JP2001163994A - Resin film and its manufacturing method and polarizing plate having its resin film as protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin film which has improved a problem of destruction of an antistatic layer to be provided on a resin film to be used as the protective film for a polarizing plate, a problem of increase in curling due to the influence of a coating solvent on the substrate and a problem of deposition of an additive in the production process to contaminate the process or on the films and the like and has no blocking tendency to the back surface of the film, sufficient adhesion to a polarizer, and high productivity, and its manufacturing method. SOLUTION: The resin film has a concentration of an antistatic agent at least one surface side which differs from the average concentration of the antistatic agent of the entire resin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin film which has an antistatic function, is thin, has high productivity, and can be used as an optical film, particularly a polarizing plate protective film, and a method for producing the same. The present invention relates to a polarizing plate used as a protective film.

[0002]

2. Description of the Related Art In recent years, thinner and lighter notebook computers and displays have been developed. Along with this, there is an increasing demand for thinner films, higher performance, and higher functions in optical films such as display films, retardation films, and polarizing plate protective films for liquid crystals having an antireflection function and the like. A triacetyl cellulose film is widely used as a part of a display film or a polarizing plate protective film, but a polarizing plate protective film having an antistatic property has been strongly demanded.

As a triacetyl cellulose film having an antistatic function, for example, as described in JP-A-6-123806, an antistatic layer containing a metal oxide or an ionic polymer is coated and formed on a film. A method for providing an antistatic function is known. However, when a resin film having an antistatic layer formed by a coating method is used as a protective film for a polarizing plate, the antistatic layer is destroyed in an alkali saponification process because the antistatic layer is applied as a thin film, and the antistatic performance is reduced. Has a problem of deterioration. In addition, there has been a problem that curling becomes large due to the influence of the coating solvent on the base material, and that the antistatic layer causes blocking on the back surface and lowers productivity. In addition, when forming the antistatic layer by coating, dust and foreign matter are mixed into the coating, causing a coating failure to lower the yield. In particular, with the increase in the screen size of the display device, further improvement in quality is required. In addition, when another layer is applied on the antistatic layer, the wettability is poor, and when used as a protective film for a polarizing plate, there is a defect that the adhesion to a polarizer is insufficient.

Another problem with these resin films is that a plasticizer or an ultraviolet absorber added to the resin film precipitates during the production of the resin film and contaminates the process. As a problem of the film to be manufactured by casting, there is a problem that the appearance of the film is deteriorated due to poor peelability of the resin film from the casting support. .

[0005] As a method of producing a film by casting,
JP-B-63-62269, JP-A-61-94725
And JP-A-61-148013 disclose a method for producing a resin film by casting solutions having different viscosities and solvent compositions. However, as in the present invention,
For example, it has not been known to produce a resin film having an antistatic function in which the antistatic agent has a distribution in the film thickness direction by co-casting using a solution having a different concentration of the antistatic agent.

[0006]

By imparting an antistatic function to the resin film itself, the antistatic layer is destroyed in the alkali saponification step when the resin film is used as a protective film for the polarizing plate, and the base material of the coating solvent is used. The problem that the curl becomes large due to the influence on the back side of the film, such as the problem that the plasticizer and the UV absorber are deposited during the production and contaminate the process or deposit on the film, etc. The present invention relates to a resin film having no blocking and sufficient adhesiveness to a polarizer, high productivity, and a method for producing the same.

[0007]

The present invention is achieved by the following means.

[0008] 1. A resin film, wherein the concentration of the antistatic agent on at least one surface side is different from the average concentration of the antistatic agent in the entire resin film.

[0009] 2. In a resin film in which the concentration of the antistatic agent on at least one surface side is different from the average concentration of the antistatic agent in the entire resin film, foreign matters having a size of 5 to 50 μm recognized in the polarization crossed Nicols state have an area of 250 m.
It is less than 200 particles per m ² , and the size of the foreign substance having a size of more than 50 μm recognized in the polarization cross Nicol state exceeds 25 μm.
A resin film characterized in that the number is substantially zero per 0 mm ² .

[0010] 3. 3. The resin film as described in 1 or 2, wherein the retardation value is 100 nm or less.

4. 4. The resin film according to the above 1, 2 or 3, further comprising a plasticizer.

5. 5. The resin film as described in 1, 2, 3, or 4, wherein the resin film contains fine particles.

6. A resin film, wherein the concentration of the antistatic agent on at least one surface side is higher than the average concentration of the antistatic agent in the entire resin film.

7. The concentration of the antistatic agent on both surfaces is
A resin film having a higher antistatic agent concentration than the average concentration of the entire resin film.

[8] The concentration of the antistatic agent on one surface side is higher than the average concentration of the antistatic agent on the entire resin film, and the concentration of fine particles on the opposite surface side is higher than the average concentration of the fine particles on the entire resin film. Resin film.

9. The concentration of the antistatic agent on one surface side is
A resin film, wherein the average concentration of the antistatic agent is higher than that of the entire film, and the concentration of the plasticizer on both surface sides is lower than the average concentration of the plasticizer in the entire resin film.

10. The concentration of the antistatic agent on one surface side is higher than the average concentration of the antistatic agent of the entire film,
A resin film, wherein the content of the UV absorber on both surface sides is lower than the average concentration of the UV absorber in the entire film.

11. What is claimed is: 1. A resin film having a distribution of an antistatic agent in a thickness direction, wherein the resin film has a region with a low concentration of the antistatic agent outside a region with a high concentration of the antistatic agent.

[12] 12. The resin film according to any one of 1 to 11, wherein the resin film is a cellulose ester film.

13. The thickness is 100 μm or less, and the absolute value of impedance at a frequency of 20 Hz is 4 × 10
13. The resin film according to any one of the above items 1 to 12, which has a resistance of ⁵ Ω or more.

14. Any one of the above items 1 to 12, wherein the thickness of the resin film is 100 μm or less, the absolute value of impedance at a frequency of 20 Hz is 4 × 10 ⁵ Ω or more, and the surface is a cellulose ester.
Item 10. The resin film according to item 1.

15. Surface specific resistance is 1 × 10 ¹² Ω / cm ²
15. The resin film as described in any one of 1 to 14 above, wherein the temperature is (23 ° C., 55% RH).

16. The surface resistivity of the antistatic agent is 1 ×
16. The resin film according to any one of 1 to 15, wherein the resin film has a resistance of 10 ¹⁰ Ω or less.

17. By simultaneously extruding and casting a plurality of solutions having different additive compositions or concentrations from a die slit to a casting support, the resin film according to any one of 1 to 16 above is produced. A method for manufacturing a resin film.

18. In a method for producing a resin film, in which a plurality of solutions having different antistatic agent concentrations are simultaneously extruded and cast from a die slit to a casting support, the concentration of the antistatic agent on the casting support side of the resin film is the entire resin film. A method for producing a resin film, which is higher than the average concentration of an antistatic agent.

19. In a method for producing a resin film in which a plurality of solutions having different antistatic agent concentrations are simultaneously extruded and cast from a die slit to a casting support, a solution having a higher concentration of an antistatic agent is more antistatic than a solution having a higher concentration. A method for producing a resin film, comprising casting a solution having a low agent concentration.

20. In a resin film manufacturing method of simultaneously extruding and casting a plurality of solutions having different additive compositions or concentrations from a die slit to a casting support, the concentration of the antistatic agent on the casting support side of the resin film is reduced over the entire resin film. Wherein the concentration of fine particles on the surface side opposite to the casting support is higher than the average concentration of fine particles in the entire resin film.

21. From a plurality of casting ports provided at intervals such that a certain degree of drying can proceed until reaching the next casting port, a plurality of solutions having different additive compositions or concentrations are stacked, and A method for producing a resin film, comprising: producing the resin film according to any one of Claims 16 to 16.

22. Manufacture of a resin film in which a plurality of solutions having different additive compositions or concentrations are laminated from a plurality of casting ports provided at intervals so that a certain degree of drying can proceed until reaching the next casting port. A method for producing a resin film, which comprises first casting a solution containing an antistatic agent.

23. Manufacture of a resin film in which a plurality of solutions having different additive compositions or concentrations are laminated from a plurality of casting ports provided at intervals so that a certain degree of drying can proceed until reaching the next casting port. A method for producing a resin film, comprising casting a solution containing an antistatic agent and then casting a solution containing fine particles.

24. A method for producing a resin film, in which a solution is extruded from a die slit onto a casting support and cast, wherein the absolute value of the impedance of the resin film at a frequency of 20 Hz is 4 × 10 ⁵ Ω or more. Method.

25. In a resin film manufacturing method of simultaneously extruding and casting a plurality of solutions having different additive compositions or concentrations from a die slit to a casting support, an absolute value of impedance at a frequency of 20 Hz of the resin film is set to 4 × 10 ⁵ Ω or more. A method for producing a resin film.

26. In a resin film manufactured by simultaneously extruding and casting a plurality of solutions having different additive compositions or concentrations from a die slit to a casting support,
A resin film, wherein the absolute value of impedance at a frequency of 20 Hz of the resin film is 4 × 10 ⁵ Ω or more, and the friction coefficient of at least one surface is 0.40 or less.

