KR100241816B1 - Liquid crystal display device and optical isotropic device - Google Patents

Abstract

The present invention relates to an optically compensated liquid crystal display device and an optically compensated optically anisotropic element, which improves visual dependence, in particular contrast ratio and visual dependence of display color, comprising at least one polarizing plate (1), (4) and two A liquid crystal display device having a driving liquid crystal cell in which a liquid crystal 3e is sandwiched between the substrates 3a and 3b, each having an optically anisotropic element 2 formed by arranging optically anisotropic units in a thickness direction. The optical anisotropy of the optically anisotropic unit is a sign with respect to the thickness direction.

The angle between the optical axis of the optically anisotropic element 2 and the substrate surface of the driving liquid crystal cell is continuously or stepwise changed in the direction of the layer thickness of the optically anisotropic element, and the optically anisotropic element having optical anisotropy is combined with the optically anisotropic element. It can be characterized by.

Description

Liquid Crystal Display and Optical Anisotropy

1 is a cross-sectional view showing a configuration of Embodiment 1 of the present invention.

2 (a) is an exploded perspective view showing the configuration of the first embodiment of the present invention.

2 (b) is a diagram for explaining Embodiment 1 of the present invention, illustrating a coordinate system for measuring electro-optical characteristics.

3 is a view for explaining the principle of operation of the TN type liquid crystal display device.

4 is a view for explaining the principle of generation of visual characteristics of a TN type liquid crystal display device.

5 is a view for explaining the principle of generation of visual characteristics of a TN type liquid crystal display device.

6 is a view showing the arrangement of the optically anisotropic element of the present invention.

7 is a view for explaining the principle of optical compensation when the optical anisotropic element of the present invention is used.

8 shows an ellipsoid of refractive index of a driving cell when voltage is applied.

9 is a diagram showing refractive index ellipsoids of an optically anisotropic element having refractive index anisotropy in the thickness direction.

10 is an electro-optical characteristic of the liquid crystal display device of Embodiment 1. FIG.

11 is an electro-optical characteristic of the liquid crystal display device of the prior art.

12 is a diagram illustrating a configuration of Embodiment 2. FIG.

FIG. 13 is a diagram illustrating an effect of Embodiment 2. FIG.

14 is a diagram for explaining the effect of the third embodiment.

FIG. 15 is a diagram illustrating a configuration of Embodiment 4. FIG.

FIG. 16 is a diagram explaining an effect of Embodiment 4. FIG.

FIG. 17 is a diagram illustrating a configuration of Embodiment 5. FIG.

FIG. 18 is a diagram illustrating a configuration of Embodiment 5. FIG.

19 is a diagram illustrating a configuration of a sixth embodiment.

20 is a view for explaining the operation of the sixth embodiment.

21 is a diagram illustrating a configuration of a seventh embodiment.

FIG. 22 is a diagram illustrating a configuration of Embodiment 9. FIG.

FIG. 23 is a diagram illustrating an effect of Embodiment 9. FIG.

24 is a view showing the arrangement of the positive optically anisotropic element according to the present invention.

25 is a view for explaining the principle of optical compensation in the case of using a positive optical anisotropic element according to the present invention.

26 is a configuration diagram of a liquid crystal display device of Embodiment 9;

27 is a curve diagram showing the electro-optical characteristics of the liquid crystal display device of Embodiment 9. FIG.

Fig. 28 is a curve diagram showing the electro-optical characteristics of the liquid crystal display device of the prior art.

29 is a curve diagram showing the electro-optical characteristics of Comparative Example 2.

30 is a curve diagram showing the electro-optical characteristics of Comparative Example 3.

FIG. 31 is a sectional view of a liquid crystal display element of Embodiment 11. FIG.

32 is a configuration diagram of a liquid crystal display device of Embodiment 11;

33 is a schematic diagram of the liquid crystal display element of Embodiment 11. FIG.

34 is a curve diagram showing the electro-optical characteristics of the liquid crystal display device of Embodiment 11. FIG.

35 is a curve diagram showing visual dependence of luminance of a conventional TN type liquid crystal display device.

* Explanation of symbols for main parts of the drawings

1, 4: polarizing plate 2: optically anisotropic element

2c: optically anisotropic material layer 3: driving liquid crystal cell

The present invention relates to an optically compensated liquid crystal display device and an optical anisotropy device for optical compensation.

The liquid crystal display device has a great advantage of thin, light weight and low power consumption, so it is used not only for displays such as wristwatches, electronic calculators, Japanese word processors, personal computers, but also for newly conceived products that actively utilize the advantages of liquid crystal display devices. have. Among them, liquid crystal display devices used in personal computers and the like have large-area display and large-capacity display, and the size of the display surface has been 10-inch diagonal and 640 × 480 pixels. Two types of display methods are used for liquid crystal display devices of this class. One is the simple matrix method, and the other is the active matrix method.

The simple matrix method has a simple structure in which a liquid crystal is sandwiched by two glass substrates having a comb-shaped transparent electrode. Therefore, in the simple matrix system, high performance is required for the liquid crystal. Before explaining the performance required for this liquid crystal, the display principle of the liquid crystal display element will be described. In the display of the liquid crystal display element, the display is performed by changing the direction of the liquid crystal molecules even when the voltage related to the liquid crystal is changed. In general, a large voltage difference is required to obtain a large contrast ratio. However, in order to express the display of 640 x 840 pixels, the voltage difference between dark and dark is small as about 1V, and a large state change of liquid crystal molecules is required only by the 1V difference. To realize this, it has been reviewed by many researchers for a long time and by a research group by Sefer et al. In 1985. Their research shows that by increasing the torsion angle (twist angle) of the array of liquid crystal molecules, the liquid crystal molecules have a certain degree of inclination in order to change the arrangement sensitively to voltage and to obtain a stable arrangement with a large torsion angle. I found it necessary. Since this research report, an orientation technique for realizing this has been actively carried out and has been successfully commercialized.

In order to express an array of 640x480 pixel displays, the twist angle is generally required to be 180 degrees or more, and the liquid crystal is called a super twisted nematic (STN) because of the large twist angle. Early STN displays, however, had a yellow background with a green smear on the display and no black display. This is because the twist angle is large, and as a means of eliminating the coloring of such a display, white display can be realized by disposing the second liquid crystal cell in which the arrangement of the liquid crystal layers is twisted in the reverse direction between the polarizing plate and the liquid crystal cell. Reported in the publication.

The principle of this black and whiteization eliminated the linear light dispersion by transmitting the liquid crystal molecules through the first liquid crystal cell in which the liquid crystal molecules were torsionally arranged, and transmitting the light having the linear light dispersion to the first liquid crystal cell and the second liquid crystal cell of the target structure. As a result, the coloring resulting from the linear light dispersion of the light can be eliminated and the black and white display can be realized. In order to accurately perform such a conversion, the second liquid crystal cell, which is an optical compensation plate, has substantially the same retardation value as the first liquid crystal cell, and the torsion directions are opposite to each other, and the arrangement directions of liquid crystal molecules adjacent to each other are orthogonal to each other. It is necessary to configure it.

As another means, various methods of using an optically anisotropic film instead of the above-mentioned second liquid crystal cell have also been proposed. This is a method in which the optically anisotropic film is laminated on the liquid crystal cell several times to have substantially the same function as the second liquid crystal cell.

The optical compensation described above enables black and white display in STN displays, and color display with higher added value can be realized by combining with a color filter. However, since the simple multiplex method is based on the time-averaging method based on the voltage averaging method, when the number of scanning players is increased to increase the display capacity, the voltage difference when blocking light and the voltage difference when transmitting light are remarkable. There is an inherent problem of decreasing, and as a result, the contrast ratio becomes small or the response speed of the liquid crystal becomes slow. In addition, such a prior art can realize a liquid crystal display device having a higher display quality because a phenomenon in which the display screen is inverted, the display screen is not visible at all, or the display is colored bleeding is observed due to the orientation or angle when the liquid crystal display device is viewed. This is a big problem.

On the other hand, since the active matrix system includes switching elements made of thin film transistors and diodes for each display pixel, an arbitrary voltage ratio can be set for each pixel liquid crystal layer regardless of the scanning source. Therefore, no special performance is required for the liquid crystal, such as in the case of the simple matrix method. The twist angle does not need to be as large as STN, but is 90 °.

Since the liquid crystal cell TN having a twist angle of 90 ° has a small torsion angle, there is no beneficiation dispersion and achromatic color high transistor display can be obtained. The response to voltage is also faster than that of STN. By combining the active matrix method and TN, a liquid crystal display device having a high contrast ratio and a fast response time can be realized as a representative capacity. In addition, since there is a switching element for each pixel, an intermediate voltage can be applied, and an intermediate tone display is also possible. In addition, in combination with a color filter, full color display can be easily realized.

However, even in the case of the active matrix method, it is fine when two values are displayed, but when the halftone is displayed, the display screen is inverted depending on the viewing direction, the display screen is not visible at all, or the display is color bleeding. This becomes a problem when realizing a liquid crystal display device having a higher display quality.

As a means of reducing the visual dependence of such a display, Japanese Laid-Open Patent Publication No. 87-21423 discloses disposing a birefringent layer, which is a negative polymer film in the thickness direction, between a liquid crystal cell and optical anisotropy between two polarizing plates. have. On the other hand, in Japanese Patent Application Laid-Open No. 91-67219, a birefringent layer composed of a liquid crystal compound (or a polymer liquid crystal) exhibiting a cholesteric liquid crystal phase having a product of spiral pitch length and refractive index of 400 nm or less is disposed on a liquid crystal cell. Is disclosed. These two proposals only consider liquid crystal cells that are vertically aligned (with liquid crystal molecules aligned vertically on the alignment substrate), but not in the case of liquid crystal cells that are twisted, such as TN or STN. . In addition, Japanese Patent Application No. 91-121578 (Japanese Patent Laid-Open No. 4-349429) proposes an optical compensation device having a tilt angle in an array of twist angles of 360 ° or more, but controls the viewing angle of the liquid crystal display device. In the case of displaying, the effect of enlarging the viewing angle is not yet sufficient. In addition, there have been technical reports for arranging the optical axis of negative optically anisotropic materials at an angle and improving the viewing angle characteristics of the TN-LCD (p. 298 to 301, p. 298 to 301).

The basic display principle of the above-mentioned liquid crystal display element is to change the direction of liquid crystal molecules by the voltage applied to liquid crystal, and to generate an optical change in a liquid crystal cell.

Therefore, when the liquid crystal display device is viewed obliquely, the direction of the liquid crystal molecules appears to be changed. In particular, when a small halftone is displayed, the inclination state of the liquid crystal molecules is changed more precisely.

