JPH0720456A - Liquid crystal display element using optical anisotropic element - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display element with high quality display of superior visibility by improving visual angle characteristics of a TN type liquid crystal display element. CONSTITUTION:The liquid crystal display element is constituted by arranging a liquid crystal cell CE formed by sandwiching TN type liquid crystal whose twist angle is almost 90 deg. between two electrode substrates, two polarizing elements A and B arranged on both its sides, and 12 optical anisotropic elements 1 and 2 across the liquid crystal cell CE between the two polarizing elements A and B; and the optical anisotropic elements 1 and 2 have negative uniaxiality and the optical axes of the optical anisotropic elements 1 and 2 slant at 5-60 deg. to the normal direction to the liquid crystal cell surface. Further, the angle between the direction where the optical axes of the optical anisotropic elements 1 and 2 on both the sides of the liquid crystal cell are positively projected on the liquid crystal cell surface and the rubbing axis direction of a nearby liquid crystal cell substrate is -45 to 45 deg. and the directions where the optical axes of the two optical anisotropic elements 1 and 2 are positively projected on the liquid crystal cell surface is 0-90 deg..

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 having improved display contrast and viewing angle characteristics of display color.

[0002]

2. Description of the Related Art CRTs, which are the mainstream of display devices for OA equipment such as Japanese word processors and desktop personal computers
Have been converted into liquid crystal display elements which have the great advantages of thinness, light weight, and low power consumption. Most of the liquid crystal display elements (hereinafter, referred to as LCDs) that are currently popular 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.

An LCD using a birefringence mode has a twisted angle of 90 ° or more in the alignment of liquid crystal molecules and has steep electro-optical characteristics, so that it has a simple matrix shape without active elements (thin film transistors or diodes). Even with the above electrode structure, a large capacity display can be obtained by time-division driving. However, the response speed is slow (hundreds of milliseconds) and gray scale display is difficult, and a liquid crystal display element (TFT-L) using an active element is used.
The display performance of CDs, MIM-LCDs, etc.) is exceeded.

For the TFT-LCD and MIM-LCD, there is used a display system (TN type liquid crystal display element) of optical rotation mode in which the alignment state of liquid crystal molecules is twisted by 90 °. 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. However, since the twisted nematic liquid crystal is used, there is a problem in the viewing angle characteristics that the display color and the display contrast change depending on the viewing direction due to the principle of the display system.
The display performance of is not reached.

JP-A-4-229828 and JP-A-4-25
As disclosed in 8923 and the like, a method has been proposed in which a retardation film is arranged between a pair of polarizing plates and a TN liquid crystal cell to increase the viewing angle.

The retardation film proposed in the above patent publication has a retardation of almost zero in the direction perpendicular to the surface of the liquid crystal cell, has no optical action from the front, and is tilted. When the liquid crystal cell has a retardation, the retardation is manifested in the liquid crystal cell. However, even with these methods, the viewing angle of LCD is still insufficient, and further improvement is desired. In particular, when considered as a vehicle-mounted type or as a substitute for a CRT, the current viewing angle cannot cope with the situation.

It is generally known that liquid crystal molecules have different refractive indexes in the major axis direction and the minor axis direction of the liquid crystal molecules. When polarized light enters liquid crystal molecules exhibiting such anisotropy of refractive index, the polarized state of the polarized light changes depending on the angle of the liquid crystal molecules. The molecular arrangement of the liquid crystal cell of the twisted nematic liquid crystal has a structure in which the arrangement of the liquid crystal molecules is twisted in the thickness direction of the liquid crystal cell. The light is sequentially polarized and propagates depending on the orientation of the liquid crystal molecules. Therefore, the polarization state of the light propagating in the liquid crystal cell is different between the case where the light is vertically incident on the liquid crystal cell and the case where the light is obliquely incident, and as a result, the display pattern cannot be seen at all depending on the viewing direction. Appears as a phenomenon, which is not preferable for practical use.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device having improved display contrast and viewing angle characteristics of display color in a TN liquid crystal cell without lowering front contrast. Is.

