JPH0821996A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce the complicated sticking process and to provide a liquid crystal display device which is inexpensive, whose angle of visibility is wide and whose reliability under high temperature and high humidity condition is high. CONSTITUTION:This device possesses at least an elliptically polarizing plate where a polarizing element and an optical anisotropic element (A) which is optically negative uniaxial and of which optical axis is in the normal direction, are laminated, a TN liquid crystal cell and the optical anisotropic element (B) which is optically negative uniaxial and of which optical axis inclines by 5 deg.-50 deg. from the normal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device having an elliptically polarizing plate using, as a protective film for a polarizing element, an optically anisotropic element (A) which is optically uniaxial and has its optical axis in the normal direction of the film.

[0002]

2. Description of the Related Art Display devices for OA equipment such as Japanese word processors and desktop personal computers are mainly used in CRTs.
Therefore, it is being converted to a liquid crystal display element (hereinafter referred to as LCD) which has great advantages of thin and light weight and low power consumption. Many of the currently widespread LCDs use twisted nematic liquid crystals. The display method using such a liquid crystal can be roughly classified into a birefringence mode and an optical rotation mode.

A display element using a birefringence mode (STN type LCD) has a twist angle of a liquid crystal molecule arrangement of 90 ° or more and has a steep electro-optical characteristic, so that there is no active element (thin film transistor or diode). However, a large-capacity display can be obtained by time-division driving with a simple matrix electrode structure. However, it has a drawback that response speed is slow (several hundred milliseconds) and gradation display is difficult, and it does not exceed the display performance of a liquid crystal display element (TFT-LCD or MIM-LCD) using active elements. .

For the TFT-LCD and the MIM-LCD, an optical rotation mode display mode (TN type LCD) in which the alignment state of liquid crystal molecules is twisted by 90 ° is used. This display method is the most effective method compared with other LCDs because it has a high response speed (several tens of milliseconds), can easily obtain a monochrome display, and has a high display contrast. But,
Since the twisted nematic liquid crystal is used, there is a problem in view angle characteristics that the display color and the display contrast change depending on the viewing direction due to the principle of the display system, and the display performance of the CRT cannot be exceeded.

Japanese Unexamined Patent Publication Nos. 4-229828 and 4-2.
As disclosed in Japanese Patent No. 58923, a method has been proposed in which a viewing angle is increased by disposing a retardation film between a pair of polarizing plates and a TN type liquid crystal cell. The retardation film proposed in the above patent publication has a retardation in the direction perpendicular to the liquid crystal cell of almost zero, exerts no optical action from the front, and retards when tilted. Occurs, and the phase difference developed in the liquid crystal cell is compensated. However, even by these methods, the viewing angle of the LCD, specifically, the phenomenon of coloring (coloring phenomenon) or black and white reversal (reversal phenomenon) of the display image when tilted vertically or horizontally from the screen normal direction However, in particular, when it is considered to be mounted on a vehicle or as a substitute for a CRT, the current situation is that it cannot respond at all.

In JP-A-4-366808 and JP-A-4-366809, a viewing angle is improved by using a liquid crystal cell containing a chiral nematic liquid crystal having an inclined optical axis as a retardation film. This is a layer liquid crystal system, which is expensive and very heavy. Further, in JP-A-4-113301, JP-A-5-80323, and JP-A-5-157913, a retardation film in which a polymer chain, an optical axis or an optical elastic axis is inclined with respect to a liquid crystal cell is used. However, there is a problem that it is difficult to obtain a large-area retardation film at low cost, such as by slicing uniaxial polycarbonate obliquely. Further, although reference is made to the improvement of the viewing angle of the STN-LCD, no specific effect is shown for the improvement of the viewing angle of the TN-LCD. Further, Japanese Patent Laid-Open No. 5-215921 proposes a method of optically compensating an LCD by a birefringent plate in which a rod-shaped compound, which exhibits liquid crystallinity when cured, is sandwiched between a pair of substrates subjected to alignment treatment. However, this plan is no different from the so-called double-cell type compensator that has been proposed in the past, and it causes a great increase in cost and is practically unsuitable for mass production. Further, no effect has been shown on improving the omnidirectional viewing angle of a TN type LCD. In addition, JP-A-3-932
No. 6 and Japanese Patent Laid-Open No. 3-291601 disclose a plan to apply a polymer liquid crystal to a film-shaped substrate provided with an alignment film to form an optical compensator for LCD. Since it is impossible to orient the molecules obliquely, improvement of the omnidirectional viewing angle of the TN LCD cannot be expected.

