JP2006247954A - Functional film, polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functional film of low moisture permeability and a polarizing plate of low change in transmittance and the degree of polarization caused by heat or humidity and to provide a liquid crystal display device having a high display grade at a wide visual field angle without causing a problem such as a light leak or the like by using a polarizing plate, wherein a retardation film and a protective film of low moisture permeability are arranged on both sides of a polarizer, in the liquid crystal display device. <P>SOLUTION: The functional film contains a cellulose acylate film of which the elastic modulus under a 25°C/60% RH condition is 3,800 N/mm<SP>2</SP>or above in either the width direction or longitudinal direction of the film and the water content under the 25°C/80% RH condition is 2.9 mass% or below and the low-moisture permeable cured layer provided at least on one side of the cellulose acylate film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

The liquid crystal display device is increasingly used year by year as an image display device with small power consumption and a small space. Conventionally, the large viewing angle dependence of images has been a major drawback of liquid crystal display devices, but in recent years, high viewing angle liquid crystal modes such as VA mode and IPS mode have been put into practical use. The demand for liquid crystal display devices is rapidly expanding even in markets where viewing angles are required.
Along with this, higher performance has begun to be required for retardation films and polarizing plates used in liquid crystal display devices. In particular, improvement of durability against temperature and humidity is a big problem for polarizing plates.
Particularly problematic in the durability test of the polarizing plate is a decrease in the degree of polarization, which is caused by the decomposition of iodine adsorbed on the polarizer by the action of water. It is known that reducing moisture permeability is effective. Since cellulose acylate, which is widely used as a protective film for polarizing plates, is a hydrophilic polymer and has high moisture permeability, a method for reducing moisture permeability by adding various hydrophobizing agents has been proposed. Patent Document 1 added rosin derivatives, Patent Document 2 added polyhydric alcohol esters having an aromatic ring or cycloalkyl ring in the molecule and glycolates having an aromatic ring or cycloalkyl ring in the molecule. A method for reducing humidity is disclosed.
JP 2002-146044 A JP 2003-232920 A

  However, in these methods, the moisture permeability can be reduced by adding a hydrophobizing agent up to a certain addition amount, but even if the addition amount is further increased, the decrease in the moisture permeability reaches its peak, and a sufficient improvement effect cannot be obtained. there were.

An object of the present invention is to provide a functional film having a low moisture permeability and 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 use a polarizing plate in which a retardation film and a protective film having low moisture permeability are arranged on both sides of a polarizer in a liquid crystal display device, so that a wide range of problems can be achieved without causing problems such as light leakage. It is an object to provide a liquid crystal display device with high viewing quality at a viewing angle.

As a result of intensive studies by the inventors, the moisture permeability of the cellulose acylate film is governed by two factors: (1) adsorption of water onto the film, and (2) diffusion of water in the film. The compounds disclosed in Patent Documents 1 and 2 have the effect of reducing the adsorption of water on the film of (1), but because of the large plasticizing effect, the diffusion of water in the film of (2) is reversed. I found out that it would be bigger.
Furthermore, the present inventor improved both of the above factors (1) and (2) by adding a compound having at least one hydrogen bonding hydrogen donating group in the molecule and having high hydrophobicity. I found what I can do. On the other hand, it was found that the moisture permeability can be further reduced by providing the low moisture permeability cured layer on at least one surface, and the conclusion of the object of the present invention was reached.

That is, the present invention is as follows.
(1)
Cellulose reed having an elastic modulus at 25 ° C. and 60% RH of 3800 N / mm ² or more in at least one of the width direction and the longitudinal direction and a water content of 2.9 mass% or less at 25 ° C. and 80% RH A functional film comprising a rate film and a low moisture-permeable cured layer provided on at least one surface of the cellulose acylate film.
(2)
A cellulose acylate film formed by containing a low molecular compound having a molecular weight of 100 or more and 2000 or less and cellulose acylate, wherein one of the low molecular compounds has at least one hydrogen bonding hydrogen donating group And a mass average value of octanol-water partition coefficient (hereinafter referred to as logP) of the low molecular weight compound is at least one of the agent, the mass ratio of the low molecular weight compound to the cellulose acylate is 5% or more and 35% or less. A functional film comprising a cellulose acylate film of 4 or more and 12 or less and a low moisture-permeable cured layer provided on at least one surface of the cellulose acylate film.
(3)
The elastic modulus at 25 ° C. and 60% RH in at least one of the width direction and the longitudinal direction is 3800 N / mm ² or more, and the moisture content at 25 ° C. and 80% RH is 2.9% by mass or less, and A cellulose acylate film formed by containing a low molecular compound having a molecular weight of 100 or more and 2000 or less and cellulose acylate, wherein one of the low molecular compounds has at least one hydrogen-bonding hydrogen donating group. It is at least one hydrophobizing agent, the mass ratio of the low molecular compound to cellulose acylate is 5% or more and 35% or less, and the mass average value of the octanol-water partition coefficient (hereinafter logP) of the low molecular compound is 4 or more and 12 or less, and the cellulose acylate film is provided on at least one surface of the cellulose acylate film. Functional film which comprises a low moisture permeability cured layer.
(4)
The low moisture permeability cured layer is
A curable composition containing at least one compound selected from the compound represented by the following general formula (A) and the compound represented by the following general formula (B) is coated and dried on the cellulose acylate film. The functional film according to any one of (1) to (3) above, which is obtained by curing this.
Formula (A)

(Wherein R1 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 is an alkylene group or alkylene oxide group having 1 to 5 carbon atoms, R3 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is 1 or An integer of 2)
General formula (B)

(Wherein R1, R3 and n have the same meaning as in the above general formula (A))
(5)
The functional film according to any one of (1) to (4) above, wherein the ratio of the phosphoric acid compound to the cellulose acylate is 5% by mass or less.
(6)
The functional film according to any one of the above (1) to (5), wherein the crystallinity of the cellulose acylate film is from 3000 to 15000.
(7)
The water vapor permeability measured in accordance with JIS Z 0208 in an environment of 60 ° C. and 95% RH is 100 g / m ² · 24 hrs or more and 600 g / m ² · 24 hrs or less. The functional film in any one.
(8)
A polarizing plate in which a protective film is bonded to both sides of a polarizer, wherein at least one of the protective films is the functional film according to any one of (1) to (7). .
(9)
In the polarizing plate in which protective films are bonded to both sides of the polarizer, the protective film on one side is the functional film according to any one of the above (1) to (7), and the functional film sandwiching the polarizer A polarizing plate, wherein the opposite side is a retardation film.
(10)
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 described in (8) or (9) above.

  According to the present invention, it is possible to provide a functional film with low moisture permeability and a polarizing plate with small changes in transmittance and degree of polarization due to heat and humidity. Furthermore, by using the polarizing plate in which the retardation film of the present invention and the protective film having low moisture permeability are arranged on both sides of the polarizer in a liquid crystal display device, a wide viewing angle can be obtained without causing problems such as light leakage. Thus, a liquid crystal display device with high display quality can be provided.

  In the present specification, the description “(meth) acryloyl” represents the meaning of “at least one of acryloyl and methacryloyl”. The same applies to “(meth) acrylate”, “(meth) acrylic acid” and the like. In addition, when a numerical value represents a physical property value, a characteristic value, or the like, the description “(numerical value 1) to (numerical value 2)” means “(numerical value 1) or more and (numerical value 2) or less”.

Hereinafter, the present invention will be described in more detail.
First, the functional film of the present invention will be described.
The functional film of the present invention includes a cellulose acylate film and a low moisture permeability cured layer provided on at least one surface of the cellulose acylate film.
The cellulose acylate film is
The elastic modulus at 25 ° C. and 60% RH in at least one of the width direction and the longitudinal direction is 3800 N / mm ² or more, and the water content at 25 ° C. and 80% RH is 2.9% by mass or less,
And / or a cellulose acylate film formed by containing a low molecular compound having a molecular weight of 100 or more and 2000 or less and cellulose acylate, wherein one of the low molecular compounds has at least a hydrogen-bonding hydrogen donating group. And at least one hydrophobizing agent, wherein the mass ratio of the low molecular compound to cellulose acylate is 5% or more and 35% or less, and the mass average value of the octanol-water partition coefficient of the low molecular compound is 4 or more and 12 or less.

<Cellulose acylate film>
First, the component of the cellulose acylate film used for the functional film of the present invention will be described.
Hereinafter, cellulose acylate will be described first.
The acyl group of the cellulose acylate used in the present invention 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 2
. 7-2.95 are preferable, and 2.8-2.95 are more preferable. Moreover, the cellulose whose acetyl substitution degree described in Unexamined-Japanese-Patent No. 2001-356214 is 2.50 or more and 2.86 or less, and the acetyl substitution degree described in 2001-226495 is 2.75 or more and 2.86 or less. Acetate can also be preferably used. If the degree of acetyl substitution is too low, there is a problem that Re tends to be larger than a desired value due to the conveyance tension during 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. If it is 0.9 or more, variations in Re and Rth hardly occur. In addition, the value calculated according to ASTM D817 is adopted as 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 61.9%.
The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).
The viscosity average degree of polymerization (DP) of cellulose acylate is preferably 250 or more, and more preferably 290 or more.

