JP2002189127A - Film for liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a striped pattern hardly visible in a film for a liquid crystal display device used as a polarizing plate protective film or the like and manufactured in a solution film forming method even when the film thickness is <=60 μm. SOLUTION: Thickness data sampled at intervals of 1 mm extending over 500 mm continuously in a longitudinal direction are denoted as X(0)-X(500) (μm). Variance in thickness ΔD(n) (μm) per 1 mm is calculated based on the equation (1). ΔD(n)=X(n)-X(n-1)... (1) When the maximum term in ΔD(1)-ΔD(500) is expressed as ΔDmax, ΔDmax satisfies the inequality (2). ΔDmax<0.30... (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for a liquid crystal display device which has good flatness, and in particular, when used as a protective film for a polarizing plate, unevenness of a stripe pattern is hardly seen, and a method for producing the same.

[0002]

2. Description of the Related Art The demand for polarizing plates is rapidly increasing with the spread of liquid crystal displays (LCDs). This polarizing plate is generally formed by bonding a protective film to both sides or one side of a polarizing film having a polarizing ability via an adhesive layer. This polarizing film is made of polyvinyl alcohol (hereinafter referred to as “P
VA ") is mainly used, and a PVA film is uniaxially stretched and then dyed with iodine or a dichroic dye, or is reversely dyed and stretched, and then crosslinked with a boron compound. Have been made.

[0003] As a polarizing plate protective film to be bonded to a polarizing film, a cellulose acylate film is generally used. Particularly, due to its transparency, low birefringence, moderate moisture permeability and moderate rigidity, a cellulose acetate film is used. Is the most widely used. This cellulose acetate film is usually manufactured by a solution casting method, that is, a concentrated solution obtained by dissolving cellulose acetate in a solvent is cast on an endless support such as a drum or a band to have self-supporting properties. It is manufactured by peeling and drying the solvent.

[0004] By the way, when a film is produced by a solution casting method, mechanical vibration around the casting die, pneumatic vibration,
Various other disturbances cause uneven thickness in the longitudinal direction, and there is a phenomenon that a striped pattern (or a stepped pattern, the same applies hereinafter) is observed when the completed film is observed, which is a problem in appearance. In particular, in recent years, the demand for thinning has been remarkable, and a stripe pattern has become more visible when the thickness is reduced, so that a measure has been required.

Conventionally, as a method for improving the surface condition of a film produced by a solution casting method, a polymer concentrated solution (hereinafter, referred to as a polymer concentrated solution) is used.
There are known methods for reducing the viscosity of the "dope" to a certain level or less, casting the solution on a smoother endless support, and suppressing drying speed to prevent uneven drying. Also, Japanese Patent Application Laid-Open
JP-A-212298, a film wound on a take-up roll by suppressing thickness unevenness in the longitudinal direction to a constant level (with a film thickness of 20 to 60 μ and a film thickness variation within ± 3% of a reference thickness). A film that prevents wrinkles from being generated has been proposed.

[0006]

However, the method of improving the surface condition of a film proposed in the prior art is not enough to improve the stripe pattern in the width direction.
Some worked against the effect. Also, JP-A-2000-21
The film proposed in Japanese Patent No. 2298 has no recognition of the stripe pattern, and cannot prevent the occurrence of the stripe pattern.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a liquid crystal display device film in which a stripe pattern is hard to be visually recognized even in a thin film having a thickness of 60 μm or less, and a manufacturing method thereof. The aim is to provide a method.

[0008]

Means for Solving the Problems Conventionally, JP-A-2000-2
As proposed in Japanese Patent Publication No. 12298, there was a concept of suppressing the absolute value of the thickness variation, but it is intended to improve a planar failure such as wrinkles, and the technology relating to the variation of the thickness and the recognition of the striped pattern is not at all. Had not been proposed.

In order to solve the above-mentioned problems, the present inventors have intensively studied the relationship between the thickness variation and the visibility of the striped pattern. Found that it could not be recognized by human eyes. That is, the inventors have found that the absolute value of the thickness variation does not always correlate with the visual flatness.
Then, further diligent examination, found that the change in thickness per unit distance has a large effect on the flatness when viewed visually, and when the change in thickness per unit distance is less than a certain value, Finding that it is difficult to recognize the striped pattern,
The first film for a liquid crystal display device according to the present invention is completed.

When the change in thickness per unit distance changes from a region smaller than a certain value to a larger region and then to a smaller region, these regions are regarded as one thickness change region. If there is some space,
That is, it has been found that if the number of pieces in a certain length is small, it is difficult to recognize the striped pattern, and the second film for a liquid crystal display device according to the present invention has been completed.

Further, the present inventors have conducted intensive studies on a method for producing the above-mentioned film for a liquid crystal display device.
The present inventors have found that when the air pressure vibration having a frequency of about 100 Hz is reduced, the above-described film for a liquid crystal display device can be suitably manufactured, and the present invention has been completed.

Furthermore, it has been found that, when the moving speed of the endless support for casting the dope is made constant or more, the pitch of the deformation caused by the disturbance is widened, and the above-mentioned film can be suitably manufactured, and the present invention has been completed. That is,
It has been considered that when a thin film (60 μm or less) is formed, an increase in the moving speed of the endless support is greatly affected by disturbance such as vibration, so that the surface condition is deteriorated. However, according to the research of the present inventor, it was found that increasing the moving speed of the endless support greatly improved the waving of the film. In particular, it was found that it was extremely suitable to increase the speed to 30 m / min or more. It has been completed.

The first film for a liquid crystal display device according to the present invention is obtained by sampling the thickness data at intervals of 1 mm over a continuous length of 500 mm in X (0) to X (0).
(500) (μm), and 1 based on the following equation (1).
The thickness change per millimeter ΔD (n) (μm) is calculated, and ΔD (n) = X (n) −X (n−1)... ΔDm
When ax is set, ΔDmax has a relationship represented by the following equation (2). ΔDmax <0.30 Expression (2)

The second film for a liquid crystal display device according to the present invention is obtained by sampling thickness data at intervals of 1 mm over a continuous length of 500 mm in X (0) to X (0) to X (0) to X (X).
(500) (μm), and 1 based on the following equation (1).
The thickness change ΔD (n) (μm) per mm is calculated, and ΔD (n) = X (n) −X (n−1) (1) This thickness change ΔD (n) (μm) When a non-thickness increasing region that does not satisfy the following expression (3) becomes a satisfactory thickness increasing region and further becomes a non-thickening increasing region that does not satisfy the following expression (3),
The number N of the peak regions including the non-thickness increasing region, the thickness increasing region, and the non-thickness increasing region is characterized by a relationship represented by the following equation (4). ΔD> 0.10 Expression (3) N <25 Expression (4)

A first liquid crystal display device according to the present invention.
The method of manufacturing the system is to dissolve cellulose acylate in a solvent.
To prepare a dope and support the dope endlessly from a casting die.
It is cast on the body, peeled off continuously, dried and filled
A dope from a casting die.
Of the frequency-resolved component of the air pressure vibration in the discharge atmosphere
Among them, the air pressure vibration in the range of 5 to 100 Hz is 19.6.
0 Pa (2.0 mmAq) or less
It is configured.

