JPH02230213A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To rewrite a screen in a short time which is enough to display a moving picture even if the number of scanning lines is large by dividing a scanning electrode group into blocks, driving liquid crystal light valves at every block and projecting images, and synthesizing the images on the screen to constitute one screen. CONSTITUTION:When the screen is displayed, the liquid crystal light valves 3 are driven individually, block by block, to project images, which are synthesized on the screen to constitute one screen. Therefore, the numbers of scanning lines by the light valves of the respective blocks are 1/(number of blocks) as large as the total number of scanning lines of a screen. Consequently, even when a rewriting time per scanning line is long, the time required to rewrite the entire image plane can be shortened, and a moving picture can be displayed sufficiently even when a ferroelectric liquid crystal element is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection type liquid crystal display device, and in particular to a projection type liquid crystal display device that allows screen rewriting in a short time sufficient for displaying moving images even when the number of scanning lines is large. This invention relates to a type of liquid crystal display device.

[Prior art and problems to be solved by the invention] In recent years,
Attempts have been made to realize a large-screen display using a projection type liquid crystal display device, but such a display has the advantage of being more compact than a CRT projection device by using a liquid crystal element.

The so-called active matrix type, in which a thin film transistor or the like is arranged for each pixel, is often used as a liquid crystal element, but active matrix type liquid crystal elements are relatively expensive due to the complicated manufacturing process, which increases the cost of the entire device. This is the main factor. On the other hand, TN (Twisted Nematic) type liquid crystals have a simple matrix structure and are inexpensive, but cannot be used in large-capacity displays because the contrast decreases as the number of pixels increases.

The same simple matrix type ferroelectric liquid crystal (FLC) element maintains constant contrast even when the number of pixels increases, so it can be used not only as a direct-view display but also as a projection display. However, in the case of an FLC element, the rewriting time for one screen is proportional to the number of scanning lines N, so in the case of N-5 1 2, for example, in order to display a moving image that requires rewriting more than 30 times per second, one scanning line is required. The allocated time per unit is 65 μs or less, and extremely high-speed switching is required.

This point is the reason why it is difficult to display moving images using the FLC device.

In view of the problems of the prior art, an object of the present invention is to
To enable a projection type liquid crystal display device to rewrite the screen in a short period of time sufficient for displaying a moving image even if the number of scanning lines is large.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a projection type matrix liquid crystal display equipped with a liquid crystal light valve having a liquid crystal and a scanning electrode group and a signal electrode group facing each other with the liquid crystal interposed therebetween. In the device, the scanning electrode group is divided into two or more blocks,
Each block is equipped with a scanning line drive circuit that drives the liquid crystal light valves separately, and the liquid crystal light valves of each block are driven separately, projected, and combined on the screen to form one screen. .

The video signal used as input is divided, for example, by a circuit that converts it into N parallel video signals in which the number of scanning lines is 1/N of the total (N≧2) and the screen scanning period is equal to that of the other video signals. This is used to drive the liquid crystal light valves for each block.

The liquid crystal light valves of each block may be driven by a common scanning line driving circuit by electrically connecting the corresponding scanning electrodes.

Furthermore, the scanning electrode group of each block is arranged so that the interval between the scanning lines is at least the width of one scanning line, and two or more liquid crystal light pulses for each block are projected onto the same screen and synthesized. The screen may also be configured.

[Function] In this configuration, the screen display is performed by driving the liquid crystal light valves of each block separately, projecting the images, and combining them on the screen to form one screen. Since the number of scanning lines is as small as 17 (the number of blocks), which is the total number of scanning lines in one screen, even if the number of scanning lines in one screen is large, moving images can be easily displayed at a refresh scanning frequency of 30 Hz or more. Therefore, the present invention is effective when using a liquid crystal element in which the screen scanning time is proportional to the number of scanning lines, especially when using a liquid crystal element with strong electromagnetic properties.However, as the number of scanning lines increases, the contrast decreases, It is also suitable for TN-type liquid crystal devices, which can provide sufficient contrast only in certain cases.

[Example] Hereinafter, an example of the present invention will be described using the drawings. FIG. 1 is a schematic diagram showing a liquid crystal display device according to an embodiment of the present invention, in which one screen is divided into three parts and three projection type FLC display devices (projection devices) are used to separate parts of the screen 4. It is projected and displayed on the screen. Each projection device has a light source 1,
It has a well-known configuration consisting of a lens 2 and a liquid crystal light valve 3. The liquid crystal light valve 3 has a matrix configuration of 160 scanning lines and 800 signal lines, and the liquid crystal material is CS1014.
(manufactured by Chisso Corporation). The switching speed of this liquid crystal at a driving voltage of 24μ is 20% per scanning line.
It is 0 μs. Therefore, the scanning time for one screen is 3 2
ms, adding the pause period of lms to 33ms,
30 repeated scans can be performed per second.

FIG. 2 is a block diagram of a circuit related to drive control of the device shown in FIG. 1, and FIG. 3 is a timing chart of each signal. In the figure, 21 is an input terminal for a video signal, 22 to 27 are image memories that store image data, 28 to 30 are display devices that display images based on this image data, and 39 is a signal electrode of the liquid crystal light valve 3. 31 is a write control unit that controls writing of image data to the image memories 22 to 27; 37 is the image memory 22;
This is a readout control section that controls the readout of image data from 27 to 27.

In this configuration, the video signal VIDEO sent from the outside via the human input terminal 21 is temporarily stored as image data in the image memories 22-27, and then sent to the display devices 28-30. However, image memory 22~
27 is an image memory 22, 23, 2 corresponding to each display device.
It is divided into three areas: 4 and 25, and 26 and 27.

