JP5912073B2 - Cellulose acylate film, polarizing plate and liquid crystal display device - Google Patents

Description

  The present invention relates to a cellulose acylate film, and a polarizing plate and a liquid crystal display device using the cellulose acylate film.

In recent years, liquid crystal display devices are expected to be used in various harsh environments such as outdoors as mobile applications expand. The polarizing plates used in these liquid crystal display devices are resistant to high temperatures and high humidity. Sex is required.
For example, Patent Document 1 discloses a cellulose acylate film containing a specific sugar ester compound and further containing an acrylic polymer or a polyester having no aromatic ring, and is stable in retardation even in a high temperature and high humidity environment. Is described as high.

In addition, liquid crystal panels are becoming lighter and thinner, and there are demands for thinner polarizing plates and further polarizing plate protective films.
However, it is known that light unevenness and the like may occur with the lightening and thinning of the liquid crystal panel, and from the viewpoint of preventing it, Patent Document 2 contains 30% by mass or more of a specific polyester oligomer. A cellulose acylate film is disclosed, and Patent Document 2 describes that it has a small optical anisotropy and is suitable for an IPS liquid crystal display device.

International Publication No. 2008/015911 JP 2012-025804 A

  An object of the present invention is to provide a cellulose acylate film used for a polarizing plate protective film having a small optical anisotropy suitable for an IPS type liquid crystal display device, a polarizing plate using the cellulose acylate film, and a liquid crystal display device. A cellulose acylate film capable of reducing the thickness of the polarizing plate protective film and the durability of the polarizing plate, which are required in recent years, and a polarizing plate and a liquid crystal display device using the cellulose acylate film. Is to provide.

The said subject can be achieved by the following means. That is, the present invention is as follows.
<1>
Each contains one or more of the following additives (A) and (B),
In an environment with a temperature of 25 ° C. and a relative humidity of 60%, the in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm, the retardation in the thickness direction (Rth) is −10 to 5 nm, and
A cellulose acylate film having a thickness of 15 to 35 μm.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic Polyester oligomer wherein m: n is from 2: 8 to 0:10, where n is the molar ratio of the group dicarboxylic acid
Additive (B): a sugar ester compound having 1 to 12 at least one pyranose structure or furanose structure and alkylating all or part of the hydroxyl groups of the structure
<2>
<1>, wherein the additive (B) is a sugar ester compound having one or two pyranose structures or furanose structures and alkyl esterifying all or part of the hydroxyl groups of the structure. The cellulose acylate film described.
<3>
The cellulose acylate film according to <2>, wherein the additive (B) is a monocyclic ring having a pyranose structure or a furanose structure, and is a sugar ester compound obtained by alkyl esterifying all or part of the hydroxyl groups of the structure.
<4>
The cellulose acylate film according to <3>, wherein the additive (B) is a sugar ester compound obtained by alkyl esterifying all or part of hydroxyl groups having a glucose structure.
<5>
The cellulose acylate film according to any one of <1> to <4>, wherein the total content of the additives (A) and (B) is 5 to 20% by mass with respect to the cellulose acylate. .
<6>
The cellulose acylate film according to any one of <1> to <5>, wherein the polyester oligomer is a polyester oligomer in which at least one end is sealed with a monocarboxylic acid.
<7>
The cellulose acylate film according to <6>, wherein the monocarboxylic acid is an aliphatic monocarboxylic acid having 2 to 10 carbon atoms.
<8>
Each contains one or more of the following additives (A) and (B),
In an environment with a temperature of 25 ° C. and a relative humidity of 60%, the in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm, the retardation in the thickness direction (Rth) is −10 to 5 nm, and
A cellulose acetate film having a thickness of 15 to 35 μm.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic Polyester oligomer in which m: n is 5: 5 to 0:10, where n is the molar ratio of the group dicarboxylic acid
Additive (B): a sugar ester compound having 1 to 12 at least one pyranose structure or furanose structure and alkylating all or part of the hydroxyl groups of the structure
<9>
The cellulose acetate film according to <8>, wherein in the cellulose acetate, the total degree of acyl substitution to the hydroxyl group of cellulose is 2.80 to 2.95.
<10>
The dicarboxylic acid contains the polyester oligomer, wherein m: n is from 2: 8 to 0:10, where m is the aliphatic dicarboxylic acid molar ratio and n is the aromatic dicarboxylic acid molar ratio <8>. Or the cellulose acetate film as described in <9>.
<11>
The cellulose acetate film according to <8>, wherein the additive (B) is a monocyclic ring having a pyranose structure or a furanose structure, and is a sugar ester compound obtained by alkyl esterifying all or part of the hydroxyl groups of the structure.
<12>
The cellulose acetate film according to any one of <8> to <11>, wherein the total content of the additives (A) and (B) is 5 to 20% by mass with respect to the cellulose acetate.
<13>
The cellulose acetate film according to any one of <8> to <12>, wherein the polyester oligomer is a polyester oligomer in which at least one end is sealed with a monocarboxylic acid.
<14>
A polarizing plate comprising at least one cellulose acylate film according to any one of <1> to <7> or a cellulose acetate film according to any one of <8> to <13>.
<15>
A liquid crystal display device comprising the polarizing plate according to <14>.
<16>
The liquid crystal display device according to <15>, which is an IPS mode.
Although this invention is invention concerning said <1>-<16>, below, other matters (for example, following [1]-[10]) are also described.
[1]
Each contains one or more of the following additives (A) and (B),
In an environment with a temperature of 25 ° C. and a relative humidity of 60%, the in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm, the retardation in the thickness direction (Rth) is −10 to 5 nm, and the thickness is 15 to 35 μm. Cellulose acylate film.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic When the molar ratio of the group dicarboxylic acid is n, the polyester oligomer / additive (B) where m: n is 5: 5 to 0:10: 1 to 12 at least one of a pyranose structure or a furanose structure , Sugar ester compounds obtained by alkylating all or part of the hydroxyl groups of the structure [2]
In the above [1], the additive (B) is a sugar ester compound having one or two pyranose structures or furanose structures and alkyl esterifying all or part of the hydroxyl groups of the structure. The cellulose acylate film described.
[3]
The cellulose acylate film according to [2], wherein the additive (B) is a monocyclic ring having a pyranose structure or a furanose structure, and is a sugar ester compound obtained by alkyl esterifying all or part of the hydroxyl groups of the structure.
[4]
The cellulose acylate film according to [3], wherein the additive (B) is a sugar ester compound obtained by alkyl esterifying all or part of the hydroxyl groups of the glucose structure.

