JPH0573006A - Driving system for color display device - Google Patents

Abstract

PURPOSE:To obtain a driving system for a color liquid crystal display device where a moving phenomenon is substantially restrained. CONSTITUTION:As to multi-level display by FRC, the thinning pattern of every frame is set for the respective picture elements of three primary colors arranged on a display panel so as to be made mutually different. Since bright lines linking between lighting picture elements are mutually different in every color and every frame, a specified pattern by the bright lines is not recognized, thereby substantially preventing the moving phenomenon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving system for a color display device, and more particularly to a technique effectively applied to a driving system for a color liquid crystal display device for displaying a color gradation.

[0002]

2. Description of the Related Art As one of gradation display technologies using liquid crystal,
There is FRC (Frame Rate Control). This technique is to perform gradation display by controlling display data between frames to change the effective value of the liquid crystal drive voltage. Regarding this FRC, for example, 199
Published in 1 year, "Flat Panel Display '91", pages 173 to 180, edited by Nikkei Electronics and Nikkei Microdevices.

[0003]

[Problems to be Solved by the Invention] With regard to FRC, as pointed out in the same document, when viewed on a large screen,
The line (bright line) connecting the lit pixels moves for each frame. This movement of the bright line is called moving. The speed of this moving phenomenon is proportional to the frame frequency, and this moving phenomenon is conspicuous at a practical frame frequency of 60 Hz to 70 Hz, which greatly hinders the practical use of multi-gradation display by FRC. The purpose of this invention is
An object of the present invention is to provide a driving method of a color liquid crystal display device in which the moving phenomenon is substantially suppressed. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0004]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows. That is, in the multi-gradation display by FRC, the thinning pattern for each frame is set to be different for each pixel of the three primary colors of color arranged on the display panel.

[0005]

According to the above-mentioned means, since the bright line connecting the lit pixels is different for each color and each frame, a specific pattern due to the bright line is not recognized, so that the moving phenomenon can be substantially prevented.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a schematic block diagram of an embodiment of a color liquid crystal display device to which the present invention is applied. The signal line driving circuit has a function of driving m signal lines D1 to Dm composed of 1 to m. Although not particularly limited, when the number m of signal lines of the liquid crystal display panel LCD is large, m signal lines are divided and driven by a plurality of signal line drive circuits. Pixel data is serially taken in from the input terminal Din and is output in parallel. That is, the latch circuits FF1 to FFm are
It constitutes a shift register & latch having a serial / parallel conversion function. The data Din input to the shift register & latch is binary data. Therefore, as will be described later, the intermediate gradation data is processed by the thinning circuit for each frame and is input as data such as lighting / non-lighting.

The pixel data held in the latch circuits FF1 to FFm are transmitted in parallel to the level shifters LS1 to LSm. Level shifters LS1 to LSm
Forms a control signal for a switch MOSFET that selectively outputs the drive voltages V0 to V2 formed by a drive voltage generating circuit (not shown) in accordance with the input pixel data.

The latch circuits FF1 to FFm forming the above shift register & latch are not particularly limited,
Since it operates by receiving a power supply voltage of about 5V, it outputs a signal having a high level of about 5V and a low level of 0V. On the other hand, the drive voltages V0 and V2 supplied to the liquid crystal display panel are set to a relatively high level. Therefore, the level (5
V, 0V), it may not be possible to turn on or off the switch MOSFET, so the level shifters LS1 to LSm convert the level to a level suitable for it.

The switch MOSFETs Q1 to Q3 shown as a representative form a unit drive circuit corresponding to one signal line D1, and one of the drive voltages V0 to V2 formed as described above is used. One is selected and transmitted to the signal line D1. In order to drive the liquid crystal in an alternating current, it is necessary to invert the polarity with respect to the common electrode of the liquid crystal. Above voltage V0
V2 is a polarity control signal for AC drive signal M for AC drive. That is, V0 is a voltage of 0 V with respect to the common electrode and turns on the pixel. In other words, light is transmitted by setting the transmittance of the liquid crystal to 100%. V1 is a positive drive voltage, and the liquid crystal has a transmittance of 0 and is turned off. V2 is a negative drive voltage, and similarly to the above, the transmittance of the liquid crystal is set to 0, and the liquid crystal is turned off. That is, the drive voltages V0 to V2 input to the drive switch MOSFETs.
Is output through the selector SEL. Selector SE
For L, the drive voltage V1 or V2 is switched by the AC signal M.

In the figure, one scanning line drive circuit GDV is arranged on the left side of the liquid crystal display panel LCD.
The scanning line driving circuit GDV sequentially selects scanning lines extending in the horizontal direction of the liquid crystal display panel LCD. In the liquid crystal display panel having the active matrix structure, the TFT transistor is selected by the scanning line. As a result, the driving voltages transmitted in parallel from the signal lines D1 to Dm are written in the liquid crystal pixels corresponding to the selected scanning line. The liquid crystal pixel acts equivalently as a capacitor and holds the written drive voltage until the next drive voltage is written.

