JPH03113427A - Simple matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain picture element information having a high contrast by constituting the device so that plural liquid crystal panels of the same structure are laminated, and these plural liquid crystal panels can be driven simultaneously by projecting parallel rays from the back. CONSTITUTION:The device is constituted so that plural liquid crystal panels A, B of the same structure are laminated, and can be driven simultaneously by projecting parallel rays 26 from the back. When the contrast obtained by each one liquid crystal of them is denoted as N : 1, the contrast of a total of picture element information which transmits successively through plural (n pieces of) liquid crystal panels and displayed in the end becomes N<n> : 1, and the contrast increases. In such a way, a plane display device having high contrast and high resolution is obtained, and for instance, a simple matrix type liquid crystal display device for reproducing a high vision image can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simple matrix liquid crystal display device used as a flat display device.

[Summary of the invention]

The present invention provides a simple matrix type liquid crystal display device including:
A plurality of liquid crystal panels having the same structure are stacked and parallel light is projected from the back to drive the plurality of liquid crystal panels simultaneously, thereby achieving high contrast of pixel information. .

[Conventional technology]

2. Description of the Related Art Conventionally, a simple matrix type liquid crystal panel, for example, a simple matrix type liquid crystal panel using a TN (twisted nematic) type liquid crystal, is known as a liquid crystal panel applied to a flat display device. FIGS. 10 and 11 are configuration diagrams of a general simple matrix type liquid crystal panel (1). This simple matrix type liquid crystal panel (1) has a plurality of strip-shaped scanning electrodes (40 (4,
) to (45)...] are arranged in parallel,
On the inner surface of the rear glass substrate (3) facing this, there are a plurality of strip-shaped picture element electrodes (5) (
(51) to (54)...] are arranged in parallel, and an insulating film (6) is formed between both glass substrates (2) and (3).
A liquid crystal layer (7) is disposed therebetween.

(8) is the front glass substrate (2) and the rear glass substrate (3).
) The spacers (9) and (10) arranged between the two are polarizing plates, respectively. Then, a bank light (11) is arranged on the rear glass substrate (3) side to form a transmissive liquid crystal panel.
be done.

This liquid crystal panel (1) has picture element electrodes (5) and scanning electrodes (
The intersection (12) of 4) is configured as a picture element, and when an image signal is applied to the picture element electrode (5) and a selection signal is applied to the scanning electrode (4), both electrodes (5) and ( An image is displayed when the liquid crystal in the portion corresponding to the intersection point (12) of 4) causes an electro-optical effect and its optical properties change.

[Problem to be solved by the invention]

By the way, the biggest problem with the simple matrix type liquid crystal panel (1) using TN type liquid crystal is that the contrast is low. That is, when forming a high-resolution simple matrix liquid crystal panel, if the number of scanning electrodes (4) is increased in order to increase the resolution in the vertical direction (or Y-axis direction),
The contrast of the liquid crystal panel decreases depending on the driving conditions.

In view of the above points, the present invention provides a simple matrix type liquid crystal display device with high contrast.

[Means to solve the problem]

In the simple matrix liquid crystal display device of the present invention, a liquid crystal layer (29) is disposed between a scanning electrode (SEA, 5EB) and a picture element electrode (PEA, PEB), and each intersection of both electrodes is configured as a picture element. A plurality of liquid crystal panels (A) and (
B) are stacked, and a plurality of liquid crystal panels (A) and (B) are simultaneously driven by projecting parallel light rays from the back side.

[Effect]

In a simple matrix type liquid crystal panel (for example, when using a TN type liquid crystal), the direction of optical rotation of the incident light beam is regulated by a polarizing plate, and when the liquid crystal is off, the light rotates 90 degrees, and when the liquid crystal is on, there is no optical rotation. , exhibits a high contrast ratio, but in reality, as the number of scanning electrodes (SEA, 5EB) increases, the effective optical rotation becomes less than 90 degrees (e.g., 75 degrees) in the liquid crystal off state, and more than 0 degrees (e.g., in the liquid crystal on state). 15
degree), and the contrast ratio decreases.

