JP3130686B2 - Liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices having great advantages such as thinness and light weight and low power consumption have been actively used as display devices for personal OA equipment such as Japanese word processors and desktop personal computers. Most liquid crystal display elements use twisted nematic liquid crystal. Among them, TN type and S
They can be roughly classified into two types: TN type.

A TN type liquid crystal display device has a 90 ° twisted molecular arrangement and exhibits a high contrast ratio at a low voltage, so that it is widely used not only for displays of watches and calculators but also for displays of liquid crystal televisions and OA equipment. Have been. In particular, displays for LCD televisions and OA equipment
Since large display capacity and high-speed operation are required, an active matrix method in which a switching element such as a thin film transistor (TFT) or a diode is formed in a portion corresponding to each display pixel is applied.

On the other hand, STN type liquid crystal display elements have a large twisted molecular arrangement of, for example, 240 ° and have steep electro-optical characteristics. Therefore, even if there is no switching element for each pixel, a simple matrix electrode is used. Large capacity display can be obtained with the structure. However, since the birefringence effect is used, a so-called yellow mode display of yellow and dark blue or a so-called blue mode display of white and blue (display colors differ depending on the directions of absorption axes of polarizing plates above and below the liquid crystal cell) And black-and-white display was impossible. Japanese Patent Publication No. 63-53528 discloses that a black-and-white display can be realized by disposing a second liquid crystal cell, which is twisted reversely, between a polarizing plate and a liquid crystal cell as means for eliminating such coloring of display. . The principle of this black-and-white conversion is that the light of the ordinary light component and the extraordinary light component, which have become elliptically polarized light in the display liquid crystal cell in which the liquid crystal molecules are arranged in a twisted arrangement, are interchanged by the second liquid crystal cell which is an optical compensator. The elliptically polarized light is converted to linearly polarized light. As a result, the same polarization can be obtained without the polarization direction being different for each wavelength of light, and a monochrome display can be realized. Here, as described above, in order to convert elliptically polarized light into linearly polarized light, the second liquid crystal cell has substantially the same retardation value as that of the first liquid crystal cell to which a voltage is applied, and has a twisting direction between each other. On the contrary, their arrangement is configured such that the liquid crystal molecules closest to each other have orthogonal orientation directions.

[0005] However, these STN and TN liquid crystal display elements have a viewing angle dependency such that the display color and contrast ratio change depending on the viewing angle and azimuth, and the display performance of the color picture tube CRT is completely exceeded. I don't want to. For example, the viewing angle characteristics of a TN type liquid crystal display element have characteristics as shown in FIG. FIG. 2 is called an isocontrast characteristic, and is often used to show the viewing angle characteristic of a liquid crystal display element. A point at which the liquid crystal display element is observed is defined as an azimuth angle Φ and a viewing angle θ as shown in FIG. 3, and when the azimuth Φ to be observed is changed,
A viewing angle θ showing an equal contrast ratio is shown in a polar coordinate system as shown in FIG. For an ideal liquid crystal display device, it is desired that the viewing angle be large at any azimuth. As can be seen from the measurement results of FIG. 2, the viewing angles are large in the 90 °, 210 °, and 330 ° azimuths, and are small in the 45 °, 135 °, and 270 ° azimuths. As in this example, when the viewing angle is changed, the same contrast ratio cannot be obtained in the liquid crystal display element, and the contrast ratio greatly changes depending on the viewing angle and azimuth.

On the other hand, with respect to a liquid crystal display device having a structure in which a liquid crystal cell in which nematic liquid crystal having negative dielectric anisotropy is vertically aligned is sandwiched between polarizing plates, an attempt is made to improve a viewing angle by sandwiching a cholesteric liquid crystal between the liquid crystal cell and the polarizing plate. Is disclosed in JP-A-3-67.
No. 219. However, in this case, the liquid crystal cell in which the nematic liquid crystal with negative dielectric anisotropy is vertically aligned has the problem of the alignment technology, the problem of the response speed of the liquid crystal material, or the active matrix driven liquid crystal because the ratio of the liquid crystal does not become so high. It is not suitable for use in display, and the above-mentioned TN type and STN type are desirable as the nematic liquid crystal.
This technique has practical problems.