27. The method for producing a resin film as described in 24 or 25 above, wherein the curl degree at 23 ° C. and 55% RH is not less than −10 and not more than +10.

28. A plurality of solutions having different additive compositions or concentrations are simultaneously extruded and cast from a die slit onto a casting support to form a resin film. After the resin film is saponified, the film has an absolute impedance of 20 Hz. A method for producing a resin film, wherein the value is 4 × 10 ⁵ Ω or more.

29. Any one of the above 1 to 16 and 26
29. A polarizing plate, characterized in that the resin film according to any one of items 17 to 25, 27 and 28 is a protective film for a polarizing plate.

30. A liquid crystal display device using the polarizing plate according to the item 29. Hereinafter, the present invention will be described in detail.

We have studied a method of directly adding an antistatic agent to a resin film in order to solve the above problems. As a result, it was found that the problem caused by forming the antistatic layer by the coating method can be solved by including the antistatic agent with a certain distribution in the thickness direction. Furthermore, it has been found that when the plasticizer, the ultraviolet absorber, and the fine particles have characteristics in the distribution in the thickness direction, not only the problem is solved, but also the resin can be made thinner, and a multifunctional film can be obtained. In addition, since the coating step can be omitted, it has been found that the method of manufacturing a film has high productivity.

As the antistatic agent of the present invention, any antistatic agent that can be added to the resin can be used. Examples of the anionic antistatic agent include fatty acid salts, higher alcohol sulfates, liquid fatty oil sulfates, and the like. Sulfates of aliphatic amines and aliphatic amides, phosphates of aliphatic alcohols, sulfonates of dibasic fatty acid esters, aliphatic amide sulfonates, alkyl allyl sulfonates, naphthalene sulfonates of formalin condensation, etc. Examples of the cationic antistatic agent include aliphatic amine salts, quaternary ammonium salts, and alkylpyridinium salts. Examples of nonionic antistatic agents include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and the like. Examples of the antistatic agent include an imidazoline derivative, a betaine-type higher alkylamino derivative, a sulfate ester derivative, a phosphate ester derivative, and the like. Shobo, Supplement "Practical Handbook of Additives for Plastics and Rubber p333
~ P455 "published by Chemical Industry Co., Ltd., JP-A-11-256143
No., JP-B-52-32572, JP-A-10-1584
No. 84, etc.

Preferred examples of the antistatic agent include ionic polymer compounds such as anionic antistatic agents and cationic antistatic agents. Examples of the ionic polymer compound include JP-B-49-23828 and JP-B-49-23.
No. 827 and No. 47-28937; anionic polymer compounds; Japanese Patent Publication No. 55-734;
No. 0-54672, JP-B-59-14735, 57
No.-18175, No.57-18176, No.57-56
No. 059 and the like, an ionene type polymer having a dissociation group in the main chain: JP-B-53-13223, JP-B-57-15376, JP-B-53-45231, and JP-B-53-45231.
Nos. 5-145783, 55-65950, 55-
67746, 57-11342, 57-197
No. 35, JP-B-58-56858, JP-A-61-27
853 and 62-9346, cationic pendant polymers having a cationic dissociating group in the side chain, and graft copolymers such as those described in JP-A-5-230161. it can.

Further, other preferable antistatic agents include:
An example is a metal oxide having conductivity. Examples of metal oxides are ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , I
n ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O
₅ or the like or a composite oxide thereof is preferable, and particularly, Zn
O, TiO ₂ and SnO ₂ are preferred. Examples of containing heteroatoms include, for example, addition of Al and In to ZnO, addition of Nb and Ta to TiO ₂ , and addition of SnO ₂
For this, the addition of Sb, Nb, a halogen element or the like is effective. The addition amount of these different atoms is 0.01 mol%
２５25 mol% is preferred, but 0.1 mol%
A range of 15 mol% is particularly preferred.

The volume resistivity of these conductive metal oxide powders is 10 ⁷ Ωcm or less, particularly 10 ⁵ Ωcm.
Powder having a specific structure having a primary particle diameter of not less than 100 ° and not more than 0.2 μm and a long diameter of a higher-order structure of not less than 300 ° and not more than 6 μm in a volume fraction of 0.01 to the conductive layer.
% Or more.

Particularly preferred antistatic agents have a surface specific resistance of 1 × 10 ¹⁰ Ω or less in view of the relationship between the antistatic performance and the amount added. The surface resistivity value of the sample was 23
After humidity control in an atmosphere of 50 ° C. and 50% RH for 24 hours, measurement is performed using a super insulation meter in accordance with ASTM D257.

Particularly preferred antistatic agents are disclosed in JP-A-9-2.
It is desirable to contain an ionene conductive polymer described in No. 03810 or a quaternary ammonium cation conductive polymer having an intermolecular crosslink.

The characteristic of the crosslinked cationic conductive polymer resides in the dispersible granular polymer obtained, and the cationic component in the particles can be provided with a high concentration and a high density, so that it has excellent conductivity. Not only that, it has good compatibility with the resin and high transparency is selected. Further, even under a low relative humidity, no deterioration in conductivity is observed.

The dispersible particulate polymer, which is a cross-linkable cationic conductive polymer used for antistatic, generally has a particle size in the range of about 0.01 μm to 0.3 μm, preferably in the range of 0.05 μm to 0.15 μm. Particle size is used. As used herein, the term "dispersible particulate polymer" is a polymer that appears to be a clear or slightly cloudy solution by visual observation, but appears as a particulate dispersion under an electron microscope.

Preferred examples of these compounds include the following compounds.

[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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As another ionic polymer compound, sulfonated polystyrene as described in JP-B-48-23451 is particularly preferred as an antistatic agent.

Further, an alkali metal salt of a phosphate ester compound represented by the following general formula described in JP-B-52-32572 is mentioned as a particularly preferred antistatic agent.

[0061]

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In the formula, R represents a substituted or specific substituted alkyl group having 8 to 22 carbon atoms. R is, for example, a group such as octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl and the like.
R may also include one or more substituted or unsubstituted benzene rings, with or without direct attachment to a phosphate group, such as phenyl, octylphenyl, and the like. Examples of the alkali metal include sodium, potassium, rubidium and cesium.

In addition, an antistatic agent represented by the following general formula is also preferable.

[0064]

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In the formula, M represents a sulfonic acid group or a phosphoric acid group,
R represents an alkyl group or an alkenyl group having 4 to 22 carbon atoms. n represents an integer of 1 to 3. When n is 0, one R represents an alkyl group having 1 to 18 carbon atoms substituted with a sulfonic acid group, a phosphoric acid group, or a quaternary ammonium group.

The following are examples of these particularly preferred antistatic agents.

[0067]

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[0068]

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The amount of the antistatic agent varies depending on the specific resistance and the type of the resin.
It is preferably at most 00 kg, particularly preferably at most 50 kg.

The method of adding the antistatic agent may be a method of directly adding the antistatic agent to a dope solution described later, a method of adding the antistatic agent after dissolving it in a solvent such as water, methanol, acetone, butanol, cyclohexane or dichloromethane, or a method of adding the antistatic agent. There is a method in which an agent is stirred and mixed in a solvent, then dispersed by a disperser, and a fine particle dispersion liquid is added to a dope liquid. A binder such as cellulose acetate may be added to the dispersion. You may use together with additives, such as a fine particle dispersion, a UV absorber, a dye, a stabilizer (reducing agent), and a plasticizer. Preferred amounts of these additives vary depending on the antistatic agent,
It is preferably 0.5 or less based on 1 mass of the binder.
More preferably, it is 0.3 or less.

As another method of applying the antistatic agent to the resin film in a distributed manner, a solution containing the antistatic agent or a solution containing the antistatic agent after casting and before the solvent is completely evaporated (the residual solvent is 2% by mass or more). How to blow gas. A method of impregnating a solution of a solvent that dissolves or swells a resin film containing an antistatic agent. There is a method of exposing a resin film to a treatment system that performs plasma discharge in the presence of a reactive gas capable of imparting antistatic properties.

As the resin film of the present invention, any transparent resin film can be used. For example, a cellulose ester film, a polyester film, a polycarbonate film, a norbornene resin film, a polyarylate film, a polysulfone film and the like can be mentioned. Among these, a cellulose acetate resin film such as triacetyl cellulose and a biaxially stretched polyester are preferably used because of their excellent transparency and durability. Further, a polycarbonate film excellent in durability and mechanical strength is also preferable. The thickness is usually 30 μm to 1000 μm
A degree is suitably used.

Of the cellulose ester films mentioned as preferred among the resin films according to the present invention, particularly preferred are lower fatty acid esters of cellulose. The lower fatty acid in the lower fatty acid ester of the cellulose ester means a fatty acid having 6 or less carbon atoms, for example, cellulose acetate, cellulose propionate, cellulose butyrate and the like are preferred examples of the lower fatty acid ester of cellulose. .

In addition to the above, Japanese Patent Application Laid-Open No. H10-458
04, 8-2311761, U.S. Pat.
Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in JP-A-9,052 and the like can be used.

Among the above descriptions, a particularly preferred lower fatty acid ester of cellulose is cellulose triacetate.

