JP2001253971A - Cellulose acetate film, phase-difference plate, and circularly polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polymer film easy to regulate the wavelength dispersion characteristics of retardation. SOLUTION: This cellulose acetate film is obtained from a mixture of at least two kinds of cellulose acetate differing in acetylation degree from each other; wherein the acetylation degree difference between the cellulose acetate with a maximum acetylation degree and that with a minimum acetylation degree is adjusted to 2.0-6.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose acetate film, and a retardation plate and a circularly polarizing plate using the same. In particular, the present invention relates to a λ / 4 plate or a λ / 2 plate used in a liquid crystal display device, a λ / 4 plate used for a pickup for writing on an optical disk, or a λ / 4 plate used as an antireflection film. It relates to an effective cellulose acetate film.

[0002]

2. Description of the Related Art A λ / 4 plate and a λ / 2 plate have many uses related to an antireflection film and a liquid crystal display device, and have already been actually used. However, λ / 4 plate or λ
Λ / 4 or λ / 2 at a specific wavelength
Most of those who achieved were. JP-A-5-27
Nos. 118 and 5-27119 disclose a retardation plate in which a birefringent film having a large retardation and a birefringent film having a small retardation are laminated so that their optical axes are orthogonal to each other. Is disclosed.
If the difference in retardation between the two films is λ / 4 or λ / 2 over the entire visible light range, the retardation plate theoretically has a λ / 4 plate or λ /
Functions as two plates.

Japanese Patent Laid-Open Publication No. Hei 10-68816 discloses that a polymer film having a wavelength of λ / 4 at a specific wavelength and a polymer film of the same material and having a wavelength of λ / 2 at the same wavelength are laminated. A retardation plate that can obtain λ / 4 in the wavelength region is disclosed. JP 1
Japanese Patent Application Publication No. 0-90521 also discloses a retardation plate capable of achieving λ / 4 in a wide wavelength region by laminating two polymer films. As the above polymer film, a stretched film of a synthetic polymer such as polycarbonate has been used.

[0004]

By laminating two polymer films, λ / 4 or λ / 2 can be achieved in a wide wavelength range. However, for this purpose, it is necessary to laminate two polymer films while strictly adjusting the angle. A λ / 4 plate or λ / 2 plate made of one polymer film has also been proposed. But,
There is almost no single film in which λ / 4 or λ / 2 is achieved in a wide wavelength region. An object of the present invention is to provide a polymer film in which the wavelength dispersion characteristics of retardation can be easily adjusted. It is an object of the present invention to use a single polymer film for a wide wavelength range of λ.
/ 4 or λ / 2.

[0005]

The object of the present invention is to provide a cellulose acetate film of the following (1) and (2), a retardation plate (λ / 4 plate) of the following (3) to (7), and a following (8) ) And the following retardation plates (9) to (13) (λ /
2 plates). (1) A mixture of two or more cellulose acetates having different degrees of acetylation, wherein the difference between the degree of acetylation between the cellulose acetate having the highest degree of acetylation and the cellulose acetate having the lowest degree of acetylation is 2.0. Cellulose acetate film, characterized in that the content is from 0.1 to 6.0%. (2) The cellulose acetate film according to (1), wherein the average degree of acetylation of the entire mixture of cellulose acetate is 55.0 to 61.5%.

(3) One cellulose acetate film, wherein the cellulose acetate film is a mixture of two or more cellulose acetates having different degrees of acetylation, wherein the cellulose acetate having the highest degree of acetylation and the minimum acetylation are used. Difference between cellulose acetate having a degree of acetylation of 2.0 to 6.0%, a retardation measured at a wavelength of 450 nm (Re450) of 100 to 125 nm, and a retardation measured at a wavelength of 590 nm A retardation plate having a value (Re590) of 120 to 160 nm and satisfying a relationship of Re590-Re450 ≧ 2 nm. (4) a retardation value (Re450) measured at a wavelength of 450 nm is from 108 to 120 nm,
Retardation value measured at 50 nm (Re550)
Is 125 to 142 nm, and the retardation value (Re590) measured at a wavelength of 590 nm is 130 to 1
52 nm, and Re590-Re550 ≧ 2
The retardation plate according to (3), which satisfies the relationship of nm. (5) The retardation plate according to (3), wherein the cellulose acetate film is a stretched film. (6) The retardation plate according to (3), wherein the cellulose acetate film contains a compound having at least two aromatic rings as a retardation increasing agent. (7) Refractive index nx in the in-plane slow axis direction of the cellulose acetate film, and n in the direction perpendicular to the in-plane slow axis.
y and the refractive index nz in the thickness direction are 1 ≦ (nx−nz)
The retardation plate according to (3), which satisfies the relationship of / (nx−ny) ≦ 2.

(8) The phase difference plate and the linear polarizing film are laminated so that the angle between the slow axis in the plane of the phase difference plate and the polarization axis of the linear polarizing film is substantially 45 °. A circularly polarizing plate, wherein the retardation plate is composed of one piece of cellulose acetate film, and the cellulose acetate film is composed of a mixture of two or more types of cellulose acetate having different degrees of acetylation, and has a maximum degree of acetylation. And the cellulose acetate having the minimum acetylation degree is 2.0 to 6.0%, and the retardation value (Re450) measured at a wavelength of 450 nm is 100 to 1
A circularly polarizing plate, which has a retardation value (Re590) of 120 to 160 nm measured at a wavelength of 590 nm and a wavelength of 590 nm, and satisfies the relationship of Re590-Re450 ≧ 2 nm.

