JPH09127917A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the residual image generated when a dynamic image is displayed in a liquid crystal display device. SOLUTION: In addition to a switching element 12 for write signal application to a liquid crystal picture element, a second switching element 14 for black signal application is provided in parallel thereto. The second switching element 14 is selectively ON to supply a black signal from a black signal supplying part 7 to the picture element 11 through a black signal feed line 8, and the erasing (reset) of write signal is performed.

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, and more particularly to a liquid crystal display device having a group of liquid crystal display elements arranged in a matrix.

[0002]

2. Description of the Related Art Currently, matrix type liquid crystal display devices are
From those mainly dealing with still screens such as personal computers and word processors, they have entered the field mainly dealing with moving images such as television receivers by taking advantage of their features such as thinness and light weight and low power consumption.

FIG. 5 shows an example of a conventional matrix type liquid crystal display device. In FIG. 5, a TFT (Thin Fi) which is a three-terminal element is used as an active element for driving a pixel.
lmTransistor). This TFT panel has liquid crystal display cells 1 arranged in a matrix of n rows * m columns, and each liquid crystal display cell 1 includes a liquid crystal pixel (hereinafter abbreviated as "pixel") 11.

[0004] In the vicinity of each pixel 11, a TFT 12 is provided.
Are connected to the electrodes. A common counter electrode 13 is connected to the electrodes of all the pixels 11.

[0005] On a TFT panel, n scanning lines 2 are arranged in parallel. The j-th (j = 1, 2,..., n) -th scanning line 2 is connected to an opening / closing control terminal (gate electrode) of the TFT 12 in the j-th row. The m column direction signal lines 3 are arranged in parallel so as to be orthogonal to the scanning lines 2 in the row direction. The k (k = 1, 2, ..., M) th signal line 3 has k
The signal input terminal (source electrode) of the TFT 12 in the column is connected.

The TFT liquid crystal panel is driven by a driving circuit including a gate driver 4 and a source driver 5.
The gate driver 4 and the source driver 5 are connected to the scanning line 2 and the signal line 3 of the TFT liquid crystal panel, respectively.

[0007] The video signal is input to the source driver 5. A control signal such as a sampling clock input to the gate driver 4 is supplied from an external control circuit (not shown).

In this type of conventional liquid crystal driving method, the signal component of the pixel of the previous frame is left until the pixel of the next frame is written, and this signal component appears as an afterimage. Become. As a conventional technique for canceling this afterimage, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 1-280787. When a screen is switched from a display content fixed for a certain time to another display content, An afterimage canceling technique for inserting a second screen in which the brightness is temporarily reversed is disclosed.

[0009]

Since a liquid crystal pixel has a capacitance characteristic, a voltage written in the pixel is held for a certain period of time. For this reason, in a conventional liquid crystal display device, on a screen such as a word processor or a personal computer that mainly handles a still screen, an afterimage does not occur even if a signal component of a pixel of a previous frame remains, but it is not like a television. When handling a moving image in which a certain pixel hardly matches the pixel of the next frame, there is a problem that an afterimage is generated due to the integration effect.

For example, as shown in FIG. 6A, when there is a screen called a white window on a black background, and the white window moves rightward in the next frame as shown in FIG. 6B,
The portion that was a white signal in the previous frame is recognized as an afterimage.

Focusing on a pixel that changes from white to black,
FIG. 7 is a graph showing the vertical time axis on the X axis and the afterglow energy of the pixel on the Y axis. In FIG. 7, the white level which is the signal of the previous frame is almost maintained until immediately before the black signal is written due to the capacitance characteristic of the liquid crystal. Therefore, immediately after writing black, an afterimage in which a white signal remains is recognized by the afterimage effect.

Further, the prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 1-280787 is effective in suppressing an afterimage at the time of screen switching in a case of a still image in which the same screen is displayed for a certain period of time or the like. However, the effect in the case of a moving image whose image constantly changes is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device having a function of canceling an afterimage in which an afterimage does not occur even in a still image or a moving image.