In the second method for producing a film for a liquid crystal display device according to the present invention, a dope is prepared by dissolving cellulose acylate in a solvent, and the dope is cast from a casting die onto an endless support. A method of producing a film having a dry thickness of 20 to 60 μm by performing peeling and drying.
The moving speed of the endless support is set to 30 m / min or more.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A first film for a liquid crystal display device according to the present invention is obtained by sampling thickness data at intervals of 1 mm over a continuous length of 500 mm in the X direction.
(0) to X (500) (μm), a thickness change ΔD (n) (μm) per mm is calculated based on the following equation (1), and ΔD (n) = X (n) −X ( n-1) Expression (1) The largest one among ΔD (1) to ΔD (500) is ΔDm
When ax is set, ΔDmax needs to have a relationship of the following equation (2), and ΔDmax <0.30 ... Equation (2) Preferably, it has to have a relationship of the following equation (5). ΔDmax <0.15 Expression (5)

The maximum value ΔDmax of the thickness change is 0.30
When the thickness is not less than μm, the visibility of a planar failure such as a stripe pattern or waving becomes large, and when ΔDmax is less than 1.5, the stripe pattern and waving are hardly recognized, which is preferable.

The second film for a liquid crystal display device according to the present invention is obtained by sampling thickness data at intervals of 1 mm over a continuous length of 500 mm in X (0) to X (0) to X (X).
(500) (μm), and 1 based on the following equation (1).
The thickness change ΔD (n) (μm) per mm is calculated, and ΔD (n) = X (n) −X (n−1) (1) This thickness change ΔD (n) (μm) When a non-thickness increasing region that does not satisfy the following expression (3) becomes a satisfactory thickness increasing region and further becomes a non-thickening increasing region that does not satisfy the following expression (3),
It is necessary that the number N of the peak regions including the non-thickness increasing region, the thickness increasing region, and the non-thickness increasing region has a relationship represented by the following formula (4): ΔD> 0.10 (3) <25 ... Equation (4) Preferably, the number N of peak areas needs to be in the relationship of Equation (6), and N <20 ... Equation (6) More preferably, the number N of peak areas is It is necessary to have the relationship of equation (7). N ≦ 1 Equation (7)

The non-thickness increasing region is a region where there is little change in thickness and is flat or a region where the thickness is small, and the thickness increasing region is a region where the thickness is large. The peak region is a non-thickness increasing region,
A region comprising a thickness increasing region and a non-thickness increasing region,
In other words, it indicates a region where the thickness of the film has rapidly increased in a short time due to some disturbance.

If the film for a liquid crystal display device of the present invention satisfies one of the first and second embodiments, failure of a stripe pattern or the like can be effectively prevented.
It is preferable to satisfy both of the first mode and the second mode, since failure of a striped pattern can be more effectively prevented.

According to the first method for producing a film for a liquid crystal display device of the present invention, the frequency resolution component of the air pressure vibration in the atmosphere where the dope is discharged from the casting die is 5 to 10%.
The air pressure vibration in the range of 0 Hz is 19.60 Pa (2.0
mmAq) or less, and 9.80 Pa (1.mmAq).
0 mmAq) or less.

That is, the inventor of the present invention has argued that the vibration of the frequency component exceeding 100 Hz does not affect the surface state of the film to be visually observed even if it is present to some extent, and the vibration of the frequency component of less than 5 Hz is temporarily It has been found that the deformation pitch is sufficiently long even if is deformed, so that the deformation is hard to be visually observed and does not pose a problem. Therefore, the frequency component affecting the surface state of the film is 5 to 100 Hz.
When the air pressure vibration at a frequency in this range exceeds 19.60 Pa (2.0 mmAq), the surface condition of the film deteriorates.

The second method for producing a film for a liquid crystal display device according to the present invention is a method for producing a film having a dry thickness of 20 to 60 μm, wherein the moving speed of the endless support is 30 m.
/ Min or more, and preferably 35 m / min or more.

That is, by setting the moving speed of the endless support for casting the dope to 30 m / min or more, even if the deformation occurs due to disturbance, the moving speed of the dope is high, so that the pitch of the deformation is widened. As a result, it is difficult to visually recognize the deformation.

To manufacture a film for a liquid crystal display device,
Any of the first and second manufacturing methods may be satisfied, but it is preferable that both are satisfied at the same time, and a more suitable film for a liquid crystal display device can be manufactured.

The distance between the dope discharge port of the casting die and the endless support is preferably 0.5 to 2.5 mm,
More preferably, it is 0.5 to 1.5 mm. If the distance between the discharge port and the endless support is less than 0.5 mm, the discharge port and the endless support may be in contact with and damaged,
If it exceeds 2.5 mm, it may be affected by disturbances such as entrained wind from the endless support, vibration of the device, and the like, which may adversely affect the surface condition of the film.

The film for a liquid crystal display device according to the present invention comprises:
It can be applied to films of any thickness. For example, when used as a protective film for a polarizing plate, a film thickness of 20 to 120 μm is generally used from the viewpoint of handleability as a polarizing plate. This is effective for a film having a thickness of 20 to 60 μm, which has not been used for a polarizing plate, and is particularly effective for a film having a thickness of 30 to 50 μm. 20-60 μm
By setting the film thickness to, the thickness of the polarizing plate can be reduced.

As a material polymer of the film for a liquid crystal display device of the present invention, cellulose acylate, polysulfone, polystyrene, norbornene-based polyolefin, or the like can be used. .