FIG. 1 is an enlarged view of an embodiment of a color display screen for explaining the driving system according to the present invention. The figure shows an example of lighting (white circles) / non-lighting (black circles) in the first frame. In this example, 3 × 3
If one pixel is smaller than the resolution of the human eye, for example, if one pixel is smaller than the resolution of the human eye, then 3/9 = 1/3 gradation display is seen by the human eye. Then, the position of the lit pixel is moved every three frames to eliminate the flicker phenomenon.

The above-mentioned 1/3 gradation is for one color, and on an actual color display panel, as shown in FIG. 1, a color filter formed by repeating a pattern of RGB, RGB ... It is formed in a stripe shape. Therefore, one set of color three primary color pixels is composed of 3 × 3 × 3 = 27 pixels arranged in 3 rows and 3 columns as shown by the dotted line in the figure when the RGB column is counted as one column.

At the bottom of the figure, there is shown a lighting / non-lighting display pattern for each color. In one frame, as in the lighting / non-lighting example of the display panel shown on the upper side, with respect to the R (red) pixel, the pixel in the first row and the first column is lit, the pixel in the second row and the second column is not lit, 1 The third row and third column are not lit, the second row and first column pixels are not lit, the second row and second column pixels are lit,
2nd row and 3rd column is not lit, 3rd row and 1st column is not lit, 3rd row and 2nd
The pixels in the columns are not lit, and the third row and third column are lit. Therefore, when these are put together, the lit pixels are arranged from the upper left to the lower right. Regarding the G (green) pixel, the pixel in the first row and the first column is not lit, the pixel in the first row and the second column is lit, the first row and the third column is not lit, the pixel in the second row and the first column is lit, the second row and the second column Pixels are not illuminated,
2nd row and 3rd column is not lit, 3rd row and 1st column is not lit, 3rd row and 2nd
The pixels in the column are not lit, and the third row and third column are lit. Therefore, when these are put together, the lit pixels are arranged from the upper right to the lower left. Regarding the B (blue) pixel, the pixel in the first row and the first column is lit, the pixel in the first row and the second column is not lit, the pixel in the first row and the third column is lit, the pixel in the second row and first column is not lit, the second row and second column The pixels are lit up,
2nd row and 3rd column is not lit, 3rd row and 1st column is not lit, 3rd row and 2nd
The pixels in the columns are not lit, and the third row and third column are lit. Therefore, when these are put together, the lit pixels are arranged from the upper left to the lower right. However, on the color display screen, the lit pixels are dispersed so that a conspicuous bright line such as an oblique straight line does not occur.

In 2 frames, among 3 × 3 pixels in R, the first row is on the right, the second row is on the left, and the third row is on the center. Among the 3 × 3 pixels, the first row is the center, the second row is the left pixel, and the third row is the right pixel. In B, among the 3 × 3 pixels, First
Each pixel in the center of the row, the second row in the right, and the third row in the left lights up. Since this is similarly dispersed and displayed on the above color display panel, a conspicuous bright line such as an oblique straight line can be prevented from occurring.

In 3 frames, 3 in R
Of the 3 × 3 pixels, the first row is in the center, the second row is on the right, and the third row is on the left. In G, the first row of the 3 × 3 pixels is lit. Is on the left, the second row is on the right, and the third row is on the center of each pixel. In B, among the 3 × 3 pixels,
Each pixel in the first row is on the right, the second row is on the left, and the third row is on the center. Since this is similarly dispersed and displayed on the above color display panel, a conspicuous bright line such as an oblique straight line can be prevented from occurring. It should be noted that, in the case of 2/3 gradation, the number of lighting pixels is as large as 6 out of 3 × 3 pixels. Therefore, there is no problem because no noticeable line such as a bright line is generated.

In this embodiment, the lighting patterns of the three primary color pixels in the same frame are made different, and this is performed for each frame, so that the concentration of the lit parts or the non-lit parts on the entire screen is reduced. It is something to do. Accordingly, when the entire screen or a large display area is displayed in gray (gray) by the three primary colors, moving is less likely to occur, and the displayed characters and the like can be easily seen.

FIG. 2 is a block diagram of an embodiment showing the entire display device. The display system is a source of pixel data, and is composed of, for example, a display system controller such as CRTC or VGA and a frame memory in which color image data is written. When the data read from the frame memory has four levels of full lighting, 2/3 gradation, 1/3 gradation, and non-lighting as described above,
The data per pixel is composed of 2 bits. For example, 11 is all lit, 2/3 gradation is 10 and 1/3 gradation is 0.
1, all non-lighting is assigned as 00.

