JPH08101381A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To improve the display contrast and visual angle characteristics of the display color without decreasing the front view contrast by controlling the spectrum dispersion of refractive index anisotropy of an optical anisotropic element to be smaller than the spectrum dispersion of the refractive index anisotropy of a TN liquid crystal. CONSTITUTION: This liquid crystal element consists of a liquid crystal cell having a TN liquid crystal with 90 deg. tilt angle held between electrode substrates, two polarizing elements disposed on both sides of the liquid crystal cell, and an optical anisotropic element between the liquid crystal cell and the polarizing element. The spectrum dispersion of the refractive index anisotropy of the optical anisotropic element is controlled to be smaller than the spectrum dispersion of the refractive index anisotropy of the TN liquid crystal. Namely, by arranging the optical anisotropic element between the polarizing plate and the liquid crystal cell, this optical anisotropic element acts like a double refractive material which increases deviation of light with increase of the incident angle of the light to the optical axis. By this method, decrease in the contrast for oblique incident light is prevented and the visual angle characteristics are improved as well as the front view contrast is improved.

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, display color and viewing angle characteristics of intermediate gradation.

[0002]

2. Description of the Related Art A CRT, which is a mainstream display device of OA equipment such as a Japanese word processor and a desktop personal computer.
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. Display methods using such a liquid crystal can be roughly classified into two methods, 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. Therefore, a simple matrix without active elements (thin film transistor or diode). A large-capacity display can be obtained by time-division driving even with a striped electrode structure. 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 as compared with other LCDs because it has a high response speed (several + milliseconds), can easily obtain a black and white 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.

SID '92 Digest p. 798
As has been described, there is proposed a method of compensating the viewing angle characteristic by dividing the pixel and inverting the tilt directions when applying a voltage. According to this method, the viewing angle characteristics relating to the gradation inversion in the vertical direction are improved, but the viewing angle characteristics of the contrast are hardly improved.

JP-A-4-229828 and JP-A-4-4-2
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 liquid crystal cell.

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, does not exert any optical action from the front and tilts. 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.

Further, 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. It is a layered 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 Publication No. 5-215921 proposes a method for optically compensating an LCD by a birefringent plate in which a rod-shaped compound exhibiting liquid crystal property at the time of curing 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.

Further, in JP-A-3-9326 and JP-A-3-291601, LC is obtained by applying a polymer liquid crystal to a film-like substrate having an alignment film.
Although an optical compensating plate for D is described, it is impossible to orient the molecules obliquely by this method, and therefore it is not possible to expect any improvement in the omnidirectional viewing angle of the TN type LCD.

Further, in EP0576304A1, an optical anisotropic element whose optical axis is neither perpendicular nor parallel to the film surface is arranged between a pair of polarizing plates and a liquid crystal cell to expand the viewing angle. The method is proposed. Although this method improves the viewing angle characteristics as compared with the method of disposing a retardation film having a retardation of almost zero in the direction perpendicular to the surface of the liquid crystal cell, it is still insufficient. 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 depending on the viewing direction. Appears as a phenomenon, which is not preferable for practical use.

Most of the optically anisotropic elements have wavelength dispersion in which the anisotropy of refractive index in the visible region is large on the short wavelength side and small on the long wavelength side. When such an optical anisotropic element is mounted on a TN type liquid crystal cell, there is a drawback that the tint changes greatly depending on the viewing angle.

[0014]

DISCLOSURE OF THE INVENTION According to the present invention, in a TN type liquid crystal cell, the display contrast and the viewing angle characteristics of the display color are improved without lowering the front contrast, and the intermediate gradation is accurately displayed regardless of the viewing angle. The present invention provides a liquid crystal display device that can be manufactured.