The details of cellulose acylate preferable as a film for a liquid crystal display device will be described below.
Preferred cellulose acylates are those in which the degree of substitution of cellulose with hydroxyl groups satisfies all of the following formulas. 2.6 ≦ A + B ≦ 3.0 2.0 ≦ A ≦ 3.0 0 ≦ B ≦ 0.8 1.9 <AB

In the formula, A and B each represent a substituent of an acyl group substituted by a hydroxyl group of cellulose, A represents a degree of substitution of an acetyl group, and B represents a substitution of an acyl group having 3 to 5 carbon atoms. Degrees. Cellulose contains 3 per glucose unit
And the above-mentioned number represents the degree of substitution for the hydroxyl group 3.0, with the maximum degree of substitution being 3.0. Cellulose triacetate generally has a degree of substitution of A of 2.6 or more and 3.0 or less (in this case, there are as many as 0.4 unsubstituted hydroxyl groups), and the case of B = 0 is cellulose triacetate. The cellulose acylate used in the film for a liquid crystal display device of the present invention is a cellulose triacetate in which all acyl groups are acetyl groups, and the acetyl group is 2.0 or more, and the acyl group having 3 to 5 carbon atoms is 0.8 or less. Preferably, the unsubstituted hydroxyl group is 0.4 or less, and cellulose triacetate having a degree of substitution of 2.6 to 3.0 is particularly preferable. Such a degree of substitution of 2.6 is preferred.
It is preferable that the above-mentioned cellulose acetate accounts for 80% or more of the film weight.

The degree of substitution can be obtained by measuring the degree of binding between acetic acid and a fatty acid having 3 to 5 carbon atoms which are substituted for the hydroxyl groups of cellulose, and calculating the degree of substitution. The measurement method is AS
It can be carried out according to TM D-817-91.

Other acyl groups having 3 to 5 carbon atoms of an acetyl group include a propionyl group (C ₂ H ₅ CO—), a butyryl group (C ₃ H ₇ CO—) (n-, iso-), and a valeryl group ( _{C 4 H 9 CO -) (} n-, iso-, sec-, te
In rt-), among these, n-substituted ones are preferred from the viewpoint of mechanical strength and easy dissolution when formed into a film, and particularly preferred is an n-propionyl group. When the degree of substitution of the acetyl group is low, the mechanical strength and the moist heat resistance are reduced. When the degree of substitution of the acyl group having 3 to 5 carbon atoms is high, the solubility in an organic solvent is improved. However, if the degree of substitution is within the above range, good physical properties are exhibited.

The polymerization degree (average viscosity) of the cellulose acylate is preferably from 200 to 700, more preferably from 250 to 550.
Are preferred. The viscosity average degree of polymerization (DP) can be obtained by an Ostwald viscometer, and is obtained from the measured intrinsic viscosity [η] of cellulose acylate by the following formula. DP = [η] / Km (where Km is a constant 6 × 10 ⁻⁴ )

As the cellulose as a raw material for cellulose acylate, there are cotton linter and wood pulp. Cellulose acylate obtained from any raw material cellulose can be used, or a mixture thereof may be used.

As described above, the film for a liquid crystal display device of the present invention is manufactured by a solution casting method. In the solution casting method, usually, a cellulose acylate and various additives are dissolved in a solvent. A dope is prepared, cast on an endless support such as a drum or band, and the solvent is evaporated to form a film. The concentration of the dope is preferably adjusted so that the solid content is 10 to 40% by weight. The surface of the drum or band is preferably smoothed. The casting and drying methods in the solution casting method are described in US Pat.
No. 369603, No. 2492078, No. 249297
No. 7, No. 2492978, No. 2607704, No. 2
Nos. 739069 and 2739070, British Patent 640
Nos. 731 and 736892, Japanese Patent Publication No. 45-
Nos. 4554 and 49-5614, and JP-A-60-176.
No. 834, No. 60-203430, No. 62-1150
There is a description in each gazette of No. 35.

A method of casting two or more dopes is also preferably used. When casting a plurality of dopes, a film may be produced while casting and laminating a solution containing a dope from a plurality of casting ports provided at intervals in the traveling direction of the endless support, and laminating, for example, JP-A-61-1584
No. 14, JP-A-1-122419, JP-A-1-122419
The method described in Japanese Patent Application Laid-Open No. 1-198285 can be applied. Alternatively, a film may be formed by casting a cellulose acylate solution from two casting ports, for example, as disclosed in JP-B-60-27562 and JP-A-61-61621.
JP-A-94724, JP-A-61-947245, JP-A-61-104814, JP-A-61-1
It can be carried out by the method described in JP-A-58413 and JP-A-6-134933. Also, Japanese Patent Application Laid-Open No. 56-16261
The casting method of wrapping the flow of the high-viscosity dope described in Japanese Patent Publication No. 7 with a low-viscosity dope and simultaneously extruding the high- and low-viscosity dope is also preferably used.

Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg, benzene, toluene), halogenated hydrocarbons (eg, methylene chloride, chlorobenzene), alcohols (eg, methanol, ethanol, diethylene glycol), Examples include ketones (eg, acetone), esters (eg, ethyl acetate, propyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve).

Halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peeling property from endless support, mechanical strength of film, and optical properties, one or more kinds of alcohol having 1 to 5 carbon atoms in addition to methylene chloride are mixed. Is preferred. The content of the alcohol is preferably from 2 to 25% by weight, more preferably from 5 to 20% by weight, based on the whole solvent. Specific examples of alcohol include methanol, ethanol, n-propanol, isopropanol, n-
Examples thereof include butanol, and methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

Recently, a solvent composition not using methylene chloride has been proposed in order to minimize the influence on the environment. For this purpose, the number of carbon atoms is between 3 and 12
Ether, ketone having 3 to 12 carbon atoms, and ester having 3 to 12 carbon atoms are preferable, and these are appropriately mixed and used. These ethers, ketones and esters 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 may be within the specified range of the compound having any one of the functional groups. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane,
Examples include dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate,
Examples include methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

In addition to cellulose acylate, the components that become solids after drying include plasticizers, ultraviolet absorbers, inorganic fine particles, heat stabilizers such as salts of alkaline earth metals such as calcium and magnesium, and charging agents. It may optionally contain an inhibitor, a flame retardant, a lubricant, an oil agent, a release accelerator from the endless support, a hydrolysis inhibitor for cellulose acylate, and the like.

Phosphoric acid esters or carboxylic acid esters are preferably used as a plasticizer. Examples of phosphate esters include triphenyl phosphate (T
PP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. As the carboxylic acid ester,
Phthalates and citrates are typical. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and dioctyl phthalate (DO).
P), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (O
ACTE) and tributyl O-acetylcitrate (OA)
CTB), acetyltriethyl citrate, and acetyltributyl citrate.

Examples of other carboxylic esters include trimellitic esters such as butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate and the like.

Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, It is preferable to use diethylhexyl phthalate, triacetin, ethyl phthalyl ethyl glycolate, trimethyl trimellitate and the like. Particularly, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, and trimethyl trimellitate are preferred. These plasticizers may be used alone or in combination of two or more. The amount of the plasticizer added is preferably 5 to 30% by weight, particularly preferably 8 to 16% by weight, based on the cellulose acylate. These compounds may be added together with the cellulose acylate or the solvent when preparing the cellulose acylate solution, or may be added during or after the solution is prepared.