In addition, the cellulose acylate used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably in the range of 1.0 to 1.7, more preferably in the range of 1.3 to 1.65, and in the range of 1.4 to 1.6. Most preferably.
As the cellulose acetate, [Synthesis Example 1] described in paragraph Nos. [0043] to [0044] of JP-A No. 11-5851, [Synthesis Example] described in paragraph Nos. [0048] to [0049] 2], and cellulose acetate obtained by the synthesis method of [Synthesis Example 3] described in paragraphs [0051] to [0052] can be used.

[Photoelasticity]
The photoelastic coefficient of the cellulose acylate is preferably 60 × 10 ⁻⁸ cm ² / N or less, and more preferably 20 × 10 ⁻⁸ cm ² / N. The photoelastic coefficient can be obtained by an ellipsometer.
[Glass-transition temperature]
The glass transition temperature of the cellulose acylate is preferably 120 ° C. or higher, more preferably 140 ° C. or higher. The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). Is obtained as an average value of.

[Hydrophobic agent]
Next, the hydrophobizing agent used for the cellulose acylate film will be described.
As the hydrophobizing agent, a compound having as high a hydrophobicity as possible is preferable because the plasticizing effect on cellulose acylate is small (without reducing the elastic modulus) and the water content reducing effect is large. However, if the hydrophobicity is too high, the compatibility with cellulose acylate is too bad, and problems such as bleeding out occur. Therefore, in the present invention, a hydrophobizing agent having at least one hydrogen bonding hydrogen donating group is used as the hydrophobizing agent. This is advantageous and preferable in terms of the trade-off between the low plasticity and the moisture content lowering effect and the prevention of bleeding out.
The hydrogen bondable hydrogen donating group is a functional group having a hydrogen atom and capable of forming a hydrogen bond between the hydrogen atom and another functional group having a high degree of electrical negativeity. As the functional hydrogen donating group, an amino group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a hydroxy group, a mercapto group, and a carboxyl group are preferable, and a hydroxy group, an acylamino group, a sulfonylamino group, and the like Functional groups are particularly preferred.

On the other hand, a phosphate ester compound generally used as a hydrophobizing agent is effective in terms of a hydrophobic effect, but is disadvantageous in terms of both the low plasticity and the moisture content lowering effect. The content is preferably low. In the present invention, the ratio of the phosphoric acid compound to cellulose acylate is preferably 5% by mass or less (5 parts by mass or less with respect to 100 parts by mass of cellulose acylate), more preferably 2% by mass or less, and substantially contained. Most preferably not.
Examples of the phosphate compounds include phosphate ester compounds, and 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 compounds such as dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), and diethylhexyl phthalate (DEHP). .
The molecular weight of the hydrophobizing agent used in the present invention is preferably from 250 to 2,000. Moreover, it is preferable that the boiling point is 260 degreeC or more. The boiling point can be measured using a commercially available measuring device (for example, TG / DTA100, manufactured by Seiko Electronics Industry Co., Ltd.).
Various compounds can be used as the hydrophobizing agent that lowers the water content without lowering the elastic modulus, but compounds represented by the following general formula (I) or (II) can be particularly preferably used.
Formula (I)

In the formula, R ¹ , R ² , and R ³ are each independently an alkyl group, an alkenyl group, an aromatic ring group, or a heterocyclic group.
Formula (II)

In the formula, X represents a substituted or unsubstituted amino group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto group, or carboxyl group.
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.

First, the compound represented by formula (I) will be described in detail.
R ¹ , R ² , and R ³ each independently represents an alkyl group, an alkenyl group, an aromatic ring group, or a heterocyclic group, and more preferably an aromatic ring or a heterocyclic ring. The aromatic ring represented by each of R ¹ , R ² and R ³ is preferably phenyl or naphthyl, and particularly preferably phenyl. R ¹ , R ² and R ³ may have a substituent on the aromatic ring or heterocyclic ring. Examples of substituents include halogen atoms, hydroxyl groups, cyano groups, nitro groups, carboxyl groups, alkyl groups, alkenyl groups, aryl groups, alkoxy groups, alkenyloxy groups, aryloxy groups, acyloxy groups, alkoxycarbonyl groups, alkenyls. Oxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamido group, carbamoyl group, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide Group, alkylthio group, alkenylthio group, arylthio group and acyl group.

When R ¹ , R ² and R ³ represent a heterocyclic group, the heterocyclic ring preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent described above. These substituents may be further substituted with the above substituents.

  Preferred examples of the compound represented by the general formula (I) of the present invention are shown below, but the present invention is not limited to these specific examples.

Next, the compound of the general formula (II) will be described in detail.
X is a substituted or unsubstituted amino group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto group, carboxyl group, more preferably an amino group or a hydroxy group. Particularly preferred is a hydroxy group.

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 As the substituent, the following substituent T can be applied.

  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, and 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, and 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 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, and particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino).

An aryloxycarbonylamino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino), a sulfonylamino group ( Preferably it is C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, for example, methanesulfonylamino, benzenesulfonylamino, etc.), a sulfamoyl group (preferably carbon number). 0-20, more preferably 0-16 carbon atoms, particularly preferably 0-12 carbon atoms, such as sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc.), carbamoyl groups (Preferably 1-20 carbon atoms, more preferably 1-16 carbon atoms, Preferably have 1 to 12 carbon atoms, such as carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc.), an alkylthio group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, especially Preferably it is C1-C12, for example, methylthio, ethylthio etc. are mentioned), an arylthio group (preferably C6-C20, more preferably C6-C16, especially preferably C6-C12. Yes, such as phenylthio, etc.), a sulfonyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl, tosyl, etc.). ), A sulfinyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, Preferably have 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.), ureido groups (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 carbon atom). For example, ureido, methylureido, phenylureido, etc.), phosphoric acid amide group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms). For example, diethyl phosphoric acid amide, phenyl phosphoric acid amide, etc.), hydroxy group, mercapto group, halogen atom (for example, 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 Or a hetero atom, for example, nitrogen atom, oxygen atom, sulfur atom, specifically imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzo Examples include oxazolyl, benzimidazolyl, benzthiazolyl, and the like. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, and particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyl and triphenylsilyl). It is done. Among these, an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, and an aryloxy group are more preferable, and an alkyl group, an aryl group, and an alkoxy group are more preferable.
These substituents may be further substituted with a substituent T. 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 (II) will be described in detail with specific examples, but the present invention is not limited to the following specific examples.

  The compounds represented by general formula (I) or (II) can be used alone or in admixture of two or more. In the present invention, the combined use of the compounds represented by formula (I) or (II) is also preferred. The hydrophobizing agent is used in an amount of 0.01 to 30 parts by mass, preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. By using the compound in this range, the moisture content can be reduced without substantially reducing the elastic modulus of the film.

  In the present invention, the method for adding the hydrophobizing agent may be added to the cellulose acylate solution (dope) after being dissolved in an organic solvent such as alcohol, methylene chloride or dioxolane, or may be added directly to the dope composition. .

[UV absorber]
The cellulose acylate film used for the functional film of the present invention preferably contains a UV absorber (ultraviolet absorber) in addition to the hydrophobizing agent.
Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with a low content is preferred. Further, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are preferably used. When the cellulose acylate film of the present invention is used as a protective film for a polarizing plate, the ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the liquid crystal, and the liquid crystal. From the viewpoint of display properties, those that absorb less visible light having a wavelength of 400 nm or more are preferred.

Specific examples of the benzotriazole ultraviolet absorber useful in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert). -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butyl Phenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2 -Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2 'Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate. As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

[Low molecular compounds]
In the present invention, the low molecular weight compound (hydrophobizing agent, ultraviolet absorber, etc.) used as a constituent of the cellulose acylate film has a molecular weight of lowering the water content without lowering the elastic modulus. It is preferable that it is 100 or more and 2000 or less. The molecular weight is preferably 100-1500. Moreover, the mass average value (logP) of the octanol-water partition coefficient of these low molecular weight compounds defined by the following formula (III) is 4 or more and 12 or less, more preferably 5 or more and 11 or less, Most preferably, it is 6 or more and 10 or less.
When the molecular weight is 100 or more, the low molecular weight compound is hardly volatilized when the cellulose acylate film is produced, and when it is 2000 or less, the problem of not dissolving during dope production does not occur. Further, when the log P is 4 or more, there is no problem that the moisture content of the cellulose acylate film is increased, and when it is 12 or less, there is no problem that it is difficult to be compatible with the cellulose acylate.

Formula (III)
Mass average log P = [Σ (Mi × Pi)] / ΣMi
In the formula, Mi is the mass of the i-th low molecular compound with respect to the total amount of low-molecular compounds added, and Pi is the logP value of the i-th low molecular compound.

The mass ratio of the whole low molecular compound to the cellulose acylate is 5% or more and 35% or less (5 to 35 parts by mass of the low molecular compound with respect to 100 parts by mass of the cellulose acylate), and 10% or more and 30%. The following is more preferable, and 15% to 25% is most preferable.
When the mass ratio is less than 5%, the hydrophobization becomes insufficient and the ultraviolet absorbing ability is insufficient, and when it exceeds 35%, volatility during film production tends to be a problem.

[Manufacture of cellulose acylate film]
The cellulose acylate film can be 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 types 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 halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. 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 by 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 as to be contained in the obtained solution in an amount of 10 to 40% by mass. 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, cellulose acylate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower 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., and more preferably 80 to 110 ° C.