Further, from the viewpoint of base strength, it is particularly preferable to use a polymerization degree of 250 to 400, an amount of bound acetic acid of 54.0 to 62.5%, and a weight average molecular weight of 70,000.
~ 120,000, preferably 80,000-100,
000 is more preferred. More preferred is cellulose triacetate having an amount of bound acetic acid of 58 to 62.5%.

As the cellulose triacetate according to the present invention, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. If the releasability from the belt or drum becomes a problem, it is preferable to use a large amount of cellulose triacetate synthesized from cotton linter having good releasability from the belt or drum because the productivity is high.

When cellulose triacetate synthesized from wood pulp is mixed and used, the ratio of cellulose triacetate synthesized from cotton linters is preferably 40% by mass or more, and the effect of releasability becomes remarkable. Is more preferable, and it is most preferable to use it alone.

The method of co-casting according to the production method of the present invention will be described. Co-casting is a simultaneous multilayer casting method in which two or more layers are merged in a die having two or more slits to form two or more layers, a sequential multilayer casting method in which two or more layers are formed through different dies, Any of the multilayer casting methods combining the simultaneous multilayer casting and the sequential multilayer casting may be used.

In the present invention, the dope solution in which the cellulose ester is dissolved is a state in which the cellulose ester is dissolved in a solvent (solvent), and the dope solution contains a plasticizer, a UV absorber, fine particles and the like. May be added, and needless to say, other additives can be added. The concentration of the cellulose ester in the dope solution is preferably 10 to 30% by mass, more preferably 1 to 30% by mass.
8 to 20% by mass.

The solvents used in the present invention may be used alone or in combination. However, it is preferable to use a mixture of a good solvent and a poor solvent from the viewpoint of production efficiency. More preferably, a mixture of a good solvent and a poor solvent is used. The ratio is such that the good solvent is 70 to 95% by mass and the poor solvent is 5 to 30% by mass.

The good solvent and the poor solvent used in the present invention are:
Those that dissolve the cellulose ester used alone are defined as good solvents, and those that swell or do not dissolve alone are defined as poor solvents. Therefore, the good solvent and the poor solvent vary depending on the amount of bound acetic acid of the cellulose ester. For example, when acetone is used as a solvent, a good solvent is obtained when the amount of bound acetic acid of cellulose ester is 55%, and the amount of bound acetic acid is 6%.
At 0%, it becomes a poor solvent.

Examples of good solvents used in the present invention include organic halogen compounds such as methylene chloride and dioxolanes.

As the poor solvent used in the present invention, for example, methanol, ethanol, n-butanol, cyclohexane and the like are preferably used.

In preparing the above-mentioned dope solution, as a method for dissolving the cellulose ester, a general method can be used, but a preferable method is to mix the cellulose ester with a poor solvent and wet or swell. Let
Further, a method of mixing with a good solvent is preferably used. At this time, under pressure, the method of heating at a temperature not lower than the boiling point of the solvent at room temperature and the solvent does not boil, and dissolving while stirring, in order to prevent the generation of a massive undissolved substance called gel or mamako, More preferred.

The pressurization may be carried out by pressurizing an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature after the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and not boiling the solvent, and is preferably set in the range of, for example, 60 ° C. or higher, and 70 to 110 ° C. . The pressure is adjusted at the set temperature so that the solvent does not boil.

After the dissolution, the resin is taken out of the container while cooling, or is taken out of the container by a pump or the like, cooled with a heat exchanger or the like, and supplied for film formation. The cooling temperature at this time may be cooled to room temperature, but it is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced.

For example, in the production of a film having a distribution of the content of the antistatic agent of the present invention, a solution in which the antistatic agent and a small amount of the cellulose ester are dissolved in a dope solution in which the cellulose ester is dissolved in a solvent is used. Is mixed and dispersed in an in-line mixer to produce a dope solution A and a dope solution B in which cellulose ester is dissolved (if necessary,
Separately, a plasticizer and an ultraviolet absorber added in-line are added) and a dope solution A containing an antistatic agent is directly applied to the casting belt using a die slit having a plurality of slits. After co-casting (casting step) and then heating to remove a part of the solvent (drying step on the casting belt), it was peeled off from the casting belt and peeled off By drying the film (film drying step), a cellulose ester film having a high concentration distribution of the antistatic agent on one surface side of the present invention can be obtained.

The surface side in the present invention refers to a portion from the film surface to a depth of 10 μm, and the concentration of the antistatic agent on at least one surface side is lower than the average concentration of the antistatic agent in the entire resin film. It needs to be different. In this case, when the concentration of the antistatic agent on at least one surface is high and the concentration of the antistatic agent other than the surface is low, or vice versa, the surface contains a high concentration of the antistatic agent. It is more preferable to be able to exert the effect of the present invention more.

Examples of the distribution of the antistatic agent of the present invention include:
Dope with a high concentration of antistatic agent is cast from the die slit farthest from the casting belt, and a configuration in which the concentration of the antistatic agent is distributed high on the surface farthest from the casting belt,
It is preferable from the viewpoint of antistatic performance that the concentration of the antistatic agent is distributed high on the surface side of the casting belt. Further, there may be a high concentration distribution of the antistatic agent on both surface sides. Another preferable reason that the antistatic agent is distributed on the surface side is that when a die slit composed of a plurality of slits is used, the thickness extruded from the central side die slit is generally thick, and the die slits on both sides are thin. In many cases, this is also preferable in that the amount of the antistatic agent can be reduced.

As a method for detecting the presence of the antistatic agent with a distribution, a method of measuring the distribution of elements contained in the antistatic agent in the cross section of the resin film, a method in which the surface of the resin film is gradually and uniformly spread from the surface side. There are a method of shaving, a method of detecting with a thickness at which the surface resistivity or the impedance changes, a method of uniformly shaving the resin film surface gradually, dissolving it in a solvent, and separating and quantifying an antistatic agent.

The concentration distribution of the antistatic agent in the film thickness direction is as follows.
From the viewpoint of preventing curling, the contents of the antistatic agent, the plasticizer, the fine particles, and the like may be adjusted to make the contents symmetric with respect to the center in the thickness direction of the film.

Further, the film of the present invention in which the concentration of the antistatic agent on one surface side is higher than the concentration of the whole film, and the other surface side where a large amount of fine particle matting agent is distributed, is used as the antistatic agent. A dope containing fine particles and a dope containing fine particles are first co-cast so that a dope having a high concentration of an antistatic agent comes to the casting belt side, or a dope containing fine particles in a casting belt. Is first cast, and a dope having a high concentration of the antistatic agent is cast from the die slit farthest from this, so that a high concentration of the antistatic agent is distributed on one surface and fine particles (matte) are distributed on the other surface. Agent) can be obtained.

A film in which the concentration of the plasticizer or the UV absorber is lower than the average concentration of the entire film on both surface sides of the film and the concentration of the antistatic agent is higher on one surface side is also the same as the antistatic film. For example, a dope containing a large amount of an agent and having a low concentration of a plasticizer or a UV absorber is poured onto a casting belt, for example, and a dope having a low concentration of an antistatic agent and a high concentration of a plasticizer or a UV absorber is flown over the casting belt. And then a dope with a low concentration of a plasticizer or a UV absorber is further cast thereon. Also, by adding a large amount of fine particles into the dope having a low concentration of the last plasticizer or UV absorber, the concentration of the antistatic agent on one surface is higher than the average concentration of the entire film, and the concentration of the fine particles on the other surface is low. A film whose content is also higher than the average content of the entire film can be obtained.

Thus, fine particles used as a matting agent,
In the present invention, it is preferable that the concentration of additives such as a plasticizer and a UV absorber has a difference between the concentration within 10 μm on the surface side and the average concentration of the whole film.

In the present invention, the concentration of the antistatic agent on the surface is 1.05 times or more the average concentration of the whole film.
It is preferably set to be 20 times higher, and more preferably 1.5 times to 10 times.

When the fine particles and the antistatic agent are present together,
It has been found that the frictional resistance is lower than in the case of adding the fine particles alone, and that the blocking becomes difficult. That is, when an antistatic agent is added, an equivalent blocking prevention effect can be obtained with an addition amount that is half or less than the addition amount of ordinary fine particles. Although the reason is unknown, it is presumed that the presence of the antistatic agent suppresses the generation of electric charge at the time of rubbing, resulting in a decrease in the frictional resistance value.

The content of fine particles is preferably 1.05 to 20 times higher than the average content of the entire film on the surface side, and more preferably 1.5 to 10 times.

Further, it has been found that when the plasticizer and the antistatic agent are present together, the impedance unexpectedly increases and the value of the surface resistivity decreases unexpectedly. Although the cause is also unknown, it is presumed that one of the causes is an increase in the moving speed of the ionic substance that contributes to conductivity.

The concentration of the plasticizer or UV absorber on the surface is preferably 0.8 times or less, more preferably 0.5 times or less, of the average of the whole film.

