JPH04258923A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which is improved in visual angle characteristic and has high visual recognizability by providing specific optically anisotropic elements between a liquid crystal cell and two sheets of polarizing plates holding the liquid crystal therebetween. CONSTITUTION:The optically anisotropic elements 17.1, 17.4 are the biaxially stretched elements having two optical axes within a thickness direction (z-axis direction) and an element plane (the plane normal to the z-axis) and have relations nx>nx, nx=ny between the refractive index nx of the optical axis direction 17.2 within the plane normal to the z-axis and likewise the refractive index ny of the optical axis directions 17.5 or have relations nz>nx, nx>ny, nxnot equal to ny. Further, the twist angle of the liquid crystal cell 4 is set at nearly 90 deg. between two sheets of substrates 4a and 4b.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which contrast ratio and viewing angle dependence of displayed colors are controlled.

0002

2. Description of the Related Art In recent years, liquid crystal display devices, which have the great advantages of being thin, lightweight, and low power consumption, have been actively used as display devices for personal office automation equipment such as Japanese word processors and desktop personal computers. Most liquid crystal display elements (hereinafter abbreviated as LCD) use twisted nematic liquid crystal, and the display method is as follows:
It can be roughly divided into two modes: birefringence mode and optical rotation mode.

[0003] LCDs with a birefringence mode display method using twisted nematic liquid crystals have a molecular arrangement twisted by more than 90 degrees (called the ST method) and have steep electro-optical characteristics, so a switching element is required for each pixel. Even without (thin film transistors or diodes), a large capacity display can be easily obtained by time-division driving even with a simple matrix-like electrode structure. However, because the ST system uses birefringence, the display colors are yellow and dark blue, the so-called yellow mode, and white and blue, the so-called blue mode, making black-and-white or color display impossible. . As a means to eliminate such discoloration of the display, a European patent publication has revealed that a black and white display can be achieved by placing an optically anisotropic element with anisotropy of refractive index within the element plane between the polarizing plate and the liquid crystal cell. It is reported in Publication No. 246842.

[0004] Optical rotation mode LCDs have a molecular arrangement twisted at 90°, and have a fast response speed (several tens of milliseconds), exhibiting a high contrast ratio and good gradation display properties, so they are used in watches, calculators, and even switching devices. By providing each pixel, an LCD (TFT-LCD or MIM-LCD) with a large display capacity, high contrast, and high display performance can be realized.

However, LCDs using twisted nematic liquid crystals have viewing angle dependence, with the display color and contrast ratio changing depending on the viewing angle and direction, and their display performance has not completely surpassed that of cathode ray tube CRTs. .

[0006]

It is generally known that liquid crystal molecules have different refractive indices in the major axis direction and the minor axis direction of the liquid crystal molecules. When polarized light enters a liquid crystal molecule exhibiting such anisotropy of refractive index, the polarization state of the polarized light changes depending on the angle of the liquid crystal molecule. The molecular arrangement of a twisted nematic liquid crystal cell has a structure in which the arrangement of liquid crystal molecules is twisted in the thickness direction of the liquid crystal cell, but the light that passes through the liquid crystal cell is transmitted through each of the liquid crystal molecules in this twisted arrangement. The light propagates while being sequentially polarized depending on the orientation of the liquid crystal molecules. Therefore, the polarization state of the light propagating through the liquid crystal cell is different depending on whether the light is incident perpendicularly to the liquid crystal cell or obliquely, and as a result, the display may vary depending on the direction or angle when viewing the liquid crystal display element. This appears as a phenomenon in which the displayed pattern appears reversed or the displayed pattern becomes completely invisible, which is undesirable from a practical standpoint.

[Configuration of the invention]

[0008]

[Means for Solving the Problems] A first invention provides a liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element. In the liquid crystal cell, the twisted angle between the two substrates is set to approximately 90°, and the optically anisotropic element has a refractive index in the optical axis direction in the element plane of nx, and a refractive index in the optical axis normal direction. If the refractive index of is ny and the refractive index in the thickness direction is nz, then nz
>nx nx=ny.