[0007]

At present, a liquid crystal display element does not have a characteristic such that it exhibits a substantially uniform contrast ratio from any point of view like a CRT, but the contrast ratio greatly changes depending on the viewing angle and azimuth. That is, the liquid crystal display element has a viewing angle characteristic. Therefore, the liquid crystal display element has a narrow viewing angle characteristic and is good only in a direction in which the contrast ratio is limited, and otherwise the visibility of the display is extremely poor. The present invention solves the above disadvantages.

[0008]

According to the present invention, there is provided a liquid crystal cell having a liquid crystal layer sandwiched between two substrates having electrodes, a liquid crystal cell, and an optical path passing through the liquid crystal cell. In a liquid crystal display element comprising an optically anisotropic element disposed and two polarizing plates sandwiching the liquid crystal cell and the optically anisotropic element, the liquid crystal cell has two or more types of alignment regions in the cell. According to the present invention, there is provided a liquid crystal display element characterized in that the optically anisotropic element has a portion having two or more kinds of optical characteristics in the element plane.

Further, the optically anisotropic element may be made of a polymer liquid crystal and a liquid crystal.

[0010]

The present invention achieves the above-mentioned object, and its principle and method will be described below. FIG.
FIG. 9 shows viewing angle characteristics of a normally open TN type liquid crystal display element (hereinafter referred to as a TN type liquid crystal display element) of a conventional example at the time of gradation display. The transmittance is shown when the display surface is inclined from 0 ° to 60 ° in the horizontal direction from the display surface normal (the angle of inclination from the display surface normal is hereinafter referred to as a viewing angle). Numerals 1 to 8 in the drawing indicate the respective gradation levels at the time of gradation display, and are numbered in order from the highest transmittance at the front (viewing angle 0 °). In this case, the viewing angle characteristic at the time of 8-level gradation display is shown. It is desired that the order of the transmittance at least from the 1st to the 8th level is the same as that in the front. As shown in this figure, the gradation order changes at a viewing angle of about 30 ° or more in both left and right directions.

On the other hand, FIG. 5 shows a viewing angle characteristic at the time of gradation display in the vertical direction. The characteristics of the upper direction are extremely poor,
The gradation order changes at a viewing angle of 10 ° or more, and the transmittance of the gradation levels from 2 to 8 levels is significantly reduced. Conversely, in the characteristics at the lower position, although the transmittance is increased, the gradation order does not change significantly as in the case of the upper direction, and the change in the gradation order is small. These causes are due to the molecular arrangement in the liquid crystal cell. When a voltage is applied to the liquid crystal cell, the liquid crystal molecules in the liquid crystal cell tilt with respect to the substrate.

FIG. 6 is a diagram schematically showing a cross section of the liquid crystal cell when a voltage is applied from the power supply 15 to the liquid crystal cell.
Reference numeral 16 denotes liquid crystal molecules, and the liquid crystal molecules 16 are tilted with respect to the substrate 13a or 13b by the applied voltage, so that the liquid crystal molecules 16 are arranged so as to continuously spread in the thickness direction of the liquid crystal cell. In a TN-type liquid crystal display element, the degree of optical rotation is controlled to transmit or block light. However, when the light passes through the liquid crystal cell, the optical rotation is lost and the light is transmitted as the longer axis of the liquid crystal molecule becomes parallel to the light beam. Light decreases. At both the observation point A and the observation point A 'in the figure, the light beam and the liquid crystal molecules are parallel, and transmitted light cannot be obtained. On the other hand, in the azimuth of point B, which is the opposite azimuth, even if the viewing angle is slightly changed, the light rays are not parallel to the liquid crystal molecules, and transmitted light is obtained to some extent. As described above, the liquid crystal display element has a direction in which the optical rotation is likely to disappear, and the upward direction in FIG. 5 shown earlier corresponds to this direction.

