JP2001100205A - Guest-host reflection type liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a guest-host reflection type liquid crystal display element having high reflection brightness, a high contrast ratio and thin thickness. SOLUTION: In a guest-host reflection type liquid crystal display element provided with a λ/4 plate, one sheet of a polymer film having 100-125 nm and 135-160 nm retardation values when measured with light having 450 nm and 590 nm wavelengths respectively is utilized as the λ/4 plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guest-host reflection type liquid crystal display device having a .lambda. / 4 plate.

[0002]

2. Description of the Related Art As a guest-host reflection type liquid crystal display device, a phase transition type (White-Taylor type), a two-layer type and a λ / 4 type are known. The phase transition type is a method in which a chiral agent is added to a mixture of a liquid crystal and a dichroic dye, and switching is performed between a cholesteric phase and vertical alignment. In this method, monochrome display can be performed with one liquid crystal layer. However, there is a problem that the contrast ratio is low, the driving voltage is high, and there is hysteresis, and it is difficult to display a gradation. The two-layer type is a method in which two layers of a mixture of a liquid crystal and a dichroic dye are provided. This method is characterized in that the contrast ratio is high. However, there is a problem that the liquid crystal display element is thick and causes parallax. The λ / 4 type is a method of combining a layer composed of a mixture of liquid crystal and a dichroic dye with a λ / 4 plate. λ / 4 type is
The thickness is thin, and the problem of parallax is solved. Japanese Patent Application Laid-Open Nos. 6-222350, 8-36174, and 10-2 describe a guest-host reflection type liquid crystal display device having a λ / 4 plate.
No. 68300, No. 10-292175, No. 10-29
No. 3301, No. 10-319776, No. 10-319
No. 442, No. 10-325595, No. 10-3331
No. 38 and Nos. 11-38410.

[0003]

In a guest-host reflection type liquid crystal display device having a λ / 4 plate, the performance of the λ / 4 plate is very important. Even though the conventional λ / 4 plate is called “λ / 4 plate”, most of the conventional λ / 4 plates achieve λ / 4 at a certain specific wavelength. If the wavelength range in which λ / 4 can be achieved is narrow, the contrast of a displayed image is reduced. JP-A-5-2
Nos. 7118 and 5-27119 disclose a retardation plate in which a birefringent film having a large retardation and a birefringent film having a small retardation are laminated so that their optical axes are orthogonal to each other. Is disclosed. However, when two films are stacked, the λ / 4 plate becomes thicker, and the advantage of a thin liquid crystal display device is reduced. Further, when the light passes through the thick λ / 4 plate, the light is attenuated, and the reflection luminance is reduced. An object of the present invention is to provide a guest-host reflection type liquid crystal display device having a high reflection luminance, a high contrast ratio, and a small thickness.

[0004]

The object of the present invention has been attained by the following guest-host reflection type liquid crystal display elements (1) to (7). (1) A guest-host reflective liquid crystal display device provided with a λ / 4 plate, wherein the λ / 4 plate has a retardation value of 100 to 125 nm measured at a wavelength of 450 nm and a retardation measured at a wavelength of 590 nm. Value is 135
1. A guest-host reflection type liquid crystal display element comprising a single polymer film having a thickness of from 160 to 160 nm. (2) When the λ / 4 plate has a refractive index nx in the in-plane slow axis direction, a refractive index ny in a direction perpendicular to the slow axis in the plane, and a refractive index nz in the thickness direction, nx>nz> ny. The guest-host reflective liquid crystal display device according to (1), which satisfies the relationship. (3) The λ / 4 plate has a retardation value of 108 to 117 nm measured at a wavelength of 450 nm and a wavelength of 550
The retardation value measured in nm is 133 to 142
The guest-host reflection type liquid crystal display device according to (1), comprising a single polymer film having a retardation value of 143 to 152 nm measured at a wavelength of 590 nm.

(4) The guest-host reflection type liquid crystal display device according to (1), wherein the λ / 4 plate is made of a cellulose ester film. (5) The guest-host reflection type liquid crystal display device according to (4), wherein the λ / 4 plate is formed of a stretched cellulose ester film. (6) The guest-host reflection type liquid crystal display according to (4), wherein the cellulose ester film includes a compound having a molecular structure having at least two aromatic rings and having no steric hindrance to the conformation of the two aromatic rings. element. (7) The guest-host reflection type liquid crystal display device according to (1), wherein the λ / 4 plate is formed of a single polymer film having a thickness of 1 to 500 μm.