As described above, when an antistatic agent is contained in a film, a problem caused by providing an antistatic layer separately on a resin film, for example, in an alkali saponification step when the film is used as a protective film for a polarizing plate. Improvement of the problem that the anti-static layer on the substrate is damaged, the curl becomes large due to the influence of the coating solvent on the base material, and the problem that additives are deposited during production and contaminates the process or deposits on the film Thus, a thin, high-strength resin film can be obtained. Furthermore, there is no blocking with the film back surface, and a resin film with sufficient adhesiveness to the polarizer and high productivity can be obtained, whereby the resin film of the present invention is sufficient for thinning and miniaturizing liquid crystal display materials. Can respond.

Further, the film obtained in this manner is more suitable for a case where a film to be described later is bonded to a polarizer to form a polarizing plate than a state where the layer having an antistatic agent is completely exposed on the surface. For further handling, it is more preferable to form a film having a region having a low concentration of the antistatic agent, more preferably a region containing no antistatic agent, outside the region having a high concentration of the antistatic agent. Similarly, before casting a dope having a high concentration of an antistatic agent, these films do not contain an antistatic agent. For example, when a dope of a cellulose ester is produced by a co-casting method, the first casting belt side or the casting belt is used. From the furthest side (ie, outside the dope containing a large amount of antistatic agent). Preferred examples of the cellulose ester include the above-mentioned triacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like, and particularly preferred is cellulose triacetate. The concentration of the antistatic agent in these layers is desirably 50% or less, more preferably 20% or less, of the concentration of the surface side region containing the antistatic agent at a concentration higher than the average value of the whole film. Yes, most preferred 1%
It is as follows. These layers preferably have a region (layer) having a thickness of 0.5 μm or more and 10 μm or less formed on a surface region containing a large amount of an antistatic agent.

By providing a structure having a low concentration of an antistatic agent or a region containing no antistatic agent on the outside, such as cellulose triacetate, the saponification treatment in the bonding step with the polarizer described above. This is preferable because damage to the film surface can be prevented. It is preferable that the concentration of the antistatic agent be lower than that of the outermost layer in the outermost layer or that the outermost layer contains no antistatic agent.

The resin film of the present invention thus produced has a curl degree of −10 or more + 1 at 23 ° C. and 55% RH.
It is desirably 0 or less.

The curl degree is measured by the following method. After leaving the film sample in an environment of 25 ° C. and 55% RH for 3 days, the film was placed in a width direction of 50 mm and a longitudinal direction of 2 mm.
mm. In addition, the film piece was kept at 23 ° C ±
The film is conditioned for 24 hours in an environment of 2 ° C. and 55% RH, and the curl value of the film is measured using a curvature scale. The curl degree was measured according to the method A of JIS-K7619-1988.

The curl value is represented by 1 / R, where R is the radius of curvature and the unit is m. As for the curl value, it is preferable that the deformation of the film is small, and the deformation direction may be either the + direction or the − direction. That is, the absolute value of the curl value only needs to be small. Specifically, when the absolute value of the curl value of the film is larger than 10, when a polarizing plate or the like is manufactured using the film, the film under high temperature and high humidity may be used. Deformation such as warpage becomes large and cannot be used. The curl value of the film is 1
If it is 0 or less, when a polarizing plate or the like is produced using the film, deformation such as warpage can be reduced even under high temperature and high humidity.

FIG. 1 shows a preferred example of an apparatus capable of simultaneous casting and continuous casting used in the present invention.

Reference numerals 1a to 1d denote dope tanks, respectively.
2a to 2c each represent an in-line mixer. 3a
-3c represents a pump, and 4 represents a co-casting die. FIG. 2 shows an enlarged cross-sectional view of the co-casting die.
1b, 10 and 9 are provided.
Each dope for casting is a die slit 11a, 1
The laminar flow is formed at the converging point by being supplied to
From the die slit on the casting belt. 6 is a support (belt) for casting, and 5
A rotating drum, 8 represents a cellulose ester film that has been peeled off after the solvent is appropriately evaporated after casting.
Reference numeral 7 denotes a roller for transporting the cellulose ester film. For example, when 1d is an antistatic agent solution, dope A, dope A,
Fill the dope B and the dope C, change the flow rate of the pumps 3a to 3c, change the mixing amount of the antistatic agent from the in-line mixers 2a to 2c, uniformly mix each, and then supply the mixture through three slits for casting. By doing so, a three-layer co-cast film having the components of the tank 1c on the casting belt side is obtained. By increasing the amount of the antistatic agent additive solution mixed with the dope C, a film having a high antistatic agent concentration can be obtained on the belt side surface.

The concentration distribution of the dope B and the dope A can be adjusted by adjusting the concentration of the plasticizer or the UV absorber, respectively, and the resin film of the present invention can be obtained.

FIG. 3 shows a continuous casting method in which a dope supplied from one die is moved on a casting belt and a second die is provided at an interval so that drying to some extent can proceed. It is an example of an apparatus. Dope solution tanks 1e to 1h and inline mixers 2e to 2h attached thereto (the additive solution supply line and the additive solution tank are omitted), and
Die co-casting dies 14, 24 each having two die slits are also set on the casting belt 6, and each dope is sequentially cast to form four layers in this case. This is an apparatus that can supply four types of dopes having different compositions by co-casting. In this case, after the dope liquid supplied from the die 14 has been dried to some extent on the belt, another dope liquid is supplied from the die 24, and co-casting with dopes having different compositions can be performed.

The interval at which a certain amount of drying can proceed before reaching the next casting port cannot be said unambiguously because it depends on the drying conditions such as the drying temperature. The interval is such that 90% or less of the solvent in the dope is removed by drying, preferably 20% to 80%.
%, And if the drying is too much, adhesion at the interface with the dope to be cast next will not be sufficient and the integrity as a film will be lost. Less drying has the same effect as co-casting, and the mixing of dope components due to sequential casting progresses, and when the drying progresses a little, application of the next dope component causes a gradient in component concentration. It becomes difficult to control to give.

The support in the casting step is preferably a belt-shaped or drum-shaped stainless steel mirror-finished support. The temperature of the support in the casting step can be cast in a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, but casting on the support at 0 to 30 ° C. causes gelation of the dope. It is preferable because the time limit for peeling can be shortened, and it is more preferable to cast on a support at 5 to 15 ° C. The peeling limit time refers to the time during which the cast dope remains on the support at the limit of the casting speed at which a transparent film having good flatness can be continuously obtained.
It is preferable that the peeling limit time is short because the productivity is excellent.

The surface temperature of the support on the side to be cast (cast) is 0 to 30 ° C., the temperature of the solution is 25 to 60 ° C., and the temperature of the solution is higher than the temperature of the support by 0 ° C. or more. Is preferably set to 5 ° C. or more. The higher the temperature of the solution and the temperature of the support, the higher the drying rate of the solvent can be. Therefore, if the temperature is too high, foaming or flatness may be deteriorated.

A more preferred range of the temperature of the support is 5 to 5.
15 ° C., a more preferable range of the solution temperature is 35 to 45 ° C.
It is.

The temperature of the support at the time of peeling is set to 10 to 4
The temperature is preferably set to 0 ° C, more preferably 15 to 30 ° C, because the adhesion between the film and the support can be reduced.

In order for the cellulose ester film at the time of production to exhibit good flatness, the amount of residual solvent when peeled from the support is preferably from 10 to 80%, more preferably from 20 to 40%, or from 60 to 40%. 80%, particularly preferably 20 to 30%.

In the present invention, the amount of the residual solvent is defined by the following formula. Residual solvent amount = (mass before heat treatment−mass after heat treatment) /
(Mass after heat treatment) × 100% In addition, the heat treatment in the measurement of the amount of the residual solvent indicates that the film is heated at 115 ° C. for 1 hour.

The peeling tension at the time of peeling the film from the support is usually 200 to 250 N / m (Newton / m), but the cellulose ester film of the present invention, which is thinner than the conventional one, is Since wrinkles are likely to be formed at the time of peeling, it is preferable to peel at a minimum tension at which peeling can be performed to 170 N / m, and more preferably at a minimum tension to 1 N / m.
Peeling at 40 N / m.

In the drying step of the cellulose ester film, the film peeled from the support is further dried so that the residual solvent amount is preferably 3% by mass or less, more preferably 0.5% by mass or less. is there.

In the film drying step, a method of drying while transporting a film by a roll hanging method or a pin tenter method is generally employed. For liquid crystal display members, it is preferable to dry while maintaining the width by a pin tenter method in order to improve dimensional stability. In particular, it is particularly preferable to maintain the width at a place where the amount of the residual solvent is large immediately after peeling off from the support, since the effect of improving the dimensional stability is further exhibited. 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 40
It is preferable that the temperature is gradually increased in three to five steps in the range of 150 to 150 ° C., and it is more preferable to perform in the range of 80 to 140 ° C. in order to improve dimensional stability.

The resin film of the present invention, particularly preferably used cellulose ester film preferably contains a plasticizer. There is no particular limitation on the plasticizer that can be used, but in the case of phosphate esters, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Phthalates are diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc. It is preferable to use ethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate or the like alone or in combination. There.

Of these, it is particularly preferable to use a plasticizer having a freezing point of 25 ° C. or lower in combination, because of its excellent dimensional stability and water resistance. The plasticizer having a freezing point of 25 ° C. or lower is not particularly limited as long as the freezing point is 25 ° C. or lower, and can be selected from the above plasticizers. For example, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, diethyl phthalate, dimethyl phthalate,
Dioctyl phthalate, dibutyl phthalate, di-2-
Ethylhexyl phthalate, triacetin, ethylphthalylethyl glycolate and the like can be mentioned. It is also preferable to use these plasticizers alone or in combination.