In order to improve the viewing angle characteristic at the time of gradation display, a liquid crystal molecule alignment portion where optical rotation is hardly lost even when the viewing angle is changed, for example, an alignment region 13A and a target alignment region 13B as shown in FIG. If added to the display pixels, improvement in display performance can be expected.

FIG. 8 shows an 8-level gray scale in the vertical direction of a liquid crystal display element in which two types of alignment regions in which a direction in which liquid crystal molecules incline when voltage is applied are opposite to each other are provided at a ratio of 1: 1. This is a viewing angle characteristic at the time of display. Even when the viewing angle increases, the gradation order does not change much. However, the luminance at three or more levels increases with an increase in the viewing angle. For example, in the case of performing color display using three or more levels of gradation, a change in the viewing angle greatly changes the color tone. As described above, when the orientation in the display pixel is composed of a plurality of orientation parts, the viewing angle dependency of the order of gradation display is improved, but the original set value observed in the front direction cannot be obtained. This causes a change in display color.

The diversification of the orientation in the display pixels of such a liquid crystal cell can be achieved by not only a method of producing a large number of orientations in which the tilt directions of the liquid crystal molecules are different in one pixel as shown in the example of FIG. An alignment film having a different tilt angle (pretilt angle) of the liquid crystal molecules near the boundary between the substrate and the liquid crystal molecules is provided in the pixel, whereby one pixel is formed.
There is a method of producing more than one kind of alignment part, a method in which the type of alignment is the same, a method in which a capacitor is provided on an electrode, and a voltage applied to one pixel is made different in a pixel to have a different arrangement, In any case, a change in the retardation value of the liquid crystal layer due to a change in the viewing angle cannot be avoided. The present invention can be applied to a multi-alignment liquid crystal cell in one pixel by any method.

In order to suppress a change in transmittance due to a change in viewing angle, the following method is possible. Hereinafter, this principle will be described.

FIG. 9 shows, as an example, a liquid crystal cell in a vertical alignment state by a three-dimensional refractive index ellipsoid 9. The z axis is the thickness direction of the liquid crystal cell, and the xy plane corresponds to the substrate surface of the liquid crystal cell. The birefringence phenomenon is a normal line on the center point of the refractive index ellipsoid 9 connecting the observation point when the center point of the refractive index ellipsoid 9 is viewed from a certain direction and the center point of the refractive index ellipsoid 9. The surface is indicated by the shape of an elliptical cut surface formed when the refractive index ellipsoid 9 is cut (here, referred to as a refractive index body in a two-dimensional plane). If the difference between the long axis and the short axis of the refractive index body in this two-dimensional plane corresponds to the phase difference between ordinary light and extraordinary light, and the transmission axes of the polarizing plates sandwiching the liquid crystal cell are orthogonal to each other, When the phase difference is zero, the transmitted light of the liquid crystal cell is blocked, and when the phase difference is not zero, transmitted light corresponding to the phase difference and the wavelength of the incident angle is generated. When light is vertically incident on the substrate surface of the liquid crystal cell (that is, when the liquid crystal cell is viewed from the front), the refractive index body (9.4) in the two-dimensional plane becomes a circle, and the phase difference between ordinary light and extraordinary light becomes Zero, but in a direction inclined from the substrate surface of the liquid crystal cell
When light enters from (9.1), the refractive index body (9.5) becomes elliptical, a phase difference occurs between ordinary light and extraordinary light, and the polarization state of light passing through the liquid crystal cell is different between the frontal direction and the oblique direction.

As the angle at which the refractive index ellipsoid 9 in FIG. 9 is viewed, that is, the viewing angle (9.3) is increased, the refractive index body (9.5) in the two-dimensional plane of the visual axis (9.1) becomes longer in the length direction of n91. The transmitted light is larger than when viewed from the direction of the visual axis (9.1). Ideally, when the viewing angle changes in any orientation, 2
It is desirable that the shape of the refractive index body in the dimensional plane does not change.

