JPH0784272A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [Object] To provide a liquid crystal display device capable of realizing a high-quality display by increasing the contrast of the display surface of a large liquid crystal display panel. The transparent electrode of the first liquid crystal cell is composed of picture element electrodes arranged in a matrix and signal lines arranged between the picture element electrodes and extending in parallel to each other in a predetermined direction,
The pixel electrode and the signal line are connected by a photoconductive element, and in the vicinity of the liquid crystal display panel except the display surface side,
A liquid crystal layer is sandwiched between transparent electrodes, and an illumination light source control panel having at least a transparent substrate provided on the back surface is provided, and the transparent electrodes on the back surface side of the panel are composed of a plurality of electrodes. The element electrodes are formed in a strip shape having a width equal to the dimension in the extending direction of the signal line, and are arranged in the extending direction of the signal line, and selectively guide the light of the illumination light source to the photoconductive element. .

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 used as a display for displaying images, images, character information and the like, and more particularly to a large screen liquid crystal display device.

[0002]

2. Description of the Related Art Conventional matrix display liquid crystal panels are roughly classified into two types, one is a simple matrix display as shown in FIG. 4 and the other is as shown in FIG. Some have an active matrix display.

First, in the simple matrix display shown in FIG. 4, strip-shaped transparent electrodes 49a and 49b are horizontally arranged on the back side of the transparent substrate 52 and on the transparent substrate 53, respectively. The liquid crystal composition 54 is sandwiched between the transparent substrates 52 and 53 in a state where the transparent electrodes 49a and 49b are opposed to each other so as to be orthogonal to each other. In the liquid crystal panel having this configuration, the transparent electrode 49a and the transparent electrode 49b function as the scanning line 50 and the signal line 51, respectively. Further, the liquid crystal panel having this structure is driven by applying a pulse-division electric field for time-divisional driving to light these crossing transparent electrode portions.

In the active matrix display shown in FIG. 5, pixel electrodes 56 are arranged in a matrix on one substrate 55 of a liquid crystal panel, and three-terminal thin film transistors 57 (in the vicinity of each pixel electrode 56 ( TFT) is formed. These three terminals are connected to the pixel electrode 56, the scanning line 58 made of a metal film insulated at the intersection, and the signal line 59, respectively. On the other hand, the transparent substrate 6
1, a transparent electrode 60 is formed on the lower surface thereof. The liquid crystal material 6 is provided between the transparent substrate 61 and the substrate 55.
It has a structure in which 2 is sandwiched. The liquid crystal panel of this structure is driven by energizing selected scan lines and signal lines, and applying a display electric field to the picture element electrodes by the switching action of the transistor connected to the intersection of both lines. Has been done. The transparent electrode 60 is provided on one transparent substrate 61 as a common electrode, and basically serves as a static drive.

[0005]

By the way, in the prior art, a small liquid crystal television size of, for example, about 3 to 10 inches does not cause any problem, but when it is used for a large display, for example, a high-definition television exceeding 40 inches. Then, there is a limit in the conventional driving method. That is, in the example of a high-definition television, a diagonal of 40 inches (scan lines 1, 12
Although five (5) panels are used, there is a problem that a simple matrix display requires a large number of time divisions and sufficient contrast cannot be obtained. In the active matrix display, a large number of TFTs (in this case, 1,125 (scan lines) × 1,875 (signal lines) × 3 (corresponding to RGB color) = 6,328,125 (number of picture elements: number of TFT elements)) However, there is a problem in that it is very difficult in manufacturing that the characteristics are made uniform and there are few defects.

The present invention has been made to solve these problems, and a liquid crystal display device capable of realizing a high quality display by increasing the contrast of the display surface of a large liquid crystal display panel. The purpose is to provide.