Further, EP0576304A1 describes a method of improving viewing angle characteristics by using a retardation plate which exhibits optically negative uniaxiality and whose optical axis is inclined. Although this method certainly improves the viewing angle significantly compared to the conventional one, it was still impossible to improve the viewing angle to the extent that a CRT alternative is considered.

Therefore, the present inventors have filed Japanese Patent Application No. 5-1532.
In Japanese Patent Application No. 6-126521, an optical anisotropic element whose optical axis is negatively uniaxial and whose optical axis is inclined from the normal direction of the film is used as a retardation film. , An optically anisotropic element whose optical axis is optically negative and whose optical axis is inclined from the normal direction of the film, and optically negative uniaxially whose optical axis is in the normal direction of the film It has been found that the viewing angle characteristics of a liquid crystal display device having a TN type liquid crystal are remarkably improved by using both of the optically anisotropic elements as a retardation film.

In order to increase the front contrast of the liquid crystal display device and improve the viewing angle characteristic, the retardation film is installed between the liquid crystal cell and the polarizing plate. The polarizing plate used in the liquid crystal display device, as described below, stretched polyvinyl alcohol, on both sides of the polarizing element adsorbed iodine or dichroic dye, cellulose triacetate with almost no optical anisotropy. Attach protective film such as
It has improved heat resistance and moisture resistance. When the optical anisotropic element described above is further bonded to this polarizing plate as a retardation film to form an elliptically polarizing plate, which is further bonded to a liquid crystal cell to form a liquid crystal display device, not only the number of bonding steps increases, but also When the liquid crystal display is placed under high temperature or high humidity conditions, peeling failure occurs at the interface where the elliptically polarizing plates are bonded, bubbles are generated inside the elliptically polarizing plate, or wrinkles occur at the four corners of the elliptically polarizing plate. Occurrence of wrinkles or the like may occur, which causes a serious problem that the display quality of the liquid crystal display device is remarkably lowered.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an elliptical polarizing plate which can be produced at a low cost without peeling failure, foaming failure or wrinkling failure even under high temperature or high humidity conditions. Further, it is another object of the present invention to provide a liquid crystal display device which does not deteriorate in display quality even when placed under high temperature or high humidity conditions.

[0011]

Means for Solving the Problems The above problems are solved by (1) laminating at least a polarizing element and an optically anisotropic element (A) having an optically negative uniaxial property and an optical axis thereof in a normal direction of a film. Elliptically polarizing plate, TN type liquid crystal cell, and optically negative uniaxial optical axis of which is 5 ° to 50 ° from the normal direction of the film.
A liquid crystal display device having an optical anisotropic element (B) inclined. (2) Assuming that the principal refractive index in the film plane of the optically anisotropic element (A) is nx, ny, the principal refractive index in the thickness direction is nz, and the thickness of the film is d, the formula {(nx + ny) / 2− n
The retardation represented by z} × d is 10 nm to 200 nm, and the liquid crystal display device according to (1) above. (3) The angle of inclination of the optical anisotropic element (B) between the optical axis and the normal direction of the film is in the range of 10 ° to 40 °, and the main refractive index in the film plane of the optical anisotropic element (B). , N
x ′, ny ′, the main refractive index in the thickness direction is nz ′, and the thickness of the film is d ′, the formula {(nx ′ + ny ′) / 2
The retardation represented by −nz ′} × d ′ is 50
It is achieved by the liquid crystal display device according to the above (1) or (2), characterized in that the thickness is from 400 nm to 400 nm.