[0006]

As a result of research, the present inventor has succeeded in producing a polymer film that achieves λ / 4 in a wide wavelength range by adjusting the material and the production method of the polymer film. A λ / 4 plate made of one polymer film that can achieve λ / 4 in a wide wavelength range
It can be very advantageously used for a guest-host reflection type liquid crystal display device. That is, since λ / 4 is achieved in a wide wavelength region, a guest-host reflection type liquid crystal display device having a high contrast ratio can be obtained. Also, since the thickness of the λ / 4 plate is small, the liquid crystal display element as a whole can be designed to be thin. Further, since the thickness of the λ / 4 plate is small, it is possible to display an image with little light attenuation and high reflection luminance.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION [λ / 4 plate]
The retardation value measured at 50 nm is 100 to 1
One polymer film having a retardation of 135 to 160 nm measured at a wavelength of 590 nm and having a wavelength of 25 nm is used as a λ / 4 plate. 450n wavelength
The retardation value measured in m is 108 to 117n
m, the retardation value measured at a wavelength of 550 nm is 133 to 142 nm, and the wavelength is 590 nm.
The retardation value measured at 143 to 152 nm
It is preferable that Retardation value (Re)
Is calculated according to the following equation. Retardation value (Re) = (nx−ny) × d where nx is the in-plane refractive index in the plane of the λ / 4 plate (maximum in-plane refractive index); ny is λ / 4 The index of refraction in the direction perpendicular to the slow axis direction in the plane of the plate; and d is λ / 4
The thickness (nm) of the plate.

It is preferable that the polymer film used as the λ / 4 plate further satisfies the following expression. nx>nz> ny, where nx is the refraction in the in-plane slow axis direction; ny is the refractive index in the direction perpendicular to the in-plane slow axis;
Is the refractive index nz in the thickness direction. The thickness of one polymer film constituting the polymer film is 1 to 500.
More preferably, it is μm. The retardation plate having the above optical properties can be manufactured by the following materials and methods.

[Polymer] The polymer forming the polymer film is preferably a cellulose ester, more preferably a lower fatty acid ester of cellulose. 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 degree of acetylation (acetylation degree) of cellulose acetate is preferably from 45.0 to 62.5%, more preferably from 55.0 to 61.0%.

[Retardation Controlling Agent] It is preferable to use a compound having at least two aromatic rings and having a molecular structure that does not hinder the conformation of the two aromatic rings. The retardation adjusting agent is preferably used in an amount of 0.2 to 20 parts by weight based on 100 parts by weight of the polymer.
It is more preferably used in the range of 1 to 10 parts by weight, and most preferably used in the range of 1 to 5 parts by weight. Two or more retardation modifiers may be used in combination. 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 study of the present inventors, it is important to form the same plane with a plurality of aromatic rings in order to adjust the retardation of a polymer film. 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 regulator is preferably from 2 to 20, and 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 regulator is 30
It is preferably from 0 to 800. Preferably, the boiling point of the retardation regulator is 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).
The retarder described above is disclosed in EP 091
In the specification of 1656A2, it is specifically described as a retardation increasing agent for cellulose ester film. However, in the present invention, it is used not for simply increasing the retardation, but for achieving λ / 4 in a wide wavelength region by adjusting the wavelength dispersion of the retardation value.

[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 is dissolved in an organic solvent. The organic solvent is an ether having 3 to 12 carbon atoms,
It is preferable to include a solvent selected from ketones having 3 to 12 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. 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 polymer 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 the polymer is adjusted so that the obtained solution contains 10 to 40% by weight. More preferably, the amount of polymer 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 polymer 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 polymer and the organic solvent are placed 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 2
It is 00 ° C, 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 a cooling dissolution method. In the cooling dissolution method, the polymer 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 a polymer by a usual dissolution method, the cooling dissolution method has an effect that a uniform solution can be obtained quickly. In the cooling dissolution method, first, a polymer is gradually added to an organic solvent with stirring at room temperature. The amount of polymer is between 10 and 4 in this mixture.
It is preferable to adjust so as to contain 0 wt%. More preferably, the amount of polymer is from 10 to 30% by weight. Further, an optional additive described below may be added to the mixture.