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

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

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

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 a retardation increasing agent to the dope.
The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted 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 with high-temperature air whose temperature is successively changed from 100 ° C. 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.

  A film can also be formed by casting two or more layers using the adjusted cellulose acylate solution (dope). 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 with a low-viscosity cellulose acylate solution and the high-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. Further, the cellulose acylate solution may be cast simultaneously with other functional layers (for example, a low moisture permeability cured layer, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.). it can.

  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.

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 inhibitor is hardly recognized. If the addition amount is 1% by mass or less, no bleed-out (bleeding) of the deterioration preventing agent to the film surface is observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).
The cellulose acylate film is preferably added with fine particles as a matting agent.

  The kind of fine particles is preferably an inorganic compound, and examples of the inorganic compound include fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, and tin oxide. In this, it is preferable that it is a compound containing a silicon atom, and the silicon dioxide microparticles | fine-particles which can make the haze (haze) of a film small are especially preferable.

  Examples of the silicon dioxide fine particles include AEROSIL-200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  In the present invention, the average particle size of the fine particles in the dry film is preferably 100 nm to 500 nm, and more preferably 150 nm to 400 nm. The average particle size of the fine particles in the film can be confirmed by taking and observing a cross-sectional photograph. When the particle size is 500 nm or less, no haze deterioration or the like is observed, and no failure occurs in the wound state of the film as a foreign matter. Moreover, if it is 100 nm or more, sufficient winding-up improvement effect is seen.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size after being added to the film often change. It is to control the particle size formed by agglomeration and aggregation with acylate.

When the particle diameter immediately after being dispersed in the solvent is A and the average particle diameter in the film is B, it is preferable that A / B = 0.5 to 1.0. This change in particle size is caused by the fact that aggregation is easily promoted when fine particles are dispersed and then mixed with cellulose acylate or other low molecular weight compounds (hydrophobizing agents, etc.) in a solvent. If A / B is 0.5 or more, the transparency of the film will not deteriorate due to an increase in the average particle size in the film. On the other hand, if A / B is 1.0 or less, there will be no inconvenience that the average particle size in the film becomes small, and the films easily adhere to each other and the film surface is deformed.

  In order to adjust A / B to 0.5 to 1.0, the compatibility of the fine particle dispersion solvent and the compatibility between the functional groups on the surface of the fine particles and the dispersion solvent, cellulose acylate, and UV absorber, Alternatively, it can be achieved by adding fine particles to a dope in which cellulose acylate is dissolved or a dope in which an ultraviolet absorber is dissolved, and then dispersing by applying shear. As the disperser used here, an ultrasonic disperser, a line mill, a homomixer, or the like is preferably used.

  In the present invention, the amount of the fine particles to be added is preferably 0.15 to 0.5% by mass of fine particles having an average particle diameter of 100 to 500 nm, more preferably 0.20 to 0.0. It is 35 mass%, More preferably, it is 0.20-0.30 mass%.

For the dispersion of the fine particles, a composition in which the fine particles and the solvent are mixed is preferably treated with a high-pressure dispersion device. The high-pressure dispersion apparatus used for dispersion can be a high-pressure dispersion apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube. By treatment with a high-pressure dispersing apparatus, for example, in capillary tube diameter 1～2000Myuemu, it is preferred, more preferably 1960 N / cm ² or greater than the maximum pressure conditions inside the apparatus is 980 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 100 kcal / hour or more are preferable.

  Examples of such a high-pressure dispersing device include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidic Corporation or a nanomizer manufactured by Nanomizer. A homogenizer manufactured by the company can be used.

The fine particles are preferably dispersed in a solvent containing a water-soluble solvent, then diluted by adding a water-insoluble organic solvent to the water-soluble solvent, and mixed with a dope in which cellulose acylate is dissolved in the solvent.
Then, the mixed liquid is cast on a support, dried, and formed into a film to obtain a cellulose acylate film.

  Here, as the water-soluble solvent, lower alcohols are mainly used. Preferred examples of lower alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Further, the water-insoluble solvent is not particularly limited, but it is preferable to use a solvent used when forming a film of cellulose acylate, and a solvent having a solubility in water of 30% by mass or less is used, which includes methylene chloride, Examples include chloroform and methyl acetate.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by mass. Dispersing the fine particles at a concentration exceeding 30% by mass is not preferable because the viscosity rapidly increases. The concentration of the fine particles in the dispersion is preferably 5 to 25% by mass, more preferably 10 to 20% by mass.

  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.

The cellulose acylate film obtained as described above has the following characteristics.
[Thickness of cellulose acylate film]
The thickness of the cellulose acylate film is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and most preferably 30 μm to 100 μm. Usually, a thickness of 40 μm to 80 μm is common.
[Width of cellulose acylate film]
The width of the cellulose acylate film is arbitrary, and is determined in consideration of the convenience in polarizing plate processing. Usually 1000 mm to 2000 mm.

[Elastic modulus of cellulose acylate film]
The elastic modulus of the cellulose acylate film correlates with the degree of freedom of movement of the cellulose acylate molecular chain in the film. The higher the elastic modulus, the smaller the degree of freedom of movement of the cellulose acylate molecular chain. The diffusion rate of low molecular weight compounds such as water is also reduced. The elastic modulus of the cellulose acylate film can be increased by increasing the crystallinity. Conversely, the addition of a compound that is highly compatible with cellulose reduces the elastic modulus. The elastic modulus of the cellulose acylate film can be determined by a tensile test.
Specifically, the sample is conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the elastic modulus is measured according to the method described in JIS K7127. Tensilon manufactured by A & D Co., Ltd. can be used as the tensile tester.
The cellulose acylate film has an elastic modulus at 25 ° C. and 60% RH of 3800 N / mm ² or more in either the width direction or the longitudinal direction, more preferably 4410 N / mm ² or more and 5880 N / mm ² or less. It is. If it is less than 3800 N / mm ² , the moisture permeability tends to increase. Moreover, if it is 5880 N / mm < ² > or less, the problem that the processability of a film will be impaired does not arise and it is preferable.

[Crystallinity of cellulose acylate film]
The degree of crystallinity of the film can be increased by various methods, but the crystallization can be effectively promoted by processing at a high temperature with a high residual solvent amount. Therefore, in the production of a cellulose acylate film, it is preferable to dry the film at a high temperature immediately after the film is peeled off from the band or drum. The drying temperature is preferably 80 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 180 ° C. or lower, and most preferably 120 ° C. or higher and 160 ° C. or lower.
The amount of residual solvent effective for increasing crystallization varies depending on the combination of solvent types. For example, in the case of a methylene chloride / methanol mixed solvent system, the mass ratio of the mixed solvent to the cellulose acylate film is preferably 1% to 70%, more preferably 5% to 60%, and more preferably 10% to 50%. Most preferred. In the mixed solvent system of methylene chloride / methanol / n-butanol, it is preferably 20% or more and 90% or less, more preferably 30% or more and 80% or less, and most preferably 30% or more and 70% or less.
The crystallinity defined in the present invention is the sum of values obtained by subtracting the diffraction intensity at a Bragg angle 2θ = 14 ° from the diffraction peak intensity detected by X-ray diffraction measurement.
The crystallinity of the acylate film is preferably from 3000 to 15000, more preferably from 4000 to 12000, and most preferably from 5000 to 9000. If the crystallinity is too high, the film may become brittle or haze may increase, so it is preferable to be within the above range.

[Moisture content of cellulose acylate film]
The moisture content of the cellulose acylate film can be evaluated by measuring the equilibrium moisture content at a constant temperature and humidity. The equilibrium moisture content is calculated by measuring the moisture content of the sample that has reached equilibrium after being allowed to stand at the above temperature and humidity for 24 hours, and dividing the moisture content (g) by the sample mass (g). .
The water content of the cellulose acylate film at 25 ° C. and 80% RH is 2.9% by mass or less, more preferably 2.6% by mass or less, and most preferably 2.3% by mass or less.
When the moisture content exceeds 2.9% by mass, moisture permeability tends to increase.

[Water permeability]
Moisture permeability 60 ° C. according to JIS Z 0208, transmission at 95% RH in compliance with the moisture permeability measurement method was measured under an atmosphere of (relative humidity), the moisture permeability of each sample was measured, 24hrs per area 1 m ² (time) Calculated as the amount of water (g). Since the moisture permeability shows different values depending on the layer configuration and the number of layers, the moisture permeability of the functional film of the present invention is the functional film of the present invention (a cellulose acylate film is laminated with a low moisture permeability cured layer on one side) It is measured in the state.
The moisture permeability is a film property closely related to the durability of the polarizing plate, and the durability of the polarizing plate can be improved by reducing the moisture permeability. In the functional film of the present invention, the moisture permeability in an environment of 60 ° C. and 95% RH is preferably 100 g / m ² · 24 hrs or more and 600 g / m ² · 24 hrs or less. More preferably, it is 150 g / m ² · 24 hrs or more and 550 g / m ² · 24 hrs or less, and particularly preferably 200 g / m ² · 24 hrs or more and 500 g / m ² · 24 hrs or less. A moisture permeability of 100 g / m ² · 24 hrs or more is preferable because drying during the production of the polarizing plate is sufficiently performed and the durability of the polarizing plate is not impaired. On the other hand, if it is 600 g / m ² · 24 hrs or less, the penetration of water from the outside can be prevented, so that the durability of the polarizing plate is improved.