A second aspect of the present invention is a liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element, wherein the liquid crystal cell has two polarizing plates. The twisted angle between the two substrates is set to approximately 90°, and the optically anisotropic element has a refractive index of nx in the optical axis direction within the element plane, and a refraction index in the optical axis normal direction within the element plane. The liquid crystal display element is characterized in that, where ny is the refractive index and nz is the refractive index in the thickness direction, nz>nx nz>ny nx≠ny.

A third aspect of the invention is a liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element.
At least two liquid crystal cells with twisted orientation are arranged between two substrates, and the optically anisotropic element has a refractive index of nx in the optical axis direction in the element plane, and the optical anisotropic element has a refractive index in the optical axis direction in the element plane. The liquid crystal display element is characterized in that, where ny is the refractive index in the axis normal direction and nz is the refractive index in the element thickness direction, nz>nx nz>ny nx≠ny.

[0011]

[Operation] Generally speaking, there are two main types of arrangement of polarizing plates used in LCD, a liquid crystal device using twisted nematic liquid crystal.
There are two types of liquid crystal cells: one is a liquid crystal cell in which a liquid crystal is placed between two substrates; when no voltage is applied to the liquid crystal cell, light does not pass through; when voltage is applied, light is transmitted (normally closed). The other is a normally open method in which light is transmitted when no voltage is applied to the liquid crystal cell, and light is blocked when voltage is applied. Figure 5 is a diagram showing the dependence of the contrast ratio when the display surface is tilted from 0° to 60° to the left and right from the display surface normal for normally open and normally closed conventional TN systems. (10.0), normally closed (1
1.0). Comparing these, it can be seen that the contrast ratio is less dependent on viewing angle in the normally closed mode than in the normally open mode. The contrast ratio is a value obtained by dividing the brightness in a state where light is transmitted (bright state) by the brightness in a state in which light is blocked (dark state), and the contrast ratio greatly affects the brightness in the dark state. Therefore, when we measured the viewing angle dependence of the luminance in the dark state in the left and right direction for both the normally open and normally closed systems, we obtained the characteristics shown in FIG. 6. The normally open case is shown in (10.1) and the normally closed case is shown in (11.1). As is clear from the figure, the viewing angle dependence of the dark state is smaller in the normally closed mode than in the normally open mode, and as a result, the viewing angle characteristics of the contrast ratio are better in the normally closed mode than in the normally open mode.

Considering the difference between the normally open and normally closed dark states, in the normally open case a voltage is applied to the liquid crystal cell to block light, and the twisted structure of the molecular arrangement state is distorted. Therefore, this distorted molecular arrangement state affects the viewing angle characteristics. Figure 7 shows the molecular arrangement state in the cell when a voltage value indicating a normally open dark state is applied, that is, the tilt angle and twist angle of the liquid crystal molecules. As shown in the figure, when a voltage is applied, the liquid crystal molecules are almost parallel to the electric field near the center of the liquid crystal cell, as shown in the tilt angle 7a, but near the top and bottom of the substrate surface, the alignment regulating force of the substrate surface It is influenced by the electric field and cannot be parallel to the electric field. Further, the twist angle has an S-shaped distribution as shown in 8a. Here, the tilt angle and torsion angle are shown in Figure 8.
In the coordinate system shown in , when the substrate surface of the liquid crystal cell is the xy plane, the long axis of the liquid crystal molecule (8.1) with respect to the xy plane is 8.
The tilt angle 7a of 1L is the tilt angle, and the angle 8a formed by the axis of the liquid crystal molecules (8.1) projected onto the z-axis empty xy plane and the x-axis is the torsion angle. The x-axis corresponds to the rubbing axis of the lower substrate, and the y-axis
The axis corresponds to the rubbing axis of the upper substrate. For example, in order to control the viewing angle characteristics in a normally open dark state, it is necessary to control the viewing angle characteristics so that almost the same polarization state is obtained when light enters the complexly distorted molecular arrangement state from various directions as shown in Figure 7. Optical compensation is necessary. Therefore, it is difficult to optically compensate for the complicatedly distorted molecular alignment state at the same time. The liquid crystal molecules are twisted and the raised portion is optically compensated separately.

