JP2001002799A - Cellulose ester film, its production and protective film for polarizing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain microparticles slightly causing the occurrence of reaggregation when added to a dope at the time of preparing a cellulose ester film, and to provide a method for adding the microparticles by which the occurrence of the reaggregation of the microparticles is reduced. SOLUTION: This cellulose ester film comprises microparticles having (1) 2-20C alkyl groups or (2) aryl groups on the surface. (3) A cellulose ester is produced by mixing a dispersion obtained by predispersing the microparticles in a solvent with a mixture liquid of a solvent with a cellulose ester, mixing the resultant liquid containing the microparticles added thereto with a dope prepared by dissolving the cellulose ester in a solvent, casting the prepared dope onto a support and drying the cast dope.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose ester film suitable for use as a protective film for a polarizing plate, especially for a large screen, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the development of notebook personal computers has been progressing toward thinner and lighter and larger screens. Along with this, there is an increasing demand for a protective film for a liquid crystal polarizing plate to be thinner and to have a larger screen. Generally, a cellulose triacetate film is widely used as a protective film for a polarizing plate.

A cellulose triacetate film is disclosed in JP-A-62-37113 and JP-A-61-94 in order to improve the slipperiness (blocking resistance) and the scratch resistance.
It is known that various particles and the like are contained or coated as described in Japanese Patent No. 725 and the like.

[0004]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 7-11055
In order to improve the aggregation of the fine particles contained for the above-mentioned purpose, Japanese Patent Application Laid-Open Publication No. H11-15064 proposes an addition method using particles having a methyl group on the surface. However, it was found that this method was insufficient as a polarizing plate protective film corresponding to a large screen. In other words, in the production method described in this publication, the fine particles having a methyl group on the surface are dispersed in a solvent, mixed with the dope, and then formed into a film. In the production method, the fine particles dispersed in the solvent are re-aggregated when mixed with the dope. I knew it would. In another method described in this publication, a solvent and cellulose triacetate are used in a production method in which fine particles having a methyl group on the surface are dispersed in a mixed solution of a solvent and cellulose triacetate, mixed with a dope, and then formed into a film. It was found that the dispersion of the fine particles could not be sufficiently performed in the mixed solution of (1), and aggregation remained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide fine particles which are less likely to re-aggregate when added to a dope, and to reduce the occurrence of re-aggregation of the fine particles. To provide a method for adding the compound.

[0006]

The object of the present invention is to provide a cellulose ester film containing fine particles having an alkyl group having 2 to 20 carbon atoms on the surface, a cellulose ester film containing fine particles having an aryl group on the surface, A dispersion liquid obtained by previously dispersing fine particles in a solvent, a fine particle additive solution obtained by mixing the mixed solution with a solvent and a cellulose ester, and a dope prepared by dissolving the cellulose ester in a solvent are mixed with a support. A method for producing a cellulose ester that is cast on and then dried, a cellulose ester film produced by this method, fine particles contained therein, fine silica particles whose surface is modified with silicone oil, fine particles of spherical monodisperse silica, or Being fine particles of polymethyl methacrylate, wherein the fine particles contain silicon atoms. Be made of a compound that, the film thickness of the film is 30 to 60 m, it is a protective film for polarizing plate, and particle size 30μm or more aggregated particles contained ten / m
^{At least two} cellulose ester films.

Hereinafter, the present invention will be described in detail.

The cellulose ester used in the present invention is preferably a lower fatty acid ester.

The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like are preferred examples of the lower fatty acid ester of cellulose. No.

In addition to the above, Japanese Patent Application Laid-Open No. H10-458
04, 08-231761, U.S. Pat. No. 2,31
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 them, a lower fatty acid ester of cellulose which is particularly preferably used is cellulose triacetate. Furthermore, from the viewpoint of base strength, the polymerization degree is particularly preferably 250 to
400, the amount of bound acetic acid is preferably 54 to 62.5%, more preferably, the amount of bound acetic acid is 58 to 62.5%.
% Cellulose triacetate.

As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter and 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 a mixture of cellulose triacetate synthesized from wood pulp is used, the ratio of cellulose triacetate synthesized from cotton linter is 40% by weight or more,
It is preferable because the effect of the releasability becomes remarkable, more preferably 60% by weight or more, and it is most preferable to use it alone.

