JPH0950026A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To realize a liquid crystal display device having high-quality display performance by improving the display performance, which greatly affects the display quality such as color reproducibility of display image, contrast characteristics, and viewing angle characteristics. A driving liquid crystal display element 9 driven to display an image and an optical axis perpendicular to the substrate surface of the driving liquid crystal display element 9 are provided. The liquid crystal cell 6 for driving has a characteristic that the directionality is negative.
Optical anisotropic element 10 placed one each on the lower side,
11 and the polarizing plate 7 on the display surface side of the two polarizing plates 7 and 8.
It is placed on the lower side, and the distribution of the scattered transmission intensity of light in a specific direction is larger than the scattered transmission intensity of light in other directions, while the light of the directions other than the specific direction goes straight and is transmitted. Light control element 12 having light scattering transmittance anisotropy
And

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 having improved contrast ratio, display color, and viewing angle characteristics during gradation display.

[0002]

2. Description of the Related Art Liquid crystal display devices have the great advantages of thinness, light weight and low power consumption, and are therefore widely used in a wide variety of products such as watches, calculators, Japanese word processors and personal computers. Most of these liquid crystal display elements use twisted nematic liquid crystals. Among them, liquid crystal display elements used in personal computers and the like are generally of large area and large capacity display, and the size of the display surface is about 10 inches diagonal or more, and the display capacity is 640 × 480 pixels or more have become mainstream.

At present, the mainstream of liquid crystal display devices for large-screen, large-capacity display is the simple matrix system. This simple matrix type liquid crystal display element has a simple structure in which liquid crystals twisted and arranged by 180 ° or more are sandwiched between electrode substrates each having a comb-shaped transparent electrode formed on a glass substrate. This is generally S
Since TN liquid crystal is used, it is called the STN system.

The STN method having such a simple structure is
In order to realize multi-digit display of × 480 pixels, the steepness of the electro-optical characteristics of the liquid crystal is required. Here, the steepness refers to the degree of change in transmitted light of the liquid crystal cell when the voltage value applied to the liquid crystal cell is changed. The steepness of the electro-optical characteristics can be improved by increasing the total twist angle of the alignment of the liquid crystal layer (hereinafter referred to as the twist angle).

Practically, the twist angle of the STN type liquid crystal display element is required to be 180 ° or more (birefringence mode), and when the twist angle becomes large like this, the display color is colored due to the birefringence phenomenon. It has been known.

As means for eliminating such coloring of display, liquid crystal molecules of a liquid crystal cell for driving (that is, a liquid crystal display panel which is driven by being connected to a driving circuit or the like for displaying an image) is arranged in a liquid crystal layer. By disposing a second liquid crystal cell (a liquid crystal cell for phase difference compensation) having a liquid crystal layer twisted in a direction opposite to the twist of the array between the polarizing plate on the display side and the driving liquid crystal cell. It has been reported, for example, in Japanese Patent Publication No. 63-53528 that a black and white display can be realized. The principle of black-and-white conversion is that the ordinary light and extraordinary light, which are elliptically polarized light transmitted through the first liquid crystal cell in which the liquid crystal molecules are arranged in a twisted array, are converted into the second liquid crystal cell which is an optical compensator. Of the elliptically-polarized light to be converted into linearly-polarized light. As a result, coloring due to the birefringence phenomenon of light is eliminated, and black and white display can be realized. The conditions required to accurately convert this elliptically polarized light into linearly polarized light are that the retardation value of the second liquid crystal cell, which is an optical compensation plate, is almost the same as that of the first liquid crystal cell (driving liquid crystal cell). Moreover, it is necessary that the twisting directions are opposite to each other and the orientation directions of the liquid crystal molecules closest to each other are orthogonal to each other.

In addition to the means using the second liquid crystal cell, that is, the liquid crystal cell for retardation compensation, a method of using an optically anisotropic film instead of the liquid crystal cell for retardation compensation has been proposed. This is a technique in which one or more optically anisotropic films are laminated on the driving liquid crystal cell to give the same function as that of the second liquid crystal cell.

By the optical compensation described above, black and white display in which coloring is eliminated is possible even in the STN system, and by further combining it with a color filter, it is possible to realize color display with higher added value.
When such a color display is performed, particularly good color reproducibility is required, and therefore it is particularly necessary to solve the coloring problem in the STN method as described above.

However, even though the coloring problem can be solved, since the simple multiplex type liquid crystal display device generally operates on the principle of time-division driving based on the voltage averaging method, the display capacity, that is, the number of pixels. Is increased (in other words, the number of scanning lines or the number of display digits is increased), the difference between the voltage value at the time of blocking light and the voltage value at the time of transmitting light cannot be sufficiently obtained, and as a result, There are essential problems such as a decrease in contrast ratio and a decrease in liquid crystal response speed.

Further, in such a conventional technique, the brightness and darkness of the display image appear to be reversed, the display image may not be seen at all, or the display may appear to be colored, depending on the azimuth and angle when viewing the screen of the liquid crystal display panel. Such phenomena have been observed, and these are major problems in realizing a liquid crystal display device with high display quality.

On the other hand, since the active matrix system is provided with a switching element composed of a thin film transistor and a diode for each display pixel, an arbitrary voltage ratio is applied to the liquid crystal layer of each pixel regardless of the number of pixels (the number of scanning lines, etc.). Can be set. Therefore, in the case of the active-matrix driving liquid crystal cell, the steepness of the electro-optical characteristics of the liquid crystal layer does not need to be as steep as in the case of the simple matrix method described above, so that the twist angle of the liquid crystal layer is It is not necessary to increase the size as in the STN method.

A liquid crystal cell having a twist angle of 90 °, so-called T
The N-type liquid crystal cell is inferior to the STN type in terms of steepness of electro-optical characteristics, but since the display principle is the optical rotatory power of light passing through the liquid crystal layer (optical rotation mode), it is relatively easy to achromatic color. A high contrast display can be obtained. It also has the advantage that the response to voltage is faster than the STN method. Therefore, by combining the TN method with the active matrix method, it is possible to realize a liquid crystal display element having a large display capacity, a high contrast ratio, and a high response speed. Furthermore, by combining with a color filter, full-color display with higher added value can be realized with high display quality.

However, even in such an active matrix type liquid crystal display device according to the prior art,
Observed as a phenomenon that the display image appears to be reversed, the display image is not visible at all, or the display looks colored depending on the direction and angle when viewing the liquid crystal display panel, and realizes a liquid crystal display device with high display quality It is a big problem to be solved in order to do so.

As means for reducing the viewing angle dependence of the display screen in such a liquid crystal display device, Japanese Patent Laid-Open No. 62-21 has been proposed.
Japanese Patent No. 423 discloses a technique of disposing a liquid crystal cell and a birefringent layer, which is a polymer film having a negative optical anisotropy in the thickness direction, between two polarizing plates.

