JP2003012859A - Cellulose ester film, protected film for polarizing plate and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent polarizing plate, hard to generate a deposit or a volatile matter from a web in producing, a little in reservability and moisture permeability, highly low in elasticity even under high temperature and high humidity, and further without degradation of a polarizer even under high temperature and high wettability. SOLUTION: A cellulose ester film is formed by a film-production method by a solution-flow casting using a dope composed of the cellulose ester, an acrylic polymer and an organic solvent, wherein the acrylic polymer has a weight average molecular weight of 500 or more and below 10,000.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cellulose ester film used in a liquid crystal image display device, and further relates to a protective film for a polarizing plate and a polarizing plate using the same.

[0002]

2. Description of the Related Art Conventionally, a cellulose ester film has been used as a support for a silver halide photographic light-sensitive material. Recently, this cellulose ester film has been diverted as a protective film for a polarizing plate in a liquid crystal image display device or the like, but there is a demand in this field which is not found in silver halide photographic light-sensitive materials. On the other hand, similarly to the support of a silver halide photographic light-sensitive material, a cellulose ester film as a protective film for a polarizing plate also contains a plasticizer for imparting flexibility and hydrophobicity.

In recent years, developments have been made on thinning and weight reduction of information equipments equipped with liquid crystal image display devices such as notebook personal computers, car navigations, mobile phones and game machines.
Along with this, there is an increasing demand for thinner protective films for polarizing plates used in liquid crystal image display devices. Therefore, the protective film for the polarizing plate tends to be extremely thinned as compared with the cellulose ester film as the support for the silver halide photographic light-sensitive material. By reducing the thickness of the film, the moisture permeability increases, and the function of the liquid crystal image display device deteriorates in a high humidity environment, particularly in a high temperature and high humidity environment.

Further, the plasticizer is a solution cast film forming method for forming a cellulose ester film, and the web in which the dope is cast on an endless metal support that moves infinitely has a thickness of the plasticizer during drying. Direction, the distribution in the web becomes non-uniform, and the plasticizer deposits on the web surface, or evaporates or volatilizes and condenses and accumulates on the walls of the film forming equipment, which then become droplets. And dirty the web and rolls. If the cellulose ester film is simply thinned, the moisture permeability will increase and it will not be possible to sufficiently block moisture from the outside, so it was used to bond the polarizer or the polarizer and the cellulose ester film after forming the polarizing plate. The adhesive sometimes deteriorated. As a measure against this, if the amount of plasticizer is increased by the amount of thinning, precipitation of the plasticizer on the surface of the cellulose ester film will become even more intense simply by increasing the amount of plasticizer, and it will be used as a support for silver halide photographic light-sensitive materials. It was found to cause new problems beyond what had been expressed. In the environment of high temperature and high humidity, the property that the mass of the film is reduced due to precipitation and volatilization of additives such as plasticizers outside the film is called retention property. The function of the image display device is deteriorated.

Further, by increasing the amount of the plasticizer, the glass transition point (hereinafter sometimes referred to as Tg) of the cellulose ester film is further lowered, and by softening, the dimensional stability (shrinkage rate, moisture absorption) of the cellulose ester film is decreased. There is a problem that the expansion coefficient and the thermal expansion coefficient are deteriorated (increased).

As a countermeasure against these problems, a technique has been proposed in which a polymer such as polyester, polyester ether, or polyurethane ether is contained, or a polymer plasticizer is used in combination with a low molecular plasticizer. For example,
JP-B-47-760, JP-B-43-16305, JP-A-5-97073, and U.S. Pat. No. 3,054,67.
No. 3 and No. 3,277,031 can be mentioned. Further, US Pat. No. 3,277,032 proposes a technique in which methyl acrylate is polymerized in the presence of cellulose ester to be contained. But,
When such a polymer plasticizer is used in a cellulose ester dope, a web is being dried, or after film formation, the cellulose ester and the polymer plasticizer are phase-separated to reduce transparency, increase moisture permeation, and make the film uniform. It was found that there is a problem that the film does not shrink or the expansion ratio deteriorates.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object thereof is a cellulose ester film in which precipitates or volatiles are hardly generated from a web during production. To provide. Further, a second object is to provide a cellulose ester film having a low moisture permeability, a very small stretchability even under a high temperature and high humidity environment, and an excellent holding property, and a protective film for a polarizing plate using the same. . A third object is to provide a good-quality polarizing plate that does not deteriorate the polarizer even in a hot and humid state.

[0008]

The present invention has the following constitution.

(1) A cellulose ester film formed by a solution casting method using a dope containing a cellulose ester, a polymer obtained by polymerizing an ethylenically unsaturated monomer, and an organic solvent, A cellulose ester film, wherein the weight average molecular weight of the polymer obtained by polymerizing an ethylenically unsaturated monomer is 500 or more and less than 10,000.

(2) A cellulose ester film formed by a solution casting method using a dope containing a cellulose ester, an acrylic polymer and an organic solvent, wherein the acrylic polymer has a weight average molecular weight of 500 or more. A cellulose ester film which is less than 10,000.

(3) The cellulose ester film according to (2), wherein the acrylic polymer has a weight average molecular weight of 500 to 5,000.

(4) The cellulose ester film according to (2) or (3), wherein the acrylic polymer has 30% by mass or more of acrylic acid methyl ester monomer units.

(5) The cellulose ester film according to (4), wherein the acrylic polymer has 40% by mass or more of a methacrylic acid methyl ester monomer unit.

(6) The acrylic polymer contains 2 to 20% by mass of an acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group, according to any one of (2) to (5). Cellulose ester film.

(7) The cellulose ester film according to any one of (2) to (6), wherein the acrylic polymer has a hydroxyl group on at least one terminal of the main chain.

(8) A cellulose ester film formed by a solution casting film formation method using a dope containing a cellulose ester, an acrylic polymer having an aromatic ring as a side chain and an organic solvent, wherein the aromatic ring is A cellulose ester film having a weight average molecular weight of an acrylic polymer having a side chain of 500 or more and less than 10,000.

(9) The acrylic polymer having an aromatic ring as a side chain has a weight average molecular weight of 500 to 5,000.
The cellulose ester film according to (8), which is

(10) The acrylic polymer having an aromatic ring as a side chain has 20 to 40% by mass of an acrylic acid ester monomer unit having an aromatic ring, and an acrylic acid methyl ester or methacrylic acid methyl ester monomer unit. 50-80 mass% is contained, The cellulose-ester film as described in (8) or (9) characterized by the above-mentioned.

(11) The acrylic polymer having an aromatic ring as a side chain contains 2 to 20% by mass of a hydroxyl group-containing acrylic acid or methacrylic acid ester monomer unit (8) to (10). The cellulose ester film according to any one of 1.

(12) The acrylic polymer having an aromatic ring as a side chain has a hydroxyl group on at least one terminal of the main chain, according to any one of (8) to (11). Cellulose ester film.

