JPH07281154A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a liquid crystal display device that suppresses the occurrence of flicker when thinning pixels to perform multi-gradation display. [Structure] The signal side drive circuit 3 checks the current frame by a frame counter 11 and
Is used to check the current scanning line, and the dot counter 13 is used to check the current dot position. Then, for each line of each frame, the decoder 14 outputs a selection signal including whether or not the leading pixel of the line is turned on.
5, the selection signal from the decoder 14 to the selector 15 is delayed by one dot by the latches 18 and 19 and output to the selector 16 and the selector 17. Then, each selector selects the d0 terminal and the d1 terminal based on the selection signal, so that the selector 15 selects the R video data,
The selector 16 outputs the G video data and the selector 1
At 7, the B video data is thinned out and output as thinned video data R, G, and B, respectively.

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,
More specifically, the present invention relates to a liquid crystal display device that performs multi-gradation display.

[0002]

2. Description of the Related Art Recently, liquid crystal display devices perform not only binary display of white and black but also multi-gradation display for displaying an intermediate state between "white" and "black" with the spread of liquid crystal. This improves the sense of reality.

The number of gradations that divides this intermediate state into several levels is called the number of gradations, and the greater the number of gradations, the more various images can be represented.

For such multi-gradation display, conventionally, for example, when an STN (Super Twisted Nematic) type liquid crystal cell is used, when one video data is displayed with a plurality of frames as one cycle, the liquid crystal is displayed. A frame gradation method or the like is used in which gradation is expressed by changing the number of times of lighting.

The frame gradation method is also called a frame thinning method. For example, when expressing 8 gradations, the number of frames to be thinned out based on the gradation data of video data among the frames from "0 to 7". That is, the number of frames that are not turned on is set.

According to such a conventional frame gradation method,
For example, when color gradation display is performed in four gradations based on color image data, three frames from darker gradation 0 to brighter gradation 3 are displayed as one cycle. At 0, the pixel is not lit in any frame,
At the gradation 1, as shown in FIG. 7, all three pixels of R, G, and B that form one picture element are turned on in the first first frame. Then, in gradation 2, all three R, G, and B pixels are lit in the first frame and the second frame, and in gradation 3, all three R, G, and B pixels are illuminated in all three frames. Light all. Note that in FIG. 7, the pixels that are turned on are indicated by broken lines.

That is, in the conventional frame gradation method, the number of frames to be lit is sequentially increased from the first frame as the gradation level increases from dark to bright.

[0008]

However, in such a conventional liquid crystal display device, the first frame that is turned on as the gradation degree increases from dark to bright
Since the number is sequentially increased from the frame, the brightness and darkness of each frame are coordinated, and there is a problem that flicker is noticeable.

Particularly, in a color liquid crystal display device in which one pixel is composed of three pixels of R, G and B, conventionally,
3 of R, G, and B that compose one picture element with one frame
Since all one pixel was lit at the same time, there was a problem that flicker was more noticeable.

For example, in the case of displaying the gradation 2 in the 4 gradation display, conventionally, as shown in FIG. 8 by ".largecircle." For the lit pixel and ".circle-solid." With three frames as one cycle, all the R, G, and B pixels that make up one pixel in the first frame are turned off, and all the R, G, and B pixels in the second and third frames are turned off. It is lit.

Therefore, as can be seen from FIG. 8, the brightness and darkness of each frame becomes clear and flicker occurs.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal display device capable of suppressing flicker.

[0013]

A liquid crystal display device according to the present invention is an LCD for displaying a full color of n gradations in which each picture element is composed of three pixels of R, G and B. , B pixels are appropriately dispersed in the thinning-out timing, and a dispersing means for reducing the frequency of the thinning-out timings simultaneously is provided to achieve the above object.

In this case, for example, as described in claim 2, the dispersing means sequentially shifts the frame for starting the lighting of the picture element to the front side or the rear side each time the frame count number increases. By doing so, the frames in which the picture elements are lit among the plurality of frames may be scattered according to the gradation.

Further, the dispersion means is, for example, as defined in claim 3.
As described in (1), a frame determination circuit for determining a frame, and a selection circuit for selecting a frame for lighting the picture element based on the gradation degree and the determination result of the frame determination means may be provided. .

