JPH07175058A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To decrease the variation in display so that the variation is observed with uniform contrast by providing a liquid crystal display element with two sheets of polarizing plates clamping a first liquid crystal cell and specific second liquid crystal cell from above and below. CONSTITUTION:This liquid crystal display element consists of two sheets of the polarizing plates 1, 3 and the first liquid crystal cell 5 for display and the second liquid crystal 7 for optical compensation therebetween. The liquid crystal cell 7 has substrates 17, 19 which are formed averting an orientation treatment and a liquid crystal layer 21 in which the major axis direction of liquid crystal molecules is held in an approximately horizontal posture to the substrate surfaces and directed in approximately ununiform direction in the substrate surface while being held in approximately horizontal posture at the time of non-impression of a voltage and is clamped between the substrates in such a manner that the liquid crystal molecules are twist-arranged in a direction perpendicular to the substrate surfaces and have the optical rotatory power varying with each of the bearings of the liquid crystal molecules. Then, transmitted light of the liquid crystal cell 5 is optically compensated by the liquid crystal cell 7 of a multidomain structure even if this light is colored by the double refraction effect of the liquid crystal layer 37 or the dependency thereof on bearing angles is stressed.

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, and more particularly to a liquid crystal display device in which the viewing angle dependence such as contrast ratio and display color is controlled.

[0002]

2. Description of the Related Art In recent years, liquid crystal display elements, which have the great advantages of thinness, light weight, and low power consumption, have been actively used as display devices for personal OA equipment such as Japanese word processors and desktop personal computers.

As a liquid crystal display element (hereinafter, abbreviated as LCD), twisted nematic liquid crystal is generally used at present, but the display system can be roughly classified into two types, TN type and STN type. .

The TN type LCD has a molecular arrangement twisted by 90 degrees and exhibits a high contrast ratio when a low voltage is applied, so that it is not only used as a display device such as a clock or a calculator but also as a liquid crystal television or an OA. It is also widely used for device displays. In particular, a display device for a display of a liquid crystal television or OA equipment is required to have a large display capacity and a high-speed operation. Therefore, an active matrix method in which a switching element such as a thin film transistor (TFT) or a diode is formed in each portion corresponding to each display pixel. Is applied.

On the other hand, the STN LCD has a steep electro-optical characteristic with a molecular arrangement that is largely twisted, for example, about 240 degrees, so that a switching element is not formed for each pixel, but a matrix shape is formed. Large-capacity display can be realized even with a simple matrix type liquid crystal display element having a simple structure in which electrodes are arranged opposite to each other.

However, since the birefringence effect is utilized, the so-called yellow mode display in which the display is colored in yellow and dark blue, and the so-called blue mode display in white and blue (these colorings (display colors) are displayed above and below the liquid crystal cell). (It depends on the direction of the absorption axis of the polarizing plate) and it was impossible to display in black and white in practical use.

As a means for eliminating such coloring of display, a second liquid crystal cell, which is twisted in the opposite direction to the display liquid crystal cell, is arranged between the display liquid crystal cell and the polarizing plate. The technology of realizing black and white display by doing
For example, it is disclosed in Japanese Patent Publication No. 57-96315. The principle of black and white is that the liquid crystal cells for display in which the liquid crystal molecules are arranged in a twisted pattern enter the elliptically polarized ordinary light component and extraordinary light component light by the second liquid crystal cell, which is an optical compensator. Instead, elliptically polarized light is converted into linearly polarized light. As a result, the same polarization can be obtained without changing the polarization direction for each wavelength of light, and black-and-white display can be realized. Here, in order to convert the elliptically polarized light into the linearly polarized light as described above, the second liquid crystal cell has a retardation value that is substantially the same as the retardation value of the first liquid crystal cell that performs display, and has a twist direction. Are opposite to each other, and their arrangement is configured so that the orientation directions of the liquid crystal molecules closest to each other are orthogonal to each other.