In contrast, in the configuration of the present invention described above, a plurality of liquid crystal panels (A) and (B) having the same structure are stacked and are configured to be driven simultaneously by projecting parallel light from the back. Assuming that the contrast obtained with the liquid crystal panel is N:1,
The total contrast of the picture element information that is sequentially transmitted through a plurality of (n) liquid crystal panels and finally displayed is N':1, and the contrast increases.

Therefore, a simple matrix liquid crystal display device with high resolution can be operated with high contrast.

〔Example〕

Hereinafter, an example of a simple matrix type liquid crystal display device according to the present invention will be explained with reference to the drawings.

In this example, as shown in FIGS. 1 to 3, the first
A simple matrix type liquid crystal panel body (called a liquid crystal panel body in the sense of a composite of liquid crystal panels) consisting of a liquid crystal panel A and a second liquid crystal panel B stacked on top of each other (21)
will be established. A first polarizing plate (
22), a second polarizing plate (23) is placed between the first liquid crystal panel A and the second liquid crystal panel B, and a third polarizing plate (23) is placed on the bottom surface of the second liquid crystal panel B. Place (24). Here, the first polarizing plate (22) and the second polarizing plate (
23) is a polarizing plate for liquid crystal panel A, and the second polarizing plate (23) and third polarizing plate (24) are for liquid crystal panel B.
It becomes a polarizing plate for. In other words, the second polarizing plate (23)
is shared by two liquid crystal panels A and B. A light regulating plate (25) is arranged below the third polarizing plate (24) to effectively convert the diffused light of the backlight (26) into parallel light beams.
liquid crystal panel B and the first liquid crystal panel A. A diffuser plate (27) serving as a screen is arranged above the first polarizing plate (22).

As shown in FIG. 4, the first liquid crystal panel A and the second liquid crystal panel B are constructed as simple matrix liquid crystal panels having the same structure. That is, the first liquid crystal panel A has 64 panels arranged in parallel in the X direction on the inner surface of the rear glass substrate (31).
0 (320×3 for color display) strip-shaped picture element electrodes (PEA) ((PE8-1) to (PEA-64)
0) ) is formed, and the front glass large substrate (3
2) 480 strip-shaped scanning electrodes (SEA) arranged in parallel in the Y direction on the inner surface ((SEA-1) ~ (SEA −
480)) are formed, and these front glass groups +yi,
(32) and the rear glass substrate (31) with an insulating film (not shown) interposed therebetween, and a liquid crystal layer, for example, a TN type liquid crystal layer (29).
(See Figure 1) are arranged.

Similarly to the first liquid crystal panel A, the second liquid crystal panel B also has
On the inner surface of the rear glass substrate (33), 640 (320 x 3 in case of color display) band-shaped picture element electrodes (PEB) ((FEB-1) to (FEB -) are arranged in parallel in the X direction.
640) ) are formed, and 480 strip-shaped scanning electrodes (
SEB) [(SEB-1) ~ (SEB -480)
) is formed, and a liquid crystal layer such as a TN type liquid crystal layer (29) (see FIG. 1) is arranged between the front glass substrate (34) and the rear glass substrate (33) with an insulating film (not shown) interposed therebetween. It consists of being done.

Each front glass substrate (32) (34) and rear glass substrate (31) (33) are formed of transparent glass plates, and each scanning electrode (SEA) (SEB) and each pixel electrode (PEA) are formed of transparent glass plates.
) (FEB) is formed of a transparent electrode. Here, the first
In the liquid crystal panel A and the second liquid crystal panel B, each intersection of the scanning electrode and the picture element electrode is configured as a picture element. Therefore, when the liquid crystal panel A and the liquid crystal panel B are stacked, they have the same structure, so they cannot be mutually separated. The picture elements begin to overlap.

