JP2002363341A - Cellulose ester film, optical film and process for production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose ester film excellent in surface properties and free from contamination in the production step, with excellent productivity, and to provide an optical film, and a process for production thereof. SOLUTION: The cellulose ester film is characterized in that it has a solubility in a solvent comprising a 50:50 (mass%) methylene chloride : ethanol mixture at 20 deg.C of 10 g/100 ml or higher and contains an ultraviolet absorber which is solid at 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film used for optical applications, and more particularly, to a protective film for a polarizing plate, a retardation film used for a liquid crystal display device and the like.
The present invention relates to an optical film that can be used for various functional films such as a viewing angle widening film and an antireflection film used for a plasma display, and various functional films used for an organic EL display and the like, and a method for manufacturing the same. .

[0002] More specifically, the present invention relates to a method for producing a cellulose ester film which has low process contamination and is excellent in productivity.

[0003]

2. Description of the Related Art An optical film is preliminarily mixed with an ultraviolet absorbent such as a benzotriazole compound or a benzophenone compound, a cyanoacrylate compound or a salicylic acid compound to form a film. Was prevented from deteriorating. In recent years, notebook computers and liquid crystal monitors have been developed to have larger screens, higher definition, and thinner and lighter weight. Along with this, the demand for higher performance and thinner protective films for liquid crystal polarizers has been increasing. However, even when the optical film is made thinner, the ultraviolet cut performance required for the optical film does not change, so that as the film becomes thinner, the amount of the ultraviolet absorber added to the solid content in the film tends to increase. If the amount of the ultraviolet absorber proposed so far is increased, there is a problem that the inside of the film forming process is contaminated. If the inside of the process is contaminated, the contaminant adheres to the transport roll and is pushed to cause a failure, thereby deteriorating the film yield.

[0004] In addition, the surface properties of optical films have become more severe with higher definition. Therefore, the film is stretched in the width direction by a tenter at the time of film production to increase the smoothness of the film and produce a film having excellent surface properties. Stretching in the width direction by a tenter is more effective if heat is applied with high residual solution. However, when heat is applied with a high residual solution, evaporation of the ultraviolet absorbent is apt to occur, and the amount of added ultraviolet absorbent is reduced, the ultraviolet absorption performance is reduced, and the production process is contaminated, which causes various problems.

[0005] With respect to the ultraviolet absorber, JP-A-6-13
Nos. 0226 and 7-11056 have been proposed, but satisfactory results have not yet been obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical film excellent in surface properties, free from process contamination and excellent in productivity, and a method for producing the same. To provide.

[0007]

The above object of the present invention has been attained by the following constitutions.

[0008] 1. Methylene chloride: ethanol = 5
A cellulose ester film having a solubility of 0:50 (% by mass) at 20 ° C. in a solvent of 10 g / 100 ml or more and containing an ultraviolet absorber which is solid under an atmosphere of 20 ° C.

[0009] 2. The 10% by mass disappearance temperature of thermal mass spectrometry is
A cellulose ester film comprising an ultraviolet absorber having a temperature of 230 to 450 ° C.

[0010] 3. In the method for producing an optical film by a solution casting film forming method, the resin solution containing the ultraviolet absorbent described in 1 or 2 above is cast on a support, dried on the support, and then peeled off. A method for producing an optical film, comprising stretching in the width direction by 0 to 100%.

4. 4. The method for producing an optical film according to the above item 3, wherein the resin solution containing an ultraviolet absorber contains methyl acetate.

5. An optical film manufactured by the method according to the above item 3 or 4. 6. 6. The optical film according to the above item 5, wherein the resin of the resin solution containing the ultraviolet absorbent is a cellulose ester.

7. 7. A polarizing plate comprising the optical film according to 5 or 6 above. 8. 7. A display device using the optical film according to 5 or 6 above.

Hereinafter, the present invention will be described in more detail. A preferred film forming step used in the method for producing a cellulose ester film of the present invention includes a dissolving step shown below,
It comprises a casting step, a solvent evaporation step, a peeling step, a drying step and a winding step. Hereinafter, each step will be described.

<< Solution Step >> In the present invention, the cellulose ester solution is called a cellulose ester dope or simply a dope. The dissolving step is a step of dissolving the flakes in cellulose ester flakes in a dissolving vessel in an organic solvent mainly composed of a good solvent described below while stirring to form a dope.

In the present invention, the solid concentration in the dope is 15%.
It is preferable to adjust the amount to not less than 18% by mass.
% By mass is preferably used.

If the solid content concentration in the dope is too high, the viscosity of the dope becomes too high, and sharkskin or the like may be formed during casting to deteriorate the film flatness.
It is desirable that the content is not more than mass%.

Preferably, the viscosity of the dope is adjusted in the range of 10 to 50 Pa · s. For the dissolution, a method performed at normal pressure, a method performed at a temperature lower than the boiling point of a preferable organic solvent (that is, a good solvent), a method performed at a pressure higher than the boiling point of the good solvent,
There are various dissolution methods, such as a method using a cooling dissolution method and a method using a high pressure. As a method of dissolving at a temperature not lower than the boiling point of a good solvent and applying a pressure that does not cause boiling, 40.4 to 12
By applying a pressure of 0.11 to 1.50 MPa at 0 ° C., foaming can be suppressed and dissolution can be performed in a short time.

As the cellulose ester used in the present invention, a lower fatty acid ester of cellulose is preferably used.

The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, for example, cellulose acetate, cellulose propionate, cellulose butyrate, and the like.
Examples of mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in U.S. Pat. Nos. 0-45804 and 8-231762 and U.S. Pat. No. 2,319,052 are examples of lower fatty acid esters of cellulose. It is listed as.

Particularly preferably, the total degree of substitution is from 2.55 to 2.
85 cellulose esters are preferably used.

The method for measuring the degree of substitution of the acyl group in the cellulose ester can be carried out according to ASTM-D-817-96.

Of the above fatty acids, cellulose acetate and cellulose acetate propionate are preferably used. In the case of the cellulose ester film of the present invention, from the viewpoint of film strength, the polymerization degree is particularly preferably from 250 to 250.
400 are preferably used.