One feature of the present invention is to use fine particles having an alkyl group or an aryl group having 2 to 20 carbon atoms on the surface. The alkyl group preferably has 4 to 12 carbon atoms, and more preferably has 6 to 10 carbon atoms. The smaller the carbon number, the better the dispersibility, and the larger the carbon number, the less the re-aggregation when mixed with the dope.

The surface used in the present invention has 2 to 20 carbon atoms.
Examples of inorganic compounds among the materials of the fine particles having an alkyl group and the fine particles having an aryl group include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, and calcined silica. Mention may be made of calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Silicon dioxide, titanium dioxide and zirconium oxide are preferred,
Among them, compounds containing a silicon atom, particularly silicon dioxide, are preferred. Fine particles of silicon dioxide are commercially available under the trade names of Aerosil 130, Aerosil 200, Aerosil 300 (all manufactured by Nippon Aerosil Co., Ltd.). In addition, silica fine particles whose surfaces are modified with silicone oil and spherical monodispersed silica fine particles are also preferably used.

The fine particles of an inorganic compound having an alkyl group having 2 to 20 carbon atoms on the surface can be obtained, for example, by treating the fine particles of silicon oxide with octylsilane. Further, it is commercially available under the trade name of Aerosil R805 having an octyl group on the surface (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

The fine particles of the inorganic compound having a phenyl group on the surface can be obtained, for example, by treating the fine particles of silicon oxide with trichlorophenylsilane.

Among the materials for the fine particles having an alkyl group having 2 to 20 carbon atoms on the surface or the fine particles having a phenyl group, examples of the polymer include silicone resin, fluorine resin and acrylic resin. Methacrylate is preferred.

As described above, the compound is preferably a compound containing silicon, particularly preferably silicon dioxide or a silicone resin having a three-dimensional network structure.
Silicon dioxide is most preferred.

These fine particles are preferably used in an amount of 0.005 to 0.3% by weight, more preferably 0.01 to 0.1% by weight, based on the cellulose ester.

Next, the method for adding fine particles according to the present invention includes the following methods.

(Addition method A) After stirring and mixing the solvent and the fine particles, the mixture is dispersed with a dispersing machine such as Menton-Gawley. This is used as a fine particle dispersion. The fine particle dispersion is added to the dope and stirred.

(Addition method B) After stirring and mixing the solvent and the fine particles, the mixture is dispersed with a disperser such as Menton-Gawley. This is used as a fine particle dispersion. Separately, a small amount of cellulose ester is added to a solvent and dissolved by stirring. The fine particle dispersion is added thereto and stirred. This is used as a fine particle addition liquid. The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

(Addition method C) A small amount of cellulose ester is added to a solvent and dissolved by stirring. Fine particles are added to the mixture and dispersed with a disperser such as Menton-Gawley. This is used as a fine particle addition liquid. The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

The addition method A is excellent in dispersibility of fine particles,
When mixed with the dope, reaggregation of the fine particles may occur. The addition method B is excellent in dispersibility of the fine particles, and is mixed with a solution in which a small amount of a cellulose ester is dissolved to form a liquid for adding the fine particles. This is a preferred addition method. In addition method C, the fine particles are added to a liquid in which a small amount of cellulose ester is dissolved and then dispersed, so that the dispersibility of the fine particles may slightly deteriorate.

In any case, by using the fine particles according to the present invention or using the method of adding fine particles according to the present invention,
10 particles / m ² of aggregated particles having a particle size of 30 μm or more
The following cellulose ester film having extremely excellent dispersibility of fine particles can be obtained.

The cellulose ester film of the present invention 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. In the phthalate ester system, diethyl phthalate,
In the glycolic acid ester system such as dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate,
It is preferable to use methylphthalylethyl glycolate, butylphthalylbutyl glycolate or the like alone or in combination. 50% by weight of phosphate plasticizer
The following are preferable because they hardly cause hydrolysis of the cellulose ester film and are excellent in durability. It is more preferable that the ratio of the phosphate plasticizer is smaller, and it is particularly preferable to use only the phthalate or glycolate plasticizer.