Further, in the liquid crystal display device of the present invention, for example, as described in claim 4, the picture element is composed of a plurality of pixels, and the dispersion means is composed of a plurality of pixels constituting the picture element. May be lit by being scattered over the plurality of frames.

[0017]

According to the liquid crystal display device of the present invention, the R, G, and B pixels forming each picture element are appropriately thinned, and the timings of thinning the pixels are simultaneously distributed. Since the dispersion means for reducing the number is provided, it is possible to prevent the uneven brightness and the occurrence of flicker in the liquid crystal display device that displays n-color full color with a simple circuit configuration. .

In this case, as described in claim 2, the dispersing means sequentially shifts the frame for starting the lighting of the picture element to the front side or the rear side every time when the number of counts of the frame increases, so that a plurality of frames can be obtained. If the frames for lighting the picture elements among the frames are scattered according to the gradation, the flicker can be prevented with a simpler circuit configuration.

Further, as described in claim 3, when the dispersing means appropriately selects the frame for lighting the picture element based on the gradation and the frame, the frame for lighting is appropriately selected according to the gradation. It is possible to set, and it is possible to further scatter the picture elements that are turned on by a simpler circuit configuration.

Further, as described in claim 4, when the picture element is composed of a plurality of pixels, the plurality of pixels forming the picture element are scattered in a plurality of frames to be turned on. Then, in the color liquid crystal including the three pixels of R, G, and B, each pixel can be turned on in a different frame, and the uneven brightness can be further prevented. As a result, it is possible to further suppress the occurrence of flicker in a liquid crystal display device that displays color.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 6 are views showing a liquid crystal display device according to the present invention.

First, the structure will be described.

FIG. 1 is a block diagram showing the configuration of the liquid crystal display device 1 of this embodiment, and this embodiment is applied to the liquid crystal display device 1 which performs gradation display by time-division driving.

In FIG. 1, the liquid crystal display device 1 is composed of a liquid crystal display panel 2, a signal side drive circuit 3, a scanning side drive circuit 4, a synchronization processing circuit 5, a controller 6, an A / D converter 7, and the like. .

As the liquid crystal display panel 2, a simple matrix type liquid crystal display panel is used here, and a scanning line and a signal line sandwich a liquid crystal layer inside a glass substrate opposed to each other with a fine interval. They are arranged in a matrix.

The signal side drive circuit 3 outputs a display signal to the signal line of the liquid crystal display panel 2 based on video data.

The scanning side drive circuit 4 applies a scanning signal for line scanning the scanning lines of the liquid crystal display panel 2.

The synchronization processing circuit 5 takes out the vertical synchronization signal φV (Vsync) and the horizontal synchronization signal φH (Hsync) from the input composite video signal and outputs it to the controller 6, and also A / D-converts the video signal V. Output to the container 7.

The controller 6 controls the overall timing of the display control of the liquid crystal display panel 2. For example, the controller 6 supplies the sampling clock SCK to the A / D converter 7 in synchronization with the vertical and horizontal synchronization signals φV and φH supplied from the synchronization processing circuit 5. Further, the controller 6 includes the signal side drive circuit 3
And a timing signal (frame clock, line clock, dot clock) for driving the scanning side drive circuit 4.

The A / D converter 7 samples the input analog video signal V by a sampling clock (SCK) from the controller 6, and outputs a predetermined bit, that is, two bits of "0" and "1" in this embodiment. The signal side drive circuit 3 converts the video data of R, G, B digitized by
Output to.

FIG. 2 is a circuit block diagram of an essential part of the signal side drive circuit 3 of FIG.

In FIG. 2, the signal side driving circuit 3 includes a frame counter 11, a line counter 12, a dot counter 13, a decoder 14, selectors 15, 16, 17 and latches 18, 19 and other distribution circuits (dispersion means) 20.
Is equipped with.

Frame counter (frame discrimination circuit) 1
1 to the vertical synchronization signal (Vsyn from the controller 6).
c) and the horizontal sync signal (Hsync) are input, and the frame counter 11 receives the vertical sync signal (Vsync) and the horizontal sync signal (Hsync) as shown in FIG.
For each frame based on c), "0", "1",
The count value is incremented by "2", ... +1, and the count value is output to the line counter 12. That is, the frame counter 11 counts the count value which is the time axis of the thinning pattern and outputs the count value to the line counter 12.