[0015]

The above-mentioned objects have been achieved by the following means. (1) T with a twist angle of about 90 ° between two electrode substrates
A liquid crystal display device comprising a liquid crystal cell sandwiching an N-type liquid crystal, two polarizing elements arranged on both sides of the liquid crystal cell, and at least one optical anisotropic element disposed between the liquid crystal cell and the polarizing element. A liquid crystal display element, wherein the wavelength dispersion of refractive index anisotropy of the optically anisotropic element is smaller than the wavelength dispersion of refractive index anisotropy of the TN type liquid crystal. (2) The liquid crystal display device according to (1), wherein the refractive index anisotropy of the optically anisotropic element does not change in the visible region or is small on the short wavelength side and large on the long wavelength side. (3) At least one of the optically anisotropic elements has no direction in which the retardation value is zero, and the direction in which the absolute value of the retardation value is minimum is neither in the normal direction of the film nor in the surface direction. (2) The liquid crystal display device as described above. (4) The optically anisotropic element is composed of at least two layers having different optical characteristics, at least one layer has an optically negative uniaxial property, and an optical axis is a film normal direction.
The liquid crystal display device according to (3), wherein at least one of the other layers has an optically negative uniaxial property, and the optical axis is tilted by 5 ° to 85 ° from the film normal direction.

The operation of the present invention will be described below by taking a TN type liquid crystal display device as an example with reference to the drawings. 1, 2, and 3
Shows the polarization state of the light propagating in the liquid crystal cell when a voltage higher than the threshold voltage is applied to the liquid crystal cell, and shows the bright state when no voltage is applied. Figure 2
FIG. 6 is a diagram showing a polarization state of light when light is vertically incident on a liquid crystal cell. When the natural light 0 is vertically incident on the polarizing plate 1 having the polarization axis 1.1, the light transmitted through the polarizing plate 1 is
Linearly polarized light becomes 1.3.

In the figure, 3.3 is a schematic representation of the alignment state of liquid crystal molecules when a sufficient voltage is applied to the TN type liquid crystal cell by one liquid crystal molecule model. When the molecular long axis of the liquid crystal molecules 3.3 in the liquid crystal cell is parallel to the light traveling path 1.4, there is no difference in the refractive index on the incident surface (in the plane perpendicular to the light traveling path). There is no phase difference between the ordinary light and the extraordinary light propagating through it, and the linearly polarized light 1.3 propagates as it is when it passes through the liquid crystal cell. When the polarization axis 2.1 of the polarizing plate 2 is set to be perpendicular to the polarization axis 1.1 of the polarizing plate 1, the light 3.1 that has passed through the liquid crystal cell cannot pass through the polarizing plate and is in a dark state.

FIG. 3 is a diagram showing the polarization state of light when the light obliquely enters the liquid crystal cell. Natural light of incident light 0
Is incident obliquely, the polarized light 1.
3 becomes almost linearly polarized light. (In the actual case, it will be elliptically polarized due to the characteristics of the polarizing plate). In this case, a difference in refractive index occurs on the incident surface of the liquid crystal cell due to the anisotropy of the refractive index of the liquid crystal,
The light 3.1 transmitted through the liquid crystal cell is elliptically polarized and transmitted through the polarizing plate 2. The transmission of light in such an oblique incidence undesirably lowers the contrast.

The present invention is intended to prevent such a decrease in contrast due to oblique incidence, improve viewing angle characteristics, and at the same time improve front contrast. FIG.
Shows an example of the configuration according to the present invention. The optical anisotropic element 7 of the present invention is arranged between the polarizing plate 2 and the liquid crystal cell 3. The optical anisotropic element 7 functions like a birefringent body that polarizes more as the angle of incidence of light with respect to the optical axis increases. As in the case of FIG. 3, the elliptically polarized light 3.1 which is obliquely incident on the liquid crystal display element having such a structure and which has been transmitted through the liquid crystal cell 3 is transmitted through the laminated body 7 of optically anisotropic elements. The elliptically polarized light is modulated into the original linearly polarized light by the phase delaying action, and a good liquid crystal display device having the same transmittance even at various oblique incidences and having no viewing angle dependence can be realized.