[0009]

A liquid crystal display device of the present invention which achieves the above object is a liquid crystal cell in which a TN type liquid crystal having a twist angle of about 90 ° is sandwiched between two electrode substrates, and both sides thereof. In a liquid crystal display element in which two polarizing elements arranged in 1 and two or more optical anisotropic elements are arranged between the two polarizing elements, the optical anisotropic element exhibits negative uniaxiality, It is characterized in that the optical axis of the optically anisotropic element is tilted by 5 ° to 60 ° from the direction normal to the surface of the liquid crystal cell.

Another liquid crystal display element of the present invention is a liquid crystal cell in which a TN type liquid crystal having a twist angle of about 90 ° is sandwiched between two electrode substrates, and two polarization plates arranged on both sides thereof. In a liquid crystal display element in which two or more optical anisotropic elements are arranged between the element and the two polarizing elements, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is 5 ° to 60 ° from the normal direction to the liquid crystal cell surface,
It is characterized in that the directions in which the optical axes of the respective optical anisotropic elements are orthogonally projected on the surface of the liquid crystal cell are different from each other.

In these cases, a concrete first liquid crystal display element is a TN having a twist angle of about 90 ° between two electrode substrates.
A liquid crystal cell sandwiching a type liquid crystal, two polarizing elements arranged on both sides of the liquid crystal cell, and two liquid crystal cells between the liquid crystal cell and the polarizing element.
In a liquid crystal display element in which a plurality of optical anisotropic elements are arranged with a liquid crystal cell sandwiched therebetween, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is 5 from the direction normal to the surface of the liquid crystal cell. The angle between the liquid crystal cell and the direction in which the optical axes of the optical anisotropic elements on both sides of the liquid crystal cell are orthographically projected on the surface of the liquid crystal cell and the rubbing axis direction of the adjacent liquid crystal cell substrate are −45 ° or more. The angle is 45 ° or less, and the angle formed by the directions in which the optical axes of the two optical anisotropic elements are orthographically projected on the surface of the liquid crystal cell is 0 ° or more and 90 ° or less.

Further, in these concrete second liquid crystal display elements, a TN having a twist angle of about 90 ° between the two electrode substrates.
A liquid crystal cell sandwiching a type liquid crystal, two polarizing elements disposed on both sides of the liquid crystal cell, and between the liquid crystal cell and the polarizing element,
In a liquid crystal display element in which two or more optical anisotropic elements are laminated and arranged, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is 5 from the direction normal to the liquid crystal cell surface. Between the direction in which the optical axis of the optical anisotropic element that is closest to the liquid crystal cell and is orthographically projected onto the surface of the liquid crystal cell and the rubbing direction of the liquid crystal cell substrate that is closer to the optical anisotropic element. The angle between -45 ° and 45 ° inclusive, the direction in which the optical axis of the optical anisotropic element farthest from the liquid crystal cell is orthographically projected onto the liquid crystal cell surface and the rubbing of the liquid crystal cell substrate farther from the optical anisotropic element. The angle between the directions is -45 ° or more and 45 °
The following are the direction in which the optical axis of the optical anisotropic element closest to the liquid crystal cell is orthographically projected onto the liquid crystal cell surface, and the direction in which the optical axis of the optical anisotropic element farthest from the liquid crystal cell is orthogonally projected onto the liquid crystal cell surface. The angle formed by is 0 ° or more and 90 ° or less.

In the above, the optical anisotropic element 632.8.
Retardation in nm light is -50 nm to -6
It is preferably 00 nm.

[0014]

The function of the present invention will be described below with reference to the TN type liquid crystal display device using the drawings as an example. FIGS. 1, 2 and 3 show polarization states of light propagating in a liquid crystal display element when a voltage higher than a threshold voltage is applied to the liquid crystal cell. It sometimes shows a bright state.