Such optical compensation is performed by disposing a refractive index ellipsoid 9c on a disk as shown in FIG. 10 on an optical path passing through the refractive index ellipsoid 9 in FIG. 9 (for example, on a liquid crystal cell or (Disposed adjacently below).
Thus, when the viewing angle (9.3) is increased, the refractive index body (9.5) in the two-dimensional plane of the refractive index ellipsoid 9 increases in the length direction of n91, whereas the length of n92 increases. The refractive index in the direction becomes large, and as a result, the combined refractive index body in the two-dimensional plane becomes a circle, the refractive index ellipsoid 9 can be optically compensated, and the viewing angle characteristics are improved.

Actually, the refractive index ellipsoid 9c as shown in FIG. 10 is a film of a material exhibiting negative optical anisotropy in the thickness direction (the refractive index in the thickness direction is smaller than the refractive index in the plane direction), A film of a material having this property has a biaxial optical anisotropy in which the optical axis is displaced from the thickness direction, or an optical anisotropic material layer having an optical anisotropic material layer in which the optical axis is continuously twisted. It can be realized by the one element. In order to make the viewing angle characteristic of the liquid crystal display element at the time of gradation display more desirable, these optically anisotropic elements are used in combination, and each alignment unit having a different viewing angle characteristic in a multi-alignment liquid crystal cell in one pixel. Can be realized by accurately performing optical compensation with an optically anisotropic element having optical characteristics suitable for each.

Generally, a liquid crystal cell emits light in a visible wavelength region (generally 380 nm) by a voltage applied to the liquid crystal cell.
(The region from to 750 nm) is positively changed. On the other hand, in the case of an optically anisotropic element for optical compensation, the optical axis of the optically anisotropic material layer is continuously twisted, so that optical rotation may occur depending on the optical conditions of the optically anisotropic element. Here, the optical rotation indicates a property in which the vibration direction of the light turns left or right around the traveling direction as the light travels through the medium. When the retardation value of an optically anisotropic element whose optical axis is continuously twisted is constant and the twist pitch of the optical axis is long, light rotates its polarization plane according to the twist of the optical axis, but the twist of the optical axis When the pitch is short, the light cannot follow the twist of the optical axis, and the optical rotation phenomenon does not occur. If the optical rotation of the optically anisotropic element is large, the polarization plane of light passing through the element is changed, and as a result, the contrast ratio is reduced,
In some cases, the polarization plane changes variously depending on the wavelength of the light, which causes a problem that the light transmitted through the optically anisotropic element is colored. Therefore, it is necessary to make at least the optical rotation of the optically anisotropic element to visible light smaller than that of the driving liquid crystal cell to visible light.

By the way, the value of the product n × p of the length p of the twist pitch and the refractive index n is in the visible wavelength range (depending on conditions, the short wavelength end is 360 nm to 400 nm, and the long wavelength end is 760 nm to 830 nm). ) Causes selective scattering (JLFergason; Molecular Crystals.
1. See 293 (1966)). When selective scattering occurs, a coloring phenomenon of the optically anisotropic element occurs and the display color changes. Therefore, the average refractive index n of the optically anisotropic material layer forming the optically anisotropic element,
If the product n × p with the twist pitch p of the optical axis is excluded from the visible wavelength range, the coloring phenomenon can be prevented. However, this is not the case when color display is performed using selective reflection of the optically anisotropic element.

As described above, the principle of viewing angle expansion or viewing angle control in the present invention has been conceptually explained. At this time, the refractive index ellipsoid of the driving liquid crystal cell to which a voltage equal to or higher than the threshold voltage described above is applied. It is not a simple ellipsoid as shown in FIG. FIG. 11 shows a calculation of the molecular alignment state in the liquid crystal cell when a voltage having a value that can obtain a dark state is actually applied to the TN mode driving liquid crystal cell. FIG.
In the figure, TI and TW are a tilt (tilt) angle and a twist (twist) angle, respectively. The tilt angle is defined by the liquid crystal molecules LC with respect to the xy plane, as shown in FIG. Indicates the angle of inclination of the long axis LCA, and the twist angle indicates the angle between the axis that projects the liquid crystal molecules LCA from the z axis to the xy plane and the x axis.