The moisture permeability can be lowered by reducing the amount of water adsorbed and the diffusion rate of water in the film. The hydrophobizing agent used in the present invention is particularly preferable because it can reduce the amount of water adsorbed without increasing the diffusion rate of water in the film. A method for increasing the crystallinity of the cellulose acylate film is also preferable because the amount of water adsorbed can be reduced without increasing the diffusion rate of water in the film.
Further, the moisture permeability can 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 stretching ratio of the film (the ratio of the increase due to stretching relative to the original length) is preferably in the range of 1 to 50%, more preferably in the range of 5 to 40%, and in the range of 10 to 35%. Most preferably.

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

In order to reduce the dimensional change due to moisture absorption, it is preferable to reduce the amount of residual solvent during film formation and to reduce the free volume in the polymer film.
A general method for reducing the residual solvent is to dry at a high temperature for a long time. However, if the time is too long, the productivity is naturally lowered. Therefore, the amount of the residual solvent with respect to the cellulose acylate film is preferably in the range of 0.01 to 1% by mass, more preferably in the range of 0.02 to 0.07% by mass, and 0.03 to 0%. The most preferable range is 0.05 mass%.
By controlling the amount of the residual solvent, the polarizing plate can be produced at low cost with high productivity.
The amount of residual solvent is measured using a gas chromatograph (GC18A, manufactured by Shimadzu Corporation) by dissolving a certain amount of sample in chloroform.

  In the solution casting method as described above, a film is produced using a solution (dope) obtained by dissolving a polymer material (cellulose acylate) in an organic solvent as described above. As described above, drying by the solution casting method is largely divided into drying on the drum (or band) surface and drying during film conveyance. When drying on the drum (or band) surface, it is preferable to dry slowly at a temperature that does not exceed the boiling point of the solvent being used (when the boiling point is exceeded, bubbles are formed). Moreover, it is preferable to dry at the time of film conveyance at the glass transition point of polymer material ± 30 ° C., more preferably ± 20 ° C.

As another method for reducing the dimensional change due to moisture absorption, it is preferable to add a compound having a hydrophobic group. The material having a hydrophobic group is not particularly limited as long as it is a material having a hydrophobic group such as an alkyl group or phenyl group in the molecule. By using the hydrophobizing agent, the dimensional change due to moisture absorption can be reduced due to its high hydrophobizing effect.
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. Moreover, when using the above-mentioned hydrophobizing agent as a compound which has this hydrophobic group, the mixture ratio can be made into the range of the addition amount mentioned above.

[Film retardation]
In this specification, Re (λ) and Rth (λ) respectively represent front retardation and retardation in the thickness direction at wavelength λ. Re (λ) is measured in KOBRA 21ADH (manufactured by Oji Scientific Instruments) by making light having a wavelength of λ nm incident in the normal direction of the film. Rth (λ) is the light of wavelength λnm from the direction inclined by + 40 ° with respect to the normal direction of the film, with Re (λ) and the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis) And a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH calculates based on the retardation value measured in three directions, the assumed value of the average refractive index, and the input film thickness value. Here, as the assumed value of the average refractive index, the values in the polymer handbook (JOHN WILEY & SONS, INC) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting these assumed values of average refractive index and film thickness.

<Low moisture permeability cured layer>
Next, the low moisture-permeable cured layer provided on at least one surface of the cellulose acylate film in the functional film of the present invention will be described.

The low moisture-permeable cured layer is a layer formed by applying a curable composition to the cellulose acylate film, drying and then curing, and the polymer forming the low moisture-permeable cured layer is I It is preferable that it contains a polymer unit derived from at least one compound selected from the group of compounds having a / O value of 0.8 or less. It preferably contains a polymer unit derived from at least one compound selected from the group of compounds having an I / O value of 0.7 or less, more preferably an I / O value of 0.6 or less. Particularly preferred is the inclusion of a polymer unit derived from at least one compound selected from the group of compounds represented by formula (A) and formula (B). It is presumed that the alicyclic structure contained in the structure of the polymerized unit has the effect of reducing the moisture permeability.
I / O values are described in “Organic Conceptual Diagram-Basics and Applications-” by Yoshio Koda, Sankyo Publishing.

The said curable composition which forms the said low moisture-permeable cured layer comprises a polymeric compound, a polymerization initiator, and another additive.
Examples of the polymerizable compound include compounds represented by general formula (A) and general formula (B).
Formula (A)

General formula (B)

  In general formula (A) and general formula (B), R1 represents a hydrogen atom or a C1-C3 alkyl group, Preferably, a hydrogen atom, a methyl group, and an ethyl group are represented. R2 represents an alkylene group having 1 to 5 carbon atoms or an alkylene oxide group, preferably a methylene group, an ethylene group, a methylene oxide group, or an ethylene oxide group. R3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and preferably represents a hydrogen atom, a methyl group, or an ethyl group.

  Although the preferable specific example of a compound represented by general formula (A) is shown, this invention is not limited to these.

  Preferable specific examples of the compound represented by formula (B) are shown below, but the present invention is not limited thereto.

  The compounds represented by the general formulas (A) and (B) are described in JP-A-60-152515.

As the polymerizable compound, in addition to the compounds represented by the general formulas (A) and (B), the following polymerizable compounds can be used.
For example, as a compound having two or more ethylenically unsaturated groups, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane polyethoxytri (meta) ) Acrylate, ditrimethylolpropane tetra (meth) acrylate, glycene polypropoxytri (meth) acrylate, di (meth) acrylate of ε-caprolactone adduct of hydroxypenic acid neopenglycol (eg Nippon Kayaku Co., Ltd.) KAYARAD HX-220, HX-620, etc.), pentaerythritol tetra (meth) acrylate, poly (meth) acrylate of dipentaerythritol and ε-caprolactone reaction product, dipentaerythritol Hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, polyglycidyl compounds (polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1 , 6-hexanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, glycerin polyglycidyl ether, glycerin polyethoxyglycidyl ether, trimethylolpropane polyglycidyl ether, trimethylolpropane polyethoxypolyglycidyl ether, etc.) and (meth) Epoxy (meth) acrylate, which is a reaction product of acrylic acid, and polyfunctional (meth) acrylate containing hydroxyl group And polyisocyanate compounds (tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate) , P-phenylene diisocyanate, etc.) and a polyfunctional urethane acrylate. You may use these individually or in mixture of 2 or more types.

Furthermore, as vinyl monomers, esters derived from acrylic acid or α-alkylacrylic acid (for example, methacrylic acid), or amides (for example, Ni-propylacrylamide, Nn-butylacrylamide, N- t-butylacrylamide, N, N-dimethylacrylamide, N-methylmethacrylamide, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylamidopropyltrimethylammonium chloride, methacrylamide, diacetone acrylamide, acryloylmorpholine, N-methylol Acrylamide, N-methylol methacrylamide, methyl acrylate, ethyl acrylate, hydroxyethyl acrylate, n-propyl acrylate, i-propyl acrylate 2-hydroxypropyl acrylate, 2-methyl-2-nitropropyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, t-pentyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-methoxymethoxyethyl acrylate, 2,2,2-trifluoroethyl acrylate, 2,2-dimethylbutyl acrylate, 3-methoxybutyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, n-pentyl acrylate, 3-pentyl acrylate , Octafluoropentyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate, cetyl acrylate, benzyl acrylate Benzyl methacrylate, methoxypolyethylene glycol methacrylate, n-octyl acrylate, 2-ethylhexyl acrylate, 4-methyl-2-propylpentyl acrylate, heptadecafluorodecyl acrylate, n-octadecyl acrylate, methyl methacrylate, 2,2,2 -Trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, hexafluoropropyl methacrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate , 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate Benzyl methacrylate, heptadecafluorodecyl methacrylate, n-octadecyl methacrylate, 2-isobornyl methacrylate, 2-norbornylmethyl methacrylate, 5-norbornen-2-ylmethyl methacrylate, 3-methyl-2-norbol Nylmethyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate, pentamethylpiperidyl methacrylate, tetramethylpiperidyl methacrylate, dimethylaminoethyl methacrylate, etc. ), Acrylic acid or α-alkyl acrylic acid (acrylic acid, methacrylic acid, itaconic acid, etc.),

  Vinyl esters (eg, vinyl acetate), esters derived from maleic acid or fumaric acid (dimethyl maleate, dibutyl maleate, diethyl fumarate, etc.), maleimides (N-phenylmaleimide, etc.), maleic acid, fumaric acid , Sodium salt of p-styrenesulfonic acid, acrylonitrile, methacrylonitrile, dienes (eg butadiene, cyclopentadiene, isoprene), aromatic vinyl compounds (eg styrene, p-chlorostyrene, t-butylstyrene, α-methyl) Styrene, sodium styrenesulfonate), N-vinylpyrrolidone, N-vinyloxazolidone, N-vinylsuccinimide, N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methyl Cetamide, 1-vinylimidazole, 4-vinylpyridine, vinyl sulfonic acid, sodium vinyl sulfonate, sodium allyl sulfonate, sodium methallyl sulfonate, vinylidene chloride, vinyl alkyl ethers (eg methyl vinyl ether), ethylene, propylene, 1 -Butene, isobutene, etc. are mentioned. Two or more of these vinyl monomers may be used in combination. Vinyl monomers other than these are listed in Research Disclosure No. 1955 (1980, July), JP-A-63-243108, high performance liquid polymer material (Maruzen Co., Ltd., issued on May 20, 1990) Chapter 14 may be used. it can. In the present invention, esters derived from acrylic acid or methacrylic acid, amides, and aromatic vinyl curable resins are particularly preferably used vinyl monomers.