However, the above STN type and TN type liquid crystal display elements have a viewing angle dependency that the display color and the contrast ratio change depending on the viewing angle and the azimuth, and the display performance of a CRT (Cathode Ray Tube). It has not yet reached the point where it completely crosses. For example, a TN type liquid crystal display element has a viewing angle characteristic as shown in FIG. FIG. 4 is a diagram called an isocontrast characteristic diagram, and is often used to show the viewing angle characteristic of a liquid crystal display element. As shown in FIG. 5, the observing points of the liquid crystal display element are azimuth angle φ and incident angle θ.
The incident angle θ showing the same contrast ratio when the observed azimuth φ is changed is shown in the polar coordinate system as shown in FIG. As an ideal liquid crystal display element, it is desired that the incident angle θ is large at any azimuth angle φ. As can be seen from the measurement results in Fig. 4, the azimuth φ is 90 degrees, 210
The incident angle θ increases near 330 degrees and 330 degrees, and the azimuth φ is 45 degrees.
The incident angle θ is small at around 135 degrees and 270 degrees. The maximum contrast ratio is obtained near the front of the liquid crystal display element, and when the incident angle θ is changed, the contrast ratio changes abruptly, and the screen at this time causes a noticeable discomfort. . As in this example, the liquid crystal display element has a problem that the same contrast ratio cannot be obtained when the viewing angle is changed, and the contrast ratio greatly changes depending on the incident angle θ and the azimuth φ.

On the other hand, in a liquid crystal display element having a structure in which a liquid crystal cell in which a nematic liquid crystal having a negative dielectric anisotropy is vertically aligned is sandwiched between polarizing plates, a cholesteric liquid crystal is sandwiched between the liquid crystal cell and the polarizing plate, and a viewing angle is increased. An attempt to improve the above is disclosed in, for example, Japanese Patent Laid-Open No. 3-67219. However,
In this case, a liquid crystal cell in which a nematic liquid crystal with a negative dielectric anisotropy is vertically aligned has a problem in the alignment technology, a response speed in the liquid crystal material, or the specific resistance of the liquid crystal does not become sufficiently high. There is a problem that it is not practically suitable for use in a liquid crystal display device.

[0010]

As described above, in the conventional liquid crystal display device, the direction in which the maximum contrast ratio is obtained is limited to near the front face of the liquid crystal display device, and the incident angle is changed from the front face. There was a problem in that the contrast ratio drastically changed as it went, making the viewer feel uncomfortable. Actually, the viewing angle of the liquid crystal display element is often oblique, and this is remarkable particularly in the case of a small liquid crystal display element.

The present invention has been made in order to solve such a problem, and its purpose is to reduce variations in light from any azimuth angle and any incident angle. An object of the present invention is to provide a liquid crystal display device that can realize an image display that is observed with a uniform contrast.

[0012]

In order to solve the above problems, the liquid crystal display element of the present invention comprises two substrates in which image display electrodes are arranged and are opposed to each other with a gap therebetween. , A first liquid crystal cell having a liquid crystal layer enclosed and sandwiched in a space between the two substrates and displaying an image by applying a voltage to the image display electrode, and combined with the first liquid crystal cell in an overlapping manner. The second liquid crystal cell is formed so as not to be subjected to an alignment treatment for aligning the major axis directions of liquid crystal molecules in the same direction, and is arranged to face each other with a gap.
Two substrates, the long axis direction of the liquid crystal molecules with respect to the substrate surface is held in a substantially horizontal posture when no voltage is applied, and the long axis direction of the liquid crystal molecules is held in the substantially horizontal posture while the substrate surface is held. The liquid crystal molecules are twisted and aligned in a gap between the two substrates in a direction perpendicular to the surface of the substrate, and have different optical rotatory powers depending on the directions of the liquid crystal molecules. A second liquid crystal cell having a liquid crystal layer sandwiched between the two substrates, and the first liquid crystal cell and the second liquid crystal cell combined with the first liquid crystal cell sandwiched from above and below. And a polarizing plate.

Alternatively, in the above liquid crystal display device,
The value of the product of the twist pitch value of the arrangement of the liquid crystal layer of the second liquid crystal cell and the magnitude of the difference in the refractive index of the liquid crystal layer used for the second liquid crystal cell is shorter than the shortest visible wavelength. .

Alternatively, in the above liquid crystal display device,
The second liquid crystal cell is characterized by being made of a polymer liquid crystal.

The optical rotatory power of the liquid crystal layer of the second liquid crystal cell is such that the transmitted light is hardly colored,
Alternatively, when the transmitted light connects the images on the screen, it is desirable to set the optical rotatory power so small that the coloring is hardly noticeable.