(9) One cellulose acetate film, wherein the cellulose acetate film is a mixture of two or more cellulose acetates having different degrees of acetylation, wherein the cellulose acetate having the highest degree of acetylation and the minimum acetylation are used. Difference between cellulose acetate having a degree of acetylation of 2.0 to 6.0%, a retardation value (Re450) measured at a wavelength of 450 nm of 200 to 250 nm, and a retardation measured at a wavelength of 590 nm. A retardation plate having a value (Re590) of 240 to 320 nm and satisfying a relationship of Re590-Re450 ≧ 4 nm. (10) The retardation value (Re450) measured at a wavelength of 450 nm is 216 to 240 nm, and the
Retardation value measured at 50 nm (Re550)
Is 250 to 284 nm, and the retardation value (Re590) measured at a wavelength of 590 nm is 260 to 3
04 nm, and Re590-Re550 ≧ 4
The retardation plate according to (9), which satisfies the relationship of nm. (11) The retardation plate according to (9), wherein the cellulose acetate film is a stretched film. (12) The retardation plate according to (9), wherein the cellulose acetate film contains a compound having at least two aromatic rings as a retardation increasing agent. (13) The refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the slow axis in the plane, and the refractive index nz in the thickness direction of the cellulose acetate film are 1 ≦ (nx−n).
(9) The retardation plate according to (9), which satisfies a relationship of (x) / (nx-ny) ≦ 2.

[0009]

As a result of research, the present inventor has succeeded in obtaining a polymer film in which the wavelength dispersion characteristic of retardation can be easily adjusted by adjusting the material of the polymer film. Specifically, when two types of cellulose acetates having different degrees of acetylation within a certain range are mixed, a polymer film (cellulose acetate film) in which the wavelength dispersion characteristic of retardation can be easily adjusted can be produced. Then, by adjusting the wavelength dispersion characteristic of the retardation, λ / 4 or λ / 2 can be achieved in a wide wavelength region. By obtaining a retardation plate that achieves λ / 4 or λ / 2 in a wide wavelength range, the step of laminating two polymer films while strictly adjusting the angle of the conventional polymer film becomes unnecessary. There are many documents suggesting the use of two or more types of cellulose acetate in the production of cellulose acetate films, but there are few examples of actually producing cellulose acetate films in combination. When two or more cellulose acetates are used in combination, there is a problem that the transparency of the film tends to decrease (haze tends to increase). As a result of the study of the present inventors, it has been found that this problem can be solved by adjusting the degree of acetylation and the degree of polymerization of two or more kinds of cellulose acetate (details will be described later).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Retardation plate] When a retardation plate (cellulose acetate film) is used as a λ / 4 plate, a retardation value (R) measured at a wavelength of 450 nm is used.
e450) is 100 to 125 nm, and the wavelength 5
Retardation value measured at 90 nm (Re590)
Is from 120 to 160 nm, and Re590-
The relationship of Re450 ≧ 2 nm is satisfied. Re590-R
e450 ≧ 5 nm is more preferable, and Re5
Most preferably, 90-Re450 ≧ 10 nm. The retardation value (R) measured at a wavelength of 450 nm
e450) is 108 to 120 nm and the wavelength is 550.
The retardation value (Re550) measured in nm is 1
25 to 142 nm, and the retardation value (Re590) measured at a wavelength of 590 nm is 130 to 152.
nm and Re590-Re550 ≧ 2 nm
Is preferably satisfied. Re590-Re5
More preferably, 50 ≧ 5 nm.
Most preferably, -Re550 ≧ 10 nm. Further, it is also preferable that Re550−Re450 ≧ 10 nm.

When a retardation plate (cellulose acetate film) is used as a λ / 2 plate, the wavelength is 450 nm.
Retardation value (Re450) measured at 200
And the retardation value (Re590) measured at a wavelength of 590 nm is 240 to 320.
nm and Re590-Re450 ≧ 4 nm
Satisfy the relationship. Re590-Re450 ≧ 10 nm
And more preferably Re590-Re450.
The retardation value (Re450) measured at a wavelength of 450 nm, most preferably ≧ 20 nm, is 216 to 240 nm, the retardation value (Re550) measured at a wavelength of 550 nm is 250 to 284 nm, and a letter measured at a wavelength of 590 nm. It is preferable that the retardation value (Re590) is 260 to 304 nm and that the relationship of Re590−Re550 ≧ 4 nm is satisfied. Also, Re590−Re550 ≧ 10n
m, more preferably, Re590-Re55.
Most preferably, 0 ≧ 20 nm. Also, Re5
It is also preferable that 50-Re450 ≧ 20 nm. The retardation value (Re) is calculated according to the following equation. Retardation value (Re) = (nx−ny) × d where nx is the in-plane refractive index in the plane of the retardation plate (maximum in-plane refractive index); ny is the retardation The index of refraction in the direction perpendicular to the slow axis in the plane of the plate; and d is
This is the thickness (nm) of the phase difference plate.

It is preferable that the retardation film (cellulose acetate film) further has optical properties satisfying the following formula. 1 ≦ (nx−nz) / (nx−ny) ≦ 2, where nx is the in-plane refractive index in the plane of the retardation plate; ny is the in-plane retardation of the retardation plate Is the refractive index in the direction perpendicular to the axis; and nz is the refractive index in the thickness direction. The thickness of the cellulose acetate film is 5 to 1
000 μm, preferably 10 to 500 μm
Is more preferably 40 to 200 μm, and most preferably 70 to 120 μm. The haze of the cellulose acetate film is preferably 2.0% or less. The cellulose acetate film having the above optical properties can be manufactured by the following materials and methods.