It is presumed as follows that the viewing angle characteristics of the liquid crystal display element were significantly improved by the present invention. 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, but at this time, the TN type liquid crystal cell can be regarded as a positive uniaxial optical anisotropic body in which the optical axis is slightly inclined from the direction normal to the cell surface. This slight tilt of the optical axis not only causes birefringence even in front of the cell, but also causes significant asymmetry of the viewing angle in the vertical direction of the cell, that is, the main viewing angle direction, which significantly impairs the viewing angle in either one or both directions. become.

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, the viewing angle characteristics may be improved by the negative uniaxial optical anisotropic body in which the optical axis of the present invention is tilted from the normal direction. (FIG. 4)

However, regarding the optical anisotropy of the TN type liquid crystal cell as a positive uniaxial property is merely an approximation, and in reality, the liquid crystal cell is not a simple positive optical anisotropic body but a twisted orientation. , The tilt angle is also changing. Therefore, it is naturally limited to compensate with a negative uniaxial optical anisotropic body having an inclined optical axis. As a result of diligent studies, the present inventors have further improved the viewing angle and opened up the possibility of CRT substitution, in the direction in which the retardation value becomes zero, that is, the optical axis does not exist, and It has been found that it can be realized by using an optical anisotropic element in which the direction in which the absolute value of the retardation value becomes the minimum is neither the film normal direction nor the surface direction. Further, as a specific method thereof, by stacking an optical anisotropic body having a negative uniaxial property and an optical axis inclined and an optical anisotropic body having a negative uniaxial property and having an optical axis in the film normal direction, It was possible to realize optical characteristics in which there was no optical axis and the minimum Re value was neither in the film normal direction nor in the plane direction. According to the present invention, since the TN type liquid crystal cell can be completely compensated at the time of displaying black, it is possible to realize a great improvement in the viewing angle characteristics in terms of contrast.

Further, in the conventional TN type LCD, there is a problem that the halftone characteristic changes depending on the viewing angle, which occurs in full color display or the like. These are called gradation inversion, white spots, and black shadows depending on the phenomenon that occurs. According to the present invention, it is possible to significantly reduce the change in the halftone characteristics depending on the viewing angle.

The above is the description of compensation for light of a certain fixed wavelength, but in practice, compensation of light of various wavelengths must be performed as in the case of color display. If the light of various wavelengths in the visible range is not sufficiently compensated, the liquid crystal display element causes a tint change depending on the viewing angle.

The refractive index anisotropy of the liquid crystal used in the TN type liquid crystal cell generally has a wavelength dispersion that is large on the short wavelength side and small on the long wavelength side. When an optical anisotropic element is attached to a TN type liquid crystal cell, the wavelength dispersion of the refractive index anisotropy of the optical anisotropic element is equal to or larger than the wavelength dispersion of the refractive index anisotropy of the liquid crystal used in the TN type liquid crystal cell. Then, even if the light having a certain wavelength is compensated, the light having a different wavelength is not compensated. This is the reason why the tint changes depending on the viewing angle.

By making the wavelength dispersion of the refractive index anisotropy of the optically anisotropic element smaller than the wavelength dispersion of the refractive index anisotropy of the TN type liquid crystal, we have made it possible to obtain light of all wavelengths in the visible region. Have found that compensation will be provided. By compensating for light of all wavelengths in the visible range, the change in tint depending on the viewing angle could be greatly reduced. In the present invention, the wavelength dispersion αLC of the refractive index anisotropy of the liquid crystal is set to the wavelength of 450
nm and 550 nm light retardation ratio, Re
It is defined by (λ = 450 nm) / Re (λ = 550 nm). Similarly, the wavelength dispersion α of the refractive index anisotropy of the optically anisotropic element
RF is Re (λ = 450 nm) / Re (λ = 550n
Defined in m). In the present invention, the fact that the wavelength dispersion of the refractive index anisotropy of the optically anisotropic element is smaller than the wavelength dispersion of the refractive index anisotropy of the TN type liquid crystal means that αRF <αLC.