As the cellulose ester film of the present invention, a cellulose ester having a total degree of substitution of 2.5 to 3.0 is preferably used, and a cellulose ester having a total degree of substitution of 2.55 to 2.85 is particularly preferably used. When the total substitution degree is 2.55 or more, the mechanical strength of the film increases,
When it is 2.85 or less, the solubility of the cellulose ester is improved and the generation of foreign matters is reduced, so that it is more preferable.

In the case of cellulose acetate propionate, the degree of acetyl group substitution is X and the degree of propionyl group substitution is Y
Then, 2.55 ≦ X + Y ≦ 2.851.5 ≦ X ≦ 2.
Those in the range of 4 are preferably used.

As the cellulose ester, a cellulose ester synthesized from cotton linter, a cellulose ester synthesized from wood pulp, and a cellulose ester synthesized from other raw materials can be used alone or in combination.

The solvent used for preparing the dope is not particularly limited as long as it is a solvent capable of dissolving the cellulose ester. Even if the solvent cannot be dissolved alone, it can be mixed with another solvent. Any substance that can be dissolved can be used. Generally, a mixed solvent composed of a poor solvent of methylene chloride and a cellulose ester, which is a good solvent, is used.
Those containing 30% by mass are preferably used.

Other good solvents that can be used include, for example, methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2 2-trifluoroethanol, 2,
2,3,3-tetrafluoro-1-propanol, 1,
3-difluoro-2-propanol, 1,1,1,3,
3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1
-Propanol, nitroethane and the like can be mentioned, and organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferable organic solvents (that is, good solvents). The use of methyl acetate is particularly preferred because the resulting film has less curl.

As the poor solvent for the cellulose ester, for example, methanol, ethanol, n-propanol, is
Alcohols having 1 to 8 carbon atoms such as o-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, monochlorobenzene,
Examples thereof include benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. These poor solvents can be used alone or in appropriate combination of two or more kinds.

In the production of the cellulose ester film of the present invention, it is preferable to use a cooling dissolution method when dissolving the cellulose ester. As a cooling dissolution method,
For example, JP-A-9-95538 and JP-A-9-95544,
The method described in JP-A-9-95557 can be used. Also, the high-pressure dissolution method described in JP-A-11-21379 can be preferably used.

After dissolution, cellulose ester solution (dope)
Is preferably filtered through a filter medium, defoamed and sent to the next step by a pump.At that time, in the dope, a plasticizer, an antioxidant, an ultraviolet absorber, a dye, fine particles and the like are preferably added. .

These additives may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared.

A plasticizer can be added to the cellulose ester film of the present invention. Examples of the plasticizer that can be used include, but are not limited to, a phosphate ester plasticizer, a phthalate ester plasticizer, and a citrate ester plasticizer. Phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.Phthalate esters include diethyl phthalate, dimethoxyethyl phthalate , Dimethyl phthalate, dioctyl phthalate,
Dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, dibenzyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like, as citric acid ester plasticizer, Triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate and the like can be preferably used.

It is preferable to use these alone or in combination, and these plasticizers may be used in combination of two or more as necessary. The amount of the plasticizer to be used is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, further preferably 2 to 15% by mass, particularly preferably 3 to 12% by mass, based on the cellulose ester. % By mass.

The cellulose ester film of the present invention may contain an additive having the same effect as the plasticizer, in addition to the above-mentioned plasticizer. As long as these additives are low molecular weight organic compounds capable of plasticizing the cellulose ester film, the effects of the present invention can be obtained in the same manner as the plasticizer. These components are not added for the purpose of directly plasticizing the film as compared with the plasticizer, but exhibit the same action as the above-mentioned plasticizer depending on the amount.

The ultraviolet absorbent used in the present invention is an ultraviolet absorbent having a 10% mass extinction temperature of 230 to 450 ° C. in thermal mass analysis, preferably 250 ° C. or higher, more preferably 275 ° C. or higher, and more preferably 300 ° C. or higher. Is most preferred. 1
The higher the 0% mass disappearance temperature, the less the evaporation of process contamination and the better. The structure is not particularly limited, and examples include the following compounds.

[0037]

Embedded image

[0038]

Embedded image

[0039]

Embedded image

The ultraviolet absorbent used in the present invention has a solubility in a solvent of methylene chloride: ethanol = 50: 50 (% by mass) at 20 ° C. of 10 to 150 g.
/ 100 ml or more, and an ultraviolet absorber having a melting point of 20 ° C. or more is preferable. The solubility is more preferably 20 g / 100 ml or more, and most preferably 30 g / 100 ml or more. The higher the solubility is, the better the roll contamination of process contamination is. The structure is not particularly limited, and examples thereof include the following compounds.

[0041]

Embedded image

As these compounds, those commercially available from Sumitomo Chemical Co., Ltd. and Chemipro Kasei Co., Ltd. can be used.

The mass loss temperature at 10% of the thermal mass spectrometry was 230.
UV absorber having a solubility in a solvent of methylene chloride: ethanol = 50: 50 (mass%) at 20 ° C. of 10 g / 100 ml or more and a melting point of 20 ° C. or more. It is most preferable because there is no evaporation and no roll contamination.

Evaporation of process contamination occurs during the drying of the film,
A phenomenon in which the ultraviolet absorber evaporates and adheres to the walls and ceilings of the process, etc.If the amount of adhesion increases, it falls on the base and causes a foreign matter failure, or falls on a roll and adheres, causing a failure due to being pushed. Or Roll contamination as a process contamination is a phenomenon in which an ultraviolet absorbent adheres to the roll immediately after the film peeling step. In particular, the process contamination tends to increase when the stretching ratio in performing the tenter process described later increases or when the drying temperature in the tenter process is increased. The ultraviolet absorbent of the present invention is more effective when combined with a tenter treatment.

The pressing failure is a failure in which the film is deformed by foreign matter on the roll. Unlike a normal foreign matter failure, there is no nucleus substance on the film, but at the same location in the film width direction at intervals of the roll cycle. This is a failure that occurs continuously.

A conventionally known ultraviolet absorber can be used in combination. Examples of conventionally known ultraviolet absorbers include, for example, oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, triazine-based compounds, cyanoacrylate-based compounds, nickel complex-based compounds, inorganic powders, and the like. .

The above-mentioned UV absorber preferably used as the UV absorber used in combination in the present invention has high transparency and is excellent in the effect of preventing deterioration of the polarizing plate and the liquid crystal element. Agents and triazine-based UV absorbers are preferred, and benzotriazole-based UV absorbers with less unnecessary coloring are particularly preferred.