[Cellulose Acetate] In the present invention, two or more kinds of cellulose acetates having different degrees of acetylation are used. The difference (Ac1-Ac2) in the acetylation degree between the cellulose acetate having the maximum acetylation degree (Ac1) and the cellulose acetate having the minimum acetylation degree (Ac2) is 2.0.
To 6.0% (2.0% ≦ Ac1-Ac2 ≦ 6.0%)
It is. The average acetylation degree of the entire mixture of cellulose acetate is preferably 55.0 to 61.5%.
Further, the non- (P1 / 1) of the viscosity average polymerization degree of the cellulose acetate having the maximum viscosity average polymerization degree (P1) and the cellulose acetate having the minimum viscosity average polymerization degree (P2) is different.
P2) is preferably 1 or more and less than 2 (1 ≦ P1 / P2 <2). The viscosity average degree of polymerization of the entire mixture of cellulose acetate is preferably from 250 to 500, and more preferably from 250 to 400.
As described above, when the degree of acetylation and the degree of polymerization of two or more types of cellulose acetate are adjusted, the haze is low (2.0% or less) even though two or more types of cellulose acetate are used in combination. ) Cellulose acetate film can be obtained.

[Retardation Raising Agent] In order to adjust the retardation value at each wavelength, a retardation raising agent can be added to the cellulose acetate film. The retardation increasing agent is preferably used in an amount of 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of cellulose acetate. More preferably, it is used in the range of 2 to 5 parts by weight.
Most preferably, it is used in the range of 5 to 2 parts by weight.
Two or more retardation increasing agents may be used in combination. The retardation increasing agent is 250 to 400 nm
Has a maximum absorption in the wavelength region of It is preferable that the retardation increasing agent has substantially no absorption in the visible region.

As the retardation increasing agent, it is preferable to use a compound having at least two aromatic rings. In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). Aromatic heterocycles are generally unsaturated heterocycles. The aromatic hetero ring is preferably a 5-, 6-, or 7-membered ring, more preferably a 5- or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of the aromatic hetero ring include a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, a pyrazole ring, a furazane ring, a triazole ring, a pyran ring, and a pyridine ring. , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, 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, a pyrazine ring and a 1,3,5-triazine ring are preferable.

The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, and preferably 2 to 12
Is more preferably, 2 to 8 is more preferable, and 2 to 6 is most preferable. The bonding relationship between two aromatic rings can be classified into (a) a case where a condensed ring is formed, (b) a case where they are directly connected by a single bond, and (c) a case where they are bonded via a linking group. , A spiro bond cannot be formed). The connection relationship is (a)-
Any of (c) may be used.

Examples of the condensed ring of (a) (condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, Naphthacene ring, pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline Ring, isoquinoline ring,
A quinolidine ring, a quinazoline ring, a cinnoline ring, a quinoxaline ring, a phthalazine ring, a pteridine ring, a carbazole ring, an acridine ring, a phenanthridine ring, a xanthene ring, a phenazine ring, a phenothiazine ring, a phenoxatiin ring, a phenoxazine ring and a thianthrene ring; included. Preferred are a naphthalene ring, an azulene ring, an indole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a benzotriazole ring and a quinoline ring. The single bond in (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be linked by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The connecting group (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is an alkylene group, alkenylene group, alkynylene group, -CO-, -O
-, -NH-, -S- or a combination thereof is preferred. Examples of the linking group consisting of a combination are shown below. Note that the left and right relationships in the following examples of the linking group may be reversed. c1: -CO-O-c2: -CO-NH-c3: -alkylene-O-c4: -NH-CO-NH-c5: -NH-CO-O-c6: -O-CO-O-c7: -O-alkylene-O-c8: -CO-alkenylene-c9: -CO-alkenylene-NH-c10: -CO-alkenylene-O-c11: -alkylene-CO-O-alkylene-O-CO
-Alkylene-c12: -O-alkylene-CO-O-alkylene-O-
CO-alkylene-O-c13: -O-CO-alkylene-CO-O-c14: -NH-CO-alkenylene- c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent. Examples of the substituent include a halogen atom (F, C
l, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl, alkenyl, alkynyl, aliphatic acyl, aliphatic acyloxy, alkoxy, alkoxycarbonyl , Alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamide group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic substituted sulfamoyl group, aliphatic substituted ureido group and non-aromatic Group heterocyclic groups.

The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable.
The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl,
-Hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable.
The alkenyl group may further have a substituent. Examples of the alkenyl group include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl, 1-butynyl and 1-hexynyl.

The number of carbon atoms of the aliphatic acyl group is 1 to 1
It is preferably 0. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl. The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy. The alkoxy group preferably has 1 to 8 carbon atoms. The alkoxy group may further have a substituent (eg, an alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The alkoxycarbonylamino group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The number of carbon atoms of the alkylthio group is 1 to 1
It is preferably 2. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl. The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide. The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamide group include methanesulfonamide, butanesulfonamide and n-octanesulfonamide. The aliphatic substituted amino group preferably has 1 to 10 carbon atoms. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino. The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include methyl ureide. Examples of the non-aromatic heterocyclic group include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably from 300 to 800.

[Infrared absorber] An infrared absorber can be added to the cellulose acetate film in order to adjust the retardation value at each wavelength. The infrared absorber is based on 100 parts by weight of cellulose acetate.
Preferably used in the range of 0.01 to 5 parts by weight, more preferably used in the range of 0.02 to 2 parts by weight, further preferably used in the range of 0.05 to 1 part by weight, Most preferably, it is used in the range of 0.1 to 0.5 parts by weight. Two or more infrared absorbers may be used in combination. The infrared absorber is 750 to 110
It preferably has a maximum absorption in a wavelength region of 0 nm,
More preferably, it has a maximum absorption in the wavelength region of 800 to 1000 nm. It is preferred that the infrared absorber has substantially no absorption in the visible region.