  The compound having two or more ethylenically unsaturated groups and the vinyl monomer are from Nippon Kayaku Co., Ltd. under the trade name of KAYARAD, and from Daiichi Kogyo Seiyaku Co., Ltd. under the trade name of New Frontier. It can be obtained under the trade name of Aronix from Co., Ltd. and under the trade name of Funkrill from Hitachi Chemical Co., Ltd.

  The amount of the compound having two or more ethylenically unsaturated groups or the vinyl monomer added to the compound represented by the general formulas (A) and (B) is the required moisture permeability, pencil hardness, refractive index, and transparency. Can be arbitrarily selected depending on the properties, adhesion to the cellulose acylate film, etc., but the compound of the above general formulas (A) and (B), a compound having two or more ethylenically unsaturated groups, and a vinyl monomer The mass of the compound having two or more ethylenically unsaturated groups and / or the vinyl monomer (total mass of both) is preferably 70% by mass or less, and preferably 50% by mass or less, based on the total mass (total mass of the polymerizable compound). Is more preferable, and 30% by mass or less is most preferable.

<Initiator>
In order to obtain a low moisture-permeable cured layer, the curable composition contains a polymerization initiator.
(I) When performing heat curing, benzoyl peroxide, dicumyl peroxide, or the like is added.
(Ii) Add benzoyl peroxide / dimethylaniline, cumene hydroperoxide / vanadium accelerator, etc. when performing redox system room temperature curing.
(Iii) In the case of anaerobic curing, hydroperoxide / tertiary amine / sulfimide is added.
(Iv) In the present invention, ultraviolet curing is most preferred and will be described in detail.

  Examples of polymerization initiators that generate radicals by ultraviolet rays include known radical generators such as acetophenones, benzophenones, Michler's ketone, benzoylbenzoate, benzoins, α-acyloxime esters, tetramethylthiuram monosulfide, and thioxanthone. Can be used. In general, sulfonium salts and iodonium salts used as photoacid generators also act as radical generators upon irradiation with ultraviolet rays, and these may be used alone in the present invention. In addition to a polymerization initiator, a sensitizer may be used for the purpose of increasing sensitivity. Examples of the sensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, and thioxanthone derivatives.

  The addition amount of the polymerization initiator is preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the total mass of the polymerizable compound contained in the curable composition, and preferably 1 to 10 parts by mass. More preferably, it is used within the range of parts.

  For ultraviolet curing, various methods described in “Latest UV Curing Technology” (Information Technology Association, Inc., issued on September 29, 1991) can be preferably used.

  The low moisture-permeable cured layer is obtained by applying and drying a curable composition containing at least one compound selected from the compounds represented by formula (A) or (B) and an initiator on the cellulose acylate film. It can be formed by curing by a method such as heat curing, redox system room temperature curing, anaerobic curing, preferably ultraviolet curing.

  The preferable film thickness of the low moisture-permeable cured layer is 0.5 to 20.0 μm, preferably 1.0 to 15.0 μm, and more preferably 2.0 to 10.0 μm. If it is thinner than 0.5 μm, moisture-proof curing is insufficient, and if it exceeds 20.0 μm, curling becomes large, which may hinder handling.

[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 the functional film of the present invention is used as a protective film for a polarizing plate, the cellulose acylate surface is acid-treated or alkali-treated, that is, cellulose acylate, from the viewpoint of adhesiveness between the cellulose acylate surface adjacent to the polarizer. It is particularly preferable to carry out a saponification treatment.

The surface energy of the cellulose acylate surface of the functional film is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less. 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 functional film of the present invention, the contact angle method is preferably used.
Specifically, two types of solutions having known surface energies are dropped on the cellulose acylate film surface, and at the intersection between the surface of the droplet and the film surface, 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.

Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment of the cellulose acylate surface of the silk 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 concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 mol / L, and 0.5 to 2.0 mol / L. More preferably, it is in the range. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

As mentioned above, although the functional film of this invention was demonstrated, the functional film of this invention is applicable to various uses. Among these, polarizing plates and liquid crystal display devices are important applications.
Next, the polarizing plate of the present invention will be described.
The polarizing plate of the present invention is a polarizing plate in which a protective film is bonded to both sides of a polarizer, and at least one side of the protective film is the functional film of the present invention described above.
(Configuration of polarizing plate)
First, a protective film and a polarizer constituting the polarizing plate of the present invention will be described.
The polarizing plate of this invention may have an adhesive layer, a separate film, etc. as a component other than a polarizer and a protective film.

(1) Protective film The polarizing plate of the present invention has a total of two protective films, one on each side of the polarizer, and at least one sheet on one side is the functional film of the present invention. Further, at least one of the two protective films may have a function as a retardation film. When using the polarizing plate of this invention for a liquid crystal display device, it is preferable that at least one of the two polarizing plates arrange | positioned at the both sides of a liquid crystal cell is a polarizing plate of this invention.
The protective film used in the present invention is preferably a polymer film produced from norbornene resin, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyarylate, polysulfone, cellulose acylate, etc., and is a cellulose acylate film. Most preferred.

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

PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.
The saponification degree of PVA is not particularly limited, but is preferably 80 to 100 mol%, particularly preferably 90 to 100 mol% from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494 is also preferably used. it can.

After PVA is formed into a film, it is preferable to introduce a dichroic molecule to constitute a polarizer. As a method for producing a PVA film, a method of forming a film by casting a stock solution in which a PVA resin is dissolved in water or an organic solvent is generally preferably used. The concentration of the polyvinyl alcohol-based resin in the stock solution is usually 5 to 20% by mass, and a PVA film having a thickness of 10 to 200 μm can be produced by forming this stock solution by casting. 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 mass described in Japanese Patent No. 3251073 and the in-plane hue variation, Japanese Patent Application Laid-Open No. 2002-2005 A PVA film having a crystallinity of 38% or less described in No. 236214 can be used.

The birefringence (Δn) of the PVA film is preferably small, and a PVA film having a birefringence of 1.0 × 10 ⁻³ or less described in Japanese Patent No. 3342516 can be preferably used. However, as described in JP-A-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 may be set to 0.02 or more and 0.01 or less. Alternatively, as described in JP-A-2002-060505, the value of (nx + ny) / 2-nz may be 0.0003 or more and 0.01 or less. The retardation (front) 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 or more described in JP-A No. 2001-316492. PVA film having 500 or less optical foreign matter per 100 cm ² , PVA film having a hot water cutting temperature spot of 1.5 ° C. or less in the TD direction of the film described in JP-A-2002-030163, and glycerin Preferred is a PVA film formed from a solution in which 1 to 100 parts by mass of a trivalent to hexavalent polyhydric alcohol such as 1 to 100 parts by mass or a plasticizer described in JP-A 06-289225 is mixed in an amount of 15% by mass or more. Can be 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 in which the stress generated when stretching 4 to 6 times in water is 10 N or less may be used.

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 are described in “Applications of Polarizing Plates” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p. 39-p. As described in 45, PVA can be produced by immersing PVA in a solution obtained by dissolving iodine in an aqueous potassium iodide solution and / or an aqueous boric acid solution and adsorbing and orienting the PVA.

  When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and a bisazo dye and a trisazo dye are particularly preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt.

Specific examples of such dichroic dyes include, for example, CIDirect Red 37, Congo Red (CI Direct Red 28), CIDirect Violet 12, CIDirect Blue 90, CIDirect Blue 22, CIDirect Blue 1, CIDirect Blue 151, CIDirect Green 1st benzidine series, CIDirect Yellow 44, CIDirect Red 23, CIDirect Red 79 etc. diphenylurea series, CIDirect Yellow 12 etc. stilbene series, CIDirect Red
Examples thereof include dinaphthylamine series such as 31 and J acid series such as CIDirect Red 81, CIDirect Violet 9 and CIDirect Blue 78.
In addition, CIDirect Yellow 8, CIDirect Yellow 28, CIDirect Yellow 86, CIDirect Yellow 87, CIDirect Yellow 142, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 72, CIDirect Orange 106, CIDirect Orange 107, CIDirect Red 2, CIDirect Red 39, CIDirect Red 83, CIDirect Red 89, CIDirect Red 240, CIDirect Red 242, CIDirect Red 247, CIDirect Violet 48, CIDirect Violet 51, CIDirect Violet 98, CIDirect Blue 15, CIDirect Blue 67, CIDirect Blue 71, CIDirect
Blue 98, CIDirect Blue 168, CIDirect Blue 202, CIDirect Blue 236, CIDirect Blue 249, CIDirect Blue 270, CIDirect Green 59, CIDirect Green 85, CIDirect Brown 44, CIDirect Brown 106, CIDirect Brown 195, CIDirect Brown 210, CIDirect Brown 223 CIDirect Brown 224, CIDirect Black 1, CIDirect Black 17, CIDirect Black 19, CIDirect Black 54, and the like are further disclosed in Japanese Patent Laid-Open Nos. 62-70802, 1-161202, 1-172906, and 1-. The dichroic dyes described in JP-A Nos. 172907, 1-183602, 1-248105, 1-265205, and 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, more preferably 10 μm to 30 μm. Further, the ratio of the thickness of the polarizer to the thickness of the protective film described later is 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0 described in JP-A No. 2002-174727. .16 range is also preferable.
The crossing angle between the slow axis of the protective film and the absorption axis of the polarizer may be any value, but is preferably parallel or an azimuth angle of 45 ± 20 °.

