JP2006071876A - Cellulose ester film, optical compensation film, polarizing plate and liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester-based optical compensation film which has extremely stable display quality by suppressing changes in the retardation value due to humidity and which has no defect such as bleed-out of a plasticizer or the like. <P>SOLUTION: The cellulose ester film is formed by flow casting and drying a coating liquid containing 100 parts by mass of a cellulose ester, 0.1 to 20 parts by mass of a retardation enhancing agent, 4 to 30 parts by mass of a crosslinking agent and a solvent. The film shows 20 to 70 nm Re retardation value expressed by formula (I): Re=(nx-ny)×d and 70 to 400 Rth retardation expressed by formula (II): Rth=ä(nx+ny)/2-nz}×d, wherein nx represents the refractive index in the slow phase axis direction within the film plane, ny represents the refractive index in the fast phase axis direction within the film plane, nz represents the refractive index in the film thickness direction, and d represents the film thickness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cellulose ester film and an optical compensation film using the same.

  In recent years, the development of thin and light notebook PCs and thin and large-screen TVs has progressed, and accordingly, the protective film for polarizing plates used in display devices such as liquid crystal display devices has become increasingly thinner, larger and higher performance. The demand for is getting stronger. Among them, the liquid crystal display device has hitherto been a problem that the viewing angle is narrow. In order to expand the viewing angle of a liquid crystal display device, a method using an optical compensation film has been proposed (see, for example, Patent Documents 1 to 5).

  On the other hand, cellulose ester has been recognized as a support having excellent transparency and low retardation, but recently, studies have been made to increase optical anisotropy, and as a retardation increasing agent, A discotic compound (see, for example, Patent Document 6), and a change in display (contrast, tint, gradation) depending on the viewing angle, in particular, a rod-shaped compound for introducing a tint change (for example, Patent Document) 7), or, in addition to these retardation-increasing agents, a specific amount of an ethylenically unsaturated monomer is contained and polymerized to provide excellent resistance to fluctuations due to distortion such as heat (for example, Patent Document 8). See.)

  Although the problem could be improved to some extent by using the above means, the retardation value still varies depending on the humidity, that is, the display quality of the liquid crystal display varies depending on the use environment. Therefore, there is a need for technical means that can solve this problem.

In particular, when a polarizing plate using the above-mentioned optical compensation film as a protective film is attached to a large panel of 17 inches or more, it has been found that light leakage due to humidity fluctuation is not completely eliminated. In addition, the optical compensation film needs not only to have a function of optically compensating the liquid crystal cell but also to be excellent in durability due to a change in use environment.
JP-A-4-229828 JP-A-4-258923 JP-A-6-75116 JP-A-6-174920 JP-A-6-222213 JP 2001-166144 A JP 2002-267847 A JP 2004-26925 A

  Accordingly, an object of the present invention is to provide a cellulose-based optical compensation film having a very stable display quality by suppressing fluctuation of the retardation value due to humidity, which is a defect of the conventional cellulose-based optical compensation film. Another object of the present invention is to provide a cellulose optical compensation film free from defects caused by bleeding out of a plasticizer or the like even when used for a long time.

  The above problem could be solved by the following configuration.

(Claim 1)
A coating solution containing 0.01 to 20 parts by mass of a retardation increasing agent with respect to 100 parts by mass of the cellulose ester and 4 to 30 parts by mass of a crosslinking agent and a solvent with respect to 100 parts by mass of the cellulose ester. A cellulose ester film formed by casting and drying, wherein the Re retardation value defined by the following formula (I) is in the range of 20 to 70 nm, and the Rth retardation defined by the following formula (II): A cellulose ester film having a value in the range of 70 to 400 nm.
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
(Where 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 It is the thickness of the film.)
(Claim 2)
The cellulose ester film according to claim 1, which is a cellulose ester that simultaneously satisfies the following formulas (III), (IV), and (V).
(III) 2.0 <X + Y <3.0
(IV) 1.4 ≦ X <3.0
(V) 0 ≦ Y ≦ 1.2
(In the formula, X is the degree of substitution with an acetyl group, and Y is the degree of substitution with an acyl group having 3 to 22 carbon atoms.)
(Claim 3)
The cellulose ester film according to claim 1 or 2, wherein the crosslinking agent is an isocyanate-based crosslinking agent.

(Claim 4)
An optical compensation film using the cellulose ester film according to claim 1.

(Claim 5)
A polarizing plate comprising the optical compensation film according to claim 4 as a polarizing plate protective film on at least one surface.

(Claim 6)
A liquid crystal display device comprising the polarizing plate according to claim 5.

  According to the present invention, it is possible to provide a cellulose-based optical compensation film that suppresses humidity fluctuations of a cellulose ester film and has extremely stable display quality.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The cellulose ester film of the present invention contains 0.01 to 20 parts by mass of a retardation increasing agent with respect to 100 parts by mass of the cellulose ester, and 4 to 30 parts by mass of a crosslinking agent with respect to 100 parts by mass of the cellulose ester. A coating solution (also referred to as a dope) containing a solvent and a solvent is cast on a drum or an endless band, evaporated to a certain area, then peeled off from the drum or the endless band, dried by heating, By stretching in the direction (also referred to as the TD direction) and the longitudinal direction (MD direction), a cellulose ester film crosslinked with a crosslinking agent in a specific range having a retardation value is obtained.

  As a result, the environmental influence can be reduced by making it less susceptible to the influence of humidity, and a highly durable optical compensation film can be obtained.

  The retardation value can be measured using an automatic birefringence measuring apparatus (trade name KOBRA-21ADH manufactured by Oji Scientific Instruments).

  Hereinafter, the present invention will be described in detail for each element.

<Cellulose ester>
The cellulose ester used in the cellulose ester film of the present invention is preferably a fatty acid ester of cellulose. The fatty acid in the fatty acid ester of cellulose means a fatty acid having 2 to 22 carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate, etc. Further, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate as described in US Pat. No. 2,319,052 can be used. Among the above description, cellulose esters particularly preferably used are cellulose triacetate and cellulose acetate propionate. These cellulose esters can be used alone or in combination.

  In the case of cellulose triacetate, those having an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5% are preferably used, and more preferably cellulose having an average degree of acetylation of 58.0 to 62.5%. Triacetate.

Preferred cellulose esters other than cellulose triacetate have an acyl group having 2 to 22 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of fatty acid having 3 to 22 carbon atoms is Y. It is a cellulose ester that simultaneously satisfies the following formulas (III), (IV), and (V).
(III) 2.0 <X + Y <3.0
(IV) 1.4 ≦ X <3.0
(V) 0 ≦ Y ≦ 1.2
Among them, cellulose acetate propionate having 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 is preferable. The portion not substituted with an acyl group usually exists as a hydroxyl group and is a group capable of reacting with the crosslinking agent of the present invention. These cellulose esters can be synthesized by a known method.

  As the cellulose ester, cellulose ester synthesized from cotton linter, wood pulp, kenaf or the like as a raw material can be used alone or in combination. In particular, it is preferable to use a cellulose ester synthesized from cotton linter (hereinafter sometimes referred to simply as linter) alone or in combination.

  If the molecular weight of the cellulose ester is large, the rate of change of the retardation value due to humidity becomes small. However, if the molecular weight is excessively increased, the viscosity of the cellulose ester solution becomes too high and the productivity is lowered. The molecular weight of the cellulose ester is preferably 70000-200000 in terms of number average molecular weight (Mn), more preferably 70000-170000.

