JP2000284123A - Elliptic polarizing plate and tn liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an integrated elliptic polarizing plate suitable to the TN liquid crystal display device by allowing a transparent base to have a wave length dispersed value of specific refractive index anisotropy. SOLUTION: The TN type liquid crystal display device has layer structure of a lower elliptic polarizing plate, a TN liquid crystal cell, and an upper elliptic polarizing plate laminated in order from a back light side. The integrated elliptic polarizing plate is formed by laminating a transparent protection film 11, a polarizing film 12, a transparent base 13, and an optical anisotropic layer 14 in this order. This transparent base 13 is adjusted in wavelength dispersed value of refractive index anisotropy, defined by α=Δn(450)/Δn(600), to 0.7 to 1.3. Here, α is the wavelength dispersed value of the refractive index anisotropy of the transparent base 13, Δn(450) is the refractive index anisotropy of the transparent base 13 which is measured with light of 450 nm in wavelength, and Δn(600) is the refractive index anisotropy of the transparent base 13 measured with light of 600 nm in wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transparent protective film, a polarizing film,
The present invention relates to an elliptically polarizing plate and a TN type liquid crystal display in which a transparent support and an optically anisotropic layer formed of liquid crystal molecules are laminated in this order.

[0002]

2. Description of the Related Art A TN (Twisted Nematic) type liquid crystal display device includes a TFT (Thin Film Transistor) and an MIM (Meta
l is the most widely used liquid crystal display device in combination with an active element such as an Insulator Metal. TN
The liquid crystal display device includes a TN liquid crystal cell and two polarizing elements. The liquid crystal cell is composed of rod-like liquid crystal molecules, two substrates for enclosing the same, and an electrode layer for applying a voltage to the rod-like liquid crystal molecules. In a TN type liquid crystal cell, 90
An alignment film for aligning rod-like liquid crystalline molecules with a twist angle of ゜ is provided on two substrates. In order to improve the viewing angle of a TN liquid crystal display device, an optical compensation sheet (retardation plate) is generally provided between a liquid crystal cell and a polarizing element. The laminate of the polarizing element (polarizing film) and the optical compensation sheet functions as an elliptically polarizing plate. As the optical compensation sheet, a stretched birefringent film has been conventionally used.

It has been proposed to use an optical compensatory sheet having an optically anisotropic layer containing liquid crystal molecules on a transparent support instead of an optical compensatory sheet made of a stretched birefringent film. The optically anisotropic layer aligns liquid crystalline molecules,
It is formed by fixing the orientation state. Liquid crystal molecules, especially discotic liquid crystal molecules, generally have a large birefringence. The liquid crystal molecules have various alignment forms. The use of liquid crystal molecules makes it possible to produce an optical compensatory sheet having optical properties that cannot be obtained with a conventional stretched birefringent film. An optical compensatory sheet using discotic liquid crystal molecules is disclosed in JP-A-6-214116, US Pat.
Nos. 3679 and 5646703, German Patent Publication 39
It is described in each specification of 11620A1. These optical compensation sheets are designed assuming a TN type liquid crystal display device as a main use.

[0004]

When a laminate of an optical compensatory sheet using liquid crystal molecules and a polarizing element (polarizing film) is used as an elliptically polarizing plate, the transparent support of the optical compensatory sheet is connected to one side of the polarizing element. Can function as a protective film. Such an elliptically polarizing plate includes a transparent protective film, a polarizing film,
It has a layer structure in the order of a transparent support, and an optically anisotropic layer formed from liquid crystal molecules. The liquid crystal display device is characterized in that it is thin and lightweight, and if one of the constituent elements is reduced by dual use, the device can be made thinner and lighter.
Further, if one component of the liquid crystal display device is reduced, one component bonding step is also reduced, and the possibility of occurrence of a failure when manufacturing the device is reduced.

However, the optical properties required for the transparent support of the optical compensation sheet often differ from the optical properties required for the protective film of the polarizing element. for that reason,
An integrated elliptically polarizing plate in which the transparent support of the optical compensation sheet and one protective film of the polarizing element are shared has been proposed in the past (for example, JP-A-7-191217 and JP-A-8-191217).
21996), but there are few examples in which it is actually used.

In order to put into practical use an integrated elliptically polarizing plate in which the transparent support of the optical compensatory sheet and the protective film of one of the polarizing elements are shared, the optical properties required for the transparent support of the optical compensatory sheet are required. And the optical properties required for the protective film of the polarizing element must be satisfied without contradiction.
An object of the present invention is to provide an integrated elliptically polarizing plate particularly suitable for a TN type liquid crystal display device. Another object of the present invention is to provide a TN type liquid crystal display device which is easy to manufacture and is lighter and thinner than the conventional one.

[0007]