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

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

The swelling step is preferably carried out only with water, but as described in JP-A-10-153709, in order to stabilize optical performance and avoid wrinkling of the polarizing plate substrate in the production line, polarized light is used. It is also possible to manage the degree of swelling of the polarizing plate substrate by swelling the 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 No. 2002-290025, iodine concentration, dye bath temperature, draw ratio in the bath, and a method of dyeing while stirring the bath liquid in the bath may be used.

When higher-order iodine ions are used as the dichroic molecule, in order to obtain a high-contrast polarizing plate, it is preferable to use a solution obtained by dissolving iodine in an aqueous potassium iodide solution in the dyeing step. In this case, iodine in the iodine-potassium iodide aqueous solution is preferably 0.05 to 20 g / l, potassium iodide is 3 to 200 g / l, and the mass ratio of iodine and potassium iodide is preferably 1 to 2000. The dyeing time is preferably 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, iodine is 0.5 to 2 g / l, potassium iodide is 30 to 120 g / l, the mass 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 cross-linking agent, those described in US Reissue Patent No. 232897 can be used, and as described in Japanese Patent No. 3357109, a polyhydric aldehyde may be used as a cross-linking agent in order to improve dimensional stability. However, boric acids are most preferably used. When boric acid is used as a crosslinking agent used in the hardening step, metal ions may be added to the boric acid-potassium iodide aqueous solution. Zinc chloride is preferred as the metal ion, but as described in JP 2000-35512 A, zinc halides such as zinc iodide, zinc sulfates, zinc acetates and the like are used instead of zinc chloride. You can also.

  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 / raw film thickness after bonding of the protective film) × (total draw ratio) > 0.17 or the relationship between the width of the polarizer when leaving the final bath and the width of the polarizer when bonding the protective film is 0.80 ≦ (protective film pasting) described in JP-A-2002-040247 It is also preferable to satisfy the following condition: polarizer width at time / width of 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, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or as described in Japanese Patent Laid-Open Nos. 07-325215 and 07-325218. Aging in a temperature and humidity controlled atmosphere can also be preferably performed.

  A protective film bonding process is a process of bonding the both surfaces of the above-mentioned polarizer which went out of the drying process 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. In addition, as described in JP-A-2001-296426 and JP-A-2002-86554, the moisture content of the polarizer at the time of bonding is adjusted in order to suppress the groove-like unevenness of the record due to the stretching of the polarizer. It is preferable to do. 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 resin (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, and particularly preferably 0.05 to 3 μm after drying.

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. When a functional film is used as the protective film, it is as described in [Surface Treatment of Cellulose Acylate Film]. 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 the preferred temperature range is 30 ° C. to 100 ° C., and the preferred 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 0.1~2.00g / m ^2, zinc 0-2. It is preferably 00 g / m ² . Further, the potassium content may be 0.2% by mass or less as described in JP-A No. 2001-166143, and the zinc content in the polarizer is described in JP-A No. 2000-035512. It is good also as 0.04 mass%-0.5 mass%.

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

(Characteristics of polarizing plate)
(1) Transmittance and degree of polarization The preferred single plate transmittance of the polarizing plate of the present invention is 40.0 to 49.5%, more preferably 41.0 to 49.5%. Further, the iodine concentration and the single plate transmittance may be in the ranges described in JP-A No. 14-258051. Furthermore, the preferable range of the transmittance (parallel transmittance) when two polarizing plates of the same type are overlapped with the absorption axes being coincident is 36 to 42%, and the transmission when the absorption axes are overlapped is orthogonal. A preferable range of the rate (orthogonal transmittance) is 0.001 to 0.05%. These transmittances are defined by the following mathematical formula (1) based on JIS Z-8701.
Formula (1)

Here, K, S (λ), y (λ), and τ (λ) are as shown in the following formula (2).
Formula (2)

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

Moreover, the preferable range of the polarization degree in the polarizing plate of this invention is 99.900% or more and 99.999% or less based on the definition by following Numerical formula (3), More preferably, it is 99.940% or more and 99.99. 995% or less.
Formula (3)

Furthermore, the preferable range of the dichroic ratio defined by the following mathematical formula (4) is 48 or more and 1215 or less, and more preferably 53 or more and 525 or less.
Formula (4)

The iodine concentration and the single plate transmittance may be within the ranges described in JP-A No. 2002-258051.
The parallel transmittance may be small in wavelength dependency as described in Japanese Patent Application Laid-Open Nos. 2001-083328 and 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.

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

Parallel transmittance and orthogonal transmittance at a wavelength of 440 nm of the polarizing plate, parallel transmittance, wavelength 550 n
The parallel transmittance and the orthogonal transmittance at m, and the parallel transmittance and the orthogonal transmittance at a wavelength of 610 nm can preferably be set within the ranges described in JP-A Nos. 2002-258042 and 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 (5) using X, Y, and Z described above.
Formula (5)

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

A preferable range of a ^* of the single polarizing plate is −2.5 or more and 0.2 or less, and more preferably −2.0 or more and 0 or less. A preferable range of b ^* of the single polarizing plate is 1.5 or more and 5 or less, and more preferably 2 or more and 4.5 or less. The preferable range of a ^* of the parallel transmitted light of the two polarizing plates is −4.0 to 0, and more preferably −3.5 to −0.5. The preferable range of b ^* of the 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 preferred range of a ^* of the orthogonally transmitted light of the two polarizing plates is from −0.5 to 1.0, and more preferably from 0 to 2. 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-A Nos. 2002-214436, 2001-166136 and 2002-169024, and the relationship between hue and absorbance is It can also be preferably performed within the range described in JP-A-2001-311827.

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

(4) Durability (4-1) Wet heat durability As described in JP-A-2001-116922, light transmittance and polarization degree before and after standing in an atmosphere of 60 ° C. and 90% RH for 500 hours. It is preferable that the change rate of is 3% or less based on the absolute value. In particular, the change rate of the light transmittance is 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 preferred that the degree of polarization after standing at 80 ° C. and 90% RH for 500 hours is 95% or more and the single transmittance is 38% or more.

(4-2) Dry durability It is preferable that the light transmittance and the rate of change of the degree of polarization before and after standing in a dry atmosphere at 80 ° C. for 500 hours are also 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value.

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

(5) Orientation degree The higher the degree of orientation of PVA, the better the polarization performance, but the range of 0.2 to 1.0 is preferable as the order parameter value calculated by means such as polarization Raman scattering or polarization FT-IR. 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 0.5. 15, the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85, as described in JP-A No. 04-204907, or the higher order iodine ions of I ₃ ⁻ and I ₅ ⁻ It is also preferable to set the degree of orientation to 0.8 to 1.0 as an order parameter value.

(6) Other properties 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 2002-236213, when the polarizing plate was placed under heating conditions of 70 ° C. for 120 hours, both the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarization axis direction of the polarizing plate were It can be preferably carried out within ± 0.6%, or the moisture content of the polarizing plate can be 3% by mass or less as described in JP-A-2002-090546. Further, as described in JP-A No. 2000-249832, the surface roughness in the direction perpendicular to the stretching axis is set to 0.04 μm or less based on the center line average roughness, or described in JP-A No. 10-268294. The refractive index n ₀ in the transmission axis direction is preferably made larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film is preferably within the range described in JP-A-10-111411. be able to.

(Functionalization of polarizing plate)
The polarizing plate of the present invention includes an LCD viewing angle widening film, a retardation film such as a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, a brightness enhancement film, It is preferably used as a functionalized polarizing plate combined with an optical film having functional layers such as a coat layer, a forward scattering layer, and an antiglare (antiglare) layer.
The structural example of the polarizing plate which combined the functional film of this invention and the below-mentioned functional optical film was shown in FIG. The polarizing plate 5 may be bonded to the functional film 1 with an adhesive and the functional optical film 3 as a protective film on one side and the polarizer 2 (FIG. 1A). A functional film 1a is provided on one side of the polarizer 2, and a protective film 1b is provided on the other side.
The functional optical film 3 may be bonded to the polarizing plate 5 configured as described above through the adhesive layer 4 (FIG. 1B). The functional optical film is preferably arranged on the liquid crystal cell side according to the intended function, or on the side opposite to the liquid crystal cell, that is, on the display side or the backlight side.

The functional optical film used as a part of the polarizing plate of the present invention or in combination with the polarizing plate of the present invention will be described below. Examples of the functional optical film include the following (1) to (5).
(1) Viewing Angle Enlargement Film The polarizing plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory).
Bend), VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) can be used in combination with a viewing angle widening film proposed for display modes.