The freezing point in the present invention is defined as the true freezing point described in the Encyclopedia of Chemistry published by Kyoritsu Shuppan Co., Ltd.

The amount of these plasticizers to be used is 1 to 1 with respect to cellulose ester in terms of film performance, processability and the like.
15% by mass is preferred. For a liquid crystal display member, the content is more preferably 5 to 15% by mass, particularly preferably 7 to 12% by mass, from the viewpoint of dimensional stability.

The content of the plasticizer having a freezing point of 25 ° C. or less based on the cellulose ester is preferably 1% by mass to 10% by mass, more preferably 3% by mass to 7% by mass.

It is preferable that the proportion of the plasticizer having a freezing point of 25 ° C. or lower in the total plasticizer is large because the flexibility of the cellulose ester film is improved and the processability is excellent. Most preferably, all of the plasticizers are plasticizers having a freezing point of 25 ° C. or lower.

It is preferable to use a plasticizer having a freezing point of 25 ° C. or lower in an amount of 1% by mass based on the cellulose ester since the flexibility of the cellulose ester film is improved and the processability is excellent. The use of a plasticizer having a freezing point of 14 ° C. or lower is preferred because the processability is further improved.

The workability refers to the ease with which a base film or a liquid crystal display member can be processed by slitting or punching. If the workability is poor, the cut surface becomes saw-toothed, and chips are generated. Undesirably because they adhere to the surface and become defective.

With respect to the distribution of the plasticizer in the film,
As described above, the concentration on the surface side of the film is preferably lower than the average concentration of the entire film as described above, since this may cause a process failure due to evaporation of the plasticizer in the drying step or the heat treatment step or an appearance failure due to reattachment. preferable.

The fine particles according to the present invention include inorganic compounds and organic compounds. As inorganic compounds,
Compounds containing silicon, silicon dioxide, aluminum oxide,
Zirconium oxide, calcium carbonate, talc, clay,
Preference is given to calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate, more preferably inorganic compounds containing silicon or zirconium oxide, but turbidity of the cellulose ester laminated film. Can be reduced,
Silicon dioxide is particularly preferably used.

The fine particles of silicon dioxide according to the present invention include, for example, Aerosil R972, R974 and R81.
2,200,200V, 300, R202, OX50,
Commercial products having a trade name such as TT600 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.

As the fine particles of zirconium oxide according to the present invention, those commercially available under the trade names such as Aerosil R976 and R811 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.

As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used.

Among the silicone resins described above, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, and 1
Commercial products having trade names such as Nos. 45, 3120 and 240 (all manufactured by Toshiba Silicone Co., Ltd.) can be used.

The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm, from the viewpoint of suppressing haze.

The primary average particle diameter of the fine particles was measured by observing the particles with a transmission electron microscope (magnification 500,000 to 2,000,000 times), observing 100 particles, and determining the average value as 1
The secondary average particle diameter was used.

As a method for preparing a dispersion liquid of fine particles according to the present invention, for example, a method in which a solvent and fine particles are stirred and mixed and then dispersed by a disperser as shown below. This is used as a fine particle dispersion, and the fine particle dispersion is added to the dope solution and stirred.

Also, after dispersing the fine particle dispersion, a small amount of cellulose triacetate is separately added to a solvent, and a solution obtained by stirring and dissolving is added, followed by stirring to obtain a fine particle additive solution, which is sufficiently mixed with the dope solution by an in-line mixer. .

Further, a small amount of cellulose triacetate is added to a solvent, dissolved by stirring, fine particles are added thereto, and the mixture is dispersed with a dispersing machine. There is.

The first method is excellent in dispersibility of fine particles of silicon dioxide, and the second method is excellent in that the fine particles of silicon dioxide are hard to re-aggregate. The third method is a preferable preparation method which is excellent in both the dispersibility of the fine particles of silicon dioxide and the difficulty of re-aggregating the fine particles of silicon dioxide.

(Dispersion method) When silicon dioxide fine particles are mixed with a solvent or the like and dispersed, the concentration of silicon dioxide is 5 to 30.
% By mass, more preferably 10 to 25% by mass, and most preferably 15 to 20% by mass. 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.

The amount of the silicon dioxide fine particles added to the cellulose ester is preferably 0.01 to 0.3 kg, more preferably 0.05 to 0.2 kg, per 100 kg of the cellulose ester. , 0.08-0.12 kg.
The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the lower the haze and the smaller the agglomerates.

The dispersers for performing the above-mentioned dispersion are roughly divided into media dispersers and medialess dispersers. For dispersing silicon dioxide fine particles, a medialess disperser is preferred because it has a low haze.

Examples of the media dispersing machine include a ball mill, a sand mill, a dyno mill and the like.

As the medialess disperser, there are an ultrasonic type, a centrifugal type, a high-pressure type, and the like. In the present invention, a high-pressure disperser is preferable. The high-pressure dispersing device is a device that creates a special condition such as a high shear or a high pressure state by allowing a composition in which fine particles and a solvent are mixed to pass through a thin tube at a high speed. When processing with a high-pressure dispersion device, for example, a tube diameter of 1 to 2000 μm
It is preferable that the maximum pressure condition inside the device in the narrow tube of m is 10 MPa or more. More preferably, it is 20 MPa or more. In this case, it is preferable that the maximum arrival speed reaches 100 m / sec or more, and the heat transfer speed reaches 420 Joule / hr or more.

The high-pressure dispersion apparatus as described above includes Micro
There is an ultrahigh-pressure homogenizer (trade name: Microfluidizer) manufactured by Fluidics Corporation or a Nanomizer manufactured by Nanomizer, and a homogenizer of the Manton-Gaulin type, such as a homogenizer manufactured by Izumi Food Machinery, a UHN- manufactured by Sanwa Machine Co., Ltd. 01 and the like.

Although the reason is unknown, it is preferable to cast the layer containing the fine particles according to the present invention so as to be in direct contact with the casting support. In order to achieve both transparency and anti-blocking performance, it is particularly preferable to increase the content on at least one surface side. Therefore, as described above, the constitution of the present invention in which the concentration of the antistatic agent on one surface of the resin film is higher than the average concentration and the content of fine particles on the other surface is increased is particularly preferable.

In the present invention, as described above, an ultraviolet absorber is preferably used. As an ultraviolet absorber, a wavelength of 37
From the viewpoint of excellent absorbability of ultraviolet light of 0 nm or less and good liquid crystal display properties, those having little absorption of visible light having a wavelength of 400 nm or more are preferable.

Specific examples of the ultraviolet absorber preferably used in the present invention include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds and the like. No.

As the benzotriazole ultraviolet absorber, a compound represented by the following general formula [1] is preferably used.

[0154]

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In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and include a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, and an alkoxy group. group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group or a 5- to 6-membered heterocyclic group, the carbon of R ₄ and R ₅ are 5- or 6-membered ring closure A ring may be formed.

The following are specific examples of the ultraviolet absorbent according to the present invention, but the present invention is not limited thereto.

UV-1: 2- (2'-hydroxy-5 '
-Methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-
tert-butylphenyl) benzotriazole UV-3: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-
tert-butylphenyl) -5-chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ",
4 ", 5", 6 "-tetrahydrophthalimidomethyl)
-5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,
3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) UV-7: 2- (2'-hydroxy-3'-tert-
(Butyl-5'-methylphenyl) -5-chlorobenzotriazole A compound represented by the following general formula [2] is preferably used as a benzophenone-based ultraviolet absorber which is one of the ultraviolet absorbers according to the present invention.

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In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group and a phenyl group, and these alkyl group, alkenyl group and phenyl group may have a substituent. A is a hydrogen atom,
Represents an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or a -CO (NH) n-1-D group, wherein D has an alkyl group, an alkenyl group or a substituent; Represents a phenyl group. m and n represent 1 or 2.

In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxy group is, for example, an alkoxy group having up to 18 carbon atoms, and the alkenyl group is, for example, carbon atom having up to 18 carbon atoms. Number 1
The alkenyl group up to 6 represents, for example, an allyl group, a 2-butenyl group and the like. Examples of the substituent on the alkyl group, alkenyl group and phenyl group include halogen atoms such as chlor, bromo and fluorine atoms, hydroxy group, phenyl group, and the like. May be used).

Hereinafter, specific examples of the benzophenone-based compound represented by the general formula [2] will be shown, but the present invention is not limited thereto.

UV-8: 2,4-dihydroxybenzophenone UV-9: 2,2'-dihydroxy-4-methoxybenzophenone UV-10: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-11: bis ( 2-methoxy-4-hydroxy-5
-Benzoylphenylmethane) The above-mentioned ultraviolet absorber preferably used in the present invention is a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber having high transparency and an excellent effect of preventing deterioration of a polarizing plate or a liquid crystal element. A benzotriazole-based ultraviolet absorber which causes less unnecessary coloring is particularly preferable.