The line counter 12 includes a controller 6
To horizontal sync signal (Hsync) and dot clock D
As shown in FIG. 3, the line counter 12 receives the otCK, and the line counter 12 receives the otCK based on the horizontal synchronizing signal (Hsync) and the dot clock DotCK for each line.
"0", "1", "2", "0", ... Counts up by +1 and outputs the count value to the dot counter 13.

The dot counter 13 includes a controller 6
, The dot clock DotCK and the basic clock CLK are input, and the dot counter 13 receives “1” and “2” each time the dot clock DotCK is input, that is, for each dot, as shown in FIG. , "0",
The count value is incremented by "1", ... And +1 and the count value is output to the decoder 14.

That is, the dot counter 13 counts dot by dot in the horizontal scanning direction and counts the progress of each dot in the horizontal scanning direction.

The decoder 14 decodes the output of the dot counter 13, that is, the count value of the dot counter 13, and outputs a selection signal for determining the selection state of the selectors 15, 16 and 17, which will be described later, to the s terminal of the selector 15 and the latch 18. Output to the D terminal.

The selector 15 receives the video signal R0 and the video signal R1, which are 2-bit R video data, at its d0 terminal and d1 terminal, respectively.
From the decoder 1 to the s terminal.
Input from 4.

Based on the selection signal input from the decoder 14 to the s terminal, the selector 15 inputs the video signal R0 input to the d0 terminal and the video signal R1 input to the d1 terminal, as shown in FIG. And are selectively selected and output from the Q terminal as the R video signal after the thinning process.

That is, when the selection signal of "0" is input to the s terminal, the selector 15 selects the video signal R0 input to the d1 terminal and the selection signal of "1" is input to the s terminal. Then, the video signal R1 input to the d0 terminal is selected and output.

A basic clock CLK is input to the latch 18 in addition to the selection signal from the decoder 14, and the latch 18 delays the selection signal by one basic clock CLK and the s terminal of the selector 16 and Output to the latch 19.

The selector 16 receives the video signal G0 and the video signal G1 which are 2-bit G video data at the d0 terminal and the d1 terminal, respectively, and the A / D converter 7 of FIG.
Is input from the latch 18 and the selection signal is latched at its s terminal.
Input from. This selector 16 has the latch 18
Based on the selection signal input to the s terminal, the video signal G0 input to the d0 terminal and the video signal G1 input to the d1 terminal, as shown in FIG.
And are selectively selected and output from the Q terminal as the G video signal after the thinning process.

The basic clock CLK is input to the latch 19 in addition to the selection signal from the latch 18.
The latch 19 delays the selection signal by one dot and outputs it to the s terminal of the selector 17.

The selector 17 receives the video signal B0 and the video signal B1, which are 2-bit B video data, at its d0 terminal and d1 terminal, respectively.
Is input from the latch 19 and the selection signal is latched at its s terminal.
Input from. This selector 17 has the latch 19 described above.
Based on the selection signal input to the s terminal, the video signal B0 input to the d0 terminal and the video signal B1 input to the d1 terminal, as shown in FIG.
And are selectively selected and output from the Q terminal as the B video signal after the thinning process.

Therefore, the decoder 14, the selectors 15, 16, 17 and the latches 18, 19 function as a whole as a selection circuit for selecting a frame for lighting the liquid crystal display device.

Next, the operation of this embodiment will be described.

The liquid crystal display device 1 separates the sync signal and the video signal V from the composite video signal input by the sync processing circuit 5, and outputs the vertical sync signal φV (Vsync) and the horizontal sync signal φH (Hsync) to the controller 6 And outputs the analog video signal V to the A / D converter 7.

The controller 6 synchronizes with the vertical and horizontal synchronization signals φV and φH supplied from the synchronization processing circuit 5,
The sampling clock SCK is output to the A / D converter 7, and a timing signal for driving the signal side driving circuit 3 and the scanning side driving circuit 4 is output.

The A / D converter 7 samples the video signal V input from the synchronization processing circuit 5 by the sampling clock SCK from the controller 6 and converts it into 2-bit digital R, G, B video data. Then, the scanning side driving circuit 4 for outputting to the signal side driving circuit 3 sequentially outputs the scanning signal to each scanning line of the liquid crystal display panel 2 based on the timing signal supplied from the controller 6, and sequentially outputs each scanning line. To scan.