It is considered as follows that the elliptically polarizing plate of the present invention does not cause a peeling failure, a wrinkle failure, a wrinkle failure, etc. even if it is placed under a high temperature and high humidity condition. The normally used polarizing element is a film made of a hydrophilic polymer such as ethylene-vinyl acetate copolymer partially saponified polymer, partially formalized polyvinyl alcohol and polyvinyl alcohol, and then iodine or dichroic dye is drawn. It is an adsorbed product or a plastic film such as polyvinyl chloride treated to orient the polyene. In order to improve the heat resistance and moisture resistance of this polarizing element, conventionally, a film with small birefringence such as cellulose triacetate and small hygroscopicity or moisture permeability on both sides of the polarizing element is attached as a protective film. I've been told. In the liquid crystal display device of the present invention, as described above, by using the optical anisotropic element (A) used as the optical compensation film as the protective film of at least one of the polarizing elements, the number of films constituting the elliptically polarizing plate is increased. It is presumed that the reliability was improved under high temperature or high humidity conditions due to the decrease of

A preferred embodiment of the present invention will be described in detail below. The optically anisotropic element (A) used in the present invention, which is optically uniaxial and whose optical axis is in the normal direction of the film, has a light transmittance of 80% or more and at the same time,
Assuming that the main refractive index in the plane of the film is nx, ny, the main refractive index in the thickness direction is nz, and the thickness of the film is d, the relationship of the triaxial main refractive index satisfies nz <ny = nx,
The retardation represented by {(nx + ny) / 2-nz} × d is preferably 10 nm to 200 nm. However, the values of nx and ny do not have to be exactly equal,
Almost equal is enough. Specifically, | nx-ny
If | / | nx−nz | ≦ 0.2, there is no practical problem. The front retardation represented by | nx-ny | xd is preferably 50 nm or less, and more preferably 20 nm or less.

The optical anisotropic element (A) of the present invention is a material having a small intrinsic birefringence, which is sold under the trade names of Zeonex (Nippon Zeon), ARTON (Nippon Synthetic Rubber), Fujitac (Fuji Photo Film Co., Ltd.), etc. Alternatively, it is made by forming a material with a large intrinsic birefringence such as polycarbonate, polyarylate, polysulfone, polyethersulfone, etc. by solution casting, melt extrusion, etc., and stretching it in the longitudinal and transverse directions. You can do it.

In the present invention, the optical anisotropic element (A) is used as one protective film of the polarizing element, and the other one protective film is Zeonex or ARTO described above.
It is preferable to use a film commercially available under the trade name of N, Fujitac, or the like. These protective films are attached to the polarizing element with an acrylic, SBR, or silicone adhesive or adhesive to obtain the elliptically polarizing plate of the present invention. When the elliptically polarizing plate of the present invention is used in a TN liquid crystal cell, it is necessary that the optical anisotropic element (A) of the protective film of the elliptically polarizing plate faces the TN liquid crystal cell side. Further, an optically anisotropic element (B) having an optically negative uniaxial property and an optical axis of which is inclined by 5 ° to 50 ° from the normal direction of the film is provided between the elliptically polarizing plate and the liquid crystal cell. It is preferable to do.

The optically anisotropic element (B) of the present invention, which has an optically negative uniaxial property and its optical axis is inclined from the normal direction of the film by 5 ° to 50 °, has a light transmittance of 80%. In addition to the above, the main in-plane refractive indices are nx ′, ny ′,
When the refractive index in the thickness direction is nz 'and the thickness is d', the relationship of the triaxial main refractive indexes satisfies nz '<ny' = nx ', and the formula {(nx' + ny ') / 2-nz is satisfied. '} × d'
It is preferable that the retardation represented by is 50 nm to 400 nm. However, the values of nx ′ and ny ′ do not have to be exactly equal, and it is sufficient if they are almost equal. Specifically, there is no problem within the following range. | Nx'-ny '| / | nx'-nz' | ≦ 0.2 Further, the angle formed by the optical axis and the film normal direction is 1
More preferably, it is 0 ° to 40 °.

As a method for producing the optical anisotropic element (B) of the present invention, as described in Japanese Patent Application No. 6-126521, both sides of a film in which a discotic compound is oriented obliquely are described. Examples thereof include applying a shearing force to impart strain, or irradiating a photoisomerizable compound such as azobenzene with polarized light. The explanation will be given below.