In addition, in this example, first and third polarizing plates (22) and (24) are arranged on the upper surface of liquid crystal panel A and the lower surface of liquid crystal panel B.
The polarization direction of the second polarizing plate (23) placed between the first and second liquid crystal panels A and B is the same as that of the first and third polarizing plates (22) and (24). When the scanning electrodes (SEA) (SEB) are driven to non-display, the picture element corresponding to the scanning electrode becomes transparent (bright), and when the scanning electrode (SEA) (SEB) is driven to display, the picture element corresponding to the scanning electrode (SEA) (SEB) becomes transparent (bright). The picture element corresponding to the scanning electrode is configured to be opaque (dark).

The light regulating plate (25) can be constructed by laminating and bonding a large number of light-transmitting columns (25a) made of, for example, acrylic resin with a light-shielding (light-absorbing) adhesive. However, the light transmitting column (2
When 5a) is a hollow body, the portion that contacts the adhesive layer becomes a light absorption wall.

The diffuser plate (screen) (27) is designed to form an image of the pixel information that has passed through the pixel sections of LCD panels A and B, and to prevent the pixel information from being viewed at different positions due to so-called parallax. The pixel information is viewed at a viewing angle of .

Next, the operation of the simple matrix type liquid crystal display device (36) having the above-described configuration will be explained with reference to FIGS. 3 and 5. In this device, the scan electrodes are driven in parallel, that is, the scan electrode (SEA) to the liquid crystal panel and the scan electrode (SEB) of the liquid crystal panel B are simultaneously driven to display pixel information. For example, the scanning electrode (SEA-10) and picture element electrode (PEA-1) of liquid crystal panel A.
(PEA-640), scanning electrode (SIEB-1) and picture element electrode (PH8-1) of liquid crystal panel B
(PH8-640) are simultaneously driven (display driven), this causes each of the selected scanning electrodes (SE8-10) and (SEB-
10) and picture element electrode PE8-(1-640), FEB
The target picture element information is displayed at the intersection of -(1 to 640). The pixel information generated by this drive is opaque (dark).

Then, the scanning electrode (SEA-10), (SEB
-10) is selected, other scanning electrodes (SEA) (SEB) and picture element electrodes (PEA) (FEB) are selected.
) is a non-display drive, and the picture element portion corresponding to the scanning electrode becomes transparent (bright). Such information is obtained from the above-mentioned scanning electrodes (SEA, 5EB) and picture element electrodes (PEA, FEB).
is displayed by being driven repeatedly (cumulative driving method).

However, the liquid crystal panel No. 1 has contrast (bright areas:
Dark areas) are displayed at a ratio of N:1, but a liquid crystal panel body made by stacking multiple (n) liquid crystal panels has a contrast of N':
It becomes 1. In this device (36), the liquid crystal panel body (21) is constructed by stacking two liquid crystal panels A and B, so the contrast is N2:1.

That is, as shown in FIG.
The light beam (38) whose optical rotation direction is regulated by the polarizing plate (24) enters the liquid crystal panel B, and when the liquid crystal is off, the light beam (38) is rotated by 90 degrees, and when the liquid crystal is on, there is no optical rotation (0 degrees), resulting in a high contrast. However, in reality, if a simple matrix structure has a large number of scanning electrodes (for example, 480), the effective optical rotation will be less than 90 degrees (for example, 75 degrees) when the liquid crystal is off, and less than 90 degrees (for example, 75 degrees) when the liquid crystal is on. is 0 degrees or more (for example, 15 degrees) and is transmitted through the second polarizing plate (23). As a result, 0.966 of the incident light is transmitted when the liquid crystal panel B is in the off state, and 0.259 of the incident light is transmitted when the liquid crystal panel B is in the on state.

Therefore, the contrast ratio in that case is CR=0.966
10.259=3.73. This contrasting light beam is incident on liquid crystal panel A and a second polarizing plate (this polarizing plate is shared by two liquid crystal panels A and B), which are driven in a completely similar manner to liquid crystal panel B. In this liquid crystal panel A, optical rotation of 75 degrees occurs again when the liquid crystal is off, and optical rotation of 15 degrees occurs when the liquid crystal is on.
The light passes through the polarizing plate (22).