(13) A cellulose ester film formed by a solution casting method using a dope containing a cellulose ester, an acrylic polymer having a cyclohexyl group in its side chain and an organic solvent, wherein the cyclohexyl group is A cellulose ester film having a weight average molecular weight of an acrylic polymer having a side chain of 500 or more and less than 10,000.

(14) The acrylic polymer having a cyclohexyl group in its side chain has a weight average molecular weight of 500.
~ 5,000, The cellulose ester film as described in (13).

(15) The acrylic polymer having a cyclohexyl group in its side chain contains 20 to 40% by mass of an acrylic acid ester monomer unit having a cyclohexyl group.
And having 50 to 80% by mass of acrylic acid methyl ester or methacrylic acid methyl ester monomer units, (13) or (14).

(16) The acrylic polymer having a cyclohexyl group as a side chain contains 2 to 20% by mass of an acrylic acid or methacrylic acid ester unit having a hydroxyl group, according to (13) to (15). The cellulose ester film according to any one of items.

(17) The acrylic polymer having a cyclohexyl group as a side chain has a hydroxyl group at at least one terminal (13) to (16).
The cellulose ester film according to any one of 1.

(18) The film has a film thickness of 10 to 60 μm, and the water vapor permeability of the film in an atmosphere of high temperature and high humidity of 80 ± 5 ° C. and 90 ± 5% RH is 250 g / m ² · 24 h or less. The cellulose ester film according to any one of (1) to (17).

(19) The mass of the film in an atmosphere of normal temperature and normal humidity of 23 ± 3 ° C. and 55 ± 3% RH, and 80 ± 3
The rate of change (holding capacity) of the mass after standing for 50 hours in a high-temperature and high-humidity atmosphere of 90 ° C. and 90 ± 3% RH and then returning to the normal-temperature and normal-humidity atmosphere for 2 hours is 2 mass% or less. The cellulose ester film according to any one of (1) to (18), which is present.

(20) Any one of (1) to (19)
A protective film for a polarizing plate, characterized in that the surface of the cellulose ester film according to the item is saponified.

(21) A polarizing plate which is formed by laminating the protective film for polarizing plate according to (20) on at least one surface of a polarizer.

The present invention is described in detail below. First, a method for producing a cellulose ester film by the solution casting film forming method according to the present invention and materials used for the dope will be described.

[Materials Used for Dope] <Cellulose Ester> The cellulose ester useful in the cellulose ester film of the present invention has an acyl group substitution degree of 2.50 to 2.98 and an acyl group of acetyl group. It is at least one selected from a propionyl group and a butyryl group. Specifically, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate, cellulose butyrate, cellulose acetate propionate butyrate and the like can be mentioned, in the present invention, cellulose triacetate, cellulose Acetate propionate and cellulose acetate butyrate are preferred. When it contains an acetyl group, the substitution degree of the acetyl group is preferably 1.40 or more in order to maintain the mechanical properties. Cellulose ester is not particularly limited in its raw material cellulose, and cotton linter, wood pulp, kenaf and the like can be used. You may mix and use these. It is preferable to use a large amount of cellulose ester synthesized from cotton linter, which has good peelability from a belt or a drum, because the production efficiency is high. The ratio of the cellulose ester synthesized from cotton linter is 60% by mass or more, and the effect of releasability becomes remarkable, so 60% by mass or more is preferable, more preferably 85% by mass or more, and further, it may be used alone. Most preferred. The method for synthesizing the cellulose ester is not particularly limited, and for example, it can be synthesized by the method described in JP-A-10-45804. The method for measuring the degree of substitution of an acyl group is ASTM-
It can be measured by D817-96. The number average molecular weight of the cellulose ester is 70,000 in order to obtain preferable mechanical strength as a protective film for a polarizing plate.
To 300,000 is preferable, and 80,000 to 20 is more preferable
10,000 is preferable.

<Polymer> The dope used in the cellulose ester film of the present invention is mainly composed of a cellulose ester, a polymer (hereinafter, when simply referred to as a polymer, a polymer obtained by polymerizing an ethylenically unsaturated monomer, an acrylic polymer). The polymer, an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain are collectively referred to) and an organic solvent.

The polymer of the present invention has a weight average molecular weight of 50.
If it is from 0 to 10,000, the compatibility with the cellulose ester is good, and neither evaporation nor volatilization occurs during film formation. In particular, an acrylic polymer, an acrylic polymer having an aromatic ring as a side chain, or an acrylic polymer having a cyclohexyl group as a side chain, is preferably 50.
In the case of 0 to 5,000, in addition to the above, the cellulose ester film after film formation has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for a polarizing plate.

The polymer of the present invention has a weight average molecular weight of 50.
Since it is 0 or more and less than 10,000, it is considered to be present between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight by ordinary polymerization, and it is desirable to use a method that can make the molecular weight uniform by a method that does not increase the molecular weight so much. As such a polymerization method, a method using a peroxide polymerization initiator such as cumene peroxide or t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than usual polymerization, and a mercapto compound in addition to the polymerization initiator And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, a method using a polymerization initiator.
A compound having one thiol group and a secondary hydroxyl group as disclosed in 0-128911 or 2000-344823, or a method of bulk polymerization using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although all of them are preferably used in the present invention, the method described in the publication is particularly preferable.

The monomers as the monomer units constituting the polymer useful in the present invention are listed below, but the present invention is not limited thereto.

The ethylenically unsaturated monomer units constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer include: vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate,
Vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, benzoate. Vinyl acrylate, vinyl cinnamate, etc .; Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-,
i-, s-, t-), pentyl acrylate (n-, i)
-, S-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), Myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε
-Caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic Acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl and the like;
As the methacrylic acid ester, the above acrylic acid ester is changed to a methacrylic acid ester; as the unsaturated acid, for example, acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like can be mentioned.
The polymer composed of the above monomers may be a copolymer or a homopolymer, a homopolymer of vinyl ester,
Copolymers of vinyl esters, copolymers of vinyl esters with acrylic acid or methacrylic acid esters are preferred.

In the present invention, the term "acrylic polymer" (simply referred to as "acrylic polymer") refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring as a side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring. In addition, the acrylic polymer having a cyclohexyl group in the side chain is
It is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

Examples of acrylic acid ester monomers having no aromatic ring or cyclohexyl group include methyl acrylate, ethyl acrylate, propyl acrylate (i
-, N-), butyl acrylate (n-, i-, s-, t
-), Pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-),
Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid ( 2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), acrylic acid (2-ethoxyethyl) And the like, or those in which the above acrylic acid ester is changed to a methacrylic acid ester.

The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass. It is preferable to have the above. A homopolymer of methyl acrylate or methyl methacrylate is particularly preferable.

As the acrylic acid or methacrylic acid ester monomer having an aromatic ring, for example, phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), acrylic acid ( 2 or 3 or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o
Or m- or p-tolyl), benzyl acrylate, benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl), and the like, and benzyl acrylate, benzyl methacrylate, phenyl acrylate. Phenethyl methacrylate can be preferably used.