A preferred embodiment is characterized in that the optically anisotropic element (B) contains an oriented discotic compound.
The discotic compound of the present invention is, for example, C.I. Destra
de et al., Mol. Cryst. 71 volumes, 11
Benzene derivatives described on page 1 (1981); Kohne et al., Angew. Che
m. Vol. 96, p. 70 (1984) and cyclohexane derivatives described in J. Am. M. Lehn et al.,
J. Chem. Commun. , P. 1794 (1985).
Year), J. Research report by Zhang et al. Am. Che
m. Soc. 116, pp. 2655 (1994), such as azacrown-based and phenylacetylene-based macrocycles. Generally, these are used as the mother nucleus of the molecular center, and straight-chain alkyl groups, alkoxy groups, and substituted It has a structure in which a benzoyloxy group or the like is linearly substituted as its straight chain, exhibits liquid crystallinity, and includes what is generally called discotic liquid crystal. However, the molecule is not limited to the above description as long as the molecule itself has negative uniaxiality and can give a certain orientation. Further, in the present invention, the term “formed from a discotic compound” does not necessarily mean that the final product is the compound, for example,
The low molecular weight discotic liquid crystal has a group that reacts with heat, light, etc., and as a result, the one that is polymerized or crosslinked by the reaction with heat, light, etc., has a high molecular weight and loses liquid crystallinity is also included. To do.

Next, the discotic compound in the present invention means the reaction of discotic liquid crystal as listed below, and the reaction of discotic liquid crystal which no longer exhibits liquid crystallinity due to reaction with other low molecular weight compounds and polymers. It means all compounds, such as products, in which the molecule itself has optically negative uniaxiality.

[0020]

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[0021]

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[0022]

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[0023]

[Chemical 4]

When the discotic compound in the present invention is a discotic liquid crystal, the layer containing them is oriented so as to have an optically negative uniaxial axis and an optical axis inclined from 5 ° to 50 ° from the normal direction of the film. The following processing is required for this. Specifically, a discotic liquid crystal is applied to a substrate on which a rubbing-treated organic alignment film or inorganic alignment film is formed, and then the temperature is raised to a liquid crystal phase, more preferably a disconematic phase formation temperature. As a result, the liquid crystal is obliquely aligned, and remains in the solid state at room temperature while maintaining the alignment by subsequent cooling. Further, the discotic nematic liquid crystal phase forming temperature is unique to the discotic liquid crystal, but can be arbitrarily adjusted by mixing two or more different types. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystal used in the present invention is preferably from 70 ° C to 300 ° C, particularly preferably from 70 ° C to 150 ° C.

The organic alignment film may be a polyimide film or polystyrene derivative, and the water-soluble film may be a gelatin film or polyvinyl alcohol. By subjecting all of them to rubbing treatment, the discotic liquid crystal can be oriented obliquely.
Of these, the alkyl-modified polyvinyl alcohol is particularly preferable, and the present inventors have discovered that it has an excellent ability to uniformly align the discotic liquid crystal. It is speculated that this is due to the strong interaction between the alkyl chains on the alignment film surface and the alkyl side chains of the discotic liquid crystal. The above alkyl-modified polyvinyl alcohol has an alkyl group at the terminal as listed below, and has a saponification degree of 80%.
As described above, the polymerization degree is preferably 200 or more. Further, polyvinyl alcohol having an alkyl group in a side chain can also be used effectively. As a commercial item, Kuraray MP103, M
P203, R1130, etc. are available.

Further, a polyimide film which is widely used as a liquid crystal alignment film of LCD is also preferable as the organic alignment film,
This is a polyamic acid (for example, LQ / L manufactured by Hitachi Chemical
X series, SE series manufactured by Nissan Chemical Co., Ltd.) is applied to the surface of the substrate, baked at 100 to 300 ° C. for 0.5 to 1 hour, and then rubbed. In addition, the rubbing treatment is the same method widely used as a liquid crystal alignment treatment process for LCDs, and the surface of the alignment film is made constant by using paper, gauze, felt, rubber, nylon, polyester fiber or the like. It is a method of obtaining orientation by rubbing in the direction. In general, rubbing is performed several times using a cloth or the like in which fibers of uniform length and thickness are evenly flocked.

Further, as a deposition material of the inorganic oblique deposition film, SiO is represented by a metal oxide such as TiO ₂ , MgF ₂ , ZnO ₂ , a fluoride, and a metal such as Au and Al.
The metal oxide can be used as the oblique vapor deposition material as long as it has a high dielectric constant, and is not limited to the above. Both a fixed substrate type method and a continuous vapor deposition type method on a film can be used to form a vapor deposition film.
For example, when the vapor deposition angle α is about 65 to 88 °, the discotic liquid crystal is uniformly aligned in a direction whose optical axis is substantially perpendicular to the direction of the vapor deposition particle column.