The visual dependence of the viewing method of the liquid crystal molecule array is observed as a phenomenon in which the display screen is inverted or indistinguishable at all. Especially, when full color display is performed in combination with a color filter, the reproducibility of the display screen is remarkably decreased. It is a big problem.

SUMMARY OF THE INVENTION The present invention solves the above unreasonability and obtains a liquid crystal display device having improved contrast ratio and visual dependence of display color, and an optically anisotropic element used therein.

The present invention resides in a liquid crystal display device having the features shown below.

The present invention comprises a driving liquid crystal cell sandwiching a liquid crystal between at least one polarizing plate and two substrates and at least one optically anisotropic element in which a plurality of optically anisotropic units are connected in a thickness direction, and the optically anisotropic element is the optically anisotropic element. The optical anisotropy of the unit is a sign with respect to the thickness direction, and the angle of each optical axis is arranged so that the angle of each optical axis is not constant in the thickness direction and has minimum opticality in the thickness direction. to be.

It is preferable that the angle formed between the optical axis of the optically anisotropic element and the substrate surface of the driving liquid crystal cell is continuously or stepwise changed in the layer thickness direction of the optically anisotropic element.

It is preferable that the angle of the optical axis of the optically anisotropic element is changed in the layer of the optically anisotropic element so as to be substantially parallel to the substrate surface on the side close to the driving liquid crystal cell and almost on the side of the substrate on the side away from the substrate.

The angle of the optical axis of the optically anisotropic element is preferably changed in the layer of the optically anisotropic element such that the angle near the driving liquid crystal cell almost follows the normal of the substrate and is substantially parallel to the surface of the substrate on the side away from the substrate.

As viewed from the normal direction of the substrate of the driving liquid crystal cell, it is preferable that the direction of the optical axis of the optically anisotropic element is inclined in the layer direction and on a single axis.

When the direction of the optical axis of the optically anisotropic element is distorted when viewed from the normal direction of the substrate of the driving liquid crystal cell, it is effective, but it is preferable that the opticality is low.

An optically anisotropic element in which the angle of the optical axis of the optically anisotropic element is substantially parallel to the substrate surface on the side close to the driving liquid crystal cell and on the side away from the substrate almost in accordance with the normal line of the substrate; The second optically anisotropic element is varied in the layer of the optically anisotropic element such that the angle of the optical axis of the optically anisotropic element is almost parallel to the substrate surface on the side near the driving liquid crystal cell and on the side away from the substrate. At least one liquid crystal display device can be obtained.

The optical axis of the optically anisotropic element is changed in the thickness direction in the layer of the optically anisotropic element such that on one surface side of the optically anisotropic element is substantially parallel to the normal direction of such surface and 10 ° to 80 ° on the side away from the surface. It is preferable. The optical axis of the optically anisotropic element is a first angle selected such that the angle formed with one surface of the optically anisotropic element is 10 ° to 90 ° on one surface side, and is smaller than the first angle and 0 ° to on the other surface side away from the surface. It is preferable to change in the layer of the optically anisotropic element to achieve the second angle in the range of 80 °.

Further, the optical axis on the side substantially parallel to the substrate surface of the driving liquid crystal cell of the optically anisotropic element is arranged at parallel and close angles or perpendicular to the absorption axis of the polarizing plate when viewed in the normal direction of the substrate. It is desirable to have.

A substrate of the optical axis of the optically anisotropic element comprising at least one polarizing plate, a liquid crystal cell for driving a liquid crystal between two substrates, and at least one optically anisotropic element comprising at least one optically anisotropic unit The angle formed with the surface is substantially the same on the side close to the driving liquid crystal cell, but is changed in the middle portion, and the optical anisotropy of the optically anisotropic element is a sign with respect to the thickness direction. Can be obtained.

The angle between the optical axis of the optically anisotropic element and the substrate surface of the driving liquid crystal cell is substantially the same on the side near and far from the driving liquid crystal cell, but is continuously or stepwise changed in the layer thickness direction of the optically anisotropic element at the middle portion. It is preferable.

It is preferable that the direction of the optical axis of the optically anisotropic element is on a single axis when viewed from the normal direction of the substrate of the driving liquid crystal cell.

It is preferable that the direction of the optical axis of an optically anisotropic element is two or more directions when it sees from the normal line direction of the board | substrate of a drive liquid crystal cell.

It is preferable that the optical axis of the optically anisotropic element is twisted continuously or stepwise when viewed from the normal direction of the substrate of the driving liquid crystal cell.

It is preferable to arrange | position a biaxial retardation film between a polarizing plate and an optically anisotropic element.

It is preferable that the optically anisotropic unit of the optically anisotropic element is made of an organic or inorganic material or a polymer liquid crystal.

Moreover, this invention exists in the optically anisotropic element which has the characteristic shown below.

In an optically anisotropic element in which a plurality of optically anisotropic units are connected in the thickness direction, the angle formed between the optical axis and the surface of the optically anisotropic element is different in the vicinity of the upper and lower surfaces of the optically anisotropic element, and the optical anisotropy of the optically anisotropic element is in the thickness direction. Optical anisotropic element, characterized in that for the sign.

It is preferable that the angle of the optical axis of the optically anisotropic element is continuously or stepwise changed in the layer thickness direction of the optically anisotropic element with respect to the surface of the optically anisotropic element.

The angle of the optical axis of the optically anisotropic element is preferably changed in the layer of the optically anisotropic element such that the angle of the optical axis is substantially parallel to the surface of the optically anisotropic element and almost conforms to the normal of the surface on the other side of the optically anisotropic element.

The angle of the optical axis of the optically anisotropic element is preferably changed in the layer of the optically anisotropic element such that the angle of the optical axis almost conforms to the normal of the surface of the optically anisotropic element and is substantially parallel to the surface of the other side of the optically anisotropic element.

When viewed from the normal direction of the surface of the optically anisotropic element, it is preferable that the direction of the optical axis of the optically anisotropic element is on a single axis.

It is preferable that the direction of the optical axis of the optically anisotropic element is distorted when seen from the normal direction of the surface of the optically anisotropic element.

An optically anisotropic element, wherein the angle between the optical axis and the surface of the optically anisotropic element is substantially the same on one side and the other side, but is changed in the middle portion, and the optical anisotropy of the optically anisotropic element is a sign with respect to the thickness direction.

It is preferable that the angle between the optical axis of the optically anisotropic element and the surface is substantially the same on one side and the other side, but is continuously or stepwise changed in the layer thickness direction of the optically anisotropic element at the middle portion.

When viewed from the normal direction of the surface of the optically anisotropic element, it is preferable that the direction of the optical axis of the optically anisotropic element is on a single axis.

The optical axis of the optically anisotropic element is preferably two or more directions when viewed in the normal direction of the surface of the optically anisotropic element.

It is preferable that the optical axis of the optically anisotropic element is twisted continuously or stepwise when viewed from the normal direction of the surface of the optically anisotropic element.

It is preferable that the optically anisotropic material layer of the optically anisotropic element is made of an organic or inorganic material or a polymer liquid crystal.

The present invention also provides a driving liquid crystal cell in which a liquid crystal is sandwiched between two substrates between at least two polarizing plates and at least one optically anisotropic layer having different optical anisotropy symbols in an optically anisotropic unit. The liquid crystal display device having the optically anisotropic layer is characterized in that the opticality in the direction inclined from the normal direction of the combined optically anisotropic layer is greater than the linearity in the normal direction.

It is preferable that the optical axis of the optically anisotropic unit of the optically anisotropic layer whose optical anisotropy of the said optically anisotropic unit is positively inclined uniformly with respect to the optically anisotropic layer thickness direction, or it changes continuously in the optically anisotropic layer thickness direction.

It is preferable that the optical axis of the optically anisotropic unit of the optically anisotropic layer is uniformly inclined with respect to the optically anisotropic layer thickness direction or continuously changed in the optically anisotropic layer thickness direction and the orientations of the optical axes are arranged in the same direction.

It is preferable to arrange | position the combination of the optically anisotropic layer whose optical anisotropy of the said optically anisotropic unit is a code | symbol, and the optically anisotropic layer whose optical anisotropy of an optically anisotropic unit is positive number on both surfaces of a drive liquid crystal cell.

It is preferable to arrange | position the optically anisotropic layer which consists of the said optically anisotropic unit of negative optical anisotropy adjacent to the drive liquid crystal cell.

Characterized in that the inclination angle of the optical axis of the optically anisotropic layer in which the optical axis of the optically anisotropic unit of the optically anisotropic layer is continuously changed with respect to the optically anisotropic layer thickness direction is disposed adjacent to the driving liquid crystal cell. It is desirable to.

It is preferable that the optical axis orientation of the optically anisotropic layer whose optical anisotropy of the said optically anisotropic unit is positive and the optical axis orientation of the optically anisotropic layer whose optical anisotropy of the optically anisotropic unit is a sign are orthogonal to each other.

Further, in the liquid crystal display device, the optical axis of the optically anisotropic unit of the optically anisotropic layer whose optical anisotropy of the optically anisotropic unit is positively inclined uniformly with respect to the optically anisotropic layer thickness direction or continuously changed in the optically anisotropic layer thickness direction The optically anisotropic element is disposed.

An optically anisotropic element is an optical anisotropy of an optically anisotropic unit, the optical axis is an array in which the optical axis is continuously changed in the layer thickness direction in a plane consisting of an axis of a constant direction of the thickness axis and the layer cross section, and the optical axis at the layer cross section. It is preferable that the optical axis is inclined at 10 degrees to 60 degrees with respect to the layer cross section at a substantially vertical direction with respect to this cross section.

In the optically anisotropic element, it is preferable that the optical axis orientation of the optically anisotropic layer having the optical anisotropy of the optically anisotropic unit and the optical orientation of the optically anisotropic layer having the optical anisotropy of the optically anisotropic unit are orthogonal to each other.

In addition, it is preferable that the arrangement of the driving liquid crystal cells is continuously changed in the thickness direction.

SUMMARY OF THE INVENTION The present invention solves the above problems by simultaneously reducing the contrast dependence of the liquid crystal display device, the brightness at the time of gray scale display, the visual dependence of the display color, or the specific orientation and time of view in which the liquid crystal display device obtains a certain contrast ratio. To control. The effect is demonstrated below.

In liquid crystal display devices such as TN and STN, when the light is incident perpendicularly to the display surface of the liquid crystal display device and when it is inclined at an angle, the polarization state of the light propagating in the liquid crystal display device is different, and the difference in the polarization state is indicated. It is directly reflected on the reversal or coloring of cotton. This phenomenon is observed when the angle of view of the display surface of the liquid crystal display device is inclined greatly from the display surface normal, and voltage is particularly applied to the liquid crystal layer of a liquid crystal cell (hereinafter referred to as a driving cell) having a means for applying a voltage to the liquid crystal layer. Appears remarkably in the applied pixel.