Any type of ultraviolet absorber can be selected according to the purpose. Salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based and nickel complex-based absorbers are used. However, benzophenone-based, benzotriazole-based, and salicylic acid ester-based are preferred. Examples of benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2'-di-hydroxy-4,4'-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- (Methacryloxy) propoxybenzophenone and the like. As the benzotriazole-based ultraviolet absorber, 2 (2'-hydroxy-3'-ter
t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-tert
-Butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl)
Benzotriazole, 2 (2'-hydroxy-3 ', 5'-
Di-tert-butylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-octylphenyl) benzotriazole and the like. Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, pt
tert-butylphenyl salicylate and the like. Among these exemplified UV absorbers, particularly 2
-Hydroxy-4-methoxybenzophenone, 2,2'-
Di-hydroxy-4,4'-methoxybenzophenone, 2
(2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2
(2′-hydroxy-5′-tert-butylphenyl)
Benzotriazole, 2 (2'-hydroxy-3 ', 5'-
Di-tert-amylphenyl) benzotriazole,
2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole is particularly preferred.

It is particularly preferable to use a plurality of absorbers having different absorption wavelengths in combination since a high blocking effect can be obtained in a wide wavelength range. The amount of the ultraviolet absorber is preferably 0.01 to 5% by weight based on the cellulose acylate, and is preferably 0.1 to 5% by weight.
1-3% by weight is particularly preferred. The ultraviolet absorber may be added simultaneously with dissolution of the cellulose acylate, or may be added to the dope after dissolution. In particular, using a static mixer, etc., the form in which the ultraviolet absorber solution is added to the dope just before casting can easily adjust the spectral absorption characteristics,
preferable.

The inorganic fine particles to be added to the cellulose acylate include silica, kaolin, talc, diatomaceous earth,
Quartz, calcium carbonate, barium sulfate, titanium oxide, alumina and the like can be arbitrarily used according to the purpose.
Before adding these fine particles to the dope, a high-speed mixer,
It is preferable to perform dispersion in the binder solution by any means such as a ball mill, an attritor, and an ultrasonic disperser. Cellulose acylate is preferred as the binder. It is also preferable to carry out dispersion with other additives such as an ultraviolet absorber. The dispersion solvent is optional, but preferably has a composition close to that of the dope solvent. The number average particle size of the dispersed particles is 0.0
It is preferably from 1 to 100 μm, particularly preferably from 0.1 to 10 μm. The above dispersion may be added to the cellulose acylate dissolving step at the same time or may be added to the dope in any step. However, it is preferable to add the dispersion immediately before casting using a static mixer or the like as in the case of the ultraviolet absorbent.

As a release accelerator from the endless support, a surfactant is effective and is not particularly limited, such as a phosphoric acid type, a sulfonic acid type, a carboxylic acid type, a nonionic type and a cationic type. These are described, for example, in JP-A-61-243837.

The film for a liquid crystal display device of the present invention contains P
In order to increase the adhesion to the VA resin, it is preferable to impart hydrophilicity to the film surface by means of saponification, corona treatment, flame treatment, glow discharge treatment or the like. Further, a hydrophilic resin may be dispersed in a solvent having an affinity for cellulose acylate, and a thin layer may be applied. Among the above means, saponification treatment is particularly preferable because the flatness and physical properties of the film are not impaired. The saponification treatment is performed, for example, by immersing the film in an aqueous alkaline solution such as caustic soda. After the treatment, it is preferable to neutralize with a low-concentration acid and sufficiently wash with water in order to remove excess alkali.

FIGS. 1 and 2 show specific examples of a manufacturing apparatus for manufacturing the film for a liquid crystal display device according to the present invention by a solution casting method, but the present invention is not limited to these examples.

FIG. 1 is a schematic view showing an example of a drum casting method in an apparatus for producing a film for a liquid crystal display device. In this figure, 10 is a casting section for casting a dope on an endless support to form a film, 20 is a stretching and drying section for stretching and drying the film formed by the casting section 10, and 30 is a film for drying. A drying unit 40 for drying the product into a product is a winding core for winding up the completed film.

The casting unit 10 has a casting die 12 provided in a drying chamber 11, a casting drum 13 as an endless support, and a stripping roll 14 for stripping a film. Is provided. Stretch drying section 2
Reference numeral 0 denotes a holding unit 22 provided in the drying chamber 21 for holding both ends of the film and extending in the width direction.
In the drying chamber 31, a number of transport rolls 32 are arranged in a drying chamber 31.

In order to produce a film using the above-described apparatus for producing a drum by a casting method, first, a dope is extruded from a casting die 12 and cast on a casting drum 13. It is preferable that the casting drum 13 is cooled to 10 ° C. or less in order to perform stripping quickly. After drying in an appropriate atmosphere, when the dope has self-supporting properties,
Through the film as a film containing the residual solvent. The peeled film is introduced into a drying chamber 21, and both ends are held by holding means 22, and dried while being transported while applying tension in the width direction. As the holding means 22, any means such as a clip and a pin can be used. The drying means is generally sprayed with hot air, but any means such as infrared rays and microwaves can be used. Residual solvent is 20
% Is preferable. The film is further conveyed to a drying chamber 31, and is further circulated and conveyed around a conveying roll 32, and further dried to form a core 40.
Is wound up in a roll form. The amount of the residual solvent during winding is preferably 0.8% or less, more preferably 0.5% or less.

FIG. 2 is a schematic view showing an example of the band casting method. In this figure, 50 is a casting section for casting a dope on an endless support to form a film, 60 is a stretching drying section, 70 is a drying section, and 80 is a core.

The casting section 50 is provided with a casting die 52 in a drying chamber 51, a casting band 53 as an endless support, and a stripping roll 54 for stripping a film. Is provided. Stretch drying section 6
The drying unit 70 and the winding core 80 are substantially the same as those in the drum casting method shown in FIG.

In order to manufacture a film by the above-described band casting method, first, a dope is extruded from a casting die 52 and cast on a casting band 53. The film is dried on the belt 53 by means of hot air or the like. When the dope has a self-supporting property, the film is peeled off via a peeling roll 54 as a film containing the residual solvent. The peeled film is introduced into the drying chamber 61 and both ends are held by holding means 6.
2 and dried while conveying while applying tension in the width direction. This film is further transported to the drying chamber 71,
While being wound around and transported by the transport roll 72, it is further dried and wound up in a roll form by the core 40.

The drying chambers 11, 21, 31, 51, 6
1 and 71 do not need to be under a single drying condition, but may be divided into several sections and dried in different atmospheres. Further, it is preferable that the film heating for improving the heat shrinkage is performed in the latter half of the drying units 30 and 70.