That is, here too, 0.966 of the incident light is transmitted when the liquid crystal is off, and 0.259 of the incident light is transmitted when the liquid crystal is on. As a result, the total contrast ratio of LCD panel B and LCD panel A is CR=(0,9661
0,259) 2-(3,73)'' = 13.9, and the contrast of pixel information is improved compared to the case of a single liquid crystal panel.In addition, in Fig. 5, the arrow (40)
indicates the polarization direction of the polarizing plate, and the length of the arrow (41) indicates the amount of transmitted light. In Figure 3, the transmitted light ray (38)
This shows the decrease in the number of lines, indicating the state of the contrast of the picture element information that is finally displayed in a diffused manner.

According to the above-mentioned simple matrix type liquid crystal display device (36), by stacking a plurality of liquid crystal panels A and B having the same structure and simultaneously driving the plurality of liquid crystal panels A and B by projecting parallel light rays from the back side. , the liquid crystal panel body (21) with high resolution can be operated with high contrast. This is advantageous when manufacturing a liquid crystal panel for reproducing high-definition video.

On the other hand, in the above-mentioned liquid crystal panel body, light beams, that is, hassycrite, are projected in an overlapping manner onto the corresponding pixel portions (portions where scanning electrodes and pixel electrodes overlap) of a plurality of spaced apart liquid crystal panels, and their shadows prevent crosstalk. It must be projected onto the diffuser plate (27), which is a screen, without causing any interference. For this purpose, the light beam from the backlight is projected as an effective parallel light beam by the light regulating plate (25) as described above. Therefore, the light regulating plate that effectively converts the backlight into parallel light is not limited to the light regulating plate (25) shown in the embodiment. However, when this light regulating plate (25) is used, its overall thickness can be made thinner, and its characteristics as a flat display can be more fully exhibited.

By the way, for example, the simple matrix type liquid crystal display device according to the present invention is set as follows.

Display area: 768mm x 576mm pixels
: 640 x 480 pieces (pixel size 1.2 mm x 1, 2 mm) Configuration (see schematic diagram in Figure 6): 2 matrix type liquid crystal panels, top liquid crystal panel A 3 mm thick, bottom liquid crystal panel B front side Glass thickness 1mm: Diffusion plate (27) (thickness 1mm) = 0.2mm guard hand (71) around 1 pixel
(Therefore, the effective pixel aperture area is 0.8m)
mX 0.8mm).

With this setting, the maximum allowable displacement angle (see Figure 7) is the maximum allowable displacement angle so that the pixel information on the lower LCD panel B does not overlap with the pixel information on the LCD panel A, causing crosstalk. θ-0.2mm/3mm=3.8 degrees.

By the way, for example, a 2 mm square piece of acrylic resin as shown in Figure 2 has a boundary (joint surface) that is light-shielding (light-absorbing).
In the case of a light regulating plate (25) that is laminated with adhesive (ignoring the thickness of the adhesive), that is, in the case of a light-transmitting column (25a) (ignoring the diagonal distance of the prism), The thickness in the direction perpendicular to the liquid crystal panel is 30 mm. Even taking into consideration the diagonal distance of the prismatic body (25a) described above, the positional deviation of the guard band with respect to the transparent display electrode, the relative positional deviation of the two liquid crystal panels A and B, etc., the distance is, for example, 35 to 50 mm. The thickness is . In addition, this light regulating plate (25
) so that the parallel light is averaged and projected onto the liquid crystal panel.
It is arranged somewhat apart from the liquid crystal panel B on the lower surface.

FIG. 7 shows an enlarged view of the light regulating plate (25), in which a plurality of prismatic bodies (25a) serving as light guides are bonded with light-shielding adhesive (43).
The light regulating plate (25) is laminated with transparent spacers (4).
4) through the liquid crystal panel B2, and therefore the third polarizing plate (2).
4). A backlight diffusion plate (45) is adhered to the lower surface of the light regulating plate (25). The backlight diffused light (46) enters the prismatic body (25a) of the light regulating plate, becomes an averaged parallel light beam (38), and enters the liquid crystal panel.

