JPH0643455A - Liquid crystal projection device - Google Patents

Abstract

PURPOSE:To prevent the fall of the light from a light source on thin-film transistors (TFTs) and to prevent the deterioration in the characteristics thereof by coating the entire part of the TFTs with filters consisting of a light non- transparent member. CONSTITUTION:The TFTs and pixel electrodes 3 are formed on a relatively thick glass substrate 1 and an oriented liquid crystal 5 is sealed between a common electrode 4 over the entire surface on the inner side of a thin glass or transparent plastic substrate 2 and the pixel electrodes 3 are sealed. A transparent substrate 6 attached with the color filter layers 7, 8 is disposed in tight contact on the surface of the substrate 2; further, the entire part is held by upper and lower polarizing plates 9, 10. The color filter layer 7 is the filter to allow the passage of one among three primary colors; red, blue and green and the color filter layer 8 is a black filter which does not allow the passage of light. The filter layer 7 of the three primary colors and the black filter layer 8 form striped patterns extending in the horizontal direction of a display screen as if one of the three primary colors passes through a blind.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a thin film transistor (T
The present invention relates to a liquid crystal projection device using a liquid crystal light valve having an FT), and particularly to the arrangement of its filter.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Large projection televisions are usually enlarged and projected using a projection tube corresponding to the three primary colors. However,
The projection tube is expensive and it is difficult to increase the screen brightness.

The present invention has been made to solve such problems, and an object thereof is to provide a liquid crystal projection device capable of increasing the brightness on the screen.

[0004]

A liquid crystal projection device according to the present invention comprises a light source, a liquid crystal light valve for modulating light from the light source, and projection optical means for projecting light modulated by the liquid crystal light valve. . The liquid crystal light valve has a pair of substrates filled with liquid crystal, has a common electrode on one of the substrates, and has a pixel electrode arranged in a matrix on the other substrate and the vicinity of the pixel electrode. It is composed of an active matrix type liquid crystal panel each having thin film transistors arranged to drive the pixel electrodes. Further, a filter made of a light non-transmissive member is arranged between the thin film transistor and the light source so as to cover the entire thin film transistor.

[0005]

In the present invention, the light from the light source is modulated by the liquid crystal light valve, and the modulated light, that is, the image is projected and displayed on the screen by the projection optical means. The liquid crystal light valve is made of an active matrix type, and the above image becomes stable. Further, since the filter made of the light non-transmissive member covers the entire thin film transistor, and the light from the light source does not hit the thin film transistor, its characteristic deterioration can be prevented. Further, since the brightness of the light source can be made large without worrying about the characteristic deterioration of the thin film transistor, the brightness on the screen can be sufficiently increased.

[0006]

1 is an explanatory view of a liquid crystal display panel used in a liquid crystal projection apparatus according to an embodiment of the present invention.
The TFT and the pixel electrode 3 are formed on the relatively thick glass substrate 1, and the liquid crystal 5 oriented between the common electrode 4 and the pixel electrode 3 formed on the entire inner surface of the thin glass or transparent plastic substrate 2 is enclosed. ing. A transparent substrate 6 provided with color filter layers 7 and 8 is arranged on the substrate 2 in close contact with each other, and the whole is sandwiched by upper and lower polarizing plates 9 and 10.
Reference numeral 11 is a liquid crystal sealing portion. The color filter layer 7 is a filter that allows one of the three primary colors of red, blue, or green to pass therethrough, and the color filter layer 8 is a black filter that blocks light. The black filter is for blocking light,
It may be a metal vapor deposited. The filter layers 7 of the three primary colors and the black filter layer 8 form a striped pattern extending in the horizontal direction of the display screen, and just one of the three primary colors comes through the blinds. This relationship is as shown in FIG.

FIG. 2A shows a pattern of the color filter layer, where 12 is a portion which does not transmit light and 13 is one of the three primary colors.
It is a filter layer corresponding to one. The TFT 15 and the pixel electrode 14 are arranged under the color filter layer as shown in FIG. Reference numeral 16 is a TFT gate drive line, and 17 is a drain drive line. At this time,
The black filter portion 12 includes the entire TFT 15 and the pixel electrode 1.
4 halves, and as a result, as described below,
When this panel is irradiated with parallel rays from behind the filter, the TFT 15 itself does not receive light, so the TFT 15
It is possible to prevent the deterioration of characteristics. Further, for example, in order to display a red image signal, two panels with red and black filters are used to finally synthesize them on the screen to obtain a red picture. Accordingly, different display panels can be used in the first half and the second half of the interlace, which facilitates signal processing. Of course, 2
By shifting the panel display images by one horizontal line on the screen and overlapping them, a picture without stripes can be obtained over the entire screen. By doing so, one pixel on the screen corresponds to half of the pixel electrode of the panel, and the pixel electrode size can be made larger than in the case of forming double density pixels on one display panel, so that the image quality is improved. Is improved.