In order to further reduce the color change due to the viewing angle, an optical anisotropic element having no wavelength dispersion of refractive index anisotropy or having a small wavelength dispersion on the short wavelength side and a large wavelength dispersion on the long wavelength side is used. It is effective to use. That is, αRF ≦
An optical anisotropic element having a value of 1.0 is used. As a result, it was possible to almost eliminate the change in tint due to the viewing angle of the TN type liquid crystal display element equipped with the optically anisotropic element.

The above description has been made by taking the normally white mode as an example, but the same applies to the normally black mode. In the normally black mode, black display is when no voltage is applied. Also in this case, by using an optical anisotropic element in which the optical axis does not exist and the direction in which the absolute value of the retardation value is the minimum is neither the film normal direction nor the surface direction, contrast, intermediate gradation, and tint The change in viewing angle could be greatly reduced.

In the retardation of the present invention, the optically anisotropic element is divided into layers that can be regarded as having uniform optical characteristics,
It is the sum of the absolute values of the retardation of each layer when viewed from a certain direction. The optical anisotropic element of the present invention has a minimum absolute value of retardation when viewed from any direction, and the direction is neither the film normal direction nor the surface direction. Further, the minimum absolute value of retardation is not zero. In the present invention, at least one such optical anisotropic element is used.

In the present invention, as a specific method for realizing an optical anisotropic element in which the optical axis does not exist and the absolute value of the retardation value is not the film normal direction or the surface direction, a negative uniaxial A method is preferred in which an optical anisotropic body having optical properties and an optical axis inclined and an optical anisotropic body having negative uniaxiality and having an optical axis in the film normal direction are stacked.

Negative uniaxiality in the present invention means the refractive index in the triaxial direction of an optically anisotropic body, n1 and n in the ascending order.
When there are 2 and n3, the relationship of n1 <n2 = n3 is satisfied. Therefore, it has a characteristic that the refractive index in the optical axis direction is the smallest. However, the values of n2 and n3 do not have to be exactly equal, and it is sufficient if they are almost equal. Specifically, if | n2-n3 | / | n2-n1 | ≦ 0.2, there is no practical problem.

The tilt angle of the optical axis of the optically anisotropic body having negative uniaxiality and having the tilted optical axis in the present invention is 5 ° from the normal to the sheet surface as a condition for significantly improving the viewing angle characteristics. It is preferable to incline by ~ 85 °, and 10 ° -4
0 ° is more preferable, and 20 ° to 35 ° is most preferable.
Further, when the thickness of the sheet is D and Δn = n2-n1 is defined, it is preferable that the condition of 50 ≦ Δn · D ≦ 400 (nm) is satisfied.

The material used for the optically anisotropic body having negative uniaxiality and having an inclined optical axis is not particularly limited, but various polymer materials, liquid crystals, or blends thereof are preferably used. It Of these, liquid crystals, particularly discotic liquid crystals, are preferably used. The discotic liquid crystal as used herein includes a group that has a group that reacts with heat, light, etc., and consequently polymerizes or crosslinks due to the reaction to have a high molecular weight and lose the liquid crystallinity.

Regarding the optically anisotropic substance having the negative uniaxial property and the optical axis in the film normal direction in the present invention,
The main in-plane refractive index is nx, ny, the refractive index in the thickness direction is nz,
Thickness
When d, 0 ≦ | nx−ny | × d ≦ 50 (nm), more preferably 0 ≦ | nx−ny | × d ≦ 20 (nm) and satisfying the following conditions It has a remarkable effect on the angle expansion. That is, preferably, 20 ≦ {(nx + ny) / 2−nz} × d ≦ 300
(Nm), and more preferably 30 ≦ {(nx + ny) / 2−nz} × d ≦ 150.
(Nm).