The signal side drive circuit 3 samples the 2-bit R, G, B video data input from the A / D converter 7 and performs thinning-out processing so that only the frames corresponding to the video data are processed. The pixel to be turned on is lit to display a gradation.

At this time, the signal side drive circuit 3 is operated by the R, G, B
When four gradations are displayed in three frames based on the video data of 3), each frame for lighting the picture element is scattered according to the gradation degree, and each pixel of R, G, B constituting the picture element is scattered in the frame. I'm throwing it away.

That is, the signal side drive circuit 3 causes the frame counter 11 to set the frames serving as the time axis of the thinning pattern to "0", "1", as shown in FIG.
As shown in FIG. 3, the line counter 12 counts “2”, ..., And outputs the count value to the line counter 12. 1 ”,“ 2 ”,“ 0 ”, ... Are counted and the count value is output to the dot counter 13. Then, the dot counter 13 is "1", "2", "0", "1", for each dot in each frame.
... is counted and the count value is latched 18
And to the s terminal of the selector 15. In this way, the frame counter 11 checks the current frame, the line counter 12 checks the current scan line, and the dot counter 13 checks the current dot position.

Then, the R video data is selected by the selector 15, the G video data is selected by the selector 16, and the B video data is selected by the selector 17 and output as thinned video data R, G, B, respectively.

At this time, the decode output of the decoder 14 input to the s terminal of the selector 15 is "1", "0", "0", "1", ... As shown in FIG. Become 2
It is bit data, and the decode output of this decoder 14 is delayed by one dot in the latch 18 and
6 and is further delayed by 1 dot by the latch 19 and input to the selector 17.

Then, as shown in FIG. 4, when "0" is input to the s terminal, the selectors 15, 16 and 17 output the video data input to the d1 terminal as thinned video data. Then, when "1" is input to the s terminal, the video data input to the d0 terminal is output as thinned video data.

Therefore, as shown by the broken line pattern in FIG. 5, at the gradation level 1, in the first frame, the R pixel is in the second frame, the G pixel is in the third frame, and the B pixel is in the third frame. In the gradation 2, the G pixel and the B pixel are in the first frame, the R pixel and the B pixel are in the second frame, and the R pixel and the G pixel are in the third frame. Each pixel lights up. Further, at the gradation level 3, all the R, G, and B pixels are turned on in all the frames from the first to the third. At the gradation level of 0, all the R, G, and B pixels are not lit in all the frames from the first to the third.
That is, it is thinned out and does not light up.

As a result, for example, in the case of a gradation level of 2,
In each pixel, one pixel includes R, G, and
Of the three B pixels, two pixels are turned on at the same time for each frame, and the R, G, and B pixels that are turned on can be shifted by one pixel each time the frame advances, and the pixels are turned on. Pixels can be scattered. Therefore, it is possible to prevent all the pixels of R, G, and B from lighting at the same time and in continuous frames as in the conventional art, and suppress the unevenness of brightness and darkness in each frame to suppress the occurrence of flicker. can do.

Further, the scanning lines scanned by the line counter 12 are counted, and for each scanning line, as shown in FIG.
Since the R, G, B pixels that start lighting are shifted, the R, G, B lighting pixels can be scattered even in the scanning line direction, and the occurrence of flicker can be further suppressed. it can.

As described above, according to this embodiment, by lighting the picture elements in the plurality of frames the number of times corresponding to the gradation, the frame in which the picture elements are lit is displayed in the gradation Since it is scattered by, it is possible to prevent the unevenness of light and dark with a simple circuit configuration,
The occurrence of flicker can be suppressed.

Further, since the frames for starting the lighting of the picture elements are sequentially shifted to the rear side as the gradation degree increases, it is possible to prevent the occurrence of flicker with a simpler circuit configuration.

Further, since the frame for lighting the picture element is appropriately selected based on the gradation and the frame, the frame for lighting can be appropriately set according to the gradation, and the simpler circuit configuration allows It is possible to make the picture elements that light up even more scattered.

Further, since each picture element is composed of three pixels of R, G, and B, and the three pixels composing the picture element are scattered in a plurality of frames to be lit, Pixels can be lit in different frames,
It is possible to further prevent uneven brightness. As a result, it is possible to further suppress the occurrence of flicker in a liquid crystal display device that displays color.