[0013] Optically anisotropic bodies such as liquid crystals are three-dimensional xyz
It is described by an axial index ellipsoid. Figure 9 shows a state in which liquid crystal molecules stand vertically using a refractive index ellipsoid, and the birefringence phenomenon is caused by the difference in refractive index within a two-dimensional plane when this refractive index ellipsoid is viewed from a certain direction. Since it is a phenomenon related to z
The refractive index difference when viewed from the direction, that is, when the liquid crystal cell is viewed directly from the front, is different from the refractive index difference when viewed from the visual axis (9.1). Normally Open (Cross Nicol)
In this case, the refractive index difference when viewed from the z direction is 0, so it is a dark state, but when viewed from the visual axis (9.1), there is a refractive index difference, so it is not a dark state.

Therefore, in order to optically compensate for the part near the center of the liquid crystal cell where the liquid crystal molecules are arranged almost perpendicularly to the substrate, a disk-shaped refractive index ellipsoid as shown in FIG. When combined with an ellipsoid, the two-dimensional surface becomes a circle even when viewed from (9.1), and a dark state is obtained.

[0015] Next, when the liquid crystal molecules near the upper substrate are slightly twisted and raised, the portion is viewed from the z direction (cell thickness direction) as shown in Fig. 11. This state is 1
When the refractive index ellipsoid is replaced with one refractive index ellipsoid, the long axis 12.1L of the ellipsoid is slightly shifted from the rubbing axis as shown in FIG. In order to optically compensate such a refractive index ellipsoid, if the same refractive index ellipsoid is arranged perpendicular to the long axis of the refractive index ellipsoid, the difference in the two-dimensional plane when viewed from various observation points is The refractive index difference becomes smaller. If the optical compensation of the alignment state of liquid crystal molecules near the other lower substrate is also performed in the same manner, the viewing angle characteristics will be improved.

Based on the above-mentioned principle, the refractive index ellipsoid that performs optical compensation when arranged at various tilt angles and twist angles in a liquid crystal cell has an optical axis in the element plane and an optical axis in the cell thickness direction. By using an optically anisotropic element having two axes in combination with a liquid crystal cell, it is possible to freely design the contrast ratio and viewing angle characteristics of displayed colors of the liquid crystal display element.

Although the above description has been made by taking the TN liquid crystal cell as an example, similar effects can be obtained not only in the TN type but also in the ST type and the LCD display type with a small twist angle of 90° or less.

[0018]

EXAMPLES Examples of the liquid crystal display element of the present invention will be described in detail below. (Example 1) FIG. 1 shows a cell configuration in this example. 1 and 6 are polarizing plates, and (1.1) and (6.1) correspond to the absorption axes of the polarizing plates. 4 is a liquid crystal cell (4.1),
(4.2) indicates the rubbing axis of the upper and lower substrates 4a and 4b. The rubbing axes (4.1) and (4.2) determine the orientation of the liquid crystal, and are perpendicular to each other to give a twist to the liquid crystal (no voltage applied). The absorption axis (1.1) and the rubbing axis (4.1) of the upper substrate 4a are parallel, and the absorption axis viewing angle direction (6.1) and the rubbing axis (4.1) of the lower substrate 4b are parallel.
．． 2) are parallel.

(17.1) and (17.4) are biaxially stretched optically anisotropic elements having two optical axes in the thickness direction (z-axis direction) and in the element plane (z-axis normal plane), The refractive index nz in the optical axis direction (17.3) in the z-axis direction, the refractive index nx in the optical axis direction (17.2) in the z-axis normal plane, and the optical axis normal direction in the z-axis normal plane (17.5) is different from the refractive index ny, which is larger than the refractive index nx, ny in the thickness direction. (17.1), (17.4
) The retardation value in the z-axis normal plane of the biaxially stretched optically anisotropic element is the thickness of the axially stretched optically anisotropic element (17.8
), (17.9) as d, (nx-nz)×d=300nm, and the retardation value in the z-axis direction is (nx-nz)
xd=-500 nm. The optical axis (17.2) of the biaxially stretched optically anisotropic element (17.1) is placed between the liquid crystal cell 4 and the polarizing plate 1 so that it is parallel to the rubbing axis (4.1) of the upper substrate. It was placed in (17.4) Optical axis (1
7.5) was placed between the liquid crystal cell 4 and the polarizing plate 6 so as to be parallel to the rubbing axis (4.2) of the lower substrate. Further, the retardation value of the liquid crystal cell is 480 nm.