In particular, the ultraviolet absorber added to the cellulose ester film of the present invention is preferably an ultraviolet absorber having a distribution coefficient of 8.5 or more. If the UV absorber is less than 8.5, foreign matter failure tends to increase, particularly when fine particles described below are added. The distribution coefficient is 8.5
The use of the above ultraviolet absorber has an effect of reducing the moisture permeability. In the present invention, the distribution coefficient is more preferably 9.0 or more, and further preferably 10.0 or more. Further, those containing no halogen in the molecule are more preferable.

The partition coefficient is a logarithm of the partition ratio (P _{o / w} ) of octanol and water which can be defined by the following equation.

Partition coefficient = log P _{o / w} P _{o / w} = So / Sw So: Solubility of the organic compound in n-octanol at 25 ° C. Sw: Solubility of the organic compound in pure water at 25 ° C. Can be measured using n-octanol and water as described above, but in the present invention, these partition coefficients were calculated by HPLC. This is a method using high performance chromatography, which is described in the OECD Guideline 117 partition coefficient (n-octanol / water) high performance chromatography (adopted on March 30, 1989). Shown in

Apparatus: LC module (manufactured by Waters) Column: Inertsil ODS-2 250 mm × 4.6
mm (manufactured by GL Sciences) Temperature: 40 ° C. Eluent: methanol: 1% phosphoric acid aqueous solution = 90: 10 Flow rate: 1.0 ml / min Detection wavelength: 210 nm Injection sample: methanol solution of about 50 ppm UV absorber alone It may be used, or a mixture of two or more kinds. The amount of use may vary depending on the kind of the compound, the use conditions, etc., but 0.2 to 5.0 g per 1 m ^{2 of} the cellulose ester film. Preferably, 0.4
~ 2.0 g is more preferred.

From the viewpoint of preventing deterioration of the liquid crystal, a wavelength of 370 n
From the viewpoint of excellent absorbability of ultraviolet light of m or less and good liquid crystal display properties, those having little absorption of visible light having a wavelength of 400 nm or more are preferably used. In the present invention, the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less, and still more preferably 1% or less.
% Or less.

In the present invention, for example, a blue dye or the like may be used as an additive to adjust the color of the film. Preferred dyes include anthraquinone dyes. The anthraquinone-based dye can have any substituent at positions 1 to 8 of the anthraquinone. Preferred substituents include an optionally substituted anilino group, a hydroxyl group, an amino group, a nitro group, and a hydrogen atom. The amount of these dyes added to the film is 0.1 to 100 to maintain the transparency of the film.
0 μg / m ² , preferably 10 to 100 μg / m ² .

It is preferable to add fine particles as a matting agent to the cellulose ester film of the present invention in order to impart lubricity to the film. It is preferable that these fine particles are surface-treated with an organic substance because the haze of the film can be reduced.

Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like.

The larger the average diameter of the fine particles, the greater the matting effect, and the smaller the average diameter, the better the transparency. Therefore, in the present invention, the average diameter of the primary particles of the fine particles is preferably from 5 to 50 nm, more preferably. , 7 to 20 nm.

The fine particles are not particularly limited. For example, AEROSIL 200 manufactured by Nippon Aerosil Co., Ltd.
200V, 300, R972, R972V, R974,
R202, R812, OX50, TT600, etc., preferably AEROSIL200V, R972V
And the like.

These fine particles usually have an average particle size of 0.01
These particles form secondary particles of about 1.0 to 1.0 μm, and these fine particles are present in the film as agglomerates of the primary particles and form irregularities of 0.01 to 1.0 μm on the film surface. The content of these fine particles is preferably 0.005 to 0.3% by mass based on the cellulose ester.

In particular, the cellulose ester film of the present invention preferably contains silicon dioxide fine particles, and is 8.5.
By casting and casting a cellulose ester film using a cellulose ester solution containing an ultraviolet absorber having the above distribution coefficient and silicon dioxide fine particles, foreign matter failure due to aggregation of the fine particles in the cellulose ester solution is significantly reduced. This is particularly preferred because

For obtaining the cellulose ester film of the present invention, as a method for preparing a dispersion of fine particles, there are, for example, the following three types.

<< Preparation Method A >> After stirring and mixing the solvent and the fine particles, the mixture is dispersed with a disperser. This is used as a fine particle dispersion. The fine particle dispersion is added to the dope and stirred.

<< Preparation Method B >> After stirring and mixing the solvent and the fine particles, the mixture is dispersed with a disperser. This is used as a fine particle dispersion. A small amount of cellulose ester is added to another solvent and dissolved by stirring. The fine particle dispersion is added thereto and stirred.
This is used as a fine particle addition liquid. The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

<< Preparation Method C >> A small amount of cellulose ester is added to a solvent and dissolved by stirring. Fine particles are added thereto and dispersed by a disperser. This is used as a fine particle addition liquid. The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

The preparation method A is excellent in dispersibility of the silicon dioxide fine particles, and the preparation method C is excellent in that the silicon dioxide fine particles hardly re-aggregate. Above all, the above-mentioned preparation method B is a preferable preparation method which is excellent in both the dispersibility of the silicon dioxide fine particles and the difficulty of re-aggregation of the silicon dioxide fine particles.

<< Dispersion Method >> When silicon dioxide fine particles are mixed with a solvent and dispersed, the concentration of silicon dioxide is 5 to 30.
% By mass is preferable, and 10 to 25% by mass is more preferable.
15-20% by mass is most preferred. The higher the dispersion concentration, the lower the liquid turbidity with respect to the amount added, which is preferable because haze and aggregates are improved.

The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol,
Examples thereof include propyl alcohol, isopropyl alcohol, and butyl alcohol. The solvent other than the lower alcohol is not particularly limited, but it is preferable to use a solvent used in forming a cellulose ester film.

Using the dope thus obtained, a cellulose ester film can be obtained through a casting process described below.

<< Casting Step >> The dope is fed to a pressurizing die through a pressurized metering gear pump, and at a casting position, an endless metal belt or a rotating metal drum casting support (hereinafter, referred to as an infinity). It may simply be a support)
In this step, a dope is cast from a pressure die. The surface of the casting support is a mirror surface.

