JP2002071948A - Optical retardation plate and circularly polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the viewing angle of a liquid crystal display device by attaining a function of λ/4 plate over a wide wavelength region using a sheet of polymer film. SOLUTION: The optical retardation plate, which is composed of a sheet of polymer film having a retardation value measured at 450 nm wavelength (Re450) within the range of 100-125 nm, having a retardation value measured at 590 nm wavelength (Re590) within the range of 120-160 nm, satisfying an inequality of Re590-Re450>=2 nm and having a thickness within the range of 10-70 μm, is used for the liquid crystal display device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate made of a polymer film and a circularly polarizing plate using the same.

[0002]

2. Description of the Related Art Retardation plates such as λ / 4 plate and λ / 2 plate have many uses related to antireflection films and liquid crystal display devices. However, even if it is referred to as a λ / 4 plate or a λ / 2 plate, most achieve λ / 4 or λ / 2 at a specific wavelength. JP-A-5-27118 and JP-A-5-27119 disclose that 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. A phase difference plate is disclosed. The difference in retardation between the two films is λ over the entire visible light range.
If it is / 4 or λ / 2, the retardation plate theoretically functions as a λ / 4 plate or a λ / 2 plate over the entire visible light range.

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. Furthermore, it has been found that even when a λ / 4 plate or a λ / 2 plate made of one polymer film is incorporated in a liquid crystal display device and used, the viewing angle of the liquid crystal display device is not improved as expected. The reflection type liquid crystal display device using one film has a contrast equal to or higher than that of the above-mentioned two-type λ / 4 film, but the mobile terminal (the main use of the reflection type liquid crystal display device) In particular, when used as a display having a large area, it was found that there was a problem in durability due to distortion such as heat. Specifically, heat generated from the backlight of the liquid crystal display device causes distortion of the film, causing unevenness of the retardation value in the film surface and a change in the slow axis direction, and the liquid crystal cell in black display. , The transmittance of the peripheral portion increases, and “frame-shaped display unevenness” occurs. The inventor's earnest research has shown that this distortion has a correlation with the thickness of the retardation plate. As will be described in detail later, it has been found that when the thickness is increased, the frame-shaped transmittance increases remarkably, and as the thickness is reduced, the frame-shaped transmittance is suppressed from increasing. That is, it is necessary to reduce the thickness of the phase difference plate in order to suppress in-plane fluctuation of the optical characteristics of the phase difference plate caused by a change in environmental conditions in which the phase difference plate is used.

An object of the present invention is to provide a single sheet having excellent durability,
Another object of the present invention is to provide a retardation plate that achieves λ / 4 or λ / 2 in a wide wavelength region. Another object of the present invention is to provide a circularly polarizing plate which is excellent in durability and achieves circularly polarized light in a wide wavelength range, and has a high display quality using the same, and a liquid crystal display having reduced frame-shaped display unevenness. It is to provide a device.

[0006]

The object of the present invention has been attained by the following retardation plates (1) to (5) and (7) to (11) and a circularly polarizing plate (6). (1) a retardation value (Re450) measured at a wavelength of 450 nm is in the range of 100 to 125 nm,
The retardation value (Re5) measured at a wavelength of 590 nm
90) is in the range of 120 to 160 nm;
A retardation plate comprising a single polymer film satisfying a relationship of 0-Re450 ≧ 2 nm and having a thickness in a range of 10 to 70 μm. (2) a retardation value (Re450) measured at a wavelength of 450 nm is in the range of 108 to 120 nm,
The retardation value (Re5) measured at a wavelength of 550 nm
50) is in the range of 125 to 142 nm and the wavelength 59
The retardation value (Re590) measured at 0 nm is in the range of 130 to 152 nm, and Re590-Re
A retardation plate comprising a single polymer film satisfying a relationship of 550 ≧ 2 nm and having a thickness in a range of 10 to 70 μm. (3) The retardation plate according to (1), wherein the polymer film is a cellulose acetate film.

(4) The cellulose acetate film is a cellulose acetate having an acetylation degree of 57.0 to 61.5%, and an aromatic compound having at least two aromatic rings with respect to 100 parts by mass of the cellulose acetate. The retardation plate according to (3), wherein 0.01 to 20 parts by mass is contained. (5) The retardation plate according to (1), wherein the polymer film is a stretched cellulose acetate film. (6) A circularly polarizing plate 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 transmission axis of the linear polarizing film is substantially 45 °. And the retardation plate has a retardation value (R) measured at a wavelength of 450 nm.
e450) is in the range of 100 to 125 nm, and the retardation value (Re59) measured at a wavelength of 590 nm.
0) is in the range of 120 to 160 nm, and Re590
-A circularly polarizing plate comprising a single polymer film satisfying a relationship of Re450 ≧ 2 nm and having a thickness in a range of 10 to 70 μm.

(7) The retardation value (Re450) measured at a wavelength of 450 nm is in a range of 200 to 250 nm, the retardation value (Re590) measured at a wavelength of 590 nm is in a range of 240 to 320 nm, and Re590-Re450 ≧ Satisfies the relationship of 4nm,
A retardation plate comprising a single polymer film having a thickness in the range of 10 to 70 μm. (8) a retardation value (Re450) measured at a wavelength of 450 nm is in a range of 216 to 240 nm,
The retardation value (Re5) measured at a wavelength of 550 nm
50) is in the range of 250 to 284 nm and the wavelength 59
The retardation value (Re590) measured at 0 nm is in the range of 260 to 304 nm, and Re590-Re
A retardation plate comprising a single polymer film satisfying a relationship of 550 ≧ 4 nm and having a thickness in a range of 10 to 70 μm.

(9) The retardation plate according to (7), wherein the polymer film is a cellulose acetate film. (10) The cellulose acetate film is prepared by adding a cellulose acetate having an acetylation degree of 57.0 to 61.5% and an aromatic compound having at least two aromatic rings to 100 parts by mass of the cellulose acetate. The phase difference plate according to (9), wherein the retardation plate contains from 01 to 20 parts by mass. (11) The retardation plate according to (7), wherein the polymer film is a stretched cellulose acetate film.