[5]
The cellulose acylate film according to any one of [1] to [4], wherein the total content of the additives (A) and (B) is 5 to 20% by mass with respect to the cellulose acylate. .
[6]
The cellulose acylate film according to any one of [1] to [6], wherein the additive (A) is a polyester having at least one end sealed with a monocarboxylic acid.
[7]
The cellulose acylate film according to [6], wherein the monocarboxylic acid is an aliphatic monocarboxylic acid having 2 to 10 carbon atoms.
[8]
A polarizing plate comprising at least one cellulose acylate film according to any one of [1] to [7].
[9]
The liquid crystal display device containing the polarizing plate as described in [8].
[10]
The liquid crystal display device according to [9], which is in an IPS mode.

  According to the present invention, there are provided a cellulose acylate film used for a polarizing plate protective film having a small optical anisotropy suitable for an IPS type liquid crystal display device, a polarizing plate using the cellulose acylate film, and a liquid crystal display device. Cellulose acylate film capable of reducing the thickness of the polarizing plate protective film and the durability of the polarizing plate, which have been demanded in recent years, and a polarizing plate and a liquid crystal display device using the cellulose acylate film Can be provided.

  Hereinafter, the present invention will be described in detail. In the present specification, when numerical values represent physical property values, characteristic values, etc., the descriptions “(numerical value 1) to (numerical value 2)” and “(numerical value 1) to (numerical value 2)” are “(numerical value 1). ) ”(Numerical value 2) or less”.

The cellulose acylate film of the present invention contains one or more of the following additives (A) and (B), respectively, and an in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm in an environment of a temperature of 25 ° C. and a relative humidity of 60%. The thickness direction retardation (Rth) is -10 to 5 nm, and the thickness is 15 to 35 μm.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic When the molar ratio of the group dicarboxylic acid is n, the polyester oligomer / additive (B) where m: n is 5: 5 to 0:10: 1 to 12 at least one of a pyranose structure or a furanose structure , Sugar ester compounds in which all or part of the hydroxyl groups in the structure are alkylesterified

[Additive (A): Polyester oligomer]
The polyester oligomer used in the present invention will be described.
The number average molecular weight (Mn) of the polyester oligomer in the present invention is 500 to 3000, preferably 600 to 2000, more preferably 600 to 1500, and still more preferably 600 to 1200. If the number average molecular weight of the polyester oligomer is 500 or more, the volatility is low, and film failure and process contamination due to volatilization under high temperature conditions during stretching of the polymer film are less likely to occur. Moreover, if it is 3000 or less, compatibility with a thermoplastic polymer will become high, and it will become difficult to produce the bleed out at the time of film forming and at the time of heat-stretching.
The number average molecular weight of the polyester oligomer in the present invention can be measured and evaluated by gel permeation chromatography.

The polyester oligomer used in the present invention has a repeating unit composed of a dicarboxylic acid and a diol, and when the molar ratio of the aliphatic dicarboxylic acid is n and the molar ratio of the aromatic dicarboxylic acid is n. , M: n is 5: 5 to 0:10, preferably 3: 7 to 0:10, and most preferably 2: 8 to 0:10.
As a synthesis method, a known method such as a dehydration condensation reaction of a dicarboxylic acid and a diol, or addition of a dicarboxylic anhydride to a diol and a dehydration condensation reaction can be used.

  The dicarboxylic acid and diol that can be preferably used for the synthesis of the polyester oligomer in the present invention will be described below.

(Dicarboxylic acid)
Among the dicarboxylic acids, examples of the aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedicarboxylic acid. , Dodecanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the like. More preferable aliphatic dicarboxylic acids include malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, 1,4 -Cyclohexanedicarboxylic acid, particularly preferably succinic acid, glutaric acid and adipic acid.
Among the dicarboxylic acids, the aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3 -Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,8-naphthalenedicarboxylic acid, and more preferable aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, and 1,8-naphthalenedicarboxylic acid. 2,3-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, particularly preferably phthalic acid, isophthalic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, most preferably Can be designed to reduce the optical anisotropy of cellulose acylate film Terms, phthalic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid.

(Diol)
Examples of the diol (glycol) include aliphatic diols having 2 to 12 carbon atoms, alkyl ether diols having 4 to 20 carbon atoms, and aromatic ring-containing diols having 6 to 20 carbon atoms, and two types selected from these. You may use the above together.

Examples of the aliphatic diol include alkyl diols and alicyclic diols. For example, ethane diol (ethylene glycol), 3-oxapentane-1,5-diol (diethylene glycol), 1,2-propanediol, 1, 3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl- 1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol, 1,4-hexanedio 1,5-hexanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8- Examples include octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, or 1,4-cyclohexanedimethanol.
Preferred aliphatic diols include ethanediol, 3-oxapentane-1,5-diol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 2-methyl. -1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,4-hexanediol, 1,5-hexanediol, 1 , 6-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, particularly preferably ethanediol, 1,2-propanediol, 1,3 -Propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, - pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol.

  Preferred examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol, and polypropylene ether glycol. Commercially available polyether glycols include Carbowax resin, Pluronics resin, and Niax resin.

Examples of the aromatic diol having 6 to 20 carbon atoms include bisphenol A, 1,2-hydroxybenzene, 1,3-hydroxybenzene, 1,4-hydroxybenzene, and benzene-1,4-methanol, preferably Bisphenol A, 1,4-hydroxybenzene, and benzene-1,4-dimethanol.
The aromatic diol preferably has 6 to 12 carbon atoms.