By the way, the backlight that forms the light beam that enters the light regulating plate (25) is required to have the following functions. The current goal of backlighting is how to make the luminance distribution uniform within the plane. The above-mentioned backlight is required to have its directional characteristics as sharp as possible in the normal direction of the backlight diffusion plate (45). FIG. 9 shows an example of this, in which a plurality of truncated square pyramids (53) having reflective surfaces (52) are arranged above a light source (51) at a predetermined pitch, and between adjacent truncated square pyramids (53). A reflective array (55) formed with a transparent portion (54) is disposed, and a backlight diffusion plate (45) made of, for example, frosted glass or opalescent glass is disposed on the upper surface of the reflective array (55).
At the same time, a reflector (56) is placed on the bottom surface of the light source (51).
A bank light (26) is constructed by arranging the following. According to this backlight (25), a sharp directional characteristic (57) in the normal direction of the backlight plate (45) can be obtained as a directional characteristic of the light source.

A light regulating plate (
25) has poor light utilization efficiency. FIG. 8 shows an example of a highly efficient light regulating plate. For example, 640mm x 480mm
16x12=129 light source blocks (61) with -side 40 mm are arranged on the screen (display area), and each light source block (61) ((61,), (61□)...
...] is projected by the Fresnel lens (62) at a maximum aperture angle α=3.8 degrees. In order to prevent uneven brightness from occurring in the projected image of the liquid crystal panel displayed on a screen (not shown), liquid crystal panels B are placed at a distance of 7.5 times the diameter of the light source block (61), and placed next to each other. The projection lights (63) from the light source blocks (61) are made to overlap. The illustration shows that the projection area (63,) of the light source block (61,) and the projection area (63□) of the light source block (61□) overlap. If the diameter of the light source block is D=40 mm, the total length will be about 400 mm.

Although the above explanation uses a liquid crystal material (TN liquid crystal material) that rotates light by 90 degrees, it is also possible to use a guest-host type liquid crystal panel or OMI (optical mode
It is easily understood that the present invention can also be implemented in a liquid crystal panel of the interference (normally 240 degree optical rotation) type.

(Effects of the Invention) According to the simple matrix type liquid crystal display device of the present invention, a plurality of liquid crystal panels having the same structure are stacked, and a plurality of liquid crystal panels can be driven simultaneously by projecting parallel light rays from the back side. Therefore, the contrast of the liquid crystal display device can be increased.

Therefore, it is possible to provide a flat display device with high contrast and high resolution, and for example, it is possible to manufacture a simple matrix type liquid crystal display device for reproducing high-definition video.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a simple matrix type liquid crystal display device according to the present invention, FIG. 2 is a perspective view thereof, FIG. 3 is an enlarged sectional view of the main parts thereof, and FIG. 4 is a liquid crystal panel A and B. FIG. 5 is an explanatory diagram of the operation according to the present invention, and FIG. 6 is a schematic diagram of the main parts for explaining the simple matrix type liquid crystal display device of the present invention. 7 is a configuration diagram of a main part showing an example of a light regulating plate according to the present invention, FIG. 8 is a diagram showing a main part of another example of a light regulating plate according to the present invention, and FIG. FIGS. 10 and 11 are a block diagram showing an example of a backlight according to the invention, and are a cross-sectional view of a conventional simple matrix liquid crystal panel and a plan view showing the structure of its scan electrodes and picture element electrodes. (A) and (B) are liquid crystal panels, (21) is a liquid crystal panel body, (22), (23), and (24) are polarizing plates, (25) is a light regulating plate, and (27) is a diffuser plate that becomes a screen. J6 Hayamatoso・Y2S″2 crystal thorns device A, B・
・-5&5-Bakasashi 21---; rlJllllI Hall'ni 22.2j, 2
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Claims (1)

[Claims of Claims] A plurality of liquid crystal panels having the same structure are stacked, in which a liquid crystal layer is disposed between a scanning electrode and a picture element electrode, and each intersection of these two electrodes is constituted as a picture element, and parallel light rays are projected from the back side. A simple matrix type liquid crystal display device which simultaneously drives the plurality of liquid crystal panels described above.