FIG. 2 is a diagram showing a polarization state of light when light is vertically incident on the liquid crystal cell CE. When the natural light L0 is vertically incident on the polarizing plate A having the polarization axis PA, the light transmitted through the polarizing plate A becomes the linearly polarized light L1. LC in the figure
FIG. 3 is a schematic diagram showing the alignment state of the liquid crystal molecules in the liquid crystal cell CE when a sufficient voltage is applied to the TN liquid crystal cell CE, using one liquid crystal molecule model. When the molecular long axis of the liquid crystal molecule LC in the liquid crystal cell CE is parallel to the light path PS, there is no difference in the refractive index in the plane perpendicular to the light path PS, so that the normal light propagating in the liquid crystal cell CE is not affected. There is no phase difference between the extraordinary rays, and the linearly polarized light L1 propagates as it is after passing through the liquid crystal cell CE. When the polarization axis PB of the polarization plate B is set to be perpendicular to the polarization axis PA of the polarization plate A, the light L2 that has passed through the liquid crystal cell CE cannot pass through the polarization plate B and is in a dark state.

FIG. 3 is a diagram showing a polarization state of light when the light L0 obliquely enters the liquid crystal cell CE. When the natural light L0 of the incident light is obliquely incident, the polarized light L1 transmitted through the polarizing plate A becomes almost linearly polarized light (in the actual case, due to the characteristics of the polarizing plate A, it becomes elliptically polarized light). In this case, since the molecular long axis of the liquid crystal molecules LC in the liquid crystal cell CE makes an angle with the light path PS, a difference in refractive index occurs in a plane perpendicular to the light path PS, and light transmitted through the liquid crystal cell CE is generated. L2 becomes elliptically polarized light, reaches the polarizing plate B, and part of the light passes through the polarizing plate B. The transmission of light in such oblique incidence causes a reduction in the contrast of the liquid crystal display element, which is not preferable.

In order to prevent such a decrease in contrast at oblique incidence, improve viewing angle characteristics, and at the same time improve front contrast, in the present invention, as shown in FIG. 1, a polarizing plate B and a liquid crystal are used. The laminated body RF of the optically anisotropic element of the present invention is arranged between the cell CE and the cell CE. The laminated body RF of the optical anisotropic elements has a function similar to that of a birefringent body which shows a larger phase difference as the angle at which light is incident on the optical axis increases in pairs. Similarly to the case of FIG. 3, the elliptically polarized light L2 which is obliquely incident on the liquid crystal display element having such a structure and is transmitted through the liquid crystal cell CE has a phase delay when transmitted through the laminated body RF of the optically anisotropic elements. By the action, the elliptically polarized light is modulated to the original linearly polarized light, and a good liquid crystal display element having the same transmittance even at various oblique incidences and having no viewing angle dependence can be realized.

Instead of this, in the present invention, two optical anisotropic elements are sandwiched between the polarizing plate A and the liquid crystal cell CE and between the liquid crystal cell CE and the polarizing plate B to sandwich the liquid crystal cell CE. By arranging them, a good liquid crystal display device having the same principle and having the same transmittance even at various oblique incidences and having no viewing angle dependency was realized.

The reason why the viewing angle characteristics of the liquid crystal display device can be greatly improved by the present invention is considered as follows. Most TN-LCDs adopt a normal white mode. In this mode, the transmittance of light from the black display portion remarkably increases as the viewing angle is increased, resulting in a sharp decrease in contrast.

The black display is the state when a voltage is applied. At this time, the TN cell can be regarded as a positive uniaxial optical anisotropic body in which the optical axis is slightly tilted from the direction normal to the surface of the cell. . This slight tilt of the optical axis not only causes birefringence even in front of the cell, but also causes a remarkable asymmetry of the viewing angle in the vertical direction of the cell, that is, in the main viewing angle direction (direction where the twist angle of the liquid crystal molecules is approximately 45 °), which causes The viewing angle in either one or both directions will be significantly impaired. This is in agreement with the actual phenomenon.