As the plasticizer preferably used in the present invention, a plasticizer having a freezing point of 20 ° C. or less is preferable,
The temperature is not particularly limited as long as it is not more than ° C, and can be selected from the above plasticizers. For example, tricresyl phosphate,
Examples thereof include cresyl diphenyl phosphate, tributyl phosphate, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate. It is preferable to use these plasticizers alone or in combination. Here, the true freezing point described in the Dictionary of Chemistry published by Kyoritsu Shuppan Co., Ltd. is defined as the freezing point.

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 weight is preferred. For a liquid crystal display member, the content is more preferably 1 to 10% by weight, particularly preferably 3 to 7% by weight, from the viewpoint of dimensional stability.

The content of the plasticizer having a freezing point of 20 ° C. or less with respect to the cellulose ester is preferably 1% by weight to 10% by weight, more preferably 3% by weight to 7% by weight.
It is preferable that the ratio of the plasticizer having a freezing point of 20 ° 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 plasticizer is a plasticizer having a freezing point of 20 ° C. or lower.

It is preferable to use a plasticizer having a freezing point of 20 ° C. or less in a proportion of 1% by weight or more based on the cellulose ester, since the flexibility of the cellulose ester film is improved and the processability is excellent. Use of a plasticizer having a temperature of 14 ° C. or lower is preferred because the processability is further improved. In addition, workability is when slitting or punching the base film or liquid crystal display member.If the workability is poor, the cut surface becomes saw-toothed, chips are generated, and it adheres to the product and becomes a defect. Not preferred.

Further, an ultraviolet absorber may be contained. Specific examples of the ultraviolet absorber include, for example, oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and inorganic powders. UV absorbers are preferably used. Specific examples are shown below, 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) -5-chlorobenzotriazole 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-benzotriazole- 2
-Yl) phenol) UV-7: 2,4-dihydroxybenzophenone UV-8: 2,2'-dihydroxy-4-methoxybenzophenone UV-9: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-10: Bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane) The above-mentioned ultraviolet absorber preferably used in the present invention has high transparency and is excellent in an effect of preventing deterioration of a polarizing plate or a liquid crystal element. UV absorbers and benzophenone UV absorbers are preferred, and benzotriazole UV absorbers with less unnecessary coloring are particularly preferred.

As a method of adding the ultraviolet absorber, the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride, or dioxolane and then added to the dope.
Alternatively, it may be added directly into the dope composition. For those that do not dissolve in organic solvents such as inorganic powders, use a dissolver or sand mill in the organic solvent and cellulose ester,
Disperse and add to dope.

The amount of the ultraviolet absorber used is not uniform depending on the kind of the compound and the conditions of use, but is usually preferably 0.2 g to 2.0 g, and more preferably 0.4 g to 1.5 g per 1 m ² of the cellulose ester film. Is more preferred, and 0.6 g
~ 1.0 g is particularly preferred.

The cellulose ester film of the present invention comprises
It is preferably used for a liquid crystal display member. The liquid crystal display member is a member used for a liquid crystal display device, and includes, for example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflector, a viewing angle improving film, an antiglare film, a non-reflective film, and charging. Prevention films and the like. Among the above,
In a polarizing plate and a protective film for a polarizing plate, which have strict requirements for dimensional stability, the cellulose ester film of the present invention is particularly preferably used.

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

In place of the alkali treatment, JP-A-6-949
No. 15, 6-118232 may be used.

The polarizing film, which is a main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction, and a typical polarizing film currently known is a polyvinyl alcohol-based polarizing film. Are dyed polyvinyl alcohol-based films with iodine and dyed with dichroic dyes. These are formed by forming a film of an aqueous polyvinyl alcohol solution and uniaxially stretching and dyeing the film, or dyeing the film and then uniaxially stretching the film, and then preferably performing a durability treatment with a boron compound. A transparent plastic film, which is a protective film for a polarizing plate of the present invention, is laminated on the surface of the polarizing film to form a polarizing plate.

The method for producing the cellulose ester film of the present invention will be described.

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). Of course, other additives can be added as needed. The concentration of the cellulose ester in the dope solution is 10 to 30% by weight.
And more preferably 18 to 20% by weight.