In a state where a voltage is applied, the liquid crystal molecules tilt near 90 ° near the center of the liquid crystal cell, but do not tilt much near the upper and lower substrate surfaces due to the influence of the alignment regulating force on the substrate surfaces. . The twist angle has an S-shaped distribution. As is apparent from the calculation results, the molecular arrangement of the liquid crystal layer when a voltage is applied is not completely vertical. Therefore, when a voltage is applied to a liquid crystal cell having a twisted arrangement, the refractive index ellipsoid of the liquid crystal cell does not have a simple shape as shown in FIG. The shape of FIG. 9 is deformed under the influence of the twist arrangement portion near the surface. Therefore, the refractive index ellipse for optical compensation used in the driving liquid crystal cell of the TN mode or the ST mode is adapted to the refractive index ellipse of the driving liquid crystal cell,
It is desirable to have a complex shape slightly deformed instead of a perfect disk shape as shown in FIG.

The optically anisotropic element is formed by laminating a retardation film having optical anisotropy by stretching a polymer film, a liquid crystal cell having a twisted arrangement, and a polymer liquid crystal. Can be realized by a thin film having a twisted arrangement. In this case, for example, the polymer layer is obtained by applying the polymer layer to at least one of the substrates of the driving liquid crystal cell, which facilitates the production and provides a more desirable liquid crystal display element. For example, a high molecular weight copolymer having a polysiloxane main chain and biphenylbenzoate and cholesteryl groups in a side chain at an appropriate ratio can be used.

Further, in order to perform better compensation, it is possible to obtain desired characteristics by arranging an optically anisotropic element suitable for each alignment portion on the optical path of each alignment portion of the liquid crystal cell. is there.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the liquid crystal display device of the present invention will be described below in detail.

Embodiment 1 FIG. 1 is a sectional view of a liquid crystal display device according to this embodiment. The liquid crystal display element 10 has two polarizing plates 11 and 14 (LLc2-92) on an optical path z of light passing through the element.
-18: manufactured by SANRITZ), a liquid crystal cell 12 as an optically anisotropic element for compensating viewing angle, and a driving liquid crystal cell 13 between them.
Are sandwiched between them. The polarizing plate 11 is a transparent substrate 11
b, a polarizing film 11a is attached inside the
Similarly, No. 4 is formed by attaching a polarizing film 14a to a transparent substrate 14b.

The driving liquid crystal cell 13 is disposed between the viewing angle compensating polymer liquid crystal 12 and the polarizing plate 14. The upper substrate 13a and the lower substrate 13b are provided with transparent electrodes 13c and 13d, respectively, and are connected to the driving power supply 15. Two types of alignment regions 13A and 13B having different inclination directions between them (FIG. 1)
3) are provided in the pixel at an equal ratio in a configuration described later, and a twisted nematic liquid crystal (ZLI-4827 (manufactured by E. Merck)) is used.
Liquid crystal composition in which a chiral agent S811 (manufactured by E. Merck) is mixed in) The liquid crystal layer 13e is introduced at a twist angle of 90 °, and twists counterclockwise (left-hand twist) from the upper substrate 13a to the lower substrate 13b. The state changes according to the applied voltage from the drive power supply 15.

FIG. 13 is a view showing the structure of the liquid crystal layer 13e. Two types of alignment regions 13A and 13B are formed in a stripe shape. Each pixel has a rectangular shape and is surrounded by the non-pixel region 12B. The alignment regions 13A and 13B are formed by performing an alignment process (rubbing) on the alignment films formed on the transparent electrodes 13c and 13d, and the control of the regions is performed in such a manner that the rubbing directions are opposite to each other in the regions 13A and 13B. It was realized by doing so. The thickness of the liquid crystal layer is 5.5
μm.

In the orientation region 13A, liquid crystal molecules rise in the direction of arrow A in the figure when a voltage is applied, and in the orientation region 13B, the liquid crystal molecules rise in the direction of the arrow B in the diagram when a voltage is applied. RA and RB in the figure are:
It is a rubbing direction of the area of 13A and 13B on the substrate. As a result, as shown in FIG. 15, each pixel p of the driving liquid crystal cell 13 has 8 × 8 fine alignment regions 13L and 13R in this embodiment in a rectangular region surrounded by the non-pixel region 12B.
Are formed alternately adjacent to each other.