On the other hand, in Japanese Patent Application Laid-Open No. 3-67219, a liquid crystal cell in which the liquid crystal molecules are vertically arranged (where the liquid crystal molecules are arranged vertically with respect to an alignment substrate) has a product of a spiral pitch length and a refractive index of 4
A technique of disposing a birefringent layer made of a liquid crystal compound (or polymer liquid crystal) showing a cholesteric liquid crystal phase of 00 nm or less on a liquid crystal cell is disclosed.

On the other hand, in the case of a liquid crystal cell having a twisted arrangement, a technique of disposing a liquid crystal cell made of a liquid crystal compound showing a cholesteric liquid crystal phase called UST between polarizing plates has been announced (Hato et al, Journal). of the SID, 1 / 3,19
93, p.319).

[0017]

As described above, in the conventional liquid crystal display element, basically, the orientation of the liquid crystal molecules is changed by the voltage applied to the liquid crystal, and the liquid crystal cell is optically changed. Since the display principle of causing a liquid crystal display is used, when the liquid crystal display element is tilted, the orientation of liquid crystal molecules appears to change, and as a result, the brightness and darkness of the displayed image appear to be reversed, or the image does not appear to the observer at all. There is a problem that a phenomenon such as inability to identify occurs.

In particular, when full-color display is performed in combination with a color filter, there is a problem that the display performance, which greatly affects the display quality, such as color reproducibility of display image, contrast characteristics and viewing angle characteristics, is significantly reduced. .

The present invention has been made to solve such a problem, and an object thereof is to improve display performance which is greatly related to display quality such as color reproducibility of display image, contrast characteristics and viewing angle characteristics. Then, it is to provide a liquid crystal display device which realizes high quality and good display performance.

[0020]

In the liquid crystal display device of the present invention, first, a gap is formed between a first substrate on which a first electrode is formed and a second substrate on which the second electrode is formed. A liquid crystal having a second substrate and a twisted nematic liquid crystal layer, the periphery of which is sealed and enclosed / sandwiched in a gap between the first substrate and the second substrate. A liquid crystal cell, and at least one polarizing plate disposed above and below the liquid crystal cell, respectively. The liquid crystal display device for driving, which is driven by controlling the optical rotatory power with respect to the transmitted light and displays an image, has an optical axis perpendicular to the substrate surface of the liquid crystal display device for driving, and has an optical axis different from that of the liquid crystal layer. The liquid crystal display device for driving has a characteristic that the directionality is negative. Of the optical anisotropic element arranged below and at least one of the two polarizing plates of the driving liquid crystal display element above, below, or both above and below the polarizing plate on the display surface side in a specific orientation. Light having a light scattering transmittance anisotropy that shows a distribution in which the light scattering and transmission intensity is larger than the light scattering and transmission intensity in other directions, while allowing light in directions other than the specific direction to go straight through and transmit. And a control element.

Further, in the above liquid crystal display device, the optical anisotropic element is an optical anisotropic element having a twist axis whose optical axis is an array twisted continuously in the thickness direction of the liquid crystal layer, The twist axis of the optically anisotropic element is set perpendicular to the substrate surface of the driving liquid crystal display element,
When the refractive index anisotropy of the optically anisotropic element is Δn and the twist pitch length of the optical axis is p, the value of Δn × p is smaller than the wavelength in the visible light wavelength region.

Further, in any one of the above liquid crystal display devices, the optical anisotropic element is a liquid crystal display element optically having the above characteristics.

Further, in any one of the above liquid crystal display devices, the optically anisotropic element is a polymer dispersion type liquid crystal display element having the above characteristics optically.

The present invention achieves the above object, and can simultaneously reduce the viewing angle dependence of the contrast ratio and display color of a liquid crystal display element.

That is, according to the present invention, the region where the predetermined contrast ratio of the liquid crystal display element is obtained is maintained as it is, but the predetermined contrast ratio is not obtained separately from the certain direction. In other words, the contrast ratio at the viewing angle. To improve the viewing angle characteristics from all directions over the entire screen.

In the liquid crystal display element of the optical rotation mode or the birefringence mode, light propagating in the liquid crystal display element is divided into two cases, that is, when the light is incident perpendicularly to the display surface of the liquid crystal display element and when it is incident obliquely. Will have different polarization states. This difference in polarization state is directly reflected in the phenomenon of inversion of brightness and darkness of the display image, the coloring phenomenon, and the like.

In general, such a phenomenon becomes more remarkable as the angle of viewing the display surface of the liquid crystal display device is greatly inclined from the normal to the display surface. This has means for applying a voltage to the liquid crystal layer, and a voltage is applied to the liquid crystal layer of a liquid crystal display panel (hereinafter referred to as a driving liquid crystal cell) that is driven by being connected to a driving circuit system. This is a phenomenon that is particularly noticeable in the pixel when there is.

FIG. 5 shows a conventional TN type liquid crystal display device when tilted from 0 ° to 60 ° in the left-right direction from the display surface normal (hereinafter, the tilt angle from the display surface normal is referred to as the viewing angle). It is a figure which shows the viewing angle dependence of the contrast ratio of a display image. FIG. 5 shows two cases of the normally open mode (100) and the normally closed mode (101). Here, the normally open mode liquid crystal display element is a liquid crystal display element having a structure in which a bright state is obtained when no voltage is applied and a dark state is obtained when a voltage is applied. The normally closed mode is the reverse of the normally open mode, and is a liquid crystal display device having a structure in which a dark state is obtained when no voltage is applied and a bright state is obtained when a voltage is applied. Comparing these, it can be seen that the normally closed mode has less viewing angle dependence of the contrast ratio than the normally open mode. Here, the contrast ratio is the state where light is transmitted (bright state)
Is a value obtained by dividing the brightness of the image by the brightness in the state where light is blocked (dark state), and the contrast ratio is greatly affected by the brightness in the dark state.

Then, when the viewing angle dependence of the brightness in the left-right direction in the dark state in the normally open mode and the normally closed mode is measured, the characteristics as shown in FIG. 6 are obtained. 20 in normally open mode
1 and 202 in the normally closed mode. As can be seen from the figure, the normally closed mode has a smaller viewing angle dependency in the dark state than the normally open mode, and as a result, the normally closed mode has a contrast ratio viewing angle characteristic more than that of the normally open mode. Will get better.