[0010]

The inventor of the present invention has found that by adjusting the material of the polymer and the manufacturing method, the λ / 4 or λ over a wide wavelength range can be obtained.
/ 2 has been successfully provided. Further, by using this retardation plate attached to a liquid crystal display device, the viewing angle is remarkably improved. Further, by adjusting the thickness of the retardation plate, the fluctuation of the in-plane optical characteristics due to a change in environmental conditions is improved, and the frame-shaped display unevenness of the liquid crystal display device can be eliminated. As a result, a liquid crystal display device having a thickness equal to or less than the conventional thickness and having excellent durability can be obtained. Since a retardation plate capable of achieving λ / 4 or λ / 2 in a wide wavelength range using a single polymer film has been obtained, a step of laminating two conventional polymer films while strictly adjusting the angle. Became unnecessary.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION [Retardation Plate] When a retardation plate is used as a λ / 4 plate, the retardation value (Re450) measured at a wavelength of 450 nm is 100 to 125 nm.
And the retardation value (Re590) measured at a wavelength of 590 nm is from 120 to 160 nm, and satisfies the relationship of Re590-Re450 ≧ 2 nm. More preferably, Re590-Re450 ≧ 5 nm, and most preferably, Re590-Re450 ≧ 10 nm. The retardation value (Re450) measured at a wavelength of 450 nm is 108 to 120 nm, the retardation value (Re550) measured at a wavelength of 550 nm is 125 to 142 nm, and the
Retardation value measured at 90 nm (Re590)
Is 130 to 152 nm, and Re590-
It is preferable to satisfy the relationship of Re550 ≧ 2 nm.
More preferably, Re590-Re550 ≧ 5 nm, and most preferably, Re590-Re550 ≧ 10 nm. Also, Re550−Re450 ≧ 10
nm is also preferable. In addition, the thickness of the retarder is
It is in the range of 10 to 70 μm. The thickness of the retarder is 2
More preferably, it is in the range of 0 to 60 μm.
Most preferably, it is in the range of 0 to 50 μm.

When a retardation plate is used as a λ / 2 plate, the retardation value (R
e450) is from 200 to 250 nm, and the wavelength 5
Retardation value measured at 90 nm (Re590)
Is 240 to 320 nm, and Re590-
The relationship of Re450 ≧ 4 nm is satisfied. Re590-R
e450 ≧ 10 nm, more preferably
590-Re450 ≧ 20 nm The retardation value (Re) measured at a wavelength of 450 nm is most preferable.
450) is 216 to 240 nm, and the wavelength is 550 n
The retardation value (Re550) measured in m is 25
0 to 284 nm, and the retardation value (Re590) measured at a wavelength of 590 nm is 260 to 304 n.
m, and preferably satisfy the relationship of Re590-Re550 ≧ 4 nm. Also, Re590-Re
More preferably, 550 ≧ 10 nm.
Most preferably, 90-Re550 ≧ 20 nm. Further, it is also preferable that Re550−Re450 ≧ 20 nm. The thickness of the retardation plate is 10 to 70.
in the range of μm. The thickness of the phase difference plate is 20 to 60 μ
m, more preferably 30 to 50 μm.
Most preferably, it is in the range of m.

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 of the retardation plate in the slow axis direction (in-plane maximum 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.

Further, it is preferable that one retardation plate of the present invention satisfies the following expression. 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.

A retardation plate having the above optical properties can be obtained from a single cellulose ester film containing a retardation increasing agent. The retardation value of the retardation plate and its wavelength dependence are as follows: (1) adjustment of the composition (particularly average degree of acetylation) of the cellulose ester, (2) adjustment of the type and amount of the retardation increasing agent, and (3). It can be controlled by the thickness of the film. In particular, the use of the retardation increasing agent (2) makes it possible to use a cellulose ester film, which was conventionally considered to be optically isotropic, as a retardation film. The retardation plate having the above optical properties can be manufactured by the following materials and methods.

[Polymer Film] As the polymer film used in the present invention, it is preferable to use a polymer film having a light transmittance of 80% or more. For polymer films, those that do not easily develop birefringence due to external force,
That is, those having a small photoelastic coefficient are preferable. Examples of the polymer that forms the polymer film include cellulosic polymers, norbornene-based polymers such as Arton (manufactured by JSR Corporation) and Zeonex (manufactured by Zeon Corporation), and polymethyl methacrylate. No. As the cellulosic polymer, a cellulose ester is preferable, and a lower fatty acid ester of cellulose is more preferable. The lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is
It is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Examples of cellulose acetate include triacetyl cellulose.

The viscosity average degree of polymerization (DP) of the polymer film is preferably at least 250,
More preferably, it is the above. Further, the polymer film preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a weight average molecular weight, Mn is a number average molecular weight) determined by gel permeation chromatography. Specific M
The value of w / Mn is preferably from 1.0 to 1.7, more preferably from 1.3 to 1.65, and most preferably from 1.4 to 1.6.

According to the inventor's intensive studies, the increase in the frame-shaped transmittance can be suppressed by a pressure-sensitive adhesive in which a dimensional change due to wet heat of a polymer film (retardation plate) interposed between a polarizing film and a liquid crystal cell is suppressed. It has been found that this is caused by the occurrence of birefringence (photoelasticity) due to the stress generated thereby. The transmittance has a correlation with the product of the developed birefringence and the thickness of the retardation plate (phase difference).
The transmittance increases. Accordingly, by reducing the thickness of the polymer film, the phase difference is reduced even if the same birefringence is exhibited, so that the frame-shaped increase in transmittance can be reduced. However, when the thickness of the polymer film is too small, problems such as poor handling arise. The thickness of the polymer film that keeps the balance between the in-plane optical characteristic fluctuation due to the change in environmental conditions using the retardation plate and the handling during the production of the retardation plate is as follows. The thickness of the polymer film is in the range of 10 to 70 μm. The thickness of the polymer film is more preferably in the range of 20 to 60 μm, and most preferably in the range of 30 to 50 μm.