The "shortest visible wavelength" means that the short wavelength end is 380 to 400 nm and the long wavelength end is 760 nm to 830 n.
It is in the range of m.

[0017]

Even if the transmitted light of the first liquid crystal cell is colored due to the birefringent action of the liquid crystal layer or the azimuth angle dependency is emphasized, these are optically compensated by the second liquid crystal cell of the multi-domain structure. As a result, it is possible to improve the coloring of light and the azimuth angle dependency when forming an image through the first liquid crystal cell and the second liquid crystal cell.

Further, such a liquid crystal cell for compensating the viewing angle can be produced not only by a liquid crystal consisting of mere small to medium scale organic molecules which is generally used at present but also by a polymer liquid crystal, and the liquid crystal is sandwiched. It is possible to realize a more desirable liquid crystal display device that is thin and lightweight because a substrate is not needed. As the polymer liquid crystal, for example, a polymer copolymer in which a main chain of polysiloxane and a side chain of biphenylbenzoate and a cholesteryl group are mixed at a specific ratio can be used. As a liquid crystal cell for display,
Needless to say, similar effects can be obtained not only by using a TN cell but also by a homogeneously aligned liquid crystal cell having no twist angle or a vertically aligned homeotropically aligned liquid crystal cell.

[0019]

Embodiments of the liquid crystal display device of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing the structure of a liquid crystal display device according to a first embodiment of the present invention. This liquid crystal display device has two polarizing plates 1 and 3 (LLC2-92-18;
(Manufactured by SANRITZ Co., Ltd.) and a first liquid crystal cell 5 for display and a second liquid crystal cell 7 for optical compensation are sandwiched between them to form a main part.

The polarizing plate 1 has a polarizing film 1 inside the transparent substrate 9.
1 is sandwiched between them, and the polarizing plate 3 is also formed on the transparent substrate 13 in the same manner.
5 is formed in a sandwiched structure. These polarizing plates 1 and 3 are arranged such that their light transmission axes are orthogonal to each other.

The second liquid crystal cell 7 comprises transparent substrates 17 and 19
The liquid crystal layer 21 is sandwiched between them. The liquid crystal layer 21 includes a transparent substrate 19 on the lower side and a transparent substrate 17 on the upper side.
It is formed in a so-called STN type in which liquid crystal molecules are arranged so as to be twisted clockwise by 490 degrees. Then, on the surfaces of the substrates 17 and 19 in contact with the liquid crystal layer 21,
Although the alignment films 23 and 25 having horizontal alignment are formed,
The rubbing alignment treatment is not applied to the surfaces of the alignment films 23 and 25, and a spacer (not shown) made by Sekisui Fine Chemical Co., Ltd. having a particle diameter of 4 μm is inserted as a gap material to keep the cell gap at about 4 μm. Meanwhile, a sealing material is applied to the periphery of the substrate to assemble. As the liquid crystal composition, nematic liquid crystal ZLI-2806 manufactured by E. Merck was used, and right-handed chiral agent R811 (manufactured by E. Merck) was mixed so that the spiral pitch was 2.96 μm. The liquid crystal layer 21 having a good orientation is obtained by injecting it into the cell in the state of the square phase and gradually cooling it to the nematic phase. Thus, a so-called multi-domain orientation in which the orientation of the liquid crystal molecules of the liquid crystal layer 21 was randomly twisted on the substrate surface was obtained.

The first liquid crystal cell 5 is arranged between the second liquid crystal cell 7 and the polarizing plate 3. The upper transparent substrate 27 and the lower transparent substrate 29 are the transparent electrodes 3 respectively.
1, 33 are provided, and these transparent electrodes 31, 3 are provided.
3 is connected to the drive circuit 35. Transparent substrates 27, 2
A liquid crystal composition in which a chiral agent S811 (manufactured by E. Merck) is mixed with a twisted nematic liquid crystal (ZLI-4287; manufactured by E. Merck) is introduced between 9 and the transparent substrate 27 with liquid crystal molecules on the upper side.
To the lower transparent substrate 29, a liquid crystal layer 37 is formed in which the twist angle is arranged counterclockwise at a twist angle of 90 degrees. The thickness of the liquid crystal layer is about 5.5 μm. Needless to say, the liquid crystal layer 37 changes its state according to the drive voltage applied from the drive circuit 35.