As a viewing angle widening film for the TN mode, the Japan Printing Society Vol. 36, No. 3 (1999) p. 40-44, monthly display August issue (2002) p. No. 20-24, JP-A-4-229828, JP-A-6-75115, JP-A-6-214116, JP-A-8-50206, etc. are preferably used in combination. The
The preferred structure of the viewing angle widening film for TN mode is the one having the polymer film used as the protective film as a base film and an orientation layer and an optically anisotropic layer (viewing angle compensation layer) in this order. It is. The viewing angle widening film may be used by being bonded to a polarizing plate through an adhesive, but SID'00 Dig., P. As described in 551 (2000), it is particularly preferable from the viewpoint of thinning that one of the protective films of the polarizer is also used.

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

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

  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. is 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, cellulose acetate, cellulose acetate Mention may be made of polymers such as pionate, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.
The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.

  A preferred embodiment of the viewing angle widening film is composed of a cellulose acylate film as a 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.

  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 a state where no electric field is applied. As 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, a film in which the films arranged in parallel with each other, a stretched film having the same front 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.
Moreover, what gave phase difference by extending | stretching norbornene-type resin film and polycarbonate resin can also be used preferably as a viewing angle expansion film or its part.

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

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

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

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

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

(3) Antireflection film The polarizing plate of the present invention can be used in combination with an antireflection film. Specifically, an antireflection film is provided on 1 and 1a in FIG. For the anti-reflection film, either a film having a reflectance 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 reflectance of 1% or less using multilayer interference of a thin film is used. it can. In the present invention, a low refractive index layer as an antireflection layer on a base film (support), 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 medium refractive index layer). A structure in which is laminated is preferably used. In addition, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28 and JP-A No. 2002-301783 can also be preferably used. It is preferable that the functional film of the present invention also serves as the base film of the antireflection film.
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 low moisture permeability cured layer of functional film> refractive index of low refractive index layer

  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 paragraphs [0018] to [0026] of JP-A-9-222503, paragraphs [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 (Japanese Patent Laid-Open No. 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-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 gas phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, atmospheric pressure CVD method, etc.), but it can be manufactured at low cost by a coating method. It is preferable to form. 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. 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, etc .: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds or (Organic metal coupling agent: JP-A-2001-310432, etc.), core-shell structure with high refractive index particles as a core (JP-A-2001-166104, etc.) No. 153703, Patent No. US62010858B1, Japanese Patent Laid-Open No. 2002-27776069, etc.).

As the matrix material, conventionally known thermoplastic resins, curable resin films, and the like can be used, but JP-A-2000-47004, 2001-315242, 2001-31871, and 2001-296401. It is also possible to use a curable film obtained from a polyfunctional material described in a gazette or the like or a metal alkoxide composition described in JP-A-2001-293818 or the like.
The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

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

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

  In the anisotropic reflection system, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers and increasing the refractive index difference in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal systems (European Patent No. 606940A2, Japanese Patent Laid-Open No. Hei 8- No. 271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. )) Is 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, positive numbers described in the specifications of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226 and JP-A-9-274108 and 11-174231 are described. It is also preferable to use in combination with an anisotropic scattering type brightness enhancement film obtained by uniaxially stretching by blending an intrinsic birefringent polymer and a negative intrinsic birefringent polymer. 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 may be used as an integrated type in which one of the polarizing film and the protective film of the polarizing plate (for example, 1b in FIG. 1) is used as a brightness enhancement film. preferable.

(5) Other Functional Optical Film The polarizing plate of the present invention is also preferably used in combination with a hard coat layer, a forward scattering layer, and an antiglare (antiglare) layer.

(5-1) Hard coat layer The polarizing plate of the present invention is preferably provided with a hard coat layer on the surface of the functional film of the present invention in order to impart mechanical strength such as scratch resistance. When the hard coat layer is used as a functional optical film applied to the above-described antireflection film, it is particularly preferable to provide it between the functional film of the present invention and the antireflection layer, particularly the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of the curable compound by light and / or heat. The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound. As specific constituent compositions of the hard coat layer, for example, those described in JP-A Nos. 2002-144913, 2000-9908 and WO00 / 46617 can be preferably used.
The film thickness of the hard coat layer is preferably 0.2 to 100 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

  As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group or a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferred examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol. Polyacrylates of polyols such as hexaacrylate; epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether; obtained by reaction of polyisocyanate and hydroxyl group-containing acrylate such as hydroxyethyl acrylate Examples of preferred compounds include urethane acrylates. Moreover, as a commercially available compound, EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (above, Daicel UCB Co., Ltd. product), UV -6300, UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.

  Preferred examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, glycerol triglycidyl ether as glycidyl ethers. Triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin, etc. Celoxide 2021P, Celoxide 2081 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.

For the hard coat layer, fine particles of oxide such as silicon, titanium, zirconium, and aluminum, and polyethylene are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and reduce curling of the polarizing plate of the present invention. It is also preferable to add crosslinked fine particles such as crosslinked fine particles such as polystyrene, poly (meth) acrylic acid esters and polydimethylsiloxane, and fine organic particles such as fine crosslinked rubber fine 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 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, and the 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 or the like which 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). No. 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.

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

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

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

(Liquid crystal display device using polarizing plate)
Next, the liquid crystal display device of the present invention in which the polarizing plate of the present invention is used will be described.
The liquid crystal display device of the present invention has a liquid crystal cell and two polarizing plates disposed on both sides thereof, and at least one polarizing plate is the polarizing plate according to the present invention described above.
FIG. 2 is an example of the liquid crystal display device of the present invention 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 cell upper electrode substrate 15 and a liquid crystal cell lower electrode substrate 18 and a liquid crystal layer 17 formed of liquid crystal molecules sandwiched between them. 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 layer 17 (hereinafter, also referred to as “inner surface”), and by a rubbing process or the like applied on the alignment film, The orientation of the liquid crystal layer 17 is controlled in a state where no electric field is applied or a state where a low voltage is applied. Further, transparent electrodes (not shown) capable of applying an electric field to the liquid crystal layer 17 made of liquid crystal molecules are formed on the inner surfaces of the substrates 15 and 18.

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 is added so that the twist angle becomes 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 electrode substrate 18 of the liquid crystal cell, and an electric field parallel to the substrate surface is applied. In the OCB mode, there is no twist angle, and in the VA mode, the liquid crystal layer 17 is aligned perpendicularly to the upper and lower substrates 15 and 18.

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 between 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 each other, whereby high contrast is obtained. 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 electrode substrate 15 of the liquid crystal cell depends 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, as shown in FIG. 2, the above-described upper and lower viewing angle widening films 13 and 20 can be separately disposed between the liquid crystal cell and the polarizing plate. The upper and lower polarizing plates 11 and 22 and the upper and lower viewing angle widening films 13 and 20 may be arranged in a laminated form bonded with an adhesive, or a so-called integrated type in which one of the liquid crystal cell side protective films is used for widening the viewing angle. It may be arranged as an elliptically polarizing plate.

  When the liquid crystal display device using the polarizing plate of the present invention is used as a transmission type, a backlight using a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, or an electroluminescent element as a light source. Can be placed on the back. 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.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited to these.

<Example of cellulose acylate film production>
(Preparation of cellulose acylate film 1a)
A composition having the following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution A.

<Composition of cellulose acetate solution A>
Cellulose acetate with 61.2% acetylation 50 parts by mass Cellulose acetate with 60.6% acetylation 50 parts by mass Triphenyl phosphate (hydrophobizing agent 1) 7.8 parts by mass Biphenyl diphenyl phosphate (hydrophobizing agent 2) 3 .9 parts by mass Methylene chloride (first solvent) 300 parts by mass Methanol (second solvent) 54 parts by mass 1-butanol 11 parts by mass

  A composition having the following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-1 was prepared.

<Additive solution B-1 composition>
Methylene chloride 80 parts by weight Methanol 20 parts by weight UV absorber (A) 2 parts by weight UV absorber (B) 4 parts by weight

  A dope was prepared by adding 474 parts by mass of cellulose acetate solution A and 40 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. Was kept at 115 ° C. until the solvent content became 5% by mass while maintaining an interval of 4% (drying step 1). Then, by conveying between the rolls of the heat treatment apparatus, the film was further dried at 140 ° C. to produce a cellulose acylate film 1a having a thickness of 80 μm (hereinafter also referred to as cellulose acetate film 1a).

(Production of cellulose acylate films 1b to 1f)
Cellulose acylate films 1b to 1f (hereinafter each referred to as cellulose acetate film 1b) except that the type and amount of hydrophobizing agent, the amount of residual solvent at the time of stripping, and the temperature of drying step 1 were changed to the contents shown in Table 1. To 1f)).
Comparative compound (A)

  The water content, elastic modulus, and crystallinity of the cellulose acylate film thus prepared were measured by the following methods. The results are shown in Table 2.

<Measurement of moisture content>
After adjusting the humidity for 24 hours in an environment of 25 ° C. and 80% RH, the equilibrium moisture content was measured with an AQ-2000 Karl Fischer moisture measuring device manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of elastic modulus>
The sample was conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the elastic modulus was measured according to the method described in JISK 7127. Tensilon manufactured by A & D Co., Ltd. was used as the tensile tester, the test piece was 50 mm × 10 mm, the distance between chucks was 30 mm, and the test speed was 30 mm / min.