Next, the mixture is cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -10 ° C).
To -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon such cooling, the mixture of polymer and organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, and 8 ° C./min.
Minutes or more, and most preferably 12 ° C./minute or more. The higher the cooling rate, the better, 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. 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,
Upon heating to (most preferably 0 to 50 ° C.), the polymer 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. Heating rate is 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 fast as possible.
00 ° C / sec is the theoretical upper limit, 1000 ° C / sec is the technical upper limit, and 100 ° C / sec is the practical upper limit. Note that the heating rate is a value obtained by dividing the difference between the temperature at which heating is started and the final heating temperature by the time from when the heating is started until the final heating temperature is reached. . As described above, a uniform solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated.
Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution.

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

From the prepared polymer solution (dope), a polymer 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 US Pat.
No. 36310, No. 2367603, No. 2492078
Nos. 2492977, 2492978, 26
No. 07704, No. 2739069, No. 2739070
Nos., British Patent Nos. 640731 and 736892, Japanese Patent Publication Nos. 45-4554 and 49-5614,
JP-A-60-176834 and JP-A-60-203430
And JP-A-62-115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. It is preferable to dry the film by blowing it for 2 seconds or more. The obtained film is peeled off from the drum or band, and further heated at 100 to 160 ° C.
It is also possible to evaporate the residual solvent by drying with a high-temperature air having a temperature which is sequentially changed up to the above. The above method is described in Tokuhei 5-178.
No. 44 discloses this. 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 manufactured is 40 to 12
The thickness is preferably 0 μm, more preferably 70 to 100 μm.

A plasticizer can be added to the polymer film in order to improve mechanical properties or to increase the drying speed. As the plasticizer, a phosphoric acid ester or a carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP)
And tricresyl phosphate (TCP). Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DB
P), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include:
Includes O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB). Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic esters. Phthalate ester plasticizers (DMP, DEP, DBP, D
OP, DPP, DEHP) are preferably used. DE
P and DPP are particularly preferred. The amount of the plasticizer added is preferably 0.1 to 25% by weight, more preferably 1 to 20% by weight, and most preferably 3 to 15% by weight of the amount of the cellulose ester.

[0030] The polymer film has a deterioration inhibitor (eg,
Antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added. Regarding the deterioration inhibitor, see JP-A-3-1992
No. 01, 5-1907073, 5-194789
And JP-A-5-271471 and JP-A-6-107854. The amount of the deterioration inhibitor added is preferably 0.01 to 1% by weight, more preferably 0.01 to 0.2% by weight of the solution (dope) to be prepared. If the amount is less than 0.01% by weight, the effect of the deterioration inhibitor is hardly recognized. 1% by weight
Exceeding the limit may cause bleed-out (bleeding-out) of the deterioration inhibitor to the film surface. A particularly preferred example of the deterioration inhibitor is butylated hydroxytoluene (BHT). The UV inhibitors are described in JP-A-7-11056.

The polymer film is further subjected to a stretching treatment to obtain a refractive index (refractive index nx in the in-plane slow axis direction, refractive index ny in the direction perpendicular to the in-plane slow axis, and refractive index n in the thickness direction).
It is preferable to adjust z). When the intrinsic birefringence is positive, the refractive index increases in the direction in which the polymer chains are oriented.
When stretching such a polymer having a positive intrinsic birefringence,
Usually, the refractive index satisfies nx> ny ≧ nz. This is because the x-component of the polymer chain oriented in the in-plane direction is increased by stretching, and the z-component is minimized. nx
In order to satisfy the relationship>nz> ny, it is necessary to make the z component of the polymer chain larger than the y component so that nz becomes larger than ny. That is, it is necessary to stretch in some way in the z direction.

Specifically, a heat-shrinkable film is adhered to one or both surfaces of a polymer film, and the laminate is subjected to a heat stretching treatment to apply a shrinking force in a direction perpendicular to the stretching direction of the polymer film (Patent 2818983, JP-A-5-297223 and JP-A-5-323120). When the heat-shrinkable film shrinks, the x and y components of the polymer chain decrease and the z component increases accordingly, so that nz becomes larger than ny. At the same time, nx is increased by stretching in the x direction. In addition, there is a method of uniaxially stretching the polymer film in a plane while applying an electric field (described in JP-A-6-88909). In this method, by applying an electric field, the component parallel to the electric field of the polymer chain increases, so that nz can be increased.