[0014]

According to the present invention, a display 1 is provided.
A liquid crystal display element matrix section in which a plurality of display elements corresponding to pixels are arranged in a matrix; a scanning line for selectively scanning the same row direction display element group of the liquid crystal display element matrix section; A signal line for supplying a write signal for display with respect to the element group, the signal line being provided for each of the display elements, conducting in response to a black signal supply command signal, and A black signal supply element for supplying a black signal, a black signal supply command selection line for selectively selecting the black signal supply command signal for a black signal supply element group in the same row direction, and all the black signals. Black signal applying means for applying to the black signal supply element,
In the vertical scanning period, means for selectively supplying the black signal supply command signal to the black signal supply command selection line in the row direction during a period other than the selective writing period in the same row direction display element group, A liquid crystal display device including:

Further, according to the present invention, a liquid crystal display element group arranged in a matrix and a first switching element group provided corresponding to each liquid crystal display element and connected to the corresponding liquid crystal display element. A second switching element group connected to the liquid crystal display element in parallel with each of the first switching element groups, and a first switching element connected to the switching control terminal of the first switching element group in the same row direction. Scanning line group, the signal line group connected to the signal input terminal of the first switching element group in the same column direction, and the second signal line group connected to the switching control terminal of the second switching element group in the same row direction. The scanning line group, the second signal line group connected to the signal input terminals of the second switching element groups in the same column direction and supplied with the black signal, and the display signal writing period in the vertical scanning period, First signal Means for selecting scan group, a period other than the writing period, the liquid crystal display device is obtained which comprises a means for selecting scanning the second select line group.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described. A second switching element is provided in addition to the switching element for writing the display signal to the liquid crystal, and the second switching element is turned on during a period other than the writing period, so that the signal accumulated in the liquid crystal during the writing period is blackened. By forcibly resetting the signal, the afterimage is suppressed.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention, and the same parts as those in FIG. 5 are denoted by the same reference numerals. n
Liquid crystal display cells 1 are arranged in a matrix of rows * m columns. Each of these cells 1 has a pixel 11 and a pixel 1
Two switching elements 1 connected in parallel to 1
2 and 14.

One electrode 13 of the pixel 11 is a common electrode for all the cells 1. The other electrode of the pixel 11 is connected to the drains of the two switching elements 12 and 14, the source of the switching element 12 is the display signal line (column line) 3, and the gate (opening / closing control electrode) is the row selection scanning line. Two
Connected to each other.

The source of the switching element 14 is connected to the black signal supply line 8, and its gate is connected to the black signal supply command selection line 9. The output of the black signal supply unit 7 is commonly supplied to all the black signal supply lines 8, and a signal voltage corresponding to black display of the pixel 11 is supplied.

The black signal supply command selection line 9 is selectively driven by the second gate driver 6. The row selection scanning line 2 is selectively driven by the first gate driver 4, and
The display signal line 3 is driven by the source driver 5.

The operation will be described in detail with reference to FIG. 1. When the scanning line 2 arbitrarily selected by the gate driver 4 is driven during a vertical scanning period of one frame, the selected scanning is performed. A voltage corresponding to a video signal voltage is applied to the liquid crystal pixels 11 from the source driver 5 through the switching elements 12 connected to the lines 2 and the signal lines 3.

By sequentially changing the driving of the row selection scanning lines 2 corresponding to the display scanning lines of the input video signal, one screen can be written. When the black signal supply command selection line 9 arbitrarily selected by the gate driver 6 is driven during the vertical scanning period of the same one frame, the selected black signal supply command selection line 9 and the black signal supply line group A signal voltage corresponding to a black signal is applied to the liquid crystal pixel group 11 from the black signal supply unit 7 through the switching elements 14 connected to the switching element 8.

By repeating this operation while changing the driving scanning line, one screen can be erased.

These series of operations are performed by appropriately driving the scanning line 2 and the black signal supply command selection line 9 so as not to apply a voltage to the same liquid crystal pixel at the same time, and within the vertical scanning period of one frame. By simultaneously writing and erasing one screen, the occurrence of an afterimage can be suppressed.