As the polymer film used in the present invention, it is preferable to use a cellulose acetate film having an acetylation degree of 57.0 to 61.5%. The acetylation degree of the cellulose acetate film is 59.0 to 60.
It is preferably 5 and most preferably 59.5 to 60.0. The degree of acetylation means the amount of bound acetic acid per unit weight of cellulose. The degree of acetylation is ASTM:
D-817-91 (test method for cellulose acetate, etc.)
In accordance with the measurement and calculation of the degree of acetylation.

These polymer films preferably contain an ultraviolet absorber or the like. Also, Japanese Patent Application Laid-Open No. 7-3334
As described in JP-A No. 33, an adhesive layer (undercoat layer) may be provided on a polymer film. The thickness of the adhesive layer is preferably in the range of 0.1 to 2 μm, and 0.2 to 1 μm.
m is more preferably in the range of m.

[Retardation Control] In order to adjust the retardation of a polymer film, a method of applying an external force such as stretching is generally used.
Aromatic compounds having at least two aromatic rings, as described in 6A2, can also be used as retardation increasing agents. The aromatic compound is used in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of cellulose acetate.
Use in the range of parts by mass. The aromatic compound is preferably used in an amount of 0.05 to 15 parts by mass, based on 100 parts by mass of cellulose acetate, and 0.1 to 10 parts by mass.
More preferably, it is used in the range of parts by mass. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The number of aromatic rings in the aromatic compound is 2
To 20, preferably 2 to 12, more preferably 2 to 8, and most preferably 3 to 6. The bonding relationship between two aromatic rings is as follows: (a) when forming a condensed ring, (b)
It can be classified into a case where a single bond is directly bonded and a case where it is bonded via a (c) linking group (a spiro bond cannot be formed due to an aromatic ring). The connection relationship may be any of (a) to (c).

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 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, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring,
Phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxatiin ring, phenoxazine ring and thianthrene ring are 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. By joining two aromatic rings with two or more single bonds,
An aliphatic ring or a non-aromatic heterocyclic ring may be formed between 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 polymer film in order to adjust the retardation value at each wavelength. The infrared absorber is preferably used in an amount of 0.01 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, and more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the polymer. It is more preferably used in the range of 1 part by weight, and most preferably used in the range of 0.1 to 0.5 part by weight.
Two or more infrared absorbers may be used in combination. The infrared absorber preferably has a maximum absorption in a wavelength range of 750 to 1100 nm, and more preferably has a maximum absorption in a wavelength range of 800 to 1000 nm. It is preferred that the infrared absorber has substantially no absorption in the visible region.

It is preferable to use an infrared absorbing dye or an infrared absorbing pigment as the infrared absorbing agent, 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 infrared absorption function or absorption spectrum, 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 polymer film] It is preferable to produce a polymer film by a solvent casting method. In the solvent casting method, a film is manufactured using a solution (dope) in which a polymer material is dissolved in an organic solvent. The production of the polymer film of the present invention will be specifically described using cellulose acetate as an example. Organic solvents include ethers having 3 to 12 carbon atoms and 3 to 1 carbon atoms.
It is preferable to include a solvent selected from ketones having 2 carbon atoms, esters having 3 to 12 carbon atoms and halogenated hydrocarbons having 1 to 6 carbon atoms. Ethers, ketones and esters may have a cyclic structure. ether,
Functional groups of ketones and esters (ie, -O-,-
A compound having two or more of any of 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 mass. More preferably, the amount of cellulose acetate is 10 to 30% by mass. 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.

The components 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. It is preferable to adjust the amount of cellulose acetate so that the mixture contains 10 to 40% by mass. More preferably, the amount of cellulose acetate is 10 to 30% by mass. Further, an optional additive described below may be added to the mixture.

Next, the mixture is heated 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, this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C.,
When heated to the temperature (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 dew 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 differential scanning calorimetry (DSC), a 20% by mass solution of cellulose acetate (degree of acetylation: 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 maintained at a temperature equal to or higher than the pseudo 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 acetylation degree of cellulose acetate, the viscosity average polymerization degree, 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. It is preferable to add the above-mentioned retardation increasing agent to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting has a solid content of 1
It is preferable to adjust the concentration so as to be 8 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 US Pat. No. 2,336,310.
No. 2367603, No. 2492078, No. 24
No. 92977, No. 2492978, No. 2607704
Nos. 2739069 and 2739070, British Patent Nos. 640731 and 736892, JP-B-45-4554, JP-A-49-5614, and JP-A-6060.
-176834, 60-203430, 62-
It is described in each publication of No. 115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry by blowing on air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried with high-temperature air whose temperature is gradually changed from 100 to 160 ° C. to evaporate the residual solvent. 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.

Using the prepared cellulose acetate solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to produce a cellulose acetate film 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 10 to 40%. It is preferable that the surface of the drum or the band is finished in a mirror state.

When casting a plurality of cellulose acetate solutions of two or more layers, a plurality of cellulose acetate solutions can be cast, and a plurality of casting ports provided at intervals in the traveling direction of the support. Alternatively, a film containing cellulose acetate may be cast and laminated to form a film. For example, Japanese Patent Application Laid-Open No. 61-158414
, JP-A-1-122419, and JP-A-11-
The method described in each specification of 198285 can be used. The film can also be formed by casting a cellulose acetate solution from two casting ports. For example, Japanese Patent Publication No. 60-27562,
JP-A-94724, JP-A-61-947245, JP-A-61-104814, JP-A-61-158413,
Further, the method described in each specification of JP-A-6-134933 can be used. Also, Japanese Patent Application Laid-Open No. 56-162
No. 617, a cellulose acetate film casting method in which a flow of a high-viscosity cellulose acetate solution is wrapped with a low-viscosity cellulose acetate solution and the high- and low-viscosity cellulose acetate solutions are simultaneously extruded.