Further, a method of repeating a bending operation in a state where a temperature difference is applied to both surfaces of a polymer film (Japanese Patent No. 281)
No. 1137). When the polymer film is bent in an arc shape with the outside at low temperature and the inside at high temperature,
A condition is created in which the polymer chains inside the film are compressed while the polymer chains outside the film are hardly stretched. In the compressed portion, the z component of the polymer chain increases, and nz increases. Next, by bending to the opposite side and reversing the temperature difference, z
Ingredients can be increased. By repeating this operation alternately, nx>nz> ny can be realized. In the above description, a polymer having a positive intrinsic birefringence has been described as an example. However, even if a polymer has a negative intrinsic birefringence, a polymer film that satisfies the relationship of nx>nz> ny by stretching in the z-direction. Can be realized.

[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. 1 includes a lower substrate (1), an organic interlayer insulating film (2), a metal reflector (3), a λ / 4 plate (4), a lower transparent electrode (5), and a lower transparent electrode (5). An alignment film (6), a liquid crystal layer (7), an upper alignment film (8), an upper transparent electrode (9), a light diffusion plate (10), an upper substrate (11), and an antireflection layer (12) are laminated in this order. It has the structure which was done. Lower substrate (1) and upper substrate (2)
Consists of a glass plate or a plastic film. A TFT is provided between the lower substrate (1) and the organic interlayer insulating film (2).
(13) is attached. The liquid crystal layer (7) 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 (14). Instead of providing the light diffusion plate (10), the metal reflection plate (3) may have a light diffusion function by providing irregularities on the surface of the metal reflection plate (3). The antireflection layer (12) preferably has an antiglare function in addition to the antireflection function.

FIG. 2 is a schematic sectional view showing another typical embodiment of the guest-host reflection type liquid crystal display device. The guest-host reflective liquid crystal display device shown in FIG. 2 includes a lower substrate (1),
Organic interlayer insulating film (2), cholesteric color reflector (3), λ / 4 plate (4), lower transparent electrode (5), lower alignment film (6), liquid crystal layer (7), upper alignment film (8) The upper transparent electrode (9), the upper substrate (11) and the antireflection layer (12)
It has a structure laminated in this order. The lower substrate (1) and the upper substrate (2) are made of a glass plate or a plastic film. The TFT (13) is attached between the lower substrate (1) and the organic interlayer insulating film (2). The λ / 4 plate (4) may also function as a light diffusion plate. The liquid crystal layer (7) 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 (14). A black matrix (15) is attached between the upper transparent electrode (9) and the upper substrate (11). The antireflection layer (12) preferably has an antiglare function in addition to the antireflection function.

The λ / 4 plate according to the present invention is shown in FIGS.
Can be used as the λ / 4 plate (4) of the guest-host reflection type liquid crystal display device described in (1). A guest-host reflection type liquid crystal display device having a λ / 4 plate is disclosed in JP-A-6-2223.
No. 50, No. 8-36174, No. 10-268300
No., No. 10-292175, No. 10-293301
No. 10-311976, No. 10-319442
No., No. 10-325595, No. 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.

[0037]

[Example 1] (Preparation of λ / 4 plate) At room temperature, average acetylation degree was 60.9.
% Cellulose acetate 45 parts by weight, the following retardation adjuster (1) 0.675 parts by weight, the following retardation adjuster (2) 0.225 parts by weight, methylene chloride 232.72 parts by weight, methanol 42.57 Parts by weight and 8.50 parts by weight of n-butanol were mixed to prepare a solution (dope).