Considering the difference in the viewing angle characteristics in the dark state between the normally open mode and the normally closed mode, in the normally open mode, a voltage is applied to the liquid crystal cell to obtain the dark state. However, while the liquid crystal molecules are in an arrangement in which the liquid crystal molecules rise up to about 90 ° on the surface of the substrate, that is, in a vertical arrangement, the dark state in the normally closed mode is a state in which no voltage is applied to the liquid crystal cell. The liquid crystal molecules inside are arranged in a twisted state horizontally with respect to the substrate. Therefore, the difference in the viewing angle characteristics of these modes is caused by the difference in the molecular alignment state of the liquid crystal cell, and the vertical alignment state has a worse viewing angle characteristic than the horizontally twisted alignment state.

For example, when a liquid crystal cell in a vertically aligned state is represented by a three-dimensional refractive index ellipsoid, a refractive index ellipsoid 301 as shown in FIG. 7 is obtained. Here, the z-axis in the drawing is the thickness direction of the liquid crystal cell, and the xy plane corresponds to the substrate surface of the liquid crystal cell. The birefringence phenomenon is a refractive index ellipse whose normal is the visual axis 302 connecting the observation point and the central point of the refractive index ellipsoid 301 when the central point of the refractive index ellipsoid 301 is observed from a certain direction. The normal line on the center point of the body 301 is the index ellipsoid 3.
It is indicated by the shape of an elliptical cut surface formed when cutting 01 (here, referred to as a two-dimensional in-plane refractive index body 303). If the difference between the long axis and the short axis of the refractive index body 303 in this two-dimensional plane corresponds to the phase difference between ordinary light and extraordinary light, and the transmission axes of the polarizing plates sandwiching the liquid crystal cell are orthogonal to each other. ,
When the phase difference is zero, the transmitted light of the liquid crystal cell is blocked, and when the phase difference is not zero, the transmitted light corresponding to the phase difference and the wavelength of the incident light is generated. When light is incident perpendicularly to the substrate surface of the liquid crystal cell (that is, when the liquid crystal cell is viewed from directly in front), the refractive index body in the two-dimensional plane is a circle 304, and the phase difference between ordinary and extraordinary light is Although it is zero, when light in a direction inclined from the substrate surface of the liquid crystal cell, for example, the direction of the visual axis 302 is incident, the refractive index body 303 becomes an ellipse, and the phase difference between the ordinary ray and the extraordinary ray occurs, causing a direct frontal view. The polarization state of light passing through the liquid crystal cell is different between the direction and the oblique direction. Therefore, the coloring phenomenon based on the phase difference occurs in the case of elliptically polarized light.

Therefore, in order to improve the viewing angle characteristics of the liquid crystal cell, it is necessary to improve the refractive index ellipsoid of the liquid crystal cell when a voltage is applied.

The main concept of the theory of improving the viewing angle characteristic will be described below based on the refractive index ellipsoid 301 in the vertically arranged state shown in FIG.

As the viewing angle of the refractive index ellipsoid 301 in FIG. 7, that is, the viewing angle 305 is increased, the refractive index body 303 in the two-dimensional plane of the visual axis 302 increases in the longitudinal direction of the major axis 306, Transmitted light having a larger phase difference than when viewed from the direction of the visual axis 302 is observed.

However, ideally, when the viewing angle is changed, the refractive index body 303 in the two-dimensional plane can be seen from any direction.
It is desirable that the shape of does not change. In order to optically compensate for such a property that the phase difference of light changes depending on the viewing angle, a disc-shaped index ellipsoid 40 as shown in FIG. 8 is used.
The optical anisotropic plate having the negative optical anisotropy having the optical characteristics as shown in 1 has an index ellipsoid 401 whose z axis is as shown by the index ellipsoid 301 shown in FIG. It is considered that this can be realized by arranging the liquid crystal cell having optical characteristics so as to coincide with the z-axis of the refractive index ellipsoid 301 in the same direction. That is, it should be realized by disposing the optically anisotropic plate having the optical characteristics represented by the refractive index ellipsoid 401 adjacent to the upper layer or the lower layer of the driving liquid crystal cell. By doing so, even when the viewing angle 305 is increased, the refractive index body 303 in the two-dimensional plane of the refractive index ellipsoid 301 becomes large in the longitudinal direction of its major axis 306. The refractive index of the minor axis 307 in the length direction increases. As a result, in the two-dimensional refractive index body 303 in the light related to the display that is synthesized and appears on the display surface side.
Becomes linearly polarized light. Therefore, by using the negative optical anisotropic plate having the optical characteristics represented by the refractive index ellipsoid 401 as described above, the refractive index ellipsoid 30 of the driving liquid crystal cell is used.
1 can be optically compensated, and the viewing angle characteristics should be dramatically improved. In practice, the refractive index ellipsoid as shown in FIG. 8 includes an optically anisotropic film (optically anisotropic layer) formed by using an optically anisotropic substance in which the optical axes are continuously twisted. Should be realized by the optical anisotropic element.

However, in general, the driving liquid crystal cell displays an image by positively changing the polarization direction of light in the visible wavelength region (generally, the region from 380 nm to 750 nm) by the voltage applied to the liquid crystal cell. However, in the case of the optical anisotropic element for optical compensation as described above, since the optical axis of the optical anisotropic element is continuously twisted, optical rotatory power may be caused depending on the optical condition of the optical anisotropic element. May occur. Here, the optical rotatory property refers to a property in which, as the light travels in the medium, the vibration direction of the light turns to the left or right around the traveling direction as an axis.

When the retardation value of an optical anisotropic element in which the optical axis is continuously twisted is constant and the twist pitch of the optical axis is long, the light rotates its polarization plane according to the twist of the optical axis. If the twist pitch of the shaft is short,
Light cannot follow the twist of its optical axis, and the optical rotation phenomenon does not occur. If the optical anisotropy of the optical anisotropic element is large, the polarization plane of the light passing through the element is changed, and as a result, the contrast ratio is reduced, and in some cases, the polarization plane is changed depending on the wavelength of the light. As a result, there arises a problem that the light transmitted through the optically anisotropic element is colored. Therefore, it is necessary that at least the optical rotatory power of the optically anisotropic element with respect to visible light is smaller than the optical rotatory power of the driving liquid crystal cell with respect to visible light. This optical rotatory power largely depends on the wavelength of light that passes through the medium and the medium through which the light passes. The magnitude of the optical rotatory power is represented by the degree of change of the retardation value of the medium with respect to the change of the optical axis. Therefore,
The magnitude of the optical rotatory power of the driving liquid crystal cell is
The difference between the refractive index no for ordinary light and the refractive index ne for extraordinary light is Δn1 (= ne-no: refractive index anisotropy), the thickness of the liquid crystal layer is d1, and the twist alignment angle of the liquid crystal layer (twist angle) is T1. Then, .DELTA.n1 .multidot.d1 / T1 = R1 / T1 where R1 = .DELTA.n1 .d1 (retardation value) (1.1) Similarly, the magnitude of the optical rotatory power of the optically anisotropic element for phase difference compensation depends on the refractive index anisotropy of the optically anisotropic material of the optically anisotropic element is Δn2, and the thickness of the laminated optically anisotropic material layer. Where d2 is the total twist angle of the optical axis of the optically anisotropic substance layer, and T2 is Δn2.d2 / T2 = R2 / T2, where R2 = .DELTA.n2.d2 (1.2). Therefore, the magnitude relationship between the optical rotatory power of the optical anisotropic element for phase difference compensation and the optical rotatory power of the driving liquid crystal cell is
From equations (1.1) and (1.2), it can be seen that (R1 / T1)> (R2 / T2) ... (1.3).