FIG. 35 is a view showing the angle dependency of display luminance when tilted from 0 ° to 60 ° in the left and right directions in the display surface normal line of the conventional TN liquid crystal display device. The steps displayed in steps 1 through 8 are the respective gradation numbers of the gradation display, and the voltages applied to the liquid crystal cells are sequentially changed. In step 1, 0V and step 8, 5V are applied to the liquid crystal cell. For example, in the upward direction, the luminance is gradually increased as the angle (time) inclined from the normal of the display surface of the display is increased from 0 ° (front face) to 60 °. In actual display, it is observed that the display color becomes white (white circle). On the other hand, when viewing the downward direction, when the time is tilted from the front (0 °) to 60 °, the brightness decreases inversely to the upper direction. This phenomenon is observed to be dark (black circle) in the display color on the actual display screen. In addition, the brightest display stage 1 on the front side and the gradation level 2 lower than that are reversed in magnitude at 35 ° in the upper direction and inverted display (negative) such as the negative of the photographic film on the actual display screen. Is observed. It is ideal that the transmittance does not change even when the time is changed in any of the gradation steps. However, as shown in FIG. 35, the visual characteristics of the actual TN are relatively good in the left and right azimuth, but bad in the up and down azimuth.

This phenomenon occurs because, as described above, the visual characteristic of the liquid crystal display device is due to the different polarization state depending on the incident angle of light incident on the liquid crystal display device, but this will be described in detail with reference to TN.

3 shows the operation principle of the TN type liquid crystal display device. FIG. 3 (a) shows the arrangement state of the liquid crystal molecules LM in the TN cell when no voltage is applied to the electrodes 3c and 3d. When no voltage V is applied, the liquid crystal molecules are parallel to the substrate in the thickness direction of the liquid crystal layer (in the direction of the Z axis in the drawing), and the liquid crystal molecules are continuously twisted. When the light Li polarized by the polarizer Pi enters into this arrangement, the polarization plane rotates according to the torsional arrangement of the liquid crystal molecules LM, and where the polarization plane exits the liquid crystal layer, the polarization plane is polarized before entering the liquid crystal layer. It rotates by the twist angle of a liquid crystal layer with respect to a surface. When the transmission axis Pot of the analyzer Po is matched with this rotation direction, the transmitted light Lo is obtained.

FIG. 3 (b) shows the arrangement state of the liquid crystal molecules in the TN cell at the time of voltage application. By the application of the voltage V, the liquid crystal molecules LM rise, and the liquid crystal molecules LMc near the center of the cell are inclined more than the liquid crystal molecules LMs near the electrodes. The inclination of the liquid crystal molecules LMs near the electrodes 3c and 3d is small because there is an orientation control force (necessary for orienting the liquid crystal) of the electrode-liquid crystal layer interface. According to the magnitude of the voltage V, the inclination of the liquid crystal molecules increases, and at the same time, the torsional arrangement is deformed, and when the voltage becomes larger, the torsion is finally released. When the polarization Li is incident in such a state, the polarization plane Lp does not rotate, and thus the polarization plane Lp does not rotate, and where the polarization plane exits the liquid crystal layer, the polarization plane does not change as before incident on the liquid crystal layer. Therefore, since the transmission axis Pot of the analyzer Po is orthogonal to the polarization plane Lp, polarization cannot transmit. In addition, in order to display the halftone, the magnitude of the voltage applied to the liquid crystal layer is set smaller than this, leaving a slight twisting arrangement of the alignment, and slightly rotating the polarization plane exiting the liquid crystal layer to obtain intermediate transmitted light.

By the above principle, transmitted light is controlled using the distortion of a torsional arrangement. Next, the phenomenon with respect to the light of an oblique direction is demonstrated.

4 is a diagram for explaining a state in which light is incident on oblique portions in a molecular arrangement state when displaying halftones. FIG. 4 (a) is a perspective view showing the relationship between the molecular arrangement state LMint and the directions L and U of two incident light beams when displaying halftones. FIG. 4 (b) is also shown in FIG. 4 (c). Here, Z-axis is shown by the normal line direction of the board | substrate of a drive liquid crystal cell, and the board | substrate surface is shown by the XY axis. The liquid crystal molecules LMs near the electrodes 3c and 3d of the upper and lower substrates are arranged slightly obliquely. This inclination is called a pretilt angle, and generally shows the inclination of the liquid crystal molecule in a pretiltlan substrate-liquid crystal interface, and the inclination angle is called the pretilt angle (alpha) 0. When no voltage is applied, the substrate is inclined at the same angle between the upper and lower substrates 3a and 3b. If there is a predetermined slope (pretilt) over the region where the voltage V is applied, the inclination direction when the voltage is applied is aligned in the direction of the pretilt, and as a result, a uniform display can be performed. If there is no pretilt, the tilting direction of the liquid crystal molecules becomes different when voltage is applied, and defect lines are generated at boundaries between regions having different inclination directions, which causes a reduction in display quality. Therefore, in order to obtain a uniform display, pretilt is indispensable, and the angle is generally 1 ° to 6 ° in the TN mode.

Therefore, as shown in Fig. 4 (b) and Fig. 4 (c), when the intermediate tones are displayed, the arrangement state of the liquid crystal molecules becomes asymmetric with respect to the Y axis. As shown in LM-L of FIG. 5 with respect to the polarized light of L that enters the inclination in the direction of + Z axis from + X axis of FIG. 4 (b), the arrangement is in a state where there is no inclination in liquid crystal molecules LM (just like voltage unmanned) Visible state), the polarization plane can be greatly rotated. As a result, the transmitted light becomes larger than the intensity of the emitted light with respect to the incident light (light parallel to the Z axis) from the front side. On the other hand, with respect to the polarized light U incident in the opposite direction to this in Fig. 4 (c) (obliquely in the direction of the -Z axis to the + Z axis), as shown in LM-U of Fig. 5, the arrangement is a liquid crystal molecule ( LM) becomes largely inclined (as in a state in which a larger voltage is applied) and the polarization plane cannot be rotated. As a result, the transmitted light becomes smaller than the intensity of the emitted light with respect to the incident light (light parallel to the Z axis) from the front surface. The symmetrical relationship with FIG. 35 corresponds to the orientation of L in FIG. 4 in the upward direction of FIG. 35 and the U direction in FIG. 4 corresponds to the downward direction of FIG.

As described above, the orientation dependence of transmitted light in the halftones is due to the asymmetry of the arrangement of liquid crystal molecules. The asymmetry of this arrangement varies the rotational (optical) angle of the polarization plane depending on the direction in which light is incident, resulting in a change in transmittance. In the TN type liquid crystal display device, it can be said that the photoensitivity occurs in the upper direction, and the photoensitivity tends to decrease in the lower direction. Therefore, in order to improve this, the optical dependence of the liquid crystal display device can be improved by adding an optical anisotropy device in which optical lightness is decreased in the upper direction and optical lightness occurs in the lower direction.

Firstly, the characteristics required for the optically anisotropic element are summarized. The characteristics required for the optically anisotropic element are based on the linearity between the upper and lower directions for the liquid crystal cell for driving in which the visual characteristics of either the upper or lower direction are not good. The abduction direction is reversed.

Secondly, it is required to be a characteristic that improves visual characteristics with respect to different orientations.

The present invention provides an optically anisotropic element having such characteristics and a liquid crystal display device having the optically anisotropic element.

The structure of the optically anisotropic element which concerns on this invention is demonstrated.

The optically anisotropic element in this invention is a film | membrane, plate, sheet-like flat body which has optical anisotropy, and has thickness. In the element with the optical anisotropy, as shown in Fig. 9, the refractive index of the Z axis or the optical axis perpendicular to the XY axis direction constituting the plane is small.

A thin layer having optical anisotropy in which the optical axis faces a certain direction is defined as an optically anisotropic unit, and the optically anisotropic element is referred to as a configuration in which the unit is stacked in multiple layers. It also includes unbounded boundaries of each layer.

Therefore, the representative configuration of the present invention comprises at least one polarizing plate, a driving liquid crystal cell in which a liquid crystal is sandwiched between two substrates, and at least one optically anisotropic element in which a plurality of optically anisotropic units are continuous in a thickness direction. The element is arranged so that the optical anisotropy of the optically anisotropic unit is a sign with respect to the thickness direction, and the angle of each optical axis is not constant with respect to the thickness direction, and has minimum opticality in the thickness direction. The liquid crystal display device is characterized by the above-mentioned.

For example, in one embodiment, the optical structure of a hybrid structure in which the optical axis is substantially parallel to one side on one side and almost inverted on the other side by gradually changing the inclination over the other side on one side of the device. Anisotropic elements can be mentioned.

In order to improve the visual dependence, the present invention is directed to an optically anisotropic device assembly in which at least one optically anisotropic layer having different optical anisotropy codes of optically anisotropic units is combined. These anisotropic elements are characterized in that the opticality in the tilting direction is greater than that in the normal direction of the combined optically anisotropic layer, for example, a pair of positive and negative optical anisotropies. It is used as a combination. This is arrange | positioned at the both sides of the drive liquid crystal cell, for example.

First, when the characteristics required for the optically anisotropic element are summarized, the characteristic required for the optically anisotropic element is that the rotation direction of the beneficiation is reversed between the upper and lower directions.

6 is a view showing the arrangement of the optical axis of the optically anisotropic element of the present invention, Figure 6 (a) is a cross-sectional view of the optically anisotropic element of the present invention, shown as an ellipse is an optically anisotropic unit constituting the optically anisotropic element ( LD), and the short axis normal of the ellipse corresponds to the optical axis OL. The unit may be one molecule or may be composed of a plurality of molecules arranged in a stack or the like.

The inclination of the long axis is continuously changed from the lower substrate 2d to the upper substrate 2a, and in the vicinity of the lower substrate 2d, it is almost perpendicular to the substrate surface and almost parallel to the vicinity of the upper substrate 2a. (Hybrid orientation). An example of this arrangement from above is shown in Figure 6 (b). Arrows in the figure indicate the direction of the optical axis. 6 (c) is an arrangement diagram when observed obliquely from the Z axis. The inclination direction is shown by the XYZ axis in the figure. The figure seen from the oblique direction opposite to this is shown to FIG. 6 (d). As seen in FIG. 6 (c) and FIG. 6 (d), when the arrangement of FIG. 6 (a) is observed obliquely from the Z axis, in FIG. 6 (c), the traveling direction proceeds from the bottom to the top. It is twisted to the left as seen in Fig. 6 (d), and is arranged to be twisted to the right which is this inverse. The optical anisotropic elements arranged obliquely in this manner can realize the above-described "opposite rotation direction between the upper and lower directions".