As an optically anisotropic element, a viewing angle compensating polymer liquid crystal 12 is provided on a polarizing plate 11 on a substrate 13 a of a driving liquid crystal cell 13.
A polymer liquid crystal having a birefringence anisotropy Δn of 0.2 having a polysiloxane main chain and a bichain benzoate and a cholesteryl group on the side surface is 0.25 μm thick.
Is formed. The viewing angle compensating polymer liquid crystal 12 is 12 L,
It is composed of three types of alignment regions 12R and 12B, that is, portions having different optical characteristics, and is divided into eight rows and eight columns as shown in FIG. 14 corresponding to FIG. Are formed in an adjacent configuration. The alignment region 12L has a twisting angle of 5 in a counterclockwise arrangement.
2.5 °, the helical pitch is 1.71 μm. The alignment region 12R has a twist angle of 52.5 ° in a clockwise arrangement and a helical pitch of 1.71 μm. However, a region indicated by reference numeral 12B surrounding a square pixel in the drawing is a non-pixel region, and the arrangement portion is in a dark state when the twist angle is 90 ° clockwise, forming a black matrix.

In the above structure, the upper substrate 13a is a pixel electrode and a TFT element, and the lower substrate 13b is a common transparent electrode and a TFT driving liquid crystal using a substrate composed of a color filter of three primary colors of red, green and blue for each pixel. A display element was created.
A gradation signal voltage corresponding to the display color was applied to each display pixel in order to perform full color, and a change in the viewing angle of the display color was observed. As a result, a favorable display in which the display color did not change up to a viewing angle of 35 ° in all directions was obtained.

COMPARATIVE EXAMPLE In Example 1, a TFT-driven liquid crystal display element having a configuration in which the viewing angle compensating liquid crystal cell 12 was not provided was prepared, and the same visual evaluation as in Example 1 was performed. Good gradation display properties were observed up to about 30 °, but in the up and down azimuths, a slight change of the viewing angle from the front slightly turned whitish, causing a practical problem.

Embodiment 2 FIG. 16 is a sectional view of a liquid crystal display device according to this embodiment. The liquid crystal display element 20 has a configuration in which a driving liquid crystal cell 23 is sandwiched between two polarizing plates (LLC2-92-18, manufactured by Sanritz) 21 and 24. The driving liquid crystal cell 23 includes an upper substrate 23a having a color filter,
This is a structure in which a liquid crystal layer 23e is sandwiched between lower substrates 23b having TFT elements.

On the upper substrate 23a, a transparent electrode 23C made of ITO is provided on a color filter formed of three colors of red R, green G, and blue B provided on a glass plate 23F. A film 24C is formed. On the lower substrate 23b, a transparent electrode 23d electrically connected to the TFT element is formed on a glass 23F, and an alignment film 24B is formed thereon. On the alignment film 24B, a polymer liquid crystal 22 having a birefringence anisotropy Δn of 0.2 whose side chain is composed of biphenylbenzoate and a cholesteryl group is formed. In addition, the part of the code | symbol 22B in the upper substrate 23a shows a black matrix.

FIG. 17 is a partial plan view of the liquid crystal display device. The dotted arrow 30 in the figure indicates the rubbing direction of the alignment film 24B on the lower substrate 23b, whereby the polymer liquid crystal 22 is aligned. Rubbing of the upper substrate 23a
The direction is parallel and opposite. High polymer liquid crystal 22
Is composed of portions 22R and 22L by exposure, the directions of which are opposite to each other, 22R is right-handed, and 22L is left-handed. The high-molecular liquid crystal 22 has a twist angle of 90 ° and the side in contact with the liquid crystal 23e has a solid arrow 3 in the drawing.
Arrange along 1.