[0038]

Embedded image

The obtained dope is cast on a glass plate,
After drying at room temperature for 1 minute, it was dried at 50 ° C. for 5 minutes. The volatile content after drying was 3% by weight. The cellulose acetate film was separated from the glass plate, and a heat-shrinkable film having a thickness of 100 μm (Ryotube, manufactured by Mitsubishi Kasei Co., Ltd.) was stuck on both surfaces of the film and uniaxially stretched at 120 ° C. Thereafter, the heat shrinkable film was peeled off from both sides of the film. The dry thickness of the obtained cellulose acetate film was 200 μm. The obtained cellulose acetate film (retardation 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). , 112.8 nm, 137.
5 nm and 145.1 nm. Therefore, this cellulose acetate film has a wavelength of λ / 4 in a wide wavelength range.
Had been achieved. Furthermore, from the refractive index measurement by the Abbe refractometer and the measurement of the angle dependence of the retardation, the in-plane refractive index nx at the wavelength of 550 nm in the slow axis direction was obtained.
When the refractive index ny in the direction perpendicular to the in-plane slow axis and the refractive index nz in the thickness direction were calculated, nx = 1.4903.
9, ny = 1.48970 and nz = 1.4900. Therefore, this cellulose acetate film
The retardation value was substantially constant even when viewed from the oblique direction (attained λ / 4 when viewed from the oblique direction).

(Preparation of Liquid Crystal Display Element) A solution of a polymer for forming a vertical alignment film (LQ-1800, manufactured by Hitachi Chemical DuPont Microsystems) is applied on a glass substrate provided with an ITO transparent electrode, and dried. A rubbing treatment was performed. The prepared λ / 4 plate was adhered with an adhesive on a glass substrate on which aluminum was deposited as a reflection plate. λ / 4
An SIO layer was provided on the plate by sputtering, and an ITO transparent electrode was provided thereon. On a transparent electrode, a solution of a polymer for forming a vertical alignment film (LQ-1800, manufactured by Hitachi Chemical DuPont Microsystems) is applied, and after drying, λ
Rubbing treatment was performed in a direction at 45 ° from the slow axis direction of the 板 plate. Two glass substrates were stacked via a 7.6 μm spacer such 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-1366,
2.0% by weight (manufactured by Nippon Kogaku Dyeing Co., Ltd.) and a liquid crystal
(Manufactured by Merck & Co., Ltd., 98.0% by weight) was injected by a vacuum injection method to form a liquid crystal layer. 1 kHz between the ITO electrodes of the fabricated guest-host reflective liquid crystal display device
A rectangular wave voltage of z was applied. White display 1V, black display 10V
Were 65% and 6%, respectively. The transmittance ratio (contrast ratio) between white display and black display is 11:
It was one. When the viewing angle at which a contrast ratio of 2: 1 was obtained in the upper, lower, left, and right directions was measured, 1
It was more than 20 mm. The transmittance was measured while increasing and decreasing the voltage, but no hysteresis was observed in the transmittance-voltage curve.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display device.

FIG. 2 is a schematic 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 organic interlayer insulating film 3 metal reflector 4 λ / 4 plate 5 lower transparent electrode 6 lower alignment film 7 liquid crystal layer 8 upper alignment film 9 upper transparent electrode 10 light diffusion plate 11 upper substrate 12 antireflection layer 13 TFT 14 Spacer 15 Black matrix

Claims (7)

[Claims] 1. A guest-host reflection type liquid crystal display device provided with a λ / 4 plate, wherein the λ / 4 plate has a retardation value of 100 to 125 nm measured at a wavelength of 450 nm and measured at a wavelength of 590 nm. A guest-host reflection type liquid crystal display device comprising a single polymer film having a retardation value of 135 to 160 nm. 2. The λ / 4 plate has a refractive index nx in the in-plane slow axis direction, a refractive index ny in a direction perpendicular to the slow axis in the plane, and a refractive index nz in the thickness direction, nx>nz>. 2. The guest-host reflection type liquid crystal display device according to claim 1, wherein the relationship of ny is satisfied. 3. The λ / 4 plate has a retardation measured at a wavelength of 450 nm of 108 to 117 nm, a retardation measured at a wavelength of 550 nm of 133 to 142 nm, and a retardation measured at a wavelength of 590 nm. 2. The guest-host reflection type liquid crystal display device according to claim 1, comprising a single polymer film having a thickness of 143 to 152 nm. 4. The guest-host reflection type liquid crystal display device according to claim 1, wherein the λ / 4 plate is made of a cellulose ester film. 5. The guest-host reflection type liquid crystal display device according to claim 4, wherein the λ / 4 plate is made of a stretched cellulose ester film. 6. The cellulose ester film contains 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.
3. The guest-host reflection type liquid crystal display device according to item 1. 7. The guest-host reflection type liquid crystal display device according to claim 1, wherein the λ / 4 plate is made of a single polymer film having a thickness of 1 to 500 μm.