When the optical axis of the liquid crystal cell is tilted from the direction normal to the surface of the liquid crystal cell, it is expected that the optical anisotropic body having the optical axis in the normal direction will be insufficiently compensated. Further, if the liquid crystal cell can be regarded as a positive optical anisotropic body, it must be a negative uniaxial optical anisotropic body to compensate for it. For these reasons, it is considered that the viewing angle characteristics are significantly improved by the negative uniaxial optical anisotropic body in which the optical axis in the present invention is inclined from the normal direction (FIG. 4). It is not sufficient to use only one uniaxial optically anisotropic element. Because the TN type liquid crystal cell actually has almost 90 liquid crystal molecules.
Since it is twisted, it is not a simple positive optical anisotropic body as shown in FIG. In order to compensate for this twist, it is preferable to use not one optical anisotropic element but two or more optical anisotropic elements with mutually different optical axis angles. These optical anisotropic elements may be arranged on both sides so as to sandwich the liquid crystal cell CE as described above, or may be laminated on one side of the liquid crystal cell CE as shown in FIG. Good.

For example, when two or more optical anisotropic elements are used so as to sandwich a liquid crystal cell, the relationship between the optical anisotropic element and liquid crystal molecules near the liquid crystal cell substrate closer to the optical anisotropic element is shown in FIG. By arranging so that the relationship between the liquid crystal molecules near the liquid crystal cell substrate near the other is close to the relationship shown in FIG. The positive birefringence and twist of the liquid crystal molecules in the cell are compensated (first form of the invention).

When two or more optical anisotropic elements are used on one side of the liquid crystal cell, the optical anisotropic element closest to the liquid crystal cell and the liquid crystal cell substrate nearer the optical anisotropic element are provided. The optical anisotropic element located farthest from the liquid crystal cell and the liquid crystal molecules near the liquid crystal cell substrate located farthest from the liquid crystal cell are arranged so that the relationship with the liquid crystal molecules is close to the relationship shown in FIG. The positive birefringence and twist of the liquid crystal molecules in the liquid crystal cell are compensated by arranging so as to be close to the relationship shown in FIG. 4 (second mode of the present invention). FIG. 5 schematically shows the refractive index of one optical anisotropic element used in the present invention. The optical axis of each optically anisotropic element in the present invention is preferably inclined 5 ° to 60 ° from the normal direction of the surface of the liquid crystal cell. Furthermore, it is preferable to incline 10 ° to 40 °.

In the first embodiment of the present invention, as shown in FIG. 6, two or more optical anisotropic elements are used with the liquid crystal cell CE interposed therebetween. The direction in which the optical axis of the optically anisotropic element is orthographically projected on the surface of the liquid crystal cell CE means the direction of the vector OR ′ obtained by orthographically projecting the optical axis OR on the plane π parallel to the surface of the liquid crystal cell as shown in FIG. Say that. FIG. 8 shows the relationship between the rubbing axis of both substrates and the direction in which the optical axes of the two optically anisotropic elements are orthographically projected onto the surface of the liquid crystal cell. FIG. 8 shows an axial configuration when viewed from the light source side in a direction perpendicular to the liquid crystal cell. The angle β formed between the direction in which the optical axis of the optically anisotropic element 1 is orthographically projected on the surface of the liquid crystal cell and the rubbing axis direction of the liquid crystal cell substrate on the light source side, which is the liquid crystal cell substrate close to the optically anisotropic element 1, is shown in FIG. Define as follows. In addition, the direction in which the optical axis of the optical anisotropic element 2 is orthographically projected on the surface of the liquid crystal cell and the rubbing axis direction of the liquid crystal cell substrate on the front side (display side) which is the liquid crystal cell substrate close to the optical anisotropic element 2 The angle α is defined as shown in FIG. Then, in FIG. 8, both α and β are positive.
Then, an angle γ formed between the directions in which the optical axes of the two optically anisotropic elements are orthographically projected on the surface of the liquid crystal cell is defined as shown in FIG. In the first embodiment of the present invention, both α and β are -45.
It is preferably in the range of ° to 45 °. Also, -10
More preferably, it is in the range of ° to 45 °. Further, it is preferably in the range of -10 ° to 25 °.