<Crystallinity>
The diffraction pattern of the sample was measured using JDX-11RA manufactured by JEOL Ltd. The sum of values obtained by subtracting the diffraction intensity at the Bragg angle 2θ = 14 ° from the measured diffraction peak is defined as the crystallinity. The scanning range was measured at 2θ = 5 ° to 35 °.

[Example 1]
(Preparation of a coating solution comprising a curable composition for forming a low moisture-permeable cured layer)

<Coating solution composition comprising curable composition>
4.85 parts by mass of Compound K-5 (Nippon Kayaku Co., Ltd. KAYARAD R-684)
MEK (methyl ethyl ketone) 4.50 parts by mass Cyclohexanone 0.50 parts by mass Photoradical polymerization initiator 0.15 parts by mass (Irgacure 907, manufactured by Ciba Geigy Corporation)

  The composition having the above composition was mixed and stirred to obtain a coating solution for forming a low moisture permeability cured layer.

A cellulose acylate film 1c, 1d, 1e, 1f is coated with a coating solution for forming a low moisture permeability cured layer using a micro gravure roll having a diameter of 135 lines / inch and a depth of 60 μm and a diameter of 50 mm and a doctor blade. The coating layer was applied at a conveyance speed of 10 m / min, dried at 60 ° C. for 150 seconds, and further irradiated with ultraviolet rays having an irradiation amount of 300 mJ / cm ² under a nitrogen purge to cure the coating layer. The rotational speed of the gravure roll was adjusted so that the thickness of the low moisture permeability cured layer after curing was 5.0 μm.
Hereinafter, the functional film of the present invention in which a low moisture permeability cured layer is formed,
Cellulose acylate film 1c + low moisture permeability cured layer Cellulose acylate film 1d + low moisture permeability cured layer Cellulose acylate film 1e + low moisture permeability cured layer Cellulose acylate film 1f + low moisture permeability cured layer

<Measurement of moisture permeability>
Cellulose acylate films 1a and 1b, cellulose acylate film 1c + low moisture permeability cured layer, cellulose acylate film 1d + low moisture permeability cured layer according to the method described in JIS Z 0208 (temperature and humidity is 60 ° C. and 95% RH) The moisture permeability of the cellulose acylate film 1e + low moisture permeability cured layer and the cellulose acylate film 1f + low moisture permeability cured layer were measured. The results are shown in Table 2.

[Example 2]
(Saponification treatment)
Cellulose acylate film 1a, 1b, cellulose acylate film 1c + low moisture permeability cured layer, cellulose acylate film 1d + low moisture permeability cured layer, cellulose acylate film 1e + low moisture permeability cured layer, cellulose acylate film 1f + low moisture permeability cured The layer was immersed in a 1.5 mol / L aqueous sodium hydroxide solution at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing bath, and neutralized using 0.05 mol / L sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of the cellulose acylate film was saponified.
Furthermore, the Fuji Photo Film WV film was saponified under the same conditions and used for the following sample preparation.

(Preparation of polarizing plate (1a))
A polarizer was prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and a saponified cellulose acylate film 1a 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, the saponified WV film was attached to the opposite side of the polarizer using a polyvinyl alcohol-based adhesive. Thus, the polarizing plate (1a) was produced.

(Preparation of polarizing plates (1b) to (1f))
Polarizing plates (1b) to (1f) were produced in the same manner as the polarizing plate (1a) by the combination of cellulose acylate films shown in Table 2.

[Example 3]
The polarizing plate produced in this manner is attached to a glass plate so that the WV film is on the glass side, the parallel transmittance and the orthogonal transmittance are measured with a Shimadzu UV2200 spectrophotometer, and the degree of polarization is calculated by the above (Equation 3). did. Further, after the polarizing plate was aged at 60 ° C. and 95% RH for 1000 hours, the parallel transmittance and the orthogonal transmittance were measured again, and the change in the polarization degree before and after the aging was calculated. The results are shown in Table 2.

  From the results in Table 2, it can be seen that the polarizing plate of the present invention has a small change in the degree of polarization with respect to heat and humidity and is excellent in durability.

[Example 4]
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 polarizing plate (1e) prepared in Example 2 is used instead. The WV film was attached to the observer side and the backlight side one by one through an adhesive so that the WV film was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be orthogonal. Under the environmental conditions of a temperature of 25 ° C. and a relative humidity of 65%, the backlight was continuously turned on for 300 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 5]
A cellulose acylate film 1e40 was produced in the same manner as the cellulose acylate film 1e. However, the cellulose acylate film 1e40 was prepared to have a thickness of 40 μm.
The water content, elastic modulus, and crystallinity of the cellulose acylate film 1e40 thus produced were measured by the above methods.
Thereafter, similarly to Example 1, a low moisture permeability cured layer was formed on the cellulose acylate film 1e40, and moisture permeability was measured.
A polarizing plate (2e) was produced according to Examples 2 to 3, and the degree of polarization was measured.
These measurement results are shown in Table 2.
From the results in Table 2, it can be seen that the polarizing plate of the present invention has a small change in the degree of polarization with respect to heat and humidity and is excellent in durability.
Further, the polarizing plate (2e) was evaluated in the same manner as in Example 4. 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.

It is explanatory drawing which shows the structural example which combined the polarizing plate and functional optical film of this invention, and the example (A) which adhere | attached the functional optical film and the polarizer through the adhesive agent as a protective film of the one side of a polarizing plate, Example (B) in which a functional optical film is bonded to a polarizing plate provided with a functional film of the present invention on one side of the polarizer and a protective film on the back side through an adhesive layer is shown. It is explanatory drawing which shows an example of the liquid crystal display device in which the polarizing plate of this invention is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Functional film 1a Functional film 1b Protective film 2 Polarizer 3 Functional optical film 4 Adhesive layer 5 Polarizing plate 11 Upper polarizing plate 12 Upper polarizing plate absorption axis 13 Upper viewing angle widening film 14 Upper viewing angle widening film 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 viewing angle widening film 21 Lower viewing angle widening film orientation control direction 22 Lower polarizing plate 23 Lower polarizing plate Absorption axis

Claims (10)

Cellulose reed having an elastic modulus at 25 ° C. and 60% RH of 3800 N / mm ² or more in at least one of the width direction and the longitudinal direction and a water content of 2.9 mass% or less at 25 ° C. and 80% RH A functional film comprising a rate film and a low moisture-permeable cured layer provided on at least one surface of the cellulose acylate film.   A cellulose acylate film formed by containing a low molecular compound having a molecular weight of 100 or more and 2000 or less and cellulose acylate, wherein one of the low molecular compounds has a hydrophobicity having at least one hydrogen-bonding hydrogen donating group And a mass average value of octanol-water partition coefficient (hereinafter referred to as logP) of the low molecular weight compound is at least one of the agent, the mass ratio of the low molecular weight compound to the cellulose acylate is 5% or more and 35% or less. A functional film comprising a cellulose acylate film of 4 or more and 12 or less and a low moisture-permeable cured layer provided on at least one surface of the cellulose acylate film. The elastic modulus at 25 ° C. and 60% RH in at least one of the width direction and the longitudinal direction is 3800 N / mm ² or more, and the moisture content at 25 ° C. and 80% RH is 2.9% by mass or less, and A cellulose acylate film formed by containing a low molecular compound having a molecular weight of 100 or more and 2000 or less and cellulose acylate, wherein one of the low molecular compounds has at least one hydrogen-bonding hydrogen donating group. It is at least one hydrophobizing agent, the mass ratio of the low molecular compound to cellulose acylate is 5% or more and 35% or less, and the mass average value of the octanol-water partition coefficient (hereinafter logP) of the low molecular compound is 4 or more and 12 or less, and the cellulose acylate film is provided on at least one surface of the cellulose acylate film. Functional film which comprises a low moisture permeability cured layer. The low moisture permeability cured layer is
A curable composition containing at least one compound selected from the compound represented by the following general formula (A) and the compound represented by the following general formula (B) is coated and dried on the cellulose acylate film. The functional film according to claim 1, wherein the functional film is obtained by curing.
Formula (A)

(Wherein R1 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 is an alkylene group or alkylene oxide group having 1 to 5 carbon atoms, R3 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is 1 or An integer of 2)
General formula (B)

(Wherein R1, R3 and n have the same meaning as in the above general formula (A))   The functional film according to claim 1, wherein a ratio of the phosphoric acid compound to cellulose acylate is 5% by mass or less.   The functional film according to any one of claims 1 to 5, wherein the cellulose acylate film has a crystallinity of 3000 to 15000. The moisture permeability measured in accordance with JIS Z 0208 in an environment of 60 ° C and 95% RH is 100 g / m ² · 24 hrs or more and 600 g / m ² · 24 hrs or less. The functional film as described.   A polarizing plate in which a protective film is bonded to both sides of a polarizer, wherein at least one of the protective films is the functional film according to claim 1.   In the polarizing plate in which a protective film is bonded to both sides of the polarizer, the protective film on one side is the functional film according to any one of claims 1 to 7, and the side opposite to the functional film across the polarizer is A polarizing plate, which is a retardation film. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to claim 8 or 9.

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