Further, by using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side in contact with the support surface. Films can also be made. For example, Japanese Patent Publication No. 44-2
No. 0235 can be mentioned.
The same cellulose acetate solution may be used for casting, or a different cellulose acetate solution may be used. In order to provide a function to a plurality of cellulose acetate layers, a cellulose acetate solution corresponding to the function may be extruded from each casting port. Further, the cellulose acetate solution of the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

In the conventional monolayer liquid, it is necessary to extrude a high-concentration and high-viscosity cellulose acetate solution in order to obtain a required film thickness. In this case, the stability of the cellulose acetate solution is poor and the This often causes problems, such as a bumpy failure or poor flatness. As a solution to this problem, by casting a plurality of cellulose acetate solutions from a casting port, it is possible to simultaneously extrude a high-viscosity solution onto a support, thereby improving the flatness and producing an excellent planar film. Not only can it be produced, but also by using a concentrated cellulose acetate solution, a reduction in the drying load can be achieved, and the production speed of the film can be increased.

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 mass, most preferably 3 to 15% by mass.

The cellulose acetate film may be added with a deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine). 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 mass, more preferably 0.01 to 0.2% by mass of the solution (dope) to be prepared. When the amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly recognized. 1% by mass
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 retardation of the cellulose acetate film can be adjusted by a stretching treatment. The stretching ratio is preferably 3 to 100%. The thickness of the cellulose acetate film is preferably from 10 to 70 μm, more preferably from 20 to 60 μm, and most preferably from 30 to 50 μm. Therefore,
The birefringence is 0.00196 to 0.
01375, more preferably 0.00168 to 0.006875, most preferably 0.1 to 0.0075.
00275 to 0.00458.

[Surface Treatment of Polymer Film] The polymer film is preferably subjected to a surface treatment. As a specific method, a corona discharge treatment, a glow discharge treatment, a flame treatment, an acid treatment, an alkali treatment, or an ultraviolet irradiation treatment is performed. From the viewpoint of maintaining the flatness of the film, the temperature of the polymer film in these treatments is preferably set to Tg (glass transition temperature) or lower. It is particularly preferable to perform an acid treatment or an alkali treatment from the viewpoint of adhesion between the polymer film and the polarizing film when producing a polarizing plate. Hereinafter, the alkali saponification treatment will be specifically described as an example. The alkali saponification treatment is preferably performed in a cycle of immersing the polymer film surface in an alkaline solution, neutralizing the surface with an acidic solution, washing with water, and drying. Examples of the alkali solution include a potassium hydroxide solution and a sodium hydroxide solution, and the specified concentration of hydroxide ions is preferably 0.1 N to 3.0 N, and more preferably 0.5 N to 2.0 N.
More preferably, it is N. The alkaline solution temperature is
The temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 ° C to 70 ° C. As described above, a retardation plate comprising the polymer film of the present invention can be manufactured.

[Circularly Polarizing Plate] The λ / 4 plate (retardation plate) of the present invention and the polarizing film are formed by setting the angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizing film substantially. A circularly polarizing plate is obtained by stacking at 45 °. Substantially 45 ° means 40 to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizing film is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 47 °. Is more preferred, and 44
It is most preferable that the angle is 46 ° 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 transmission 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 λ / 4. An ordinary cellulose acetate film may be used as the transparent protective film.

[Liquid Crystal Display Device] A retardation plate made of the above polymer film or a polarizing plate using the above polymer film is advantageously used for a liquid crystal display device.

FIG. 1 is a schematic diagram showing a basic configuration of a reflection type liquid crystal display device. The reflective liquid crystal display device shown in FIG. 1 includes, in order from the bottom, a lower substrate (1), a reflective electrode (2), a lower alignment film (3), a liquid crystal layer (4), an upper alignment film (5), and a transparent electrode ( 6), an upper substrate (7), a λ / 4 plate (8), and a polarizing film (9). The lower substrate (1) and the reflection electrode (2) constitute a reflection plate. The lower alignment film (3) to the upper alignment film (5) constitute a liquid crystal cell. The λ / 4 plate (8) can be arranged at an arbitrary position between the reflection plate and the polarizing film (9). In the case of color display, a color filter layer is further provided. The color filter layer is formed between the reflective electrode (2) and the lower alignment film (3), or between the upper alignment film (5) and the transparent electrode (6).
Is preferably provided between A reflective plate may be separately attached using a transparent electrode instead of the reflective electrode (2) shown in FIG. A metal plate is preferable as the reflector used in combination with the transparent electrode. If the surface of the reflector is smooth, only the specular reflection component may be reflected and the viewing angle may be narrowed. Therefore, an uneven structure is formed on the surface of the reflecting plate (Patent No. 27).
No. 5620) is preferably introduced. When the surface of the reflection plate is flat (instead of introducing an uneven structure on the surface), a light diffusion film may be attached to one side (cell side or outside) of the polarizing film.

The liquid crystal cell is a TN (twisted nematic)
Type, STN (Supper Twisted Nematic) type or HAN
(Hybrid Aligned Nematic) type is preferred.
The twist angle of the TN type liquid crystal cell is preferably from 40 to 100 °, more preferably from 50 to 90 °, and most preferably from 60 to 80 °.
The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 0.5 μm, and 0.2 to 0.4 μm. It is more preferred that there be. The twist angle of the STN type liquid crystal cell is 180
To 360 °, preferably 220 to 270 °
゜ is more preferable. The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.3 to 1.2 μm.
More preferably, it is 5 to 1.0 μm. HAN
In the type liquid crystal cell, the liquid crystal is substantially vertically aligned on one substrate and the pretilt angle on the other substrate is 0 to 4
It is preferably 5 °. The refractive index anisotropy of the liquid crystal layer (Δ
The value of the product (Δnd) of (n) and the thickness (d) of the liquid crystal layer is
The thickness is preferably from 0.1 to 1.0 μm, and more preferably from 0.3 to 0.8 μm. The substrate on which the liquid crystal is vertically aligned may be a substrate on the reflection plate side or a substrate on the transparent electrode side. The reflection type liquid crystal display device can be used in a normally white mode in which the display is bright when the applied voltage is low and a dark display when the applied voltage is high, or in a normally black mode in which the display is dark when the applied voltage is low and bright when the applied voltage is high. . Normally white mode is preferred.