As the infrared absorbing agent, it is preferable to use an infrared absorbing dye or an infrared absorbing pigment, and it is particularly preferable to use an infrared absorbing dye. The infrared absorbing dye includes an organic compound and an inorganic compound. It is preferable to use an infrared absorbing dye which is an organic compound. Organic infrared absorbing dyes include cyanine compounds, metal chelate compounds, aminium compounds, diimonium compounds, quinone compounds, squarylium compounds and methine compounds. For the infrared absorbing dye, coloring material, 61 [4] 2
15-226 (1988), and Chemical Industry, 43-5.
3 (1986, May).

When examining the types of dyes from the viewpoint of the infrared absorption function or absorption spectrum, the infrared absorption dyes developed in the technical field of silver halide photographic materials are excellent. Infrared absorbing dyes developed in the technical field of silver halide photographic light-sensitive materials include dihydroperimidine squarylium dyes (described in US Pat. No. 5,380,635 and Japanese Patent Application No. 8-189817) and cyanine dyes (JP-A No. No. 62-123454, No. 3-138640, No. 3
-21542, 3-226736, 5-31
Nos. 3305 and 6-43583, Japanese Patent Application No. 7-435.
269097 and EP 0430244), pyrylium dyes (JP-A-3-13864).
Nos. 0 and 3-21542) and diimmonium dyes (JP-A-3-138640 and JP-A-3-2115).
No. 42), pyrazolopyridone dyes (described in JP-A-2-282244), indoaniline dyes (described in JP-A-5-323500 and JP-A-5-323501), polymethine dyes (described in JP-A-3-26765). Nos. 4,190,343 and EP 37796.
No. 1), oxonol dyes (JP-A-3-93)
No. 46), anthraquinone dyes (Japanese Unexamined Patent Publication No.
13654), a naphthalocyanine dye (described in US Pat. No. 5,099,899) and a naphtholactam dye (described in European Patent 568,267).

[Production of Cellulose Acetate Film]
It is preferable to produce a cellulose acetate film by a solvent casting method. In the solvent casting method, a film is manufactured using a solution (dope) in which cellulose acetate is dissolved in an organic solvent. The organic solvent is
It may contain a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. preferable. Ethers, ketones and esters may have a cyclic structure. Functional groups of ether, ketone and ester (i.e., -O
-, -CO-, and -COO-) can also be used as the organic solvent.
The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any one of the functional groups.

Examples of the ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of the ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more types of functional groups include
Includes 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen atoms in halogenated hydrocarbons is preferably 25 to 75 mol%, and preferably 3 to 75 mol%.
The content is more preferably 0 to 70 mol%, still more preferably 35 to 65 mol%, and 40 to 60 mol%.
Most preferably, it is mol%. Methylene chloride is a typical halogenated hydrocarbon. Two or more organic solvents may be used as a mixture.

A cellulose acetate solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (normal temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a usual solvent casting method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent. The amount of cellulose acetate is adjusted so that the obtained solution contains 10 to 40% by weight. More preferably, the amount of cellulose acetate is from 10 to 30% by weight. In the organic solvent (main solvent), any additives described below may be added. The solution can be prepared by stirring cellulose acetate and an organic solvent at normal temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heating conditions. Specifically, the cellulose acetate and the organic solvent are put in a pressurized container and hermetically sealed, and the mixture is stirred while being heated under pressure to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then placed in a container. Moreover, you may put in a container sequentially. The container must be configured to be able to stir. The container can be pressurized by injecting an inert gas such as nitrogen gas. Further, an increase in the vapor pressure of the solvent due to heating may be used.
Alternatively, each component may be added under pressure after the container is sealed. When heating, it is preferable to heat from outside the container. For example, a jacket-type heating device can be used. Alternatively, a plate heater may be provided outside the container, and the entire container may be heated by circulating the liquid through piping. It is preferable to provide a stirring blade inside the container and stir using the stirring blade. The stirring blade preferably has a length reaching the vicinity of the container wall. At the end of the stirring blade, a scraping blade is preferably provided to renew the liquid film on the container wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Dissolve each component in the solvent in the container.
The prepared dope is taken out of the vessel after cooling, or is taken out and then cooled using a heat exchanger or the like.

The solution can be prepared by the cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved even in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can dissolve cellulose acetate by an ordinary dissolution method, the cooling dissolution method has an effect that a uniform solution can be obtained quickly. In the cooling dissolution method, first, cellulose acetate is gradually added to an organic solvent at room temperature while stirring. Preferably, the amount of cellulose acetate is adjusted to be 10 to 40% by weight in the mixture. More preferably, the amount of cellulose acetate is from 10 to 30% by weight. Further, an optional additive described below may be added to the mixture.

Next, the mixture is cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -10 ° C).
To -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon such cooling, the mixture of cellulose acetate and the organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more.
Most preferably, the temperature is at least ° C / min. The cooling rate is preferably as fast as possible, but 10,000 ° C./sec is the theoretical upper limit, 1000 ° C./sec is the technical upper limit, and
00 ° C / sec is a practical upper limit. The cooling rate is
This is a value obtained by dividing the difference between the temperature at which the cooling is started and the final cooling temperature by the time from when the cooling is started to when the final cooling temperature is reached.