When the optical axis of the optical anisotropic element is continuously twisted, the propagation of light inside the optical anisotropic element can be expressed by the parameter shown by the following equation (CZVan Doorn, Rh
ysics Letters 42A, 7 (1973)). f = λ / (p × Δn), where λ is the wavelength of light in vacuum (visible wavelength range), p is the twist pitch length of the optical axis (p = d / T) (1.4) f << In the case of 1, the polarization plane of the light in the optical anisotropic element changes in accordance with the twist angle of the optical axis and has optical rotatory power. As described above, the optical anisotropic element preferably has a small optical rotatory power, and the optical anisotropic element needs to satisfy the condition of f >> 1. Therefore, it is deduced from the formula (1.4) that the optical anisotropic element needs to satisfy p × Δn <λ (1.5).

By the way, a liquid crystal having a very large twist angle, that is, a liquid crystal having a short spiral pitch length is generally called a cholesteric liquid crystal. The product n of the spiral pitch length p and the average refractive index n of this cholesteric liquid crystal is used. The value of × p is
In the visible wavelength range (this range varies depending on the conditions, but the short wavelength end is about 360 nm to 400 nm, and the long wavelength end is
Selective reflection occurs (JLFergason; Molecular Crystals.1.293 (196 nm to 830 nm)).
6)).

Such a phenomenon is not a phenomenon observed only in a cholesteric liquid crystal cell, but can generally occur in an optically anisotropic element in which the optical axis of an optically anisotropic body is continuously twisted. When this selective reflection occurs, a coloring phenomenon of the optically anisotropic element occurs and the display color changes. Therefore, if the product n × p of the average refractive index n of the optically anisotropic substance forming the optically anisotropic element and the twist pitch p of the optical axis is excluded from the visible wavelength range, the coloring phenomenon can be prevented. can do.

However, although the principle of the viewing angle control has been conceptually described above, the refractive index ellipsoid of the driving liquid crystal cell to which a voltage higher than the threshold voltage at that time is applied is actually shown in FIG. It is not a simple ellipsoidal shape as shown in 7. TN
When a voltage having a value capable of obtaining a dark state is applied to the driving liquid crystal cell of the method, the molecular alignment state in the liquid crystal cell actually becomes a state shown by a curve as shown in FIG. FIG.
Curves 7 and 8 therein indicate a tilt angle and a twist angle, respectively. Here, as shown in FIG. 10, the tilt angle is the tilt angle 603 of the major axis 602 of the liquid crystal molecules 601 with respect to the xy plane when the display surface of the liquid crystal cell, that is, the display-side substrate main surface is the xy plane. The twist angle means that the long axis 602 of the liquid crystal molecule 601 is x from the z-axis direction.
An angle 604 formed by the projection projected on the y-plane and the x-axis.

When a voltage is applied, the liquid crystal molecules are tilted almost 90 ° (vertically) near the center of the liquid crystal cell in the thickness direction, but near the upper and lower substrate surfaces, the influence of the alignment regulating force of the substrate surface As a result, the liquid crystal molecules do not actually tilt much. At this time, the twist angle between the upper and lower substrates is S
The distribution is in the shape of. As is apparent from this, the molecular alignment of the liquid crystal layer when a voltage is applied is not in a completely vertical alignment state. Such an array state has a great adverse effect on the viewing angle characteristics.

FIG. 11 is a diagram showing a viewing angle characteristic in a dark state of a normally open mode TN mode liquid crystal display device to which a voltage higher than a threshold voltage is applied. This is shown in FIG.
In the coordinate system as shown in Fig. 2, the liquid crystal display element is placed in four directions of up, down, left and right, that is, the azimuth angle φ is 0 ° (right azimuth), 90 °
(Upward azimuth), 180 ° (left azimuth), and 270 ° (lower position) are the results of measuring the transmittance of the liquid crystal cell when the viewing angle θ was changed from 0 ° to 60 °. From FIG. 12, the viewing angle transmittance curves of the upper-lower position and the left-right direction do not match. Also, comparing the upper direction and the lower position,
The same angle (that is, except for the azimuth such as the vertical direction of the viewing angle,
It can be seen that the transmittance greatly differs with respect to the angle value which is the absolute value of the viewing angle.

On the other hand, in the case of a vertically aligned liquid crystal cell,
As shown in FIG. 13, the viewing angle transmittance curves in the upper azimuth and the lower azimuth, and the left azimuth and the right azimuth are substantially the same in the mutually opposite azimuths.

When a voltage is applied to the driving liquid crystal cell having the twisted arrangement, the refractive index ellipsoid of the driving liquid crystal cell is
7 is not a simple shape as shown in FIG. 7, but is actually a shape obtained by deforming FIG. 7 due to the influence of the tilt of liquid crystal molecules near the center of the liquid crystal cell and the twist alignment portion near the substrate surface. (Not shown).

Therefore, as the refractive index ellipsoid for optical compensation which can be preferably used for the driving liquid crystal cell of the TN system or the STN system, in order to adapt to the refractive index ellipsoid of the driving liquid crystal cell. It is desirable that the disk shape is not a perfect (in other words, theoretical or ideal) disk shape as shown in FIG. 8, but a slightly deformed complicated shape.

FIGS. 14, 15 and 16 show a liquid crystal display similar to the case shown in FIGS. 11 and 13, in which an optical anisotropic element is arranged between two polarizing plates whose transmission axes are orthogonal to each other. The visual angle characteristics of the entire device are measured. As the optically anisotropic element, a liquid crystal cell using a chiral nematic liquid crystal was prepared and used. The Δn is 0.039
The liquid crystal layer thickness is 12 μm, and the pitch p is 0.248 μm in the case shown in FIG. 14 and 0.73 in the case shown in FIG.
8 μm, the case of the one shown in FIG. 16 is 5.3 μm,
The twist angles are 48.25 rotations and 16.25 rotations, respectively.
It is 2.25 revolutions. It should be noted that the vertical direction is shown by a cross mark and the horizontal direction is shown by a good circle mark. It can be seen from FIGS. 14, 15 and 16 that when the twist angle is small, the transmittance in the vertical and horizontal directions is different, and when the twist angle is large, the transmittance in the vertical and horizontal directions is the same. This indicates that the refractive index ellipsoid of the optical anisotropic element becomes a perfect disc shape when the twist angle is large, and the disc shape becomes distorted when the twist angle is small.