[Guest-host reflective liquid crystal display device] FIG.
FIG. 1 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display element. The guest-host reflection type liquid crystal display device shown in FIG. 2 includes a lower substrate (11), an organic interlayer insulating film (1).
2), metal reflector (13), λ / 4 plate (14), lower transparent electrode (15), lower alignment film (16), liquid crystal layer (17), upper alignment film (18), upper transparent electrode (19) ), Light diffusion plate (2
0), an upper substrate (21) and an antireflection layer (22) are laminated in this order. The lower substrate (11) and the upper substrate (21) are made of a glass plate or a plastic film. Lower substrate (11) and organic interlayer insulating film (12)
A TFT (23) is attached between the two. The liquid crystal layer (17) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (24). Instead of providing the light diffusion plate (20), the metal reflection plate (13) may have a light diffusion function by making the surface of the metal reflection plate (13) uneven. The antireflection layer (22) preferably has an antiglare function in addition to the antireflection function.

FIG. 3 is a schematic sectional view showing another typical embodiment of the guest-host reflection type liquid crystal display device. The guest-host reflection type liquid crystal display device shown in FIG.
1), organic interlayer insulating film (32), cholesteric color reflector (33), λ / 4 plate (34), lower transparent electrode (3)
5) A structure in which a lower alignment film (36), a liquid crystal layer (37), an upper alignment film (38), an upper transparent electrode (39), an upper substrate (41), and an antireflection layer (42) are laminated in this order. Having. The lower substrate (31) and the upper substrate (41) are made of a glass plate or a plastic film. Lower substrate (31)
A TFT (43) is provided between the TFT and the organic interlayer insulating film (32).
Is attached. The λ / 4 plate (34) may also function as a light diffusion plate. The liquid crystal layer (37) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (44). A black matrix (45) is attached between the upper transparent electrode (39) and the upper substrate (41). Anti-reflection layer (4
2) preferably has an antiglare function in addition to the antireflection function.

The λ / 4 plate according to the present invention includes the λ / 4 plate (8) of the reflection type liquid crystal display device described with reference to FIG. 1, and FIG.
And it can be used as the λ / 4 plates (24) and (34) of the guest-host reflection type liquid crystal display device described in FIG.
Japanese Patent Application Laid-Open Nos. 6-222350 and 8-36174 disclose a guest-host reflection type liquid crystal display device having a λ / 4 plate.
No., No. 10-268300, No. 10-292175
No. 10-293301, No. 10-319776
Nos. 10-319442 and 10-325595
And JP-A-10-333138 and JP-A-11-38410. The λ / 4 plate according to the present invention can also be used for the guest-host reflection type liquid crystal display device described in each of the above publications.

[0056]

[Example 1] (Preparation of retardation plate) Average acetylation degree of 57.5 at room temperature
% Of cellulose acetate, 9.36 parts by mass of triphenyl phosphate, 4.68 parts by mass of biphenyldiphenyl phosphate, 3.00 parts by mass of a retardation increasing agent described below, 2.00 parts by mass of tribenzylamine, and methylene chloride 543 .14 parts by mass, 99.35 parts by mass of methanol and 19.87 parts by mass of n-butanol were mixed to prepare a solution (dope).

[0057]

Embedded image

The obtained dope was cast on a film forming band, 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 mass. The cellulose acetate film was peeled off from the band,
After drying for 0 minutes, the film was stretched at 130 ° C. in a direction parallel to the casting direction. The direction perpendicular to the stretching direction was allowed to shrink freely. After stretching, the film was dried at 120 ° C. for 30 minutes, and then the stretched film was taken out. The residual solvent amount after stretching was 0.1% by mass. The thickness of the obtained polymer film (retardation film) was 54 μm, and was measured using an ellipsometer (M-150, manufactured by JASCO Corporation).
When the retardation values (Re) at wavelengths of 450 nm, 550 nm and 590 nm were measured, they were 118.3 nm, 137.2 nm and 140.7 nm, respectively.
nm. Therefore, this cellulose acetate film achieved λ / 4 in a wide wavelength range. Thus, a λ / 4 plate was obtained. 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 1.58.

Example 2 (Preparation of Retardation Plate) The dope obtained in Example 1 was cast using a band casting machine. A film having a residual solvent content of 15% by mass was placed on a 45 ° C.
% To give a polymer film. The thickness of the obtained polymer film (retardation film) was 40 μm, and was measured using an ellipsometer (M-15).
0, manufactured by JASCO Corporation, wavelength 450 nm, 5
When the retardation values (Re) at 50 nm and 590 nm were measured, each was 118.3 n.
m, 137.2 nm and 140.7 nm. Therefore, this cellulose acetate film achieved λ / 4 in a wide wavelength range. Thus, a λ / 4 plate was obtained. Furthermore, the refractive index measurement by Abbe refractometer,
From the measurement of the angle dependence of the retardation, the wavelength was 550.
The refractive index nx in the direction of the in-plane slow axis, the refractive index ny in the direction perpendicular to the slow axis in the plane, and the refractive index nz in the thickness direction at nm are obtained, and (nx-nz) / (nx-ny) is obtained. The value was calculated to be 1.70.