Further, the temperature is raised to 0 to 200 ° C (preferably 0 to 150 ° C, more preferably 0 to 120 ° C,
When heated to (most preferably 0 to 50 ° C.), the cellulose acetate dissolves in the organic solvent. The temperature may be raised only by leaving it at room temperature or may be heated in a warm bath. The heating rate is preferably 4 ° C./min or more, and 8 ° C./min.
Minutes or more, and most preferably 12 ° C./minute or more. The heating rate is preferably as high as possible, but the theoretical upper limit is 10,000 ° C./sec.
0 ° C./sec is a technical upper limit, and 100 ° C./sec is a practical upper limit. Note that the heating rate is a value obtained by dividing the difference between the temperature at which heating is started and the final heating temperature by the time from when the heating is started until the final heating temperature is reached. . As described above, a uniform solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution.

In the cooling dissolution method, it is desirable to use a closed container in order to avoid water contamination due to condensation during cooling. Also, in the cooling and heating operation, pressurization during cooling,
By reducing the pressure during the heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container. According to the differential scanning calorimetry (DSC), a 20% by weight solution of cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) dissolved in methyl acetate by a cooling dissolution method was 3%.
A pseudo phase transition point between the sol state and the gel state exists near 3 ° C., and below this temperature, the gel state becomes uniform. Therefore,
This solution must be stored at a temperature equal to or higher than the quasi phase transition temperature, preferably at a temperature of about 10 ° C. plus the gel phase transition temperature. However, the pseudo phase transition temperature varies depending on the average acetylation degree of cellulose acetate, the average degree of viscosity polymerization, the solution concentration, and the organic solvent used.

From the prepared cellulose acetate solution (dope), a cellulose acetate film is produced by a solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. It is preferable that the surface of the drum or the band is finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. Nos. 2,336,310 and 23,676.
No. 03, No. 2492078, No. 2492977, No. 2492978, No. 2607704, No. 27390
Nos. 69 and 2739070, British Patent 640731
Nos. 736892 and JP-B-45-455.
No. 4, No. 49-5614, JP-A-60-176834.
And JP-A-60-203430 and JP-A-62-115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.
It is preferable to dry the film by blowing it for 2 seconds or more.
Strip the obtained film from the drum or band,
Furthermore, the residual solvent can be evaporated by drying with high-temperature air having a temperature sequentially changed from 100 to 160 ° C. The above method is described in JP-B-5-17844. According to this method, the time from casting to stripping can be reduced. In order to carry out this method, it is necessary that the dope gels at the surface temperature of the drum or band during casting. The solution (dope) prepared according to the present invention satisfies this condition. The thickness of the film to be produced is preferably from 40 to 120 μm, more preferably from 70 to 100 μm.

A plasticizer can be added to the cellulose acetate film in order to improve the mechanical properties or to increase the drying speed. As a plasticizer,
Phosphate or carboxylate esters are used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCC).
P) is included. Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalate esters include dimethyl phthalate (DM
P), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACT
E) and tributyl O-acetylcitrate (OACT
B) is included. Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate,
It includes dibutyl sebacate and various trimellitate esters. Phthalate ester plasticizers (DMP, DE
P, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The amount of the plasticizer added is 0.1 to 25 times the amount of the cellulose ester.
%, More preferably 1 to 20% by weight, most preferably 3 to 15% by weight.

A deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) may be added to the cellulose acetate film. Regarding the deterioration inhibitor, see JP-A-3-19920.
No. 1, 5-1907073, 5-194789
And JP-A-5-271471 and JP-A-6-107854. The amount of the deterioration inhibitor added is preferably 0.01 to 1% by weight, more preferably 0.01 to 0.2% by weight of the solution (dope) to be prepared. If the amount is less than 0.01% by weight, the effect of the deterioration inhibitor is hardly recognized. 1% by weight
Exceeding the limit may cause bleed-out (bleeding-out) of the deterioration inhibitor to the film surface. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

The cellulose acetate film is further subjected to a stretching treatment to obtain a refractive index (refractive index n in the in-plane slow axis direction).
It is preferable to adjust x, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction. Cellulose acetate has a positive intrinsic birefringence. Therefore, the refractive index increases in the direction in which the cellulose chains are oriented.
When a polymer having a positive intrinsic birefringence is stretched, the refractive index usually becomes nx> ny ≧ nz. This is because the x-component of the polymer chain oriented in the in-plane direction is increased by stretching, and the z-component is minimized. This allows
The relationship of 1 ≦ (nx−nz) / (nx−ny) can be satisfied. Further, (nx-nz) / (nx-n
In order to satisfy the relationship of y) ≦ 2, it is sufficient to control the stretching ratio of uniaxial stretching or adjust the refractive index by performing unbalanced biaxial stretching. Specifically, a maximum stretching ratio SA and a stretching ratio S in a direction perpendicular to the stretching direction are set.
B so that 1 <SA / SB ≦ 3,
Uniaxial stretching or unbalanced biaxial stretching may be performed. The stretching ratio is a relative value when the length before stretching is set to 1. SB may be a value less than 1 (in other words, contract). If the relationship of the above expression is satisfied, SB may be a value less than 1. Further, the stretching ratio is adjusted so that the front retardation is λ / 4 or λ / 2. The stretching process is a simultaneous process,
It may be a sequential process.

[Circularly Polarizing Plate] The λ / 4 plate and the polarizing film are
A circularly polarizing plate is obtained by laminating such that the angle between the in-plane slow axis of the four plates and the polarizing axis of the polarizing film is substantially 45 °.
Substantially 45 ° means 40 to 50 °. The angle between the in-plane slow axis of the λ / 4 plate and the polarization axis of the polarizing film is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 47 °. Is more preferable, and most preferably 44 to 46 °. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. It is preferable to provide a transparent protective film on the surface of the polarizing film opposite to the λ / 4 plate.