In the acrylic polymer having an aromatic ring as a side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit has 50 to 40% by mass. It is preferable to have 80 mass%. The polymer preferably has 2 to 20% by mass of a hydroxyl group-containing acrylic acid or methacrylic acid ester monomer unit.

Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate and acrylic acid (4-
Examples thereof include methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid (4-ethylcyclohexyl), and cyclohexyl acrylate and cyclohexyl methacrylate are preferably used. I can.

In the acrylic polymer having a cyclohexyl group in the side chain, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and 50 to 80% by mass. Further, it is preferable that the polymer has 2 to 20% by mass of a hydroxyl group-containing acrylic acid or methacrylic acid ester monomer unit.

The polymer obtained by polymerizing the above-mentioned ethylenically unsaturated monomer, the acrylic polymer, the acrylic polymer having an aromatic ring in the side chain, and the acrylic polymer having a cyclohexyl group in the side chain are each a cellulose ester. Excellent compatibility, excellent productivity without evaporation or volatilization, good retention as a protective film for polarizing plate, low moisture permeability, and excellent dimensional stability.

The acrylic acid or methacrylic acid ester monomer having a hydroxyl group of the present invention is not a homopolymer but a constitutional unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is 2 to 20 in the acrylic polymer.
It is preferable to contain it in mass%.

In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the above-mentioned monomer, but acrylic acid or methacrylic acid ester is preferable, and for example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3
-Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-
Examples thereof include p- (2-hydroxyethyl) phenyl, and those obtained by replacing these acrylic acids with methacrylic acid, and preferably 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.
Acrylic ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is 2 to 2 in the polymer.
It is preferable to contain 0% by mass, more preferably 2 to
It is 10% by mass.

The above-mentioned polymer containing 2 to 20% by mass of the above-mentioned hydroxyl group-containing monomer unit is, of course, excellent in compatibility with cellulose ester, retention, and dimensional stability, and has a small moisture permeability. In particular, the adhesiveness to a polarizer as a protective film for a polarizing plate is particularly excellent, and the durability of the polarizing plate is improved.

Further, in the present invention, it is preferable that at least one terminal of the main chain of the polymer has a hydroxyl group. The method of having a hydroxyl group at the terminal of the main chain is not particularly limited as long as it has a hydroxyl group at the terminal of the main chain, but radical polymerization having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method of using an initiator, a method of using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method of using a polymerization terminator having a hydroxyl group, a method of having a hydroxyl group at the terminal by living ionic polymerization, JP 2000-12
A compound having one thiol group and a secondary hydroxyl group as disclosed in Japanese Patent No. 8911 or 2000-344823, or obtained by a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. The method described in this publication is particularly preferable. The polymer produced by the method related to the description of this publication is commercially available as Actflow series manufactured by Soken Chemical Industry Co., Ltd. and can be preferably used.

The above-mentioned polymer having a hydroxyl group at the terminal and / or a polymer having a hydroxyl group at the side chain has the effect of remarkably improving the compatibility and transparency of the polymer in the present invention.

<Organic Solvent> Next, the organic solvent of the dope containing the cellulose ester, the polymer and the organic solvent of the present invention will be described.

Good solvents for cellulose esters are also generally good solvents for polymers, such as methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran,
1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3 -Difluoro-2-propanol,
1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3 3-pentafluoro-1-propanol, nitroethane, 2-
Pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, methylene chloride, bromopropane and the like can be mentioned, and methyl acetate, acetone and methylene chloride are preferably used. However, due to recent environmental problems, non-chlorine organic solvents tend to be preferable. Further, it is preferable to use a lower alcohol such as methanol, ethanol or butanol in combination with these organic solvents because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. Especially low boiling point,
Ethanol, which is less toxic, is preferred.

<Additives> In the dope used for forming the cellulose ester film of the present invention, a low molecular weight plasticizer, a low molecular weight ultraviolet absorber or a low molecular weight antioxidant which has been conventionally used is added. A cellulose ester dope composition containing a polymer, which is essentially free of an agent, is formed into a film. Therefore, a feature of the present invention is that the plasticizer and the ultraviolet absorber do not deposit or volatilize from the web. However, if necessary, a small amount of a low molecular weight plasticizer or a low molecular weight ultraviolet absorber may be supplementarily added to the extent that it does not precipitate. The low molecular weight plasticizer that can be supplementarily added in the present invention is not particularly limited, but a phosphoric acid ester plasticizer, a phthalic acid ester plasticizer, a glycolate plasticizer and the like can be preferably used. Phosphate ester plasticizers such as triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc.Phthalate ester plasticizers such as diethyl phthalate and dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, dibenzyl phthalate, glycolate plasticizers such as butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalate Ruethyl glycolate and the like can be preferably used. These plasticizers can be used alone or in combination of two or more.

In the present invention, the ultraviolet absorber that can be supplementarily added is not particularly limited.
Examples thereof include oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, etc., but benzotriazole-based compounds with little coloring are preferable. Benzotriazole-based UV absorbers and benzophenone-based UV absorbers having stability to light are preferable, and benzotriazole-based UV absorbers with less unnecessary coloring are particularly preferable. For example, TINUVIN 109, 171, 326, 3 manufactured by Ciba Specialty Chemicals.
27, 328 and the like can be preferably used. Also,
In the present invention, a polymer ultraviolet absorber using a commercially available product of an ethylenically unsaturated monomer having an ultraviolet absorbing group can be preferably used.
-Hydroxy-2- (2-benzotriazole) -4
-(2-methacryloyloxyethyl) benzene (UV absorber RUVA-93 manufactured by Otsuka Chemical Co., Ltd.), 1-hydroxy-2- (2-benzotriazole) -4- (2-
Acryloyloxyethyl) benzene can be mentioned. The weight average molecular weight of the polymeric ultraviolet absorber is preferably adjusted to that of the above-mentioned polymer. The low molecular weight ultraviolet absorber may be deposited on the web during film formation or volatilized like the plasticizer depending on the amount used, so the amount added is about 3 to 10% by mass.

Further, the cellulose ester film of the present invention may additionally contain an antioxidant, and a hindered phenol compound is preferably used as the antioxidant, and 2,6-dicarboxylic acid is preferably used. -T-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,3
5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4- Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-
2,4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, Tris- (3,5-di-
Examples thereof include t-butyl-4-hydroxybenzyl) -isocyanurate. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-
Bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, N, N'-bis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionyl] hydrazine-based metal deactivators and tris (2,4-di-)
A phosphorus-based processing stabilizer such as t-butylphenyl) phosphite may be used in combination. The addition amount of these compounds is 1 ppm to 1.0 by mass ratio with respect to the cellulose ester.
% Is preferable, and 10 to 1000 ppm is more preferable.