[0007]

In order to achieve the above object, a liquid crystal display device of the present invention comprises a first liquid crystal cell in which a liquid crystal layer is sandwiched between transparent electrodes, and the first liquid crystal cell of the first liquid crystal cell. A liquid crystal display panel provided with a transparent substrate formed on each of the display surface and the back surface, a light source arranged behind the liquid crystal display panel, and the liquid crystal display panel for modulating the intensity of light from the light source. In a liquid crystal display device including a control unit that controls driving, the transparent electrodes on the transparent substrate formed on the back side are arranged in a matrix, and the transparent electrodes are arranged between the pixel electrodes. A signal line extending parallel to each other in a predetermined direction, and the pixel electrode and the signal line are connected by a photoconductive element, and in the vicinity of the display panel except the display surface side of the liquid crystal display panel. In the liquid An illumination light source control panel including a second liquid crystal cell in which a layer is sandwiched between transparent electrodes and a transparent substrate provided at least on the back surface of the second liquid crystal cell is provided, and the illumination light source control panel is provided. The transparent electrodes on the back side of the panel are composed of a plurality of strip electrodes each having a width equal to the dimension of the picture element electrodes in the extending direction of the signal lines and arranged in the extending direction of the signal lines. In addition, it is characterized in that a second control unit for driving and controlling the illumination light source control panel is provided to selectively guide the light of the illumination light source to the photoconductive element.

[0008]

[Operation] The display on the back panel is constantly turned off by the transparent electrodes in the form of strips, and the panel for controlling the illumination light source is driven,
The strip-shaped transparent electrodes are sequentially turned on, and the light source serves as a scanning line in the direction along the strip-shaped transparent electrodes. Then, the scanning line is incident on the photoconductive element of the liquid crystal display panel section, the signal line and the pixel electrode are electrically connected, and a potential corresponding to the signal information of the scanning line is applied to the pixel electrode. . Further, an electric field is applied between the signal line and the transparent electrode on the display side, and the liquid crystal sandwiched between them changes the orientation, and a predetermined display is performed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the embodiment of the present invention.

This liquid crystal display device has a two-layer structure using three glass substrates. First, an upper surface deflection plate 5 is formed on the upper surface of the upper surface transparent substrate 1, and a color filter 4, a transparent electrode 2, and an alignment film 3 are sequentially formed on the rear surface. The transparent electrode 2 is formed by depositing ITO (Indium Tin Oxide) or the like. The alignment film 3 is coated with polyimide resin or the like. As the alignment treatment of the alignment film 3, fine grooves are formed on the alignment film 3 by a rubbing method.

A matrix-shaped picture element electrode 9 is formed on the intermediate transparent substrate 6, and a signal line 8 on the input side for liquid crystal display is provided between the picture element electrodes 9 along a predetermined direction. Are arranged in parallel. In addition, the signal line 8 and the pixel electrode 9
A photoconductive film 10 for electrically connecting them is formed between and. The signal line 8 is formed by patterning a metal film made of chromium or nickel by a photolithography process, and the pixel electrode 9 is also formed by patterning ITO. Is. The photoconductive film 10 is formed by vapor deposition and patterning of a photoconductive material such as CdS or amorphous polysilicon.

Furthermore, on the lower transparent substrate 13, strip-shaped transparent electrodes 1 patterned in strips in the scanning line direction.
4 and the alignment film 15 are laminated, and the lower surface deflection plate 16 is attached to the rear surface of the lower surface transparent substrate 13.

Further, a backlight 17 such as a cold cathode tube is installed at a position where it passes through the three transparent substrates 1, 6, 13 from below. The transparent substrates 1, 6 having the above structure
13 is a sealant (not shown) made of epoxy resin or the like with an interval of several μm to several tens of μm (this interval is controlled by the size of the spacer using glass fibers, beads, etc.). These substrates 1, 6 in a rectangle
Only the outer peripheral portion of 13 is separated and bonded, and the twisted nematic liquid crystal 18 is provided between the upper transparent substrate 1 and the intermediate transparent substrate 6, and the intermediate transparent substrate 6 and the lower transparent substrate 1 are bonded together.
A guest-host liquid crystal 19 is filled in between 3 and 3 (the sealing method is not shown).

The operation of the embodiment of the present invention having the above construction will be described below with reference to FIG. Note that this drawing is the same as FIG. 1, but the alignment film is omitted.