Regarding the distribution of the UV absorber in the film, the UV absorber moves to the surface together with the plasticizer in the drying step and the heat treatment step, thereby contaminating the step and causing an appearance failure due to reattachment and the like. The content of the UV absorber is preferably such that the concentration on the film surface side is lower than the average concentration of the entire film.

The resin film of the present invention is characterized in that the number of bright spot foreign matters observed under polarized cross nicol is small.

The bright spot foreign matter is in an orthogonal state (crossed Nicols)
When a resin film is placed between the two polarizers arranged in the above, light is radiated from the outside of one and observed from the outside of the other polarizer. It means that a light emission phenomenon occurs. 200 or less foreign substances having a size of 5 to 50 μm recognized in the polarization crossed Nicols state per 250 mm ² area (preferably 10
0 or less, further 90 or less, especially 50 or less leaves), and the size recognized in the polarization crossed Nicol state is 50 μm.
The number of foreign substances exceeding m is substantially zero per area of 250 mm ² .

In the resin film of the present invention in which the concentration of the antistatic agent differs from the surface side of the resin, the retardation value of the film is preferably 100 nm or less.

The retardation is defined as the product (Δn · multiplier) of the difference (Δn) between the refractive index in the slow axis direction and the fast axis direction in the birefringence of the transparent resin film and the thickness (d) of the film.
This is a value based on d). When a film having a high retardation value is used for the protective film of the polarizer, transmission light is lost according to the deviation between the light absorption axis of the polarizing film and the optical axis of the transparent protective layer, and the degree of polarization is greatly reduced. . Therefore, a lower retardation value is preferable as a protective film for a polarizer. In the resin film of the present invention, the retardation value is 100 nm or less, preferably 10 nm,
Particularly preferably, it is 5 nm or less.

As is known, the conductivity of a material can be a cation,
It is expressed by an anion or a charge carrier such as an electron or a hole present in a particle.

When the main charge carriers are ions, they become solid electrolytes. When the charge carriers are electrons, they become semiconductors.

Further, when the conductivity was examined in detail, the absolute value of the impedance Z including the term of resistance generally decreased as the conductivity of the material increased as shown in the following equation (1). It is known.

| Z | = [R ² + (1 / ωC) ² ] ^1/2 (1) where, Z: impedance R: resistance C: capacitance ω: 2πf f: frequency

In the present invention, for measuring the impedance of a film material, a general impedance measuring device used for measuring the permittivity of an electronic component can be used. Preferably, an impedance measuring device capable of measuring a frequency of 1 Hz or more is used. This is an apparatus that combines electrodes for film measurement. For example, a combination of a precision LCR meter HP4284A and HP16451B manufactured by Yokogawa-Hewlett-Packard (hereinafter, manufactured by YHP). When using another device, it is necessary to correct the electrode portion. In order to achieve the present invention, it is necessary to correctly measure the impedance of the film material. Therefore, when an uncorrectable device is used, a favorable result cannot be obtained. An example of obtaining the absolute value of the impedance at 20 Hz using this combination of devices will be described in detail. However, if the absolute value of the impedance of the film material at an accurate frequency of 20 Hz can be measured, the present invention does not limit the measuring method.

Using a precision LCR meter HP4284A connected to an HP16451B having two electrodes composed of parallel planes and a guard electrode, at 23 ° C. and 55%
Under an RH atmosphere, the absolute value of the impedance of the film material is measured by a gap method. Regarding the measurement of the void method,
Follow the electrode non-contact method described in the instruction manual of HP16451B. The size of the sample is not particularly limited as long as it is larger than the plane of the electrode, but when the diameter of the main electrode is 3.8 cm (11.335 cm ² ), a square sample of 6 cm × 6 cm to 5 cm × 5 cm is used. preferable. If the magnitude of the surface resistivity measured using the direct current of the sample is the same on the front and back, either side may be raised, but if the front and back are not equal, the surface with the lower surface resistivity is raised A sample is placed between two electrodes composed of parallel planes, and measurement is performed by the air gap method while applying an AC voltage.

The preferred range measured is the frequency 20 measured using an electrode having an area of 11 to 12 cm ^2.
The absolute value of the impedance at Hz is 4 × 10 ⁵ Ω or more, preferably 4 × 10 ⁵ Ω or more and 1 × 10 ²⁰ Ω or less, more preferably 5 × 10 ⁵ Ω or more and 1 × 10 ¹⁴ Ω or less.

The surface resistivity is 1 × 10 ¹² Ω / cm ² or less (23 ° C., 55% RH), preferably 5 × 10 ¹¹
Ω / cm ² or less (23 ° C., 55% RH).

For the measurement of the surface resistivity, the sample was heated at 28 ° C. and 55 ° C.
After leaving for 1 hour or more under the condition of% RH, the surface resistance was measured with an insulation resistance measuring instrument (VE-30 type, manufactured by Kawaguchi Electric Co., Ltd.). The surface resistivity of the present invention is 1 × 10 ¹² Ω / cm ^2.
The following (23 ° C., 55% RH) makes it possible to obtain a polarizing plate protective resin film having good antistatic performance.

Further, the coefficient of kinetic friction of the surface of the film containing more fine particles than the average content of the whole resin film is preferably 0.40 or less, more preferably 0.35 or less, .30 or less, and most preferably 0.25 or less. The dynamic friction coefficient is preferably as low as possible, but the lower limit is about 0.10. The dynamic friction coefficient can be easily measured using a steel ball according to a method defined by JIS or ASTM.

In the present invention, the total thickness of the resin film is 100 μm or less. The film thickness is more preferably 30
６０60 μm, an antistatic agent, and other additives,
For example, by employing a fine particle matting agent, a plasticizer, a UV absorber or the like according to the present invention, even in a thin film having a thickness of 30 to 60 μm, the film has sufficient strength and does not have the above-mentioned disadvantages. Further, a thin resin film having an antistatic function suitable for a polarizing plate protective resin film used in a liquid crystal display device, which hardly wrinkles even in subsequent handling, can be obtained.

The polarizing plate using the resin film of the present invention as a protective film for a polarizing plate can be used for various liquid crystal cells. For example, TN or STN type liquid crystal, I
It can be used for PS (in-play switching) type liquid crystal and vertical alignment (VA) type liquid crystal display. When used as a protective film for a polarizing plate of a liquid crystal cell, disturbance of liquid crystal and adhesion of dust when the cover sheet is peeled can be suppressed.

[0180]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 The following composition was prepared.

<< Preparation of Dope >> (Dope 1) Cellulose triacetate (average degree of oxidation: 61.0%) 1000 g Triphenyl phosphate 80 g Ethylphthalylethyl glycolate 40 g Ti-326 (UV absorber: Ciba Specialty Chemical Co., Ltd.) )) 3 g Ti-109 (UV absorber: Ciba Specialty Chemical Co., Ltd.) 5 g Ti-171 (UV absorber: Ciba Specialty Chemical Co., Ltd.) 5 g Methylene chloride 4300 g Methanol 900 g (Dope 2) Cellulose acetate propio Nate 1000 g Triphenyl phosphate 80 g Ethylphthalylethyl glycolate 40 g Ti-326 (UV absorber: Ciba Specialty Chemical Co., Ltd.) 3 g Ti-109 (UV absorber: Ciba Specialty) Mical Co., Ltd.) 5 g Ti-171 (UV absorber: Ciba Specialty Chemical Co., Ltd.) 5 g Methylene chloride 4300 g Methanol 900 g (Dope 3) Cellulose triacetate (average degree of oxidation: 61.0%) 1000 g Triphenyl phosphate 80 g Ethyl Phthalylethyl glycolate 40 g Antistatic agent dispersion 1 * 320 g Methylene chloride 4300 g Methanol 600 g * Antistatic agent dispersion 1 Methylene chloride 300 g Methanol 450 g Conductive polymer resin (P-1) (0.1 to 0.3 μm particles) 250g (Surface resistivity: 1 × 10 ⁶ Ω)

[0183]

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(Dope 4) Cellulose triacetate (average degree of oxidation 61.0%) 1000 g Triphenyl phosphate 80 g Ethyl phthalyl ethyl glycolate 40 g Antistatic agent dispersion 2 * 200 g Methylene chloride 4300 g Methanol 600 g * Antistatic agent dispersion 2 Methylene chloride 300 g Methanol 100 g Acetone 300 g Conductive SnO ₂ antimony composite fine particles 500 g (Mitsubishi Materials: primary particle diameter 0.015 nm, surface resistivity 1 × 10 ³ Ω) The above composition was dispersed for 2 hours using a sand mill. .