Other casting methods include a doctor blade method in which the thickness of the cast dope film is adjusted with a blade, and a reverse roll coater method in which the dope film is adjusted with a counter-rotating roll. A pressure die that can adjust the shape and easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the doping amount may be divided to form a plurality of layers. Alternatively, the inside of the die is divided by slits, and a plurality of dope solutions having different compositions are simultaneously cast (also called co-casting).
Thus, a cellulose ester film having a laminated structure can be obtained.

The dope thus obtained is cast on a support such as a belt or a drum to form a film. In the present invention, a solution casting method using a belt is particularly effective. This is because it is easy to finely adjust the drying conditions on the support as described later.

<< Solvent Evaporation Step >> A web (in the present invention, a dope is cast on a casting support and the formed dope film is called a web) is heated on the casting support to remove the solvent. This is the step of evaporating. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat with liquid from the back surface of the support, a method of transferring heat from the front and back by radiant heat, and the like. Preferred for drying efficiency. A method of combining them is also preferable. The web on the support after casting is preferably dried on the support in an atmosphere at 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat the web by means such as infrared rays.

In particular, the cellulose ester film of the present invention desirably releases the web from the support within 30 to 90 seconds after casting. Peeling in less than 30 seconds not only deteriorates the surface quality of the film, but is also not preferable in terms of moisture permeability. Drying for more than 90 seconds is not preferable because surface quality is deteriorated due to deterioration of the releasability and strong curl is generated in the film.

<< Peeling Step >> In this step, the web from which the solvent has evaporated on the support is peeled from the support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, the web is difficult to peel, or conversely, if the web is sufficiently dried on the support and then peeled, a part of the web is peeled off in the middle.

The temperature at the peeling position on the support is preferably 10 to 40 ° C., more preferably 11 to 30 ° C.
° C. The residual solvent amount of the web at the peeling position is 2
It is preferably from 5 to 120% by mass, more preferably from 40 to 1% by mass.
00% by mass.

The residual solvent amount of the web according to the present invention is defined by the following equation. Residual solvent amount = (mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web) × 100% The heat treatment for measuring the amount of residual solvent is 115 ° C.
Represents that heat treatment is performed for one hour.

In order to adjust the amount of the residual solvent at the time of peeling as described above, the surface temperature of the casting support after casting is controlled so that the organic solvent can be efficiently evaporated from the web. It is preferable to set the temperature at the peeling position on the casting support within the above-mentioned temperature range. In order to control the temperature of the support, a heat transfer method having good heat transfer efficiency is preferably used. For example, a back surface heat transfer method using a liquid is preferable.

The heat transfer method using radiant heat, hot air or the like is difficult to control the temperature of the support, and is not a preferable method. However, in a belt (support) machine, it is necessary to control the temperature at the position where the belt to be transferred comes below. Can adjust the belt temperature with gentle wind.

The temperature of the support can be partially changed by dividing the heating means, and is set to a different temperature such as a casting position, a drying section, and a peeling position of the casting support. Can be done.

As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled while the amount of the residual solvent is as large as possible), there is a gel casting method in which the film can be peeled even when the amount of the residual solvent is large. .

There are a method in which a poor solvent for the cellulose ester is added to the dope, gelling is performed after casting the dope, and a method in which gelling is performed by lowering the temperature of the support.
There is also a method of adding a metal salt to the dope.

By gelling the film on the support to strengthen the film, peeling can be accelerated and the film forming speed can be increased.

In the case where the web is peeled off at a point where the residual solvent amount is larger, if the web is too soft, the flatness at the time of peeling may be impaired, or a shear or a vertical stripe may easily occur due to the peeling tension. The amount of solvent can be determined.
The peeling tension when peeling the support and the film is usually 19
Peeling is performed at 6 to 245 N / m. When wrinkles are likely to occur at the time of peeling, it is preferable to peel at 190 N / m or less, and further, the minimum tension at which peeling can be performed is 166.6 N / m.
m, then peeling at a minimum tension of ２137.2 N / m, particularly preferably at a minimum tension of １００100 N
/ M. It is preferable that the peeling tension is lower because the in-plane retardation Ro can be kept lower. The in-plane retardation Ro is preferably less than 20 nm, more preferably less than 10 nm and then preferably less than 5 nm, most preferably 0 to 1 nm.

In the present invention, the in-plane retardation R
o was measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at a wavelength of 590 nm.
The three-dimensional refractive index is measured, and the obtained refractive indices Nx, Ny,
It can be calculated from Nz. Further, a retardation value Rt in the film thickness direction of 0 to 300 nm is obtained, more preferably 0 to 150 nm, more preferably 0 to 70 nm.
nm is preferably obtained according to the application.

Ro = (Nx−Ny) × d Rt = ((Nx−Ny) / 2−Nz) × d The cellulose ester film of the present invention has an angle θ (radian) between the slow axis direction and the film forming direction. ) And in-plane retardation Ro have the following relationship, and are particularly preferably used as optical films such as protective films for polarizing plates.

P ≦ 1−sin ² (2θ) sin ² (πRo / λ) P = 0.9999 Nx is the refractive index in the slow axis direction in the film plane, and Ny is the refraction in the fast axis direction in the film plane. Is the refractive index in the thickness direction of the film, and d is the film thickness (nm) of the film. θ is the angle (° radian) formed between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the above-mentioned Nx, Ny, Nz, θ in the three-dimensional refractive index measurement for determining θ. The wavelength of light is 590 nm, and π is the circular constant.

<< Drying Step >> While maintaining the width by using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web while holding both ends of the web with clips or pins, This is the step of drying the web. It is preferable to maintain the transport tension in the drying step as low as possible because Ro can be kept low.
It is preferably 90 N / m or less. 170N /
m, more preferably 140 N
/ M or less, and particularly preferably from 100 to 130 N / m. In particular, it is effective to maintain the transport tension at or below the above-mentioned value until the amount of the residual solvent in the film becomes at least 5% by mass or less.

The drying means generally blows hot air on both sides of the web, but there is also a means of heating by applying microwaves instead of the wind. Too fast drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably carried out from a residual solvent content of about 8% by mass or less. Throughout, the drying temperature is generally between 40 and 250 ° C. In particular, drying at 40 to 160 ° C is preferable.