A voltage is applied between the transparent electrode 2 on the upper substrate and the signal line 8 and between the transparent electrode 11 on the intermediate substrate and the strip-shaped transparent electrodes 14a, 14b on the lower substrate. ing. Further, by the switch circuit 34,
It is possible to control “ON” and “OFF” of application.

The twisted nematic liquid crystal 18 on the display panel side is designed so that the liquid crystal molecule alignment between the upper transparent substrate 1 and the intermediate transparent substrate 6 is 90 ° twisted and transparent when no electric field is applied. Therefore, the backlight 17
When the light is incident on the lower surface deflection plate 16, the transmitted light emerges as polarized light orthogonal to the incident light. Then, by arranging the upper deflection plate 20 so as to have a deflection surface in the same direction as the lower deflection plate 16, the backlight 1
The light of 7 is blocked. On the other hand, when an electric field is applied, the twisted nematic liquid crystal 18 is unaligned and the deflected light is transmitted as it is, so that the transmitted color of the color filter 4 is emitted.

On the other hand, since the guest-host liquid crystal 19 on the backlight control panel side uses a nematic type negative display color liquid crystal, a deflector is not required on the side of the intermediate transparent substrate 6 and a high contrast can be obtained. This liquid crystal is a nematic liquid crystal to which, for example, an anthraquinone-based black dye having a high light-shielding property is added as a dichroic dye. The display in this case is such that the nematic liquid crystal and the dichroic dye are aligned horizontally with respect to the substrate surface when no electric field is applied, and even if only one deflection plate is used, almost no light is transmitted by the added dye, and no electric field is applied. Sometimes, like the normal twisted nematic display, liquid crystal molecules and dye molecules are aligned perpendicular to the substrate, and light is transmitted,
Display is made.

Here, as shown in FIG. 2, the signal line 8 is selected, and the switching circuit 3 of the scanning line 14a is further selected.
When 4 is closed, the light from the backlight 17 passes through the guest-host liquid crystal 19 and enters the photoconductive film 10, whereby the potential of the signal line 8 is transmitted to the pixel electrode 14a. Then, the twist of the twisted nematic liquid crystal 28 is released, and the backlight light is transmitted through the color filter 4 to be displayed.

Next, the configuration of another embodiment of the present invention is shown in FIG. 3 and described below. In this embodiment, the backlight control panel is arranged on the side surface of the display panel. A light guide plate 37 is formed on the transparent substrate 36 of the liquid crystal panel on the display side, and signal lines 38 on the input side for liquid crystal display are arranged in the horizontal direction on the light guide plate 37 at predetermined equal intervals. A pixel electrode 39 is formed between the signal lines 38. A photoconductive film 40 for electrically connecting the signal line 38 and the pixel electrode 39, respectively.
Are formed. On the side surface of this display panel, a transparent substrate 45, a transparent electrode 44, a liquid crystal material 43, a transparent electrode 42,
A backlight control panel 30 is formed in which a transparent substrate 41 of a liquid crystal panel on the scanning line side is sequentially formed. Further, on the back side of the transparent substrate 36 of the liquid crystal panel on the display side,
A backlight 48 is installed, and reflection mirrors 46 and 47 are installed on the optical axis of the transparent electrode 42 so that the light of the backlight 48 is guided to the light guide plate 37 as scanning line light. Forms a strip-shaped transparent electrode along a predetermined direction so that the light from the backlight 48 serves as a scanning line. The other display panel facing the display panel has the same configuration as that of the previous embodiment and is omitted in FIG. 3, and in the illustrated display panel and the liquid crystal panel on its side, a deflector plate is used. The alignment film is omitted in the drawing.

Next, the operation of another embodiment having the above construction will be described. The light emitted from the backlight 48 is partially reflected by the reflection mirrors 46 and 47, and the backlight control panel 3
By the control of 0 (the drive control unit is not shown), the scanning line light is guided to the light guide plate 37 on the display panel side. In the light guide plate 37, light is refracted and reaches the photoconductive film 40, so that the signal line 38 and the pixel electrode 39 are electrically connected. Further, a light-shielding plate is provided below the photoconductive film 40 so that the light from the backlight 48 does not directly impinge on it. As a result, the potential of the signal line 38 is transmitted to the pixel electrode 39. After this, as in the above-described embodiment of the present invention, the twist of the twisted nematic liquid crystal (not shown) is released, and the backlight light is transmitted through the color filter (not shown) for display. In this example, twisted nematic liquid crystal is used as the liquid crystal.