In FIG. 8, the arrows in the directions orthogonal to the liquid crystal cell surface of the optical axis of each optical anisotropic element are substantially opposite to the arrows in the rubbing direction of the corresponding substrate. This is because the projection is performed on the opposite surface of each substrate.

The angle γ formed by the directions of the orthogonal projections of the optical axes of the optically anisotropic elements on both sides of the liquid crystal cell on the surface of the liquid crystal cell is 0.
It is preferably in the range of 90 ° to 90 °. Further, the direction of a straight line that bisects the angle formed by the directions of the orthogonal projections of the optical axes of the optically anisotropic elements on both sides of the liquid crystal cell is equal to the main viewing angle direction of the liquid crystal cell, that is, the twist angle of the liquid crystal molecules. °
It is preferable that the direction is substantially equal to the direction. That is, α and β
Are preferably approximately equal.

Further, in the second aspect of the present invention,
As shown in FIG. 9, two or more optical anisotropic elements are laminated and used. The angle formed between the direction in which the optical axis of the optical anisotropic element closest to the liquid crystal cell CE is orthographically projected on the liquid crystal cell surface and the rubbing direction of the liquid crystal cell substrate closer to the optical anisotropic element is -45.
The angle is preferably in the range of ° to 45 °, and the direction in which the optical axis of the optical anisotropic element farthest from the liquid crystal cell CE is orthographically projected onto the surface of the liquid crystal cell and the rubbing direction of the liquid crystal cell substrate farther from the optical anisotropic element. The angle formed is -45 ° to 45 ° as described below.
Is preferred.

As shown in FIG. 9, in the second embodiment of the present invention, two or more optical anisotropic elements are laminated and used.
In FIG. 9, two optically anisotropic elements are laminated on the front side (display side) with respect to the liquid crystal cell CE, but in the present invention, they may be laminated on the light source side, or more than two layers may be laminated. May be.

FIG. 10 shows the relationship between the rubbing axis and the direction in which the optical axis of the optically anisotropic element is orthographically projected on the surface of the liquid crystal cell. FIG. 10 shows an axial configuration when viewed from the light source side in a direction perpendicular to the liquid crystal cell. The angle α formed between the direction in which the optical axis of the optical anisotropic element 1 closest to the liquid crystal cell is orthogonally projected on the surface of the liquid crystal cell and the rubbing direction of the liquid crystal cell substrate closer to the optical anisotropic element is defined as shown in FIG. To do. Further, as shown in FIG. 10, an angle β formed between a direction in which the optical axis of the optical anisotropic element 2 farthest from the liquid crystal cell is orthographically projected on the surface of the liquid crystal cell and a liquid crystal cell substrate rubbing direction farther from the optical anisotropic element is as shown in FIG. Define. And
In FIG. 10, both α and β are positive. Further, an angle γ formed by the directions in which the optical axes of the two optically anisotropic elements are orthographically projected on the surface of the liquid crystal cell is defined as shown in FIG.
In the present invention, both α and β are preferably in the range of −45 ° to 45 °. Further, it is more preferably in the range of −10 ° to 45 °. Furthermore, -10 ° to 25
It is preferably in the range of °.

In FIG. 10, the arrow in the direction orthogonal to the liquid crystal cell surface of the optical axis of the optical anisotropic element 1 is substantially opposite to the arrow in the rubbing direction of the substrate on the front side. This is because the projection is performed on the surface opposite to the front substrate.

The angle γ formed by the optical anisotropic element 1 and the optical anisotropic element 2 is preferably in the range of 0 ° to 90 °.
Further, it is preferable that the direction of a straight line that divides γ into two equal approximately to the main viewing angle direction of the liquid crystal cell, that is, the direction where the twist angle of the liquid crystal molecules is 45 °. That is, it is preferable that α and β are substantially equal.