It is preferable that a fine particle matting agent is contained in the dope according to the present invention. The presence of the matting agent in the form of fine particles in the cellulose ester film as the protective film for polarizing plate after the film formation imparts appropriate slip and abrasion resistance. The fine matting agent is used by mixing and dispersing it in the cellulose ester dope. Examples of the particulate matting agent include inorganic substances such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. It is preferable to contain fine particles or crosslinked polymer fine particles. Of these, silicon dioxide is preferable because it can reduce the haze of the film.
The average particle diameter of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm, and the content thereof is 0.
005 to 0.3 mass% is preferable. In many cases, fine particles such as silicon dioxide are surface-treated with an organic substance, particularly a compound having a methyl group, but such a substance can reduce the haze of the film and is preferable in the present invention. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes (particularly methoxysilane), silazanes, siloxanes and the like. The larger the average particle size of the fine particles, the greater the matting effect, and the smaller the average particle size, the more excellent the transparency. Therefore, the average particle size of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to
It is 14 nm. It is preferable that these fine particles usually exist as an aggregate in the cellulose ester film and generate irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. As fine particles of silicon dioxide, Aerosil manufactured by Nippon Aerosil Co., Ltd.
IL) 200, 200V, 300, R972, R972
V, R974, R202, R812, OX50, TT6
00 and the like, preferably Aerosil R9
72, R972V, R974, R202, and R812. Two or more kinds of these matting agents may be used in combination. When two or more kinds are used in combination, they can be mixed and used at an arbitrary ratio. In this case, a matting agent having different average particle diameters or materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

[Production of Cellulose Ester Film by Solution Casting Film Forming Method] A method for forming a cellulose ester film by the solution casting film forming method according to the present invention will be described.

Dissolution step: a step of dissolving the cellulose ester, the polymer and additives with stirring in an organic solvent mainly composed of a good solvent for the cellulose ester (flakes) to form a dope, or the cellulose ester This is a step of forming a dope by mixing a polymer solution and an additive solution with the solution. To dissolve the cellulose ester, a method carried out under normal pressure, a method carried out below the boiling point of the main solvent,
Method of pressurizing above the boiling point of the main solvent, JP-A-9-95
544, 9-95557 or 9-95538.
Japanese Patent Laid-Open Publication No. 11-1999
Although various dissolution methods such as the method under high pressure as described in JP-A-21379 can be used, in the present invention, the method under pressure above the boiling point of the main solvent is particularly preferable. The concentration of cellulose ester in the dope is 10 to 35.
Mass% is preferred. Additives other than the matting agent are added to the dope during or after dissolution to dissolve it, and the dope is filtered through a filter medium, defoamed, and sent to the next step by a liquid feed pump.

Casting step: A casting position on a metal support such as an endless metal belt, for example, a stainless belt or a rotating metal drum, which feeds the dope to a pressure die through a pressure type quantitative gear pump and infinitely transfers it. In the second step, the dope is cast from the pressure die. It is preferable to use a pressure die that can adjust the slit shape of the die and can easily make the film thickness uniform. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film formation speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided to form multiple layers.

Solvent evaporation step: The web (the dope film is called the web after the dope is cast on the metal support) is heated on the metal support until the web can be peeled from the metal support. This is a step of evaporating the solvent. To evaporate the solvent, a method of blowing a wind from the web side and / or
Alternatively, there are a method of transferring heat from the back surface of the metal support by a liquid, a method of transferring heat from the front and back sides by radiant heat, and the like. A method of combining them is also preferable. In the case of rear surface liquid heat transfer, it is preferable to heat at a temperature not higher than the boiling point of the main solvent of the organic solvent used for the dope or the organic solvent having the lowest boiling point.

Peeling step: This is a step of peeling the web having the solvent evaporated on the metal support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount of the web at the time of peeling (the following formula) is too large, it is difficult to peel, or conversely if you peel it after drying it sufficiently on the metal support, part of the web may peel off in the middle .

As a method for increasing the film forming speed (the film forming speed can be increased by peeling while the residual solvent amount is as large as possible), there is a gel casting method (gel casting). There are a method of adding a poor solvent for cellulose ester into the dope, gelation after casting the dope, a method of lowering the temperature of the metal support and gelling. By gelling on the metal support to increase the strength of the film at the time of peeling, the peeling can be accelerated and the film forming speed can be increased. Drying of the web on the metal support can be peeled in the range of 5 to 150 mass% depending on the strength and weakness of the conditions, the length of the metal support, etc., but when peeling at a time when the residual solvent amount is larger, the web If is too soft, the flatness is deteriorated at the time of peeling, and cracks and vertical lines due to peeling tension are likely to occur, and the amount of residual solvent for peeling can be determined in consideration of economic speed and quality. Therefore, in the present invention, the temperature at the peeling position on the metal support is 10 to 40 ° C, preferably 15 to 3 ° C.
It is preferable that the temperature is 0 ° C. and the residual solvent amount of the web at the peeling position is 10 to 120% by mass. In the present invention, the peeling residual solvent amount can be represented by the following formula.

Amount of residual solvent (% by mass) = {(M−N) / N} × 100 Here, M is the mass of the web at any time, and N is the one of M when dried at 110 ° C. for 3 hours. Is the mass of.

In the present invention, the amount of residual solvent with respect to the entire width of the web is sometimes referred to as the average amount of residual solvent or the amount of residual solvent at the center, and the amount of residual solvent at both ends of the web is referred to as the amount of local residual solvent. There is also a case.

Drying and stretching process: After peeling, generally,
The web is dried using a drying device that conveys the web alternately through rolls arranged in a zigzag and / or a tenter device that clips and conveys both ends of the web with clips. As a drying means, hot air is generally blown on both sides of the web, but a microwave may be applied instead of the air to heat the web. Drying too rapidly tends to impair the flatness of the finished film. Throughout, the drying temperature is usually in the range of 40 to 250 ° C. The drying temperature, the amount of drying air and the drying time vary depending on the solvent used, and the drying conditions may be appropriately selected depending on the type and combination of the solvents used.

The thickness of the cellulose ester film of the present invention is the thinning of the polarizing plate used in the liquid crystal image display device,
The thickness is 10 to 150 μm, and preferably 35 to 85 μm in order to reduce the weight.

[Properties of Cellulose Ester Film Containing Polymer] Since the cellulose ester film of the present invention does not substantially contain a low molecular weight plasticizer, nothing deposits or volatilizes from the web being produced. It can be said to be an ideal film because it does not become dirty, and after it becomes a liquid crystal display device, it hardly precipitates or volatilizes from the film even in a high temperature and high humidity condition in a closed automobile.

<Holdability> High temperature and high humidity conditions (80 ± 3 ° C., 9
It is preferable that the holding property, which shows a change in mass due to precipitation or volatilization of a substance from the film in a high temperature and high humidity atmosphere of 0 ± 3% RH for 50 hours, is almost zero,
Due to the residual solvent in the film, some reduction in mass is unavoidable. The retention of the cellulose ester film of the present invention is 2.0% by mass or less, preferably 1.0%.
Or less, more preferably 0.5% or less.

<Dimensional Stability> The dimensional stability of the cellulose ester film subjected to the high temperature and high humidity as described above is also improved, and the dimensional change rate is smaller than that of the cellulose ester film containing no polymer of the present invention. The dimensional change rate of the cellulose ester film of the present invention is ± 0.1%
It is preferably within the range, more preferably ± 0.5%
Within, more preferably within ± 0.4%, particularly preferably within ± 0.3%.