  Furthermore, the cellulose ester used in the present invention is preferably a cellulose ester having a weight average molecular weight (Mw) / number average molecular weight (Mn) value of 1.4 to 3.0. Preferably it is the range of 1.7-2.2.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using these, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable to obtain 13 samples at approximately equal intervals.

<Retardation raising agent>
The cellulose ester film of the present invention contains a retardation increasing agent.

  Conventionally, in order to obtain a cellulose ester film having a high retardation value, it has been necessary to perform longitudinal or transverse stretching until just before breakage at the time of film formation. Alternatively, by containing a discotic compound, a compound capable of achieving a Re retardation value of 20 to 70 nm and an Rth retardation value of 70 to 400 nm even when the draw ratio is about 1.0 to 1.2 is found. The present invention is characterized by containing such a retardation increasing agent.

  Hereinafter, specific retardation increasing agents will be described.

<Bar compound>
The cellulose ester film of the present invention preferably contains a rod-like compound having a maximum absorption wavelength (λmax) of the ultraviolet absorption spectrum of the solution shorter than 250 nm as a retardation increasing agent.

  From the viewpoint of the function of the retardation increasing agent, the rod-like compound preferably has at least one aromatic ring, and more preferably has at least two aromatic rings. The rod-like compound preferably has a linear molecular structure. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation is performed using molecular orbital calculation software (for example, WinMOPAC2000, manufactured by Fujitsu Limited), and a molecular structure that minimizes the heat of formation of a compound can be obtained. The molecular structure being linear means that the angle of the molecular structure is 140 degrees or more in the thermodynamically most stable structure obtained by calculation as described above. The rod-shaped compound preferably exhibits liquid crystallinity. More preferably, the rod-like compound exhibits liquid crystallinity upon heating (has thermotropic liquid crystallinity). The liquid crystal phase is preferably a nematic phase or a smectic phase.

  The rod-like compound is preferably a trans-1,4-cyclohexanedicarboxylic acid ester compound represented by the following general formula (2).

Formula (2) Ar ¹ -L ¹ -Ar ²
In formula (2), Ar ¹ and Ar ² are each independently an aromatic group. In the present specification, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group. An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group. The heterocycle of the aromatic heterocyclic group is generally unsaturated. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine Rings, pyridazine rings, pyrimidine rings, pyrazine rings, and 1,3,5-triazine rings are included. As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of substituents for substituted aryl groups and substituted aromatic heterocyclic groups include halogen atoms (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, alkylamino groups (eg, methylamino, ethylamino) , Butylamino, dimethylamino), nitro, sulfo, carbamoyl, alkylcarbamoyl groups (eg, N-methylcarbamoyl, N-ethylcarbamoyl, N, N-dimethylcarbamoyl), sulfamoyl, alkylsulfamoyl groups (eg, N- Methylsulfamoyl, N-ethylsulfamoyl, N, N-dimethylsulfamoyl), ureido, alkylureido groups (eg, N-methylureido, N, N-dimethylureido, N, N, N′-trimethyl) Ureido), alkyl groups (eg, methyl, ethyl, propyl, butyl, pentyl, Butyl, octyl, isopropyl, s-butyl, t-amyl, cyclohexyl, cyclopentyl), alkenyl groups (eg, vinyl, allyl, hexenyl), alkynyl groups (eg, ethynyl, butynyl), acyl groups (eg, formyl, acetyl, Butyryl, hexanoyl, lauryl), acyloxy groups (eg, acetoxy, butyryloxy, hexanoyloxy, lauryloxy), alkoxy groups (eg, methoxy, ethoxy, propoxy, butoxy, pentyloxy, heptyloxy, octyloxy), aryloxy groups (Eg, phenoxy), alkoxycarbonyl group (eg, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, heptyloxycarbonyl), aryloxycarbo Group (eg, phenoxycarbonyl), alkoxycarbonylamino group (eg, butoxycarbonylamino, hexyloxycarbonylamino), alkylthio group (eg, methylthio, ethylthio, propylthio, butylthio, pentylthio, heptylthio, octylthio), arylthio group (eg, , Phenylthio), alkylsulfonyl groups (eg, methylsulfonyl, ethylsulfonyl, propylsulfonyl, butylsulfonyl, pentylsulfonyl, heptylsulfonyl, octylsulfonyl), amide groups (eg, acetamide, butylamide group, hexylamide, laurylamide) and non- Aromatic heterocyclic groups (eg, morpholyl, pyrazinyl) are included.

  Substituents for substituted aryl groups and substituted aromatic heterocyclic groups include halogen atoms, cyano, carboxyl, hydroxyl, amino, alkyl-substituted amino groups, acyl groups, acyloxy groups, amide groups, alkoxycarbonyl groups, alkoxy groups, alkylthios. And groups and alkyl groups are preferred. The alkyl moiety of the alkylamino group, alkoxycarbonyl group, alkoxy group, and alkylthio group and the alkyl group may further have a substituent. Examples of alkyl moieties and substituents of alkyl groups include halogen atoms, hydroxyl, carboxyl, cyano, amino, alkylamino groups, nitro, sulfo, carbamoyl, alkylcarbamoyl groups, sulfamoyl, alkylsulfamoyl groups, ureido, alkylureido Group, alkenyl group, alkynyl group, acyl group, acyloxy group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, alkylsulfonyl group, amide group and non-aromatic An aromatic heterocyclic group is included. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, hydroxyl, amino, alkylamino group, acyl group, acyloxy group, acylamino group, alkoxycarbonyl group and alkoxy group are preferable.

In Formula (2), L ¹ is a divalent linking group selected from the group consisting of an alkylene group, an alkenylene group, an alkynylene group, a divalent saturated heterocyclic group, —O—, —CO—, and combinations thereof. is there. The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group. The number of carbon atoms of the alkylene group is preferably 1-20, more preferably 1-15, still more preferably 1-10, still more preferably 1-8, 6 is most preferred.

  The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure. The number of carbon atoms in the alkenylene group and the alkynylene group is preferably 2 to 10, more preferably 2 to 8, still more preferably 2 to 6, and still more preferably 2 to 4. Most preferred is 2 (vinylene or ethynylene). The divalent saturated heterocyclic group preferably has a 3- to 9-membered heterocyclic ring. The hetero atom of the hetero ring is preferably an oxygen atom, a nitrogen atom, a boron atom, a sulfur atom, a silicon atom, a phosphorus atom or a germanium atom. Examples of saturated heterocycles include piperidine ring, piperazine ring, morpholine ring, pyrrolidine ring, imidazolidine ring, tetrahydrofuran ring, tetrahydropyran ring, 1,3-dioxane ring, 1,4-dioxane ring, tetrahydrothiophene ring, 1 , 3-thiazolidine ring, 1,3-oxazolidine ring, 1,3-dioxolane ring, 1,3-dithiolane ring and 1,3,2-dioxaborolane. Particularly preferred divalent saturated heterocyclic groups are piperazine-1,4-diylene, 1,3-dioxane-2,5-diylene and 1,3,2-dioxaborolane-2,5-diylene.

  The example of the bivalent coupling group which consists of a combination is shown.