In addition, the optically anisotropic element as the optically anisotropic element of the present invention can be seen as a structure in which the optically anisotropic material layer unit is laminated in multiple layers in the thickness direction thereof. Each layer unit has an optical axis, and the inclination of this optical axis changes continuously or stepwise. Moreover, the optical axis arrangement which has the minimum linearity in the thickness direction is taken.

Next, how the optical anisotropic element is combined with the driving cell will be described to obtain a good compensation effect.

7 (a) is a diagram in which the driving cells shown in FIGS. 3, 4, and 5 are indicated by arrows in the same manner as in FIG. 6, with the symbol Lip representing the polarization axis of incident light and the symbol Lop indicating the polarization axis of the emitted light. FIG. 7 (a) shows the optical anisotropic element and FIG. 7 (b) shows the driving cell TN to which the voltage corresponding to the halftone is applied from the Z axis. 7 (c) is a diagram showing the arrangement of molecules of each optically anisotropic material layer constituting the optically anisotropic element when it reaches the + X axis side on the Z axis, and shows the beneficiation state when linearly polarized light is incident in the figure. Indicated. In this direction, the optically anisotropic element has the property of rotating the polarization plane of the incident light in the left direction (left ray ability). FIG. 7 (d) shows an arrangement state of the drive cells when viewed from the same direction as that of FIG. 7 (c). The liquid crystal molecules are gradually inclined because a voltage corresponding to the intermediate tone (a voltage slightly higher than the threshold voltage (limit voltage at which the liquid crystal operates)) is applied, and from this direction, the length and the short axis direction of the liquid crystal molecules are viewed. Orientation portions occur in which the lengths are almost equal. Therefore, the incident polarization is transmitted without being linearly polarized, and the direction of the polarization axis Lo of the emitted light is almost unchanged from the polarization axis Lip of the incident light. This is the cause of display abnormality called "black circle" in which the display becomes dark. In this case, if the polarized light is increased (increased the optical power) in the left turn, this is improved. The optically anisotropic element of FIG. 7 (c) is suitable for this. The optically anisotropic element of Fig. 7 (c) has left line light capability and compensates for the insufficient line light as a drive cell.

In addition, this and reverse direction are demonstrated using FIG. 7 (e) and FIG. 7 (f). 7 (e) and 7 (f) show the arrangement of the optical axes when the optically anisotropic element of FIG. 7 (a) is observed from the -X axis in the direction of the Z axis, and turns to the right with respect to the incident light in the figure. It has the characteristic (priority optical power) to make. Fig. 7 (f) is the same as that of Fig. 7 (d), in which the voltage of the midtones is applied, and in this direction, the liquid crystal molecules are not inclined even though they are inclined. Comes out. This causes a display abnormality called a "white circle" in which the display becomes brighter than necessary, and applying a priority light that suppresses the beneficiation of the left turn can eliminate the extra beneficiation, thereby improving the "white circle". The optically anisotropic element of FIG. 7 (e) has a first optical capability, and by combining this with a driving cell, the characteristics of the element can be improved.

The optical anisotropy in which the optical anisotropy in which the optical anisotropy in the tilting direction with respect to the normal of the optically anisotropic element surface is larger than the optical anisotropy in the direction of the normal is described as an example of the enlargement of the field of view, but is twisted in the hybrid orientation. In the optically anisotropic element evenly tilted between the upper and lower plates, similar characteristics to those of the hybrid anisotropic element are obtained, which can be selected according to the design specifications of the liquid crystal display element. In addition, although TN has been described as an example, the same principle can be applied to STN, so it can be used as a means of improving the vision of STN.

The optical anisotropy showing negative optical anisotropy is characterized by the optical arrangement in the oblique direction of the device having a characteristic larger than the front direction (Z axis) by the hybrid arrangement as described above, thereby mainly displaying abnormality of "black circle" or "white circle." There is a big improvement in terms of. In the above description, the optical anisotropy of the optically anisotropic unit constituting the optically anisotropic element is shown as a sign. However, when the optically anisotropy in the oblique direction shows a characteristic larger than the front direction, Not to mention the same effect.

In addition, in the above description, the hybrid array is shown, but the optical axis of the optically anisotropic unit constituting the optically anisotropic element when viewed from the device normal line direction is not only such an arrangement but also exhibits a characteristic in which the beneficiation in the oblique direction is larger than the front direction. Even if the arrangement is twisted in the direction of the element surface, the arrangement of the optical axis with the same inclination of the optical axis at both ends of the optical anisotropic element, and the arrangement of the internal arrangement being continuously or stepwise changed, for example, the band arrangement or the spray arrangement of two hybrid arrays. The same effect is obtained.

The retardation value of the optically anisotropic element is preferably smaller than the retardation value of the liquid crystal cell for driving, and more preferably near the retardation value of the liquid crystal cell for driving when a voltage indicating an intermediate tone is applied. Do. However, this value is not necessarily limited to this, depending on product specifications or mass productivity. Further, the arrangement and arrangement of the optical anisotropic elements vary depending on the product specifications, mass productivity, price, etc., depending on the optical anisotropic elements used in combination, the number of copies thereof, and the like.

In addition, when an optical characteristic is combined with a product specification, an optical anisotropic element having a biaxial optical axis, or an optical anisotropic element having various optical anisotropies having an optical anisotropy of an optical anisotropic unit, or an optical anisotropy It goes without saying that the same effect can be obtained even when the optical anisotropy having the optical anisotropy of a material is used in combination with an optically anisotropic element having various arrangements.

Examples of the material showing negative optical anisotropy include C ₁₈ H ₆ (OCOC ₇ H ₁₅ ) ₆ having an alkyl chain attached to the triphenylene nucleus as an ester bond, C ₆ (OCOC _m H _{2m + 1} ) ₆ having a benzene nucleus, and the like. This is called a discotic liquid crystal. It can also be used as a crystal phase so that a desired arrangement can be formed in the temperature range showing the liquid crystal phase so that the arrangement does not change. In addition, the temperature range representing the liquid crystal phase is defined as the operating temperature range of the liquid crystal module, and when the optically anisotropic element is made so that the arrangement can be controlled by an electric field or the like, it is also possible to voltage control the visual characteristics.

In the present invention, the optically anisotropic material constituting the optically anisotropic element exhibits a better visual improvement effect with a sign having different inclination of the optical axis of the optical anisotropy. Next, the principle that the viewing angle characteristic is improved when using a liquid crystal having optical anisotropy is described.

When the state where the threshold voltage or more is applied to the driving liquid crystal cell is represented by a three-dimensional refractive index ellipsoid, it is as shown in FIG. The Z axis corresponds to the substrate surface of the liquid crystal cell in the XY plane in the thickness direction of the liquid crystal cell. In the birefringence phenomenon, the normal point on the center point of the index ellipsoid RA connecting the observation point when the center point of the index ellipsoid RA is seen from a certain direction and the center point of the index ellipsoid RA cuts the index ellipsoid RA. It is represented by the shape of the oval-shaped cut surface formed when doing this (referred to here as a refractive index body in a two-dimensional surface). If the difference between the major axis and the minor axis of the refractive index in this two-dimensional plane corresponds to the phase difference between ordinary light and abnormal light, and the transmission axes of the polarizing plates sandwiching the liquid crystal cells are perpendicular to each other, the phase difference is zero (0). The transmitted light of the cell is blocked, and when the phase difference is not zero, the transmitted light according 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 (when directly viewed from the front of the liquid crystal cell), the refractive index RA4 of the two-dimensional surface becomes a circle, and the phase difference between the normal light and the ideal light becomes zero (0). When the light is incident on the liquid crystal cell substrate surface in the tilting direction RA1, the refractive index ellipsoid RA5 becomes an ellipse, and a phase difference between the normal light and the abnormal light occurs. The polarization state is different.

When the angle of view of the refractive index ellipsoid RA of FIG. 8, that is, the time RA3 is increased, the refractive index RA5 in the two-dimensional plane of the time axis RA1 becomes larger in the longitudinal direction of nRA1, and in the direction of the time axis RA1. Larger transmitted light is observed than seen. Ideally, it is preferable that the shape of the refractive index in the two-dimensional plane does not change when the viewing angle is changed in any orientation.

Such optical compensation can be realized by arranging the disk-shaped index ellipsoid RB as shown in FIG. 9 on the Z axis of the index ellipsoid RA in FIG. 8 (that is, adjacent to the top or bottom of the liquid crystal cell). Can be. In such a configuration, when the time RA3 is increased, the refractive index RA in the two-dimensional plane of the refractive index ellipsoid RA increases in the longitudinal direction of nRA1, and the length of the nRA2 in the refractive index ellipsoid RB increases. The refractive index becomes large, and as a result, the synthesized refractive index in the two-dimensional surface becomes a circle, and the refractive index ellipsoid (RA) can be optically compensated, and the visual characteristic is improved.

In the actual liquid crystal display device, as shown in FIG. 8, the refractive index ellipsoid of the driving liquid crystal cell is slightly inclined rather than perpendicular to the display surface. Therefore, it is preferable that the disk-shaped short axis of the refractive index ellipsoid RB of the optically anisotropic element of FIG. 9 compensates for this.

In fact, the refractive index ellipsoid as shown in FIG. 9 can be realized by forming an optically anisotropic element composed of an optically anisotropic material layer in which the optical axes are continuously twisted, or a material having a smaller refractive index in the in-plane direction than in the thickness direction.

Hereinafter, a method of realizing an optical anisotropic element having an optical anisotropy sign as an optical anisotropic element composed of an optically anisotropic material layer in which the optical axes are continuously twisted is described.

In general, the driving liquid crystal cell actively displays the polarization direction of light in the visible wavelength region (generally from 380 nm to 750 nm) by the voltage applied to the liquid crystal cell.

On the other hand, in the optically compensated optically anisotropic element of the present invention, the optical axis of the optically anisotropic material layer is twisted continuously, so opticality may occur under optical conditions of the optically anisotropic element. Here, opticality refers to a property in which the oscillation direction of the light rotates to the left or right along the traveling direction as the light travels in the medium. When the optical axis of the optically anisotropic element is continuously twisted when the optical axis is constant, when the torsion pitch of the optical axis is long, the light rotates the polarization plane according to the torsion of the optical axis, but when the torsion pitch of the optical axis is short, the light is the optical axis It is impossible to follow the torsion, and the beneficiation does not occur. If the optical anisotropy of the optically anisotropic element is large, the polarization plane of the light passing through the device is changed, and as a result, the contrast ratio is reduced or, in some cases, the polarization plane is changed in various ways depending on the wavelength of the light. Problems such as light coloring occur.