<Moisture Permeability> The moisture permeability of the cellulose ester film containing the polymer of the present invention is JISZ 02.
According to the method described in No. 08, 80 ± 5 ℃, 90 ± 5% RH
The film thickness of the cellulose ester film is 10 to 10
When it is 60 μm, it is preferably 250 g / m ² · 24 h or less. The cellulose ester film of the present invention can achieve this value by containing the above polymer.

<Retardation> Since the cellulose ester film of the present invention contains a polymer,
It was also found that the retardation was improved without increasing the film thickness and showed excellent retardation.
Such a cellulose ester film is useful as a protective film for polarizing plates. The protective film for a polarizing plate may be saponified on the surface of a cellulose ester film as described below so as to improve the adhesiveness when it is attached to a polarizing film (polarizer).

The smaller the retardation R ₀ (nm) in the in-plane direction of the cellulose ester film as the protective film for a polarizing plate of the present invention, the better. It is preferably 100 nm or less, more preferably 10 nm or less, It is more preferably 5 nm or less. Further, the angle θ ₁ formed by the film-forming direction (corresponding to the longitudinal direction) of the cellulose ester film of the present invention and the slow axis is 0.
The closer to 90 °, + 90 ° or −90 °, the more preferable. However, θ ₁ is a narrow angle formed by the film forming direction and the slow axis, and is in the range of + 90 ° to −90 °. By doing so, the polarization degree of the polarizing plate using the protective film for a polarizing plate of the present invention is improved. Here, the slow axis is the direction in which the in-plane refractive index of the film is highest. More preferably, θ ₁ and in-plane retardation R ₀ have the following relationship.

P ≦ 1-sin ² (2θ ₁ ) × sin ² (πR ₀ / λ) Here, when P is 0.999, θ ₁ and R ₀ preferably satisfy the above formula, and more preferably 0.9995, more preferably 0.9998, even more preferably 0.9
It is most preferable that θ ₁ and R ₀ satisfy the above formula when 999, especially 0.99999. λ represents the wavelength of light at the time of three-dimensional refractive index measurement for obtaining θ ₁ and R ₀ ,
It is in the range of 650 nm. Preferably, the above formula is satisfied when λ is 590 nm, and more preferably the above formula is satisfied when λ is 400 nm.

Other good properties of the cellulose ester film of the present invention are as follows.

The light transmittance of visible light (polarizing plate protective film after saponification treatment described below) is preferably 90% or more, more preferably 95% or more, and further 96% or more. Preferably, the cellulose ester film of the present invention has 97% or more after the saponification treatment.

The haze is preferably less than 1%,
It is more preferably less than 0.5%, and further preferably less than 0.1%. Most preferably, it is 0%.
The cellulose ester film of the present invention has a content of less than 0.1% even after saponification treatment.

Further, in the process of producing a cellulose ester film, the curl of the film caused by the movement of the plasticizer in the thickness direction of the film during the conventional production,
Since the cellulose ester film containing the polymer of the present invention does not move, curling hardly occurs and good flatness can be obtained.

Basically, the nature of high temperature and high humidity is not limited to all, but often depends on water absorption.
The cellulose ester film containing the polymer of the present invention has smaller water absorption and excellent properties than the film not containing them. In general, the water absorption rate of a cellulose ester film is about 3% by mass or less under high humidity, whereas the cellulose ester film of the present invention is characterized by being 2% by mass or less.

In addition to the above, the cellulose ester film containing the polymer of the present invention has physical, mechanical or chemical properties equivalent to or higher than those of a normal cellulose ester film containing no polymer. There is.

[Protective Film for Polarizing Plate and Polarizing Plate] As described above, at least one surface of the cellulose ester film of the present invention is subjected to saponification treatment to form a protective film for polarizing plate, which is attached to at least one surface of a polarizing film described below. Thus, a polarizing plate useful for a liquid crystal display device can be obtained.

The saponification treatment is carried out, for example, by treating the surface of the cellulose ester film with 2 mol / L NaOH at 40 to 60 ° C.
After soaking in the aqueous solution for about 30 to 150 seconds, at room temperature for about 30 to
Wash with water for 60 seconds, then add about 1 to 5 mass% HCl aqueous solution for about 30
It is neutralized for ~ 60 seconds, then washed with normal temperature water for about 30-60 seconds and dried at about 80 ° C, but not limited to this method.

The polarizing film is made of, for example, polyvinyl alcohol,
An aqueous solution of a polyvinyl alcohol-based polymer such as an ethylene-vinyl alcohol copolymer is formed into a film, which is uniaxially stretched and dyed with iodine or a dichroic dye is further uniaxially stretched, and then crosslinked like a boron compound. It is water-resistant treated with an agent.

As described above, the polarizing plate of the present invention is obtained by laminating the protective film for a polarizing plate (cellulose ester film) of the present invention, the surface of which is saponified, on at least one surface of the polarizing film. An example of how to prepare a polarizing film and how to attach it to the polarizing film is shown. Two saponified protective films for polarizing plates are coated with an aqueous solution of polyvinyl alcohol as an adhesive solution on each side, The uniaxially stretched polyvinyl alcohol film is dipped in an iodine solution, and then the uniaxially stretched polarizing film is sandwiched and bonded. Examples of the adhesive liquid include polyvinyl alcohol-based adhesive liquids such as a polyvinyl alcohol aqueous solution and a polyvinyl butyral solution, and vinyl polymerization-based latexes such as butyl acrylate, but a completely saponified polyvinyl alcohol aqueous solution is preferable.

[Characteristics of Polarizing Plate] <Foreign Substances / Defects> In a polarizing plate in which a cellulose ester film and stretched polyvinyl alcohol are bonded together, the presence of dust reduces the yield.
Since the foreign matter is shiningly observed in the polarized crossed nicols dark field state, the presence of the foreign matter becomes clear, and such a state is not preferable for the polarizing plate. It is preferable that there is substantially no foreign matter in the polarizing plate, but per 250 mm ² area,
Substantially, it is acceptable that the number of foreign matter having a size of 5 to 50 μm is 200 or less and 50 μm, and the number of foreign matter of 0 or more is zero, and preferably 100 or less foreign matter having a size of 5 to 50 μm,
More preferably, it is 50 or less. Although some of the foreign substances existing in the film depend on the filtration accuracy of the dope before film formation, they are often related to stains such as plasticizers. Since the cellulose ester film containing the polymer of the present invention does not use a plasticizer, it is characterized by having extremely few foreign substances.

<Durability of Polarizing Plate> When the polarizing plate is exposed to high temperature and high humidity, the edges of the polarizing plate may become white. 8
The durability of the polarizing plate is examined by exposing it to an atmosphere of 0 ± 3 ° C. and 90 ± 3% RH for 50 hours and observing the area of white spots generated at the edge of the polarizing plate by crossed nicols as an area ratio to the entire area. The white spots on the edge can be visually determined because the edge portion of the polarizing plate that does not transmit light in the orthogonal state is in a state of transmitting light. In the state of the polarizing plate, it is a phenomenon in which the display of the edge part cannot be seen. The polarizing plate of the present invention does not have such white spots and can provide an excellent polarizing plate.