An example of the electro-optical characteristics of the liquid crystal display element of this configuration is shown in FIGS. 13 and 14, and a comparative example shown later is shown in FIG.
5, shown in Figure 16.

FIGS. 13 and 14 show the applied voltage characteristics of the transmittance of the liquid crystal display element of this configuration in the front direction and the lateral direction of the liquid crystal cell. This is the applied voltage characteristic of light transmittance when the cell is tilted. Ideally, it is desirable that the applied voltage characteristics of the light transmittance (standard value) do not change no matter how tilted the liquid crystal cell is. Comparing these figures, it can be seen that the dependence of the transmittance on the viewing angle is smaller in the horizontal direction, especially in the range of applied voltage from about 2.5 V to about 4 V, and the contrast ratio when displaying gradations is lower in this example. Visual angle characteristics were improved. When we measured the viewing angle characteristics of a liquid crystal display element with this cell configuration, we found that a contrast ratio of 35:1 or more was obtained at a 60° cone (observation from a position with an incident angle of 60° from the vertical axis); Even in the above manner, a good black and white display without coloration was obtained without inversion of the displayed image. (Comparative Example) In Example 1, the viewing angle characteristics of the liquid crystal display element were measured when the optically anisotropic element was not disposed between the liquid crystal cell 4 and the upper and lower polarizing plates 1 and 6. The measurement results of the electro-optical characteristics are shown in FIG. 15 in the front direction and in FIG. 16 in the lateral direction. The dark state changes depending on the viewing angle, and a maximum contrast ratio of only 5:1 was obtained with a 60° cone, and when the incident angle exceeded 60°, the displayed image was inverted or not visible at all depending on the viewing direction. (Example 2) In Example 1, (17.1), (1
7.4) The retardation value in the z-axis normal plane of the biaxially stretched optically anisotropic element was 100 nm, and the retardation value in the z-axis direction was -150 nm. Biaxially stretched (17.4) so that the optical axis (17.2) of the biaxially stretched optically anisotropic element (17.1) is parallel to the rubbing axis (4.2) of the lower substrate. The optical axis (17.5) of the optically anisotropic element was arranged to be parallel to the rubbing axis (4.1) of the upper substrate. Similar to Example 1, the electro-optical characteristics of the liquid crystal display element of this example in the front direction and the lateral direction are shown in FIGS. 17 and 18. Especially in the front direction, the applied voltage of the transmittance in the dark state is The viewing angle dependence of the characteristics was small, and as a result, viewing angle characteristics with a high contrast ratio were obtained. When we measured the viewing angle characteristics of a liquid crystal display element with this cell configuration, we found that a contrast ratio of 35:1 or more was obtained at a 60° cone, and a good black and white display with no coloration was obtained, with no inversion of the displayed image even at an incident angle of 60° or more. The display was obtained. (Example 3) In Example 1, instead of the protective film normally provided on the polarizing plates 1 and 6, a protective film (17.
Polarizing plates 1a and 6a integrally formed with biaxially stretched optically anisotropic elements of 1) and (17.4) were prepared, and a liquid crystal display element was prepared with the optically anisotropic element placed on the liquid crystal cell 4 side. Note that in FIG. 2, the same symbols as in FIG. 1 indicate the same parts.

When the viewing angle characteristics of the liquid crystal display element with this configuration were measured, a contrast ratio of 43:1 or more was obtained at a 60° cone, and a black and white display with no coloring was obtained, with no inversion of the displayed image even at an incident angle of 60° or more. A good display was obtained. (Example 4) In FIG. 1, the optically anisotropic element (17.1)
, (17.4) An optically anisotropic element with a retardation value of -100 nm in the thickness direction (z direction) was used. Here, there is no anisotropy in the refractive index in the in-plane direction of the optically anisotropic element, and the refractive index is 1.541. Also, the refractive index in the thickness direction is 1.54
It is 2. The retardation value (=Δnd) of the liquid crystal cell is 480 nm.