In the drying step after peeling off from the surface of the casting support, the web tends to shrink in the width direction due to evaporation of the solvent. The quicker it dries at higher temperatures, the greater the shrinkage.

It is preferable to dry the film while suppressing the shrinkage as much as possible in order to improve the flatness of the finished film.

From this viewpoint, for example, Japanese Patent Application Laid-Open No. Sho 62-46
No. 625, a method of drying the whole or a part of the web in the width direction while holding both ends of the width of the web with a clip or a pin (called a tenter method), in particular, a tenter using a clip A pin tenter method using a pin is preferably used.

At this time, the stretching ratio in the width direction is 0% to 10%.
It is preferably 0%, more preferably 5% to 20%, and more preferably 8% to 15% when used as a polarizing plate protective film.
% Is most preferable, and when used as a retardation film, 10% to 40% is more preferable, and 20% to 30% is most preferable. Ro can be controlled by the stretching ratio, and a higher stretching ratio is preferable because the resulting film has excellent flatness.

When the tenter is carried out, the residual solvent content of the web is preferably 20 to 100% by mass at the start of the tenter, and drying is performed while applying a tenter until the residual solvent content of the web becomes 10% by mass or less. It is preferably performed, more preferably 5% by mass or less.

The drying temperature when performing a tenter is 30 to
150 ° C is preferred, 50 to 120 ° C is more preferred,
70-100 ° C is most preferred. The lower the drying temperature, the less the evaporation of the ultraviolet absorber and the plasticizer, and the better the process contamination, and the higher the drying temperature, the better the flatness of the film. Even when the drying temperature is high, the ultraviolet absorbent of the present invention hardly evaporates, so that the effect is remarkably exerted under the manufacturing conditions in which the tenter drying temperature is high and the stretching ratio is high.

In the film drying step, the film peeled from the support is further dried to reduce the residual solvent content to 0.5% by mass or less, more preferably 0.1% by mass or less. , Most preferably from 0 to 0.0
It is to be 1% by mass or less.

In the film drying step, a roll hanging method or a method of drying while transporting the film by the above-mentioned pin tenter method is generally employed. The means for drying the film is not particularly limited, and is generally performed using hot air, infrared rays, a heating roll, a microwave, or the like. It is preferable to use hot air in terms of simplicity. Drying temperature is 3-5 in the range of 40-150 ° C.
It is preferable to raise the temperature gradually in each step, and it is more preferable to increase the temperature in the range of 80 to 140 ° C. in order to improve dimensional stability.

In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, but may be an atmosphere of an inert gas such as nitrogen gas, carbon dioxide gas, or argon. May go.

However, it is needless to say that the danger of the explosion limit of the evaporated solvent in the dry atmosphere must always be considered.

<< Winding Step >> This is a step of winding as a cellulose ester film after the amount of residual solvent in the web becomes 2% by mass or less.
A film having good dimensional stability can be obtained by the following.

As the winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like, and these may be used properly. .

To adjust the film thickness, the dope concentration, the amount of liquid fed by the pump, the slit gap of the die cap, the extrusion pressure of the die, the speed of the casting support, etc. are controlled so as to obtain the desired thickness. Good to do.

Further, as means for making the film thickness uniform, it is preferable that the programmed feedback information is fed back to each of the above-described devices using a film thickness detecting means for adjustment.

The thickness of the cellulose ester film varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, and more preferably 10 to 250 μm, as a finished film.
Is particularly preferable as a film for a liquid crystal image display device. The cellulose ester film of the present invention is particularly excellent in moisture permeability and dimensional stability, although it is a thin film having a thickness of 10 to 60 μm.

The moisture permeability in the present invention is defined by JIS Z
It is defined by the value measured by the method described in “0208”. Moisture permeability is preferably 20~250g / m ² · 24 hours, but is preferably in particular 20~200g / m ² · 24 hours. When the moisture permeability exceeds 250 g / m ² · 24 hours, the durability of the polarizing plate is significantly reduced.
If the time is less than 0 g / m ² · 24 hours, the solvent such as water used for the adhesive during the production of the polarizing plate is difficult to dry, and the drying time is undesirably long. More preferably 25 to
200 g / m ² · 24 hours.

In the cellulose ester film of the present invention, the dimensional stability can be further improved by reducing the mass change at 80 ° C. and 90% RH.

In the cellulose ester film of the present invention, the rate of change in mass before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is more preferably within ± 2%, whereby a thin film having improved moisture permeability is obtained. Although it is a film, a cellulose ester film having an excellent dimensional change rate can be obtained.

The cellulose ester film of the present invention comprises
The dimensional change after heat treatment for 48 hours at 80 ° C. and 90% RH atmosphere is MD direction (film forming direction), TD
Both directions (width direction of the film) are preferably within ± 0.5%, more preferably within ± 0.3%, further preferably within ± 0.1%, and further preferably ± 0%. It is preferably within 0.05%.

The dimensional change rate in the present invention is a characteristic value representing a dimensional change in the longitudinal and lateral directions of the film under severe conditions of temperature and humidity. Specifically, the film is placed under heating conditions, humidification conditions, and heat-humidity conditions as forced deterioration.
Measure vertical and horizontal dimensional changes. For example, a film sample to be measured is cut into a size of 150 mm in the width direction × 120 mm in the length direction, and two portions are formed on the film surface at 100 mm intervals in the width direction and the length direction, respectively.
Mark the cross with a sharp knife, such as a razor. The film is humidified in an environment of 23 ° C. and 55% RH for 24 hours or more, and the distance L1 between the marks in the width direction and the longitudinal direction before the treatment is measured with an optical microscope. Next, the sample is subjected to a high temperature and high humidity treatment (conditions: 80 ° C., 90% RH) in an electric thermostat.
In the environment for 48 hours). Again, the sample is conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and the distance L2 between the marks in the width direction and the length direction after the treatment is measured with an optical microscope. The rate of change before and after this processing is determined by the following equation.

Dimensional change rate (%) = (L2−L1) / L1 × 100 In the formula, L1 represents a distance between marks before processing, and L2 represents a distance between marks after processing.

That is, a desired dimensional change can be measured by setting the positions of the marks to be applied in the longitudinal direction and the width direction of the film.

The dimensional change after treatment at 105 ° C. for 5 hours is preferably within ± 0.5%, more preferably within ± 0.3%, and more preferably ± 0.3%, in both the MD and TD directions. It is preferably within 0.1%.
Preferably it is within 0.05%.