An object of the present invention is to provide an optical compensatory sheet of the following (1) to (6) and a T (7) of the following (7).
This was achieved by an N-type liquid crystal display device. (1) An elliptically polarizing plate in which a transparent protective film, a polarizing film, a transparent support, and an optically anisotropic layer formed of liquid crystal molecules are laminated in this order, wherein the transparent support has 0.7 to 1 .
An elliptically polarizing plate having a wavelength dispersion of refractive index anisotropy defined by the following formula within a range of less than 3. α = Δn (450) / Δn (600) where α is the wavelength dispersion value of the refractive index anisotropy of the transparent support; Δn (450) is the refractive index of the transparent support measured with light having a wavelength of 450 nm. Anisotropic; and Δn (60
0) is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm. (2) The laminate of the transparent support and the optically anisotropic layer,
The elliptically polarizing plate according to (1), which has a Re retardation value defined by the following formula in the range of 0 to 100 nm and an Rth retardation value defined by the following formula in the range of 20 to 400 nm. . Re = │nx-ny│ × d Rth = {(n1 + n2) / 2−n3} × d where nx and ny are the in-plane principal refractive indexes of the laminate; d is the thickness of the laminate (nm) ); And n1,
n2 and n3 are the triaxial refractive indexes of the laminate satisfying n1 ≧ n2 ≧ n3. (3) The slow axis of the laminate of the transparent support and the optically anisotropic layer is substantially parallel to the transmission axis of the polarizing film.
The elliptically polarizing plate according to 1. (4) The elliptically polarizing plate according to (1), wherein the liquid crystal molecules are discotic liquid crystal molecules. (5) The elliptically polarizing plate according to (1), wherein the liquid crystalline molecules are fixed in a state of being oriented by polymerization. (6) The elliptically polarizing plate according to (1), wherein the transparent support is a cellulose ester film.

(7) A TN type liquid crystal cell and two polarizing elements disposed on both sides of the TN type liquid crystal cell, and at least one of the polarizing elements has a transparent protective film, a polarizing film, a transparent support and a liquid crystal molecule in order from the outside. A TN type liquid crystal display device which is an elliptically polarizing plate on which an optically anisotropic layer formed from is laminated, wherein the transparent support is defined by the following formula within a range of 0.7 or more and less than 1.3. TN liquid crystal display device having a wavelength dispersion value of refractive index anisotropy. α = Δn (450) / Δn (600) where α is the wavelength dispersion value of the refractive index anisotropy of the transparent support; Δn (450) is the refractive index of the transparent support measured with light having a wavelength of 450 nm. Anisotropic; and Δn (60
0) is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm. In the present specification, the slow axis means a direction in which the refractive index becomes maximum in the plane. Further, the transmission axis means a direction in which the transmittance becomes maximum in the plane. Further, in this specification, “substantially parallel” means that an error from exact parallel is less than ± 10 °. The error is preferably less than ± 8 °, more preferably less than ± 4 °, even more preferably less than ± 2 °, and most preferably less than ± 1 °.

[0009]

As a result of research, the present inventor has found that by adjusting the wavelength dispersion of the refractive index anisotropy of the transparent support within the range of 0.7 or more and less than 1.3, the transparency of the optical compensation sheet can be improved. It has been found that the optical properties required for the support and the optical properties required for the protective film of the polarizing element can be satisfied without contradiction. By using the transparent support having the above wavelength dispersion value, an integrated elliptically polarizing plate having excellent optical properties can be obtained. This integrated elliptically polarizing plate is particularly effective when used in a TN liquid crystal display device. By using the integrated elliptically polarizing plate, a TN-type liquid crystal display device which is easy to manufacture, lighter and thinner than the conventional one can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a TN type liquid crystal display using an integrated elliptically polarizing plate. The TN type liquid crystal display device has a layer configuration in which a lower elliptically polarizing plate (1), a TN liquid crystal cell (2), and an upper elliptically polarizing plate (3) are stacked in this order from the backlight (BL) side. Solid arrows (TA1, TA) written on the lower elliptically polarizing plate (1) and the upper elliptically polarizing plate (3)
3) is the transmission axis of the polarizing film in the elliptically polarizing plate. Wavy arrows (SA1, SA3) drawn on the lower elliptically polarizing plate (1) and the upper elliptically polarizing plate (3) indicate the slow axis of the laminate of the transparent support and the optically anisotropic layer in the elliptically polarizing plate. It is. T
Arrows (RD1, RD2) written on N liquid crystal cell (2)
Is the rubbing direction of the two alignment films provided in the liquid crystal cell. As shown in FIG. 1, the slow axis of the laminate of the transparent support and the optically anisotropic layer is preferably substantially parallel to the transmission axis of the polarizing film.

FIG. 2 is a schematic view of an integrated elliptically polarizing plate. As shown in FIG. 2, the integrated elliptically polarizing plate has a transparent protective film (11), a polarizing film (12), a transparent support (13), and an optically anisotropic layer (14) laminated in this order. Having a configuration. Hereinafter, each component of the integrated elliptically polarizing plate will be described in this order.

[Transparent protective film] As the transparent protective film, an optically isotropic polymer film is used. That the protective film is transparent means that the light transmittance is 80% or more. Specifically, the optical isotropy means that the in-plane retardation (Re) is preferably 10 nm or less,
More preferably, it is 5 nm or less. Further, the retardation (Rth) in the thickness direction is preferably at most 40 nm, more preferably at most 20 nm. The definition of the in-plane retardation (Re) and the retardation in the thickness direction (Rth) will be described later for the transparent support. As the transparent protective film, a cellulose ester film, preferably a triacetyl cellulose film, is generally used. The cellulose ester film is preferably formed by a solvent casting method. The thickness of the transparent protective film is preferably from 20 to 500 μm, more preferably from 50 to 200 μm.

[Polarizing Film] Iodine-based polarizing films,
There are 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 (polarization axis) of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film.

[Transparent support] The thickness of the transparent support is 20
To 500 μm, preferably 50 to 200 μm.
More preferably, it is μm. In the present invention, for the transparent support, the wavelength dispersion value of the refractive index anisotropy defined by the following formula is adjusted within the range of 0.7 or more and less than 1.3. α = Δn (450) / Δn (600) where α is the wavelength dispersion value of the refractive index anisotropy of the transparent support; Δn (450) is the refractive index of the transparent support measured with light having a wavelength of 450 nm. Anisotropic; and Δn (60
0) is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm.