[Suitability of Liquid Crystal Image Display Device] The cellulose ester film of the present invention is a member used in a liquid crystal image display device, for example, a polarizing plate, a protective film for polarizing plate, a retardation plate, a reflecting plate, a viewing angle improving film, Examples of the antiglare film, antireflection film, antistatic film and the like. Among them, it is suitable for a polarizing plate, a protective film for a polarizing plate, a retardation film, and a viewing angle improving film, which have strict requirements for dimensional stability.

[0086]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 [Synthesis of Polymers 1 to 12] <Polymer 1> 10 parts by mass of methyl acrylate 1 part by mass of 2-hydroxyethyl acrylate 1 part by mass of azobisisobutyronitrile (AIBN) 30 parts by mass of toluene The above composition Into a four-necked flask (with a charging port, a thermometer, a reflux condenser, a nitrogen inlet, and a stirrer), and gradually add 8
The temperature was raised to 0 ° C., polymerization was carried out for 5 hours with stirring, and after the completion of the polymerization, the polymer solution was poured into a large amount of methanol to cause precipitation, which was further washed with methanol, purified and dried to obtain a weight average molecular weight of 5,000 ( Polymer 1 (measured by GPC) was obtained.

<Polymer 2> Methyl acrylate 10 parts by mass 2-Hydroxyethyl acrylate 1 part by mass AIBN 2 parts by mass Toluene 30 parts by mass Polymerization 2, precipitation and purification in the same manner as in Polymer 1 to give Polymer 2 having a weight average molecular weight of 2,000. Obtained.

<Polymer 3> Methyl acrylate 12 parts by mass Azobis (2-hydroxyethyl butyrate) 2.4 parts by mass Toluene 30 parts by mass Polymerization, precipitation and purification similar to that of the polymer 1 to obtain a polymer having a weight average molecular weight of 2,000. Got 3.

<Polymer 4> Methyl Methacrylate 10 parts by mass 2-Hydroxyethyl Methacrylate 1 part by mass AIBN 2 parts by mass Toluene 30 parts by mass Polymerization 4, precipitation and purification in the same manner as Polymer 1 to give Polymer 4 having a weight average molecular weight of 2,000. Obtained.

<Polymer 5> Methyl acrylate 6 parts by mass Ethyl acrylate 5 parts by mass 2-Hydroxyethyl acrylate 1 part by mass AIBN 2 parts by mass Toluene 30 parts by mass Polymerization, precipitation and purification in the same manner as in Polymer 1 and weight average molecular weight 2, 000 Polymer 5 was obtained.

<Polymer 6> Methyl Methacrylate 6 parts by mass Ethyl Methacrylate 5 parts by mass 2-Hydroxyethyl Methacrylate 1 part by mass AIBN 2 parts by mass Toluene 30 parts by mass Polymerization, precipitation and purification in the same manner as in Polymer 1 and weight average molecular weight 2, 000 Polymer 6 was obtained.

<Polymer 7> JP-A 2000-34482
Bulk polymerization was carried out by the polymerization method described in JP-A-3. That is, the content was heated to 70 ° C. while introducing the following methyl methacrylate and ruthenocene into a flask equipped with a stirrer, a nitrogen gas introduction tube, a thermometer, an inlet and a reflux condenser. Then, half of the following β-mercaptopropionic acid, which had been sufficiently replaced with nitrogen gas, was added to the flask with stirring.
After the addition of β-mercaptopropionic acid, the content in the stirring flask was maintained at 70 ° C. and polymerization was carried out for 2 hours. Furthermore, after the remaining half of the β-mercaptopropionic acid replaced with nitrogen gas was added, the temperature of the contents during stirring was further increased to 7%.
Polymerization was carried out for 4 hours while maintaining the temperature at 0 ° C. The temperature of the reaction product was returned to room temperature, and 20 parts by mass of a 5% by mass tetrahydrofuran solution of benzoquinone was added to the reaction product to terminate the polymerization. Tetrahydrofuran, residual monomers and residual thiol compounds were removed while gradually heating the polymer to 80 ° C. under reduced pressure with an evaporator to obtain polymer 7. The weight average molecular weight was 3,400. The hydroxyl value (according to the measuring method described below) was 50.

Methyl methacrylate 100 parts by mass Ruthenocene (metal catalyst) 0.05 parts by mass β-mercaptopropionic acid 12 parts by mass (method of measuring hydroxyl value) This measurement is carried out according to JIS K 00
70 (1992). This hydroxyl value is 1g of sample
Is defined as the number of mg of potassium hydroxide required to neutralize the acetic acid bound to the hydroxyl group when acetylated. Specifically, a sample Xg (about 1 g) is precisely weighed in a flask, and 20 mL of an acetylating reagent (20 mL of acetic anhydride to which pyridine is added to make 400 mL) is accurately added. Attach an air cooling tube to the mouth of the flask,
Heat in a 0 ° C. glycerin bath. After 1 hour and 30 minutes, it is cooled, 1 mL of purified water is added from an air cooling tube, and acetic anhydride is decomposed into acetic acid. Next, using a potentiometric titrator, 0.5 m
Titrate with ol / L potassium hydroxide ethanol solution,
The end point is the inflection point of the obtained titration curve. Further, as a blank test, titration is performed without inserting the sample, and the inflection point of the titration curve is determined. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(B−C) × f × 28.05 / X} + D In the formula, B is the amount (mL) of the 0.5 mol / L potassium hydroxide ethanol solution used in the blank test, C Is the amount (mL) of the 0.5 mol / L potassium hydroxide ethanol solution used for the titration, f is the factor of the 0.5 mol / L potassium hydroxide ethanol solution, D is the acid value, and 28.05 is the hydroxylation. 1 mol amount of potassium is 1/2 of 56.11.

<Polymer 8> JP-A 2000-12891
Bulk polymerization was carried out by the polymerization method described in JP-A-1. That is, the following methyl acrylate was charged into a flask equipped with a stirrer, a nitrogen gas introduction tube, a thermometer, an inlet and a reflux condenser, and nitrogen gas was introduced to replace the thioglycerol below with the nitrogen gas in the flask with stirring. Was added. After the addition of thioglycerol, polymerization was carried out for 4 hours while maintaining the temperature of the content at 60 ° C., the content was returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added to terminate the polymerization. The contents were transferred to an evaporator and tetrahydrofuran, residual monomers and residual thioglycerol were removed under reduced pressure at 80 ° C. to obtain polymer 8
Got Weight average molecular weight is 2,100 and hydroxyl value is 3
It was 5.

100 parts by mass of methyl acrylate 5 parts by mass of thioglycerol <Polymer 9> Polymer 9 is obtained by polymerizing a mixed monomer of methyl acrylate and benzyl methacrylate using ruthenocene and β-mercaptopropionic acid in the same manner as in Polymer 7. It was Weight average molecular weight is 1,800,
The hydroxyl value was 35.