(Sealing)
It is preferable that both ends of the polyester oligomer of the present invention are sealed at least one end, and the end is an aliphatic group having 1 to 22 carbon atoms, an aromatic ring-containing group having 6 to 20 carbon atoms, or a carbon number. It is preferably at least one selected from an aliphatic carbonyl group having 1 to 22 carbon atoms and an aromatic carbonyl group having 6 to 20 carbon atoms.
Furthermore, when both ends of the polyester oligomer are sealed, the polyester oligomer is more preferably sealed by reacting with a monocarboxylic acid or monoalcohol, and more preferably sealed by reacting with a monocarboxylic acid. At this time, both ends of the oligomer are monoalcohol residues or monocarboxylic acid residues. Here, the residue is a partial structure of the oligomer and represents a partial structure having the characteristics of the monomer forming the oligomer. For example, the monocarboxylic acid residue formed from monocarboxylic acid R—COOH is R—CO—.

The monocarboxylic acid residue is preferably an aliphatic monocarboxylic acid residue having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid residue having 2 to 3 carbon atoms, and 2 carbon atoms. Particularly preferred are aliphatic monocarboxylic acid residues.
When the number of carbon atoms of the monocarboxylic acid residue at both ends of the polyester oligomer is 3 or less, the volatility is reduced, the weight loss due to heating of the oligomer does not increase, and the occurrence of process contamination and surface failure is reduced. can do. That is, aliphatic monocarboxylic acids are preferable as monocarboxylic acids used for sealing. The monocarboxylic acid is more preferably an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid having 2 to 3 carbon atoms, and an aliphatic monocarboxylic acid residue having 2 carbon atoms. Particularly preferred is a group.
Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, and oleic acid. Examples of the aromatic ring-containing monocarboxylic acid include benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl benzoic acid. Acid, aminobenzoic acid, acetoxybenzoic acid, etc. are mentioned.
Among these, acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof are preferable, acetic acid or propionic acid is more preferable, and acetic acid (terminal is an acetyl group) is most preferable. Two or more monocarboxylic acids used for sealing may be mixed.

As the monoalcohol residue, a substituted or unsubstituted monoalcohol residue having 1 to 30 carbon atoms is preferable. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl Alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohol such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3- Examples include substituted alcohols such as phenylpropanol.
The end-capping alcohol residues that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, Oleyl alcohol and benzyl alcohol, especially methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol and benzyl alcohol.

  When both ends are sealed, the state at normal temperature is unlikely to be in a solid form, the handling becomes good, and a polymer film excellent in humidity stability and polarizing plate durability can be obtained.

The cellulose acylate film of the present invention preferably contains 1 to 30% by mass, more preferably 5 to 20% by mass, and more preferably 5 to 20% by mass of the polyester oligomers as additives (A). It is particularly preferable to contain ˜15% by mass.
[Additive (B): Sugar ester compound]
A sugar ester compound having 1 to 12 of at least one pyranose structure or furanose structure used in the present invention and alkyl esterifying all or part of the hydroxyl groups (hereinafter simply referred to as OH groups) of the structure will be described. .

  The sugar ester compound is a compound in which at least one substitutable group (for example, hydroxyl group or carboxyl group) in the sugar skeleton structure constituting the compound and at least one substituent are ester-bonded. Say that. That is, the sugar ester compound referred to here includes a wide range of sugar derivatives, for example, a compound containing a sugar residue such as gluconic acid as a structure. That is, the sugar ester compound includes an ester of glucose and carboxylic acid and an ester of gluconic acid and alcohol.

The sugar ester compound used in the present invention is a sugar ester compound obtained by alkyl esterifying all or part of the OH group of the compound (M) having one furanose structure or one pyranose structure, or a furanose structure or pyranose. A sugar ester compound obtained by alkylating all or part of the OH groups of the compound (D) in which at least one of the structures is bonded to each other is preferable.
The sugar ester compound used in the present invention is more preferably a sugar ester compound which is a monocyclic furanose structure or pyranose structure and alkylates all or part of the hydroxyl groups in the structure, and has a glucose structure hydroxyl group. More preferably, it is a sugar ester compound obtained by alkylesterifying all or part of the above.

Examples of the compound (M) include glucose, galactose, mannose, fructose, xylose, and arabinose, preferably glucose and fructose, and more preferably glucose.
Examples of the compound (D) include lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose. In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.
Among these compounds (D), compounds having both a furanose structure and a pyranose structure are particularly preferable, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, etc. are preferable, and sucrose is more preferable. .

In order to alkylate all or part of the OH groups in the compound (M) and the compound (D), it is preferable to use an aliphatic monocarboxylic acid.
Examples of the aliphatic monocarboxylic acid include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid; And unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid; among them, acetic acid, propionic acid and isobutyric acid are preferred. That is, the substituent is preferably an acetyl group, a propionyl group, or an isobutyryl group.

The aliphatic monocarboxylic acid used to alkylate all or part of the OH group may be two or more aliphatic monocarboxylic acids, at least one of which is branched. Aliphatic monocarboxylic acids are more preferred, and isobutyric acid is particularly preferred.
Specifically, it is preferable that all or a part of the OH group is esterified with acetic acid and isobutyric acid, that is, the substituent is an acetyl group and an isobutyryl group. When it consists only of an acetyl group and an isobutyryl group, the ratio is preferably acetyl group / isobutyryl group = 1/7 to 4/4, more preferably 1/7 to 3/5, and 2/6. It is particularly preferred.

  A method for producing these aliphatic sugar ester compounds substituted with an aliphatic monocarboxylic acid is described, for example, in JP-A-8-245678.

An example of the production of the sugar ester compound is as follows.
Acetic anhydride (200 ml) was added dropwise to a solution obtained by adding pyridine (100 ml) to glucose (29.8 g, 166 mmol), and allowed to react for 24 hours. Thereafter, the solution was concentrated by evaporation and poured into ice water. After standing for 1 hour, the mixture was filtered through a glass filter to separate the solid and water. The solid on the glass filter was dissolved in chloroform and separated with cold water until it became neutral. The organic layer was separated and dried over anhydrous sodium sulfate. After removing anhydrous sodium sulfate by filtration, chloroform was removed by evaporation and further dried under reduced pressure to obtain glycolose pentaacetate (58.8 g, 150 mmol, 90.9%). In addition, the above-mentioned monocarboxylic acid can be used instead of the acetic anhydride.