In the method for producing a film for a liquid crystal display device according to the present invention, 5 to 100 of the frequency-resolved components of the air pressure vibration in the atmosphere in which the dope is discharged from the casting die.
The air pressure vibration in the range of Hz is 19.60 Pa (2.0 m
mAq). In order to achieve such a configuration, the air pressure vibration of the atmosphere around the casting dies 12, 52 is reduced, and the pressure of the air pressure vibration is reduced.

In order to reduce the air pressure vibration and reduce the pressure, for example, the size, shape, rotation speed, control method, duct, Length, diameter, shape, drying room 1
This can be achieved by suppressing the source of vibration, such as the size of 1, 51. Further, a method of sealing the front and rear of the casting dies 12 and 52 with a sealing material so as not to transmit the pneumatic vibration of other zones can be adopted. Further, a method is also preferable in which openings are provided in the drying chambers 11 and 51 around the casting dies 12 and 52 to release air pressure vibration. When the opening is provided, if the organic solvent gas leaks out of the drying chamber, it is not preferable from an environmental point of view. Therefore, it is preferable to shield the outside air with a material having low rigidity such as a resin thin film. When a thin film material is used, the pressure difference between the inside and outside of the drying chamber is preferably maintained at 9.8 Pa (1 mmAq) or less in order to sufficiently absorb vibration. Of course, it is preferable to eliminate mechanical vibration sources around the casting die as much as possible.

The film for a liquid crystal display device according to the present invention comprises:
It can be used for various films used in liquid crystal display devices, for example, a polarizing plate protective film, an optical compensation film,
Although it can be used for plastic cells and the like, it is particularly preferable to use it as a polarizing plate protective film. Less than,
The case where the liquid crystal display device film is used as a polarizing plate protective film will be described.

On the surface of the polarizing plate protective film, JP-A-Hei 4-
229828, JP-A-6-75115, JP-A-8-50206, etc., an optically anisotropic layer for compensating a viewing angle of a liquid crystal display device and an antiglare layer for improving the visibility of a display. Or anti-reflection layer, layer having PS wave separation function by anisotropic scattering or anisotropic optical interference for improving the brightness of liquid crystal display device (polymer dispersed liquid crystal layer, cholesteric liquid crystal layer, etc.), scratch resistance of polarizing plate Arbitrary functional layers such as a hard coat layer for improving the diffusion, a gas barrier layer for suppressing the diffusion of moisture and oxygen, a polarizing film or an adhesive layer, an adhesive layer for enhancing the adhesion to an adhesive, and a layer for imparting slipperiness are provided. be able to.

The functional layer may be provided on the polarizing film side or on the opposite surface to the polarizing film, and can be appropriately selected according to the purpose.

The polarizing plate protective film is used as a polarizing plate by being bonded to a polarizing film. Generally, a polarizing plate is manufactured by adhering a protective film to at least one side of a polarizing film produced by adsorbing and orienting a dichroic substance on a base film. As the base polymer, a PVA-based polymer is generally used. As the dichroic substance, iodine or a dichroic dye is used alone or in combination.

The PVA used for the polarizing film is usually obtained by saponifying polyvinyl acetate. For example, a component copolymerizable with vinyl acetate such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins and vinyl ethers. May be contained. Modified P containing acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group, etc.
VA can also be used. Although the saponification degree of PVA is not particularly limited, it is preferably from 80 to 100 mol%, and from 90 to 100 mol%, from the viewpoint of solubility, polarization, heat resistance, moisture resistance and the like.
ol% is particularly preferred. The degree of polymerization of PVA is not particularly limited, but is preferably from 1,000 to 10,000 from the viewpoint of film strength, heat resistance, moisture resistance, stretchability, and the like, and is preferably from 1500 to 50,000.
00 is particularly preferred. Further, the syndiotacticity of PVA is not particularly limited, and can take any value depending on the purpose.

The procedure for dyeing and stretching PVA to obtain a polarizing film includes a method of stretching a raw PVA film by dry or wet method and then immersing the film in a solution of iodine or a dichroic dye, iodine or dichroic dye. And a method in which a PVA film is stretched and oriented in a solution of a chromatic dye, and a method in which a PVA film is immersed in iodine or a dichroic dye and then stretched and oriented in a wet or dry system. In addition, when the raw PVA film is formed by the solution film forming method, a method of previously including a dichroic substance in the PVA solution can be used.

A method for producing a typical polarizing plate by wet stretching will be described below. First, the raw PVA film is pre-swelled with an aqueous solution. Next, it is immersed in a dichroic substance solution to adsorb the dichroic substance. Further, the film is uniaxially stretched in the traveling direction in an aqueous solution of a boron compound such as boric acid. If necessary, a color adjustment bath, a curing bath, and the like may be provided after this. After drying to some extent, the protective film is bonded using an adhesive such as PVA. Further drying, a polarizing plate is obtained.

Various organic solvents, inorganic salts, plasticizers, boric acids and the like may be added to the pre-swelling liquid in the aqueous solution.

As an example of the dyeing solution, an iodine-potassium iodide aqueous solution is used when iodine is used as the dichroic substance. Preferably, iodine is 0.1 to 20 g / l, potassium iodide is 1 to 100 g / l, and the weight ratio of iodine to potassium iodide is 1 to 100.

The dyeing time is preferably 30 to 5000 seconds,
The liquid temperature is preferably 5 to 50C. It is also preferable to include a compound that crosslinks PVA such as a boron compound in the dyeing solution.

The boron compound in the stretching bath is particularly preferably boric acid. The boric acid concentration is preferably 1 to 200 g / l.
And more preferably 10 to 120 g / l.
The stretching bath may contain, in addition to the boron compound, an inorganic salt such as potassium iodide, various organic solvents, or a dichroic dye.

The color adjusting bath and the curing bath contain, as necessary, an inorganic salt such as potassium iodide, a boron compound, and the like, in addition to the dichroic dye.

As a stretching step of PVA, a method of applying tension in the traveling direction of the continuous film and stretching and orienting the film in the traveling direction as described above is generally used.
A method of applying tension in the width direction of the film by a stretching means such as a so-called tenter method to orient the film in the width direction is also applicable.

The stretching is preferably performed three times or more in the uniaxial direction, more preferably 4.5 times or more. Biaxial stretching may be performed depending on the purpose of use of the polarizing film. Although the film thickness after stretching is not particularly limited, it is preferably from 5 to 100 μm, more preferably from 10 to 40 μm, from the viewpoint of handleability, durability and economy.

The temperature at the time of stretching depends on the stretching conditions, but is usually from 10 to 250 ° C. When the dry stretching is performed at a temperature of 100 ° C. or more, it is preferable to perform the stretching in an inert gas atmosphere such as nitrogen. In addition, it is preferable to perform a crystallization treatment at a temperature of 100 ° C. or more before dyeing the previously stretched film.