Methyl acrylate 70 parts by mass Benzyl methacrylate 30 parts by mass Ruthenocene 0.05 parts by mass β-mercaptopropionic acid 12 parts by mass <Polymer 10> In the same manner as in Polymer 8, a mixed monomer of methyl acrylate and cyclohexyl methacrylate and thioglycerol were added. Polymerize using Polymer 1
I got 0. Weight average molecular weight is 2,200, hydroxyl value is 4
It was 0.

Methyl acrylate 65 parts by mass Cyclohexyl methacrylate 35 parts by mass Thioglycerol 5 parts by mass <Polymer 11> Polymer 11 was polymerized using vinyl acetate monomer and thioglycerol as in Polymer 8.
Got Weight average molecular weight is 1,600, hydroxyl value is 35
Met.

Vinyl acetate 100 parts by mass Thioglycerol 5 parts by mass <Polymer 12> Polymer 12 was obtained by polymerization using a mixed monomer of vinyl acetate monomer and vinyl benzoate and thioglycerol in the same manner as in Polymer 8. The weight average molecular weight was 4,000 and the hydroxyl value was 47.

Vinyl acetate 70 parts by mass Vinyl benzoate 30 parts by mass Thioglycerol 5 parts by mass [Preparation of dope] (Preparation of dopes 1 to 15) <Dope compositions 1 to 12> Cellulose triacetate (degree of substitution 2.83) 100 Parts by mass Polymers (1 to 12) of the above synthesis 15 parts by mass Tinuvin 326 2 parts by mass Methylene chloride 475 parts by mass Ethanol 50 parts by mass <Dope composition 13> Cellulose triacetate (substitution degree 2.8) 100 parts by mass Triphenyl phosphate 15 Parts by mass Tinuvin 326 1 part by mass methylene chloride 475 parts by mass ethanol 50 parts by mass <dope composition 14> cellulose triacetate (substitution degree 2.8) 100 parts by mass ethylphthalyl glycolate 4 parts by mass tinuvin 326 1 part by mass methylene chloride 475 Parts ethanol 50 parts by weight <dope composition 15> cellulose triacetate (substitution degree 2.8) 100 parts by weight triphenyl phosphate 10 parts by weight lauryl benzene sulfonate 2 parts by weight tinuvin 326 1 part by weight methylene chloride 475 parts by weight ethanol 50 parts by weight The above dope compositions 1 to 15 were separately charged into a pressure-closed vessel, heated to 70 ° C. to increase the pressure inside the vessel to 1 atm or more, and the cellulose ester was completely dissolved while stirring. The dope temperature was lowered to 35 ° C., and the mixture was allowed to stand overnight, and this dope was dried by Azumi Filter Paper No. After filtering using 244, it was left still overnight for defoaming. Next is Finemet NM manufactured by Nippon Seisen Co., Ltd. (absolute filtration accuracy 10
0 μm), fine pore NF (absolute filtration accuracy 50 μm,
15 μm and 5 μm in this order with increasing filtration accuracy) and filtered at a filtration pressure of 1.0 × 10 ⁶ Pa to provide a membrane.

[Formation of Cellulose Ester Film] <Cellulose Ester Films 1 to 15> Using dopes 1 to 15 at 35 ° C. obtained by filtration, endless endless transitions from a hanger type die to 22 ° C. A film was formed by casting on a stainless belt. After that, the organic solvent was evaporated until the residual solvent amount became 25 mass% by the time the cast stainless belt completed one round, and the web was peeled off. The time from casting to peeling was 3 minutes. After peeling, the web is dried at 120 ° C while clipping the both ends of the web with a tenter to hold the width of the web while transporting, remove the clips, and draw a plurality of rolls arranged in zigzag with a roll dryer at 120 to 135 ° C. After drying, the film is cooled and subjected to knurling with a width of 10 mm and a height of 5 μm on both ends of the film to have an initial winding tension of 150 N / width and a final winding tension of 100 N / width, respectively. Wound up. The thickness of each of the obtained cellulose triacetate films 1 to 15 was 40 μm, the winding length was 3000 m, and the width was 1300 mm.

[Preparation of Polarizing Plate] (Preparation of Polarizing Film Protective Films 1 to 15) The formed cellulose ester films 1 to 15 were prepared at 40 ° C. for 2.5 m.
The surface was saponified with an ol / L sodium hydroxide aqueous solution for 60 seconds, washed with water for 3 minutes and dried to obtain protective films 1 to 15 for polarizing plates.

(Production of Polarizing Plates 1 to 15) 120 μm
Of polyvinyl alcohol having a thickness of 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid at 50 ° C.
A polarizing film stretched 4 times in the vertical direction was prepared. The surface-saponified cellulose ester film was completely saponified on both sides of the polarizing film in an amount of 5% by mass of polyvinyl alcohol.
Polarizing plates 1 to 15 were produced by laminating the aqueous solution as an adhesive.

[Evaluation] <Retention> A film sample is cut into a size of 10 cm × 10 cm, left in a room at 23 ° C. and 55% RH for 24 hours, and the mass F of the sample is measured. 80
It was left for 48 hours in a room at 90 ° C. and 90% RH. This sample was returned to the condition of a room of 23 ° C. and 55% RH and left for 24 hours to measure the mass A, and the retention property was calculated by the following method.

Retention (% by mass) = {(F−A) / F} × 100 <Measurement of water vapor permeability> The water vapor permeability of each sample was measured according to the method described in JIS Z 0208. The temperature and humidity conditions for measurement are 25 ° C. and 90% RH.

<Dimensional Stability> The cellulose ester film before saponification was conditioned for 24 hours in a room at 23 ° C. and 55% RH, and then, in the same room, 100 mm in the longitudinal direction and the width direction of the film on the surface of the cellulose ester film. Mark two crosses at intervals and measure their dimensions accurately to determine the distance a
And heat treatment at 80 ° C, 90% RH for 50 hours,
Again, the humidity was adjusted in a room at 23 ° C. and 55% RH for 24 hours, the distance between two marks was measured with a cassette meter, and the value was taken as b.

Dimensional change rate (%) = [(ba) / a] × 100 <retardation> automatic birefringence meter KOBRA-21A
Using DH (manufactured by Oji Scientific Instruments Co., Ltd.), 23 ° C, 55
In an environment of% RH, a three-dimensional refractive index is measured at a wavelength of 590 nm, and the refractive index nx in each of the vertical, horizontal, and thickness directions,
Find ny and nz. The retardation value (R _t value) is calculated according to the following formula R _t value (nm) = {(nx + ny) / 2−nz} × d.
Here, nx is the refractive index in the direction parallel to the film forming direction, ny is the refractive index in the direction horizontal to the film forming direction in the width direction, nz is the refractive index in the film thickness direction, Also d
Represents the thickness (nm) of the film, respectively.

<Foreign matter / defect> A film sample was cut out in a clean room to a length of 1 m in the longitudinal direction, and the sample was examined for the presence / absence of foreign matter / defect while transmitting light on a Schaukasten and under reflected light. And the size was observed and evaluated by the following grades.