The above-mentioned alignment film has a function of determining the alignment direction of the discotic liquid crystal molecules coated thereon, but since the alignment property of the discotic liquid crystal depends on the alignment film, its combination is optimized. There is a need. Further, the uniformly aligned discotic liquid crystal molecules are aligned at an angle with the normal line of the film, but the tilt angle does not change much depending on the alignment film and often takes a value specific to the discotic liquid crystal molecules. When two or more discotic liquid crystals are mixed or a compound similar to the discotic liquid crystal is mixed, the tilt angle can be adjusted by the mixing ratio. Therefore, a method of selecting or mixing discotic liquid crystals is more effective for controlling the tilt angle of the oblique alignment.

Another method for orienting the discotic liquid crystal obliquely is magnetic field orientation or electric field orientation. In this case, it is necessary to apply a magnetic field or an electric field at a desired angle while heating the substrate coated with the discotic liquid crystal. ,

In order to maintain the oblique orientation of the discotic compound thus obtained even under high temperature and high humidity, a polymerizable unsaturated group, an epoxy group, a hydroxyl group and an amino group are previously added to the discotic compound. Groups, functional groups such as carboxyl groups, radical polymerization of polymerizable unsaturated groups by heat or photopolymerization initiator, ring-opening polymerization of epoxy groups by photoacid generator, polyvalent isocyanate, polyvalent It is preferable to crosslink the discotic compound itself by a crosslinking reaction with an epoxy compound. At this time, another compound having the same functional group may be contained.

The optically anisotropic element (B) in the present invention is
It can also be obtained by subjecting at least a step of applying a shearing force to both sides of the transparent film. Specifically, a film made of a thermoplastic resin and having a light-transmitting property is sandwiched between two rolls having different peripheral speeds, and a shearing force is applied to the film to efficiently obtain the film. The thermoplastic resin used here has no problem as long as it has a light transmittance of 70%, more preferably 85%, and is not particularly limited. Specifically, polycarbonate, polyarylate
, Polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyvinyl alcohol, polyamide,
Polyimide, polyolefin, polyvinyl chloride, cellulose polymer, polyacrylonitrile, polystyrene,
Various binary and ternary polymers, graft copolymers, blends and the like are preferably used.

Further, the optically anisotropic element (B) in the present invention can be obtained by irradiating a photoisomerizable substance with polarized light. Here, the photoisomerizable substance is one that causes stereoisomerization or structural isomerization by light, and is preferably one that causes its reverse isomerization by light or heat of another wavelength. Generally, as these compounds, those accompanied by a structural change and a change in color tone in the visible range are
Many are well known as photochromic compounds, azobenzene compounds, benzaldoxime compounds, azomethine compounds, fulgide compounds, diarylethene compounds, cinnamic acid compounds, retinal compounds,
A hemithioindigo compound etc. are mentioned.

It is presumed as follows that the viewing angle of the liquid crystal display device using the TN type liquid crystal cell was significantly improved by the elliptically polarizing plate and the optically anisotropic element (B) of the present invention. Many TN-LCDs employ a normally white mode. In this mode, the transmittance of light from the black display portion remarkably increases as the viewing angle increases, resulting in a sharp decrease in contrast. The black display is the state when a voltage is applied. At this time, the liquid crystal molecules in the TN type liquid crystal cell are shown in FIG.
They are lined up like the model shown in. When the arrangement of the liquid crystal molecules is approximated by an optically positive uniaxial index ellipsoid, FIG.
As shown in (b), the TN liquid crystal cell includes two positive uniaxial optical anisotropic bodies whose optical axes are tilted from the normal direction of the cell and positive uniaxial optical anisotropic bodies whose optical axes are in the normal direction. It can be thought of as a stack of four cubes, two cubes.

If the liquid crystal cell can be regarded as a laminated body of four positive uniaxial optically anisotropic bodies, in order to compensate for it,
It is preferable to use four negative uniaxial optically anisotropic bodies which have the same combination of optical axis tilt angles as the laminated body. In the case of the present invention, the optical anisotropic element (A) is a negative uniaxial optical anisotropic body having an optical axis in the normal direction of the cell, and a negative optical anisotropic body having an optical axis inclined from the normal direction of the cell. The optical anisotropic element (B) acts as a cube. For these reasons, it is presumed that the present invention has realized a significant improvement in viewing angle characteristics.