A twisted nematic liquid crystal (ZLI-4287, E, Merck) mixed with a left-handed chiral agent (S811, E, Merck) is twisted between the upper and lower glass substrates 23A, 23B. The liquid crystal layer 23e is introduced at an angle of 90 ° to form a liquid crystal layer 23e. In the case of the present embodiment, the alignment films 24A, 24B, and 24C of the upper and lower substrates used have different pretilt angles, which are 1 °, 4 °, and 6 °, respectively. With such a combination, two types of alignment regions 23L and 23U are formed, and the directions in which the liquid crystal molecules are tilted by voltage application are exactly opposite. The thickness of the liquid crystal layer is 5.5 μm.

A TFT-driven liquid crystal display device having the above-described structure was prepared, and a signal voltage corresponding to a display color was applied to each pixel electrode to perform color display. A good display in which the display color did not change up to 38 ° was obtained.

[0040]

According to the present invention, it is possible to provide a liquid crystal display device of high quality display with improved viewing angle characteristics of the liquid crystal display device and excellent visibility.

It goes without saying that excellent effects can be obtained even when the present invention is applied to an active matrix liquid crystal display device using a three-terminal or two-terminal device such as a TFT or MIM.

[Brief description of the drawings]

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

FIG. 2 is a view for explaining equal contrast characteristics of a conventional TN type liquid crystal display device.

FIG. 3 is a view for explaining a coordinate system of observation points in FIG. 2;

FIG. 4 is a view showing the viewing angle dependence of the transmittance of a conventional TN-type liquid crystal display device when displaying gray scales in left and right directions.

FIG. 5 is a view showing the viewing angle dependency of the transmittance of a conventional TN type liquid crystal display element when displaying gray scales in the vertical direction.

FIG. 6 is a view for explaining the principle of generation of viewing angle dependence of a liquid crystal display element.

FIG. 7 is a view for explaining the principle of improving viewing angle dependence of a liquid crystal display element.

FIG. 8 is a view showing the viewing angle dependency of the transmittance of a liquid crystal display element having two types of alignment regions in one pixel when displaying gradation in the vertical direction.

FIG. 9 is a diagram illustrating a three-dimensional refractive index ellipsoid of a vertically aligned liquid crystal cell.

FIG. 10 is a diagram illustrating a refractive index ellipsoid of an optically anisotropic element that performs viewing angle compensation.

FIG. 11 illustrates a molecular arrangement of a liquid crystal cell to which a voltage equal to or higher than a threshold is applied.

FIG. 12 is a diagram showing a coordinate system of a molecular arrangement of a liquid crystal cell.

FIG. 13 is a plan view illustrating the configuration of the optically anisotropic element according to the first embodiment.

FIG. 14 is a plan view illustrating the orientation of the driving liquid crystal cell according to the first embodiment.

FIG. 15 is a plan view showing the distribution of pixels and liquid crystal molecule alignment regions of the driving liquid crystal cell of Example 1.

FIG. 16 is a cross-sectional view illustrating the configuration of the second embodiment.

FIG. 17 is a plan view illustrating the orientation in Example 2.

[Explanation of symbols]

 11, 14 ... polarizing plate 12 ... optical anisotropic element, 12L, 12R ... alignment region 13 ... driving liquid crystal cell, 13A, 13B ... alignment region of driving liquid crystal cell

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jin Hato 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Corporation Yokohama Office (56) References JP-A-4-55827 (JP, A) JP-A-4 −55813 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1337 505 G02F 1/13363 G02F 1/1347

Claims (2)

(57) [Claims] 1. A driving liquid crystal cell having a liquid crystal layer sandwiched between two substrates each having an electrode, an optically anisotropic element disposed on an optical path passing through the driving liquid crystal cell, and the driving liquid crystal cell; In a liquid crystal display element comprising two polarizing plates sandwiching an optically anisotropic element, the driving liquid crystal cell has two or more types of alignment regions in the cell, and the optically anisotropic element corresponds to this alignment. A liquid crystal display device comprising a portion having two or more kinds of optical characteristics in a device plane. 2. The liquid crystal display device according to claim 1, wherein the optically anisotropic element is made of a polymer liquid crystal or a liquid crystal.