L-1: —O—CO-alkylene group —CO—O—
L-2: -CO-O-alkylene group -O-CO-
L-3: —O—CO—alkenylene group —CO—O—
L-4: -CO-O-alkenylene group -O-CO-
L-5: -O-CO-alkynylene group -CO-O-
L-6: -CO-O-alkynylene group -O-CO-
L-7: -O-CO-divalent saturated heterocyclic group -CO-O-
L-8: -CO-O-divalent saturated heterocyclic group -O-CO-
In the molecular structure of the general formula (2), the angle formed by Ar ¹ and Ar ² across L ¹ is preferably 140 degrees or more. As the rod-like compound, a compound represented by the following general formula (3) is more preferable.

Formula (3) Ar ¹ -L ² -XL ³ -Ar ²
In Formula (3), Ar ¹ and Ar ² are each independently an aromatic group. The definition and examples of the aromatic group are the same as those of Ar ¹ and Ar ^{2 in} the formula (2).

In Formula (3), L ² and L ³ are each independently a divalent linking group selected from the group consisting of an alkylene group, —O—, —CO—, and combinations thereof. The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure. The number of carbon atoms of the alkylene group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, still more preferably 1 to 4, and 1 or Most preferred is 2 (methylene or ethylene). L ² and L ³ are particularly preferably —O—CO— or —CO—O—.

  In the formula (3), X is 1,4-cyclohexylene, vinylene or ethynylene. Specific examples of the compound represented by formula (2) are shown below.

  Specific examples (1) to (34), (41), (42), (46), (47), (52), (53) are two asymmetric carbons at the 1st and 4th positions of the cyclohexane ring. Has atoms. However, the specific examples (1), (4) to (34), (41), (42), (46), (47), (52), (53) have a symmetric meso type molecular structure. Therefore, there is no optical isomer (optical activity) and only geometric isomers (trans and cis forms) exist. The trans type (1-trans) and cis type (1-cis) of specific example (1) are shown below.

  As described above, the rod-like compound preferably has a linear molecular structure. Therefore, the trans type is preferable to the cis type. Specific examples (2) and (3) have optical isomers (a total of four isomers) in addition to geometric isomers. As for geometric isomers, the trans type is similarly preferable to the cis type. The optical isomer is not particularly superior or inferior, and may be D, L, or a racemate. In specific examples (43) to (45), the central vinylene bond includes a trans type and a cis type. For the same reason as above, the trans type is preferable to the cis type.

  Two or more rod-shaped compounds having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination. The rod-shaped compound can be synthesized with reference to methods described in the literature. As literature, Mol. Cryst. Liq. Cryst. 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 (1989); Am. Chem. Soc. 113, p. 1349 (1991), p. 118, p. 5346 (1996), p. 92, p. 1582 (1970). Org. Chem. 40, 420 (1975), Tetrahedron, 48, 16, 3437 (1992).

<Disc-like compound>
The cellulose ester of the present invention preferably contains a discotic compound as a retardation increasing agent.

  The discotic compound used in the present invention is a compound having a disc structure having a nucleus (for example, a benzene ring or a triazine ring) which is the center of the disc and extending from the central nucleus on a plane. In the present invention, a compound having a 1,3,5-triazine ring is particularly preferably used as the central nucleus.

  Among them, the compound having a 1,3,5-triazine ring is preferably a compound represented by the following general formula (4).

In the general formula (4), X ¹ is a single bond, —NR ₄ —, —O— or —S—; X ² is a single bond, —NR ₅ —, —O— or —S—; X ³ is a single bond, —NR ₆ —, —O— or —S—; R ¹ , R ² and R ³ are an alkyl group, an alkenyl group, an aryl group or a heterocyclic group; and R ₄ , R ₅ and R ₆ are a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group. The compound represented by the general formula (4) is particularly preferably a melamine compound.

In the melamine compound, in the general formula (4), X ¹ , X ² and X ³ are —NR ₄ —, —NR ₅ — and —NR ₆ —, respectively, or X ¹ , X ² and X 3 ³ is a single bond, and R ¹ , R ² and R ³ are heterocyclic groups having a free valence on the nitrogen atom. ^{-X 1 -R 1, -X 2 -R} 2 and -X ³ -R ³ are preferably the same substituents. R ¹ , R ² and R ³ are particularly preferably aryl groups. R ₄ , R ₅ and R ₆ are particularly preferably a hydrogen atom.

  The alkyl group is preferably a chain alkyl group rather than a cyclic alkyl group. A linear alkyl group is preferred to a branched alkyl group.

  The number of carbon atoms of the alkyl group is preferably 1-30, more preferably 1-20, still more preferably 1-10, still more preferably 1-8, 6 is most preferred. The alkyl group may have a substituent.

  Specific examples of the substituent include a halogen atom, an alkoxy group (for example, each group such as methoxy, ethoxy, and epoxyethyloxy) and an acyloxy group (for example, acryloyloxy, methacryloyloxy). The alkenyl group is preferably a chain alkenyl group rather than a cyclic alkenyl group. A linear alkenyl group is preferable to a branched chain alkenyl group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent.

  Specific examples of the substituent include a halogen atom, an alkoxy group (for example, each group such as methoxy, ethoxy, and epoxyethyloxy) or an acyloxy group (for example, each group such as acryloyloxy and methacryloyloxy).

  The aryl group is preferably a phenyl group or a naphthyl group, and particularly preferably a phenyl group. The aryl group may have a substituent.

  Specific examples of the substituent include, for example, a halogen atom, hydroxyl, cyano, nitro, carboxyl, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, alkenyloxy Carbonyl group, aryloxycarbonyl group, sulfamoyl, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamido group, carbamoyl, alkyl-substituted carmoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide group, alkylthio Groups, alkenylthio groups, arylthio groups and acyl groups are included. The said alkyl group is synonymous with the alkyl group mentioned above.

  The alkyl group of the alkoxy group, acyloxy group, alkoxycarbonyl group, alkyl-substituted sulfamoyl group, sulfonamido group, alkyl-substituted carbamoyl group, amide group, alkylthio group and acyl group is also synonymous with the alkyl group described above.

  The said alkenyl group is synonymous with the alkenyl group mentioned above.

  The alkenyl part of the alkenyloxy group, acyloxy group, alkenyloxycarbonyl group, alkenyl-substituted sulfamoyl group, sulfonamide group, alkenyl-substituted carbamoyl group, amide group, alkenylthio group and acyl group is also synonymous with the alkenyl group described above.

  Specific examples of the aryl group include phenyl, α-naphthyl, β-naphthyl, 4-methoxyphenyl, 3,4-diethoxyphenyl, 4-octyloxyphenyl, and 4-dodecyloxyphenyl. Can be mentioned.

  Examples of the aryloxy group, acyloxy group, aryloxycarbonyl group, aryl-substituted sulfamoyl group, sulfonamido group, aryl-substituted carbamoyl group, amide group, arylthio group, and acyl group are the same as the above aryl group.

When X ¹ , X ² or X ³ is —NR—, —O— or —S—, the heterocyclic group preferably has aromaticity.

  The heterocyclic ring in the heterocyclic group having aromaticity is generally an unsaturated heterocyclic ring, preferably a heterocyclic ring having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, a 6-membered ring or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 6-membered ring.

  The hetero atom in the heterocyclic ring is preferably each atom such as N, S or O, and particularly preferably an N atom.

  As the heterocyclic ring having aromaticity, a pyridine ring (as the heterocyclic group, for example, each group such as 2-pyridyl or 4-pyridyl) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent of the aryl moiety.