The material used for the optically anisotropic body having negative uniaxiality and having the optical axis in the film normal direction is not particularly limited, but various polymeric materials, liquid crystals, or blends thereof, etc. Is preferably used. Among these,
Films made of polymeric materials are preferred. Such a polymer film has a light transmittance of 80% or more, and as described above, it is preferable that the optical characteristics on the front surface are close to isotropic. Therefore, Zeonex (Zeon Japan), ARTON
Materials having a small intrinsic birefringence such as (Nippon Synthetic Rubber) and Fujitac (Fuji Photo Film Co., Ltd.) are preferable. However, even a material having a large intrinsic birefringence such as polycarbonate, polyarylate, polysulfone, and polyethersulfone can be made optically isotropic by controlling the molecular orientation during film formation. They can also be suitably used.

In the present invention, the optical anisotropic element having no optical axis and the direction in which the absolute value of the retardation value is the minimum is neither the film normal direction nor the surface direction has negative uniaxiality and has an optical axis. Can be realized by stacking an optical anisotropic body having a negative uniaxiality with an inclined optical anisotropic body having an optical axis in the film normal direction. More specifically, it can be realized by applying an alignment film to a negative uniaxial film whose optical axis is the film normal direction, rubbing the film, and continuously thinly applying a discotic liquid crystal thereon. When such an optical anisotropic element is attached to a liquid crystal cell, there are cases where a discotic liquid crystal layer is arranged near the liquid crystal cell and cases where a uniaxial film is arranged near the liquid crystal cell. It may be placed in. However, in order to maximize the compensation ability, it is preferable to dispose the discotic liquid crystal layer near the liquid crystal cell.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. Example 1 A long-chain alkyl-modified Poval (MP-203 manufactured by Kuraray Co., Ltd.) was applied on a 100 μm thick film of triacetyl cellulose (manufactured by Fuji Photo Film Co., Ltd.) coated with a gelatin thin film (0.1 μm). After drying with warm air, rubbing treatment was performed to form an alignment film. When the in-plane main refractive index is nx, ny, the refractive index in the thickness direction is nz, and the thickness is d, the triacetyl cellulose film has | nx-
ny | × d = 3 nm, {(nx + ny) / 2−nz} × d =
The thickness was 70 nm, which was almost uniaxial, and the optical axis was almost in the film normal direction.

A discotic liquid crystal was applied on this alignment film, and then UV light was irradiated to cross-link it. The discotic liquid crystal layer had a thickness of about 1.0 μm. This discotic liquid crystal layer has n
When 1, n2, and n3 are satisfied, the relationship of n1 <n2 = n3 is satisfied, and the uniaxial property is negative. The optical axis was inclined by 35 ° from the film normal direction. When the thickness of the discotic liquid crystal layer is D, (n2-n1) .D = 1
It was 20 nm.

The optically anisotropic element thus obtained is
Δn · D in the direction inclined by 37 ° from the film normal direction
Has the minimum absolute value of 17 nm.

The product of the difference in refractive index between the extraordinary light and the ordinary light of the liquid crystal and the gap size of the liquid crystal cell is 470 nm, and the twist angle is 9
Two optical anisotropic elements were mounted in a 0 degree TN type liquid crystal cell so as to sandwich the liquid crystal display element. Two polarizing plates were arranged orthogonally so as to sandwich the whole on the outside.

The wavelength dispersion of the refractive index anisotropy of the liquid crystal in the TN type liquid crystal cell used here and the wavelength dispersion of the optically anisotropic element are shown in FIG. αLC = 1.06 and αRF = 1.00. αLC> αRF, and the wavelength dispersion of the optically anisotropic element is smaller than the wavelength dispersion of the liquid crystal in the TN type liquid crystal cell.

To this liquid crystal cell, a voltage of 1 V was applied with a rectangular wave of 55 Hz to display white. A cold cathode tube is used as the backlight, and the color change from all directions is TOPCON
It was performed at bm-7. The result is expressed as x vs. y 193
It is shown in FIG. 6 by the 1CIE chromaticity diagram. Since the tint change was symmetrical on the left and right, only the right half is shown in FIG. Also,
The direction of inclination from the front is 5 for upper, upper right, right, lower right, and lower.
In the direction, the tilt angle indicates data from the front up to 60 ° in 5 ° steps.