FIG. 19 shows the applied voltage characteristics of the transmittance in directions tilted up to 60° at 15° intervals in the horizontal direction from the front direction of the liquid crystal cell. Apply it to the cell and display it. Compared with the characteristics of the comparative example shown below (Fig. 20), in this example, the applied voltage characteristics of transmittance and the applied voltage characteristics of transmittance near 4.5V (dark state) are almost the same. However, the display contrast ratio and viewing angle characteristics were improved. When we measured the viewing angle characteristics of the liquid crystal display element with this configuration, we found that a contrast ratio of 35:1 or more was obtained with a 60° cone, and a good black and white display with no coloration was achieved with no inversion of the displayed image even at an incident angle of 60° or more. was gotten. (Comparative example) In Example 4, the optically anisotropic element was
The viewing angle characteristics of the liquid crystal display element when it is not placed between the upper and lower polarizing plates were measured. Figure 20 shows the measurement results of electro-optical characteristics.
Shown below. The dark state changes depending on the viewing angle, with a 60° cone, the maximum contrast ratio was only 5:1, and when the incident angle was 60° or more, the displayed image was reversed or completely invisible depending on the viewing direction. (Example 5) In Example 4, liquid crystal cell 4 and polarizing plate 1
An optically anisotropic element with a retardation value of -150 nm was placed between the two. An example of the electro-optical characteristics of a liquid crystal display element having this configuration is shown in FIG. When compared with the electro-optical characteristics of the comparative example shown in FIG. 20, the dark state of this example did not change even when the viewing angle was changed, and the viewing angle characteristics of display contrast were improved. When we measured the viewing angle characteristics of the liquid crystal display element with this configuration, we found that a contrast ratio of 38:1 or more was obtained at a 60° cone, and a good black and white display with no coloration was achieved with no inversion of the displayed image even at an incident angle of 60° or more. was gotten. (Example 6) In Example 4, an optically anisotropic element having a retardation value of -300 nm was placed between the liquid crystal cell 4 and the polarizing plate 1. FIG. 22 actually shows an example of the electro-optical characteristics of a liquid crystal display element having this configuration. When comparing the electro-optical characteristics with the comparative example shown in FIG. 20, the dark state does not change even when the viewing angle is changed in this example, and the viewing angle characteristics of the display contrast can be improved. When we measured the viewing angle characteristics of the liquid crystal display element with this configuration, we found that a contrast ratio of 40:1 or more was obtained at a 60° cone, and a good black and white display with no coloration was achieved, with no inversion of the displayed image even at an incident angle of 60° or more. was gotten. (Example 7) In place of the protective films normally formed on the polarizing plates 1 and 6 in Example 4, (17.1) and (17.4) were used.
A polarizing plate integrally formed with an optically anisotropic element was fabricated, and a liquid crystal display element was fabricated. When we measured the viewing angle characteristics of a liquid crystal display element with this configuration, we found that the contrast ratio was 38 at a 60° cone.
: 1 or more was obtained, and a good black and white display without coloration was obtained without inversion of the displayed image even at an incident angle of 60° or more. (Example 8) In place of the protective films of polarizing plates 1 and 6 in Example 5, a polarizing plate in which the optically anisotropic elements of (17.1) and (17.4) were integrally formed was created, and a liquid crystal display element was It was created. When we measured the viewing angle characteristics of the liquid crystal display element with this configuration, we found that a contrast ratio of 40:1 or more was obtained at a 60° cone, and a good black and white display with no coloration was achieved, with no inversion of the displayed image even at an incident angle of 60° or more. was gotten. (Example 9) FIG. 3 shows the cell structure of the liquid crystal display element of this example. Here, the same reference numerals as in FIG. 1 indicate the same parts. 1,
6 is a polarizing plate, 20 is an optically anisotropic element, and 3 and 4 are liquid crystal cells with a twist angle of 90°. If the angle of each axis is shown counterclockwise in the xy plane with the x-axis as a reference, the optical axis (1
．． 1) =45° Optical axis of polarizing plate 6 (6.1) =45° Rubbing axis of upper substrate of liquid crystal cell 3 (3.1) =45
゜Rubbing axis of upper substrate of liquid crystal cell 4 (4.1) = 1
It is 35°.