The laminate of the transparent support and the optically anisotropic layer (described later) has a Re retardation value defined by the following formula within the range of 0 to 100 nm, and
It preferably has an Rth retardation value defined by the following formula in the range of 0 to 400 nm. Re = │nx-ny│ × d Rth = {(n1 + n2) / 2−n3} × d where nx and ny are the in-plane principal refractive indexes of the laminate; d is the thickness of the laminate (nm) ); And n1,
n2 and n3 are the triaxial refractive indexes of the laminate satisfying n1 ≧ n2 ≧ n3.

Further, when the wavelength of the transparent support is 600 nm,
Retardation value in the thickness direction is 20 to 400
nm, preferably 50 to 300 nm
More preferably, it is 60 to 200 nm.
Is most preferred. The birefringence in the thickness direction ｛(nx +
ny) / 2−nz} is 7 × 10^-Four~ 4 × 10^-3In
Preferably 1 × 10^-3~ 4 × 10^-3Is
Is more preferable, and 1.5 × 10^-3~ 4 × 10^-3In
More preferably 2 × 10^-3~ 4 × 10^-3so
Still more preferably, 2 × 10^-3Or 3 × 1
0 ^-3Is most preferably 2 × 10^-3To 2.5
× 10^-3Is particularly preferred.

As the transparent support, a cellulose ester film having a high retardation is preferably used. In-plane retardation of cellulose ester film (R
e) can be adjusted (high value) by stretching the cellulose ester film. The retardation (Rth) in the thickness direction of the cellulose ester film is
It can be adjusted (to a high value) by (1) using a retardation increasing agent, (2) adjusting the average acetylation degree (acetylation degree), or (3) manufacturing a film by a cooling dissolution method. As a result, a cellulose ester film conventionally considered to be optically isotropic can be used as an optically anisotropic transparent support having an optical compensation function. Hereinafter, a method for producing a cellulose ester film having a high retardation will be described.

As the cellulose ester, a lower fatty acid ester of cellulose is preferably used. The lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms 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. The average acetylation degree (acetylation degree) of cellulose acetate is preferably 55.0% or more and less than 62.5%. From the viewpoint of physical properties of the film, the average acetylation degree is more preferably 58.0% or more and less than 62.5%. However, the average degree of acetylation is from 55.0% to less than 58.0% (preferably from 57.0% to 58.0%).
%), A film having a high retardation in the thickness direction can be produced.

The retardation in the thickness direction can be increased by using a retardation increasing agent. As the retardation increasing agent, a compound having at least two aromatic rings and having a molecular structure that does not sterically hinder the conformation of the two aromatic rings can be used. The retardation increasing agent is preferably used in an amount of 0.3 to 20 parts by weight based on 100 parts by weight of the cellulose ester. The compound having at least two aromatic rings has a π-bonding plane having 7 or more carbon atoms. Unless the configuration of the two aromatic rings is sterically hindered, the two aromatic rings form the same plane. According to the inventor's research,
In order to increase the retardation of the cellulose ester film, it is important that a plurality of aromatic rings form the same plane. 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).

The aromatic hetero ring is generally an unsaturated hetero ring. The aromatic hetero ring is preferably a 5-, 6-, or 7-membered ring, more preferably a 5- or 6-membered ring. Aromatic heterocycles are generally
It has 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, furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring,
Pyran ring, pyridine ring, pyridazine ring, pyrimidine ring,
It includes a pyrazine ring and a 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,
Preferred are an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring and a 1,3,5-triazine ring.

The number of aromatic rings contained in the retardation increasing agent is preferably from 2 to 20, preferably from 2 to 12.
Is more preferably, 2 to 8 is more preferable, and 2 to 6 is most preferable. When the compound has three or more aromatic rings, the configuration of at least two aromatic rings need not be sterically hindered. 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). In terms of the retardation increase function,
Any of (a) to (c) may be used. However, in the case of (b) or (c), it is necessary that the conformation of the two aromatic rings is not sterically hindered.

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. However, it is necessary that the substituent does not hinder the conformation of the two aromatic rings. For steric hindrance, the type and position of the substituents become a problem. As the type of the substituent, a sterically bulky substituent (for example, a tertiary alkyl group) is likely to cause steric hindrance. As the position of the substituent, steric hindrance is likely to occur when a position adjacent to the bond of the aromatic ring (ortho position in the case of a benzene ring) is substituted. Examples of the substituent include a halogen atom (F, Cl, B
r, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl,
Ureido, alkyl group, alkenyl group, alkynyl group,
Aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamide group, aliphatic substituted amino group, aliphatic substituted carbamoyl Groups, aliphatic substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic 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 enhancer is 30.
It is preferably from 0 to 800. The boiling point of the retardation increasing agent is preferably 260 ° C. or higher.
The boiling point can be measured using a commercially available measuring device (for example, TG / DTA10).
0, manufactured by Seiko Denshi Kogyo KK).

It is preferable to produce a cellulose ester film by a solvent casting method. In the solvent casting method, a film is produced using a solution (dope) in which a cellulose ester is dissolved in an organic solvent. The organic solvent is 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. It is preferable to include ether,
Ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, -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.

The solution may be prepared by a general method without employing the cooling dissolution 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 the cellulose ester is adjusted so that the obtained solution contains 10 to 40% by weight. More preferably, the amount of cellulose ester 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 the cellulose ester and the organic solvent at room temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heating conditions. Specifically, the cellulose ester and the organic solvent are put in a pressurized container, sealed, and 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 1 ° C.
10 ° 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.