Now, the visual angle improving effect of the present invention is shown in FIG.
Although it can be exhibited under any of the conditions shown in 15 and 16, the refractive index ellipsoid of the driving liquid crystal cell when a voltage is applied is theoretically geometrically accurate as described above. It is considered that the shape is more distorted than that of an ellipsoid, so that the effect should be more exhibited if the refractive index ellipsoid of the optical anisotropic element to be overlaid is also distorted correspondingly.

That is, the characteristic in the case where the rotation number of the optical rotation in the optically anisotropic element is made relatively small is actually more desirable.

As described above, when the rotation number of the optical rotation in the optical anisotropic element is small, the pitch p becomes long. On the other hand, since the refractive index n of the optically anisotropic element is 1.5 in the above case, the condition for n × p described above is that the value of n × p is equal to or longer than the long wavelength end of the visible wavelength range. Is more
It can be said that it is more preferable.

In the present invention, the optical conditions of the optically anisotropic element, the retardation value represented by Δn × d (d is the thickness of the liquid crystal layer), the rotation number of the optical rotation, and the tilt angle of the optical axis with respect to the spiral axis. Also, the effect is changed by changing the rotation direction or the direction of the optical axis of the optically anisotropic substance in the optically anisotropic element from the outside. In particular, regarding the rotation direction, the effect is greatly different depending on whether the rotation direction of the optical axis of the optical anisotropic element and the twisting direction of the driving liquid crystal cell are the same or opposite.

The retardation compensator having negative optical anisotropy described above should exert a great effect in the case of binary display. This is because there is only one tilt of the liquid crystal molecule when a voltage is applied. That is,
This is because the display state of each pixel changes depending on the binary value of ON / OFF.

However, in the case of a liquid crystal display device that realizes gradation display of a plurality of gradations by changing the inclination of liquid crystal molecules, the above effect of improving the viewing angle is still insufficient. It can be said that there is.

FIG. 17 shows the luminance-visual angle characteristics at the time of 8-gradation display in the conventional normally open mode TN type liquid crystal display device which performs such gradation display.

Regarding the horizontal azimuth (FIG. 17A), even if the incident angle is 40 °, the gradation luminance values remain in the frontal order. In other words, it can be said that the practical viewing angle is maintained up to about 40 °. On the other hand, the vertical direction (Fig. 17
Regarding (b)), the order of the gradation luminance has already been changed especially when the incident angle is about 10 ° in the downward direction,
It can be seen that the gradation display property is greatly impaired especially in the downward direction.

Such a normally open mode TN
FIG. 18 shows the viewing angle characteristics of the liquid crystal display device when the negative optical anisotropic element having the optical characteristics shown in FIG. 8 is arranged between the polarizing plate and the liquid crystal cell of the liquid crystal display element. . In this case, regarding the left and right azimuth (FIG. 18A),
The luminance at the gradation level 8 has less change depending on the incident angle as compared with the case of FIG. On the other hand, regarding the vertical direction,
In the upper azimuth, the luminance rank among the gradations is kept uniform even if the incident angle is increased, and it is thought that it can be realized to achieve sufficiently good display, but in the lower portion, there is a significant decrease in luminance, and the lower 10
It can be seen that the brightness has already been remarkably reversed at ~ 20 °. It can be said that this is because the viewing angle characteristics are worse than in the case where the optical anisotropic element as shown in FIG. 17 is not used. In the liquid crystal display device having such a viewing angle characteristic,
Since the viewing angle characteristics are extremely poor, it is extremely difficult to realize good display.

As described above, the reason why the viewing angle characteristic is further deteriorated is that the liquid crystal molecules are tilted by about 90 ° near the center of the liquid crystal cell in the thickness direction, as described above. In the vicinity of the upper and lower substrate surfaces, the liquid crystal molecules do not tilt much under the influence of the alignment regulating force of the substrate surface, and the distribution of the twist angle of the liquid crystal molecules continuous in a spiral plane from the lower substrate to the upper substrate of the liquid crystal molecules is seen. , S-shaped distribution, and it is considered that this is because the distribution of the twist angle of the S-shaped actually causes a difference in the phase difference generated in the transmitted light depending on the viewing angle azimuth.

Therefore, in the case of the liquid crystal display device as exemplified above, the lowering of the lower luminance and the poor viewing angle dependency of the contrast characteristic are improved by the present invention, thereby significantly improving the display quality. be able to.

In other words, to generalize the above example, it is necessary to improve the brightness and contrast characteristics of the azimuth particularly in the viewing angle region (lower position in the above example) where the brightness and contrast characteristics are particularly poor. According to the present invention, for example, a light control element having a diffractive action is used as a specific means for realizing the above. The characteristics of the light control element used in the present invention are transparent to the transmitted light in the front direction, and are particularly effective for light in the viewing angle region in which the brightness and contrast characteristics in the oblique direction, particularly the above-described lower azimuth, are particularly poor. On the other hand, by introducing light in a specific angle area, scattering it, and emitting it, it is possible to increase the brightness and contrast characteristics of the azimuth corresponding to the emission angle area where the aforementioned brightness and contrast characteristics are poor. Function. In the structure of this light control element, a layer having a different refractive index is formed in a specific direction, and light having an angle substantially parallel to the layer to a specific angle region is scattered by a diffracting action. Therefore, the emitted light has an appropriate spread. On the other hand, since it has a uniform refractive index in the front direction, it is in a transparent state in the front direction and the light travels straight. Therefore, according to the present invention, the light control element (light control element) that selectively scatters the emitted light only in a specific direction (with a width of a certain angle region) and transmits the light of other angles in a straight line according to the present invention. By using a film or the like), it is possible to realize a liquid crystal display device having excellent visibility by preventing a decrease in luminance in a specific direction.

The driving liquid crystal cell of the TN system has been described above as an example. However, since the optical compensation system of the present invention is based on the principle of optically anisotropic, the driving liquid crystal cell has a twist angle. It goes without saying that the same effect can be exhibited not only in the case of the TN method of about 90 ° but also in the case of the STN method having a twist angle of 180 ° or more.

Further, the optically anisotropic element is formed by laminating a retardation film in which optical anisotropy is generated by stretching a polymer film, a twisted liquid crystal cell, and a polymer. It can also be realized by a thin film in which liquid crystal is twisted and aligned. In this case, for example, by coating this polymer layer on at least one of the substrates of the driving liquid crystal cell, the optical anisotropic element according to the present invention can be obtained. Also, in terms of manufacturing process, it is more desirable because it can be easily manufactured.

For example, a polymer copolymer having a polysiloxane main chain and having biphenylbenzoate and cholesteryl groups in side chains at an appropriate ratio can be used.