Example 3 (Preparation of Retardation Plate) At room temperature, average acetylation degree was 59.0.
% Of cellulose acetate, 2.0 parts by mass of the retardation increasing agent used in Example 1, 9.36 parts by mass of triphenyl phosphate, 4.68 parts by mass of biphenyl diphenyl phosphate, methylene chloride 54
3.14 parts by weight, 99.35 parts by weight of methanol and n
A solution (dope) was prepared by mixing 19.87 parts by mass of butanol. The obtained dope was cast on a film forming band, 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 mass. The cellulose acetate film was peeled off from the band,
For 5 minutes, and then stretched at 130 ° C. in the casting direction and the 45 ° direction. After stretching and drying at 130 ° C for 20 minutes,
The stretched film was taken out. The residual amount of the solvent after stretching is 0.1.
It was 1% by mass. The thickness of the obtained polymer film (retardation plate) was 63 μm, and the thickness of the ellipsometer (M
-150, manufactured by JASCO Corporation, at a wavelength of 450 n.
The retardation values (Re) at 550 nm, 550 nm and 590 nm were measured.
7 nm, 137.4 nm and 141.1 nm. Therefore, this cellulose acetate film achieved λ / 4 in a wide wavelength range. Thus, λ
/ 4 plate was obtained. 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. When ny and the refractive index nz in the thickness direction were obtained, and the value of (nx-nz) / (nx-ny) was calculated, it was 1.50.

Example 4 (Production of Circular Polarizing Plate) The cellulose acetate film produced in Example 1 and a commercially available polarizing plate (manufactured by Sanritz Co., Ltd.)
Were arranged such that the slow axis of the cellulose acetate film and the transmission axis of the polarizing plate were at 45 degrees, and were adhered with an adhesive to produce a circularly polarizing plate. 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 nm), almost perfect circularly polarized light was achieved.

Example 5 (Preparation of Polarizing Film) The average degree of polymerization was 4000 and the degree of saponification was 99.
8 mol% of PVA was dissolved in water to obtain a 4.0% aqueous solution. This solution was cast in a band, dried, peeled off from the band, stretched dry in the casting direction, and then washed with iodine 0.1%.
5 g / l, 50 g / l potassium iodide aqueous solution (liquid temperature 3
(0 ° C.) for 1 minute. Then 100 g / l boric acid,
5% aqueous solution of potassium iodide (liquid temperature 70 ° C)
The substrate was immersed for 10 minutes, and further washed with a water washing layer (water temperature 20 ° C.) for 10 seconds. The washed film was further dried at 80 ° C. for 5 minutes to obtain a long polarizing film. The film width is 1290mm,
The thickness was 20 μm. (Production of Circular Polarizing Plate) The cellulose acetate film produced in Example 3, the produced polarizing film, and a commercially available cellulose acetate film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) were laminated in this order by a roll-to-roll method. A polarizing plate was obtained. 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 nm).
, Almost perfect circularly polarized light was achieved.

Example 6 (Preparation of TN-type reflective liquid crystal display device) A glass substrate provided with an ITO transparent electrode and a glass substrate provided with an aluminum reflective electrode having fine irregularities were prepared. On the electrode side of the two glass substrates, a polyimide alignment film (S
E-7992 (manufactured by Nissan Chemical Co., Ltd.) and rubbed. Two substrates were stacked via a 3.4 μm spacer so that the alignment films faced each other. The directions of the substrates were adjusted so that the rubbing directions of the two alignment films intersect at an angle of 110 °. Liquid crystal (ML)
C-6252, manufactured by Merck & Co., Ltd.) to form a liquid crystal layer. Thus, a TN type liquid crystal cell having a twist angle of 70 ° and a value of Δnd of 269 nm was produced. The λ prepared in Example 1 was placed on the side of the glass substrate on which the ITO transparent electrode was provided.
A / 4 plate was attached via an adhesive. On top of that, a polarizing plate (a polarizing film on which a protective film whose surface was subjected to AR treatment was laminated) was further adhered. In the reflection type liquid crystal display device,
A rectangular wave voltage of kHz was applied. Visual evaluation was performed with a white display of 1.5 V and a black display of 4.5 V. As a result, it was confirmed that neither white display nor black display had a hue and neutral gray was displayed. Next, when the contrast ratio of the reflection luminance was measured using a measuring device (EZcontrast160D, manufactured by Eldim), the contrast ratio from the front was 25, and the viewing angle at which the contrast ratio was 3 was 120 ° or more in the vertical direction and the horizontal direction. It was 120 ° or more. In addition, no problem occurred on the display in a durability test at a temperature of 60 ° C. and a relative humidity of 90% for 500 hours.

Example 7 (Production of STN-type reflective liquid crystal display device) A glass plate provided with an ITO transparent electrode and a glass substrate provided with a flat aluminum reflective electrode were prepared. A polyimide alignment film (SE-150, manufactured by Nissan Chemical Industries, Ltd.) was formed on each of the electrode sides of the two glass substrates, and rubbing treatment was performed. 6.
Two substrates were stacked via a 0 μm spacer such that the alignment films faced each other. The rubbing direction of the two alignment films is 6
The direction of the substrate was adjusted so as to intersect at an angle of 0 °.
Liquid crystal (ZLI-2977, manufactured by Merck) in the gap between the substrates
Was injected to form a liquid crystal layer. Thus, an STN type liquid crystal cell having a twist angle of 240 ° and a value of Δnd of 791 nm was produced. On the side of the glass substrate provided with the ITO transparent electrode, an internal diffusion sheet (IDS, manufactured by Dai Nippon Printing Co., Ltd.)
And the circularly polarizing plate produced in Example 5 were adhered in this order via an adhesive so that the polarizing plate became the outermost layer. A rectangular wave voltage of 55 Hz was applied to the manufactured reflective liquid crystal display device. Visual evaluation was performed with a black display of 2.0 V and a white display of 2.5 V. As a result, it was confirmed that neither white display nor black display had a hue and neutral gray was displayed. Next, a measuring instrument (EZcontrast
160D, manufactured by Eldim), the contrast ratio of the reflected luminance was measured.
The viewing angle at which the contrast ratio is 3 is 90
゜, left and right 105 °.