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 70 to 95% by weight for the good solvent and 30 to 5% by weight for the poor solvent.

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

As a method for dissolving the cellulose ester at the time of preparing the dope solution, a general method can be used, but a preferable method is to mix the cellulose ester with a poor solvent, wet or swell, 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 mass undissolved substance called gel or mamako, More preferred.

In the present invention, the type of the pressure vessel used for dissolving the cellulose ester is not particularly limited, as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. For the pressurized container, other instruments such as a pressure gauge and a thermometer are appropriately arranged. Pressurization may be performed by a method of injecting 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 in the range of not less than the boiling point of the solvent used and not boiling the solvent, and is preferably set in the range of, for example, 40 ° C. or more, 50 to 110 ° C. . The pressure is adjusted at the set temperature so that the solvent does not boil.

After the dissolution, it is taken out of the container while cooling, or is taken out of the container by a pump or the like, and cooled with a heat exchanger or the like, and is provided 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.

In the present invention, a dope solution in which a cellulose ester is dissolved in a solvent, and a solution in which a small amount of a cellulose ester is dissolved in fine particles and an ultraviolet absorber are added and mixed in-line. (Casting step), heating to remove a part of the solvent (drying step on the support), then peeling off the support, drying the peeled film (film drying step), and producing the cellulose of the present invention. An ester film is obtained.

As the support in the casting step, a support in which a belt-shaped or drum-shaped stainless steel is mirror-finished is preferably used. 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 separation time can be increased, and it is more preferable to cast on a support at 5 to 15 ° C. The peeling limit time is the limit of the casting speed at which a transparent and flat good film can be continuously obtained.
The time during which the cast dope remains on the support. 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 10 to 55 ° C., the temperature of the solution is 25 to 60 ° C.
Further, the temperature of the solution is preferably higher than the temperature of the support by 0 ° C. or more, and more preferably 5 ° C. or more. The solution temperature and the support temperature are preferably higher as the drying speed of the solvent can be increased, but if the temperature is too high, foaming or
Flatness may be deteriorated.

A more preferred range of the temperature of the support is 20
~ 40 ° C, a more preferred range of solution temperature is 35-45.
° C.

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 = (weight before heat treatment-weight after heat treatment) × 100 / (weight after heat treatment)% The heat treatment for measuring the amount of residual solvent means that the film is heated at 115 ° C. This indicates that heat treatment is performed for one hour.

The peeling force at the time of peeling the film from the support is usually 20 to 25 kg / m. However, when the cellulose ester film is thinned, wrinkles are likely to be formed at the time of peeling. , Minimum tension that can be peeled ~
Peeling is preferably performed at 17 kg / m, more preferably at a minimum tension of 14 kg / m.

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

In the film drying step, a method of drying while transporting a film by a roll suspension 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 in a place where the amount of the residual solvent is large immediately after being peeled 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.

If the cellulose ester film is too thin, the strength of the polarizing plate as a protective film is insufficient.
The dimensional stability of the polarizing plate and the storage stability under wet heat deteriorate.
When the film thickness is large, the thickness of the polarizing plate becomes large, and it is difficult to reduce the thickness of the liquid crystal display. The film thickness of the cellulose ester film satisfying both requirements is 20 to 60 μm, preferably 30 to 60 μm.
５０50 μm, more preferably 35-45 μm, and most preferably 40 μm.

[0060]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Each sample was prepared as described below.

Sample 1 (Preparation of Dope Solution) 100 parts by weight of cellulose triacetate 5 parts by weight of ethylphthalylethyl glycolate 2- (2-hydroxy-3-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole 1 part by weight Methylene chloride 475 parts by weight Ethanol 50 parts by weight The above was charged into a closed container, heated, stirred, completely dissolved and filtered to prepare a dope solution.

(Preparation of Fine Particle Dispersion A) Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd.) 10 parts by weight Ethanol 90 parts by weight The above components were sufficiently stirred and mixed with a dissolver, and then dispersed with a Menton-Gawley.

(Preparation of Fine Particle Addition Liquid A) Fine Particle Dispersion A
To the mixture was added 90 parts by weight of methylene chloride, and the mixture was stirred to prepare a liquid containing fine particles.