A solution can be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose ester can be dissolved in an organic solvent (an organic solvent other than a halogenated hydrocarbon) which is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent (for example, halogenated hydrocarbon) which can dissolve the cellulose ester by the usual dissolution method, the cooling dissolution method has an effect that a uniform solution can be obtained quickly. When the cooling dissolution method is used, the retardation of the produced cellulose ester film becomes a high value. In the cooling dissolution method, first, a cellulose ester is gradually added to an organic solvent at room temperature while stirring. It is preferable to adjust the amount of the cellulose ester so that the mixture contains 10 to 40% by weight of the mixture.
More preferably, the amount of cellulose ester is from 10 to 30% by weight. 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 the cellulose ester and the organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and 12 ° C./min.
/ Min or more is most preferable. A higher cooling rate is preferred, but 10,000 ° C./sec is a theoretical upper limit, 1000 ° C./sec is a technical upper limit, and
0 ° C./sec is a practical upper limit. The cooling rate 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 temperature reaches the final cooling temperature.

Further, the temperature is raised to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C.,
When heated to the temperature of 0 to 50 ° C., the cellulose ester 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, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The heating rate is preferably as high as possible, but the theoretical upper limit is 10,000 ° C./sec.
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 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 ester solution (dope), a cellulose ester 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 2,367,603.
Nos. 2492078, 2492977, 24
No. 92978, No. 2607704, No. 2739069
Nos. 2739070, British Patent Nos. 640731 and 736892, Japanese Patent Publication No. 45-4554,
JP-A-49-5614, JP-A-60-176834, 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. 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. The solution (dope) prepared according to the present invention satisfies this condition. The thickness of the film to be produced is preferably 40 to 120 μm,
More preferably, it is 70 to 100 μm.

A plasticizer can be added to the cellulose ester film in order to improve 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.

The cellulose ester film may contain an antioxidant (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) or an ultraviolet inhibitor. Good. Regarding the deterioration inhibitor, see JP-A-Hei 3
-199201, 5-1907073, 5-1
No. 94789, No. 5-271471, No. 6-1078
No. 54 describes each of them. The addition amount of the deterioration inhibitor
It 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. If the amount exceeds 1% by weight, bleeding out (bleeding out) of the deterioration inhibitor on the film surface may be observed.
A particularly preferred example of the deterioration inhibitor is butylated hydroxytoluene (BHT). The UV inhibitors are described in JP-A-7-11056. Note that cellulose acetate having an average acetylation degree of 55.0 to 58.0% has an average acetylation degree of 58.0%.
As compared with the above-mentioned cellulose triacetate, there is a defect that the stability of the prepared solution and the physical properties of the produced film are inferior. However, this disadvantage can be substantially eliminated by using an antioxidant such as the above-mentioned deterioration inhibitor, particularly butylated hydroxytoluene (BHT).

[Alignment Film] The alignment film is formed by rubbing an organic compound (preferably a polymer), obliquely depositing an inorganic compound, forming a layer having microgrooves, or using an organic compound by the Langmuir-Blodgett method (LB film). (Eg, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate). In addition, the application of an electric field,
There is also known an alignment film in which an alignment function is generated by applying a magnetic field or irradiating light. An alignment film formed by rubbing a polymer is particularly preferable. The rubbing treatment is performed by rubbing the surface of the polymer layer several times with paper or cloth in a certain direction. The type of polymer used for the alignment film is determined according to the type of display mode of the liquid crystal cell. In a display mode in which many of the rod-like liquid crystal molecules in the liquid crystal cell are substantially vertically aligned (eg, VA, OCB, HAN), the liquid crystal molecules in the optically anisotropic layer are substantially horizontally aligned. An alignment film having the function of causing the alignment is used. In a display mode (eg, STN) in which most of the rod-like liquid crystal molecules in the liquid crystal cell are substantially horizontally aligned, the liquid crystal molecules have a function of substantially vertically aligning the liquid crystal molecules in the optically anisotropic layer. An alignment film is used.
In a display mode (eg, TN) in which many of the rod-like liquid crystal molecules in the liquid crystal cell are substantially obliquely oriented, it has a function of substantially obliquely aligning the liquid crystal molecules of the optically anisotropic layer. An alignment film is used.

With respect to specific types of polymers, there are descriptions in the literature on optical compensatory sheets using discotic liquid crystalline molecules corresponding to the various display modes described above. The strength of the alignment film may be enhanced by crosslinking the polymer used for the alignment film. By introducing a crosslinkable group into the polymer used for the alignment film and reacting the crosslinkable group,
The polymer can be crosslinked. The crosslinking of the polymer used for the alignment film is described in JP-A-8-3389.
No. 13 has a description. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm. After the liquid crystal molecules are aligned using the alignment film, the liquid crystal molecules are fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is formed on the support. It may be transferred. Discotic liquid crystalline molecules fixed in an aligned state can maintain the aligned state without an alignment film. Therefore, in the optical compensation sheet, the alignment film is not an essential element (although it is essential in the production of the optical compensation sheet containing discotic liquid crystalline molecules).

[Optical Anisotropic Layer] The optically anisotropic layer is formed from liquid crystal molecules. As the liquid crystal molecules, rod-shaped liquid crystal molecules or discotic liquid crystal molecules are preferable,
Discotic liquid crystalline molecules are particularly preferred. Examples of rod-like liquid crystal molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxane, tolan and alkenylcyclohexylbenzonitrile are preferably used. Not only low molecular liquid crystal molecules as described above but also high molecular liquid crystal molecules can be used. The high-molecular liquid crystal molecules are polymers having side chains corresponding to the low-molecular liquid crystal molecules described above. An optical compensatory sheet using high-molecular liquid crystalline molecules is described in JP-A-5-53016.