FIG. 2 is a diagram showing the optical configuration of the liquid crystal display element of the first embodiment. In the figure, 20
Reference numerals 1 and 203 denote an upper substrate 27 and a lower substrate 29, respectively.
Is a rubbing axis that indicates the rubbing direction of, and these are orthogonal to each other.

The transmission axis 205 of the polarizing plate 1 and the rubbing axis 201 of the upper transparent substrate 27 are parallel to each other, and the transmission axis 207 of the polarizing plate 3 and the rubbing axis 203 of the lower substrate 29 are parallel to each other. The parts are arranged.

A liquid crystal display device having such a structure is produced,
The test pattern was displayed and the contrast characteristics were measured. The applied voltage at the time of measurement (the voltage supplied from the drive circuit 35 and applied between the transparent electrodes 31 and 33 facing each other in the liquid crystal cell 5) was set to 1 V in the bright state and 5 V in the dark state. Here, the threshold voltage of the liquid crystal layer 21 of the first liquid crystal cell 5 is 2V. The result is shown in FIG. Compared with the viewing angle characteristics of the conventional normally open liquid crystal display element shown in FIG. 4, the viewing angle characteristics are dramatically improved in all directions, and the viewing angle characteristics suitable for practical use are realized. You can confirm that. An active matrix type liquid crystal display device was manufactured using such a liquid crystal display element according to the present invention, and various image patterns were displayed to verify the display quality. It was confirmed that

Here, the viewing angle characteristics of the liquid crystal display element of the present invention can be dramatically improved to be uniform, but its theoretical explanation will be briefly described below.

As described above, FIG. 6 is a diagram showing the viewing angle characteristics of a conventional normally open TN type liquid crystal display element (hereinafter abbreviated as TN-LCD). In FIG. 6,
When tilted from 0 to 60 degrees to the left and right from the normal to the display surface (the tilt angle from the normal to the display surface is hereinafter referred to as the incident angle θ)
Shows the viewing angle dependence of the transmittance in the bright state and the dark state. Here, the normally open method refers to a method of a liquid crystal cell in which a bright state is obtained when no voltage is applied and a dark state is obtained when a voltage is applied. Comparing the dark state and the bright state, it can be seen that the dark state has a larger change in the transmittance with respect to the incident angle θ, and the viewing angle characteristic is worse than the bright state. Comparing the portion where the voltage is actually applied and the portion where the voltage is not applied in the liquid crystal cell, the dark portion to which the voltage is applied has worse viewing angle characteristics. This is due to the molecular arrangement in the liquid crystal cell. A voltage above the threshold value of the liquid crystal is applied to the dark portion, and the molecular alignment is in a state where the twisted alignment is released with the long axis of the liquid crystal molecules inclined with respect to the substrate surface. On the other hand, in the bright part, no voltage is applied and the liquid crystal molecules in the liquid crystal cell are in a state of being twisted horizontally with respect to the substrate. When a voltage is applied and the long axis of the liquid crystal molecules is tilted, the polarization plane of the light passing through the cell has been swirling due to the twisted arrangement (the twisting of the medium causes the oscillation plane of the light to rotate with respect to the traveling direction). What is called optical rotation) cannot be rotated, and remains in the direction when it enters the cell, and becomes the same as the absorption axis direction of the polarizing plate on the side where light passes through the cell, and the display is in a dark state. . According to FIG. 6, when the incident angle θ is 15 degrees to the left and right, the transmittance becomes almost 0 and no optical rotation occurs, but at an incident angle above this, the transmittance increases due to optical rotation and birefringence. Birefringence is a phenomenon in which two refracted lights are obtained when light is incident on an optical anisotropic body (medium whose refractive index varies depending on the direction). Needless to say, liquid crystal is an optical anisotropic body.
When liquid crystal molecules are obliquely arranged in a liquid crystal cell, birefringence occurs when light enters from directions other than the obliquely arranged direction. It is a key point of the technique according to the present invention to eliminate such optical rotation and birefringence in the oblique direction. By arranging a liquid crystal cell in which liquid crystal molecules are twisted and aligned in various directions between a liquid crystal cell for display and a polarizing plate, it is possible to eliminate the above-mentioned optical rotation and birefringence in an oblique direction. The present invention has found that. The liquid crystal cell for optical compensation (improving the viewing angle characteristics) has a structure in which the liquid crystal molecules are twisted and aligned substantially parallel to the substrate surface and the twist angle of the liquid crystal molecules is large so that the optical rotatory power is small. Good. It is possible to obtain a slight optical rotatory power by increasing the twist angle of the array to the extent that the optical rotation cannot be completed. The magnitude of the above-mentioned optical activity is shown by the following equation (CZVan Doorn, P
hysics Letters 42A, 7 (1973)).