(Dope 5) Cellulose triacetate (average degree of oxidation: 61.0%) 1000 g Triphenyl phosphate 80 g Ethylphthalylethyl glycolate 40 g Antistatic agent dispersion 3 * 200 g Methylene chloride 4300 g Methanol 600 g * Antistatic agent dispersion 3 Methylene chloride 300 g Methanol 100 g Acetone 300 g Phosphoric acid derivative (P-2 shown below) 200 g Surface resistivity: 1 × 10 ⁸ Ω Stearyl alcohol 150 g

[0186]

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(Dope 6) Cellulose triacetate (average degree of oxidation: 61.0%) 1000 g Triphenyl phosphate 30 g Ethylphthalylethyl glycolate 10 g Antistatic agent dispersion liquid 1 (described above) 320 g Methylene chloride 4380 g Methanol 600 g (Dope 7) ) Cellulose triacetate (average degree of oxidation 61.0%) 1000 g Triphenyl phosphate 80 g Ethylphthalylethyl glycolate 40 g Methylene chloride 4300 g Methanol 900 g (dope 8) Cellulose acetate propionate 990 g Cellulose triacetate (average degree of oxidation 61.0%) 10 g triphenyl phosphate 30 g ethylphthalylethyl glycolate 10 g antistatic dispersion 1 320 g methylene chloride 4 380 g methanol 600 g (dope 9) cellulose triacetate (average degree of oxidation: 61.0%) 1000 g triphenyl phosphate 30 g ethylphthalylethyl glycolate 10 g methylene chloride 4300 g methanol 600 g fine particle dispersion (prescription below) 8 g (dope 10) cellulose acetate Propionate 990 g Cellulose triacetate (average degree of oxidation 61.0%) 10 g Triphenyl phosphate 30 g Ethyl phthalyl ethyl glycolate 10 g Methylene chloride 4300 g Methanol 600 g Fine particle dispersion (dosage below) 8 g (Dope 11) Triphenyl phosphate 20 g Ethyl Phthalylethyl glycolate 30 g Methyl acetate 4750 g Ethanol 50 g was cooled to -10 to -10 ° C. And cellulose triacetate synthesized from cotton linter (degree of acetylation 61.
0%) and 15 parts of cellulose triacetate (degree of acetylation: 61.0%) synthesized from wood pulp.
The solution was completely dissolved in an organic solvent during the heating to about 120 ° C., and 320 g of Antistatic Agent Dispersion 1 was added to the obtained cellulose ester organic solvent solution and stirred.

<Fine Particle Dispersion> Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 50 g (average primary particle diameter 12 nm, apparent specific gravity 100 g / l) Ethanol 450 g went.

(Dope 12) Dope 12 was prepared in the same manner as in Dope 1 except that triphenyl phosphate and ethylphthalylethyl glycolate were removed.

(Dope 13) A dope 13 was prepared in the same manner as in dope 3, except that triphenyl phosphate and ethyl phthalylethyl glycolate were removed.

(Dope 14) A fine particle dispersion 8 was added to the dope 3.
A dope 14 was prepared in the same manner except that g was added.

The above-mentioned dope composition was charged into a closed container, and was kept at 80 ° C. under pressure and completely dissolved with stirring. Using the combinations of dopes shown in Table 1, using the co-casting apparatus shown in FIG. 1, dopes A, B,
In the order of C, the film thickness after drying was 5 μm, 30 μm,
The dope was cast from the die slit of FIG. 2 so as to have a thickness of 5 μm. The solvent was evaporated on a stainless steel casting belt until the residual solvent amount became 25%, and the solvent was peeled off from the casting belt. Thereafter, drying is completed while transporting the drying zone with a roll, and the cellulose ester film samples 101 to 101 are dried.
119 was obtained. The surface in contact with the casting belt is referred to as surface b,
The other surface is defined as a surface.

Further, using a co-casting apparatus shown in FIG. 3, dopes were applied in order of A, B, C, and D on the casting belt from the bottom so that the dry film thickness became 5 μm, 30 μm, 5 μm, and 5 μm, respectively. Then, a dope was cast from slits of two dies to obtain a cellulose ester film sample 120 in the same manner.

As described above, the cellulose ester film sample Nos. 101-120 were obtained.

[0195]

[Table 1]

<< Comparative Sample No. 121 >>
o. 116 was coated with a wire bar at a concentration of 20 ml / m ² , dried and dried. 121.

(Antistatic Agent Coating Solution) Polymethyl methacrylate 0.5 g (weight average molecular weight 550,000, Tg 90 ° C.) Propylene glycol monomethyl ether 60 g Methyl ethyl ketone 16 g Ethyl lactate 5 g Methanol 8 g Conductive polymer resin (P-1) 0 .4 g Evaluation method The evaluation was performed on films 101 to 120 obtained as follows.

<Impedance> Yokogawa, Hewlett,
Precision LCR manufactured by Packard (hereinafter YHP)
Impedance at 20 Hz was measured using a combination of meters HP4284A and HP16451B. Specifically, using a precision LCR meter HP4284A connected to an HP16451B having two electrodes composed of parallel planes and a guard electrode, at 23 ° C. and 55 ° C.
It was measured under a% RH atmosphere. 3.8cm diameter of main electrode
(11.335 cm ² ).

<Surface Resistivity> A sample was heated at 23 ° C. and 55% RH.
, And measured using a Tera Ohm Meter Model VE-30 manufactured by Kawaguchi Electric Co., Ltd. The electrodes used for the measurement were two electrodes (the part in contact with the sample was 1
cm × 5 cm) were arranged in parallel at an interval of 1 cm, the sample was brought into contact with the electrode, and measured. The value obtained by doubling the measured value was defined as the surface resistivity Ω / cm ² .

<Dust Adhesion Test> The surface a of the film was brought close to the height of 1 cm for 10 seconds to the ash of tobacco, and adhesion of dust was observed.

○: No dust adhesion was observed at all △: Dust adhesion was slightly observed ×: Dust adhesion was significantly observed <Curl> A sample was taken 50 mm in width direction and 2 mm in longitudinal direction. Was used. The sample was left for 3 days in an atmosphere of 25 ° C. and 55% RH, and the curl degree was measured according to JIS-K76.
Performed according to Method A of 19-1988.

<Coefficient of Dynamic Friction> The dynamic friction coefficient was measured using steel balls in accordance with the method specified by JIS or ASTM.

<Adhesion> A test was conducted in accordance with the grid adhesion test method described in JIS D0202. Specifically, 11 cuts were made vertically and horizontally at 1 mm intervals on the film (coated) surface, and 100 grids of 1 mm square were formed. A cellophane tape was stuck thereon, peeled off quickly at an angle of 90 °, and the number of grids remaining without being peeled was set to m, and expressed as m / 100.

<Haze> T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd. was used in accordance with JIS K 7105.

<Alkali saponification treatment> Saponification step 2 mol / l-NaOH 60 ° C for 120 seconds Rinse step Water 30 ° C for 45 seconds Neutralization step 10% by mass HCl 30 ° C for 45 seconds Rinse step water 30 ° C for 45 seconds Saponification → Rinse → Neutralization → washing with water, followed by drying at 80 ° C.

<Polarizer Adhesive Property> A polarizer and a resin film were bonded to each other in the following steps to prepare a polarizing film.

An 18 cm × 5 cm optical film was
The sheets are placed on a glass plate with the surface b facing down.

A polarizer consisting of a uniaxially stretched polyvinyl alcohol dyed film of the same size as the resin film was placed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass.
Immerse for 2 seconds (both sides of polarizer).

The excess adhesive adhering to the above polarizer is gently removed, and placed on the above protective film sample, and another sample is laminated.

[0210] Excess adhesive and air bubbles are removed from the laminate of the polarizer and the resin film laminated as above with a hand roller, and the laminate is bonded. The pressure of the hand roller is 0.
2 to 0.3 MPa, and the speed was about 2 m / min.

The sample stuck in a dryer at 80 ° C. is left to dry for 2 minutes. <Adhesion: Initial adhesion> After bonding the resin film and the polarizer, the peelability was measured by hand, and the following three grades were evaluated based on the degree of occurrence of material destruction.

：: Material destruction occurs. Δ: Partial sample destruction occurs, but the area peeled between the optical film and the polarizing film is large. X: Peeled between the optical film and the polarizer. <Adhesiveness: Processability> The sheet was cut using a single blade, and the following three grades were evaluated based on the degree of floating of the adhesive surface.

：: There is no lifting of the bonding surface at all. Δ: The floating of the bonding surface occurs slightly. X: The lifting of the bonding surface occurs. <Blocking> A resin film sample (35 mm in width and 950 mm in length) is formed into a core having a diameter of 50 mm. The sample is wrapped six times with a load of 1 kg, and both ends of the sample are stuck together with double-sided tape (30 mm in width and 5 mm in length) so that the sample is not loosened. Remove the core and remove it at 23 ° C and 55% RH
After standing for 4 hours, place the sample on the electronic balance,
m, and the stress at that time is measured. Next, the sample is unwound, wound around one turn, and measured in the same manner. The blocking force of the sample was calculated by subtracting six times the stress when winding six times. (Unit: millinewton (mN)) <Process contamination> Resin film sample at 160 ° C, 10 ° C
Heat treatment for a minute, determine the amount of plasticizer dissipated from the sample,
The reduced amount was used as a substitute for process contamination evaluation. The amount of plasticizer dissipated was determined from the amount of the plasticizer before the heat treatment and the amount of the plasticizer after the heat treatment, and this was expressed in%. That is, the sample in which the amount of the plasticizer has been reduced a lot has a large process contamination.

The base was methylene chloride 85 ml /
Dissolve in 15 ml of ethanol.

5 ml of a solvent containing 25 mg of n-butyl palmitate as an internal standard substance is added.

Gas chromatography (Shimadzu GC-
7A), and the plasticizer was quantified.