In the above embodiment, the case of displaying 4 gradations in 3 frames has been described, but the number of gradations is not limited to the above 4 gradations, and 8 gradations are obtained in 7 frames. The same can be applied to the arbitrary gradation display such as when 16 gradations are obtained in 15 frames or the like as in the above embodiment.

Although the invention made by the present inventor has been specifically described based on the preferred embodiments, the present invention is not limited to the above embodiments and various modifications are possible without departing from the scope of the invention. It goes without saying that it can be changed.

[0065]

According to the liquid crystal display device of the first aspect of the invention, the three pixels of R, G, and B which constitute each picture element are simultaneously dispersed by appropriately distributing the timing of thinning each pixel. The distribution means is provided to reduce the frequency of drawing timing.

Therefore, with a simple circuit configuration, in the liquid crystal display device for displaying full-color of n gradations, it is possible to prevent the unevenness of light and dark and suppress the occurrence of flicker.

In this case, as described in claim 2, the dispersing means sequentially shifts the frame for starting the lighting of the picture element to the front side or the rear side each time the frame count number increases, so that a plurality of frames can be obtained. If the frames for lighting the picture elements among the frames are scattered according to the gradation, the flicker can be prevented with a simpler circuit configuration.

Further, as described in claim 3, when the dispersion unit appropriately selects the frame for lighting the picture element based on the gradation and the frame, the frame for lighting is appropriately selected according to the gradation. It is possible to set, and it is possible to further scatter the picture elements that are turned on by a simpler circuit configuration.

Further, as described in claim 4, when the picture element is composed of a plurality of pixels, the plurality of pixels composing the picture element are scattered in a plurality of frames to be turned on. Then, for example, in a color liquid crystal composed of three pixels of R, G, and B, each pixel can be turned on in a different frame, and the bias of light and dark can be prevented further. As a result, it is possible to further suppress the occurrence of flicker in a liquid crystal display device that displays color.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to an embodiment.

FIG. 2 is a circuit block diagram of a signal line drive circuit in FIG.

FIG. 3 is a timing chart of signals of respective parts of the signal side drive circuit shown in FIG.

4 is a diagram showing a selection relationship between a selection signal input to the s terminal of the selector of FIG. 2 and d0 and d1 terminals input of a video signal.

5 is a diagram showing a thinning pattern for each gradation in the case of 4-gradation display by the signal side drive circuit shown in FIG.

FIG. 6 is a diagram showing an example of a gray scale display screen with a gray scale of 2 when the thinning process is performed by the signal side drive circuit shown in FIG.

FIG. 7 is a diagram showing a thinning pattern for each gradation in the conventional 4-gradation display.

FIG. 8 is a diagram showing an example of a display image on a liquid crystal display screen when a thinning process using a conventional thinning pattern is performed.

[Explanation of symbols]

 1 liquid crystal display device 2 liquid crystal display panel 3 signal side drive circuit 4 scanning side drive circuit 5 synchronization processing circuit 6 controller 7 A / D converter 11 frame counter 12 line counter 13 dot counter 14 decoder 15, 16, 17 selector 18, 19 Latch 20 distributed circuit

Claims (4)

[Claims] 1. A liquid crystal display device for displaying a full color of n gradations in which each picture element is composed of three pixels of R, G, B, wherein each of the R, G, B pixels is thinned out. A liquid crystal display device, characterized in that a dispersion means is provided for appropriately distributing timings and reducing the frequency of timings to be simultaneously thinned. 2. The dispersing means sequentially shifts the frame for starting the lighting of the picture element to the front side or the rear side every time when the count number of the frame increases, thereby lighting the picture element of the plurality of frames. 2. The liquid crystal display device according to claim 1, wherein the frames to be dispersed are scattered according to the gradation. 3. The dispersion means comprises a frame discrimination circuit for discriminating a frame, and a selection circuit for selecting a frame for lighting the picture element based on the gradation degree and the discrimination result of the frame discrimination means. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 4. The liquid crystal display device, wherein the picture element is composed of a plurality of pixels, and the dispersion means lights the plurality of pixels composing the picture element in the plurality of frames in a scattered manner. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.