Discotic liquid crystalline molecules are described in various literatures (C. Destrade et al., Mol. Crysr. Liq. Cryst., V
ol. 71, page 111 (1981); edited by The Chemical Society of Japan, quarterly chemistry review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2
(1994); B. Kohne et al., Angew. Chem. Soc. Chem. C
omm., page 1794 (1985); J. Zhang et al., J. Am. Che
m. Soc., vol. 116, page 2655 (1994)). Regarding the polymerization of discotic liquid crystalline molecules,
It is described in JP-A-8-27284. In order to fix the discotic liquid crystal molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal molecules. However, when a polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain an oriented state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystal molecule is preferably a compound represented by the following formula (I).

(I) D (-LQ) _{n wherein} D is a discotic core; L is a divalent linking group; Q is a polymerizable group; and n is 4 to 12 Is an integer. An example of the discotic core (D) of the formula (I) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

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In the formula (I), the divalent linking group (L)
Is an alkylene group, alkenylene group, arylene group,-
It is preferably a divalent linking group selected from the group consisting of CO-, -NH-, -O-, -S- and a combination thereof. The divalent linking group (L) includes an alkylene group, an alkenylene group, an arylene group, -CO-, -NH-,-
More preferably, the group is a group obtained by combining at least two divalent groups selected from the group consisting of O- and -S-. The divalent linking group (L) is most preferably a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group, a halogen atom, a cyano, an alkoxy group, an acyloxy group). Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (P). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group.

L1: -AL-CO-O-AL- L2: -AL-CO-O-AL-O- L3: -AL-CO-O-AL-O-AL- L4: -AL-CO-O -AL-O-CO-L5: -CO-AR-O-AL-L6: -CO-AR-O-AL-O-L7: -CO-AR-O-AL-O-CO-L8: -CO -NH-AL-L9: -NH-AL-O-L10: -NH-AL-O-CO-L11: -O-AL-L12: -O-AL-O-

L13: -O-AL-O-CO- L14: -O-AL-O-CO-NH-AL- L15: -O-AL-S-AL- L16: -O-CO-AL-AR -O-AL-O-CO-L17: -O-CO-AR-O-AL-CO-L18: -O-CO-AR-O-AL-O-CO-L19: -O-CO-AR- O-AL-O-AL-OC
O-L20: -O-CO-AR-O-AL-O-AL-OA
L-O-CO-L21: -S-AL-L22: -S-AL-O-L23: -S-AL-O-CO-L24: -S-AL-S-AL-L25: -S-AR -AL-

In order to optically compensate for a liquid crystal cell in which rod-like liquid crystal molecules are twisted in the STN mode, it is preferable that the discotic liquid crystal molecules are also twisted. When an asymmetric carbon atom is introduced into the AL (alkylene group or alkenylene group), the discotic liquid crystal molecule can be twisted and aligned in a helical manner. Further, even when a compound (chiral agent) having an asymmetric carbon atom and exhibiting optical activity is added to the optically anisotropic layer, the discotic liquid crystal molecules can be twisted in a helical manner.

The polymerizable group (Q) in the formula (I) is determined according to the type of the polymerization reaction. Examples of the polymerizable group (Q) are shown below.

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The polymerizable group (Q) is an unsaturated polymerizable group (Q1
To Q7), an epoxy group (Q7) or an aziridinyl group (Q8), more preferably an unsaturated polymerizable group, and more preferably an ethylenically unsaturated polymerizable group (Q
1 to Q6) are most preferred. In the formula (I), n is an integer of 4 to 12. Specific numbers are determined according to the type of discotic core (D).
The combination of a plurality of L and Q may be different, but is preferably the same.

Two or more discotic liquid crystal molecules may be used in combination. For example, the polymerizable discotic liquid crystal molecules and the non-polymerizable discotic liquid crystal molecules described above can be used in combination. The non-polymerizable discotic liquid crystal molecule is preferably a compound in which the polymerizable group (P) of the polymerizable discotic liquid crystal molecule is changed to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystalline molecule is preferably a compound represented by the following formula (II). (II) D (-LR) _{n wherein} D is a discotic core; L is a divalent linking group; R is a hydrogen atom or an alkyl group;
Is an integer of 4 to 12. An example of the discotic core (D) of formula (II) is that LP (or PL) is replaced by LR (or R
Except for changing to L), it is the same as the example of the polymerizable discotic liquid crystal molecule described above. Further, a divalent linking group (L)
Is the same as the example of the polymerizable discotic liquid crystal molecule described above. The alkyl group represented by R has 1 to 4 carbon atoms.
It is preferably 0, more preferably 1 to 30. A chain alkyl group is more preferable than a cyclic alkyl group, and a straight-chain alkyl group is more preferable than a branched chain alkyl group. R is particularly preferably a hydrogen atom or a linear alkyl group having 1 to 30 carbon atoms.

The optically anisotropic layer is composed of liquid crystal molecules or the following polymerizable initiators and optional additives (eg, plasticizers, monomers, surfactants, cellulose esters, 1,3,5-
It is formed by applying a coating solution containing a triazine compound and a chiral agent) on the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethylsulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, ,
Chloroform, dichloromethane), ester (eg, methyl acetate, butyl acetate), ketone (eg, acetone, methyl ethyl ketone), ether (eg, tetrahydrofuran,
1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The application of the coating solution can be performed by a known method (eg, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method).