<Bright spot foreign matter>
Place a resin film between the light plates, and shine light from one outside.
From the outside of the other polarizer using a microscope
25 times in 0) ^TwoForeign matter that shines and looks white through
Is measured over 10 places, and a total of 250 mm^TwoPer
, And this evaluation is repeated five times to obtain an average value.
The average value was used as the number of foreign substances.

<Retardation value> Automatic birefringence meter KO
Using a BRA-21DH (manufactured by KS Systems) under the environment of 23 ° C. and 55% RH, a wavelength of 590 n
It was measured by irradiating m light.

The above results are shown in Tables 2 and 3.

[0220]

[Table 2]

[0221]

[Table 3]

[0222]

[Table 4]

Example 2 By the method described in the example of JP-A-11-264982,
An in-plane switching mode (IPS) active liquid crystal display device was manufactured. However, the polarizing plate used was a polarizing plate manufactured by using the resin film of the sample 101 of Example 1 to which a polymer cover sheet made of polyethylene was attached to prevent abrasion. Example 1 containing no antistatic agent
As compared with the case of the polarizing plate using No. 116, the liquid crystal was not disturbed when the cover sheet was peeled off, and a favorable liquid crystal display with no dust attached was obtained.

[0224]

EFFECTS OF THE INVENTION A manufacturing process which is excellent in antistatic performance, hardly causes destruction of an antistatic layer in an alkali saponification step when used as a protective film for a polarizing plate, curl, aggregation and precipitation of additives, and hardly causes blocking. A thin resin film having high suitability and excellent properties as a protective film for a polarizing plate and a method for producing the same were obtained.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a resin film manufacturing apparatus capable of simultaneously casting a plurality of dopes.

FIG. 2 is a cross-sectional view of a co-casting die.

FIG. 3 is a view schematically showing a resin film manufacturing apparatus capable of simultaneously and continuously casting a plurality of dopes.

[Explanation of symbols]

 1a-1h Dope liquid tank 2a-2c, 2e-h In-line mixer 3a-3c Pump 4,14,24 Casting die 5 Drum 6 Casting belt 7 Roller 8 Resin film 9 Die slit 10,11a, 11b Die slit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Hagiwara 1 Konica Stock Company, Sakura-cho, Hino-shi, Tokyo In-house (72) Inventor Toshiaki Shibue 1 Konica Stock Company, 1 Sakura-cho, Hino-shi, Tokyo F-term (reference) 2H049 BA02 BB13 BB33 BB67 BC09 4F071 AA09 AA43 AB18 AB26 AB30 AD02 AE04 AE05 AE16 AF28Y AF31Y AF37Y AF38Y AF53Y AG09 AH12 AH19 BA02 BB02 BB08 BC01 BC12 4F207 AA01 AA24 AA04 AB07 AB01 AB33

Claims (30)

[Claims] 1. A resin film, wherein the concentration of the antistatic agent on at least one surface side is different from the average concentration of the antistatic agent in the entire resin film. 2. A resin film in which the concentration of the antistatic agent on at least one surface side is different from the average concentration of the antistatic agent in the entire resin film, the size of which is recognized in the polarization crossed Nicols state of 5 to 50 μm. Is 250mm in area
Is 200 or less per ^2, foreign matter sized to be recognized by the polarization crossed nicols exceeds 50μm area 250
A resin film characterized in that the number is substantially zero per mm ² . 3. The resin film according to claim 1, wherein a retardation value is 100 nm or less. 4. The resin film according to claim 1, further comprising a plasticizer. 5. The resin film according to claim 1, containing fine particles. 6. A resin film, wherein the concentration of the antistatic agent on at least one surface side is higher than the average concentration of the antistatic agent in the entire resin film. 7. A resin film wherein the concentration of the antistatic agent on both surface sides is higher than the average concentration of the antistatic agent in the entire resin film. 8. The concentration of the antistatic agent on one surface side is higher than the average concentration of the antistatic agent on the entire resin film, and the concentration of fine particles on the opposite surface side is higher than the average concentration of the fine particles on the entire resin film. A resin film characterized by the above-mentioned. 9. The concentration of the antistatic agent on one surface is higher than the average concentration of the antistatic agent on the entire film, and the concentration of the plasticizer on both surfaces is the average concentration of the plasticizer on the entire resin film. Resin film characterized in that it is less than 10. The concentration of an antistatic agent on one surface side,
A resin film, wherein the average concentration of the antistatic agent is higher than the entire film, and the content of the UV absorber on both surface sides is lower than the average concentration of the UV absorber throughout the film. 11. A resin film having a distribution of an antistatic agent in a thickness direction, wherein the resin film has a region having a low concentration of the antistatic agent outside a region having a high concentration of the antistatic agent. 12. The resin film according to claim 1, wherein the resin film is a cellulose ester film. 13. The thickness is 100 μm or less, and the absolute value of impedance at a frequency of 20 Hz is 4 × 10 ⁵
The resin film according to any one of claims 1 to 12, wherein the resin film has a resistance of Ω or more. 14. The method according to claim 1, wherein the thickness of the resin film is 100 μm or less, the absolute value of impedance at a frequency of 20 Hz is 4 × 10 ⁵ Ω or more, and the surface is a cellulose ester. Any one
Item 10. The resin film according to item 1. 15. The resin film according to claim 1, wherein the resin film has a surface specific resistance of 1 × 10 ¹² Ω / cm ² or less (23 ° C., 55% RH). 16. The antistatic agent has a surface specific resistance of 1 × 1.
The resin film according to any one of claims 1 to 15, wherein the resin film has a resistance of 0 ¹⁰ Ω or less. 17. The resin film according to any one of claims 1 to 16, wherein a plurality of solutions having different additive compositions or concentrations are simultaneously extruded and cast from a die slit onto a casting support. A method for producing a resin film. 18. A method for producing a resin film, in which a plurality of solutions having different concentrations of an antistatic agent are simultaneously extruded from a die slit to a casting support and cast, and the concentration of the antistatic agent on the casting support side of the resin film. Is higher than the average concentration of the antistatic agent in the entire resin film. 19. A method for producing a resin film in which a plurality of solutions having different concentrations of an antistatic agent are simultaneously extruded and cast from a die slit onto a support for casting, wherein the solution having a higher concentration of the antistatic agent is disposed on the surface side of the solution having a higher concentration of the antistatic agent. A method for producing a resin film, comprising casting a solution having a lower concentration of an antistatic agent than a solution. 20. A method for producing a resin film in which a plurality of solutions having different additive compositions or concentrations are simultaneously extruded and cast from a die slit to a casting support, wherein the antistatic agent on the casting support side of the resin film is used. A method for producing a resin film, wherein the concentration is higher than the average concentration of the whole resin film, and the concentration of fine particles on the surface side opposite to the casting support is higher than the average concentration of fine particles in the whole resin film. 21. A plurality of solutions having different additive compositions or concentrations are laminated from a plurality of casting ports provided at intervals so that a certain degree of drying can proceed before reaching the next casting port. A method for producing a resin film, comprising producing the resin film according to any one of claims 1 to 16. 22. A plurality of solutions having different additive compositions or concentrations are laminated from a plurality of casting ports provided at intervals so that a certain degree of drying can proceed before reaching the next casting port. A method for producing a resin film, comprising: first casting a solution containing an antistatic agent. 23. A plurality of solutions having different additive compositions or concentrations are laminated from a plurality of casting ports provided at intervals so that a certain degree of drying can proceed before reaching the next casting port. A method for producing a resin film, comprising: casting a solution containing an antistatic agent and then casting a solution containing fine particles. 24. A method for producing a resin film in which a solution is extruded and cast from a die slit onto a casting support,
A method for producing a resin film, wherein the absolute value of the impedance at a frequency of 20 Hz of the resin film is 4 × 10 ⁵ Ω or more. 25. A method for producing a resin film in which a plurality of solutions having different additive compositions or concentrations are simultaneously extruded from a die slit onto a casting support and cast, wherein the absolute value of the impedance of the resin film at a frequency of 20 Hz is 4 ×. A method for producing a resin film, wherein the resin film has a resistivity of 10 ⁵ Ω or more. 26. In a resin film produced by simultaneously extruding and casting a plurality of solutions having different additive compositions or concentrations from a die slit onto a casting support, the absolute value of the impedance at a frequency of 20 Hz of the resin film is 4%. × 10 ⁵ Ω or more, and a friction coefficient of at least one surface is 0.40 or less. 27. The method for producing a resin film according to claim 24, wherein the curl degree at 23 ° C. and 55% RH is −10 or more and +10 or less. 28. A method in which a plurality of solutions having different additive compositions or concentrations are simultaneously extruded and cast from a die slit onto a casting support to form a resin film. A method for producing a resin film, wherein the absolute value of impedance at 20 Hz is 4 × 10 ⁵ Ω or more. 29. Any one of claims 1 to 16 and 26.
The resin film according to any one of claims to 17, or the resin film according to claim 17 to 25, 27.
29. A polarizing plate, characterized in that the resin film manufactured by the manufacturing method according to any one of items 28 and 28 is used as a protective film for a polarizing plate. 30. A liquid crystal display device using the polarizing plate according to claim 29.