>
The following composition was put into a disperser and stirred to dissolve each component to prepare a cellulose acetate solution.

――――――――――――――――――――――――――――――――――
Matting agent composition ――――――――――――――――――――――――――――――――――
Silica particles having an average particle size of 16 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2.0 parts by mass Methylene chloride (first solvent) 76.3 parts by mass Methanol (second solvent) 11.4 parts by mass Cellulose acylate solution E 10.3 parts by mass ――――――――――――――――――――――――――――――――――

<Preparation of UV absorber solution>
The following composition was put into another mixing tank and stirred while heating to dissolve each component to prepare an ultraviolet absorber solution.
――――――――――――――――――――――――――――――――――
UV absorber solution composition ――――――――――――――――――――――――――――――――――
Methylene chloride 64 parts by weight Ethanol 16 parts by weight UV absorber C 3 parts by weight UV absorber D 6 parts by weight ――――――――――――――――――――――――――― ―――――――

<Preparation of cellulose acylate film (31)>
94.6 parts by mass of the cellulose acylate solution F, 1.3 parts by mass of the matting agent solution, and 4.1 parts by mass of the ultraviolet absorber solution were mixed after filtration, and cast using a band casting machine. The film was peeled off from the band with a residual solvent amount of 40%, and the film with a residual solvent amount of 13% by mass was stretched transversely at a stretch ratio of 4% using a tenter under the condition of 100 ° C. Hold at 30 ° C. for 30 seconds. Thereafter, the clip was removed and dried at 130 ° C. for 40 minutes to produce a cellulose acetate film. The resulting cellulose acetate film had a residual solvent amount of 0.15%, a film thickness of 80 μm, and a moisture permeability measured under the conditions of 60 ° C. and 95% RH was 2000 g / m ² · 24 hr.
The in-plane retardation (Re) was 0.5 nm and the thickness direction retardation (Rth) was −1 nm.

<Preparation of Polarizing Plate 31>
The cellulose acylate film (1) and the cellulose acylate film (31) were saponified in the same manner as in Example 4.
Further, iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizer, and a saponified cellulose acylate film (6) 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 acylate film were arranged in parallel.
Further, a saponified cellulose acylate film (31) was attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive. In this way, a polarizing plate (31) was produced.

[Evaluation of mounting on IPS liquid crystal display]
An optical compensation film uniaxially stretched on the cellulose acylate film (31) was bonded to the polarizing plate (31) to give 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. The in-plane retardation Re of the optical compensation film was 270 nm, the retardation Rth in the thickness direction was 0 nm, and the Nz factor was 0.5.
The cellulose acylate of the polarizing plate (31) in the order of the laminate of the polarizing plate (31) of the present invention and the optical compensation film, the IPS liquid crystal cell, and the polarizing plate (31) of the present invention produced as described above. A display device was prepared in which the film (31) was placed on the liquid crystal side and the cellulose acylate film (6) was on the air interface side so as to be superimposed from above (FIG. 5). 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). ). As the liquid crystal cell, electrode and substrate, those conventionally used as IPS can be used as they are. The alignment of the liquid crystal cell is horizontal alignment, and the liquid crystal has a positive dielectric anisotropy, and those developed and marketed for IPS liquid crystals can be used. 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.
It has been found that the liquid crystal display device manufactured as described above is preferable because light leakage is small even when continuously lit under high humidity.

It is a conceptual diagram of the structural example which combined the polarizing plate and the functional optical film. It is explanatory drawing which shows an example of the liquid crystal display device in which a polarizing plate is used. It is a conceptual diagram which shows an example of the liquid crystal display device of this invention which has arrange | positioned the polarizing plate of this invention on both sides of a liquid crystal cell. It is a conceptual diagram which shows an example of the liquid crystal display device of this invention which has arrange | positioned the polarizing plate of this invention in the backlight side of the liquid crystal cell. FIG. 4 is a conceptual diagram showing an example of the liquid crystal display device of the present invention, in which the optical compensation film is laminated on the observer-side polarizing plate in the arrangement of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b Protective film 2 Polarizer 3 Functional optical film 4 Adhesive layer 11 Upper polarizing plate 12 Upper polarizing plate absorption axis 13 Upper optical anisotropic layer 14 Upper optical anisotropic layer orientation control direction 15 Liquid crystal cell upper electrode Substrate 16 Upper substrate orientation control direction 17 Liquid crystal layer 18 Liquid crystal cell lower electrode substrate 19 Lower substrate orientation control direction 20 Lower optical anisotropic layer 21 Lower optical anisotropic layer orientation control direction 22 Lower polarizing plate 23 Lower polarizing plate absorption axis 30 Upper polarizing plate 31 Liquid crystal cell 32 Lower polarizing plate 33 Polarizer 34 First protective film (air interface side)
35 Second protective film (liquid crystal cell side)
36 Protective film 37 Optical compensation film

Claims (15)

  In the polarizing plate in which the first protective film, the polarizer, and the second protective film are laminated in this order, the second protective film is a liquid crystal cell-side protective film, and the moisture permeability of the first protective film is the first. A polarizing plate characterized by being lower than the moisture permeability of the protective film of No. 2. 2. The polarized light according to claim 1, wherein a difference in moisture permeability measured between 60 ° C. and 95% RH between the first protective film and the second protective film is 200 to 2000 g / m ² · 24 hr. Board.   The first and second protective films are the same type of polymer substrate film, and the difference in moisture permeability between the first and second protective films is caused by the type and / or amount of the additive. The polarizing plate according to claim 1, wherein:   The first and second protective films are cellulose acylate films, and the difference in moisture permeability between the first and second protective films is caused by the type of cellulose acylate. Or the polarizing plate of 2. 5. The polarizing plate according to claim 1, wherein the first protective film has a moisture permeability of 250 to 1000 g / m ² · 24 hr measured under conditions of 60 ° C. and 95% RH. 6. The polarizing plate according to claim 1, wherein the second protective film has a moisture permeability of 500 to 5000 g / m ² · 24 hr measured under conditions of 60 ° C. and 95% RH.   The polarizing plate according to claim 1, wherein the in-plane retardation Re of the second protective film at 25 ° C. and 60% RH is 60 nm or more and 200 nm or less, and the thickness direction retardation Rth is 100 nm or more and 400 nm or less. . The polarizing plate according to claim 1, wherein the in-plane retardation Re and the thickness direction retardation Rth of the second protective film at 25 ° C. and 60% RH satisfy the following formulas (I) and (II).
(I) 0 ≦ Re ₍₆₃₀₎ ≦ 10 and | Rth ₍₆₃₀₎ | ≦ 25
(II) | Re ₍₄₀₀₎ −Re ₍₇₀₀₎ | ≦ 10 and | Rth ₍₄₀₀₎ −Rth ₍₇₀₀₎ | ≦ 35
[In the formula, Re ₍ λ ₎ is an in-plane retardation measurement value (unit: nm) at a wavelength λnm, and Rth ₍ λ ₎ is a thickness direction retardation measurement value (unit: nm) at a wavelength λnm. ]   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 first protective film.   The polarizing plate according to claim 1, comprising a reflective layer or a transflective layer.   The polarizing plate according to claim 1, comprising a retardation layer or a λ / 4 layer.   It has a viewing angle compensation layer, The polarizing plate in any one of Claims 1-12 characterized by the above-mentioned.   It has a brightness improvement layer, The polarizing plate in any one of Claims 1-13 characterized by the above-mentioned.   A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to claim 1.

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