When X ¹ , X ² or X ³ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms.

  Moreover, the hetero atom in a heterocyclic group may have hetero atoms other than a nitrogen atom (for example, O atom, S atom). The heterocyclic group may have a substituent. Specific examples of the substituent of the heterocyclic group are the same as the specific examples of the substituent of the aryl moiety.

  Specific examples of the heterocyclic group having a free valence on the nitrogen atom are shown below.

  The molecular weight of the compound having a 1,3,5-triazine ring is preferably 300 to 2,000. The boiling point of the compound is preferably 260 ° C. or higher. The boiling point can be measured using a commercially available measuring device (for example, TG / DTA100, manufactured by Seiko Electronics Industry Co., Ltd.).

  Specific examples of the compound having a 1,3,5-triazine ring are shown below.

  In addition, several R shown below represents the same group.

(1) Butyl (2) 2-Methoxy-2-ethoxyethyl (3) 5-Undecenyl (4) Phenyl (5) 4-Ethoxycarbonylphenyl (6) 4-Butoxyphenyl (7) p-Biphenylyl (8) 4 -Pyridyl (9) 2-naphthyl (10) 2-methylphenyl (11) 3,4-dimethoxyphenyl (12) 2-furyl

(14) phenyl (15) 3-ethoxycarbonylphenyl (16) 3-butoxyphenyl (17) m-biphenylyl (18) 3-phenylthiophenyl (19) 3-chlorophenyl (20) 3-benzoylphenyl (21) 3 -Acetoxyphenyl (22) 3-benzoyloxyphenyl (23) 3-phenoxycarbonylphenyl (24) 3-methoxyphenyl (25) 3-anilinophenyl (26) 3-isobutyrylaminophenyl (27) 3-phenoxy Carbonylaminophenyl (28) 3- (3-ethylureido) phenyl (29) 3- (3,3-diethylureido) phenyl (30) 3-methylphenyl (31) 3-phenoxyphenyl (32) 3-hydroxyphenyl (33) 4-Ethoxycarbonylphenyl (34) 4-butoxyphenyl (35) p-biphenylyl (36) 4-phenylthiophenyl (37) 4-chlorophenyl (38) 4-benzoylphenyl (39) 4-acetoxyphenyl (40) 4-benzoyloxyphenyl ( 41) 4-phenoxycarbonylphenyl (42) 4-methoxyphenyl (43) 4-anilinophenyl (44) 4-isobutyrylaminophenyl (45) 4-phenoxycarbonylaminophenyl (46) 4- (3-ethyl (Ureido) phenyl (47) 4- (3,3-diethylureido) phenyl (48) 4-methylphenyl (49) 4-phenoxyphenyl (50) 4-hydroxyphenyl (51) 3,4-diethoxycarbonylphenyl ( 52) 3,4-dibutoxyphenyl (53) 3 -Diphenylphenyl (54) 3,4-diphenylthiophenyl (55) 3,4-dichlorophenyl (56) 3,4-dibenzoylphenyl (57) 3,4-diacetoxyphenyl (58) 3,4-dibenzoyl Oxyphenyl (59) 3,4-diphenoxycarbonylphenyl (60) 3,4-dimethoxyphenyl (61) 3,4-dianilinophenyl (62) 3,4-dimethylphenyl (63) 3,4-diphenoxy Phenyl (64) 3,4-dihydroxyphenyl (65) 2-naphthyl (66) 3,4,5-triethoxycarbonylphenyl (67) 3,4,5-tributoxyphenyl (68) 3,4,5- Triphenylphenyl (69) 3,4,5-triphenylthiophenyl (70) 3,4,5-trichlorophenyl (71) 3,4,5-tribenzoylphenyl (72) 3,4,5-triacetoxyphenyl (73) 3,4,5-tribenzoyloxyphenyl (74) 3,4,5-triphenoxycarbonylphenyl (75) 3,4,5-trimethoxyphenyl (76) 3,4,5-trianilinophenyl (77) 3,4,5-trimethylphenyl (78) 3,4,5-triphenoxyphenyl (79 ) 3,4,5-trihydroxyphenyl

(80) phenyl (81) 3-ethoxycarbonylphenyl (82) 3-butoxyphenyl (83) m-biphenylyl (84) 3-phenylthiophenyl (85) 3-chlorophenyl (86) 3-benzoylphenyl (87) 3 -Acetoxyphenyl (88) 3-benzoyloxyphenyl (89) 3-phenoxycarbonylphenyl (90) 3-methoxyphenyl (91) 3-anilinophenyl (92) 3-isobutyrylaminophenyl (93) 3-phenoxy Carbonylaminophenyl (94) 3- (3-ethylureido) phenyl (95) 3- (3,3-diethylureido) phenyl (96) 3-methylphenyl (97) 3-phenoxyphenyl (98) 3-hydroxyphenyl (99) 4-Ethoxycarbonylphenyl (100) 4-butoxyphenyl (101) p-biphenylyl (102) 4-phenylthiophenyl (103) 4-chlorophenyl (104) 4-benzoylphenyl (105) 4-acetoxyphenyl (106) 4-benzoyloxyphenyl ( 107) 4-phenoxycarbonylphenyl (108) 4-methoxyphenyl (109) 4-anilinophenyl (110) 4-isobutyrylaminophenyl (111) 4-phenoxycarbonylaminophenyl (112) 4- (3-ethyl (Ureido) phenyl (113) 4- (3,3-diethylureido) phenyl (114) 4-methylphenyl (115) 4-phenoxyphenyl (116) 4-hydroxyphenyl (117) 3,4-diethoxycarbonylphenyl ( 118) 3 , 4-dibutoxyphenyl (119) 3,4-diphenylphenyl (120) 3,4-diphenylthiophenyl (121) 3,4-dichlorophenyl (122) 3,4-dibenzoylphenyl (123) 3,4- Diacetoxyphenyl (124) 3,4-dibenzoyloxyphenyl (125) 3,4-diphenoxycarbonylphenyl (126) 3,4-dimethoxyphenyl (127) 3,4-dianilinophenyl (128) 3,4 -Dimethylphenyl (129) 3,4-diphenoxyphenyl (130) 3,4-dihydroxyphenyl (131) 2-naphthyl (132) 3,4,5-triethoxycarbonylphenyl (133) 3,4,5- Tributoxyphenyl (134) 3,4,5-triphenylphenyl (135) 3 4,5-triphenylthiophenyl (136) 3,4,5-trichlorophenyl (137) 3,4,5-tribenzoylphenyl (138) 3,4,5-triacetoxyphenyl (139) 3,4 5-tribenzoyloxyphenyl (140) 3,4,5-triphenoxycarbonylphenyl (141) 3,4,5-trimethoxyphenyl (142) 3,4,5-trianilinophenyl (143) 3,4 , 5-trimethylphenyl (144) 3,4,5-triphenoxyphenyl (145) 3,4,5-trihydroxyphenyl

(146) phenyl (147) 4-ethoxycarbonylphenyl (148) 4-butoxyphenyl (149) p-biphenylyl (150) 4-phenylthiophenyl (151) 4-chlorophenyl (152) 4-benzoylphenyl (153) 4 -Acetoxyphenyl (154) 4-benzoyloxyphenyl (155) 4-phenoxycarbonylphenyl (156) 4-methoxyphenyl (157) 4-anilinophenyl (158) 4-isobutyrylaminophenyl (159) 4-phenoxy Carbonylaminophenyl (160) 4- (3-ethylureido) phenyl (161) 4- (3,3-diethylureido) phenyl (162) 4-methylphenyl (163) 4-phenoxyphenyl (164) 4-hydroxyphenyl