Example 2 In the same TN type liquid crystal cell as in Example 1, two optical anisotropic elements having wavelength dispersion as shown in FIG. 5 were mounted so as to sandwich the liquid crystal. αRF = 0.58, αLC> αRF
Met. Two polarizing plates were arranged orthogonal to each other on the outer side thereof.
Also in this case, the color change measurement in all directions was performed in the same manner as in Example 1. FIG. 7 shows the result.

Comparative Example 1 In the same TN type liquid crystal cell as in Example 1, two optical anisotropic elements having wavelength dispersion as shown in FIG. 5 were mounted so as to sandwich the liquid crystal. αRF = 1.07, αLC <αRF
Met. Two polarizing plates were arranged orthogonal to each other on the outer side thereof.
Also in this case, the color change measurement in all directions was performed in the same manner as in Example 1. FIG. 8 shows the result.

It can be seen that in Examples 1 and 2 which are the present invention, the tint change depending on the viewing angle was improved as compared with Comparative Example 1.

[0046]

According to the present invention, the TN type liquid crystal display element, the TFT type liquid crystal display element, the MIM type liquid crystal display element, the TFD.
It is possible to provide a high-quality liquid crystal display element with improved visibility, in which the viewing angle characteristics of the liquid crystal display element are improved.
Needless to say, the present invention can be applied to other active matrix liquid crystal display elements using three-terminal elements and two-terminal elements to obtain excellent effects.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram of a conventional TN type liquid crystal display element and a diagram for explaining a light transmission state when light is obliquely incident on a display surface.

FIG. 4 is a schematic diagram showing the principle that the viewing angle characteristics are improved by a negative uniaxial optical anisotropic body whose optical axis is tilted from the normal direction.

FIG. 5 is a diagram illustrating wavelength dispersion of refractive index anisotropy of Examples 1 and 2 and Comparative Example 1 and TN liquid crystal.

FIG. 6 is a diagram illustrating a change in tint depending on the viewing angle according to the first exemplary embodiment.

FIG. 7 is a diagram illustrating a change in tint depending on the viewing angle according to the second embodiment.

FIG. 8 is a diagram illustrating a change in tint depending on the viewing angle in Comparative Example 1.

[Explanation of symbols]

 0 ------------- Incident light 1, 2 -------- Polarizing plate 1.1, 2.1 --- Polarizing axis 1.3 ----- Emitted from the polarizer Light 1.4 ----- Direction of Light 3 ------------ TN liquid crystal cell 3.1 Light emitted from TN liquid crystal cell 3.3 Liquid crystal molecule 7 ------------- Optical anisotropic element

Claims (4)

[Claims] 1. A twist angle of about 90 between two electrode substrates.
Liquid crystal display in which a TN-type liquid crystal is sandwiched, two polarizing elements arranged on both sides of the liquid crystal cell, and at least one optical anisotropic element is disposed between the liquid crystal cell and the polarizing element. In the device, the liquid crystal display device is characterized in that the wavelength dispersion of refractive index anisotropy of the optically anisotropic element is smaller than the wavelength dispersion of refractive index anisotropy of the TN type liquid crystal. 2. The liquid crystal display element according to claim 1, wherein the refractive index anisotropy of the optically anisotropic element does not change in the visible region or is small on the short wavelength side and large on the long wavelength side. 3. At least one of the optical anisotropic elements has no direction in which the retardation value is zero, and the direction in which the absolute value of the retardation value is the minimum is in the normal direction of the film and the surface direction. The liquid crystal display element according to claim 2, wherein the liquid crystal display element is absent. 4. The optically anisotropic element is composed of at least two layers having different optical characteristics, at least one layer having an optically negative uniaxial property and an optical axis being in a film normal direction, and at least another. One layer has optically negative uniaxiality and the optical axis is 5 ° to 85 ° from the film normal direction.
The liquid crystal display element according to claim 3, wherein the liquid crystal display element is inclined.