The cellulose ester film of the present invention has a tensile strength of 90 to 170 N / mm ² in both the MD and TD directions.
And particularly preferably 120 to 160 N / mm ²
It is preferable that

The water content is preferably from 0.1 to 5%,
0.3 to 4% is more preferable, and 0.5 to 2% is further preferable.

The cellulose ester film of the present invention comprises
The transmittance is desirably 90% or more, more preferably 92% or more, and particularly preferably 93% or more. Further, the haze is preferably 0.5% or less,
In particular, it is preferably 0.1% or less, more preferably 0%.

In the cellulose ester film of the present invention, it is preferable that the curl value has a small absolute value, and the deformation direction may be either the + direction or the-direction. The absolute value of the curl value is preferably 30 or less, more preferably 2
0 or less, and particularly preferably 10 or less.
The curl value is represented by a radius of curvature (1 / m).

The method for producing the cellulose ester film of the present invention by the solution casting method will be described below in more detail with reference to the drawings.

FIG. 1 is a schematic view showing a preferred example of a solution casting method for forming a film. FIG. 1A is a schematic diagram of a case where the film is dried in a roll conveying / drying step after casting. FIG.
(B) is a schematic diagram in a case where after casting, drying is performed in a roll transport / drying step, and then drying is performed in a tenter transport / drying step. FIG. 1 (c) is a schematic view showing a case where, after casting, drying is performed in a tenter conveying / drying step, and then drying is performed in a roll conveying / drying step. FIG. 1D is a schematic view showing a case where after casting, drying is performed in a roll transport and drying process, then drying is performed in a tenter transport and drying process, and then drying is performed in a roll transport and drying process.

In the present invention, the steps including the tenter transport / drying step and the roll transport / drying step include the step of drying the film separated from the support and drying the film. It refers to a process having a tenter transport / drying process and a roll transport / drying process for adjusting the expansion / contraction ratio. The tenter transport / drying step refers to a step in which drying is performed simultaneously while being transported by the tenter transport apparatus, and the drying expansion / contraction ratio is adjusted. It refers to the step of adjusting the rate.

In FIG. 1, reference numeral 1 denotes a support that runs endlessly. A mirror-like metal strip is used as the support. Reference numeral 2 denotes a die for casting a dope obtained by dissolving a cellulose ester resin in a solvent on a support 1. Reference numeral 3 denotes a peeling point at which the film on which the dope cast on the support 1 is solidified is peeled off, and reference numeral 4 denotes a peeled-off film. Reference numeral 5 denotes a tenter conveying / drying process, and 51 denotes an exhaust port.
Reference numeral 2 denotes a drying air intake. Note that the exhaust port 51 and the dry air intake port 52 may be reversed. Reference numeral 6 denotes a tension cutting means. Examples of the tension cutting means include a nip roll and a suction roll. Incidentally, the tension cutting means may be provided between each step.

Reference numeral 8 denotes a roll transport / drying step, 81 denotes a drying box, 82 denotes an exhaust port, and 83 denotes a drying air intake. In addition, the exhaust port 82 and the dry air intake 83
May be reversed. Reference numeral 84 denotes an upper transport roll,
Reference numeral 85 denotes a lower transport roll. The transport roll 84,
Reference numeral 85 denotes one set of upper and lower parts, and is composed of a plurality of sets. Reference numeral 7 denotes a rolled-up film.

In the step shown in FIG. 1D, the roll transport / drying step before the tenter transport / drying step 5 is called a first roll transport / drying step, and the roll transport after the tenter transport / drying step 5 is performed. -The drying step is referred to as a second roll transport / drying step. Note that a cooling step not shown in FIGS. 1A to 1D may be provided as necessary before winding.

In the present invention, a cellulose ester film may be produced by any of the above-mentioned solution casting methods.

The cellulose ester film of the present invention comprises
From the viewpoint of good moisture permeability and dimensional stability, it is preferably used for a liquid crystal display member, more specifically, a protective film for a polarizing plate.
In particular, the cellulose ester film of the present invention is preferably used in a protective film for a polarizing plate which has strict requirements for both moisture permeability and dimensional stability.

The polarizing plate according to the present invention can be manufactured by a general method. For example, a method in which an optical film or a cellulose ester film is subjected to an alkali saponification treatment, and a polyvinyl alcohol film is immersed in an iodine solution and bonded to both surfaces of a polarizing film produced by stretching using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment in which the cellulose ester film is immersed in a high-temperature strong alkaline solution in order to improve the wetting of the aqueous adhesive and improve the adhesiveness.

The cellulose ester film of the present invention has a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optically anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer,
Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, and atmospheric pressure plasma treatment.

The polarizing plate thus obtained is provided on one or both sides of a liquid crystal cell, and the display device of the present invention is obtained using the polarizing plate.

By using the protective film for a polarizing plate composed of the cellulose ester film of the present invention, it is possible to provide a polarizing plate which is thinner and has excellent durability, dimensional stability and optical isotropy. Further, the liquid crystal display device using the polarizing plate or the retardation film of the present invention can maintain stable display performance for a long period.

The cellulose ester film of the present invention can also be used as a substrate for an antireflection film or an optical compensation film.

[0129]

EXAMPLES Synthesis Example 1 70 ml of methyl ethyl ketone, 30 m of methyl cellosolve
1,2- (2 ', 4'-dihydroxyphenyl) -5
52.3 g of chloro-benzotriazole, cetyl bromide 7
3.3 g, 13.8 g of sodium carbonate, 1.0 g of potassium iodide, and 2.0 g of dimethylformamide were charged.
The temperature was raised to 92 ° C. over time, and the reaction was performed for 3 hours. Further, the temperature was slowly raised by collecting the solvent, and the temperature was raised to 130 ° C. after 7 hours. After cooling, toluene 400 ml, water 1
00 ml was added and the pH was adjusted to 4 with dilute sulfuric acid. After liquid separation, the toluene layer was washed with water, and 400 ml of isopropyl alcohol and 50 ml of toluene were added to the residue obtained by distilling off toluene.
After recrystallization, 2- (2'-hydroxy-4'-hexadecyloxyphenyl) -5-chloro-benzotriazole represented by Compound UV-2 was obtained in a yield of 69.4 g.