Example 8 (Preparation of HAN type reflective liquid crystal display device) A glass substrate provided with an ITO transparent electrode and a glass substrate provided with a flat aluminum reflective electrode were prepared. A polyimide alignment film (SE-6) was formed on the electrode side of the glass substrate provided with the ITO transparent electrode.
10, manufactured by Nissan Chemical Industries, Ltd.) and rubbed. A vertical alignment film (SE-1211, manufactured by Nissan Chemical Industries, Ltd.) on the electrode side of a glass substrate provided with an aluminum reflective electrode
Was formed. No rubbing treatment was performed on the alignment film on the aluminum reflective electrode. Two substrates were stacked via a 4.0 μm spacer such that the alignment films faced each other. Liquid crystal (ZLI-1565, manufactured by Merck) was injected into the gap between the substrates to form a liquid crystal layer. Thus, a HAN type liquid crystal cell having a value of Δnd of 519 nm was produced. The λ prepared in Example 1 was placed on the side of the glass substrate on which the ITO transparent electrode was provided.
A / 4 plate was attached via an adhesive. A polarizing plate (NPF-G1225DU, manufactured by Nitto Denko Corporation) was adhered thereon, and a light diffusion film (Lumisty, manufactured by Sumitomo Chemical Co., Ltd.) was further adhered thereon. A rectangular wave voltage of 55 Hz was applied to the manufactured reflective liquid crystal display device. Black display 0.8V,
Visual evaluation was performed with white display being 2.0 V, and it was confirmed that neutral gray was displayed without coloration in both white display and black display. Next, when the contrast ratio of the reflection luminance was measured using a measuring instrument (EZcontrast160D, manufactured by Eldim), the contrast ratio from the front was 8, and the viewing angle at which the contrast ratio was 3 was 120 ° or more in the vertical direction and 120 ° in the left and right directions. It was more than ゜.

Example 9 (Preparation of G / H type liquid crystal display element) On a glass substrate provided with an ITO transparent electrode, a polymer for forming a vertical alignment film (L
A solution of Q-1800 (manufactured by Hitachi Chemical DuPont Microsystems) was applied, dried, and then rubbed.
The λ / 4 plate produced in Example 2 was adhered on a glass substrate on which aluminum was vapor-deposited as a reflection plate with an adhesive. An SIO layer was provided on the λ / 4 plate by sputtering, and an ITO transparent electrode was provided thereon. A solution of a polymer for forming a vertical alignment film (LQ-1800, manufactured by Hitachi Chemical DuPont Microsystems) is applied on the transparent electrode,
After drying, a rubbing treatment was performed in a direction at 45 ° from the slow axis direction of the λ / 4 plate. Via a 7.6 μm spacer,
Two glass substrates were stacked so that the alignment films faced each other. The orientation of the substrate was adjusted so that the rubbing direction of the alignment film was antiparallel. A dichroic dye (NKX
A mixture of -1366, 2.0 mass% of Nippon Kogaku Dye Co., Ltd.) and 98.0 mass% of liquid crystal (ZLI-2806, manufactured by Merck) was injected by a vacuum injection method to form a liquid crystal layer. The fabricated guest-host reflective liquid crystal display device ITO
A 1 kHz rectangular wave voltage was applied between the electrodes. White display 1
V and the transmittance at 10 V for black display are 65% and 6%, respectively.
Met. The transmittance ratio (contrast ratio) between white display and black display was 11: 1. When the viewing angle at which a contrast ratio of 2: 1 was obtained in the upper, lower, left and right directions was measured, it was 120 ° or more in both the upper, lower, left and right directions. The transmittance was measured while increasing and decreasing the voltage, but no hysteresis was observed in the transmittance-voltage curve.

Comparative Example 1 (Preparation of λ / 4 Plate) A polycarbonate having a mass average molecular weight of 100,000 was dissolved in methylene chloride to obtain a polycarbonate solution having a concentration of 17% by mass. Put this solution on a glass plate
The film was cast to a dry film thickness of 80 μm, dried at room temperature for 30 minutes, and then dried at 70 ° C. for 30 minutes. Peel the polycarbonate film (volatile content: about 1% by mass) from the glass plate,
It was cut into a size of 5 cm × 10 cm. The film was uniaxially stretched at 158 ° C. to obtain a stretched birefringent film of polycarbonate. The obtained polycarbonate film (λ / 4 plate) was measured for retardation values (Re) at wavelengths of 450 nm, 550 nm and 590 nm using an ellipsometer (M-150, manufactured by JASCO Corporation). , 147.8 nm, 137.5
nm and 134.9 nm.

(Preparation of λ / 2 Plate) Using the polycarbonate solution used in preparing the λ / 4 plate, the dry film thickness was 100 μm.
A λ / 2 plate was produced in the same manner as in the production of λ / 4 except that the film was cast so as to obtain m. About the obtained polycarbonate film (λ / 2 plate), an ellipsometer (M-
150, manufactured by JASCO Corporation) at a wavelength of 450 n.
m, 550 nm and 590 nm, the retardation values (Re) were measured.
0 nm, 275.0 nm and 269.8 nm.