Also, since the writing and reading cycles are different, each area has two
It has a page structure, and while the first page, that is, the image memories 22, 24, and 26 are being read, the second page, that is, the image memories 23, 25, and 27 are being written, and then the second page is written. The first page is written at the same time as it is read. That is, the write controller 31 sends control signals WEI, WE2, and WE3 for distributing write data to the three areas mentioned above, a signal ADR for specifying a write address, and a WPA for specifying a page.
Each GE signal is generated, and one screen worth of video signal is stored in the image memory of each first page accordingly. Then, the readout control unit 37 provides the readout clock RE and the page selection signal RPAGE to the image memories 22 to 27, and also provides the same clock RE to the signal electrode drive circuits 39 of the display units (display devices) 28 to 30 to display image information. Read and transfer.

When the transfer of information for one scanning line is completed in this way, the display clock DISP is sent to one of the liquid crystal light valves 3.
A scanning line is selected and the display content appears on the light pulp 3. Thereafter, each scanning line is sequentially selected in the same manner, and 16
After selecting 0 scanning lines, one screen is completed. The display sections of the three projection devices 28 to 30 are scanned in parallel, and the scanning period for one screen is made to coincide with the transfer period for one screen of the video signal. The video signal input as described above is divided into three parts and displayed on each liquid crystal light valve 3 with a delay of one screen.

FIG. 4 is a schematic diagram showing a liquid crystal display device according to another embodiment of the present invention. In this case as well, one screen is divided into three light valves of 50'N52, combined by a prism 53, and projected onto the screen 4.

In this example, the scanning lines are divided into three groups: 3nth line, 3n+1st line, and 3n+2th line (n=1.2"-160). The electrode configuration of each light valve is as shown in FIG. , 160 scanning lines (scanning electrodes) 1a to 160a are arranged with an interval of two lines, and 160 scanning lines (scanning electrodes) 1a to 160a are arranged with an interval of two lines.
800 pieces of 800b are arranged. When projecting this, the scanning lines are shifted one by one and aligned to form one continuous screen.

In this embodiment, three light valves 50 to 52 are arranged in one projection device 54, so the light source 1 and lens 2 are shared, resulting in a compact overall configuration. moreover,
Flexible cable 5 connects the scanning electrode group of each light valve.
5, one tree at a time is connected and driven by one scanning line drive circuit 56, so the scanning side drive circuit can be a station, reducing costs.

FIG. 6 is a block diagram showing peripheral circuits for driving the liquid crystal light valves 50-52 of FIG. 4. A video input signal input from the outside via the video input terminal 61 is divided by the demultiplexer 62 for each horizontal synchronization period,
The signal is sent to three signal line drive circuits 63. After three horizontal synchronization periods have elapsed and the image data has been sent to the three signal line drive circuits 63, the display clock D is given to both the signal line and scanning line drive circuits 63.85, and the display signal voltage pulse and the scanning line A selection signal voltage pulse is applied to each light valve 66 simultaneously. By repeating the above operations, all 160 scanning lines are selected and one screen is completed. The time required to complete one screen is 33 ms, the same as in the embodiment shown in FIG. 1, and therefore the screen is rewritten 30 times per second.

[Effects of the Invention] As explained above, according to the present invention, the liquid crystal light valve is divided into a plurality of blocks and driven for each block, so even if the rewriting time per scanning line is long, the entire screen can be The time required for rewriting can be shortened, and moving images can be displayed satisfactorily even when an FLC element is used. Further, even when using a TN type liquid crystal whose contrast decreases as the number of scanning lines increases, the contrast can be increased by increasing the rewriting time per scanning line.

[Brief explanation of the drawing]

1 is a schematic diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a circuit related to drive control of the device of FIG. 1, and FIG. 3 is a diagram of the circuit of FIG. 2. A timing chart of each signal, FIG. 4 is a schematic diagram of a liquid crystal display device according to another embodiment of the present invention, FIG. 5 is a configuration diagram of the electrodes of the light valve of the device in FIG. 4, and FIG. 5 is a block diagram showing a peripheral circuit for driving a light valve of the device of FIG. 4. FIG. 1: Light source, 2: Lens, 3, 50-52: Liquid crystal light valve, 4: Screen, 22-27: Image memory, 28
~30, 54: Display device (projection device), 31: Write control unit, 37: Read control unit, 39.63 Signal electrode drive circuit, 56, 65: Scanning line drive circuit, 62: Demultiplexer.

Claims (4)

[Claims] (1) In a projection type matrix liquid crystal display device equipped with a liquid crystal light valve having a liquid crystal and a scanning electrode group and a signal electrode group facing each other with the liquid crystal interposed therebetween, the scanning electrode group is divided into two or more blocks, and each It is characterized by having a scanning line driving circuit that drives the liquid crystal light valves for each block separately, and driving the liquid crystal light valves for each block separately, projecting the images, and combining them on the screen to form one screen. LCD display device. (2) The number of scanning lines for the video signal is 1/N of the total (N≧2)
2. The liquid crystal display device according to claim 1, further comprising a circuit for converting the video signals into N parallel video signals having a screen scanning period equal to that of the original video signal. (3) The liquid crystal display device according to claim 1, wherein the liquid crystal light valves of each block are electrically connected to corresponding scan electrodes and driven by a common scan line drive circuit. (4) The scanning electrode group of each block is arranged so that the interval between scanning lines is at least the width of one scanning line, and two or more liquid crystal light valves of each block are projected onto the same screen and synthesized. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device comprises one screen.