The liquid crystal molecules are preferably substantially uniformly oriented, more preferably fixed in a state of being substantially uniformly oriented, and the liquid crystal molecules are fixed by a polymerization reaction. Is most preferred. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reactions are preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670) and acyloin ethers (U.S. Pat.
828), α-hydrocarbon-substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512),
Polynuclear quinone compounds (U.S. Pat.
51758), a combination of a triarylimidazole dimer and p-aminophenyl ketone (described in US Pat. No. 3,549,367), an acridine and phenazine compound (Japanese Unexamined Patent Publication No. Sho 60-105667).
No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,221,970). The amount of the photopolymerization initiator used is preferably 0.01 to 20% by weight, more preferably 0.5 to 5% by weight of the solid content of the coating solution. Light irradiation for the polymerization of discotic liquid crystalline molecules preferably uses ultraviolet light. The irradiation energy is preferably from 20 mJ / cm ^{2 to} 50 J / cm ² , more preferably from 100 to 800 mJ / cm ² . Light irradiation may be performed under heating conditions to promote the photopolymerization reaction.

The thickness of the optically anisotropic layer is 0.1 to 10
μm, more preferably 0.5 to 5 μm, and most preferably 1 to 5 μm. . However, depending on the mode of the liquid crystal cell, in order to obtain high optical anisotropy, the optically anisotropic layer is thickened (3
To 10 μm) in some cases. As described above, the alignment state of liquid crystal molecules in the optically anisotropic layer is determined according to the type of display mode of the liquid crystal cell. Specifically, the alignment state of liquid crystal molecules is controlled by the types of liquid crystal molecules, types of alignment films, and the use of additives (eg, plasticizers, binders, and surfactants) in the optically anisotropic layer. You.

[Liquid crystal display device] The elliptically polarizing plate of the present invention comprises:
It can be applied to liquid crystal cells of various display modes. Already TN
(Twisted Nematic), IPS (In-Plane Switchin)
g), FLC (Ferroelectric Liquid Crystal), OC
B (Optically Compensatory Bend), STN (Supper
Various display modes such as Twisted Nematic, VA (Vertically Aligned) or HAN (Hybrid Aligned Nematic) have been proposed. The elliptically polarizing plate of the present invention,
This is particularly effective in a TN mode liquid crystal display device.

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EXAMPLES Example 1 (Preparation of Transparent Support) At room temperature, the average acetylation degree was 60.
45 parts by weight of 9% cellulose acetate, 1.35 parts by weight of the following retardation increasing agent (1), 2.75 parts by weight of triphenyl phosphate (plasticizer), 2.20 parts by weight of biphenyl diphenyl phosphate (plasticizer) , 232.72 parts by weight of methylene chloride, 42.57 parts by weight of methanol and 8.50 parts by weight of n-butanol to prepare a solution (dope).

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The obtained dope was cast and dried using a band casting machine having an effective length of 6 m so that the dry film thickness became 100 μm. About the obtained cellulose acetate film (transparent support), an ellipsometer (M-15)
0, manufactured by JASCO Corporation, the thickness direction retardation (Rth) at a wavelength of 600 nm was measured and found to be 80 nm. The in-plane retardation (Re) was 10 nm. Further, as a wavelength dispersion value of the refractive index anisotropy of the transparent support, Δn (4) which is the refractive index anisotropy of the transparent support measured with light having a wavelength of 450 nm.
50) and the ratio of Δn (600), which is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm, Δn (450)
The measured value of / Δn (600) was 0.86.

(Formation of Alignment Film)
A 1 μm thick gelatin subbing layer was provided. On the undercoat layer, a long-chain alkyl-modified polyvinyl alcohol (MP-
203, manufactured by Kuraray Co., Ltd.), dried with hot air at 60 ° C. for 90 seconds, and then rubbed to form an alignment film.

(Formation of Optically Anisotropic Layer) 1.8 g of the following discotic liquid crystalline compound, ethylene oxide-modified trimethylolpropane triacrylate (V # 36)
0, manufactured by Osaka Organic Chemical Co., Ltd.) 0.2 g, cellulose acetate butyrate (CAB531-1.0, manufactured by Eastman Chemical Company) 0.04 g, photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 0.06 g and a sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.)
Was dissolved in 8.43 g of methyl ethyl ketone to prepare a coating solution. The coating solution was applied on the alignment film using a # 2.5 wire bar. This was adhered to a metal frame and heated in a thermostat at 130 ° C. for 2 minutes to align the discotic liquid crystalline compound. While maintaining the temperature of 130 ° C., ultraviolet rays were irradiated for 1 minute using a high-pressure mercury lamp of 120 W / cm to polymerize the vinyl group of the discotic liquid crystal compound and fix the alignment state. Then, it was left to cool to room temperature.

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The thickness of the optically anisotropic layer was 1.0 μm. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 14.5 °, and the retardation in the thickness direction (Rth ) Was 135 nm, and the in-plane retardation (Re) was 25 nm.

(Preparation of Transparent Protective Film) A cellulose acetate film (transparent protective film) was prepared in the same manner as in the preparation of the transparent support, except that the retardation increasing agent was not added.
Was prepared.