[0063]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a liquid crystal display device of the present invention will be described below in detail with reference to the drawings.

(First Embodiment of the Invention) FIG. 1 is a sectional view showing the outline of the structure of a liquid crystal display device according to the first embodiment of the present invention.

In this liquid crystal display device, the first substrate 2 on which the first electrode 1 is formed and the second substrate 2 on which the second electrode 3 is formed and which is opposed to the first substrate 2 with a gap. Substrate 4 of
A twisted nematic liquid crystal layer 5 which is sealed and sandwiched around the periphery in the gap between the first substrate 2 and the second substrate 4.
And a driving liquid crystal cell 6 having
It has two polarizing plates 7 and 8 arranged one below each, and when a liquid crystal applied voltage is applied, the optical activity for transmitted light is controlled based on the orientation change of liquid crystal molecules of the liquid crystal layer 5. A liquid crystal display element 9 for driving which displays an image and an optical axis which is perpendicular to the substrate surface of the liquid crystal display element 9 for driving and has a negative optical anisotropy contrary to the liquid crystal layer 5. Of the two polarizing plates 7 and 8 of the driving liquid crystal display element 9 and the optical anisotropic elements 10 and 11 arranged one above and one below the driving liquid crystal cell 6. Polarizing plate 7
The scattered transmission intensity of light in a specific orientation, which is arranged on the lower side, shows a distribution larger than the scattered transmission intensity of light in other directions, while the light in the orientation other than the specific orientation goes straight. And a light control element 12 having a diffractive action, which has a light scattering transmittance anisotropy for transmission.

The two polarizing plates 7 and 8 (SH-1832AP; manufactured by Sumitomo Chemical Co., Ltd.) are not attached directly above and directly below the driving liquid crystal display element 9, but these two sheets are not attached. Between the polarizing plates 7 and 8, the optical anisotropic elements 10 and 11 which are liquid crystal cells for viewing angle compensation and the driving liquid crystal cell 6 which is driven to display an image are arranged so as to be sandwiched therebetween. There is. Here, the polarizing plate 7 is composed of two thin transparent substrates 7 which are protective layers.
It is formed by sandwiching the polarizing film 7a inside b, and the polarizing plate 8 is also similarly formed by sandwiching the polarizing film 8a between the transparent substrates 8b.

A scattering angle region of outgoing light is 0 ° between the polarizing plate 7 and the negative optical anisotropic element 10 as described above.
Light control element 12 (LUMIST with scattering characteristics of ~ 30 °
Y; Sumitomo Chemical Co., Ltd.) is located. The light control element 12 has a distribution in which the scattered transmission intensity of light in a specific azimuth has a distribution larger than the scattered transmission intensity of light in the other directions, while the light in the azimuths other than the specific azimuth goes straight through and is transmitted. It is an element having a light scattering transmittance anisotropy and having a diffracting action. Therefore, by arranging the specific azimuth direction so as to face the angle region where the viewing angle characteristic of the liquid crystal display device is bad, the viewing angle characteristic (that is, the brightness and the contrast characteristic) of the angle region can be improved. .

Further, an antireflection layer 13 (Technoloy laminated with Y ₂ O ₃ / TiO ₂ / SiO ₂ ; manufactured by Sumitomo Chemical Co., Ltd.) is installed adjacent to the polarizing plate 7.

The negative optical anisotropic elements 10 and 11 use liquid crystal cells and have a retardation value of 134 in the thickness direction.
nm. The optical anisotropic elements 10 and 11 are so-called optical retardation plates.

FIG. 2A is an exploded perspective view showing the outline of the structure of the liquid crystal display device in this example.

In the figure, arrows (1.1) and (4.1) are the transmission axes of the polarizing plates 7 and 8, respectively, which are orthogonal to each other. And (1.1) is arranged in the 135 ° direction counterclockwise when viewed from the + z direction with respect to the y axis. Arrows (3.1) and (3.2) indicate the upper and lower substrates 2 and 4 of the driving liquid crystal cell 6.
The rubbing axes of the alignment films (not shown) arranged on each of them are orthogonal to each other, and the angle formed by the rubbing axis (3.1) with respect to the y axis is 45 ° counterclockwise when viewed from the + z direction.
It is located in.

The viewing angle characteristics of the liquid crystal display device of this example are shown in FIG.
It measured using the coordinate system as shown in FIG. The voltage value at the time of the measurement, that is, the driving power source 14 to the driving liquid crystal display element 9
The voltages applied between the electrodes 1 to 3 are selected from eight types of voltages so that equal luminous efficiency can be obtained in front of the driving liquid crystal display element 9, and as a result, display of eight gradations is performed. did. The result is shown in FIG.

The viewing angle characteristic of FIG. 18 showing an example of the conventional liquid crystal display device is 10 ° to 20 ° in the lower position as described above.
Although it was so bad that bright / dark reversal occurred at 0 °, in comparison with this, in the case of the present invention, as is apparent from FIG. 3, the viewing angle characteristic in the lower position is greatly improved,
The viewing angle at which a good display can be observed has improved to over 40 °. Also, it can be seen that a sufficient wide viewing angle is realized in other upward and horizontal directions.

Regarding the display color, in the past, the display color in the dark state was colored in particular when the viewing angle was changed, whereas in the liquid crystal display device of the first embodiment according to the present invention, the viewing angle was changed. It was confirmed that a good black display color could be obtained even when was changed.

Actually, in the liquid crystal display device having the above-mentioned structure according to the present invention, a color filter is arranged in the driving liquid crystal display element 9 and the T size is 10 inches diagonally.
An FT type liquid crystal display device is created, and the driving circuit 14
The display quality of the image was visually confirmed. As a result, even if the observation azimuth and viewing angle are changed, not only the contents of the gradation display image observed on the display screen can be sufficiently identified, but also there is no color reversal or coloring that deteriorates the image quality, which is extremely good. It was confirmed that excellent full-color display was obtained.

(Second Embodiment) FIG. 4 is a sectional view showing the outline of the structure of a liquid crystal display device according to a second embodiment of the present invention. The same parts as those in FIG. 1 of the first embodiment are designated by the same reference numerals.

In the liquid crystal display device of this example, the polarizing plate 7
And the liquid crystal cell 210 for compensating the viewing angle, which is an optically anisotropic element, between the light control element 5 (LUMIST) with a scattering angle region of 0 ° to 30 °.
Y; Sumitomo Chemical Co., Ltd.) is located.

An antireflection layer 13 is provided on the polarizing plate 7.
(Technoloy in which Y ₂ O ₃ / TiO ₂ / SiO ₂ is laminated; manufactured by Sumitomo Chemical Co., Ltd.) is installed. That is, the antireflection layer 13 is the polarizing plate 7 in the first embodiment.
It is also used as a transparent substrate 7b which is a protective layer on the upper side of the.