  The cellulose acylate film of the present invention preferably contains 1 to 30% by mass of sugar ester compounds, more preferably 5 to 20% by mass, and more preferably 5 to 15% by mass with respect to the cellulose acylate. Is particularly preferred.

  Specific examples of the sugar ester compound that can be used in the present invention are listed below, but the present invention is not limited thereto. Moreover, although the ester substitution degree of each sugar ester compound is not described in the following specific examples, a sugar ester compound mixture is used by using a sugar ester compound having any degree of ester substitution unless it is contrary to the gist of the present invention. It can be.

In the cellulose acylate film of the present invention, the total content of the additives (A) and (B) is preferably 5 to 20% by mass with respect to the cellulose acylate.
[Cellulose acylate]
Next, the cellulose acylate used for the cellulose acylate film of the present invention will be described.
Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, conifer pulp), and any cellulose acylate obtained from any raw material cellulose can be used. May be used. Detailed descriptions of these raw material celluloses can be found in, for example, Plastic Materials Course (17) Fibrous Resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (page 7). To page 8) can be used, and the cellulose acylate film of the present invention is not particularly limited.

The cellulose acylate according to the present invention produced from the above-described cellulose will be described.
Cellulose acylate is obtained by acylating a hydroxyl group of cellulose, and the substituent can be any acetyl group having 2 carbon atoms in the acyl group to those having 22 carbon atoms.

The acyl group having 2 to 22 carbon atoms to be substituted for the hydroxyl group of cellulose is not particularly limited and may be an aliphatic group or an aromatic group, and may be a single type or a mixture of two or more types. Cellulose acylates substituted with these groups are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, and each may further have a substituted group.
Preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl Benzoyl, naphthylcarbonyl, cinnamoyl group and the like. Among these, acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are preferable, and acetyl, propionyl and butanoyl are more preferable.
Among these, an acetyl group and a propionyl group are preferable, and an acetyl group is particularly preferable from the viewpoints of ease of synthesis, cost, and ease of control of substituent distribution. When two or more acyl groups are substituted, an acetyl group and a propionyl group are preferred.

In the cellulose acylate according to the present invention, the acyl substitution degree to the hydroxyl group of cellulose is not particularly limited, but when used for polarizing plate protective film and optical film, the higher acyl substitution degree is in the thickness direction of the film. The phase difference (Rth) is preferable because it tends to be a small value close to zero or a negative value. For this reason, it is preferable that the acyl substitution degree (total substitution degree) to the hydroxyl group of a cellulose is 2.50-3.00. Furthermore, the acyl substitution degree is preferably 2.70 to 2.96, and more preferably 2.80 to 2.95. Moreover, when only an acetyl group substitutes, it is preferable that the substitution degree of this acetyl group is 2.70-2.96, and it is more preferable that it is 2.80-2.95. The substitution degree of the propionyl group is preferably 0.20 to 2.60.
In the cellulose acylate according to the present invention, the method for measuring the substitution degree (acyl substitution degree) of acetic acid and / or a fatty acid having 3 to 22 carbon atoms substituted on the hydroxyl group of cellulose is in accordance with ASTM D-817-91. And the NMR method.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . If the degree of polymerization is too high, the viscosity of the cellulose acylate dope solution tends to be high, and film production tends to be difficult due to casting. If the degree of polymerization is too low, the strength of the produced film tends to decrease. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in JP-A-9-95538.

From the viewpoint of mechanical strength and handling suitability of the film, the mass average molecular weight Mw of the cellulose acylate is preferably 100,000 or more and 400,000 or less, more preferably 150,000 or more and 370000 or less, and 200,000 or more and 300,000 or less. Is more preferable.
From the same viewpoint, the number average molecular weight Mn of cellulose acylate is preferably 20000 or more and 300000 or less, more preferably 50000 or more and 250,000 or less, and further preferably 70000 or more and 200000 or less.
The mass average molecular weight and number average molecular weight of cellulose acylate can be measured by gel permeation chromatography.

  Furthermore, regarding the molecular weight distribution of cellulose acylate, it is preferable that the polydispersity index Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is small and the molecular weight distribution is narrow. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 1.3 to 3.7, and most preferably 1.6 to 3.4. preferable.

  When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (narrow molecular weight distribution) can be synthesized. When used in the production of the cellulose acylate film of the present invention, the moisture content of the cellulose acylate is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7%. It is below mass%. In general, cellulose acylate contains water, and its water content is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate as described above in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content is obtained. Regarding these cellulose acylates of the present invention, the raw material cotton and the synthesis method thereof are disclosed on the 7th to 12th pages of the Japan Society for Invention and Innovation (public technical number 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is described in detail.

  In the present invention, cellulose acylate can be used by mixing two or more different types of cellulose acylates from the viewpoint of substituents, substitution degree, polymerization degree, molecular weight distribution, and the like.

[Retardation]
The cellulose acylate film of the present invention has an in-plane retardation (Re) defined by the following formula (I) at a wavelength of 590 nm in an environment of 25 ° C. and 60% RH of −5 to 5 nm, and the following formula (II) The retardation (Rth) in the thickness direction defined by is -10 to 5 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the film (Nm).
Re is more preferably 0 nm to 5 nm. Rth is more preferably −10 to 3 nm, and further preferably −5 to 2 nm. When the cellulose acylate film of the present invention is used as a protective film on the liquid crystal cell side of a polarizing plate of a liquid crystal display device, when Re and Rth are in the above ranges, light leakage and color change from an oblique direction are further improved, Display quality can be improved.
The absolute value ΔRth of the difference between the Rth value at 25 ° C. and 80% RH and the 25 ° C. and 10% RH value at a wavelength of 590 nm is preferably 0 to 10, more preferably 0 to 5, More preferably, it is ~ 3. When ΔRth is within this range, the light unevenness from the oblique direction is further improved, and the display quality can be improved.

Re and Rth can be measured as follows.
Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH is calculated based on the retardation value measured in the direction. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness.

[Matting agent fine particles]
It is preferable to add fine particles as a matting agent to the cellulose acylate film of the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film.
The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle size is preferably from 0.2 to 1.5 μm, more preferably from 0.4 to 1.2 μm, and most preferably from 0.6 to 1.1 μm. The primary and secondary particle sizes were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the turbidity of the optical film low. It is particularly preferable because it has a great effect of reducing the effect.