Synthesis Example 2 A glass reactor was charged with 21 parts of benzyl, 12.2 parts of salicylaldehyde, 77.1 parts of ammonium acetate and 600 parts of glacial acetic acid, and reacted under reflux for 4 hours. After throwing into ice water, it was made alkaline with aqueous ammonia to precipitate crystals. Then, the crystals were collected by filtration, washed with water, and dried to obtain white crystals. The obtained crystals were compound UV-8.
2- (2'-hydroxyphenyl) -4,5-diphenylimidazole.

Example 1 <Preparation of Samples 1 to 6> (Silicon Oxide Dispersion) Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) (Average diameter of primary particles: 12 nm, apparent specific gravity: 100 g / liter) 10 parts by mass Ethanol 90 parts by mass After stirring and mixing the above with a dissolver for 30 minutes, the mixture was dispersed with Menton-Gaulin. The liquid turbidity after dispersion is 93 pp
m.

(Preparation of Additive Solution A) Cellulose triacetate synthesized from linter cotton 4 parts by mass Methylene chloride 100 parts by mass The above was charged into a closed vessel, heated, stirred, completely dissolved, and filtered.

To this, 12 parts by mass of the silicon oxide dispersion was added with stirring, and the mixture was further stirred for 30 minutes. Then, the filtration accuracy was sequentially increased with a polypropylene wind cartridge filter TCW-PPS (10N, 20N) manufactured by Advantech Toyo Co., Ltd. And used to prepare an additive solution A.

(Preparation of dope solution A) Cellulose triacetate synthesized from linter cotton 85 parts by mass Cellulose triacetate synthesized from wood pulp 15 parts by mass Triphenyl phosphate 11.5 parts by mass UV absorber described in Table 1 2 parts by mass Part 475 parts by weight of methylene chloride 50 parts by weight of ethanol The above was put into a closed container, heated and completely dissolved while stirring, and Azumi Filter Paper No. Filtration was performed using 244 to prepare a dope solution A.

In the film forming line, Finemet NF manufactured by Nippon Seisen Co., Ltd. (absolute filtration accuracy: 50 μm, 15 μm, 5 μm)
The dope solution A was filtered in the order of m with increasing filtration accuracy. In the in-line addition line, Nippon Seisen Co., Ltd. Finemet NF (absolute filtration accuracy 50 μm, 15 μm
m, and 5 μm in this order with increasing filtration accuracy). 2.2 parts by mass of the filtered additive solution A was added to 100 parts by mass of the filtered dope solution A, and an in-line mixer (Toray static tube mixer Hi-Mixe) was added.
r, SWJ), and then uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm using a belt casting apparatus. With stainless steel band support,
The solvent was evaporated until the residual solvent amount became 80%, and the solvent was peeled off from the stainless steel band support at a peel tension of 127 Newton (13 kgf) / m. The peeled cellulose triacetate film was slit to a width of 1550 mm, and then stretched 10% in the width direction by a tenter.
At a drying temperature of 120 ° C., 135 ° C.
Was dried while being conveyed by a number of rolls through a drying zone, slit to a width of 1330 mm, and knurling was performed on both ends of the film with a width of 10 mm and a height of 5 μm to obtain cellulose triacetate film samples 1 to 6. At this time, the thickness of the cellulose triacetate film was 4
0 μm and the winding length was 2000 m.

The prepared sample was evaluated according to the following measuring method. << Measurement Method >> Roll Stain After preparing a 10,000 m cellulose ester film, the degree of soiling of the first roll in contact with the film peeled from the stainless steel band support was visually observed and evaluated according to the following ranks.

A: The roll is dirty at all. B: The roll is partially soiled. C: The roll is completely soiled. A and B continue production. Level. C is the level at which production is suspended and rolls are cleaned.

At the place where the 10,000 m cellulose ester film was produced, the film was sampled, and the obtained film was 1 m thick.
^2. The number of push failures having a size of 30 μm or more existing on ² was counted and obtained.

Flatness The fluorescent lamp tube lit on the surface of the film sample was reflected and projected, and its distortion or fine disturbance was observed. The flatness was classified into the following levels.

A: Fluorescent lamp looks straight B: Fluorescent lamp looks partially bent C: Fluorescent lamp appears mottled Lightfastness Following the alkali saponification treatment described below, described below First, the parallel transmittance and the orthogonal transmittance of the polarizing plate produced by the above method were measured, and the degree of polarization was calculated according to the following equation. Thereafter, each polarizing plate was forcibly deteriorated for 200 hours without a UV cut filter for 200 hours under a sunshine weather meter, and then the parallel transmittance and the orthogonal transmittance were measured again, and the degree of polarization was calculated according to the following equation. The degree of polarization change was determined by the following equation.

The degree of polarization P = ((H ₀ −H ₉₀ ) / (H ₀ +
H ₉₀ )) ^1/2 × 100 Rate of change in degree of polarization = P ₀ −P ₅₀₀ H ₀ : Parallel transmittance H ₉₀ : Direct transmittance P ₀ : Degree of polarization before forced degradation P ₅₀₀ : Polarization 500 hours after forced degradation Degree A: Change rate of polarization degree is less than 10% O: Change rate of polarization degree is 10% or more and less than 25% X: Change rate of polarization degree is 25% or more.

Alkaline saponification treatment Saponification step 2 mol / l NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Neutralization step 10% by mass HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Saponification, water washing, neutralization, and water washing were performed in this order, and then drying was performed at 80 ° C.

(Preparation of Polarizing Plate) A polyvinyl alcohol film having a thickness of 120 μm was coated with 1 kg of iodine and 4 kg of boric acid.
Was immersed in 100 kg of an aqueous solution containing, and stretched 6 times at 50 ° C. to form a polarizing film. Cellulose ester film samples which had been subjected to an alkali saponification treatment on both sides of the polarizing film were bonded to each other using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive to prepare a polarizing plate.

[0144]

[Table 1]

[0145]

Embedded image

Example 2 <Preparation of Samples 101 to 113> (Preparation of Additive Solution B) Cellulose acetate propionate having a degree of acetyl substitution of 1.95, a degree of propionyl substitution of 0.7, and a number average molecular weight of 75,000 4 parts by mass methyl acetate 100 parts by mass or more were put into a closed container, heated, stirred, completely dissolved, and filtered.