As a dyeing method, not only the dipping method exemplified above, but also any means such as coating or spraying of iodine or a dye solution is possible. In addition, not only the liquid layer adsorption described above but also the gas phase adsorption can be performed as needed.

It is also preferable to dye with a dichroic dye. Specific examples of dichroic dyes include, for example, dye compounds such as azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. I can give it. Water-soluble ones are preferred, but not limited thereto. Further, it is preferable that a hydrophilic substituent such as a sulfonic acid group, an amino group, or a hydroxyl group is introduced into these dichroic molecules. Representative examples of dichroic molecules include C.I.Direct Yellow 12, C.I.Direct Orange 39, C.I.Direct Orange 72, and C.I.Direct Red 2.
8, sea eye direct red 39, sea eye direct red 79, sea eye direct
Red 81, C I Direct Red 83, C I Direct Red 89, C I Direct Violet 48, C I Direct
Blue 67, C.I.Direct Blue 90, C.I.Direct Green 59, C.I. Acid Red Red 37, and the like.
No. 61202, JP-A-1-172906, JP-A-1-172906
No. 172907, JP-A-1-183602, JP-A-1
And the dyes described in JP-A-248105, JP-A-1-265205 and JP-A-7-261024. In particular, CI Direct Red 28
(Congo red) has long been known as preferred for this application. These dichroic molecules are used as a free acid or a salt of an alkali metal salt, an ammonium salt or an amine. By mixing two or more of these dichroic molecules, polarizers having various hues can be produced. As a polarizing element or a polarizing plate, a compound (dye) which exhibits black when the polarization axes are orthogonal to each other or a compound in which various dichroic molecules are blended so as to exhibit black are excellent in single-plate transmittance and polarization, and thus are preferable.

From the viewpoint of improving the heat resistance and moisture resistance of the polarizing film,
It is preferable to include an additive that crosslinks PVA in the polarizing film manufacturing process. As the cross-linking agent, those described in U.S. Pat. No. 2,328,979 can be used, but boric acid and borax are practically preferably used.

Also, zinc, cobalt, zirconium,
It is also preferable to include a metal salt such as iron, nickel, and manganese in the polarizing film because it is known to improve durability.

These crosslinking agents and metal salts may be contained in any of the above-described steps such as the pre-swelling bath, the dichroic substance dyeing bath, the stretching bath, the curing bath, and the color adjusting bath. Is not particularly limited.

The adhesive for bonding the protective film and the polarizing film is not particularly limited, and any known adhesive such as PVA, modified PVA, urethane, and acrylic can be used. The thickness of the adhesive layer is preferably from 0.01 to 20 μm, more preferably from 0.1 to 10 μm.

One or more polarizing plate protective films can be used. The same polarizing plate protective film may be bonded to both surfaces of the polarizing film, or polarizing plate protective films having different functions and physical properties may be bonded to both surfaces. In addition, the polarizing plate protective film of the present invention is bonded to only one surface, and the liquid crystal cell is directly bonded to the opposite surface of the polarizing film. Is also possible. In this case, it is preferable to provide a peelable separator film outside the adhesive.

It is also preferred that the polarizing plate protective film of the present invention is bonded to one surface of the polarizing film, and that various types of functional films are directly bonded to one or both surfaces as a protective film on the opposite surface of the polarizing film. Examples of the functional film include a retardation film such as a λ / 4 plate and a λ / 2 plate, a light diffusion film, a plastic cell having a conductive layer provided on the surface opposite to the polarizing plate, anisotropic scattering and anisotropic optical interference. Examples include a brightness enhancement film having a function, a reflector, and a reflector having a semi-transmissive function.

The adhesive for bonding the polarizing plate protective film and the polarizing film is not particularly limited, and may be PVA-based, modified PVA.
Any known materials such as a system, a urethane system, and an acrylic system can be used. The thickness of the adhesive layer is 0.01 to 2
0 μm is preferable, and 0.1 to 10 μm is more preferable.

The polarizing plate of the present invention preferably has a higher transmittance from the viewpoint of increasing the contrast of the liquid crystal display device.
The higher the degree of polarization, the better. Transmittance is preferably 30%
Or more, more preferably 40% or more. The degree of polarization is preferably at least 95.0%, more preferably at least 99%, particularly preferably at least 99.9%.

The liquid crystal display device of the present invention is formed by using the above-described polarizing plate, that is, the polarizing plate is provided on at least one of the two polarizing plates disposed on both sides of the liquid crystal cell. Used. The liquid crystal cell is not particularly limited, and a conventionally used liquid crystal cell can be used.

[0086]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[Preparation of Raw Material Dope] (Preparation of Fine Particle Dispersion a) Silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) 0.67% by weight Cellulose acetate (degree of substitution 2.8) 2.93% by weight Triphenyl phosphate 0.23% by weight Biphenyl diphenyl phosphate 0.12% by weight Methylene chloride 88.37% by weight Methanol 7.68% by weight was prepared, and the volume average particle diameter was 0.3% with an attritor.
Dispersion was performed to 7 μm.

(Preparation of Raw Material Dope A) Cellulose triacetate (degree of substitution: 2.8) 89.3% by weight Triphenyl phosphate 7.1% by weight Biphenyl diphenyl phosphate 3.6% by weight Based on 100 parts by weight of a solid content. Then, 17.9 parts by weight of the fine particle dispersion a was added, and a mixed solvent of 92% by weight of dichloromethane and 8% by weight of methanol was appropriately added thereto, followed by stirring and dissolution to prepare a dope. The solid content of the dope was 18.5% by weight. This dope was filtered through filter paper (Toyo Roshi Kaisha Co., Ltd., “$ 63”) and then sintered metal filter (Nippon Seisen Co., Ltd.)
“06N”, nominal pore size 10 μm), and further filtered through a mesh filter (“RM”, manufactured by Nippon Pall Co., Ltd., nominal pore size 45 μm).

(Preparation of UV Absorbent Solution b) 2 (2′-Hydroxy-3 ′, 5′-di-tert-butylphenyl-5-chlorobenzotriazole) 5.83% by weight 2 (2′-hydroxy- 3 ', 5'-di-tert-amylphenyl) benzotriazole 11.66 wt% cellulose acetate (degree of substitution: 2.8) 1.48 wt% triphenylphosphate 0.12 wt% biphenyldiphenylphosphate 0. 06% by weight Methylene chloride 74.38% by weight Methanol 6.47% by weight

An ultraviolet absorber solution was prepared according to the above-mentioned formulation, and was filtered with “Astrophore 10 filter” manufactured by Fuji Photo Film Co., Ltd.