Therefore, it is necessary to make at least the optical anisotropy of the optical anisotropic element to the visible light of the optically anisotropic element to be smaller than the optical light to the visible light of the driving liquid crystal cell. Beneficiation is highly dependent on the wavelength of the light passing through the medium and the medium through which the light passes. The magnitude of the beneficiation is represented by the degree of change in the retardation value of the medium with respect to the change in the optical axis.

Therefore, the linearity of the light of the driving liquid crystal cell is Δn1 (= ne-no: refractive anisotropy) between the refractive index of the liquid crystal of the driving liquid crystal cell and the refractive index ne of the abnormal light. If the thickness is d1 and the angle (twist angle) of the twist arrangement of the liquid crystal layer is T1,

Δn1d1 / T1 = R1 / T1 [1.1]

However, R1 = Δn1, d1 (retardation value)

It can be represented as

Similarly, the optical anisotropy of the compensation optical anisotropy element is represented by the refractive index anisotropy of the optically anisotropic material layer of the compensation optically anisotropic element Δn2, the thickness of the laminated optically anisotropic material layer d2, and the total twist angle of the optical axis of the optically anisotropic material layer. Is T2,

Δn2d2 / T2 = R2 / T2 [1.2]

However, R2 = Δn2, d2

It can be represented as.

Therefore, the relation between the linearity of the compensating optical anisotropic element and the linearity of the driving liquid crystal cell is expressed in [1.1] and [1.2].

(R1 / T1)〉 (R2 / T2) [1.3]

Becomes

The propagation of light in the optically anisotropic element in which the optical axis of the optically anisotropic material layer is continuously twisted is represented by a parameter represented by the following equation (C.Z. Van Physics Letters 42A, 7 (1973)).

f = λ / (p × Δn) [1.4]

Is the wavelength of visible light (visible wavelength range)

p is the torsion pitch length of the optical axis (p = d / T)

In the case of f << 1, the light in the optically anisotropic element changes in polarization plane according to the twist angle of the optical axis, and has opticality. As described above, it is preferable that the optical anisotropy element is small in opticality, and the optical anisotropic element must satisfy the condition f >> 1. Therefore, optical anisotropy in [1.4]

p × Δn <λ [1.5]

It is necessary to satisfy.

By the way, a liquid crystal having a very large twist angle, that is, a short spiral pitch, is generally referred to as a cholesteric liquid crystal, but the product of the helical pitch of the liquid crystal (p) and the average refractive index (n) of the cholesteric liquid crystal If the value of n × p is in the visible wavelength range (depending on the conditions, the short wavelength end is in the range of 360 nm to 400 nm and the long wavelength end is in the range of 760 nm to 830 nm), it causes selective scattering.

(J.L. Fergason; Molecular Crystals 1.293 (1966)). Such a phenomenon is not only seen in the correster liquid crystal cell, but may also occur in an optically anisotropic element in which the optical axis of the optically anisotropic body is continuously twisted. When selective scattering occurs, coloration of the optically anisotropic element occurs and the display color changes. Therefore, coloring phenomenon can be prevented by making the product nxp of the average refractive index n of the optically anisotropic material layer which forms an optically anisotropic element and the twisted pitch p of an optical axis out of the visible wavelength range.

In addition, the optically anisotropic element can be realized by a thin film in which a liquid crystal cell and a polymer liquid crystal are arranged in a twisted manner with a laminate of a retardation film which produces optical anisotropy by stretching a polymer film.

In this case, since it is obtained by apply | coating this polymer layer to at least one of the board | substrates of a drive liquid crystal cell, it becomes easy in manufacture, for example, and a more preferable liquid crystal display element is obtained. For example, the polymer copolymer etc. which have a polysiloxane as a principal chain and have biphenyl benzoate and a cholesteryl group in a suitable ratio in a side chain can be used.

The same effect can be obtained even if the optically anisotropic element is produced not only between the polarizing plate and the substrate but also in the cell inside the substrate. For example, you may apply a polymer liquid crystal to the inside of a board | substrate, and may produce an oriented film on it.

However, if one or more of the same type is used to realize that the characteristic required for the optical anisotropic element is the opposite direction of rotation of the beneficiation between the upper and lower directions, the thickness becomes thick and the retardation value becomes too large. There is a drawback that the color changes. The reason for this is that the light passing through the optically anisotropic element has a birefringence effect with linear light, and the linearly polarized light becomes elliptical polarization, and the ellipticity is different depending on the wavelength of the light.

Therefore, in order to eliminate the desired linear light performance and color blur, it was found that a hybrid arrangement of optically anisotropic elements made of optically anisotropic units of code having different optical anisotropy, such as the combination of the elements of the code and the code, obtains both required performances.

Next, the positive optical anisotropic element to be combined with the optical anisotropic element of the sign will be described.

As described in the optically anisotropic element of the sign, the case where the characteristic of the opposite direction of rotation of beneficiation between the upper direction and the lower direction is obtained is demonstrated.

24 is a view showing the arrangement of the optical axis of the optical anisotropic element of the present invention, Figure 24 (a) is a cross-sectional view of the optical anisotropic element of the embodiment of the present invention, shown in ellipses constitute an optical anisotropic element The optically anisotropic body (LD) is shown and the ellipsoidal axis corresponds to the optical axis (OL). The inclination of the long axis is continuously changed from the electrode of the lower substrate 2b to the electrode of the upper substrate 2a, and is substantially parallel to the substrate surface near the lower substrate electrode and almost perpendicular to the upper substrate electrode. (Hybrid orientation). An example of this arrangement from above is shown in Figure 24 (b). Arrows in the ellipse in the figure indicate the direction of the optical axis.

The direction of each optical axis in the layer is on the same plane, ie arranged side by side on a single axis. 24 (c) is an arrangement diagram when it observes obliquely from the Z axis. The inclination direction is shown by the XYZ axis in the figure. The figure seen from the inclination direction of this and reverse is shown in FIG. 24 (d). As seen in FIG. 24 (c) and FIG. 24 (d), when the arrangement of FIG. 24 (a) is observed obliquely from the Z axis, in FIG. 24 (c), the traveling direction proceeds from the bottom to the top. Are twisted to the left as seen in Fig. 24 (d), and are arranged twisted to the right opposite to this. The optically anisotropic elements arranged in such a manner as described above can realize the property described above that "the rotation direction of the beneficiation between the upper and lower rocks is reversed".

Next, how the optically anisotropic element is combined with the driving liquid crystal cell to obtain a correct compensation effect will be described next.

FIG. 25 (a) shows the driving liquid crystal cell shown in FIGS. 3, 4, and 5 as an arrow in the same manner as in FIG. 24, where the symbol Lip is the polarization axis of the incident light and the symbol Lop is the polarization axis of the emitted light. Indicates. FIG. 25A shows the optically anisotropic element and FIG. 25B shows the driving liquid crystal cell TN to which the voltage corresponding to the halftone is applied from the Z axis. FIG. 24 (c) is a diagram showing the arrangement of the optical axes of the optically anisotropic elements as seen from the + X side on the Z axis, and shows the beneficiation state when linearly polarized light is incident in the figure. In this direction, the optically anisotropic element has the property of rotating the polarization plane of the incident light to the left direction (left-hand light ability). FIG. 25 (d) shows an arrangement state of the driving liquid crystal cell when viewed in the same direction as that of FIG. 25 (c). The liquid crystal molecules are inclined obliquely because a voltage corresponding to the halftone (a voltage slightly larger than the threshold voltage (limit voltage) at which the liquid crystal operates) is inclined obliquely. An orientation portion is formed in which the lengths of are substantially the same. Therefore, incident polarization does not fluoresce so much, and the direction of the polarization axis Lo of the emitted light hardly changes with the polarization axis Lip of the incident light. This is the cause of the display abnormality called "black circle" in which the display becomes dark. In this case, if the polarized light is beneficiated (increased the optical power) in the left turn, this is improved. The optically anisotropic element shown in Fig. 25 (c) is suitable for this. The optically anisotropic element of Fig. 25 (c) has left line light capability, and compensates for the insufficient line light in the driving liquid crystal cell.

In addition, this and reverse direction are demonstrated using FIG. 25 (e) and FIG. 25 (f). 25 (e) and 25 (f) show the arrangement of the optical axes when the optically anisotropic element of FIG. 25 (a) is observed in the -X axis in the Z-axis direction, and is rotated to the right with respect to the incident light in the figure. Has characteristics (priority photonic power). Fig. 25 (f) is a state in which the intermediate color tone is applied as in Fig. 25 (d), and it appears that the liquid crystal molecules are not inclined even though the liquid crystal molecules are inclined from this direction. This causes a display abnormality called "white circle" where the display becomes brighter than necessary, and application of priority light that suppresses the beneficiation of the left rotation can eliminate the excess beneficiation, thereby improving the "white circle". The optically anisotropic element of Fig. 25 (e) has a first optical capability, and the improvement of characteristics is obtained by combining this with the driving liquid crystal cell.

The optical anisotropy in which the optical anisotropy of the hybrid orientation in which the beneficiation in the direction inclined to the normal of the optical anisotropic element surface is inclined to the normal in the direction of the normal has been described as an example, but the viewing angle is enlarged. Even if the optically anisotropic element is tilted uniformly between the element and the upper and lower substrates, similar characteristics to the optically anisotropic element of the hybrid orientation are obtained, which can be selected according to the design means of the liquid crystal display element. In addition, although TN has been described as an example, the same principle can be applied to STN and Hybrid Aligned Nematics, so that it can be used as a means of improving STN's perspective.

As described above, the optical anisotropy unit showing negative optical anisotropy has a characteristic in which the linearity in the oblique direction of the device has a characteristic larger than that in the front direction by the hybrid arrangement as described above, and is mainly related to display abnormality of "black circle" and "white circle." Although there is a significant improvement effect, the optical anisotropy of the optically anisotropic material exhibits the same effect as the optically anisotropic material exhibiting greater characteristics in the oblique direction in the oblique direction.

The present invention can improve the visual dependence of the driving liquid crystal cell over the entire orientation by combining at least one of the optically anisotropic layer or the element having the optical anisotropy of the reference number and the sign.

In addition, in the above description, each optical anisotropic element is shown in a case where the optical anisotropy unit is a hybrid array, but the optically anisotropic unit in the oblique direction exhibits a characteristic larger than the front direction when viewed from the element normal direction as well as such an arrangement. Even if the optical axis of the optically anisotropic material layer constituting the optically anisotropic element is arranged in the direction of the element plane, the direction of the optical axis in both cross sections of the optically anisotropic element is the same, and the same effect can be obtained even if the internal arrangement is changed continuously and stepwise.

In order to realize the above-described optically anisotropic element, for example, an ultraviolet curable liquid crystal in which a polymerizable functional group such as acryloyloxy group is imparted to the liquid crystal may be used.

EMBODIMENT OF THE INVENTION Embodiment of the liquid crystal display element of this invention is described in detail.