In order to obtain a cellulose acylate film having particles having a small secondary average particle size in the present invention, several methods are conceivable when preparing a fine particle dispersion. For example, a method of preparing a fine particle dispersion in which a solvent and fine particles are stirred and mixed in advance, adding this fine particle dispersion to a small amount of cellulose acylate solution separately prepared, stirring and dissolving, and further mixing with the main cellulose acylate dope solution There is. This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose acylate to the solvent and dissolving with stirring, add fine particles to this and disperse with a disperser to make this fine particle additive solution, which is sufficiently mixed with the dope solution using an in-line mixer. There is also a method of mixing. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The addition amount of the matting agent in the final cellulose acylate dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and 0.08 to 0.16 g per 1 m ^2. Most preferred. Further, when the cellulose acylate film is formed from multiple layers, it is preferably not added to the inner layer, but only to the surface layer side. In this case, the amount of the matting agent added to the surface layer is 0.001% by mass. The content is preferably 0.2% by mass or less and more preferably 0.01% by mass or more and 0.1% by mass or less.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate.

[Method for producing cellulose acylate film]
The cellulose acylate film of the present invention can be formed by a solution casting method. Hereinafter, the method for producing a polymer film of the present invention will be described with reference to a film formed by using cellulose acylate as a thermoplastic polymer (referred to as “cellulose acylate film”).

(Organic solvent for cellulose acylate solution)
In the present invention, it is preferable to produce a cellulose acylate film by a solution casting method (solvent cast method), and the film is produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent. The organic solvent preferably used as the main solvent of the present invention is preferably a solvent selected from esters, ketones, ethers having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 7 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent. It may have a functional group of

  For the cellulose acylate film according to the present invention, a chlorinated halogenated hydrocarbon may be used as a main solvent, and as described in JIII Journal of Technical Disclosure 2001-1745 (pages 12 to 16), A non-chlorine solvent may be used as the main solvent, and is not particularly limited to the cellulose acylate film according to the present invention.

  In addition, the solvent for the cellulose acylate solution and the film according to the present invention is disclosed in the following patents, including its dissolution method, and is a preferred embodiment. They are, for example, JP 2000-95876, JP 12-95877, JP 10-324774, JP 8-152514, JP 10-330538, JP 9-95538, JP 9-95557, JP 10-10. -235664, JP-A-12-63534, JP-A-11-21379, JP-A-10-182853, JP-A-10-278056, JP-A-10-279702, JP-A-10-323853, JP-A-10-237186, JP-A-11-60807. JP-A-11-152342, JP-A-11-292988, JP-A-11-60752, JP-A-11-60752, and the like. According to these patents, not only the preferred solvent for the cellulose acylate according to the present invention but also the physical properties of the solution and the coexisting substances to be coexisted are described, which is also a preferred embodiment in the present invention.

(Dissolution process)
Preparation of the cellulose acylate solution (dope) according to the present invention is not particularly limited in its dissolution method, and may be performed at room temperature, and further, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. Regarding the preparation of the cellulose acylate solution in the present invention, and further on the steps of solution concentration and filtration accompanying the dissolving step, the technical report of the Japan Society of Invention (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention) The manufacturing process described in detail on pages 22 to 25 is preferably used.

(Casting, drying, winding process)
Next, the method for producing a film using the cellulose acylate solution according to the present invention will be described more specifically. As a method and equipment for producing a cellulose acylate film according to the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film can be used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as a polymer web) is peeled off from the metal support at a peeling point which is uniformly cast on the metal support and substantially rounds the metal support. The both ends of the obtained web are sandwiched between clips, transported by a tenter while holding the width and dried, and then the obtained film is mechanically transported by a roll group of a drying device, dried, and then rolled by a winder. Wind up to a predetermined length. The combination of the tenter and the roll group dryer varies depending on the purpose. As another embodiment, the metal support described above is a drum cooled to 0 ° C. or less, and the dope cast from the die is gelled on the drum and then peeled off after about one turn, and stretched with a pin-shaped tenter. Various methods for forming a film by a solvent cast method, such as a method of transporting and drying the solution, can be used.

Since the cellulose acylate film according to the present invention contains a specific polyester-based oligomer in an amount of more than 30 mass, the polymer web can be dried at 80 ° C. or less, and the load in the drying process can be reduced. it can. 50-80 degreeC is preferable and, as for the temperature at the time of drying (film surface temperature of a polymer web), 60-75 degreeC is more preferable. The drying time is preferably 5 to 60 minutes, more preferably 10 to 30 minutes.
The amount of residual solvent in the polymer web after drying is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass.

  In the solution casting film-forming method used for the functional polarizing plate protective film and the silver halide photographic light-sensitive material, which are optical members for electronic displays, which is the main use of the cellulose acylate film according to the present invention, solution casting In addition to the film forming apparatus, a coating apparatus is often added for surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, and a protective layer. These are described in detail on pages 25 to 30 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Inventions). Including), metal support, drying, peeling and the like, and can be preferably used in the present invention.

[Film thickness]
The thickness of the cellulose acylate film of the present invention is 15 to 35 μm, preferably 15 to 30 μm, and particularly preferably 15 to 25 μm. If thickness is 35 micrometers or less, it is easy to control the retardation (Rth) of a thickness direction to -10-5 nm, and it is preferable. Moreover, if thickness is 15 micrometers or more, a fracture | rupture and wrinkle generation | occurrence | production can be suppressed and it is preferable at the point of handling of a film.

[Haze of film]
The transparency of the film is important as an optical film, and the haze of the cellulose acylate film of the present invention is preferably as small as possible, preferably 0.01 to 2.0%. More preferably, it is 1.0% or less, More preferably, it is 0.5% or less. The haze can be measured by measuring the cellulose acylate film sample 40 mm × 80 mm of the present invention at 25 ° C. and 60% RH in accordance with JIS K-6714 using a haze meter (HGM-2DP, Suga Test Instruments). it can.