(165) phenyl (166) 4-ethoxycarbonylphenyl (167) 4-butoxyphenyl (168) p-biphenylyl (169) 4-phenylthiophenyl (170) 4-chlorophenyl (171) 4-benzoylphenyl (172) 4 -Acetoxyphenyl (173) 4-benzoyloxyphenyl (174) 4-phenoxycarbonylphenyl (175) 4-methoxyphenyl (176) 4-anilinophenyl (177) 4-isobutyrylaminophenyl (178) 4-phenoxy Carbonylaminophenyl (179) 4- (3-ethylureido) phenyl (180) 4- (3,3-diethylureido) phenyl (181) 4-methylphenyl (182) 4-phenoxyphenyl (183) 4-hydroxyphenyl

(184) phenyl (185) 4-ethoxycarbonylphenyl (186) 4-butoxyphenyl (187) p-biphenylyl (188) 4-phenylthiophenyl (189) 4-chlorophenyl (190) 4-benzoylphenyl (191) 4 -Acetoxyphenyl (192) 4-benzoyloxyphenyl (193) 4-phenoxycarbonylphenyl (194) 4-methoxyphenyl (195) 4-anilinophenyl (196) 4-isobutyrylaminophenyl (197) 4-phenoxy Carbonylaminophenyl (198) 4- (3-ethylureido) phenyl (199) 4- (3,3-diethylureido) phenyl (200) 4-methylphenyl (201) 4-phenoxyphenyl (202) 4-hydroxyphenyl

(203) phenyl (204) 4-ethoxycarbonylphenyl (205) 4-butoxyphenyl (206) p-biphenylyl (207) 4-phenylthiophenyl (208) 4-chlorophenyl (209) 4-benzoylphenyl (210) 4 -Acetoxyphenyl (211) 4-benzoyloxyphenyl (212) 4-phenoxycarbonylphenyl (213) 4-methoxyphenyl (214) 4-anilinophenyl (215) 4-isobutyrylaminophenyl (216) 4-phenoxy Carbonylaminophenyl (217) 4- (3-ethylureido) phenyl (218) 4- (3,3-diethylureido) phenyl (219) 4-methylphenyl (220) 4-phenoxyphenyl (221) 4-hydroxyphenyl

(222) phenyl (223) 4-butylphenyl (224) 4- (2-methoxy-2-ethoxyethyl) phenyl (225) 4- (5-nonenyl) phenyl (226) p-biphenylyl (227) 4-ethoxy Carbonylphenyl (228) 4-butoxyphenyl (229) 4-methylphenyl (230) 4-chlorophenyl (231) 4-phenylthiophenyl (232) 4-benzoylphenyl (233) 4-acetoxyphenyl (234) 4-benzoyl Oxyphenyl (235) 4-phenoxycarbonylphenyl (236) 4-methoxyphenyl (237) 4-anilinophenyl (238) 4-isobutyrylaminophenyl (239) 4-phenoxycarbonylaminophenyl (240) 4- ( 3-ethylureido Phenyl (241) 4- (3,3-diethylureido) phenyl (242) 4-phenoxyphenyl (243) 4-hydroxyphenyl (244) 3-butylphenyl (245) 3- (2-methoxy-2-ethoxyethyl) ) Phenyl (246) 3- (5-nonenyl) phenyl (247) m-biphenylyl (248) 3-ethoxycarbonylphenyl (249) 3-butoxyphenyl (250) 3-methylphenyl (251) 3-chlorophenyl (252) 3-phenylthiophenyl (253) 3-benzoylphenyl (254) 3-acetoxyphenyl (255) 3-benzoyloxyphenyl (256) 3-phenoxycarbonylphenyl (257) 3-methoxyphenyl (258) 3-anilinophenyl (259) 3-I Butyrylaminophenyl (260) 3-phenoxycarbonylaminophenyl (261) 3- (3-ethylureido) phenyl (262) 3- (3,3-diethylureido) phenyl (263) 3-phenoxyphenyl (264) 3 -Hydroxyphenyl (265) 2-butylphenyl (266) 2- (2-methoxy-2-ethoxyethyl) phenyl (267) 2- (5-nonenyl) phenyl (268) o-biphenylyl (269) 2-ethoxycarbonyl Phenyl (270) 2-Butoxyphenyl (271) 2-Methylphenyl (272) 2-Chlorophenyl (273) 2-Phenylthiophenyl (274) 2-Benzoylphenyl (275) 2-Acetoxyphenyl (276) 2-Benzoyloxy Phenyl (277) 2 Phenoxycarbonylphenyl (278) 2-methoxyphenyl (279) 2-anilinophenyl (280) 2-isobutyrylaminophenyl (281) 2-phenoxycarbonylaminophenyl (282) 2- (3-ethylureido) phenyl ( 283) 2- (3,3-diethylureido) phenyl (284) 2-phenoxyphenyl (285) 2-hydroxyphenyl (286) 3,4-dibutylphenyl (287) 3,4-di (2-methoxy-2) -Ethoxyethyl) phenyl (288) 3,4-diphenylphenyl (289) 3,4-diethoxycarbonylphenyl (290) 3,4-didodecyloxyphenyl (291) 3,4-dimethylphenyl (292) 3, 4-dichlorophenyl (293) 3,4-dibenzoyl Enyl (294) 3,4-diacetoxyphenyl (295) 3,4-dimethoxyphenyl (296) 3,4-di-N-methylaminophenyl (297) 3,4-diisobutyrylaminophenyl (298) 3 , 4-diphenoxyphenyl (299) 3,4-dihydroxyphenyl (300) 3,5-dibutylphenyl (301) 3,5-di (2-methoxy-2-ethoxyethyl) phenyl (302) 3,5- Diphenylphenyl (303) 3,5-diethoxycarbonylphenyl (304) 3,5-didodecyloxyphenyl (305) 3,5-dimethylphenyl (306) 3,5-dichlorophenyl (307) 3,5-dibenzoyl Phenyl (308) 3,5-diacetoxyphenyl (309) 3,5-dimethoxyphenyl (3 0) 3,5-di-N-methylaminophenyl (311) 3,5-diisobutyrylaminophenyl (312) 3,5-diphenoxyphenyl (313) 3,5-dihydroxyphenyl (314) 2,4 -Dibutylphenyl (315) 2,4-di (2-methoxy-2-ethoxyethyl) phenyl (316) 2,4-diphenylphenyl (317) 2,4-diethoxycarbonylphenyl (318) 2,4-di Dodecyloxyphenyl (319) 2,4-dimethylphenyl (320) 2,4-dichlorophenyl (321) 2,4-dibenzoylphenyl (322) 2,4-diacetoxyphenyl (323) 2,4-dimethoxyphenyl ( 324) 2,4-di-N-methylaminophenyl (325) 2,4-diisobutyrylaminopheny (326) 2,4-diphenoxyphenyl (327) 2,4-dihydroxyphenyl (328) 2,3-dibutylphenyl (329) 2,3-di (2-methoxy-2-ethoxyethyl) phenyl (330) 2,3-diphenylphenyl (331) 2,3-diethoxycarbonylphenyl (332) 2,3-didodecyloxyphenyl (333) 2,3-dimethylphenyl (334) 2,3-dichlorophenyl (335) 2, 3-dibenzoylphenyl (336) 2,3-diacetoxyphenyl (337) 2,3-dimethoxyphenyl (338) 2,3-di-N-methylaminophenyl (339) 2,3-diisobutyrylaminophenyl (340) 2,3-diphenoxyphenyl (341) 2,3-dihydroxyphenyl (342 2,6-dibutylphenyl (343) 2,6-di (2-methoxy-2-ethoxyethyl) phenyl (344) 2,6-diphenylphenyl (345) 2,6-diethoxycarbonylphenyl (346) 2, 6-didodecyloxyphenyl (347) 2,6-dimethylphenyl (348) 2,6-dichlorophenyl (349) 2,6-dibenzoylphenyl (350) 2,6-diacetoxyphenyl (351) 2,6- Dimethoxyphenyl (352) 2,6-di-N-methylaminophenyl (353) 2,6-diisobutyrylaminophenyl (354) 2,6-diphenoxyphenyl (355) 2,6-dihydroxyphenyl (356) 3,4,5-tributylphenyl (357) 3,4,5-tri (2-methoxy-2-ethoxy) Til) phenyl (358) 3,4,5-triphenylphenyl (359) 3,4,5-triethoxycarbonylphenyl (360) 3,4,5-tridodecyloxyphenyl (361) 3,4,5- Trimethylphenyl (362) 3,4,5-trichlorophenyl (363) 3,4,5-tribenzoylphenyl (364) 3,4,5-triacetoxyphenyl (365) 3,4,5-trimethoxyphenyl ( 366) 3,4,5-tri-N-methylaminophenyl (367) 3,4,5-triisobutyrylaminophenyl (368) 3,4,5-triphenoxyphenyl (369) 3,4,5 -Trihydroxyphenyl (370) 2,4,6-tributylphenyl (371) 2,4,6-tri (2-methoxy-2-ethoxyethyl) ) Phenyl (372) 2,4,6-triphenylphenyl (373) 2,4,6-triethoxycarbonylphenyl (374) 2,4,6-tridodecyloxyphenyl (375) 2,4,6-trimethyl Phenyl (376) 2,4,6-trichlorophenyl (377) 2,4,6-tribenzoylphenyl (378) 2,4,6-triacetoxyphenyl (379) 2,4,6-trimethoxyphenyl (380 ) 2,4,6-tri-N-methylaminophenyl (381) 2,4,6-triisobutyrylaminophenyl (382) 2,4,6-triphenoxyphenyl (383) 2,4,6- Trihydroxyphenyl (384) Pentafluorophenyl (385) Pentachlorophenyl (386) Pentamethoxyphenyl (38 ) 6-N-methylsulfamoyl-8-methoxy-2-naphthyl (388) 5-N-methylsulfamoyl-2-naphthyl (389) 6-N-phenylsulfamoyl-2-naphthyl (390) 5-Ethoxy-7-N-methylsulfamoyl-2-naphthyl (391) 3-methoxy-2-naphthyl (392) 1-ethoxy-2-naphthyl (393) 6-N-phenylsulfamoyl-8- Methoxy-2-naphthyl (394) 5-methoxy-7-N-phenylsulfamoyl-2-naphthyl (395) 1- (4-methylphenyl) -2-naphthyl (396) 6,8-di-N- Methylsulfamoyl-2-naphthyl (397) 6-N-2-acetoxyethylsulfamoyl-8-methoxy-2-naphthyl (398) 5-acetoxy-7- N-phenylsulfamoyl-2-naphthyl (399) 3-benzoyloxy-2-naphthyl (400) 5-acetylamino-1-naphthyl (401) 2-methoxy-1-naphthyl (402) 4-phenoxy-1 -Naphtyl (403) 5-N-methylsulfamoyl-1-naphthyl (404) 3-N-methylcarbamoyl-4-hydroxy-1-naphthyl (405) 5-methoxy-6-N-ethylsulfamoyl- 1-naphthyl (406) 7-tetradecyloxy-1-naphthyl (407) 4- (4-methylphenoxy) -1-naphthyl (408) 6-N-methylsulfamoyl-1-naphthyl (409) 3- N, N-dimethylcarbamoyl-4-methoxy-1-naphthyl (410) 5-methoxy-6-N-benzylsulfamoyl 1-naphthyl (411) 3,6-di-N-phenylsulfamoyl-1-naphthyl (412) methyl (413) ethyl (414) butyl (415) octyl (416) dodecyl (417) 2-butoxy-2 -Ethoxyethyl (418) benzyl (419) 4-methoxybenzyl