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EXAMPLES Example 1 (Preparation of Dope A) At room temperature, the average acetylation degree was 60.9.
%, Cellulose acetate 12 having a viscosity average degree of polymerization of 298
0 parts by weight, 9.36 parts by weight of triphenyl phosphate,
4.68 parts by weight of biphenyl diphenyl phosphate, 357.80 parts by weight of methylene chloride, 65.
45 parts by weight and 13.09 parts by weight of n-butanol were mixed to prepare a cellulose acetate solution (dope A).

(Preparation of Dope E) At room temperature, 24.41 parts by weight of cellulose acetate having an average acetylation degree of 55.0% and a viscosity average degree of polymerization of 370, 1.23 parts by weight of triphenyl phosphate, and 0.62 parts of biphenyl diphenyl phosphate. Parts by weight, the following retardation increasing agent 1.2
0 parts by weight, 337.74 parts by weight of methylene chloride, 61.78 parts by weight of methanol and 12.3 of n-butanol.
6 parts by weight were mixed to prepare a cellulose acetate solution (dope E).

[0041]

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(Preparation of Cellulose Acetate Film)
454.5 parts by weight of dope A and 439.3 parts by weight of dope E were mixed and stirred. The mixed dope was cast on a glass plate, dried at room temperature for 1 minute, and then dried at 45 ° C. for 5 minutes. The residual amount of the solvent after drying was 30% by weight. The cellulose acetate film was peeled off from the glass plate, fixed on an aluminum frame, and dried at 100 ° C. for 10 minutes. The residual amount of the solvent after drying was 5 to 10% by weight.
The film was stretched in a direction parallel to the casting direction. The thickness of the obtained film was 98 μm.

(Measurement of average degree of acetylation) The average degree of acetylation was measured by a saponification method. Sections of dried film (about 2
g) was precisely weighed and dissolved in a mixed solvent of 120 ml of acetone and 70 ml of dimethyl sulfoxide. 1N sodium hydroxide solution was added and saponified at 25 ° C. for 2 hours. Phenolphthalein was added as an indicator and excess sodium hydroxide was titrated with 1N sulfuric acid (concentration factor: f). A blank test was performed in the same manner as described above. The average degree of acetylation of the film was calculated by the following equation. Average degree of acetylation (%) = {6.05 × (BA) × F} /
In the formula, A is the amount (ml) of 1N sulfuric acid required for titration of the sample.
B is the amount (ml) of 1N sulfuric acid required for the blank test; and W is the amount of the precisely weighed section. The results are shown in Table 1.

(Measurement of Haze) Haze meter (Model
The haze was measured using 1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1.

(Measurement of Retardation) Retardation values of the obtained cellulose acetate film (retardation plate) at wavelengths of 450 nm, 550 nm and 590 nm using an ellipsometer (M-150, manufactured by JASCO Corporation). (Re) was measured. Result is,
It is shown in Table 1. However, 121.2 nm, 1
38.0 nm and 147.1 nm. Therefore,
This cellulose acetate film achieved λ / 4 in a wide wavelength range. Further, from the measurement of the refractive index by the Abbe refractometer and the measurement of the angle dependence of the retardation, the refractive index nx in the in-plane slow axis direction and the refractive index in the direction perpendicular to the in-plane slow axis at a wavelength of 550 nm are obtained. ny and the refractive index nz in the thickness direction are obtained, and (nx−nz) / (nx−
ny) was calculated to be 1.53.

(Production of Circularly Polarizing Plate) A transparent protective film, a polarizing film and the produced retardation plate were laminated in this order to obtain a circularly polarizing plate. The angle between the slow axis of the phase difference plate and the polarizing axis of the polarizing film is
Adjusted to 45 °. When the optical properties of the obtained circularly polarizing plates were examined, they were found to be in a wide wavelength range (450 to 590 n).
In m), almost perfect circularly polarized light was achieved.

Example 2 (Preparation of Dope G) At room temperature, the average degree of acetylation was 58.5.
%, Cellulose acetate 6 having a viscosity average degree of polymerization of 455
0.00 parts by weight, 4.08 parts by weight of triphenyl phosphate, 2.92 parts by weight of biphenyldiphenyl phosphate, the retardation increasing agent 1.20 used in Example 1
Parts by weight, 443.90 parts by weight of methylene chloride, 81.20 parts by weight of methanol and 16.24 of n-butanol
The parts by weight were mixed to prepare a cellulose acetate solution (dope G).

(Preparation of Cellulose Acetate Film)
285.3 parts by weight of the dope A prepared in Example 1 and 609.5 parts by weight of the dope G were mixed and stirred. The mixed dope was cast on a glass plate and dried at room temperature for 1 minute.
Dry for 5 minutes at ° C. The residual amount of the solvent after drying was 30% by weight. The cellulose acetate film was peeled off from the glass plate and fixed to an aluminum frame.
Dry at 10 ° C. for 10 minutes. The residual amount of the solvent after drying is 5 to 1
It was 0% by weight. The film was stretched in a direction parallel to the casting direction. The thickness of the obtained film was 102 μm. The average degree of acetylation, haze, and retardation of the obtained cellulose acetate film (retardation film) were measured in the same manner as in Example 1. The results are shown in Table 1.

(Preparation of Circularly Polarizing Plate) A transparent protective film, a polarizing film and the prepared retardation plate were laminated in this order to obtain a circularly polarizing plate. The angle between the slow axis of the phase difference plate and the polarizing axis of the polarizing film is
Adjusted to 45 °. When the optical properties of the obtained circularly polarizing plates were examined, they were found to be in a wide wavelength range (450 to 590 n).
In m), almost perfect circularly polarized light was achieved.