The present invention will be described in detail below based on examples. Example 1 Preparation of Optically Anisotropic Elements A1 and A2 Triacetyl cellulose having a styrene-equivalent weight average molecular weight of 130,000 was dissolved in methylene chloride, cast on a metal band, and peeled when the volatile content reached 4%. After that, by performing widthwise stretching with a tenter, MD direction stretching, and relaxation of orientation by heat, optical anisotropic elements A1 and A2 having different retardations described above were prepared.

Example 2 Preparation of Optically Anisotropic Element B1 A 54 μm thick polycarbonate film (Iupilon;
Mitsubishi Gas Chemical Co., Ltd.) was passed through a pair of different peripheral speed rolling rollers (speed ratio 1: 1.005) heated to 132 ° C., and then stretched in the transverse direction to optically irradiate the light with negative uniaxiality. An optical anisotropic element B1 having an axis inclined from the normal direction of the film was prepared.

Example 3 Preparation of Optically Anisotropic Elements B2 and B3 Using A1 prepared in Example 1 as a support, an alkyl-modified PVA (MP203: trade name, manufactured by Kuraray) of 0.5 μm
Of the above-mentioned discotic liquid crystal TE-8 (m =
4) 0.4 g, 0.04 g of trimethylolpropane triacrylate, and Irgacure 9070.004 g dissolved in 1.6 g of methyl ethyl ketone were applied with a spin coater (rotation speed 1700 rpm / 3 minutes).
After drying, the temperature is raised from room temperature to 150 ° C. in 8 minutes to heat the discotic liquid crystal to align it, and then UV irradiation is performed at 150 ° C. for 1.5 minutes using a high pressure mercury lamp, and then slowly cooled to room temperature. Thus, an optical anisotropic element B2 having a layer D1 containing a discotic compound was prepared. A disk-shaped compound was prepared in exactly the same manner as B2 except that the spin coater was rotated at 2000 rpm, the temperature was raised from room temperature to 155 ° C. for 6 minutes after drying, and UV irradiation was performed for 3 minutes at 155 ° C. using a high pressure mercury lamp. An optical anisotropic element B3 having a layer D2 containing was prepared.

Example 4 Light of Optically Anisotropic Elements A0, A1, A2, B1, B2, B3
Optically anisotropic element prepared from the academic characterization Example 1 in 3 A1, A2, B
For 1 and A0 described below, after measuring the film thickness of the film with a film thickness meter, using an ellipsometer, the retardation value described above and the tilt angle formed by the optical axis and the normal direction of the film were obtained. Are summarized in Table 1. For the optically anisotropic elements B2 and B3, the optical characteristics of the support and the coating layer containing the discotic compound were determined separately, and the optical characteristics of the coating layers D1 and D2 are summarized in Table 2.

[0039]

[Table 1]

[0040]

[Table 2]

Example 5 Production of Polarizing Plate P0 and Elliptic Polarizing Plates P1 and P2 An acrylic adhesive was used on both sides of the polarizing element S1 in which iodine was adsorbed to stretched polyvinyl alcohol.
Film A0 (ARTO with 0 μm thickness and no optical anisotropy
N: trade name, made of Japan Synthetic Rubber) was laminated as a protective film to prepare a polarizing plate P0. As the protective film, the optical anisotropic elements A1 and A2 prepared in Example 1 are
Elliptic polarizing plates P1 and P2 of the present invention were prepared in exactly the same manner as in the case of P0 except that it was used instead of 0.

Example 6 Preparation of liquid crystal display devices H1 to H4 TN having a product of the difference in refractive index between the extraordinary light and ordinary light of the liquid crystal and the gap size of the liquid crystal cell is 485 nm and the twist angle is 89 °.
The elliptically polarizing plate P1 of the present invention and the optical anisotropic element B1 were attached to both sides of the liquid crystal cell of the type in the arrangement shown in FIG. 2 to produce a normally white liquid crystal display device H1 of the present invention. Similarly, the liquid crystal display devices H3 and H4 of the present invention and the liquid crystal display device H2 of the comparative example were prepared in the arrangement shown in FIG. In the production of a liquid crystal display device, the projection direction onto the film surface, which is the direction in which the optical axis or retardation of the optical anisotropic elements B1, B2, B3 takes a minimum value, is 180 ° with respect to the rubbing axis of the adjacent liquid crystal cell, The adjacent polarizing plates or the elliptically polarizing plates were arranged so as to form an angle of 90 ° with the absorption axis.