In the first embodiment of the present invention described above, that is, when the optically anisotropic element is arranged so as to sandwich the liquid crystal cell CE,
When using three or more optical anisotropic elements, when the outermost optical anisotropic element is the optical anisotropic element 1 or the optical anisotropic element 2, between the optical anisotropic element 1 or 2 and the liquid crystal cell CE. It is preferable that the angle between the optically anisotropic element in 1) and the rubbing direction of the adjacent liquid crystal cell substrate is smaller than β or α. Further, it is preferable that the laminated body of the optically anisotropic elements is arranged so that the optical axis continuously changes.

In the second embodiment of the present invention, that is, when the optical anisotropic element is arranged close to one side of the liquid crystal cell CE and three or more optical anisotropic elements are used, the liquid crystal cell C is used.
The optical anisotropic element on the side closest to E and the optical anisotropic element on the side closest to the liquid crystal cell CE have an optical axis tilt direction of the optical anisotropic element between the optical anisotropic element on the side farthest from the liquid crystal cell CE. It is preferable to arrange so as to continuously change between the inclination direction of the optical axis of the element and the inclination direction of the optical axis of the optical anisotropic element farthest from the liquid crystal cell CE.

The retardation in the present invention means that the principal refractive index of the optically anisotropic element with respect to light having a wavelength of 632.8 nm is nx, ny, nz (nx = ny), and the thickness of the optically anisotropic element is d. Then, (nz-nx) * d.

The retardation in the light of 632.8 nm per optical anisotropic element showing negative uniaxiality is -5.
It is preferably 0 nm to -600 nm. Further, it is preferably -50 nm to -400 nm.
The optically anisotropic element in the present invention is preferably provided as a polymer film or a plate-like material, and the light transmittance of the optically anisotropic element is preferably 80% or more, more preferably 90% or more.

The polymer material used in the optical anisotropic element of the present invention is not particularly limited, but it is not limited to polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone. , Polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic polymer, polyacrylonitrile, polystyrene, polymethylmethacrylate, product name Zeonex 280, which is a polyolefin material manufactured by Nippon Zeon Co., Ltd.
Binary type, ternary type, various polymers, graft copolymers, blends and the like are preferably used. Further, a sheet in which a low molecular liquid crystal having positive or negative intrinsic birefringence is dispersed in a polymer matrix may be used.

[0037]

The present invention will be described in detail below with reference to examples. Example 1 is a liquid crystal display element of the first aspect of the present invention, and Example 2 is a liquid crystal display element of the second aspect of the present invention.

Example 1 Polycarbonate having a molecular weight of 120,000 obtained by condensation of phosgene and bisphenol A was dissolved in methylene dichloride to prepare an 18% solution. This was cast on a steel drum and continuously stripped and dried to obtain a film having a thickness of 60 μm. When the retardation value at a wavelength of 632.8 nm was measured with an ellipsometer AEP-100 manufactured by Shimadzu Corporation, this film was 85 nm. This is probably due to the tension when the film was stripped off the steel drum.

When the film was heat-relaxed for 1 hour in an atmosphere of 190 °, the retardation value became almost zero. This film was biaxially stretched under a stretching condition of 180 ° to prepare a film in which the retardation from the normal direction of the film was almost 0 and nx = ny> nz.

This film is divided into two 19 films with different peripheral speeds.
Rolling was carried out between metal rolls heated to 0 ° C., and a film having an optical axis inclined by 20 ° with respect to the normal line direction of the film plane was prepared. The prepared sample was manufactured by Shimadzu Corporation using an ellipsometer AEP-100, and nx, ny, nz were used.
Was measured. Assuming that the thickness of the sample is d, (nz-
nx) × d was used as the retardation in the thickness direction. The retardation of the film was -300 nm. It was also confirmed that nx = ny.