(Preparation of TN Reflection Type Liquid Crystal Display Device) The TN type liquid crystal cell prepared in Example 6 was provided with a λ / 4 plate, a λ / 2 plate, and a polarizing plate on the glass substrate side provided with the ITO transparent electrode. Polarizing film with a protective film laminated on the surface with AR treatment)
In this order, they were attached via an adhesive. The angle between the transmission axis of the polarizing film and the slow axis of the λ / 2 plate is 20 °, and the angle between the slow axis of the λ / 2 plate and the slow axis of the λ / 4 plate is 55 °. . A 1 kHz rectangular wave voltage was applied to the manufactured reflective liquid crystal display device. 1.5 V for white display, 4.5 V for black display
As a result, a slight yellow tint was observed in white display, and a slight blue tint was observed in black display. Next, when the contrast ratio of the reflection luminance was measured using a measuring device (EZcontrast160D, manufactured by Eldim), the contrast ratio from the front was 10, and the contrast ratio was 3
Was 100 ° vertically and 80 ° horizontally.
When a durability test was conducted at a temperature of 60 ° C. and a relative humidity of 90% for 500 hours, light leakage (frame-shaped display unevenness) occurred around the display.

Example 10 A cellulose acetate film was prepared in the same manner as in Example 1, except that the amount of the retardation increasing agent was 6.00 parts by mass and the thickness of the obtained film was 65 μm. Produced. About the obtained cellulose acetate film (retardation film), an ellipsometer (M-150, JASCO Corporation)
Wavelengths of 450 nm, 550 nm and 59
When the retardation values (Re) at 0 nm were measured, they were 236.6 nm, 274.4 nm and 281.4 nm, respectively. Therefore, this cellulose acetate film achieved λ / 2 in a wide wavelength range.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.

FIG. 2 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display element.

FIG. 3 is a schematic cross-sectional view showing another typical embodiment of a guest-host reflection type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 lower substrate 2 reflective electrode 3 lower alignment film 4 liquid crystal layer 5 upper alignment film 6 transparent electrode 7 upper substrate 8 λ / 4 plate 9 polarizing film 11 lower substrate 12 organic interlayer insulating film 13 metal reflector 14 λ / 4 plate 15 lower Transparent electrode 16 Lower alignment film 17 Liquid crystal layer 18 Upper alignment film 19 Upper transparent electrode 20 Light diffusing plate 21 Upper substrate 22 Antireflection layer 23 TFT 24 Spacer 31 Lower substrate 32 Organic interlayer insulating film 33 Cholesteric color reflector 34 λ / 4 plate 35 lower transparent electrode 36 lower alignment film 37 liquid crystal layer 38 upper alignment film 39 upper transparent electrode 41 upper substrate 42 antireflection layer 44 spacer 45 black matrix

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13363 G02F 1/13363 F-term (Reference) 2H049 BA03 BA06 BA07 BA25 BB03 BB12 BB42 BB49 BB51 BC03 BC22 2H091 FA08X FA08Z FA11X FA14Z FA37X FB02 FB12 FD10 GA06 GA07 GA08 GA13 KA10 LA18 LA20 4F071 AA09 AC01 AH12 BB07 BC01 BC12 4J002 AB021 EA066 EL096 EP016 ET016 EU026 EU056 EU116 EU176 GQ05

Claims (11)

[Claims] 1. A retardation value (Re450) measured at a wavelength of 450 nm is in the range of 100 to 125 nm, a retardation value (Re590) measured at a wavelength of 590 nm is in a range of 120 to 160 nm,
A retardation plate comprising a single polymer film satisfying a relationship of Re590-Re450 ≧ 2 nm and having a thickness in a range of 10 to 70 μm. 2. A retardation value (Re450) measured at a wavelength of 450 nm is in the range of 108 to 120 nm, a retardation value (Re550) measured at a wavelength of 550 nm is in a range of 125 to 142 nm,
The retardation value (Re5) measured at a wavelength of 590 nm
90) is in the range of 130 to 152 nm;
A retardation plate comprising a single polymer film satisfying a relationship of 0-Re550 ≧ 2 nm and having a thickness in a range of 10 to 70 μm. 3. The retardation plate according to claim 1, wherein the polymer film is a cellulose acetate film. 4. The cellulose acetate film comprises a cellulose acetate having an acetylation degree of 57.0 to 61.5%, and an aromatic compound having at least two aromatic rings, based on 100 parts by mass of cellulose acetate. The retardation plate according to claim 3, wherein the retardation plate contains 0.01 to 20 parts by mass. 5. The retardation plate according to claim 1, wherein the polymer film is a stretched cellulose acetate film. 6. A circle in which a retardation plate and a linear polarizing film are laminated such that the angle between the slow axis in the plane of the retardation plate and the transmission axis of the linear polarizing film is substantially 45 °. A polarizing plate,
The retardation plate has a retardation value (Re450) measured at a wavelength of 450 nm in the range of 100 to 125 nm, and a retardation value (R450) measured at a wavelength of 590 nm.
e590) is in the range of 120 to 160 nm, and Re
590-Re450 ≧ 2 nm, and
A circularly polarizing plate comprising a single polymer film having a thickness in the range of 10 to 70 μm. 7. A retardation value (Re450) measured at a wavelength of 450 nm is in a range of 200 to 250 nm, a retardation value (Re590) measured at a wavelength of 590 nm is in a range of 240 to 320 nm,
A retardation plate which satisfies the relationship of Re590-Re450 ≧ 4 nm and is made of one polymer film having a thickness in the range of 10 to 70 μm. 8. A retardation value (Re450) measured at a wavelength of 450 nm is in a range of 216 to 240 nm, a retardation value (Re550) measured at a wavelength of 550 nm is in a range of 250 to 284 nm,
The retardation value (Re5) measured at a wavelength of 590 nm
90) is in the range of 260 to 304 nm;
A retardation plate comprising a single polymer film satisfying a relationship of 0-Re550 ≧ 4 nm and having a thickness in a range of 10 to 70 μm. 9. The retardation plate according to claim 7, wherein the polymer film is a cellulose acetate film. 10. The cellulose acetate film comprises a cellulose acetate having an acetylation degree of 57.0 to 61.5% and an aromatic compound having at least two aromatic rings based on 100 parts by mass of the cellulose acetate. The phase difference plate according to claim 9, comprising 0.01 to 20 parts by mass. 11. The retardation plate according to claim 7, wherein the polymer film is a stretched cellulose acetate film.