Example 3 (Preparation of dope B) At room temperature, the average acetylation degree was 60.9.
%, Cellulose acetate 12 having a viscosity average degree of polymerization of 298
0 parts by weight, 9.36 parts by weight of triphenyl phosphate,
4.68 parts by weight of biphenyl diphenyl phosphate, 561.77 parts by weight of methylene chloride and methanol 4
8.5985 parts by weight were mixed to prepare a cellulose acetate solution (dope B).

(Preparation of Dope F) At room temperature, 24.41 parts by weight of cellulose acetate having an average acetylation degree of 55.0% and a viscosity average degree of polymerization of 370, 1.90 parts by weight of triphenyl phosphate, and 0.95 parts by weight of biphenyl diphenyl phosphate. By weight, 1.20 parts by weight of the retardation increasing agent used in Example 1, 114.26 parts by weight of methylene chloride, and 9.94 parts by weight of methanol were mixed to prepare a cellulose acetate solution (dope F).

(Preparation of Cellulose Acetate Film)
Dope B593.20 parts by weight and dope F151.46
Parts by weight and stirred. The mixed dope was cast on a glass plate, dried at room temperature for 1 minute, and then dried at 45 ° C. for 5 minutes. The residual amount of the solvent after drying was 30% by weight. The cellulose acetate film was peeled off from the glass plate, fixed on an aluminum frame, and dried at 100 ° C. for 10 minutes. The residual amount of the solvent after drying was 5 to 10% by weight. The film was stretched in a direction parallel to the casting direction. The thickness of the obtained film was 99 μm. The average degree of acetylation, haze, and retardation of the obtained cellulose acetate film (retardation film) were measured in the same manner as in Example 1. The results are shown in Table 1.

(Preparation of Circular Polarizing Plate) A transparent protective film, a polarizing film and the prepared retardation plate were laminated in this order to obtain a circular polarizing plate. The angle between the slow axis of the phase difference plate and the polarizing axis of the polarizing film is
Adjusted to 45 °. When the optical properties of the obtained circularly polarizing plates were examined, they were found to be in a wide wavelength range (450 to 590 n).
In m), almost perfect circularly polarized light was achieved.

Example 4 (Preparation of Dope H) At room temperature, the average degree of acetylation was 58.5.
%, Cellulose acetate 6 having a viscosity average degree of polymerization of 455
0.00 parts by weight, 4.68 parts by weight of triphenyl phosphate, 2.34 parts by weight of biphenyldiphenyl phosphate, 1.20 retardation increasing agent used in Example 1.
By weight, 280.89 parts by weight of methylene chloride and 24.43 parts by weight of methanol were mixed to prepare a cellulose acetate solution (dope H).

(Preparation of Cellulose Acetate Film)
372.33 parts by weight of the dope B prepared in Example 3 and 373.54 parts by weight of the dope H were mixed and stirred. The mixed dope was cast on a glass plate and dried at room temperature for 1 minute.
Dry at 45 ° C. for 5 minutes. Solvent residue after drying is 30
% By weight. After the cellulose acetate film was peeled off from the glass plate and fixed to an aluminum frame,
Dry at 00 ° C. for 10 minutes. The residual amount of the solvent after drying was 5 to 10% by weight. The film was stretched in a direction parallel to the casting direction. The thickness of the obtained film was 98 μm. The average degree of acetylation, haze, and retardation of the obtained cellulose acetate film (retardation film) were measured in the same manner as in Example 1. The results are shown in Table 1.

(Preparation of Circularly Polarizing Plate) A transparent protective film, a polarizing film and the prepared retardation plate were laminated in this order to obtain a circularly polarizing plate. The angle between the slow axis of the phase difference plate and the polarizing axis of the polarizing film is
Adjusted to 45 °. When the optical properties of the obtained circularly polarizing plates were examined, they were found to be in a wide wavelength range (450 to 590 n).
In m), almost perfect circularly polarized light was achieved.

Example 5 (Preparation of dope C) At room temperature, the average degree of acetylation was 55.0.
%, Cellulose acetate 2 having a viscosity average degree of polymerization of 370
4.40 parts by weight, 95.60 parts by weight of cellulose acetate having an average degree of acetylation of 60.9% and a viscosity average degree of polymerization of 298, 9.36 parts by weight of triphenyl phosphate, 4.68 parts by weight of biphenyl diphenyl phosphate, Example 1 1.20 parts by weight of the retardation increasing agent used in the above, 622.84 parts by weight of methylene chloride, 113.93 parts by weight of methanol and 22.79 parts by weight of n-butanol were mixed to prepare a cellulose acetate solution (dope C). did.

(Preparation of Cellulose Acetate Film)
The dope C was cast on a glass plate, dried at room temperature for 1 minute, and then dried at 45 ° C. for 5 minutes. The residual amount of the solvent after drying was 30% by weight. The cellulose acetate film was peeled off from the glass plate, fixed on an aluminum frame, and dried at 100 ° C. for 10 minutes. The residual amount of the solvent after drying was 5 to 10% by weight. The film was stretched in a direction parallel to the casting direction. The thickness of the obtained film is 10
It was 0 μm. The average degree of acetylation, haze, and retardation of the obtained cellulose acetate film (retardation film) were measured in the same manner as in Example 1. The results are shown in Table 1.

(Preparation of Circularly Polarizing Plate) A transparent protective film, a polarizing film and the prepared retardation plate were laminated in this order to obtain a circularly polarizing plate. The angle between the slow axis of the phase difference plate and the polarizing axis of the polarizing film is
Adjusted to 45 °. When the optical properties of the obtained circularly polarizing plates were examined, they were found to be in a wide wavelength range (450 to 590 n).
In m), almost perfect circularly polarized light was achieved.