(Preparation of Elliptical Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. On one side of the polarizing film, a laminate of an optically anisotropic layer and a transparent support was attached using a polyvinyl alcohol-based adhesive so that the optically anisotropic layer was on the outside. On the opposite side, a transparent protective film was attached using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the laminate of the optically anisotropic layer and the transparent support were arranged in parallel. Thus, an elliptically polarizing plate was produced. An elliptically polarizing plate is attached to a glass plate using an acrylic adhesive, and after aging under high temperature and pressure, 90 ° C.
And left for 500 hours. Examination of the elliptically polarizing plate revealed no problems such as peeling, generation of bubbles, or generation of wrinkles. After 500 hours (1000 hours in total) in a 90 ° C thermostat,
No problems such as peeling, generation of bubbles or generation of wrinkles were observed.

(Production of Liquid Crystal Display Device) A polyimide alignment film was provided on a glass substrate provided with an ITO transparent electrode, and rubbing treatment was performed. Two substrates were stacked via a 5 μm spacer so that the alignment films faced each other. The orientation of the substrate was adjusted so that the rubbing directions of the alignment films were orthogonal. In the gap between the substrates, rod-like liquid crystal molecules (ZL479
2, manufactured by Merck) to form a liquid crystal layer. Δn of the liquid crystal molecule was 0.0969. An elliptically polarizing plate was attached to both sides of the TN liquid crystal cell manufactured as described above so that the optically anisotropic layer faced the substrate, thereby manufacturing a liquid crystal display device. The slow axis of the laminate of the optically anisotropic layer and the transparent support was arranged to be orthogonal to the rubbing direction of the liquid crystal cell. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as the contrast ratio. The non-existing area was measured as the viewing angle. As a result, the vertical viewing angle was 70 ° and the horizontal viewing angle was 126 °. The front contrast is 12
It was 2.

Example 2 (Formation of Optically Anisotropic Layer) On the transparent support prepared in Example 1, an alignment film was formed in the same manner as in Example 1. On the alignment film, a # 3.4 wire bar (# 1 in Example 1)
An optically anisotropic layer was formed in the same manner as in Example 1 except that 2.5) was used. The thickness of the optically anisotropic layer is 1.4 μm
Met. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 18 °, and the retardation (Rth) in the thickness direction was: The in-plane retardation (Re) was 180 nm and the in-plane retardation (Re) was 55 nm.

(Preparation of Elliptically Polarizing Plate) An elliptically polarizing plate was prepared in the same manner as in Example 1 except that a laminate of the transparent support and the optically anisotropic layer prepared as described above was used. The elliptically polarizing plate was attached to a glass plate using an acrylic adhesive, aged under high temperature and pressure, and then placed in a thermostat at 90 ° C. and left for 500 hours. Examination of the elliptically polarizing plate revealed no problems such as peeling, generation of bubbles, or generation of wrinkles. 500 hours (total 1000 hours)
Time) Even after examination in a thermostat at 90 ° C., no problems such as peeling, generation of bubbles, and generation of wrinkles were found.

(Production of Liquid Crystal Display) A liquid crystal display was produced in the same manner as in Example 1 except that the above-mentioned elliptically polarizing plate was used. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as the contrast ratio. The non-existing area was measured as the viewing angle. As a result, the vertical viewing angle was 80 ° and the horizontal viewing angle was 124 °. The front contrast was 118.

[Example 3] (Preparation of transparent support) Retardation increasing agent (1)
Same as Example 1 except that instead of 1.35 parts by weight, a mixture of 1.01 part by weight of the retardation increasing agent (1) and 0.24 part by weight of the following retardation increasing agent (2) was used. To produce a transparent support.

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The obtained transparent support was measured for retardation (R) in the thickness direction at a wavelength of 600 nm using an ellipsometer (M-150, manufactured by JASCO Corporation).
When th) was measured, it was 80 nm. The in-plane retardation (Re) was 10 nm. Further, as a wavelength dispersion value of the refractive index anisotropy of the transparent support,
The ratio of Δn (450), which is the refractive index anisotropy of the transparent support measured with light having a wavelength of 450 nm, to Δn (600), which is the refractive index anisotropy of the transparent support measured with a wavelength of 600 nm, Δn ( When (450) / Δn (600) was measured, it was 0.86.

(Formation of Optically Anisotropic Layer) On the prepared transparent support, an alignment film and an optically anisotropic layer were formed in the same manner as in Example 1. The thickness of the optically anisotropic layer is 1.0
μm. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 14.5 °, and the retardation in the thickness direction (Rth ) Was 148 nm and the in-plane retardation (Re) was 25 nm.

(Preparation of Elliptically Polarizing Plate) An elliptically polarizing plate was prepared in the same manner as in Example 1, except that a laminate of the transparent support and the optically anisotropic layer prepared as described above was used. The elliptically polarizing plate was attached to a glass plate using an acrylic adhesive, aged under high temperature and pressure, and then placed in a thermostat at 90 ° C. and left for 500 hours. Examination of the elliptically polarizing plate revealed no problems such as peeling, generation of bubbles, or generation of wrinkles. 500 hours (total 1000 hours)
Time) Even after examination in a thermostat at 90 ° C., no problems such as peeling, generation of bubbles, and generation of wrinkles were found.

(Preparation of Liquid Crystal Display) A liquid crystal display was prepared in the same manner as in Example 1 except that the above-mentioned elliptically polarizing plate was used. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as the contrast ratio. The viewing angle was measured with the region not present as the viewing angle. As a result, the upper and lower viewing angles are 70
゜, the left and right viewing angles were 126 °. The front contrast was 122.