To this, 12 parts by mass of the silicon oxide dispersion was added with stirring, and after stirring for another 30 minutes, the filtration accuracy was increased sequentially with a polypropylene wind cartridge filter TCW-PPS (10N, 20N) manufactured by Advantech Toyo Co., Ltd. ) To prepare an additive liquid B.

(Preparation of Dope Liquid B) Cellulose acetate propionate having a degree of acetyl substitution of 1.95, a degree of propionyl substitution of 0.7, and a number average molecular weight of 75,000 100 parts by mass Triphenyl phosphate 11.5 parts by mass Table 2 2 parts by mass of ultraviolet absorber 300 parts by mass of methyl acetate 80 parts by mass of ethanol The above components are put into a closed container, and are completely dissolved with heating and stirring, and Azumi Filter Paper No. Filtration was performed using 244 to prepare a dope solution B.

Finemet NF (absolute filtration accuracy 50 μm, 15 μm, 5 μm) manufactured by Nippon Seisen Co., Ltd.
The dope liquid B was filtered in the order of m with increasing filtration accuracy. In the in-line addition line, Nippon Seisen Co., Ltd. Finemet NF (absolute filtration accuracy 50 μm, 15 μm
m, and 5 μm in this order with increasing filtration accuracy). 2.2 parts by mass of the filtered additive B was added to 100 parts by mass of the filtered dope B, and an in-line mixer (Toray static tube mixer Hi-Mixe) was added.
r, SWJ), and then uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm using a belt casting apparatus. With stainless steel band support,
The solvent was evaporated until the residual solvent amount became 80%, and the solvent was peeled off from the stainless steel band support at a peel tension of 127 Newton (13 kgf) / m. The peeled cellulose triacetate film was slit to a width of 1550 mm, and then stretched by 25% in the width direction with a tenter.
At a drying temperature of 120 ° C., 135 ° C.
Was dried while being conveyed by a number of rolls through a drying zone, slit to a width of 1330 mm, and knurling was performed on both ends of the film with a width of 10 mm and a height of 5 μm to obtain cellulose triacetate film samples 101 to 113. At this time, the thickness of the cellulose triacetate film was 40 μm, and the winding length was 2000 m.

The prepared sample was evaluated according to Example 1 and the following measurement method. << Measurement Method >> Evaporation of Ultraviolet Absorber 30 g of a film sample was finely cut, 100 g of methyl ethyl ketone was added, and ultrasonic irradiation was performed to extract the ultraviolet absorber. After filtration, the solvent is evaporated to dryness, an internal standard sample is added, and a gas chromatograph mass spectrometry system (GC
/ MS) to determine the amount of the ultraviolet absorber. With respect to the prescription value obtained from the calculation, it was calculated how much the quantitative value of the film sample was reduced, and ranking was performed as follows. The smaller the difference from the prescribed value, the less the transpiration of the ultraviolet absorber, and the better.

A Reduction amount less than 1% B Reduction amount 1% or more and less than 3% C Reduction amount 3% or more

[0152]

[Table 2]

[0153]

Embedded image

Example 3 A commercially available liquid crystal display panel (NEC color liquid crystal display MultiSync LCD1525J)
LA-1529HM) was carefully peeled off. After the samples prepared in Examples 1 and 2 were subjected to the alkali saponification treatment described in Example 1, a polarizing plate was prepared by the method described in Example 1, and the polarization direction was adjusted to obtain a liquid crystal display panel. I stuck it. For each liquid crystal display panel, as a result of visually evaluating the contrast, the liquid crystal display panel using the polarizing plate of the present invention has no foreign matter on the surface compared to the liquid crystal display panel using the polarizing plate of the comparative example, and the screen is easy to see. It was confirmed that high contrast was maintained over a long period of time.

[0155]

According to the present invention, a cellulose ester film having excellent surface properties, no process contamination, and excellent productivity is provided.
An optical film and a method for producing the same can be provided,
Furthermore, a polarizing plate and a display device could be provided using this optical film.

[Brief description of the drawings]

FIG. 1 is a schematic view of a solution casting method for forming a film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mirror surface belt-shaped metal casting support 2 Dice 4 Cellulose ester film 5 Tenter conveyance and drying process 6 Tension cutting means 8 Roll conveyance and drying process 84 Upper conveyance roll 85 Lower conveyance roll

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G02B 1/11 G02B 5/22 4F205 5/22 5/30 4F210 5/30 G02F 1/1335 4J002 G02F 1/1335 B29K 1 : 00 // B29K 1:00 B29L 7:00 B29L 7:00 11:00 11:00 G02B 1/10 A F term (reference) 2H048 CA01 CA04 CA09 CA13 CA19 CA27 CA29 2H049 BA02 BA06 BB13 BB33 BB49 BC09 BC22 2H091 FA08X FA08Z FA11X FA11Z FA37X FA37Z FB02 FC07 LA16 LA17 2K009 AA02 CC38 4F071 AA09 AC11 AC19 AE05 AF03 AF05 AF29 AF30 AH12 AH16 BB02 BC01 4F205 AA01 AB14 AC05 AG01 AH73 GA07 GB02 GC07 GE24 GF02 AGW014 EU106 EU116 EU166 EU176 FD056 GP00 GS00

Claims (8)

[Claims] 1. Methylene chloride: ethanol = 5
A cellulose ester film having a solubility of 0:50 (% by mass) at 20 ° C. in a solvent of 10 g / 100 ml or more and containing an ultraviolet absorber which is solid under an atmosphere of 20 ° C. 2. The 10 mass% disappearance temperature of thermal mass spectrometry is 2
A cellulose ester film containing an ultraviolet absorber at 30 to 450 ° C. 3. A method for producing an optical film by a solution casting method, wherein the resin solution containing the ultraviolet absorbent according to claim 1 is cast on a support and dried on the support. Thereafter, it is peeled off and stretched in the width direction by 0 to 100% with a tenter. 4. The method for producing an optical film according to claim 3, wherein the resin solution containing the ultraviolet absorbent contains methyl acetate. 5. An optical film produced by the method according to claim 3. Description: 6. The optical film according to claim 5, wherein the resin of the resin solution containing the ultraviolet absorbent is a cellulose ester. 7. A polarizing plate comprising the optical film according to claim 5. 8. A display device using the optical film according to claim 5 or 6.