Embodiment 1

1 and 2 show cross-sectional views of the liquid crystal display element in this embodiment. The liquid crystal display device 10 includes two polarizing plates 1 and 4 (LLC2-92-18 manufactured by SANRITZ), a liquid crystal cell 2 as an optical anisotropy element for visual compensation, and a driving liquid crystal cell 3 therebetween. Has the configuration fitted. The polarizing plate 1 sandwiches the polarizing film 1a inside the transparent substrate 1b, and the polarizing plate 4 is also formed by attaching the polarizing film 4a to the transparent substrate 4b.

The optical compensation liquid crystal cell 2 as an optical anisotropic element is disposed between the polarizing plates 1 and 4 and has a cell structure in which an optically anisotropic material layer 2c is interposed between the transparent substrates 2a and 2b. The substrates 2a and 2b each deposited SiO ₂ on the surface at different angles, and the optically anisotropic dendritic discotic liquid crystals (C ₁₈ H ₆ with alkyl group chains attached to the triphenylene nucleus by ester bonds) ( OCOC ₇ H ₁₅ ) ₆ is introduced as an optically anisotropic material layer, and the pretilt angle is set to 30 ° near the driving liquid crystal cell 3 and 60 ° far away. Δnd of the optically anisotropic material layer used for the film was 570 nm.

The driving liquid crystal cell 3 is disposed between the visual compensation liquid crystal cell 2 and the polarizing plate 4. The two upper substrates 3a and the lower substrates 3b form transparent electrodes 3c and 3d, respectively, and are connected to the driving power source 3E. A twisted nematic liquid crystal (ZLI-4287, manufactured by E. Merck Co. Ltd.) having a positive dielectric anisotropy between the substrates 3a and 3b was mixed with a chemical agent S811 (trade name, manufactured by E. Merck Co. Ltd.). The twist angle is introduced at 90 degrees, but the state changes in accordance with the applied voltage from the drive power source 3f. In the absence of voltage, the twisted arrangement is maintained.

(DELTA) n of the liquid crystal used for the drive liquid crystal cell 3 is 0.093 micrometer, and the thickness of a liquid crystal layer is 5.5 micrometer. The liquid crystal molecules of the driving liquid crystal cell 3 are twisted counterclockwise from the lower substrate 3b to the upper substrate 3a (left twisted). The cell 3 operates as a TN cell having a 90 ° twist angle and is optically controlled by the beneficiation.

FIG. 2 (a) is an exploded perspective view showing the configuration of the liquid crystal display element in this embodiment.

(1, 1) and (4, 1) are the transmission axes of the two polarizing plates 1 and the polarizing plates 4, and they are orthogonal to each other so that (1, 1) is + Z, which is the normal direction of the substrate with respect to the Y axis. It is arranged at 135 ° counterclockwise. (3, 1), (3, 2) are the rubbing axes of the upper and lower substrates 3a and 3b of the liquid crystal cell 3 for driving, that is, they are orthogonal to each other in the alignment processing direction, and with respect to the Y axis. The angles which become the rubbing shafts 3 and 1 are arranged at 45 degrees counterclockwise as seen from the + Z direction.

(2, 1) and (2, 2) of the optical compensation liquid crystal cell 2, which are optically anisotropic elements, are the rubbing axes of the upper and lower substrates 2a and 2b, respectively. The rubbing shafts 2 and 2 are arranged in parallel with the rubbing shafts 3 and 1 of the driving liquid crystal cell 3. That is, the optical axis OL (FIG. 6) of the liquid crystal molecule LM is disposed along this rubbing axis, and becomes the optical axis of the liquid crystal layer on the side of the liquid crystal layer in contact with the rubbed surface of the substrate.

The polarizing plates 1 were arranged so that the transmission axes 1, 1 were perpendicular to the rubbing axes 2, 1 of the liquid crystal cell 2 for visual compensation.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value (voltage applied between the driving voltage 3f and the electrodes 3c-3d of the driving liquid crystal cell 3) at the time of measurement was changed from 1V to 5V. The results are shown in FIG. FIG. 10 shows the applied voltage-transmittance characteristics of the four directions of up, down, left, and right, respectively, and shows the transmittance when the time is changed every 30 degrees from the front to 60 degrees. Ideally, any angle is the same as the transmittance curve of the front face (time θ = 0 °). In the frontal direction, when a certain voltage is exceeded, the transmittance decreases with increasing voltage.

11 shows the applied voltage-transmittance characteristic diagram of the TN-LCD of Comparative Example 1 of the prior art, but the transmittance decreases with increasing time. This corresponds to the occurrence of a "black circle" when gradation display is actually performed. In addition, re-increasing the transmittance around 3V at the time 60 ° corresponds to "inversion" in the actual display. In the upward direction, as the time increases from 0 ° to 60 ° at a voltage of 3V, the transmittance increases. This corresponds to the white circle in the actual display. In the case of this embodiment, looking at FIG. 10, the characteristic of a downward direction hardly changes, a right direction and an upper direction deteriorate, and "inversion" decreases to 60 degrees only with respect to a left direction, and improvement is seen.

Such a characteristic can be used when the user wants to improve the view of only a specific direction such as a car navigation device or a personal information terminal.

Comparative Example 1

In Embodiment 1, the voltage-transmittance characteristic in the case where there is no liquid crystal cell 2 for visual compensation was measured. The measurement results are shown in FIG. In this comparative example, the display became white in the upper direction depending on the angle, and in the lower direction, the display became black or the gray level was reversed.

Embodiment 2

12 is an exploded perspective view showing the configuration of a liquid crystal display element in this embodiment. In Embodiment 1, the optical compensation liquid crystal cell 2, which is an optically anisotropic element, is coated with polyamide AL-1051 (manufactured by Japan Synthetic Rubber) on the surface of the lower substrate 2b in contact with the liquid crystal. It is carried out. The pretilt angle is 1 °. On the other hand, the vertical alignment treatment is performed on the side of the upper substrate 2a in contact with the liquid crystal. (DELTA) nd of the liquid crystal cell for visual compensation produced in this way is -570 nm. The optical axis of the liquid crystal molecules, i.e., the optical axis of the optically anisotropic element, is parallel to the cell on the driving liquid crystal cell side and continuously changes in the layer thickness direction so as to almost follow the normal direction of the cell substrate on the side away from the liquid crystal cell 3. The twist angle is 0 degrees.

(1, 1) and (4, 1) are the transmission axes of the polarizing plate 1 and the polarizing plate 4, these are orthogonal to each other, and (1, 1) are counterclockwise in the + Z direction with respect to the Y axis. Placed at 135 °. (3, 1) and (3, 2) are the rubbing axes of the upper and lower substrates 3a and 3b of the driving liquid crystal cell 3, which are orthogonal to each other, and the rubbing axes 3 and 1 with respect to the Y axis. ) And the angle of rotation is 45 ° counterclockwise.

The optical axes 2 and 2 of the visual compensation liquid crystal cell 2 are orthogonal to the rubbing axes 3 and 1 of the upper substrate of the liquid crystal cell 3 for driving and the rubbing axes of the lower substrate 2b. It is arrange | positioned so that it may become parallel to the rubbing axes 3 and 1 (hybrid arrangement).

The transmission axes 1, 1 of the polarizing plate 1 are arranged to be parallel to the rubbing axes 3, 1 of the upper substrate of the driving liquid crystal cell 3.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value (voltage applied between the drive voltage 3f and the electrodes 3c-3d of the driving liquid crystal cell 3) at the time of measurement was changed from 1V to 5V. The results are shown in FIG. As can be seen from FIG. 11 which is the characteristic diagram of the conventional example, although the visual direction of an upper direction and a right direction deteriorates, the "reversal" of the lower direction disappears substantially, and the contrast of the time of 60 degrees of the left direction is improved.

Embodiment 3

In Embodiment 2, the liquid crystal layer of the visual compensation liquid crystal cell 2 was made to be the torsional arrangement of a twist angle of 10 degrees. The twist direction is twisted counterclockwise from the lower substrate 2b to the upper substrate 2a (left twist). The conditions other than that are substantially the same as that of Embodiment 2. The voltage-transmittance characteristic is shown in FIG. Since the twist angle is 10 DEG, there is no significant difference from the second embodiment, but the distortion is added to the liquid crystal cell 2 for visual compensation, thereby increasing the inversion of the left and right directions, thereby improving the contrast in the lower direction.

Embodiment 4

FIG. 15 is an exploded perspective view showing the configuration of the liquid crystal display element in this embodiment. The visual compensation liquid crystal cell 2 which is a 1st optically anisotropic element is the same as that of the visual compensation liquid crystal cell 2 in Embodiment 2. As shown in FIG.

The visual compensation liquid crystal cell 5, which is the second optically anisotropic element, has the structure of the visual compensation liquid crystal cell 2 reversed up and down. Polyimide AL-1051 (manufactured by Japan Synthetic Rubber) is applied to the surface of the lower substrate 2b of the liquid crystal cell 2 for visual compensation and the surface of the upper substrate 5a of the liquid crystal cell 5 for visual compensation. The surface is rubbed. The pretilt angle is 1 °. On the other hand, the vertical alignment process is performed on the side of the upper substrate 2a of the visual compensation liquid crystal cell 2 and the side of the lower substrate 5b of the visual compensation liquid crystal cell 5 in contact with the liquid crystal. Δnd of the visual compensation cell is -570 nm in both cells. The optical axis of the liquid crystal molecules, i.e., the optical axis of the optically anisotropic element, is parallel to the surface of the cell substrate on the side close to the driving liquid crystal cell of the visual compensation liquid crystal cell 2, and continuously changes in the layer thickness direction from the liquid crystal cell 4 On the distant side, it almost follows the normal direction of the substrate, and the cell 5 is the reverse.

The twist angle is 0 ° in both cells.

(1, 1) and (4, 1) are the transmissive axes of the polarizing plate 1 and the polarizing plate 4, and they are orthogonal to each other and (1, 1) are viewed in the + Z direction with respect to the Y axis in the counterclockwise direction. Placed at 135 °. (3, 1) and (3, 2) are the rubbing axes of the upper and lower substrates 3a and 3b of the driving liquid crystal cell 3, which are orthogonal to each other, and the rubbing axes 3 and 1 with respect to the Y axis. The angle formed by) is placed 45 ° counterclockwise in the + Z direction.

The optical axes 2, 2 of the visual compensation liquid crystal cell 2 are orthogonal to the rubbing axes 3, 1 of the upper substrate of the driving liquid crystal cell 3 by the rubbing axis of the lower substrate 2b, and the lower substrate. It is arrange | positioned so that it may become parallel with the rubbing shafts 3 and 2 of this.