The refractive index of the optically anisotropic element 20 is in the x-axis direction (
20.2) (optical axis) and the y-axis direction (20.3) are both equally 1.543, and the refractive index in the z-axis direction (20.1) is 1.
．． It is 545. The retardation value of liquid crystal cells 3 and 4 is 500 nm, liquid crystal cell 3 is provided with a transparent electrode, and a voltage is applied to the liquid crystal layer.

When the viewing angle characteristics of the liquid crystal display element with this configuration were measured, a contrast ratio of 35:1 or more was obtained at a 60° cone, and the display image did not invert even at an incident angle of 60° or more, and had good coloration. The display was obtained. (Comparative example) In Example 9, the optically anisotropic element was
and the polarizing plate 1, and the polarizing axis of the polarizing plate 6 (6.
1) The viewing angle characteristics of the liquid crystal display element were measured when the display was placed at an angle of 135°. With a 60° cone, a maximum contrast ratio of only 5:1 can be obtained, and when the angle of incidence exceeds 60°, the displayed image may become inverted or invisible depending on the viewing direction. (Example 10) In Example 9, the optically anisotropic element 20 was placed between the liquid crystal cells 3 and 4. When the viewing angle characteristics of the liquid crystal display element with this configuration were measured, a contrast ratio of 37:1 or more was obtained at a 60° cone, and a good black and white display with no coloration was achieved without inversion of the displayed image even at an incident angle of 60° or more. was gotten. (Example 11) FIG. 4 shows the cell structure of the liquid crystal display element of this example. Note that the same symbols as in FIG. 1 indicate the same parts.

Two optically anisotropic elements 20 are provided between the polarizing plates 1 and 6.
, 50 are disposed, and further inside thereof two liquid crystal cells 3 and 4 each having a twist angle of 90° are disposed adjacent to each other.

When the angles of each axis are shown counterclockwise in the xy plane with the x-axis as a reference, the polarizing axis of the polarizing plate 1 (1.1) = 45° The polarizing axis of the polarizing plate 6 (6.1) = 45° Rubbing axis (3.1) of the upper substrate of liquid crystal cell 3 = 45° Rubbing axis (4.1) of the upper substrate of liquid crystal cell 4 = 135°.

The optical anisotropic element 20 disposed between the polarizing plate 1 and the liquid crystal cell 3 has a refractive index of 1.543 in the optical axis (20.2) direction in the xy plane; The refractive index in the vertical direction in the xy plane is 1.541, and the refractive index in the z-axis direction (20.1
) has a refractive index of 1.545.

The other optically anisotropic element 50 is placed between the polarizing plate 6 and the liquid crystal cell 4. Optical axis in xy plane (50.
2) The refractive index in the direction is 1.543, the optical axis (50.2) and x
The refractive index in the vertical direction (50.3) in the y-plane is 1.541
, the refractive index in the z-axis direction (50.1) is 1.541. Moreover, the thickness (50.5) of the optically anisotropic element 50 is 150n
It is m.

The optical axis (20.2) of the optically anisotropic element 20 is 1
35°, the optical axis (50.2) of the optically anisotropic element 50 is 45°
It is. The retardation value of liquid crystal cells 3 and 4 is 5
00 nm, a transparent electrode is provided in the liquid crystal cell 3, and a voltage is applied to the liquid crystal layer. When the viewing angle characteristics of the liquid crystal display element with this configuration were measured, a contrast ratio of 38:1 or more was obtained with a 60° cone, and a good colored black and white display was achieved with no inversion of the displayed image even at an incident angle of 60° or more. Obtained. (Example 12) In Example 9, liquid crystal cells with a twist angle of 240° were used as the liquid crystal cells 3 and 4, and the liquid crystal cells 3 and 4 were
In No. 4, the twist directions are opposite to each other. The rubbing axis (3.1) of the upper substrate of liquid crystal cell 3 was 60°, and the rubbing axis (4.1) of the upper substrate of liquid crystal cell 4 was 150°. The retardation value of these two liquid crystal cells is 110 nm. The polarization axis (1.1) of polarizing plate 1 is 0°, polarizing plate 6
The polarization axis (6.1) of is 90°. The viewing angle characteristic of the liquid crystal display element with this configuration is that the contrast ratio is 2 at a 60° cone.
0:1 or more, and a good black-and-white display without coloration was obtained without inversion of the displayed image even when the incident angle was 60° or more.