[Spectral characteristics, Spectral transmittance]
A transmittance of a cellulose acylate film sample 13 mm × 40 mm at a wavelength of 300 to 450 nm can be measured with a spectrophotometer “U-3210” {Hitachi, Ltd.} at 25 ° C. and 60% RH. The inclination width can be obtained at a wavelength of 72% -5%. The limiting wavelength can be represented by a wavelength of (gradient width / 2) + 5%, and the absorption edge can be represented by a wavelength having a transmittance of 0.4%. From this, the transmittances at 380 nm and 350 nm can be evaluated.
When the cellulose acylate film of the present invention is used on the opposite side of the protective film facing the liquid crystal cell of the polarizing plate, the spectral transmittance at a wavelength of 380 nm measured by the above method is 45% or more and 95% or less, and The spectral transmittance at a wavelength of 350 nm is preferably 10% or less.

[Glass-transition temperature]
The glass transition temperature of the cellulose acylate film of the present invention is preferably 120 ° C. or higher, and more preferably 140 ° C. or higher.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.
Moreover, the measurement of a glass transition temperature can also be calculated | required using the following dynamic viscoelasticity measuring apparatuses. After adjusting the cellulose acylate film sample (unstretched) 5 mm × 30 mm of the present invention at 25 ° C. and 60% RH for 2 hours or more, a dynamic viscoelasticity measuring device (Vibron: DVA-225 (IT Measurement Control Co., Ltd.) Manufactured))), measured at a distance between grips of 20 mm, a heating rate of 2 ° C./minute, a measurement temperature range of 30 ° C. to 250 ° C., and a frequency of 1 Hz, the logarithmic axis is the storage elastic modulus, and the horizontal axis is the linear axis is the temperature. When taking (° C.), the straight line 1 was drawn in the solid region, and the straight line 2 was drawn in the glass transition region, when the storage elastic modulus transitioned from the solid region to the glass transition region. The intersection of the straight line 1 and the straight line 2 is the temperature at which the storage elastic modulus suddenly decreases and the film begins to soften when the temperature rises, and the temperature at which the film begins to move to the glass transition region. Viscoelasticity) .

[Equilibrium moisture content of film]
The water content (equilibrium water content) of the cellulose acylate film of the present invention is not limited regardless of the film thickness so as not to impair the adhesion with a water-soluble polymer such as polyvinyl alcohol when used as a protective film for a polarizing plate. The water content at 25 ° C. and 80% RH is preferably 0 to 4% by mass. More preferably, it is 0.1-3.5 mass%, and it is especially preferable that it is 1-3 mass%. When the equilibrium moisture content is 4% by mass or less, it is preferable that the dependency of retardation due to humidity change does not become too large when used as a support for an optical compensation film.
The water content was measured by using a cellulose acylate film sample of 7 mm × 35 mm according to the present invention with a moisture meter, a sample drying apparatus “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation) and Karl Fischer. Measured by the method. It was calculated by dividing the amount of water (g) by the sample mass (g).

[Water permeability of film]
The moisture permeability of the film is measured under conditions of 60 ° C. and 95% RH based on JIS Z-0208.
The moisture permeability decreases as the thickness of the cellulose acylate film increases, and increases as the thickness decreases. Therefore, for samples having different film thicknesses, it is necessary to convert the reference to 80 μm. The film thickness can be converted according to the following mathematical formula.
Formula: Moisture permeability in terms of 80 μm = measured moisture permeability × measured film thickness (μm) / 80 (μm)
The measurement method of water vapor transmission rate is “Polymer Physical Properties II” (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294 “Measurement of vapor permeation amount (mass method, thermometer method, vapor pressure method, adsorption amount method) Can be applied.
The moisture permeability of the cellulose acylate film of the present invention is preferably 400~5000g ^/ m 2 ^/ 24h. More preferably 400~4000g ^/ m 2 ^/ 24h, and particularly preferably 400~3500g ^/ m 2 ^/ 24h. If moisture permeability less 4000g ^/ m 2 ^/ 24h, Re value of the film, the absolute value of humidity dependency of Rth value without causing inconvenience such as greater than RH 0.5 nm /%, preferably.

[Changes in film dimensions]
The dimensional stability of the cellulose acylate film of the present invention is as follows: dimensional change rate after standing for 24 hours under conditions of 60 ° C. and 90% RH (high humidity), and conditions of 90 ° C. and 5% RH It is preferable that the dimensional change rate after standing for 24 hours (high temperature) is 0.5% or less.
More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.
ing.

[Elastic modulus of film]
Since the thickness of the cellulose acylate film of the present invention is as thin as 15 to 35 μm, it is preferable because the roll film can be easily handled when the tensile elastic modulus is in an appropriate range.
The preferable range of the tensile modulus of the cellulose acylate film of the present invention is 4.0 to 7.0 GPa, more preferably 4.5 to 6.0 GPa.
As a specific measurement method, using a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd., the stress at 0.5% elongation was measured at 23 ° C. and 60 RH% atmosphere at a tensile rate of 10% / min. Find the elastic modulus.

[Photoelastic coefficient]
When the cellulose acylate film of the present invention is used as a polarizing plate protective film, birefringence (Re, Rth) may change due to stress caused by the contraction of the polarizer. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 Br or less, more preferably −3 to 12 Br, and further preferably 0 to 11 Br. preferable.

[Contact angle of film surface by alkali saponification]
One effective means of surface treatment when the cellulose acylate film of the present invention is used as a polarizing plate protective film is alkali saponification treatment. In this case, the contact angle of the film surface after the alkali saponification treatment is preferably 55 ° or less. More preferably, it is 50 ° or less, and further preferably 45 ° or less.

[surface treatment]
The cellulose acylate film can achieve improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs in a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail in pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention), and are preferably used in the present invention. be able to.

[Functional layer]
The cellulose acylate film of the present invention is applied as, for example, an optical application and a photographic photosensitive material. In particular, the optical application is preferably a liquid crystal display device, and the liquid crystal display device has a liquid crystal cell in which liquid crystal is supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and the liquid crystal It is more preferable that at least one optical compensation sheet is disposed between the cell and the polarizer. As these liquid crystal display devices, TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN are preferable.
In that case, when using the cellulose acylate film of this invention for the above-mentioned optical use, providing various functional layers is implemented. These are, for example, an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optical compensation layer, an alignment layer, a liquid crystal layer, and the like. Examples of these functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical Number 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

[Polarizer]
The use of the cellulose acylate film of the present invention will be described.
When the cellulose acylate film of the present invention is used as an optical film, it is particularly useful for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed.
Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.
The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since the polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, the polarizing plate protective film is particularly preferably used in this portion.