[0060]

Table 1 Table 1 Retardation (nm) phase difference Plate Average acetylation degree Haze 450 nm 550 nm 590 nm ──────────────────────────────────── Example 1 59. 6% 1.2% 121.2 138.0 147.1 Example 2 59.7% 0.7% 119.3 140.7 149.2 Example 3 59.6% 1.3% 122.7 137 5.5 146.7 Example 4 59.7% 0.9% 120.1 140.2 148.7 Example 5 59.7% 1.0% 120.2 139.8 148.3 ───────────────────────────────

Example 6 (Preparation of retardation plate) The thickness of the obtained film was 200 μm.
m, a cellulose acetate film was produced in the same manner as in Example 1, except that the amount of the dope applied was changed. About the obtained cellulose acetate film (retardation plate), the wavelength was 450 nm and 550 nm using an ellipsometer (M-150, manufactured by JASCO Corporation).
Values at 590 and 590 nm (Re)
Were measured, 240.6 nm and 27, respectively.
It was 3.5 nm and 289.9 nm. Therefore, this cellulose acetate film has λ over a wide wavelength range.
/ 2 was achieved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 C08L 1:12 C08L 1:12 F Terms (reference) 2H049 BA02 BA03 BA06 BA07 BA25 BB03 BB11 BB49 BB66 BC03 BC21 4F071 AA09 AC12 AE22 AF31Y AH19 BA02 BB02 BB07 BC01 4F210 AA01 AG01 AH73 QC02 QG01 QG18 4J002 AB02W AB02X EU0206 EU166 EU16676 EU166

Claims (13)

[Claims] 1. A mixture of two or more cellulose acetates having different degrees of acetylation, wherein the difference between the degree of acetylation between the cellulose acetate having the highest degree of acetylation and the cellulose acetate having the lowest degree of acetylation is 2%. 2.0-6.0%, cellulose acetate film characterized by the above-mentioned. 2. The average acetylation degree of the entire mixture of cellulose acetate is 55.0 to 61.5%.
The cellulose acetate film according to the above. 3. A cellulose acetate film comprising a mixture of two or more cellulose acetates having different degrees of acetylation, wherein the cellulose acetate film comprises a mixture of two or more cellulose acetates having different degrees of acetylation, and a cellulose acetate having a maximum degree of acetylation and a minimum degree of acetylation. The difference in the degree of acetylation from cellulose acetate having the following is 2.0 to 6.0%, and the retardation value (Re450) measured at a wavelength of 450 nm is 100 to 1
A retardation plate having a retardation value of 25 nm, a retardation value (Re590) measured at a wavelength of 590 nm of 120 to 160 nm, and satisfying a relationship of Re590-Re450 ≧ 2 nm. 4. A retardation value (Re450) measured at a wavelength of 450 nm is from 108 to 120 nm,
The retardation value (Re5) measured at a wavelength of 550 nm
50) is 125 to 142 nm, and the wavelength is 590 nm.
Retardation value (Re590) measured at 130
To 152 nm and Re590-Re55
The retardation plate according to claim 3, wherein a relationship of 0 ≧ 2 nm is satisfied. 5. The retardation film according to claim 3, wherein the cellulose acetate film is a stretched film. 6. The retardation film according to claim 3, wherein the cellulose acetate film contains a compound having at least two aromatic rings as a retardation increasing agent. 7. The refractive index nx in the in-plane slow axis direction of the cellulose acetate film, the refractive index ny in the direction perpendicular to the in-plane slow axis and the refractive index nz in the thickness direction are 1 ≦ (nx
The retardation plate according to claim 3, wherein a relationship of -nz) / (nx-ny) ≤ 2 is satisfied. 8. A circle in which a retardation plate and a linear polarizing film are laminated such that the angle between the in-plane slow axis of the retardation plate and the polarization axis of the linear polarizing film is substantially 45 °. A polarizing plate,
The phase difference plate is made of one piece of cellulose acetate film, and the cellulose acetate film is made of a mixture of two or more types of cellulose acetate having different degrees of acetylation,
The difference in the degree of acetylation between cellulose acetate having the highest degree of acetylation and cellulose acetate having the lowest degree of acetylation,
2.0 to 6.0%, and the retardation value (Re450) measured at a wavelength of 450 nm is 100 to 125.
and a retardation value (Re590) measured at a wavelength of 590 nm of 120 to 160 nm and satisfying a relationship of Re590-Re450 ≧ 2 nm. 9. A cellulose acetate film comprising a mixture of two or more cellulose acetates having different degrees of acetylation, wherein the cellulose acetate film has a maximum degree of acetylation and a minimum degree of acetylation. The difference in the degree of acetylation from cellulose acetate having a value of 2.0 to 6.0% and the retardation value (Re450) measured at a wavelength of 450 nm of 200 to 2
A retardation film having a retardation value of 50 nm, a retardation value (Re590) measured at a wavelength of 590 nm of 240 to 320 nm, and satisfying the relationship of Re590-Re450 ≧ 4 nm. 10. The retardation value (Re450) measured at a wavelength of 450 nm is 216 to 240 nm, and the retardation value (R450) measured at a wavelength of 550 nm is (R450).
e550) is from 250 to 284 nm and the wavelength is 590.
The retardation value (Re590) measured in nm is 2
60-304 nm, and Re590-Re
The retardation plate according to claim 9, which satisfies a relationship of 550 ≥ 4 nm. 11. The retardation film according to claim 9, wherein the cellulose acetate film is a stretched film. 12. The retardation film according to claim 9, wherein the cellulose acetate film contains a compound having at least two aromatic rings as a retardation increasing agent. 13. The refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction of the cellulose acetate film are 1 ≦ (n
The phase difference plate according to claim 9, which satisfies a relationship of (x-nz) / (nx-ny) ≤2.