FIG. 2 shows a part of an example of display timing in the driving circuit of the liquid crystal display device of FIG. By inputting a write start pulse synchronized with the vertical synchronizing signal to the gate driver 4, driving of the scanning line 2 for writing to the liquid crystal pixels starts.

In the same vertical scanning period, the erase start pulse is input to the gate driver 6 with a timing delayed from the generation of the write start pulse. Thus, the driving of the black signal supply command selection line 9 for erasing the liquid crystal pixels starts.

The display contents of a certain liquid crystal pixel by these operations are also shown at the bottom of FIG. 2. The time difference A between the write start pulse and the erase start pulse coincides with the input video signal display period of the liquid crystal pixel. It is assumed that

By doing so, the image displayed on the liquid crystal display device is as shown in FIGS. 3A to 3D, and the period during which a black signal is displayed between one frame display and the next frame display. Is generated, and this is alternately repeated.

As described above, according to the configuration of the present embodiment, the light emission time of the pixel from the scanning of a frame of a certain video signal to the scanning of the next frame is shorter than in the conventional case. FIG. 4 shows the light emitting state of this pixel. Since black is scanned between the scanning of a frame of a certain video signal and the scanning of the next frame, the effect of the afterglow of the pixel on the pixels of the next frame is reduced as compared with FIG. Can understand.

[0031]

As described above, according to the present invention,
In the image displayed on the liquid crystal display device, since the video signal and the black signal are repeatedly displayed in one frame, the light emission time of the pixel from scanning one frame of the video signal to scanning the next frame is determined. Is shorter than before, the effect of the afterglow of the pixels on the pixels of the next frame is reduced, and thus the effect of generating an afterimage when displaying a moving image is greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a schematic diagram schematically showing timings of writing and erasing of liquid crystal pixels in a vertical scanning period in the circuit of FIG.

FIG. 3 is a schematic diagram schematically showing a scanning state of a frame according to the embodiment of the present invention.

FIG. 4 is a schematic diagram schematically showing a light emitting state of a liquid crystal pixel in an example of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a conventional active matrix type liquid crystal display circuit.

FIGS. 6A and 6B are schematic diagrams showing a process of generating an afterimage in a conventional liquid crystal display circuit.

FIG. 7 is a schematic view schematically showing a light emitting state of liquid crystal pixels in a conventional liquid crystal display circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Display cell 2 Row selection scanning line 3 Signal line 4, 6 Gate driver 5 Source driver 7 Black signal supply part 8 Black signal supply line 9 Black signal supply command selection line

Claims (3)

[Claims] 1. A liquid crystal display element matrix section in which a plurality of display elements corresponding to one display pixel are arranged in a matrix, and a scanning line for selectively scanning the same row-direction display element group of the liquid crystal display element matrix section. And a signal line for supplying a write signal for display to the same column direction display element group, which is provided corresponding to each of the display elements and responds to a black signal supply command signal. A black signal supply element for conducting and supplying a black signal to the corresponding display; and a black signal supply command selection line for selectively supplying the black signal supply command signal to a group of black signal supply elements in the same row direction. A black signal applying means for applying the black signal to all the black signal supply elements, and the black signal in the row direction during a period other than the selective writing period to the same row direction display element group in the vertical scanning period. The liquid crystal display device which comprises a selectively supplying means to the black signal supply command signal to supply command selection line. 2. A liquid crystal display element group arranged in a matrix, a first switching element group provided corresponding to each liquid crystal display element and connected to the corresponding liquid crystal display element, and a first switching element group A second switching element group connected to the liquid crystal display element in parallel with each of the switching element groups, a first scanning line group connected to an open / close control terminal of the first switching element group in the same row direction, First in the same column direction
Signal line group connected to the signal input terminal of the switching element group, the second scanning line group connected to the switching control terminal of the second switching element group in the same row direction, and the second scanning line group in the same column direction. A second signal line group connected to a signal input terminal of the switching element group and supplied with a black signal; and means for selectively scanning the first signal line group during a display signal writing period in the vertical scanning period. A liquid crystal display device comprising: means for selectively scanning the second selection line group during a period other than the writing period. 3. The liquid crystal display device according to claim 2, wherein the second signal line group is commonly supplied with a black signal.