(General liquid crystal display device configuration)
When the cellulose acylate film is used as an optical compensation film, the transmission axis of the polarizer and the slow axis of the optical compensation film made of the cellulose acylate film may be arranged at any angle. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizers disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizer. The optical compensation film is arranged.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.

(Types of liquid crystal display devices)
The cellulose acylate film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Liquid BTS). Various display modes such as ECB (Electrically Controlled Birefringence) and HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose acylate film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

(IPS liquid crystal display device)
The cellulose acylate film of the present invention is also particularly advantageously used as a protective film for a polarizing plate of an IPS liquid crystal display device having an IPS mode liquid crystal cell. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the cellulose acylate film of the present invention is effective in reducing changes in color and contrast depending on the viewing angle.
Moreover, although the retardation (Rth) in the thickness direction of the cellulose acylate film of the present invention is -10 to 5 nm, in the region of 450 to 650 nm, Rth is 0 nm or less, the change in color is small, Particularly preferred.

  Among the protective films of the polarizing plate above and below the liquid crystal cell, the cellulose acylate film of the present invention is provided on at least one side of the liquid crystal cell as a protective film (cell side protective film) disposed between the liquid crystal cell and the polarizer. It is preferable to use it on both sides. In addition, an optically anisotropic layer in which the retardation value of the optically anisotropic layer is set to not more than twice the value of Δn · d of the liquid crystal layer is disposed on one side between the protective film of the polarizing plate and the liquid crystal cell. May be.

The features of the present invention will be described more specifically with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Sample No. Examples of “present invention” using 6, 7, 10-13 shall be read as “reference examples”.
<< 1 >> Manufacture and Evaluation of Optical Film A film was manufactured using the following materials and manufacturing method.
(Preparation of polymer solution)
1] Cellulose acylate Cellulose acylate (acetylcellulose) having different degrees of substitution of acetyl groups described in Table 4 was used. Each cellulose acylate was heated to 120 ° C. and dried to adjust the water content to 0.5% by mass or less, and then 20 parts by mass was used. The number average molecular weight of the cellulose acylate used was in the range of 90,000 to 13,0000.

2] Solvent A mixed solvent of dichloromethane / methanol = 87/13 (mass ratio) was used. The water content was 0.2% by mass or less.

3] Additive (Additive A: Polyester oligomer)
Polyester oligomers 101 to 106 having the composition shown in Table 3 below (dicarboxylic acid and diol used in molar ratios shown in Table 3 below), number average molecular weight (Mn), and terminal structure were used.

  In the terminal structure, AcO is sealed with an acetyl group. For example, polyester 101 represents a polyester oligomer obtained by reacting adipic acid and ethylene glycol at 50/50 (molar ratio) and sealing with acetyl groups.

(Additive B: sugar ester compound)
The sugar ester compound M-1 described in Table 1 and the sugar ester compounds D-1 and D-5 described in Table 2 were used. Moreover, sucrose benzoate (8 substitution) was used as the comparison compound C-1.

4] Preparation of polymer solution The following composition was put into a mixing tank and stirred to dissolve each component to prepare a polymer solution.
(Addition amount of each component)
-Cellulose acylate (degree of substitution described in Table 4) 20 parts by mass-Mixed solvent 100 parts by mass-Polyester oligomer Amount described in Table 4 (% by mass relative to cellulose acylate)
Sugar ester compounds Amounts listed in Table 4 (mass% with respect to cellulose acylate)
・ Silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) 0.02 parts by mass

(Production of film)
The polymer solution was filtered using a filter paper having an average pore diameter of 34 μm and a sintered metal filter having an average pore diameter of 10 μm, and then cast using a band casting machine. The film was peeled off from the band with a residual solvent amount of 30%, and the drying temperature and time were appropriately adjusted so that the residual solvent amount of the resulting film was 0.2% or less, to prepare a film. The film thickness of the obtained film was as shown in Table 4.

The tensile elastic modulus of the cellulose acylate films of Examples and Comparative Examples was measured using a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd. at 23 ° C. and a relative humidity of 60% at a tensile rate of 10% / min. The stress at 0.5% elongation was measured, and the average values of the tensile modulus of MD and TD were listed in the table.
Since the cellulose acylate film of the present invention has a thickness of 15 to 35 μm, it is easy to handle a roll film when its tensile elastic modulus is in an appropriate range. 0 to 7.0 GPa, more preferably 4.5 to 6.0 GPa.

<< 2 >> Preparation and evaluation of polarizing plate (Preparation of polarizing plate)
1] Saponification of Film Each film prepared in Examples and Comparative Examples and FUJITAC TD40UC (manufactured by FUJIFILM Corporation) were heated in a 4.5 mol / L sodium hydroxide aqueous solution (saponification solution) adjusted to 37 ° C. for 1 minute. After dipping, the film was washed with water, then dipped in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, and then passed through a water washing bath. Then, draining with an air knife was repeated three times, and after dropping the water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film.

2] Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls and stretched in the longitudinal direction to prepare a polarizing film having a thickness of 20 μm.

3] Bonding After selecting two polarizing films from the polarizing film thus obtained and the saponified film and sandwiching the polarizing film therebetween, PVA (manufactured by Kuraray Co., Ltd., PVA-117H) 3% Using an aqueous solution as an adhesive, a polarizing plate was prepared by laminating with a roll-to-roll so that the polarization axis and the longitudinal direction of the film were orthogonal to each other. Here, one film of the polarizing film was a saponified film selected from the film group described in Table 4, and the other film was a saponified film of Fujitac TD40UC.