To 100 parts by weight of the dope solution prepared above, 0.25 parts by weight of the fine particle addition liquid A was added, stirred, and filtered. Next, using a belt casting apparatus, the mixed liquid of the dope and the fine particle addition liquid A was heated to a temperature of 33 ° C. and 1500 ° C.
It was uniformly cast on a stainless steel band support with a width of mm.
The solvent was evaporated on the stainless steel band support until the residual solvent amount became 25%, and peeled off from the stainless steel band support at a peeling tension of 13 kg / m. The peeled cellulose triacetate film was slit to 1300 mm, and then dried while being conveyed by a number of rolls through a drying zone.
m of cellulose triacetate film was obtained.

Sample 1 of the cellulose triacetate film was subjected to alkali saponification by the following method to produce a polarizing plate. The thickness of the completed polarizing plate was 120 μm. Compared to a general polarizing plate, a polarizing plate having a thickness of 2/3 thinner and lighter was manufactured.

(Alkaline saponification treatment) Saponification step 2N-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Neutralization step 10 wt% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Under the above conditions, cellulose triacetate film Was treated in the order of saponification → water washing → neutralization → water washing, and then dried at 80 ° C.

(Preparation of Polarizing Plate) A polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by weight of an aqueous solution containing 1 part by weight of iodine and 4 parts by weight of boric acid and stretched 6 times at 50 ° C. to form a polarizing film. Was. A cellulose triacetate film sample having been subjected to an alkali saponification treatment on both sides of the polarizing film was bonded to each other using a completely saponified 5% aqueous solution of polyvinyl alcohol as an adhesive to prepare a polarizing plate.

Sample 2 Silicon oxide fine particles Aerosil 200V (produced by Nippon Aerosil Co., Ltd.) were treated with trichlorophenylsilane to produce silicon oxide fine particles having a phenyl group on the surface. Sample 2 was prepared in the same manner except that the fine particles of Sample 1 were changed to the fine particles of silicon oxide having a phenyl group on the surface.

Sample 3 Sample 3 was prepared in the same manner except that the fine particles of Sample 1 were changed to Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.).

Sample 4 (Preparation of Fine Particle Addition Liquid B) Cellulose triacetate 6 parts by weight Methylene chloride 140 parts by weight The above was charged into a closed vessel, heated, stirred, completely dissolved, and filtered. 20 parts by weight of the fine particle dispersion liquid A used in Sample 1 was added thereto with stirring, and the mixture was further stirred for 30 minutes, followed by filtration to prepare a fine particle addition liquid B.

The fine particle additive liquid B was added at a ratio of 2 parts by weight to 100 parts by weight of the same dope liquid as that of the sample 1, and an in-line mixer (Toray static type in-tube mixer Hi-Mixe) was added.
r, SWJ) and filtered. Next, using a belt casting apparatus, a mixed solution of the dope and the fine particle addition liquid was uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm. On a stainless steel band support, the solvent was evaporated until the residual solvent amount was 25%, and the peel tension was 13 kg.
/ M from the stainless steel band support. The peeled cellulose triacetate film was slit to a width of 1300 mm, and then dried while being conveyed by a number of rolls in a drying zone. The slit was cut to a width of 1100 mm to obtain a cellulose triacetate film sample 4 having a film thickness of 40 μm.

Sample 5 The thickness of the cellulose triacetate film of Sample 4 was 8
Sample 5 was prepared in the same manner except that the thickness was changed to 0 μm.

Sample 6 Sample 6 was prepared in the same manner except that the fine particles of Sample 4 were changed to Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.).

Sample 7 Sample 7 was prepared in the same manner except that the fine particles of Sample 4 were changed to Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.).

Sample 8 Sample 8 was prepared in the same manner except that the fine particles of Sample 4 were changed to Aerosil R202 (manufactured by Nippon Aerosil Co., Ltd.).

Sample 9 Spherical monodispersed silica fine particles KE-P30
(Average primary particle diameter: 3.0 μm, manufactured by Nippon Shokubai Co., Ltd.), except that Sample 9 was prepared in the same manner.