The birefringence is 0.110 between the pair of polarizing elements.
3. The nematic liquid crystal with a twist angle of 90 ° and a thickness of 4.
Between the liquid crystal cell sandwiched by the gap size of 5 μm and the polarizing element, two optical anisotropic elements were mounted as shown in FIG. FIG. 8 shows an axial configuration as viewed from the light source side in a direction perpendicular to the liquid crystal cell. The angle between the rubbing direction of the liquid crystal cell substrate away from the light source and the direction of the optical axis of the optical anisotropic element 2 orthogonally projected on the liquid crystal cell surface is α, and the rubbing direction of the liquid crystal cell substrate on the light source side is optically different from the rubbing direction. The angle formed by the optical axis of the rectangular element 1 and the direction orthogonally projected on the surface of the liquid crystal cell is β. LCD-manufactured by Otsuka Electronics Co., Ltd. when α and β are set as shown in Table 1 and when no optical anisotropic element is mounted.
0V / 5V (white / black) contrast at 5000 10
The reference viewing angle in all directions was measured. The results are shown in Figs.
13 shows.

[0042] 11 to 13 that Example B, which is the first mode of the present invention, has excellent viewing angle characteristics.

Example 2 Using the same optical anisotropic element as that used in Example 1, a nematic liquid crystal having a birefringence of 0.110 was twisted between a pair of polarizing elements at a twist angle of 90 ° and a thickness of Two optical anisotropic elements were mounted between the liquid crystal cell sandwiched by a gap size of 4.5 μm and the polarizing element as shown in FIG. FIG. 10 shows the axial configuration when viewed from the direction perpendicular to the liquid crystal cell from the light source side. The angle between the rubbing direction of the liquid crystal cell substrate away from the light source and the direction of the optical axis of the optically anisotropic element 1 orthogonally projected on the liquid crystal cell surface is α, and the rubbing direction of the liquid crystal substrate on the light source side is optically different from the rubbing direction. The angle formed by the optical axis of the rectangular element 2 and the direction orthogonally projected on the surface of the liquid crystal cell is β. Table 2 for α and β
0 V on Otsuka Electronics Co., Ltd. LCD-5000 in the case of not doing so and when not mounting the optical anisotropic element.
The viewing angle in all directions based on a 10V (white / black) contrast of / 5 V was measured. The results are shown in FIGS. 11 and 14 to 15.

[0044] It can be seen from FIGS. 11 and 14 to 15 that Example D, which is the second mode of the present invention, has excellent viewing angle characteristics.

[0045]

According to the present invention, it is possible to provide a liquid crystal display device of high quality display in which the viewing angle characteristics of the TN type liquid crystal display device are improved and the visibility is excellent. In addition, the present invention
It goes without saying that even when applied to an active matrix liquid crystal display element using a 3-terminal or 2-terminal element such as FT or MIM, excellent effects can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating one mode of a liquid crystal display element of the present invention.

FIG. 2 is a diagram illustrating a configuration of a conventional TN type liquid crystal display element and a diagram for explaining a light transmission state when light is perpendicularly incident on a display surface.

FIG. 3 is a diagram illustrating a configuration of a conventional TN type liquid crystal display element and a light transmission state when light obliquely enters a display surface.

FIG. 4 is a schematic diagram showing the principle of improving the viewing angle characteristics according to the present invention.

FIG. 5 is a diagram illustrating the main refractive index of the optically anisotropic element used in the present invention.

FIG. 6 is a diagram illustrating a first mode of the configuration of the liquid crystal display element of the present invention.

FIG. 7 is a diagram illustrating a direction in which the optical axis of an optically anisotropic element is orthographically projected on the surface of a liquid crystal cell.

FIG. 8 is a diagram illustrating an axial configuration when viewed from a direction perpendicular to a liquid crystal cell from the light source side of the first embodiment.

FIG. 9 is a diagram illustrating a second mode of the configuration of the liquid crystal display element of the present invention.

FIG. 10 is a diagram illustrating an axial configuration of the second embodiment viewed from the light source side in a direction perpendicular to the liquid crystal cell.

FIG. 11 is a diagram illustrating a viewing angle in all directions of Sample A with a contrast of 10 as a reference.

FIG. 12 is a diagram illustrating an omnidirectional viewing angle based on contrast 10 of sample B (first embodiment of the present invention).

FIG. 13 is a diagram illustrating a viewing angle in all directions with reference to contrast 10 of sample C.