Pixel data from such a frame memory is repeatedly read in synchronization with the display operation of the display device. The thinning circuit unconditionally means 1 for lighting and 0 for non-lighting for all lighting and all non-lighting data.
It is converted to data and output. Data 1 showing halftone
For 0 or 01, the following thinning is performed. In other words, it is converted into data of 1 which means lighting and 0 which means non-lighting for each frame and outputs it.

In the thinning circuit, if the frame information is 1 and the gradation data is 1 gradation and the color information is R, 100 at the first scanning timing, 010 at the second scanning timing and 3rd at the time of one frame. 001 is formed at the scanning timing. Further, for the color information G, 001 is formed at the first scanning timing for one frame, 010 for the second scanning timing, and 100 at the third scanning timing, and 100 for the color information G at the first scanning of one frame. 100 is formed at the scanning timing, 101 is formed at the second scanning timing, and 001 is formed at the third scanning timing.

When the frame information changes like 2 or 3, the thinning-out circuit converts into 1-bit data for each pixel in accordance with lighting / non-lighting of 2 frames and 3 frames of FIG. Output. Therefore, the decimation circuit is 0
It can be configured by a decoder circuit (logic gate circuit) that receives halftone data such as 1 and 10 and frame information and color information. Alternatively, the RO having the above information as an address
It can be configured by a pattern generation circuit using M (read only memory).

The effects obtained from the above embodiment are as follows. That is, (1) in multi-gradation display by FRC, thinning patterns for each frame are set to be different from each other for each pixel of the three primary colors of color arranged on the display panel, so that the bright lines connecting the lit pixels are of different colors. Also, since each frame is different from each other, a specific bright line is not recognized on the display screen, so that the moving phenomenon can be substantially prevented. (2) According to the above (1), it is possible to obtain an effect that multicolor display is possible by using a color liquid crystal display panel with a simple configuration.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention of the present application is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the liquid crystal display panel may have a simple matrix structure. That is, in the FRC of this embodiment, halftone display is performed by thinning out pixel data for each frame. It suffices for the color display panel to be capable of binary display of bright and dark corresponding to the driving voltage. Therefore,
In addition to the liquid crystal, any type may be used as long as it can perform color display by the similar binary display. LCD drive voltage and lighting /
The non-lighting relationship may be such that the directions of the polarizing plates provided with the liquid crystal sandwiched therebetween are orthogonal to each other and the lighting is performed by applying a drive voltage. One pixel combination is
3 (R, G, B) x 2 (columns) x 2 (rows), with 3 frames having 3 gradations of full lighting, 1/2 gradation and non-lighting, and 3 (R, G, B) x 4 (row) x 4
As (row), all non-lighting by 4 frames, 1/4 gradation,
Various embodiments can be adopted such as 2/4 gradation, 3/4 gradation, and 5 gradations of all lighting. The present invention can be widely used as a driving system for color display devices.

[0023]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, in multi-gradation display by FRC, the thinning pattern for each frame is set to be different for each pixel of the three primary colors of color arranged on the display panel so that the bright line connecting the lit pixels is for each color and each frame. Since they are different from each other, a moving line can be substantially prevented because a specific bright line is not recognized on the display screen.

[Brief description of drawings]

FIG. 1 is a pattern diagram of a lighting example of a display panel and a lighting example of each color for each frame for explaining an embodiment of a driving system of a color display device according to the present invention.

FIG. 2 is an overall schematic block diagram of a display device to which a driving method of a color display device according to the present invention is applied.

FIG. 3 is a schematic block diagram showing an embodiment of a color liquid crystal display device used in the present invention.

[Explanation of symbols]

FF1 to FFm ... Shift register & latch, LS1 to L
Sm ... level shifter, SEL ... selector, Q1-Q3 ...
Switch MOSFET, LCD ... Liquid crystal display panel, GD
V ... Scan line drive circuit, G1 to G480 ... Scan line electrode, D
1 to Dm ... Signal line electrodes.

Claims (3)

[Claims] 1. An average luminance is obtained by thinning out data from pixels for which halftone display is to be performed over a plurality of frames using a color display panel in which pixels of three primary colors of color are regularly arranged. A driving method of a color display device, characterized in that, by performing an intermediate gradation by means, the thinning pattern for each frame is made different from each other in each pixel of the three primary colors of color arranged on the display panel. 2. The thinning-out of the data is to convert into binary pattern information corresponding to a scanning line of a display device by halftone data consisting of a plurality of bits, color information and frame information. A driving method of the color display device according to item 1. 3. The color display according to claim 1, wherein the display panel for the three primary colors of color is a color liquid crystal display device provided with a color filter in the form of vertical stripes corresponding to the signal line direction. Device drive system.