Sample 10 The fine particles of Sample 4 were converted to polymethyl methacrylate fine particles MX.
-150 (average primary particle size 1.5 μm, Soken Kagaku Co., Ltd.)
Sample 10 was produced in the same manner except that the sample 10 was changed to

Sample 11 (Preparation of Fine Particle Dispersion C) Cellulose triacetate 3 parts by weight Methylene chloride 80 parts by weight Ethanol 20 parts by weight The above was put into a closed vessel, heated, stirred, completely dissolved, and filtered. To this was added 0.5 parts by weight of fine particles of silicon dioxide Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.), and the mixture was dispersed with a disperser, filtered, and filtered to obtain a fine particle dispersion C.
Was prepared.

Sample 11 was prepared in the same manner as in Sample 4, except that the fine particle dispersion C was added in a ratio of 2.7 parts by weight to 100 parts by weight of the dope solution in place of the fine particle addition liquid B of Sample 4. .

Sample 12 Sample 12 was prepared in the same manner except that the fine particle addition liquid A of Sample 1 was not added.

(Measurement of Average Particle Diameter of Dispersed Particles) The particles were observed with a scanning electron microscope (3000 times magnification), and the diameter of a circle circumscribing the particles was defined as the particle diameter. Also, 100 particles were observed at different locations, and the average value was defined as the average particle size.

(Measurement of Dynamic Friction Coefficient) The dynamic friction coefficient (μ) between the front and back surfaces of the film was determined according to JIS-K-7125.
According to (1987), the film was cut out so that the front and back surfaces of the film were in contact with each other, a 200 g weight was placed on the film, the weight was pulled horizontally under the conditions of a sample moving speed of 100 mm / min, and a contact area of 80 mm × 200 mm. The load (F) was measured and determined by the following equation.

Dynamic friction coefficient = F (gf) / weight of weight (gf) (Measurement of haze)
It measured according to STM-D1003-52.

(Measurement of Agglomerate) 1 m ^{2 of the} obtained film
It was determined by counting the number of aggregates having a size of 30 μm or more present above.

Table 1 shows the above results.

[0087]

[Table 1]

[0088]

According to the present invention, it is possible to obtain a cellulose ester film which is excellent in mechanical strength and optical characteristics and is suitable for use as a polarizing plate protective film corresponding to a large screen.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuko Ueda, Konica Corporation, 1 Sakura-cho, Hino-shi, Tokyo In-house (72) Inventor Noriaki Tachibana, Konica Corporation, 1st Sakura-machi, Hino-shi, Tokyo F-term (reference ) 4F071 AA09 AA33 AA67 AB26 AD02 AH12 BB02 BC01 BC12 4F205 AA01 AA21 AA33 AB17 AB19 AC05 AG01 AH73 AR12 GA07 GB02 GC06 GE02 GE22 GF01 GF02 GF24 GN22 GN24 4J002 AB021 BD122 BG062 DJ03146 DJ36 DJ03006

Claims (11)

[Claims] 1. A cellulose ester film containing fine particles having an alkyl group having 2 to 20 carbon atoms on the surface. 2. A cellulose ester film comprising fine particles having an aryl group on the surface. 3. A dope prepared by dissolving cellulose ester in a solvent, and adding a fine particle addition liquid obtained by mixing a dispersion liquid in which fine particles are previously dispersed in a solvent with a mixed solution of a solvent and a cellulose ester. A method for producing a cellulose ester, comprising mixing, casting on a support, and then drying. 4. A cellulose ester film produced by the method according to claim 3. 5. The cellulose ester film according to claim 4, wherein the fine particles contained are silica fine particles whose surface is modified with silicone oil. 6. The cellulose ester film according to claim 4, wherein the fine particles contained are spherical monodispersed silica fine particles. 7. The cellulose ester film according to claim 4, wherein the fine particles contained are polymethyl methacrylate fine particles. 8. The cellulose ester film according to claim 1, wherein the fine particles are made of a compound containing a silicon atom. 9. The cellulose ester film according to claim 1, wherein the film thickness is 30 to 60 μm. 10. A protective film for a polarizing plate, comprising the cellulose ester film according to claim 1, 2, 4, 5, 6, 7, 8, or 9. 11. A cellulose ester film characterized in that the number of aggregated particles having a particle size of 30 μm or more is 10 particles / m ² or less.