(424) Methyl (425) Phenyl (426) Butyl

(430) methyl (431) ethyl (432) butyl (433) octyl (434) dodecyl (435) 2-butoxy-2-ethoxyethyl (436) benzyl (437) 4-methoxybenzyl

  In the present invention, a melamine polymer may be used as the compound having a 1,3,5-triazine ring. The melamine polymer can be synthesized by a polymerization reaction of a melamine compound and a carbonyl compound represented by the following general formula (5).

In the above synthetic reaction scheme, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group.

  The alkyl group, alkenyl group, aryl group, heterocyclic group and substituents thereof have the same meanings as the groups and substituents described in the general formula (4).

  The polymerization reaction between the melamine compound and the carbonyl compound is the same as the method for synthesizing a normal melamine resin (for example, melamine formaldehyde resin). Moreover, you may use a commercially available melamine polymer (melamine resin). The molecular weight of the melamine polymer is preferably 2,000 to 400,000.

  Moreover, you may use together the compound which has a 2 or more types of 1,3,5- triazine ring. Two or more kinds of discotic compounds (for example, a compound having a 1,3,5-triazine ring and a compound having a porphyrin skeleton) may be used in combination.

  These retardation increasing agents are preferably contained in an amount of 0.01 to 20% by mass, particularly preferably 1 to 10% by mass, based on the cellulose ester.

<Crosslinking agent>
A crosslinking agent is used for the cellulose ester film of the present invention.

  The crosslinking agent in the present invention reacts with the hydroxyl group of cellulose ester to form a crosslinked structure between cellulose esters.

  The crosslinking agent used in the present invention is a compound having in the molecule two or more groups capable of reacting with free hydroxyl groups in the cellulose ester, and examples of the groups capable of reacting include isocyanate groups and acid halide groups. , Epoxy groups, silyl chloride groups, and the like.

  The crosslinking agent preferably used in the present invention is an isocyanate-based crosslinking agent having two or more isocyanate groups in the molecule. Preferred isocyanate crosslinking agents include, for example, isocyanates having aromatic rings such as 2,4-tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, n-butyl diisocyanate, hexamethylene diisocyanate. Examples include aliphatic isocyanates such as hydrogenated isocyanates such as hydrogenated TDI and hydrogenated MDI.

  Moreover, you may use the polyisocyanate which reacted these isocyanate compounds and the active hydrogen group containing compound.

  These isocyanate compounds can also be purchased as commercial products. For example, the Coronate series manufactured by Nippon Polyurethane Co., Ltd. or the Sumijoule series manufactured by Sumitomo Bayer Urethane Co., Ltd.

  By adding these cross-linking agents into the dope and cross-linking the cellulose ester, the humidity dependence of the cellulose ester film can be improved, and the durability can be improved by preventing bleeding out of plasticizers and the like. I was able to.