The optical axes 5 and 1 of the visual compensation liquid crystal cell 5 are parallel to the rubbing axes 3 and 1 of the upper substrate of the driving liquid crystal cell 3 by the rubbing axis of the upper substrate 5a. It is arranged to be orthogonal to the rubbing shafts 3 and 2.

The transmission axes 1 and 1 of the polarizing plate 1 were arranged so as to be parallel to the rubbing axes 3 and 1 of the upper substrate of the driving liquid crystal cell 3.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value at the time of measurement (voltage applied by the driving liquid crystal cell 3 between the electrodes 3c-3d from the driving power supply 3E) was changed from 1V to 5V. The results are shown in FIG. Compared with FIG. 11, which is the characteristic diagram of the conventional example, the characteristics of the left direction and the lower direction were worse, but the "reverse" of the right direction was lost, and the "white circle" of the upper direction was also improved.

Embodiment 5

17 is an exploded perspective view showing the configuration of the liquid crystal display element in this embodiment. The visual compensation liquid crystal cell 2 which is the first optically anisotropic element has a structure similar to that of the visual compensation liquid crystal cell 2 in the second embodiment. However, the one-side substrate is a pre-tilt angle of the four-way deposit the SiO _2, and the lower substrate is 60 °. Vertical alignment processing is performed on the side of the upper substrate 2a in contact with the liquid crystal.

The visual compensation liquid crystal cell 5, which is the second optically anisotropic element, has the structure of the visual compensation liquid crystal cell 2 reversed up and down. Δnd of the visual compensation cell is -180 nm in both cells. The twist angle is 0 ° in both cells.

(1, 1) and (4, 1) are the transmission axes of the polarizing plate 1 and the polarizing plate 4, these are orthogonal to each other, and (1, 1) is the counterclockwise direction in the + Z direction with respect to the Y axis. To 135 °. (3, 1) and (3, 2) are the rubbing axes of the upper and lower substrates 3a, 3b of the driving liquid crystal cell 3, these are orthogonal to each other, and the rubbing axes 3, 1 with respect to the Y axis. The angle formed by) is placed 45 ° counterclockwise in the + Z direction.

The optical axes 2, 2 of the visual compensation liquid crystal cell 2 are orthogonal to the rubbing axes 3, 1 of the upper substrate of the driving liquid crystal cell 3 in the alignment direction of the lower substrate 2b, It is arrange | positioned so that it may become parallel to the rubbing shafts 3 and 2. As shown in FIG.

The optical axes 5 and 1 of the visual compensation liquid crystal cell 5 are parallel to the rubbing axes 3 and 1 of the upper substrate of the driving liquid crystal cell 3 in the alignment direction of the upper substrate 5a, and It is arranged to be orthogonal to the rubbing shafts 3 and 2.

The transmission axes 1 and 1 of the polarizing plate 1 were arranged so as to be parallel to the rubbing axes 3 and 1 of the upper substrate of the driving liquid crystal cell 3.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value (voltage applied between the driving power supply 3E and the electrodes 3c and 3e of the driving liquid crystal cell 3) at the time of measurement was changed from 1V to 5V. The results are shown in FIG. Compared with FIG. 11, which is a characteristic diagram of the conventional example (Comparative Example 1), the "reverse" in the lower direction was worse, but the "reverse" in the left and right directions disappeared, and the "white circle" in the upper direction was also greatly improved.

Embodiment 6

19 is an exploded perspective view showing the configuration of a liquid crystal display element in this embodiment. The visual compensation liquid crystal cell 20 which is the optically anisotropic element in this embodiment is comprised from two optically anisotropic layers, and in Embodiment 4, the visual compensation cells 2 and 5 overlapped. (DELTA) nd was -380 nm.

20 is a cross-sectional view of the visual compensation liquid crystal cell 2 viewed in the + X axis direction. In the direction of the rubbing axis (2, 1) in the cell (2) of FIG. 19, the optical axis direction when the + Z axis direction is viewed with the boundary of the substrate 2d subjected to the vertical alignment treatment on both surfaces is between 2a and 2d. The lower 2d · 2b is different from the (2, 2) direction. When the rubbing axes 2, 1 and (2, 2) are in the same direction, the optical axis becomes a single axis, and when it is in the other direction, the rubbing axes 2, 1 and (2, 2) become biaxial as shown in this embodiment. The optical axis is continuously changed by twisting the liquid crystal layer.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value (voltage applied between the driving power supply 3E and the electrodes 3c-3d of the driving liquid crystal cell 3) at the time of the measurement was changed from 1V to 5V. Compared with FIG. 11 showing the characteristics of the conventional example, the "inversion" and "black circle" in the downward direction are improved, and there is no change in other orientations.

As shown in Example 4, the optically anisotropic element used in this embodiment is obtained by combining several optically anisotropic elements of the present invention. In addition, it is possible to manufacture an optically anisotropic element composed of one optically anisotropic layer by band-aligning and band-twisting the liquid crystal having the optical anisotropy code.

Embodiment 7

The structure of this embodiment is shown in FIG. Biaxial retardation film 50 for the purpose of supplementing the optical anisotropy of the unstable discotic array between the visual compensation liquid crystal cell 2 and the driving liquid crystal cell 3 in which the first optical is the discharge element in Embodiment 2 Placed. In particular, no significant improvement was seen, but the display spots due to misalignment can be alleviated.

Embodiment 8

In Embodiment 2, the visual compensation liquid crystal cell 2 was made of a polymer copolymer having polysiloxane as the main chain and biphenyl benzoate and cholesteryl group in the side chain at a suitable ratio. Obtained. In addition, a thinner display device can be realized by manufacturing an optically anisotropic device with a polymer copolymer.

Embodiment 9

FIG. 22 is a sectional view of the liquid crystal display element in the present embodiment, and a diagram for explaining the operation in FIG. 23. FIG. The liquid crystal display element is composed of two polarizing plates (LLC2-92-18: manufactured by SANRITZ) (1, 4), a liquid crystal cell (2, 5, 6, 7), which is an optical anisotropic element for visual compensation, and a liquid crystal cell for driving. (3) has a configuration fitted.

The visual compensation liquid crystal cell used as the optically anisotropic elements 2 and 5 is disposed between the polarizing plate 1 and the driving liquid crystal cell 3. The optically anisotropic element 2 has an optical anisotropy. It has a liquid crystal cell structure in which a liquid crystal 2c is interposed between the transparent substrates 2a and 2b. The substrates 2a and 2b have different alignment treatments, and the reference numeral “2a” is vertically oriented and “2b” is horizontally oriented. As the horizontal alignment treatment of “2b”, rubbing is performed on the alignment film. Tilt orientation of ° is obtained. As the liquid crystal 2c, a nematic liquid crystal (ZLI-4287, manufactured by E. Merck Co., Ltd.) having optical anisotropy is used, and has a thickness of 1.9 µm and is a product of retardation (the optical anisotropy of the liquid crystal and the thickness of the liquid crystal layer). ) Is 180 nm. The optically anisotropic element 7 (substrate 7a, 7b) is the element of the optical anisotropy similar to the optically anisotropic element 2, and it is arrange | positioned upside down.

The optically anisotropic element 5 is composed of a visual compensation cell which is a sign of optical anisotropy, and has a liquid crystal cell structure in which a liquid crystal 5c is interposed between the transparent substrates 5a and 5b.

On the transparent substrate 3b, SiO ₂ was deposited on the surface at an angle, and optically anisotropy was discotic liquid crystal (C ₁₈ H ₆ (OCOC ₇ H ₁₅ ) ₆ having an alkyl bond attached to the triphenylene nucleus by an ester bond is optical. It is introduced as an anisotropic substance, and the pretilt angle is set at 60 ° to the side near the driving liquid crystal cell 4 and at 90 ° to the far side, and the retardation is -220 nm. The optically anisotropic element 6 (substrate 6a). 6b)) is made of the visual compensating cell of the same optical anisotropy as the optical anisotropic element 5, and is arranged upside down.

The optically anisotropic elements 2 and 5 and the optically anisotropic elements 6 and 7 correspond to each other, and the element having the optical anisotropy code is arranged to face the driving liquid crystal cell 3. That is, the driving liquid crystal cell 3 is arranged between the optically anisotropic element 5 of the sign and the optically anisotropic element 6 of the sign.

The upper substrate 3a of the driving liquid crystal cell 3 includes a liquid crystal between a substrate 3a on which a transparent electrode 3a1 is formed on a color filter and a substrate 3b on which a thin film transistor and a pixel electrode 3b1 are formed on each pixel. 3c) is inserted to form a 90 ° twisted orientation when no voltage is applied. The liquid crystal 3c is a mixture of nematic liquid crystals (ZLI-4287, manufactured by E. Merck Co. Ltd.) and S811 (trade name, manufactured by E. Merck Co. Ltd.) at a twist angle of 90 °. The state changes in accordance with the applied voltage from the drive power source 4E, which is an applying means. In the absence of voltage, the torsional arrangement is maintained.

(DELTA) n of the liquid crystal used for the drive liquid crystal cell 3 is 0.093, and the thickness of a liquid crystal layer is 5.0 micrometers. The liquid crystal molecules of the driving liquid crystal cell 3 are twisted counterclockwise from the lower substrate 3b to the upper substrate 3a (left twist). This cell 3 operates as a TN cell with a 90 ° twist angle and is optically controlled by beneficiation.

FIG. 26 is an exploded explanatory view showing the structure of the liquid crystal display element in this embodiment, and FIG. 26 (a) is a perspective view, FIG. 26 (b) is a top view, and FIG. 26 (c) is a side view. (1, 1) and (4.1) are absorption axes of two polarizing plates 1 and 7, which are orthogonal to each other and (1, 1) is + Z, which is the normal direction of the substrate with respect to the X axis. It is arranged at 45 ° counterclockwise.

(3, 1), (3, 2) are the rubbing axes of the upper and lower substrates 3a and 3b of the liquid crystal cell for driving, that is, they are orthogonal to each other in the alignment treatment direction, 3 and 1) are arranged at 135 ° counterclockwise in the + Z direction.

Definition The optically anisotropic element 2 has the optical axis of the optically anisotropic unit 20U arranged side by side in the same orientation, and as shown in the side view of FIG. The substrate is arranged at an inclined angle of about 90 ° between them (hybrid arrangement).

The average of the optical axes of these optically anisotropic units, that is, the average optical axis 20A, is disposed at 225 ° in the counterclockwise direction as seen from the + Z direction with respect to the X axis.