Comparative Example 1 (Preparation of Transparent Support) A cellulose acetate film (transparent support) was prepared in the same manner as in Example 1, except that no retardation increasing agent was added. About the obtained transparent support, an ellipsometer (M-150,
The retardation in the thickness direction (Rth) at a wavelength of 600 nm was measured using JASCO Corporation, and found to be 40 nm. The in-plane retardation (Re) was 10 nm. Further, as a wavelength dispersion value of the refractive index anisotropy of the transparent support, Δn (45) which is the refractive index anisotropy of the transparent support measured with light having a wavelength of 450 nm.
0) and Δn (600), which is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm, Δn (450) /
The measured Δn (600) was −5.80.

(Formation of Optically Anisotropic Layer) On the prepared transparent support, an alignment film and an optically anisotropic layer were formed in the same manner as in Example 1. The thickness of the optically anisotropic layer is 1.0
μm. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 22.5 °, and the retardation in the thickness direction (Rth ) Was 110 nm, and the in-plane retardation (Re) was 25 nm.

(Preparation of Elliptically Polarizing Plate) An elliptically polarizing plate was prepared in the same manner as in Example 1 except that a laminate of the transparent support and the optically anisotropic layer prepared as described above was used.

(Production of Liquid Crystal Display) A liquid crystal display was produced in the same manner as in Example 1 except that the above-mentioned elliptically polarizing plate was used. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as the contrast ratio. The viewing angle was measured with the region not present as the viewing angle. As a result, the upper and lower viewing angles are 70
゜, the left and right viewing angles were 124 °. The front contrast was 120.

Comparative Example 2 (Preparation of Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. Two transparent protective films prepared in Example 1 were attached to both sides of the polarizing film using a polyvinyl alcohol-based adhesive. Thus, a polarizing plate was produced.

(Production of Liquid Crystal Display) A liquid crystal display was produced in the same manner as in Example 1 except that the above-mentioned polarizing plate was used in place of the elliptically polarizing plate. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as a contrast ratio.
The viewing angle was measured using a region having a contrast ratio of 10 at the top, bottom, left and right and no gradation inversion as a viewing angle. As a result, the vertical viewing angle was 50 ° and the horizontal viewing angle was 70 °. The front contrast was 120.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a TN liquid crystal display device using an integrated elliptically polarizing plate.

FIG. 2 is a schematic view of an integrated elliptically polarizing plate.

[Description of Signs] BL backlight 1 Lower elliptically polarizing plate 2 TN liquid crystal cell 3 Upper elliptically polarizing plate TA1, TA3 Transmission axis of polarizing film SA1, SA3 Slow phase of laminate of transparent support and optically anisotropic layer Axis RD1, RD2 Rubbing direction of alignment film provided in liquid crystal cell 11 Transparent protective film 12 Polarizing film 13 Transparent support 14 Optically anisotropic layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA04 BA06 BA27 BA42 BB33 BB43 BB49 BC05 BC09 BC22 2H091 FA08X FA08Z FA11X FA11Z FB02 FB12 FC01 FC23 FD08 FD10 FD14 GA06 HA07 KA02 LA11 LA12 4H027 BA02 BB03

Claims (7)

[Claims] 1. An elliptically polarizing plate comprising a transparent protective film, a polarizing film, a transparent support and an optically anisotropic layer formed of liquid crystal molecules laminated in this order, wherein the transparent support has a thickness of 0.7%.
An elliptically polarizing plate having a wavelength dispersion value of refractive index anisotropy defined by the following formula within the range of less than 1.3. α = Δn (450) / Δn (600) where α is the wavelength dispersion value of the refractive index anisotropy of the transparent support; Δn (450) is the refractive index of the transparent support measured with light having a wavelength of 450 nm. Anisotropic; and Δn (60
0) is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm. 2. The laminate of the transparent support and the optically anisotropic layer has a Re retardation value defined by the following formula in the range of 0 to 100 nm, and 20 to 400
The elliptically polarizing plate according to claim 1, which has an Rth retardation value defined by the following formula within the range of nm. Re = │nx-ny│ × d Rth = {(n1 + n2) / 2−n3} × d where nx and ny are the in-plane principal refractive indexes of the laminate; d is the thickness of the laminate (nm) ); And n1,
n2 and n3 are the triaxial refractive indexes of the laminate satisfying n1 ≧ n2 ≧ n3. 3. The elliptically polarizing plate according to claim 1, wherein the slow axis of the laminate of the transparent support and the optically anisotropic layer is substantially parallel to the transmission axis of the polarizing film. 4. The elliptically polarizing plate according to claim 1, wherein the liquid crystal molecules are discotic liquid crystal molecules. 5. The elliptically polarizing plate according to claim 1, wherein the liquid crystalline molecules are fixed while being oriented by polymerization. 6. The elliptically polarizing plate according to claim 1, wherein the transparent support is a cellulose ester film. 7. A TN type liquid crystal cell and two polarizing elements disposed on both sides of the TN type liquid crystal cell, and at least one of the polarizing elements comprises a transparent protective film, a polarizing film, a transparent support, and a liquid crystal molecule in order from the outside. A TN type liquid crystal display device which is an elliptically polarizing plate on which formed optically anisotropic layers are laminated, wherein a transparent support is defined by the following formula within a range of 0.7 or more and less than 1.3. A TN liquid crystal display device having a wavelength dispersion value of refractive index anisotropy. α = Δn (450) / Δn (600) where α is the wavelength dispersion value of the refractive index anisotropy of the transparent support; Δn (450) is the refractive index of the transparent support measured with light having a wavelength of 450 nm. Anisotropic; and Δn (60
0) is the refractive index anisotropy of the transparent support measured at a wavelength of 600 nm.