  In addition, the addition method of a crosslinking agent may be added batchwise to the dope solution in which the cellulose ester is dissolved, or a crosslinking agent solution may be separately prepared and added in-line. In order to suppress the reaction between the crosslinking agent and the cellulose ester in the dope solution, a method of adding a crosslinking agent solution in-line is preferable.

  In the case where the cross-linking agent solution is added in-line, it is preferable to dissolve a small amount of the polymer resin in order to improve the mixing property with the dope. Examples of the preferred polymer resin are not particularly limited as long as the compatibility with the cellulose ester is good. Examples thereof include the cellulose ester, polymethyl methacrylate, and the melamine resin. The amount of the polymer resin is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In the present invention, for example, a static mixer (manufactured by Toray Engineering Co., Ltd.), SWJ (Toray static type in-tube mixer) is used for in-line addition and mixing of a dope solution obtained by dissolving a cellulose ester in a solvent and a crosslinking agent solution. An in-line mixer such as Hi-Mixer) is preferably used.

<Plasticizer>
In the production of the cellulose ester film of the present invention, it is preferable to use a plasticizer. Although it does not specifically limit as a plasticizer which can be used, For example, a polyhydric alcohol ester plasticizer, a glycolate plasticizer, a phosphate ester plasticizer, a phthalate ester plasticizer etc. can be used. Particularly preferred are polyhydric alcohol plasticizers and ester plasticizers. Moreover, it is preferable that the addition amount of a phosphate ester plasticizer shall be 6 mass% or less.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used for the polyhydric alcohol ester is represented by the following general formula (1).

Formula (1) R _1- (OH) _n
In the formula, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic or phenolic hydroxyl group.

  Examples of preferable polyhydric alcohols include the following. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as 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, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. Aromatic monocarboxylic acids possessed by them, or derivatives thereof. In particular, benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester. The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are. The specific compound of a polyhydric alcohol ester is shown below.

  The ester plasticizer is not particularly limited, and an ester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a preferable ester plasticizer, For example, it represents with the following general formula (I).

Formula (I) B- (GA) _n -GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 0 or more.)
In the general formula (I), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the ester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the ester plasticizer of the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 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 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol, -Methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. These glycols are used as one kind or a mixture of two or more kinds .

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester of the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester of the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are each used as one or a mixture of two or more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, 1,5 naphthalene dicarboxylic acid, 1,4 naphthalene dicarboxylic acid, and the like.

  The ester plasticizer used in the present invention has a number average molecular weight of preferably 250 to 2000, more preferably 300 to 1500. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and the like can be used.

  These plasticizers can be used alone or in admixture of two or more. 4-20 mass% is preferable with respect to a cellulose ester, and, as for the usage-amount of a plasticizer, 6-16 mass% is still more preferable, Most preferably, it is 7-11 mass%. If the amount of the plasticizer added is too large, the film becomes too soft and the rate of decrease in elastic modulus due to heat increases. If the amount added is too small, the moisture permeability of the film decreases.

<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose-ester film of this invention is demonstrated.

  Cellulose ester, retardation increasing agent, crosslinking agent, other additives are dissolved in a solvent to form a dope solution, a dope solution is cast on a support, and a cast dope solution is dried. Done.

  The concentration of the cellulose ester in the dope is preferably higher because the drying load after casting on the support can be reduced. However, if the concentration of the cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-50 mass% is preferable, More preferably, it is 15-35 mass%.

  The solvent used in the dope solution may be used alone or in combination, but it is preferable from the viewpoint of production efficiency to use a good solvent and a poor solvent of cellulose ester, and the more soluble solvent is, the more soluble the cellulose ester is. Is preferable. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 30 to 2% by mass for the poor solvent.

  With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the average degree of acetylation of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as a solvent, cellulose acetate (bound acetic acid amount 55%), cellulose acetate propionate is a good solvent. Thus, cellulose acetate (bound acetic acid amount 60%) becomes a poor solvent.

  The good solvent is not particularly limited. For example, in the case of cellulose triacetate, organic halogen compounds such as methylene chloride and dioxolanes, and in the case of cellulose acetate propionate, methylene chloride, acetone, methyl acetate and the like can be mentioned.

  Moreover, although a poor solvent is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, acetone, cyclohexanone etc. are used preferably.

  A general method can be used as a method for dissolving the cellulose ester when preparing the dope solution described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the formation of massive undissolved material called gel or mamako. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

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

  The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. The range of preferable heating temperature is 45-120 degreeC, 60-110 degreeC is more preferable, and the range of 70 degreeC-105 degreeC is still more preferable. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters. However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium in the range of 0.001 to 0.008 mm is more preferable, and a filter medium in the range of 0.003 to 0.006 mm is still more preferable.

  The material of the filter medium is not particularly limited, and a normal filter medium can be used. However, a plastic filter medium such as polypropylene and Teflon (registered trademark) and a metal filter medium such as stainless steel are preferable because there is no loss of fibers. .

  The dope solution can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is different between before and after the filter medium. The increase in pressure (hereinafter sometimes referred to as filtration pressure) is small and preferable. A preferred temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C. A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  As the support in the casting process, a stainless endless belt or drum having a mirror-finished surface is preferably used. The temperature of the support in the casting process is preferably 0 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the drying rate can be increased. However, if the temperature is too high, foaming or flatness may be deteriorated. . The support temperature is preferably 0 to 40 ° C, and more preferably cast on a support at 5 to 30 ° C. The method for controlling the temperature of the support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of bringing a hot water bat into contact with the support. It is preferable to use a hot water bat because heat is efficiently transmitted, so that the time until the temperature of the support becomes constant is short. When warm air is used, it may be necessary to use wind at a temperature higher than the target temperature.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling from the support is preferably 10 to 120%, more preferably 20 to 40% or 60 to 120%, particularly preferably. Is 20-30% or 70-115%. The amount of residual solvent is defined by the following formula.

Residual solvent amount = ((mass before heat treatment−mass after heat treatment) / (mass after heat treatment)) × 100 (%)
Note that the heat treatment when measuring the residual solvent amount means that the film is heat treated at 115 ° C. for 1 hour.

  Moreover, in the drying process of the cellulose ester film, the film peeled off from the support is further dried, and the residual solvent amount is preferably 3% or less, more preferably 0.5% or less. In the film drying process, generally, a roll suspension system or a tenter system is used for drying while transporting the film.

  Where the amount of residual solvent immediately after peeling from the support is large, the Re retardation value is in the range of 20 to 70 nm and the Rth retardation value is 70 to 400 nm by carrying out width holding and stretching by a tenter method. Adjust to be within range. A preferable draw ratio is 0 to 15%, and more preferably 1 to 12%. The stretching ratio of 0% means width retention, and the same effect as stretching can be obtained at a place where the amount of residual solvent is large.

  The means for drying the film is not particularly limited, and can be generally performed with hot air, infrared rays, heating rolls, microwaves, etc., but it is preferably performed with hot air in terms of simplicity.

  The drying temperature is preferably increased stepwise in the range of 40 to 150 ° C, and more preferably in the range of 50 to 140 ° C in order to improve the reactivity with the crosslinking agent. Moreover, it is preferable at the point which accelerates | stimulates a crosslinking reaction to dry for 10 to 40 minutes in the softening point +/- 20 degreeC of a film. The retardation in the casting direction can be controlled by controlling the conveyance tension during drying of the film at the softening point of ± 20 ° C. The range of preferable conveyance tension is 150 to 350 N / m, and 200 to 300 N / m is more preferable.