Example 1 The above-mentioned UV absorbent solution b was added to the above-mentioned dope A using a static mixer, and the amount of the UV absorbent was 1.04% by weight based on the solid content in the dope.
The dope was added and mixed in the piping route while adjusting so as to be.

Using this dope, a film was produced by a band casting method production apparatus shown in FIG. That is, the dope was cast from a casting die 52 to a casting band 53, and hot air was blown onto the upper and lower portions of the casting band 53 to dry it until it had a self-supporting property. At this time,
The moving speed of the casting band 53 is 30 m / min, and the distance between the discharge port 52a of the casting die 52 and the casting band 53 is
1.7 mm. The drying air fan for sending the drying air to the casting band 53, the duct length, and the duct shape were optimized so as to suppress the air pressure vibration measured around the casting die 52. An opening was provided in the drying chamber 51 around the casting die 52, and a 10-μm polyethylene membrane was used to shut off the outside air. The maximum air pressure vibration around the casting die 52 is 8.82 Pa near 14 Hz.
(0.9 mmAq).

This film is dried in the drying chamber 6 of the stretching drying section 60.
The film was dried while applying tension while holding both ends of the film with holding means 62 of a tenter type dryer. next,
After being introduced into the roller drying unit 70 and dried, the core 8
Rolled up at 0. The thickness of the completed film was 80 μm. Table 1 shows the evaluation results of the change in thickness and the evaluation results of the film surface state.

Example 2 The above-mentioned dope A was mixed with the above-mentioned ultraviolet absorbent solution b using a static mixer, and the amount of the ultraviolet absorbent was 2.08% by weight based on the solid content in the dope.
The dope was added and mixed in the piping route while adjusting so as to be.

Using this dope, a film was produced by the production apparatus of the band casting method shown in FIG. That is, the dope was cast from the casting die 52 to the casting band 53, and hot air was blown only to the lower portion without blowing hot air to the upper portion of the casting band 53, and the dope was dried until it had self-supporting property. . At this time, the moving speed of the belt 53 is 2
The distance between the discharge port 52a of the casting die 52 and the belt 53 was 1.5 mm. The drying air fan, duct length, and duct shape were the same as in Example 1. Further, similarly to Example 1, an opening was provided in the drying chamber 51 around the casting die 52, and the air was blocked from the outside air by a 10-μm polyethylene film. The maximum air pressure vibration around the casting die 52 is 8.82 Pa (0.9 mmA) around 14 Hz.
q).

This film is dried in the drying chamber 6 of the stretching drying section 60.
The film was dried while applying tension while holding both ends of the film with holding means 62 of a tenter type dryer. next,
After being introduced into the roller drying unit 70 and dried, the core 8
Rolled up at 0. The thickness of the completed film was 40 μm. Table 1 shows the evaluation results of the change in thickness and the evaluation results of the film surface state.

Example 3 A film was produced in the same manner as in Example 2 except that the moving speed of the belt 53 was 33 m / min. The air pressure vibration around the casting die 52 is 5-100H.
In the range of z, it was 19.60 Pa (2.0 mmAq) or less. Table 1 shows the evaluation results of the change in thickness and the evaluation results of the film surface state.

[Comparative Example 1] The drying air fan at the lower part of the belt 53 was changed, and the outside air shut-off means at the opening of the drying chamber 51 was changed to S.
A film was produced in the same manner as in Example 1 except that a US plate was used. As for the air pressure vibration around the casting die 52, 21.56 Pa (2.2 mmAq) was observed around 13 Hz, and 24.50 Pa (2.5 mmAq) was observed around 22 Hz. Table 1 shows the evaluation results of the change in thickness and the evaluation results of the film surface state.

[Comparative Example 2] The drying air fan at the lower part of the belt 53 was changed, and the outside air shut-off means at the opening of the drying chamber 51 was changed to S.
A film was produced in the same manner as in Example 2, except that a US plate was used, and the distance between the die discharge port 52a and the belt 53 was 2.5 mm. The air pressure vibration around the casting die is 13H
20.58 Pa (2.1 mmAq) near 22z, 22Hz
22.54 Pa (2.3 mmAq) was observed in the vicinity. Table 1 shows the evaluation results of the change in thickness and the evaluation results of the film surface state.

<Measurement of Air Pressure Vibration> In Examples 1 to 3 and Comparative Examples 1 and 2, the measurement of the air pressure vibration around the casting die was performed by first inserting one end of a tube near the casting die.
The other end is manufactured by ST R & D Co., Ltd., "Micro differential pressure gauge Spec
ial Transducer PD80A + PU12-
A "and measure the air pressure fluctuation. This is measured by Ono Sokki Co., Ltd.
S-9100 "and" General-purpose FFT analysis software DS
−0921 ”to separate the components into frequency components, and the vibration intensity of each component was determined.

(Saponification of Film) Examples 1-3
The films of Comparative Examples 1 and 2 were treated with 1.5N NaOH at 50 ° C.
After treating with an aqueous solution for 180 seconds, neutralization and washing were performed, followed by drying.

(Preparation of Polarizing Plate) "PV" manufactured by Kuraray Co., Ltd.
A film ”(75 μm) is immersed in an aqueous solution of 5.0 g / l of iodine and 10.0 g / l of potassium iodide at 25 ° C., and then boric acid 40 g / l and potassium iodide 30 g / l
1 and immersed in a 10 g / l aqueous solution of zinc chloride at 25 ° C. for 120 seconds. This is stretched 4.5 times, and 60
It dried at 10 degreeC for 10 minutes, and produced the polarizing film. The polarizing film is removed from the stretching machine, and PVA (manufactured by Kuraray Co., Ltd., “PVA-11
7H ") The films of Examples 1 to 3 and Comparative Examples 1 and 2 which were subjected to a saponification treatment using a 4% aqueous solution as an adhesive were laminated on both sides, and further dried at 80 ° C. to obtain a polarizing plate. The immersion time of the film in the staining solution was appropriately adjusted so that the transmittance of the polarizing plate was 41 ± 0.5%. The polarization degree of the obtained polarizing plate is 9
9.7 to 99.9%.