The viewing angle compensating liquid crystal cell 210 is arranged so as to be sandwiched between the polarizing plates 7 and 8 together with the driving liquid crystal cell 6. This viewing angle compensating liquid crystal cell 210
Is a liquid crystal layer 210c between the transparent substrates 210a and 210b.
Are formed in a liquid crystal cell structure in which is enclosed and sandwiched. As the liquid crystal layer 210c, a twisted nematic liquid crystal (ZLI-2806 (manufactured by E. Merck Co., Itd)) and a chiral agent S811 are used.
(Mixed with E. Merck Co., Itd) has a helix angle of 9
It is enclosed at 90 °, and the liquid crystal molecules inside are enclosed by the lower substrate 2.
A counterclockwise (left-handed) twist arrangement is made from 10b to the upper substrate 210a. The Δn of the liquid crystal material used as the liquid crystal layer 210c of the viewing angle compensation liquid crystal cell 210 is
The thickness is 0.039, the spiral pitch is 3.27 μm, and the liquid crystal layer thickness is 9 μm.

The driving liquid crystal cell 6 is arranged between the viewing angle compensating liquid crystal cell 210 and the polarizing plate 8. Transparent electrodes 1 and 3 are formed on the upper substrate 2 and the lower substrate 4, respectively, and they are connected to a driving power supply 14.
The twisted nematic liquid crystal (ZL
I-4287 (E. Merck Co., Itd) with chiral agent S811 (E. Mer
ck Co., Itd Co., Ltd.)) is mixed and sandwiched at a twist angle of 90 °, and the orientation state changes according to the voltage applied from the driving power supply 14. The liquid crystal layer 2 of the driving liquid crystal cell 6
The liquid crystal composition used in 10c had a Δn of 0.093 and a liquid crystal layer thickness of
5.5 μm. The liquid crystal molecules in the driving liquid crystal cell 6 are arranged counterclockwise (to the left) in a twisted arrangement from the lower substrate 4 to the upper substrate 2.

FIG. 2B is an exploded perspective view showing the outline of the structure of the liquid crystal display device in this example.

In the figure, arrows (1.1) and (4.1) indicate the transmission axes of the polarizing plates 7 and 8, respectively, which are orthogonal to each other. And (1.1) is arranged in the 135 ° direction counterclockwise when viewed from the + z direction with respect to the y axis. Arrows (3.1) and (3.2) indicate the upper and lower substrates 2 and 4 of the driving liquid crystal cell 6.
The rubbing axes of the alignment films (not shown) arranged on each of them are orthogonal to each other, and the angle formed by the rubbing axis (3.1) with respect to the y axis is 45 ° counterclockwise when viewed from the + z direction.
It is located in. The rubbing axis (2.1) of the upper substrate and the rubbing axis (2.2) of the lower substrate of the viewing angle compensation liquid crystal cell 210 are orthogonal to each other, and the rubbing axis (2.1) is the rubbing axis of the driving liquid crystal cell 6. It is placed parallel to (3.1). The transmission axis (1.1) of the polarizing plate 7 is arranged parallel to the rubbing axis (2.1) of the upper substrate of the viewing angle compensation liquid crystal cell 210.

The polarizing plate 7 is arranged so that the transmission axis (1.1) is parallel to the rubbing axis of the viewing angle compensating liquid crystal cell 210. And comparing the optical activity of both liquid crystal cells 210 and 6, it becomes as follows.

The optical rotatory power of the driving liquid crystal cell 6 is such that the difference between the refractive index no of the driving liquid crystal cell 6 for ordinary light and the refractive index ne of extraordinary light is Δn1 (= ne-no: refractive index anisotropy), Assuming that the thickness of the liquid crystal layer is d1 and the twisted arrangement angle (twist angle) of the liquid crystal layer is T1, Δn1 · d1 / T1
= R1 / T1, where R1 = .DELTA.n1.d1 (retardation value)
It can be represented by (1.1). Similarly, the optical rotatory power of the viewing angle compensating liquid crystal cell 210, which is an optical anisotropic element for phase difference compensation, depends on the refractive index anisotropy of the liquid crystal layer as the optically anisotropic substance, Δn 2, and the thickness of the liquid crystal layer. D
2. Letting T2 be the total twist angle of the optical axis of the liquid crystal layer, Δn2 · d2 / T2 = R2 / T2, where R2 = Δn2 · d2 (1.2).

After being defined in this way, both liquid crystal cells 2
Comparing the optical rotatory powers of 10 and 6, R1 / T1 = 0.5115 μm / 90 ° = 5.6833 [nm / de
g], the compensating liquid crystal cell is R2 / T2 = 0.351 μm / 990 ° = 0.3545 [nm / de from equation (1.2).
g] and the relationship between the two is (R1 / T1)> (R2 / T2). When substituting a specific numerical value into the above equation and calculating, the optical activity of the viewing angle compensation liquid crystal cell 210 is
1/10 or less.

The viewing angle characteristics of the liquid crystal display device of this example were measured in the same manner as in the first example. As a result, the first
Similar to the example, it was confirmed that the viewing angle characteristics in the lower position were greatly improved, and that the viewing angle at which a good display was observable was improved to 40 ° or more. Also, it was confirmed that a sufficient wide viewing angle was achieved in other upward and horizontal directions.

Regarding the display color, the display color in the dark state is colored in the past when the viewing angle is changed, whereas in the liquid crystal display device of the first example according to the present invention, the viewing angle is changed. It was confirmed that a good black display color could be obtained even if the color was changed.

In the liquid crystal display device having the above-described structure according to the present invention, a color filter is disposed in the driving liquid crystal display element 9 and a T-size screen having a diagonal of 10 inches is used.
An FT type liquid crystal display device is created, and the driving circuit 14
The display quality of the image was visually confirmed. As a result, even if the observation azimuth and viewing angle are changed, not only the contents of the gradation display image observed on the display screen can be sufficiently identified, but also there is no color reversal or coloring that deteriorates the image quality, which is extremely good. It was confirmed that excellent full-color display was obtained.

(Comparative Example) In the liquid crystal display device of the first example, the contrast characteristic was measured in the liquid crystal display device of the conventional structure from which the light control element was removed. As a result, it was revealed that the lower level of luminance was severely reduced.

In each of the above examples, the case of the TN type liquid crystal display device is described, but the present invention is not limited to this. It goes without saying that the present invention can be applied to, for example, an STN type liquid crystal display device. Also,
INDUSTRIAL APPLICABILITY The present invention can be applied to an active matrix type liquid crystal display device using a TFT element which is a three-terminal element, an active matrix type liquid crystal display apparatus using an MIM element which is a two-terminal element, and the like. Alternatively, it is also applicable to a simple matrix type liquid crystal display device. In any of these cases, it goes without saying that the same remarkable effect of improving the contrast characteristics as in the above examples can be obtained.