The positive optically anisotropic element 7 disposed on the other surface side of the liquid crystal cell 3 also has the same configuration as the optically anisotropic element 2, and its arrangement is such that the optically anisotropic element 2 is turned upside down when viewed from the + Z axis. In addition, the average optical axis 60A is set at 135 degrees with respect to the X axis on the + Z axis. On the other hand, in the negative optically anisotropic element 5, the optical axis 50U of the optically anisotropic unit (the direction in which the refractive index is the smallest is defined as the optical axis) is 90 ° in the upper plate as shown in FIG. The inclination angle is continuously changed between 60 degrees. Therefore, the average optical axis 50A is inclined with respect to the element surface, and the direction thereof is disposed at -45 ° on the X axis as seen from the + Z axis.

The negative optically anisotropic element 5 also has the same configuration as the optically anisotropic element 3, and the optical anisotropic element 2 is turned upside down when viewed from the + Z axis, and the average optical axis 60A is the average optical axis 20A. It is arranged to be 45 ° to the X axis in the + Z axis.

The electro-optical characteristic was measured for the liquid crystal display element of this structure by changing the angle of a viewpoint, azimuth angle (o), and time (theta) in the coordinate system of FIG. 2 (b). The voltage value (voltage applied to the liquid crystal layer 4c of the driving liquid crystal cell 3 at the driving voltage 3E) at the time of measurement was changed from 0V to 5V, and the transmittance of the liquid crystal panel was measured. The results are shown in FIG. FIG. 27 shows the applied voltage-transmittance characteristics of the four directions of up, down, left, and right (excluding the decrease in the transmittance by the color filter), and shows the transmittance when the time is changed by 30 ° from the front to 60 °. The ideal characteristic is the same as the transmittance curve of the front face (time θ = 0 °) at any angle.

28 is an applied voltage-transmittance characteristic diagram when the optically anisotropic element of the prior art is not used. The downward direction characteristic is that the transmittance decreases as time increases. This corresponds to the occurrence of a "black circle" when the gradation display is actually performed. In addition, re-increasing the transmittance near 3V at time 60 ° corresponds to "inversion" in the actual display. As for the upward direction, the transmittance increases as the time increases from 0 ° to 60 ° at a voltage of 3V. This corresponds to "white circle" in the actual display.

In the case of the present embodiment, in Fig. 27, the improvement in the characteristics of all the orientations is shown, and in particular, the transmittance at the inclination of 60 ° at 0 V is high except for the upward direction, and bright display can be realized even in an oblique direction.

When the actual present liquid crystal display device was observed with 64 gray scales, even when the angle was increased, good display was obtained.

Comparative Example 2

In the ninth embodiment, the voltage-transmittance characteristic when the positive optically anisotropic element 3 and the optically anisotropic element 5 were not included in the positive optically anisotropic element 2 and the optically anisotropic element 6 was measured. The measurement results are shown in FIG. In the present comparative example, the downward orientation is somewhat improved, but the transmittance at 5V at the left and right is high and the contrast ratio is low.

Comparative Example 3

With respect to Embodiment 9 of FIG. 22, the voltage-transmittance characteristic of the negative optical anisotropic element 5 and the optical anisotropic element 6 was measured only with the positive optical anisotropic element 2 and the optical anisotropic element 7. The measurement results are shown in FIG. In this comparative example, the transmittances of the upper direction, the left direction, and the right direction are suppressed low even at 5 V, but the sudden decrease in the transmittance at the lower direction is remarkable, and inversion and black circles occur.

Embodiment 10

In Embodiment 9, the biaxial phase difference film was disposed between the visual compensation liquid crystal cell 2 and the driving liquid crystal cell 3 as the first optical anisotropic element to compensate for the optical anisotropy of the unstable discotic array. . Although there was no significant improvement in characteristics, it was possible to alleviate display stains due to misalignment.

Embodiment 11

31 and 32 show a liquid crystal display device according to the present embodiment. The liquid crystal display device 10 is composed of two polarizing plates 1 and a polarizing plate 4 (LLC-92-18 manufactured by SANRITZ Co., Ltd.) and an optically anisotropic element for visual compensation between them and a driving liquid crystal. It has the structure which inserted the cell 3. The polarizing plate 1 is formed by attaching a polarizing film to a transparent substrate, and the polarizing plate 4 is similarly formed by attaching a polarizing film to a transparent substrate.

As the optical anisotropic element, the visual compensation liquid crystal cell 2 is disposed between the polarizing plate 1 and the polarizing plate 4, and the transparent substrates 2a and 2b are interposed between the optically anisotropic material layer 2c. Has Discrete SiO ₂ on the surface of the substrate 2a and the substrate 2b at different angles at an angle, and discotic liquid crystals having optical anisotropy therebetween (C ₁₈ H ₆ (OCOC attached to the alkyl chain by ester bond to triphenylene nucleus) ₇ H ₁₅ ) ₆ ) is introduced as an optically anisotropic material layer, and the pretilt angle (incline of the optical axis 20U with respect to the substrate surface) is about 30 ° to the side close to the driving liquid crystal cell 3 and about to the far side. 90 degrees (refer to FIG. 33). The effective Δnd of the optically anisotropic material layer used for the vision compensation liquid crystal cell 2 is -60 nm.

The driving liquid crystal cell 3 is disposed between the visual compensation liquid crystal cell 2 and the polarizing plate 4.

The two upper substrates 3a and the lower substrates 3b form transparent electrodes 3a ₁ and 3b ₁ , respectively, and are connected to the driving power source 3E. A nematic liquid crystal (ZLI-4287, manufactured by E. Merck Co. Ltd.) having positive dielectric anisotropy is charged between the substrates 3a and 3b and changes its state in accordance with the applied voltage from the driving power source 3E. If no voltage is applied, the hybrid array is maintained.

(DELTA) nd of the liquid crystal molecule of the driving liquid crystal cell 3 is 0.093, and the thickness of a liquid crystal layer is 5.0 micrometers. The liquid crystal molecules of the driving liquid crystal cell 3 are arranged from the lower substrate 3b to the upper substrate 3a with a tilt angle varying from almost vertical to horizontal (hybrid arrangement).

32 is an exploded perspective view showing the configuration of the liquid crystal display element in this embodiment.

(1, 1) and (4, 1) are the transmission axes of the two polarizing plates 1 and 4 and they are orthogonal to each other and (1, 1) is viewed in the + Z direction, which is the normal direction of the substrate with respect to the Y axis. It is placed at 45 ° counterclockwise rotation. (3, 1) is the rubbing axis of the upper substrate 3a of the driving liquid crystal cell 3, that is, the angle formed with the rubbing axes 3, 1 with respect to the Y axis in the alignment processing direction is counterclockwise in the + Z direction. It is disposed at 180 ° in the directional rotation. (3, 2) almost coincides with the -Z direction in the alignment direction of the lower substrate 3b.

(2, 1) and (2, 2) of the optical compensation liquid crystal cell 2, which are optically anisotropic elements, are arranged in the orientation processing direction of the upper substrate 2a and the lower substrate 2b, respectively. ) Is arranged such that its alignment treatment directions 2 and 2 are parallel to the rubbing axes 3 and 1 of the driving liquid crystal cell 3.

The polarizing plate 1 was arranged such that the transmission axes 1 and 1 made an angle of 45 ° with the rubbing axes 2 and 1 of the visual compensation liquid crystal cell 2.

The electro-optical characteristic of the liquid crystal display element of this structure was measured in the coordinate system of FIG. 2 (b). The voltage value at the time of measurement (the voltage applied between the electrodes 3a1 and 3b1 of the driving liquid crystal cell 3 at the driving voltage 3E) was changed from 0V to 5V. The results are shown in FIG. FIG. 34 shows time-luminance characteristics for each of the gradations of the top, bottom, left and right, respectively, and shows the gradation luminance when changing the time by 10 degrees from the front to 60 degrees. The ideal is the same as the transmittance curve of the front face (time θ = 0 °) at any angle.

In the case of the present embodiment, in FIG. 34, the "inversion" is reduced in any of the up, down, left, and right directions compared to TN, and the black transmittance hardly increases, so that the contrast ratio is wide and stable. Obtained.

According to the present invention, it is possible to provide a high-definition display liquid crystal display device having excellent contrast and visual characteristics of contrast and display color of the liquid crystal display device. The present invention can also be used under certain conditions, for example, when it is desired to change the perspective of only one direction, such as car navigation.

Furthermore, although the present invention deals only with TN type liquid crystal display elements using TFTs, it goes without saying that excellent effects can be obtained even when applied to simple matrix liquid crystal display elements such as active matrices using MIM and the like.

Claims (15)

A driving liquid crystal cell in which a liquid crystal is sandwiched between at least one polarizing plate and two substrates, and disposed between the polarizing plate and the driving liquid crystal cell, the first main surface of the driving liquid crystal cell side and the second main surface of the polarizing plate side. A liquid crystal display device having at least one optically anisotropic element having a plurality of optically anisotropic units connected from the first main surface to the second main surface, wherein the optically anisotropic unit has an optical anisotropy sign of the optically anisotropic unit. (Iii) and at the same time arranged so that an angle between the respective optical axis and the first main surface gradually increases from the first main surface side toward the second main surface side. The liquid crystal display device according to claim 1, wherein the angle is changed continuously or stepwise. The optical axis of the optically anisotropic unit near the first main plane of the optically anisotropic element is substantially parallel to the first main plane, and the optical axis of the optically anisotropic unit near the second main plane is a first one. A liquid crystal display device, characterized in that substantially follows the normal of the main surface. The liquid crystal display device according to claim 2, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is arranged on a single axis as viewed in the normal direction of the first main surface. The liquid crystal display device according to claim 2, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is twisted when viewed in the normal direction of the first main surface. The liquid crystal display device according to claim 1, wherein a biaxial retardation film is disposed between the polarizing plate and the driving liquid crystal cell. The liquid crystal display device according to claim 1, wherein the optically anisotropic unit of the optically anisotropic element is made of a polymer liquid crystal. The liquid crystal display of claim 1, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is in a range of 0 to 80 ° in the vicinity of the first main surface, the angle formed with the first main surface. . 10. The liquid crystal display device according to claim 8, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is about 0 ° in the vicinity of the first main surface, wherein the angle formed by the first main surface is 0 degrees. The liquid crystal display of claim 1, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is in a range of 10 to 90 degrees with respect to the first main surface in the vicinity of the second main surface. . The liquid crystal display device according to claim 10, wherein the optical axis of the optically anisotropic unit of the optically anisotropic element is about 90 ° in the vicinity of the second main surface, the angle being from the first main surface. The liquid crystal display device according to claim 7, wherein the polymer liquid crystal is made of a discotic liquid crystal. The liquid crystal display device according to claim 1, wherein the liquid crystal of the driving liquid crystal cell is arranged in a twisted manner between the substrates. The liquid crystal display device according to claim 13, wherein the liquid crystal of the driving liquid crystal cell is a TN liquid crystal. The liquid crystal display device according to claim 1, wherein the liquid crystal of the driving liquid crystal cell is hybridly arranged between the substrates.