A: No foreign matter or defect having a size of 50 μm or more, 0 to 10 particles less than 50 μm were observed B: No foreign matter or defect having a size of 50 μm or more, 50 μm
11 to 30 particles less than m were observed C: 1 to 10 foreign particles / defects having a size of 50 μm or more were observed, 31 to 50 particles less than 50 μm were observed D: a size of 50 μm or more 11 to 30 foreign particles / defects were observed, 51 to 99 particles less than 50 μm were observed E: 31 foreign particles / defects having a size of 50 μm or more were observed, 100 particles less than 50 μm were 100 It was observed above.

<Durability of Polarizing Plates> 100 from each polarizing plate
Cut out two samples of size mm x 100 mm and
After exposure to an atmosphere of 90 ° C and 90% RH for 50 hours, the area of white spots generated at the edges of the polarizing plate by crossed Nicols in an atmosphere of normal temperature and normal humidity was observed as an area ratio with respect to the entire area. evaluated.

A: No white spots were present at all B: White spots were less than 2% of the total area C: White spots were 2% or more and less than 5% of the total area D: White spots were 5% or more and less than 10% with respect to the entire area E: White spots were 10% or more with respect to the entire area.

[0113]

[Table 1]

(Results) It can be seen that the cellulose ester film of the present invention has small retention and moisture permeability, excellent dimensional change, proper retardation, and excellent properties. Further, it became clear that the polarizing plate of the present invention had almost no foreign matter or defects and was excellent in polarizing plate durability. It can be seen that all the comparative examples using the conventional low molecular weight plasticizer are inferior.

[0115]

EFFECTS OF THE INVENTION By providing a cellulose ester film containing a polymer having a weight average molecular weight of 500 or more and less than 10,000, which has excellent compatibility with cellulose ester, precipitates or volatiles are generated from the web during production. It is difficult and has excellent productivity, and also has low retention and low moisture permeability,
It is possible to provide a cellulose ester film having extremely small stretchability even in a hot and humid environment, and to provide a good-quality polarizing plate that does not deteriorate a polarizer even in a hot and humid state.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H049 BA02 BB33 BC09 BC22                 4F071 AA02 AA08 AA31 AA81 AF08                       AF10 AH16 BA02 BB02 BC01                       BC12                 4J002 AA01X AB02W BG00X BG04X                       BG05X BG07X FD206

Claims (21)

[Claims] 1. A cellulose ester film formed by a solution casting film forming method using a dope containing a cellulose ester, a polymer obtained by polymerizing an ethylenically unsaturated monomer, and an organic solvent, wherein the ethylene A cellulose ester film having a weight average molecular weight of 500 or more and less than 10,000, which is obtained by polymerizing a polyunsaturated monomer. 2. A cellulose ester film formed by a solution casting method using a dope containing a cellulose ester, an acrylic polymer and an organic solvent, wherein the acrylic polymer has a weight average molecular weight of 500.
A cellulose ester film having a thickness of at least 10,000. 3. The cellulose ester film according to claim 2, wherein the acrylic polymer has a weight average molecular weight of 500 to 5,000. 4. The cellulose ester film according to claim 2, wherein the acrylic polymer has 30% by mass or more of acrylic acid methyl ester monomer units. 5. The cellulose ester film according to claim 4, wherein the acrylic polymer has 40% by mass or more of a methacrylic acid methyl ester monomer unit. 6. The cellulose ester film according to claim 2, wherein the acrylic polymer contains 2 to 20% by mass of an acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group. . 7. The cellulose ester film according to claim 2, wherein the acrylic polymer has a hydroxyl group on at least one terminal of the main chain. 8. A cellulose ester film formed by a solution casting film forming method using a dope containing a cellulose ester, an acrylic polymer having an aromatic ring as a side chain, and an organic solvent, wherein the aromatic ring is located on the side. The weight average molecular weight of the acrylic polymer in the chain is 500 or more 1
A cellulose ester film which is less than 10,000. 9. The cellulose ester film according to claim 8, wherein the acrylic polymer having an aromatic ring as a side chain has a weight average molecular weight of 500 to 5,000. 10. The acrylic polymer having an aromatic ring as a side chain has 20 to 40% by mass of an acrylic acid ester monomer unit having an aromatic ring, and an acrylic acid methyl ester or methacrylic acid methyl ester monomer unit. It has 50-80 mass%, The cellulose ester film of Claim 8 or 9 characterized by the above-mentioned. 11. The acrylic polymer having an aromatic ring as a side chain contains 2 to 20% by mass of an acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group. The cellulose ester film according to item 1. 12. The cellulose ester film according to claim 8, wherein the acrylic polymer having an aromatic ring as a side chain has a hydroxyl group on at least one terminal of the main chain. . 13. A cellulose ester film formed by a solution casting film forming method using a dope containing a cellulose ester, an acrylic polymer having a cyclohexyl group in a side chain, and an organic solvent, wherein the cyclohexyl group is a side group. A cellulose ester film having a weight average molecular weight of an acrylic polymer having a chain of 500 or more and less than 10,000. 14. The weight average molecular weight of the acrylic polymer having a cyclohexyl group in a side chain is 500 to 5,
It is 000, The cellulose-ester film of Claim 13 characterized by the above-mentioned. 15. The acrylic polymer having a cyclohexyl group in a side chain has 20 to 40 mass% of an acrylic acid ester monomer unit having a cyclohexyl group, and an acrylic acid methyl ester or methacrylic acid methyl ester monomer unit. It has 50-80 mass%, The cellulose ester film of Claim 13 or 14 characterized by the above-mentioned. 16. The acrylic polymer having a cyclohexyl group as a side chain contains 2 to 20% by mass of an acrylic acid or methacrylic acid ester unit having a hydroxyl group. Item 7. A cellulose ester film according to item. 17. The cellulose ester film according to claim 13, wherein the acrylic polymer having a cyclohexyl group as a side chain has a hydroxyl group at at least one terminal. 18. A film having a thickness of 10 to 60 μm and having a thickness of 80 ±
The cellulose ester according to any one of claims 1 to 17, wherein the moisture permeability of the film in an atmosphere of high temperature and high humidity of 5 ° C and 90 ± 5% RH is 250 g / m ² · 24h or less. the film. 19. The mass of the film in an atmosphere of normal temperature and normal humidity of 23 ± 3 ° C. and 55 ± 3% RH and 80 ± 3 ° C., 9
The rate of change (holding capacity) of the mass after standing for 50 hours in a high temperature and high humidity atmosphere of 0 ± 3% RH and then returning to the normal temperature and normal humidity atmosphere for 24 hours (holding capacity) is 2 mass% or less. The cellulose ester film according to any one of claims 1 to 18, characterized in that. 20. A protective film for a polarizing plate, characterized in that the surface of the cellulose ester film according to any one of claims 1 to 19 is saponified. 21. A polarizing plate formed by laminating the protective film for a polarizing plate according to claim 20 on at least one surface of a polarizer.