At this time, in the present invention, basically, by using a light control element having a diffractive action at a light emission angle which complements light in an azimuth in which contrast characteristics and brightness are observed to be low, The viewing angle characteristics of can be significantly improved as specified above. Therefore, for details such as the specifications of the light emission angle and the scattering angle region by diffraction as the light control element according to the present invention, the driving liquid crystal cell used with the light control element according to the present invention and the optical element for phase difference compensation are used. Determined in each case by an anisotropic element, etc., since it varies variously depending on the viewing angle dependence of the display screen as the entire liquid crystal display device, in accordance with the gist of the present invention clearly described in the description of each of the above examples and the operation of the present invention, In order to supplement the light in the azimuth of the viewing angle region showing particularly poor contrast characteristics and brightness in the viewing angle, the light emission angle and the scattering angle region by diffraction as the light control element according to the present invention may be set.

[0092]

As described above in detail, according to the present invention, it is possible to improve the display performance, which is greatly related to the color reproducibility of the display image, the display characteristics such as the contrast characteristics and the viewing angle characteristics, and to improve the high performance. It is possible to provide a liquid crystal display device that realizes good display performance with high quality.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of the structure of a liquid crystal display device according to a first embodiment of the present invention.

2A is an exploded perspective view showing the outline of the structure of the liquid crystal display device according to the first embodiment, and FIG. 2B is the structure of the liquid crystal display device according to the second embodiment. It is an exploded perspective view showing an outline.

FIG. 3 is a diagram showing a result of measuring a viewing angle characteristic of the liquid crystal display device according to the first embodiment.

FIG. 4 is a sectional view showing an outline of the structure of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a viewing angle dependence of a contrast ratio of a display image when the liquid crystal display element of the conventional TN system is tilted in the left and right directions from 0 ° to 60 ° from a display surface normal.

FIG. 6 is a diagram showing the measurement results as an example of the viewing angle dependence of the luminance in the dark state in the normally open mode and the normally closed mode in the left-right direction.

FIG. 7 is a diagram showing an index ellipsoid of a vertically aligned liquid crystal cell.

FIG. 8 is a diagram showing an index ellipsoid of an optically anisotropic plate for optical compensation.

FIG. 9 is a diagram showing a molecular alignment state in a liquid crystal cell when a voltage having a value capable of obtaining a dark state is applied to the driving liquid crystal cell of the TN system.

FIG. 10 is a diagram showing definitions of general tilt angle and twist angle.

FIG. 11 is a diagram showing viewing angle characteristics in a dark state of a normally open mode TN mode liquid crystal display device to which a voltage equal to or higher than a threshold voltage is applied.

FIG. 12 is a diagram showing a general definition of a coordinate system when measuring a viewing angle characteristic.

FIG. 13 is a diagram showing viewing angle-transmittance curves in a vertical direction and a horizontal direction in the case of a vertically aligned liquid crystal cell.

FIG. 14 is a diagram showing the results of measuring the viewing angle characteristics of the entire liquid crystal display device by disposing an optically anisotropic element between two polarizing plates whose transmission axes are orthogonal to each other.

FIG. 15 is a diagram showing the results of measuring the viewing angle characteristics of the entire liquid crystal display device by disposing an optically anisotropic element between two polarizing plates whose transmission axes are orthogonal to each other.

FIG. 16 is a diagram showing the results of measuring the viewing angle characteristics of the entire liquid crystal display device by disposing an optically anisotropic element between two polarizing plates whose transmission axes are orthogonal to each other.

FIG. 17 shows a luminance-visual angle characteristic at the time of 8-gradation display in a conventional normally open mode TN type liquid crystal display device which performs gradation display.

FIG. 18 is a diagram showing viewing angle characteristics of a conventional liquid crystal display device when a negative optical anisotropic element is arranged.

[Explanation of symbols]

1 ... 1st electrode, 2 ... 1st board | substrate, 3 ... 2nd electrode, 4
... second substrate, 5 ... light control element, 6 ... driving liquid crystal cell,
7, 8 ... Polarizing plate, 9 ... Driving liquid crystal display element, 10, 11
... Optical anisotropic element, 12 ... Light control element, 13 ... Antireflection layer, 14 ... Driving power supply

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hitoshi Hato 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa, Ltd. Inside Toshiba Corporation Yokohama office (72) Inventor Takashi Honda 2-10-1, Tsukahara, Takatsuki-shi, Osaka Sumitomo Chemical Co., Ltd. (72) Inventor Akiko Shimizu 2-10-1 Tsukahara, Takatsuki City, Osaka Sumitomo Chemical Co., Ltd.

Claims (4)

[Claims] 1. A first substrate having a first electrode formed thereon,
A second substrate on which a second electrode is formed and which is opposed to the first substrate with a gap; and the first substrate and the second substrate
A liquid crystal cell having a twisted nematic type liquid crystal layer whose periphery is sealed and enclosed / sandwiched in a gap between the substrate and
At least one polarizing plate is disposed above and below the liquid crystal cell, and the transmitted light is connected to a driving circuit and a liquid crystal applied voltage is applied to the liquid crystal cell to change the attitude of the liquid crystal molecules. A liquid crystal display device for driving, which is driven by controlling the optical activity of the liquid crystal display device, and has an optical axis perpendicular to the surface of the substrate of the liquid crystal display device for driving, and has a negative optical difference opposite to the liquid crystal layer. Of the optically anisotropic element which is provided above and below or both above and below the driving liquid crystal display element, and the polarizing plate on the display surface side of the two polarizing plates of the driving liquid crystal display element. Placed above or below or both above and below,
While the scattering transmission intensity of light in a specific direction shows a distribution larger than the scattering transmission intensity of light in the other directions, the light scattering transmittance anisotropy that allows the light in the directions other than the specific direction to go straight through and be transmitted And a light control element having: a liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the optical anisotropic element has a twist axis in which the optical axis is an array continuously twisted in the thickness direction of the liquid crystal layer. And the twist axis of the optical anisotropic element is set to be perpendicular to the substrate surface of the driving liquid crystal display element, the refractive index anisotropy of the optical anisotropic element is Δn, and the optical axis of the optical axis is A liquid crystal display device, wherein a value of Δn × p is smaller than a wavelength in a visible light wavelength region, where p is a twist pitch length. 3. The liquid crystal display device according to claim 1, wherein the optically anisotropic element is a liquid crystal display element having the optical characteristics. . 4. The liquid crystal display device according to claim 1, wherein the optically anisotropic element is a polymer dispersion type liquid crystal display element having the optical characteristics. Liquid crystal display device.