Example 7 Evaluation of Liquid Crystal Display Devices H1 to H4 For the liquid crystal display devices H1 to H4 prepared in Example 6, a 36 Hz rectangular wave of 0 V to 5 V was applied to a liquid crystal cell.
By applying a voltage in the range of, the angle dependence of the transmittance (T) is
It was measured with LCD-5000 manufactured by Otsuka Electronics. The position where the contrast ratio (T0 / T5) of white display and black display is 10 is defined as the viewing angle, the viewing angle in the vertical and horizontal directions is obtained, and the results are summarized in Table 3.

[0044]

[Table 3]

[0045]

As is apparent from FIG. 2, in the liquid crystal display device H2 of the comparative example, a total of six polarizing plates P0 and optical anisotropic elements A1 and B1 are attached to the liquid crystal cell from both sides. . In contrast, the liquid crystal display device H of the present invention
1, H3 and H4 are liquid crystal cells and elliptically polarizing plates P1 and P2.
Further, a total of four optical anisotropic elements B1, B2 or B3 are attached from both sides, and the attaching step is ⅔. As shown in Table 3, the viewing angles are the same as those of the comparative example and the liquid crystal display device of the present invention,
Both the left and right sides were good at about 100 °, but the maximum contrast of the liquid crystal display device H2 of the comparative example was 100 or less. Then, these liquid crystal display devices were alternately placed in a constant temperature bath at 60 ° C. and a total humidity of 10% and 60% at intervals of 12 hours, and visually observed after 120 hours. Peeling occurred at the interface between the polarizing plate P0 and the optically anisotropic element A1 in the corner of the part. Also, fine wrinkles were generated on the edges, but in the book, the liquid crystal display devices H1, H3, and H4 of the place name did not show such a failure at all. Therefore, according to the present invention, it is possible to obtain a liquid crystal display device having a small number of bonding steps, a wide viewing angle, and no failure even under constant temperature and high humidity conditions.

[Brief description of drawings]

FIG. 1 is a model view showing an arrangement of liquid crystal molecules of a TN liquid crystal cell.

FIG. 2 is a diagram showing a configuration of a liquid crystal display device created in Example 6.

[Explanation of symbols]

A0: Optically isotropic film made of ARTON A1, A2: Optical anisotropic element made of cellulose triacetate B1: Optical anisotropic element made of polycarbonate B2, B3: Layer D1 or D2 containing a discotic compound on A1 Optical anisotropic element having P0: Polarizing plate P1, P2: Elliptical polarizing plate S1: Polarizing element LC: TN type liquid crystal cell BL: Backlight

Claims (3)

[Claims] 1. An elliptically polarizing plate in which at least a polarizing element and an optically anisotropic element (A) having optically negative uniaxiality and whose optical axis is in the normal direction of the film are laminated, a TN type liquid crystal cell, and Optically anisotropic element (B) which is optically uniaxial and has its optical axis inclined 5 ° to 50 ° from the normal direction of the film.
A liquid crystal display device comprising: 2. The principal refractive index in the film plane of the optically anisotropic element (A) is nx, ny, the principal refractive index in the thickness direction is nz,
Assuming that the film thickness is d, the formula {(nx + ny) /
The retardation represented by 2-nz} × d is 10n
The liquid crystal display device according to claim 1, wherein the thickness is from m to 200 nm. 3. The optical anisotropic element (B) has an inclination angle between the optical axis and the normal direction of the film in the range of 10 ° to 40 °, and a main surface in the film plane of the optical anisotropic element. Assuming that the refractive index is nx ′, ny ′, the main refractive index in the thickness direction is nz ′, and the film thickness is d ′, the formula {(nx ′ + n
The liquid crystal display device according to claim 1, wherein the retardation represented by y ′) / 2-nz ′} × d ′ is 50 nm to 400 nm.