<Transmissivity of Polarizing Plate> Shimadzu Spectrophotometer UV-3
The transmittance was measured at 100 PC, and was calculated from the spectral transmittance τ (λ) obtained every 10 nm according to the following equation. In the formula, P (λ) is a standard light D65 according to JISZ8720.
The spectral distribution y (λ) of the light source is a color matching function based on a two-degree visual field X, Y, Z system according to JIS Z8701. Transmittance T (%) = A / B × 100 A = _∫vis P (λ) · y (λ) · τ (λ) dλ B = _∫vis P (λ) · y (λ) dλ (vis: 400
~ 700nm)

<Polarization degree of polarizing plate> The polarization degree was calculated by the following equation. Degree of polarization P (%) = {(Tp−Tc) / (Tp + Tc)}
^×× 100 where Tp is the transmittance (%) when the absorption axes of the two polarizing plates are superposed in parallel on a sample obtained by superimposing the two polarizing plates, and Tc is the transmittance of the two polarizing plates. The transmittance (%) when the absorption axes are vertically overlapped. Table 1 shows the evaluation results of the planar state of the polarizing plate.

[0105]

[Table 1]

<Evaluation of ΔDmax, N> A sample of 40 mm width × 1000 mm length was cut out from the center of the film, and was manufactured by Anritsu Electric Co., Ltd., “Continuous thickness meter FILM T”.
HICKNESS TESTER KG601A ”, the thickness was continuously measured, and data obtained by sampling data at intervals of 1 mm over a continuous length of 500 mm was defined as X (0) to X (500) (μm).
The thickness change ΔD (n) per 1 mm is calculated based on the following formula: ΔDm
ax.

.DELTA.D is arranged in the order of data collection, and after .DELTA.D (n) exceeds 0.10 and falls again below 0.10, one area is defined as one area. . That is, the thickness change ΔD (n) (μ
m) changes from the non-thickness increasing region that does not satisfy the following formula (3) to a satisfactory thickness increasing region and further becomes a non-thickness increasing region that does not satisfy the following formula (3). The number of peak regions consisting of the increase region was set to N. ΔD> 0.10 Equation (3)

<Evaluation of Film Transmission Surface Condition> Substantially parallel light was projected from the back surface of the film, a white screen was placed on the opposite surface, and the projected shadow was visually evaluated. A: No stripe pattern is observed in the projected image. B: A slight stripe pattern is observed in the projected image, but the contrast is weak. C: A stripe pattern is clearly observed in the projected image. D: The stripe pattern of the projected image looks very prominent, and a clear cycle is observed.

<Evaluation of film reflection surface condition> 1340 mm width x
The film having a length of 2000 mm was spread on a black cloth, irradiated with fluorescent light from directly above, visually observed from an oblique direction, and the degree of waving of the film was determined based on the distortion of the reflected image of the fluorescent light. A: No undulation is observed. B: Rippling is slightly observed depending on the observation angle. C: Rippling is observed from a wider angle. D: Rippling is remarkably observed.

<Evaluation of Polarizing Plate Surface Condition> 190 mm × 150 mm
The polarizing plate was spread on a black cloth, irradiated with fluorescent light from directly above, visually observed from an oblique direction, and the deformation of the polarizing plate surface was determined based on the distortion of the reflected image of the fluorescent lamp. A: No undulation is observed. B: Rippling is slightly observed depending on the observation angle. C: Rippling is observed from a wider angle.

[0111]

According to the present invention, by keeping the thickness change in the longitudinal direction of the film at a certain level or less, it is possible to make it difficult to visually recognize the stripe pattern caused by the thickness unevenness in the longitudinal direction. In addition, by making the number of thickness changes exceeding a specific value within a certain length equal to or less than a certain value, it is possible to make it difficult to visually recognize a striped pattern caused by thickness unevenness. In particular, it was very suitable for a thin film of 20 to 60 μm.

Further, a specific component of pneumatic vibration in an atmosphere in which the dope is discharged from the casting die is adjusted to 19.60 Pa or less, and a film having a dry thickness of 20 to 60 μm is produced at a moving speed of the endless support. By manufacturing at a rate of 30 m / min or more, it is possible to suitably manufacture a film in which the above-mentioned striped pattern is difficult to visually recognize.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for producing a film by a casting drum type solution casting method.

FIG. 2 is a schematic view of an apparatus for producing a film by a casting band type solution casting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Casting part 11 ... Drying chamber 12 ... Casting die 13 ... Casting band 20 ... Stretching drying part 21 ... Drying chamber 22 ... Holding part 30 ... Drying part 31 ... Transport roll 40 ... Core 50 ... Casting part 51 ... drying chamber 52 ... casting die 53 ... casting band 60 ... stretching drying section 61 ... drying chamber 62 ... holding section 70 ... drying section 71 ... transport roll 80 ... core

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29C 41/52 B29C 41/52 G02F 1/13363 G02F 1/13363 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 F term (reference) 2H049 BA02 BA27 BB18 BB33 BB43 BC01 BC03 BC22 2H091 FA08X FA08Z GA16 LA30 4F205 AA01 AC05 AG01 AH73 AM26 AR08 GA07 GB02 GC02 GC07 GF24 GN24

Claims (4)

[Claims] 1. A thickness data sampled at intervals of 1 mm over a continuous length of 500 mm in the longitudinal direction is represented by X
(0) to X (500) (μm), a thickness change ΔD (n) (μm) per mm is calculated based on the following equation (1), and ΔD (n) = X (n) −X ( n-1) Expression (1) The largest one among ΔD (1) to ΔD (500) is ΔDm
A film for a liquid crystal display device, wherein, when ax is defined, ΔDmax has a relationship represented by the following formula (2). ΔDmax <0.30 Expression (2) 2. Thickness data sampled at intervals of 1 mm over a continuous length of 500 mm in the longitudinal direction is represented by X
(0) to X (500) (μm), a thickness change ΔD (n) (μm) per mm is calculated based on the following equation (1), and ΔD (n) = X (n) −X ( n-1) Formula (1) This thickness change ΔD (n) (μm) changes from a non-thickness increasing region not satisfying the following expression (3) to a satisfactory thickness increasing region, and further unsatisfactory non-thickness increasing. When it becomes an area,
A film for a liquid crystal display device, wherein the number N of the peak regions including the non-thickness increasing region, the thickness increasing region, and the non-thickness increasing region has a relationship represented by the following formula (4). ΔD> 0.10 Expression (3) N <25 Expression (4) 3. A method for producing a film by dissolving cellulose acylate in a solvent to prepare a dope, casting the dope on an endless support from a casting die, continuously peeling it off, and drying it. In the frequency resolution component of the air pressure vibration in the atmosphere where the dope is discharged from the casting die, the air pressure vibration in the range of 5 to 100 Hz is 19.60.
A method for producing a film for a liquid crystal display device, which is not more than Pa (2.0 mmAq). 4. A dope is prepared by dissolving cellulose acylate in a solvent, and the dope is cast on an endless support from a casting die, continuously peeled off, and dried to a dry thickness of 20 to 60 μm. A method for producing a film for a liquid crystal display device, wherein the moving speed of the endless support is 30 m / min or more.