F = λ / (p × Δn) (1) where λ is the wavelength of light in vacuum (wavelength in the visible wavelength range), and p is the pitch length of the twisted arrangement of the compensating liquid crystal cell. , △ n
Is the anisotropy of the refractive index of the compensating liquid crystal cell.

When f << 1, the optical rotatory power is large and the plane of polarization follows the twist of the optical axis. If a compensating liquid crystal cell under such conditions is inserted between the polarizing plate and the liquid crystal cell, the contrast ratio may be reduced, or the image may be colored, which may adversely affect the display performance contrary to the object of the present invention. become. In order to obtain a good viewing angle compensation effect, it is preferable that the optical rotatory power is as small as possible, and the liquid crystal cell for optical compensation needs to satisfy the condition of f> 1, and by rewriting the formula (1), p × Δn <λ … (2) As can be seen from the equation (2), the optical rotatory power of the liquid crystal cell is reduced by increasing the twist angle of the array, shortening the pitch p, and using a liquid crystal having a small Δn.

However, of course, even in a liquid crystal cell having such a large twist angle, the optical rotatory power depends on the incident angle, and the optical rotatory power increases at a certain incident angle. However, since it also has an azimuth angle dependency, this configuration is not suitable for actual use.
Therefore, by providing a large number of orientations in the liquid crystal layer, which have various (random) orientations having such an azimuth angle dependency of optical rotation, there is no azimuth angle dependency macroscopically, and only the incident angle We have found that an ideal liquid crystal cell for viewing angle compensation with dependence can be realized. Thereby, the viewing angle characteristic can be improved by returning the light that is transmitted through the liquid crystal cell in an oblique direction and is slightly rotated by the liquid crystal cell for compensation to the original state.

On the other hand, the increase in the transmittance due to the birefringence can be eliminated at the same time as the elimination of the optical rotatory power because the major axis of the liquid crystal molecules for compensating the viewing angle is twisted and arranged horizontally on the substrate.
The liquid crystal molecule has a different refractive index between the major axis and the minor axis, and the major axis direction has a large refractive index. The liquid crystal cell for compensation has a larger refractive index in the lateral direction than in the thickness direction of the liquid crystal layer because the liquid crystal cell is twisted in a horizontal direction with respect to the substrate. When a voltage is applied to the liquid crystal cell and the liquid crystal molecules stand up, the refractive index increases in the thickness direction of the liquid crystal layer, so when these sizes are well matched, the refractive index anisotropy becomes zero. Therefore, apparent birefringence of transmitted light does not occur. With such a principle, it is possible to obtain a display that is darker than the front even at a viewing angle from an oblique direction, and it is possible to obtain a liquid crystal display element with extremely favorable display quality in practical use, because the viewing angle characteristics have little azimuth angle dependence. Of.

On the other hand, when the twisted liquid crystal cell is used for viewing angle compensation, it is necessary to consider selective reflection. Selective reflection is a phenomenon in which only light of a specific wavelength is reflected, and it occurs at the interface having a polarization function or an optical rotation function. The value of the product n × p of the twist pitch length p of the array and the average refractive index n is visible. (JLFergason; Molecular Crystals. 1. 293 (196) in the wavelength range (360 nm to 400 nm at the short wavelength end and 760 nm to 830 nm at the long wavelength end).
6)). When selective reflection occurs, the display screen of the liquid crystal cell is colored. Therefore, if the value of n × p is out of the visible wavelength range, the above coloring phenomenon can be prevented. However, this is not the case in the case of performing color display using the selective reflection as described above (for example, using a technique of performing color display using a dichroic mirror).

(Comparative Example) A liquid crystal display device having a structure in which the second liquid crystal cell 7 was removed in the first example was prepared. Then, the viewing angle characteristic of the contrast ratio was measured in the same manner as in the first embodiment. As a result, the incident angle range in the 270 °, 30 °, and 150 ° azimuths as shown in FIG. 2 became smaller, and when gradation display was performed, the bright / dark reversal of the 90 ° azimuth display became remarkable.