Pixel electrode 1 driven by TFT 15
In No. 4, by storing a signal potential in the electrode capacitance of the liquid crystal, the orientation of the liquid crystal can be stably maintained at a predetermined level even during the non-driving period. By the way, when the electrode capacitance of the liquid crystal is small, self-discharge is accelerated, and a stable alignment level cannot be maintained until the next drive signal arrives, resulting in deterioration of image quality. Further, when the TFT is exposed to light, the insulation performance of the TFT is deteriorated, the leak resistance is lowered, and the charge of the electrode capacitance of the liquid crystal is also quickly discharged, resulting in deterioration of image quality. However, in this embodiment, the TFT1
5 is not exposed to light, and the pixel electrode 14 is enlarged to form the entire screen with two panels for each of the three primary colors, so that a uniform and stable projection image can be obtained.

FIG. 3 is a conceptual diagram of a liquid crystal projection device using the active matrix type liquid crystal light valve of FIGS. 1 and 2, in which light from a white light source 20 is applied to two liquid crystal display panels 18 and 19 for each primary color. The light is irradiated through the parallel optical path system 22 and is focused on the screen 24 by the magnifying lens system 23. Reference numeral 21 is a reflecting mirror. As the magnifying projection optical system itself, the one used in the 35 mm slide projector can be used, but a fine adjustment mechanism for aligning a total of 6 magnified images on the screen is necessary.

FIG. 4 is a block diagram showing the structure of a TV signal processing circuit for each primary color. The video signals are separated by the interlace separation circuit 25, the signals for each interlace are passed through the delay circuit systems 26 and 27, and are combined by the signal combining circuits 28 and 29, and then the video signals are supplied to the liquid crystal display panels 30 and 31. To do. As a result, the signals in the interlace period on one side are supplied without interruption to one panel, and the image quality does not deteriorate even if the number of pixels is increased and the pixel capacity is reduced. In this case, the delay circuit system is A
It can be formed by a D conversion circuit, a frame memory, and a DA conversion circuit.

FIG. 5 is a conceptual view of the liquid crystal projection apparatus of the embodiment shown in FIG. 3 as viewed from above, and FIG. 6 is a housing 40 containing the embodiment shown in FIGS. 3 and 5. It is a perspective view showing a state. FIG. 3 is a conceptual diagram for one color, and a pair of liquid crystal display panels 1 for one color.
Although the state in which 8 and 19 are provided has been described, three colors (red, green and blue) are required for color display. When the projection device of the embodiment shown in FIG. 3 is viewed from above, as shown in FIG. 5, liquid crystal display panels 18, 18a, 18 are provided.
Since there are three b's, each of which is provided as a pair, it is composed of six liquid crystal display panels as shown in FIG. The images generated by the red, green, and blue liquid crystal display panels are superimposed on the screen 24. However, as described with reference to FIG. 3, the image formed by one liquid crystal display panel 18 of each color is The odd-numbered image of the horizontal line is set, and the image formed by the other liquid crystal display panel 19 is set as the even-numbered image of the horizontal line, which are displayed on the screen 24 in a staggered manner.

[0012]

As described above, according to the present invention, it is necessary to increase the resolution by increasing the number of pixels as much as possible because the projection television has a large screen. However, it is possible to sufficiently meet the demand. , The optical system has a simple structure, and the screen brightness can be increased more easily than the existing projection tube because only the light source needs to be brightened. Further, the filter made of a light non-transmissive member is arranged so as to cover the entire thin film transistor, and the light from the light source does not hit the thin film transistor, and its characteristic deterioration can be prevented. Further, since the brightness of the light source can be made large without worrying about the characteristic deterioration of the thin film transistor, the brightness on the screen can be sufficiently increased and a bright image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a liquid crystal display panel used in a liquid crystal projection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between a pixel electrode portion and a color filter portion.

FIG. 3 is a conceptual diagram of a liquid crystal projection device according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a TV signal processing circuit for each primary color.

5 is a conceptual view of the liquid crystal projection device of the embodiment of FIG. 3 as viewed from above.

6 is a perspective view showing a state in which the liquid crystal projection device of the embodiment of FIGS. 3 and 5 is housed in a housing.

[Explanation of symbols]

 1 Glass Substrate 2 Transparent Substrate 3 Pixel Electrode 4 Common Electrode 5 Liquid Crystal Layer 6 Filter Substrate 7 3 Color Filter Layer Corresponding to One of the Primary Colors 8 Light-Impermeable Filter Layer 9, 10 Polarizing Plate 11 Sealing Part 12 Light-Passing Black filter 13 Color filter corresponding to 3 primary colors 14 Pixel electrode 15 TFT 16 Drain drive line 17 Gate drive line 18, 19 Liquid crystal display panel 20 White light source 21 Reflector 22 Parallel light path system 23 Magnifying lens system 24 Screen 25 Interlace separation circuit 26, 27 Delay circuit system 28, 29 Signal combining circuit 30, 31 Liquid crystal display panel

Claims (1)

[Claims] 1. A light source, a liquid crystal light valve for modulating light from the light source, and projection optical means for projecting light modulated by the liquid crystal light valve, wherein the liquid crystal light valve includes a pair of substrates. Liquid crystal is sealed inside, and a common electrode is provided on one substrate of the substrates, and pixel electrodes are arranged on a matrix on the other substrate and are respectively arranged in the vicinity of the pixel electrodes to drive the pixel electrodes. It is composed of an active matrix type liquid crystal panel having a plurality of thin film transistors, and a filter made of a light non-transmissive member is arranged between the thin film transistors and the light source so as to cover the entire thin film transistors. Characteristic liquid crystal projection device.