[0021]

As described above, according to the liquid crystal display device of the present invention, the transparent electrodes on the back surface side of the first liquid crystal cell are picture element electrodes arranged in a matrix, and the picture element electrodes. The signal lines arranged in parallel with each other and extending in parallel to each other in a predetermined direction, the pixel electrodes and the signal lines are connected by a photoconductive element, and in the vicinity except the display surface side of the liquid crystal display panel, A liquid crystal layer is sandwiched between transparent electrodes, and an illumination light source control panel including at least a transparent substrate provided on the back surface is disposed, and the transparent electrode on the back surface side of the illumination light source control panel is composed of a plurality of electrodes. And each of the pixel electrodes is formed in a strip shape having a width equal to the dimension in the extending direction of the signal line and arranged in the extending direction of the signal line, and the light of the illumination light source is transmitted to the photoconductive element. Selective configuration In the light from the light source is incident on the photoconductive elements become scan line, the potential corresponding to the signal information of the scanning line is applied to the pixel electrode, it is possible to a predetermined display. Therefore, as in the case of a large-sized liquid crystal display panel, there is too much time division as in the conventional case, and it is not necessary to form a large number of TFTs.
It is possible to increase the contrast of the display surface and realize high-quality display. In addition, since only one signal line is provided on one panel and the connection between the signal line and the pixel electrode is a photoconductive element that is easier to manufacture than the conventionally used TFT, The complexity can be eliminated and the yield of non-defective products can be dramatically increased at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is another embodiment of the present invention.

FIG. 4 is a perspective view showing a structure of a conventional example.

FIG. 5 is a perspective view showing the structure of another conventional example.

[Explanation of symbols]

 1 ... ・ Top transparent substrate 2, 11 ・ ・ ・ ・ Transparent electrode 6 ・ ・ ・ ・ Intermediate transparent substrate 8 ・ ・ ・ ・ Signal line 9 ・ ・ ・ ・ Pixel electrode 10 ・ ・ ・ ・ ・ ・ Photoconductive film 11・ ・ ・ Control unit 13 ・ ・ ・ ・ Lower surface transparent substrate 14 ・ ・ ・ Strip transparent electrode 17 ・ ・ ・ ・ Backlight 18 ・ ・ ・ ・ Twisted nematic liquid crystal 19 ・ ・ ・ ・ ・ ・ Guest host liquid crystal

Claims (1)

[Claims] 1. A liquid crystal display panel comprising a first liquid crystal cell in which a liquid crystal layer is sandwiched between transparent electrodes, and transparent substrates formed on the display surface and the back surface of the first liquid crystal cell, respectively. In a liquid crystal display device comprising a light source arranged behind the liquid crystal display panel and a control unit for driving and controlling the liquid crystal display panel to modulate the intensity of light from the light source, the liquid crystal display device is formed on the back side. The transparent electrodes on the transparent substrate are composed of picture element electrodes arranged in a matrix, and signal lines arranged between the picture element electrodes and extending parallel to each other in a predetermined direction. The line is connected by a photoconductive element, and a second liquid crystal cell in which a liquid crystal layer is sandwiched between transparent electrodes is provided in the vicinity of the display panel except the display surface side of the liquid crystal display panel. 2nd liquid crystal cell An illumination light source control panel provided with a transparent substrate provided at least on the back surface is disposed, and the transparent electrode on the back surface side of the illumination light source control panel is composed of a plurality of signals, and each of the signal of the pixel electrode is In order to guide the light of the illumination light source to the photoconductive element while being formed in a strip shape having a width equal to the dimension in the line extending direction and arranged in the signal line extending direction. A liquid crystal display device, further comprising: a second control unit for driving and controlling the illumination light source control panel.