<< 3 >> Mounting evaluation to liquid crystal display device (mounting to IPS liquid crystal display device)
The polarizing plate sandwiching the liquid crystal cell is peeled off from the commercially available liquid crystal television (IPS mode slim 42-inch liquid crystal television), and the film described in Table 4 is placed on the liquid crystal cell side. Thus, it re-bonded to the liquid crystal cell through the adhesive. The display characteristics of the reassembled liquid crystal television were confirmed, and the luminance and color from the front and oblique directions were confirmed. In the polarizing plate produced using the film of 5, 8, 9, and 18, it was confirmed that the color change when observed from an oblique direction was large and the display characteristics were inferior. (Display performance B in the table) The other polarizing plates showed the same characteristics as before the polarizing plate was peeled off. (In the table, display performance A)

4] Polarizing plate durability evaluation About the polarizing plate produced above, two sets (about 5 cm x 5 cm) of the sample (about 5 cm x 5 cm) which stuck the cellulose acylate film side of each Example and the comparative example to the glass plate with the adhesive were produced. . This was placed in crossed Nicol, and the orthogonal transmittance was measured at 410 nm using UV3100PC (manufactured by Shimadzu Corporation), and the average value of 10 measurements was defined as the orthogonal transmittance (%).
Thereafter, the orthogonal transmittance after storage for 500 hours in an environment of 60 ° C. and 95% relative humidity was measured by the above method. The evaluation value of the polarizing plate durability is defined as follows.
Evaluation value of polarizing plate durability = [orthogonal transmittance after time (%) − orthogonal transmittance before time (%)] / orthogonal transmittance before time (%)
The results are shown in Table 4 above with the evaluation value as the polarizing plate durability. The smaller the evaluation value of the polarizing plate durability, the better.

As is clear from the results shown in Table 4, polyester oligomer 101 or 102 (molar ratio of aromatic dicarboxylic acid component is outside the scope of the present invention) alone (sample No. 1, 2), sugar It can be seen that the films (sample Nos. 3 and 4) in which the molar ratio of the aromatic dicarboxylic acid component in the polyester oligomer is outside the range of the present invention (Sample Nos. 3 and 4) were greatly inferior in polarizing plate durability even when the ester compound was contained. It can be seen that the films (samples Nos. 5, 8, and 18) containing the polyester oligomers 103 and 104 or the ester compound M-1 alone had large Rth and poor display characteristics.
It can be seen that the film (sample No. 9) using the sugar ester compound outside the scope of the present invention also had a large Rth and inferior display characteristics.
On the other hand, in the film which is an example to which any of the polyester oligomers 103 to 106 and any of the sugar ester compounds M-1, D-1, and D-5 is added, the initial display characteristics are excellent and the polarizer durability is improved. It can be seen that a high elastic modulus that facilitates handling can be achieved even with a thin film thickness of 25 μm.

Claims (16)

Each contains one or more of the following additives (A) and (B),
In an environment with a temperature of 25 ° C. and a relative humidity of 60%, the in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm, the retardation in the thickness direction (Rth) is −10 to 5 nm, and the thickness is 15 to 35 μm. Cellulose acylate film.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic When the molar ratio of the group dicarboxylic acid is n, m: n is from 2: 8 to 0:10, and the polyester oligomer and additive (B) have 1 to 12 at least one kind of pyranose structure or furanose structure. , Sugar ester compounds in which all or part of the hydroxyl groups in the structure are alkylesterified   The additive (B) is a sugar ester compound having one or two pyranose structures or furanose structures and alkyl esterifying all or part of the hydroxyl groups of the structure. The cellulose acylate film described.   The cellulose acylate film according to claim 2, wherein the additive (B) is a monoester ring having a pyranose structure or a furanose structure, and is a sugar ester compound obtained by alkyl esterifying all or part of the hydroxyl groups of the structure.   The cellulose acylate film according to claim 3, wherein the additive (B) is a sugar ester compound obtained by alkyl esterifying all or part of hydroxyl groups of a glucose structure.   The cellulose acylate film according to any one of claims 1 to 4, wherein the total content of the additives (A) and (B) is 5 to 20 mass% with respect to the cellulose acylate. Wherein the polyester oligomer, the cellulose acylate film according to any one of claims 1 to 5 which is a Porisuteru oligomer sealing the at least one end with monocarboxylic acids.   The cellulose acylate film according to claim 6, wherein the monocarboxylic acid is an aliphatic monocarboxylic acid having 2 to 10 carbon atoms. Each contains one or more of the following additives (A) and (B),
  In an environment with a temperature of 25 ° C. and a relative humidity of 60%, the in-plane retardation (Re) at a wavelength of 590 nm is −5 to 5 nm, the retardation in the thickness direction (Rth) is −10 to 5 nm, and
  A cellulose acetate film having a thickness of 15 to 35 μm.
Additive (A): a polyester oligomer having a repeating unit composed of a dicarboxylic acid and a diol and having a number average molecular weight of 500 to 3000, wherein the molar ratio of the aliphatic dicarboxylic acid is m, aromatic Polyester oligomer in which m: n is 5: 5 to 0:10, where n is the molar ratio of the group dicarboxylic acid
Additive (B): a sugar ester compound having 1 to 12 at least one pyranose structure or furanose structure and alkylating all or part of the hydroxyl groups of the structure The cellulose acetate film according to claim 8, wherein in the cellulose acetate, the total degree of acyl substitution to the hydroxyl group of cellulose is 2.80 to 2.95. The said dicarboxylic acid contains the said polyester oligomer whose m: n is 2: 8-0: 10, when the molar ratio of aliphatic dicarboxylic acid is m and the molar ratio of aromatic dicarboxylic acid is n. Or the cellulose acetate film according to 9.   The cellulose acetate film according to claim 8, wherein the additive (B) is a sugar ester compound which is a monocyclic ring having a pyranose structure or a furanose structure, and all or part of the hydroxyl groups in the structure are alkylesterified.   The cellulose acetate film of any one of Claims 8-11 whose sum total of content of the said additive (A) and (B) is 5-20 mass% with respect to a cellulose acetate.   The cellulose acetate film according to any one of claims 8 to 12, wherein the polyester oligomer is a polyester oligomer having at least one end sealed with a monocarboxylic acid. A polarizing plate comprising at least one cellulose acylate film according to any one of claims 1 to 7 or a cellulose acetate film according to any one of claims 8 to 13 . A liquid crystal display device comprising the polarizing plate according to claim 14 . The liquid crystal display device according to claim 15 , which is in an IPS mode.