[0031]

According to the present invention, the viewing angle characteristics of a liquid crystal display element using twisted nematic liquid crystal are improved, and a liquid crystal display element with excellent visibility can be obtained. In addition, the present invention can be
It goes without saying that excellent effects can be exhibited even when applied to active matrix liquid crystal display elements using three-terminal or two-terminal elements such as FT and MIM.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a liquid crystal display element according to another embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a liquid crystal display element according to another embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a liquid crystal display element according to another embodiment of the present invention.

FIG. 5 is a diagram illustrating viewing angle characteristics of normally open and normally closed contrast ratios in the horizontal direction of a twisted nematic liquid crystal display element.

FIG. 6 is a diagram illustrating viewing angle characteristics of luminance in a normally open and normally closed dark state in the horizontal direction of a twisted nematic liquid crystal display element.

FIG. 7 is a diagram showing the state of molecular alignment in the thickness direction of the liquid crystal cell when a voltage is applied to the liquid crystal cell.

8 is a diagram showing a coordinate system of tilt angles and twist angles of liquid crystal molecules in FIG. 7. FIG.

FIG. 9 is a diagram showing a three-dimensional refractive index ellipsoid with liquid crystal standing up.

10 is a diagram illustrating a refractive index ellipsoid that optically compensates for the refractive index ellipsoid in FIG. 9. FIG.

FIG. 11 is a diagram showing the arrangement state of liquid crystal molecules existing near the substrate surface.

FIG. 12 is a diagram showing a refractive index ellipsoid equivalent to FIG. 8;

FIG. 13 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effect of Example 1 of the present invention.

FIG. 14 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effects of Example 1 of the present invention.

FIG. 15 is a curve diagram of liquid crystal cell applied voltage (V) vs. light equivalent ratio (standard value) characteristic, explaining the characteristics of a comparative example in comparison with the effects of Example 1 of the present invention.

FIG. 16 is a curve diagram of liquid crystal cell applied voltage (V) vs. light equivalent ratio (standard value) characteristic, for explaining the characteristics of a comparative example in comparison with the effects of Example 1 of the present invention.

FIG. 17 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effect of Example 2 of the present invention.

FIG. 18 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic to explain the effect of Example 2 of the present invention.

FIG. 19 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effect of Example 4 of the present invention.

FIG. 20 illustrates the characteristics of a comparative example in comparison with the effects of Examples 4, 5, and 6 of the present invention, and shows the applied voltage (V) of the liquid crystal cell.
FIG. 3 is a curve diagram of light equivalent ratio (standard value) characteristics.

FIG. 21 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effect of Example 5 of the present invention.

FIG. 22 is a curve diagram of the liquid crystal cell applied voltage (V) versus light equivalent ratio (standard value) characteristic for explaining the effect of Example 6 of the present invention.

[Explanation of symbols]

1, 6...Polarizing plate 4...Liquid crystal cell 17.1, 17.4...Optical anisotropic element

Claims (3)

[Claims] 1. A liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element, wherein the liquid crystal cell is located between two substrates. The twisted angle at is set to approximately 90°,
The optically anisotropic element has a refractive index in the optical axis direction in the element plane of nx, a refractive index in the optical axis normal direction in the element plane as ny, and a refractive index in the thickness direction as nz, then nz>nx nx= A liquid crystal display element characterized by ny 2. A liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element, wherein the liquid crystal cell is located between two substrates. The twisted angle at is set to approximately 90°,
The optically anisotropic element has a refractive index in the optical axis direction in the element plane of nx, a refractive index in the optical axis normal direction in the element plane as ny, and a refractive index in the thickness direction as nz, then nz>nx nz> A liquid crystal display element characterized in that ny nx≠ny 3. A liquid crystal display element comprising two polarizing plates, a liquid crystal cell disposed between these polarizing plates, and at least one optically anisotropic element, wherein the polarizing plate is twisted between the two substrates. At least two oriented liquid crystal cells are arranged, and the optically anisotropic element has a refractive index in the optical axis direction in the element plane of nx, and a refractive index in the optical axis normal direction in the optically anisotropic element plane. When ny is the refractive index in the element thickness direction, nz>n
A liquid crystal display element characterized in that x nz>ny nx≠ny