FIG. 14 is a diagram illustrating a viewing angle in all directions with reference to contrast 10 of sample D (second embodiment of the present invention).

FIG. 15 is a diagram illustrating a viewing angle of Sample E in all directions with a contrast of 10 as a reference.

[Explanation of symbols]

 CE ... Liquid crystal cell A, B ... Polarizing plate PA, PB ... Polarization axis L0 ... Natural light L1, L2, L3 ... Polarized light LC ... Liquid crystal molecule when voltage is applied PS ... Light path RF ... Laminated optical anisotropic element

Claims (5)

[Claims] 1. A twist angle of about 90 between two electrode substrates.
Liquid crystal cell sandwiching a TN-type liquid crystal of 2 °, two polarizing elements arranged on both sides of the liquid crystal cell, and a liquid crystal display element in which two or more optical anisotropic elements are disposed between the two polarizing elements. In, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is 5 ° to the normal direction to the liquid crystal cell surface.
A liquid crystal display device characterized by being tilted by 60 °. 2. The twist angle between the two electrode substrates is approximately 90.
Liquid crystal cell in which a TN type liquid crystal of 90 ° is sandwiched, two polarizing elements arranged on both sides of the liquid crystal cell, and a liquid crystal display in which two or more optical anisotropic elements are arranged between the liquid crystal cell and the polarizing element. In the element, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is tilted at 5 ° to 60 ° from the direction normal to the liquid crystal cell surface. A liquid crystal display device characterized in that the directions orthogonally projected on the liquid crystal cell surface are different from each other. 3. The twist angle between the two electrode substrates is approximately 90.
Liquid crystal cell sandwiching a TN-type liquid crystal of 2 °, two polarizing elements arranged on both sides of the liquid crystal cell, and a liquid crystal display element in which two or more optical anisotropic elements are disposed between the two polarizing elements. In, the optical anisotropic element exhibits negative uniaxiality, and the optical axis of the optical anisotropic element is 5 ° to the normal direction to the liquid crystal cell surface.
It is inclined by 60 °, and the angle formed by the orthogonal projection of the optical axes of the optical anisotropic elements on both sides of the liquid crystal cell to the liquid crystal cell surface and the rubbing axis direction of the adjacent liquid crystal cell substrate is −45 ° or more and 45 ° or more. And the angle between the directions of the orthogonal projections of the optical axes of the two optically anisotropic elements on the surface of the liquid crystal cell is 0 ° or more and 9 or more.
A liquid crystal display device characterized by being 0 ° or less. 4. The twist angle between the two electrode substrates is approximately 90.
Liquid crystal cell sandwiching a TN type liquid crystal of two degrees, two polarizing elements arranged on both sides of the liquid crystal cell, and two or more optical anisotropic elements laminated between the liquid crystal cell and the polarizing element. In the arranged liquid crystal display element, the optical anisotropic element exhibits negative uniaxiality, the optical axis of the optical anisotropic element is inclined 5 ° to 60 ° from the direction normal to the liquid crystal cell surface, and the liquid crystal cell The angle formed by the orthogonal projection of the optical axis of the anisotropic optical element closest to the liquid crystal cell surface to the rubbing direction of the liquid crystal cell substrate closer to the optical anisotropic element is -45 ° or more and 45 ° or less. The angle formed by the direction of orthogonal projection of the optical axis of the optical anisotropic element farthest from the liquid crystal cell on the liquid crystal cell surface and the rubbing direction of the liquid crystal cell substrate farther from the optical anisotropic element is -45 ° or more and 45 ° or less. And the optical axis of the optical anisotropic element closest to the liquid crystal cell is A liquid crystal display device characterized in that an angle formed between a direction orthogonally projected to a surface and a direction orthogonally projected to the liquid crystal cell surface is an optical axis of an optical anisotropic element farthest from the liquid crystal cell is 0 ° or more and 90 ° or less. . 5. The liquid crystal display element according to claim 1, wherein the retardation of the optically anisotropic element at a light of 632.8 nm is −50 nm to −600 nm.