  Although the thickness of a film is not specifically limited, For example, the film of arbitrary thickness, such as a thing of about 10 micrometers-1 mm, can be produced. Preferably, the film thickness after drying, stretching and the like is preferably 10 to 500 μm, particularly preferably 30 to 120 μm.

  The cellulose ester film of the present invention preferably has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.4 to 2 m. If it exceeds 4 m, conveyance becomes difficult.

  You may add additives, such as a ultraviolet absorber, dye, and a mat agent, to the cellulose-ester film of this invention as needed. From the viewpoint of preventing deterioration of the liquid crystal, an ultraviolet absorbent having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less and less visible light absorption having a wavelength of 400 nm or more is preferably used from the viewpoint of good liquid crystal display properties. In the present invention, the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less, and further preferably 2% or less.

(Optical compensation film)
The cellulose ester film of the present invention can be used as a protective film for a polarizing plate such as a liquid crystal display and at the same time as an optical compensation film for compensating for the retardation of the liquid crystal.

  The polarizing plate can be produced by a general method. One side of the cellulose ester film of the present invention is subjected to alkali saponification treatment, and a completely saponified polyvinyl alcohol aqueous solution is used on at least one side of a polarizing film prepared by immersing and stretching the treated film in an iodine solution. It is preferable to bond them together. The film may be used on the other surface, or another polarizing plate protective film may be used. A polarizing plate protective film in which an optical compensation film having an optical anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal, a rod-like liquid crystal, or a cholesteric liquid crystal on the cellulose ester film of the present invention may be used. I can do it.

  As a polarizing plate protective film used on the back side, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3 (manufactured by Konica Minolta Opto Co., Ltd.) and the like are also preferably used as commercially available cellulose ester films.

  The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. On the surface of the polarizing film, one side of the optical film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  Since the cellulose ester film according to the present invention is cross-linked, it is excellent in dimensional stability, and thus is suitably used as such a polarizing plate protective film.

  The embodiments of the present invention will be specifically described below using examples, but the present invention is not limited to these.

Example 1
<Preparation of Sample 101>
(Preparation of dope solution)
Cellulose triacetate (Linter, 60.3% acetylation) 100kg
Triphenyl phosphate (TPP) 10kg
Ethyl phthalyl ethyl glycolate (EPEG) 2kg
Retardation increasing agent: discotic compound (420 ') 3 kg
Cross-linking agent: Sumidur N3300 (manufactured by Sumika Bayer Urethane Co., Ltd.) 6kg
590 kg of methylene chloride
Ethanol 50kg
The above was put into a closed container and dissolved with stirring to prepare a dope solution.

(Casting, drying)
Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 25 ° C. On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film was 75% by mass, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

  The peeled cellulose triacetate film was stretched 30% in the width direction using a tenter while applying heat at 140 ° C. The residual solvent at the start of stretching was 30% by mass.

  Subsequently, it was dried at 140 ° C. for 20 minutes while being conveyed by a number of rolls in a drying zone. The conveyance tension was 150 N / m. The solvent residual amount of the obtained cellulose ester film was 0.1% by mass.

  As described above, a sample 101 of a cellulose triacetate film having a dry film thickness of 80 μm was obtained.

<Preparation of Samples 102 to 121>
Samples 102 to 121 were prepared in the same manner as described above except that the crosslinking agent of sample 101: Sumidur N3300 and retardation increasing agent were changed in type and amount as shown in Table 1.

<Evaluation>
About each obtained sample, Re retardation value, Rth retardation value, and bleed out were measured in the following ways. Table 1 shows the contents and results of the samples.

<Bleed out>
The sample was cut to a size of 10 (cm) × 10 (cm) and subjected to a constant temperature and humidity treatment under conditions of 80 ° C. and 90% RH for 120 hours. The surface state of the sample after the constant temperature and humidity treatment was visually observed to check for bleeding out. Preferably there is no bleed out.

<Re, Rth, Rth changes>
Re and Rth of the sample were measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments). Re and Rth were measured under the conditions of 23 ° C., 20% RH, 23 ° C., 55% RH, and 23 ° C., 80% RH, respectively. The Re retardation value and Rth retardation value in the present invention are Re and Rth, respectively, measured at 23 ° C. and 55% RH.

  The difference between Rth at 23 ° C. and 20% RH and Rth at 23 ° C. and 80% RH was taken as the Rth change.

Rth change = (Rth of 23 ° C. and 20% RH) − (Rth of 23 ° C. and 80% RH)
The smaller the change in Rth, the better. However, there is no practical problem if it is 10 nm or less.

<Preparation of polarizing plate>
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and each sample 101 to 114 subjected to saponification treatment was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. A commercially available cellulose acetate film (Konica Minoltac KC8UX) was saponified and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. At this time, the transmission axis of the polarizing film and the slow axis of the sample were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose acetate film were arranged so as to be orthogonal. In this way, polarizing plates 101 to 114 were prepared for each sample.

  A pair of polarizing plates and a retardation plate provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using a vertical alignment type liquid crystal cell are peeled off, and instead, sample films of polarizing plates 101 to 114 are liquid crystals. It stuck through the adhesive so that it might become a cell side. The crossed nicols were arranged so that the transmission axis direction of the polarizing plate on the observer side was up and down and the transmission axis of the polarizing plate on the backlight side was in the left and right direction.

<Frame unevenness>
Under an environment of 23 ° C. and 55% RH, the backlight was continuously turned on for 5 hours, and the entire black display state was visually observed in a dark room to observe frame unevenness (light leakage). The results are shown in Table 1.

Coronate HX, Coronate L: manufactured by Nippon Polyurethane Co., Ltd. By adopting the configuration of the present invention, a high retardation value can be obtained, fluctuation due to humidity is small, bleed out can be reduced, and a polarizing plate with little frame unevenness is obtained I was able to.

Claims (6)

A coating solution containing 0.01 to 20 parts by mass of a retardation increasing agent with respect to 100 parts by mass of the cellulose ester and 4 to 30 parts by mass of a crosslinking agent and a solvent with respect to 100 parts by mass of the cellulose ester. A cellulose ester film formed by casting and drying, wherein the Re retardation value defined by the following formula (I) is in the range of 20 to 70 nm, and the Rth retardation defined by the following formula (II): A cellulose ester film having a value in the range of 70 to 400 nm.
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
(Where 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 It is the thickness of the film.) The cellulose ester film according to claim 1, which is a cellulose ester that simultaneously satisfies the following formulas (III), (IV), and (V).
(III) 2.0 <X + Y <3.0
(IV) 1.4 ≦ X <3.0
(V) 0 ≦ Y ≦ 1.2
(In the formula, X is the degree of substitution with an acetyl group, and Y is the degree of substitution with an acyl group having 3 to 22 carbon atoms.) The cellulose ester film according to claim 1 or 2, wherein the crosslinking agent is an isocyanate-based crosslinking agent. An optical compensation film using the cellulose ester film according to claim 1. A polarizing plate comprising the optical compensation film according to claim 4 as a polarizing plate protective film on at least one surface. A liquid crystal display device comprising the polarizing plate according to claim 5.