(Example 2) In the first example, as the second liquid crystal cell 7 for compensating the viewing angle, a liquid crystal layer of a high molecular copolymer liquid crystal having a polysiloxane main chain and a side chain of biphenylbenzoate and a cholesteryl group was used. The liquid crystal cell used for was produced. The right-handed chiral pitch is 1.716 μm.
This material has a thickness of 0.25 in the isotropic phase on a substrate on which an alignment film for horizontal alignment is formed and which is not rubbed.
The coating was applied so as to be uniform in μm to form a viewing angle compensation plate. Using such a viewing angle compensator, an active matrix type liquid crystal display device having the other structure similar to that of the above-mentioned first embodiment was produced, and color display was performed using a color filter. It was confirmed that a good display with little light / dark reversal of the display could be obtained.

In the above, the case where a TN type liquid crystal cell is used as the first liquid crystal cell for display has been described as an example.
This is just an example, and when a liquid crystal cell having no twist angle (homogeneous alignment) is used as the first liquid crystal cell for displaying an image by applying a voltage, or a vertically aligned (homeotropic alignment) liquid crystal cell is used. Even when using
It goes without saying that an optical compensation action similar to the above can be obtained.

Needless to say, even if the present invention is applied to an active matrix liquid crystal display device using 3-terminal and 2-terminal elements such as TFT and MIM, excellent effects can be obtained.

Needless to say, various changes can be made to the material for forming each part of the liquid crystal display device of the present invention without departing from the scope of the present invention.

[0039]

As is clear from the detailed description above, according to the present invention, it is possible to improve the viewing angle characteristics of a liquid crystal display device and provide a liquid crystal display device having excellent visibility and high display quality. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display element of a first embodiment according to the present invention.

FIG. 2 is a diagram showing an optical structure of the liquid crystal display element of the first embodiment according to the present invention.

FIG. 3 is a diagram showing isocontrast characteristics of the liquid crystal display element according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining isocontrast characteristics of a conventional (and comparative example) TN cell.

FIG. 5 is a diagram showing an azimuth angle φ and an incident angle θ from an observation point in a coordinate system.

FIG. 6 is a diagram showing the incident angle dependence of the transmittance of the liquid crystal cell in the bright state and the dark state of the conventional TN type liquid crystal display element.

[Explanation of symbols]

 1, 3 ... Polarizing plate, 5 ... First liquid crystal cell, 7 ... Second liquid crystal cell

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Hato 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office

Claims (3)

[Claims] 1. A pair of substrates in which image display electrodes are arranged and are opposed to each other with a gap therebetween, and a liquid crystal layer enclosed and sandwiched in the gap between the two substrates, A first liquid crystal cell for displaying an image by applying a voltage to the image display electrode, and a second liquid crystal cell combined with the liquid crystal cell so as to be aligned with each other so that the major axis directions of liquid crystal molecules are aligned in the same direction. Two substrates that are formed so as not to be subjected to orientation treatment on the surface of the substrate and are arranged to face each other with a gap, and when the long axis direction of the liquid crystal molecules is not applied to the substrate surface. The liquid crystal molecules are held in a substantially horizontal posture, and the long-axis direction of the liquid crystal molecules is oriented in a substantially inhomogeneous direction on the substrate surface while maintaining the substantially horizontal posture. The liquid crystal molecules are twisted and aligned in the gap between the substrates, and the liquid crystal molecules are A second liquid crystal cell having a liquid crystal layer sandwiched between the two substrates so as to have different optical rotatory powers in different azimuths, the first liquid crystal cell and the second liquid crystal cell combined therewith. A liquid crystal display device comprising: two polarizing plates that sandwich the above liquid crystal cell from above and below. 2. The liquid crystal display device according to claim 1, wherein the value of the twist pitch of the alignment of the liquid crystal layer of the second liquid crystal cell is multiplied by the magnitude of the difference in the refractive index of the liquid crystal layer used for the second liquid crystal cell. A liquid crystal display device having a value shorter than the shortest visible wavelength. 3. The liquid crystal display element according to claim 1,
The liquid crystal display device according to claim 1, wherein the second liquid crystal cell is made of a polymer liquid crystal.