JP2000330524A - Driving method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a damage of display picture uniformity caused by charge and discharge of electric charges stored at pixel electrodes generated from driving of a liquid crystal display device and by discontinuity of reversed driving. SOLUTION: A video signal is stored in a hold condenser part 4 by controlling a sample control transistor 5 from a vertical scanning driver circuit 12. When scanning is executed from the first vertical scanning line to the N-th vertical scanning line, video signals of one picture amount are stored in the hold condenser part 4 of each pixel. Next by controlling a pixel transistor 3 by a pixel transistor driver circuit 15 during a flying back period of the video signal, the video signals of one picture amount stored in each hold condenser part 4 are written into a liquid crystal pixel part 2. By such driving as this, a current leak between the liquid crystal pixel part 2 and video signal lines 13 is reduced and discontinuity of reversed driving can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of driving an active matrix type liquid crystal display device (international patent classification G02).
F 1/13).

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for large-screen image display devices for enjoying powerful images with the enhancement of video equipment such as video tape recorders and video disk players and video software. As a conventional large-screen image display device, there has been a television using a CRT.
Since the CRT is used for the image display unit, there is a limitation in miniaturizing the apparatus due to physical restrictions of the CRT. A liquid crystal display device using a liquid crystal panel for an image display unit has been proposed in order to eliminate this limitation and reduce the size of the device. An example of a conventional liquid crystal display device using a liquid crystal panel is disclosed in, for example, JP-A-4-188104.

FIG. 3 is a block diagram showing an example of a conventional liquid crystal display device using a liquid crystal panel. In FIG. 3, an input video signal is processed by a video signal processing circuit 61 into a form for displaying an image on a liquid crystal panel 51 and is applied to a horizontal scanning driver circuit 54. Further, the horizontal synchronizing signal and the vertical synchronizing signal are separated from the video signal by the synchronizing signal separating circuit 62, and are applied to the liquid crystal panel drive control circuit 63.
The liquid crystal panel drive control circuit 63 generates a control signal for displaying an image on the liquid crystal panel 51 from the input synchronization signal, and is applied to the horizontal scan driver circuit 54 and the vertical scan driver circuit 55.

[0004] In order to display an image on the liquid crystal panel 51, a horizontal scanning driver circuit 54 performs horizontal scanning, and a vertical scanning driver circuit 55 performs vertical scanning. Here, the scanning in the vertical direction is performed for all the lines on the liquid crystal panel 51 in order. The video signal lines 5 are displayed at the timing of displaying an image from each driver circuit.
6 is applied to the scanning signal line 57 and the transistor 5
An image is displayed on the liquid crystal panel 51 by controlling 3 and applying a signal to the liquid crystal pixel section 52. The liquid crystal pixel portion 52 is equivalently represented by a liquid crystal capacitance, and is connected to a drain electrode of the transistor 53. A common electrode potential Vc is applied from a common electrode power supply 58 to a corresponding common electrode of one terminal of the liquid crystal capacitor.

In driving a liquid crystal display device, an AC driving method is used to prevent the liquid crystal from deteriorating due to driving.
In the AC driving method, the polarities of pixel electrodes adjacent in the scanning line direction (horizontal direction) are the same, and the polarities of pixel electrodes adjacent in the signal line direction (vertical direction) are alternately opposite polarities. Inversion driving in which the polarity of each pixel electrode is inverted every frame period, or frame inversion driving in which the polarity of pixel electrodes adjacent in the signal line direction (vertical direction) is the same and the polarity of each pixel electrode is inverted every frame period There is.

FIG. 4 is a timing chart showing an example of a conventional driving method of a liquid crystal display device. FIG. 4 illustrates the case of line inversion driving.

As described above, the vertical scanning of the liquid crystal panel 51 is performed by sequentially outputting the gate pulse signals from the vertical scanning driver circuit 55 line by line for all the lines. A certain scanning signal line X
The gate pulse signal output from the vertical scanning driver circuit 55 for i is a voltage Vg-on for turning on the transistor Tr during the on period, and a voltage Vg-off for turning off the transistor Tr during the off period. Has been applied. Thereby, the video signal line Y is turned on during the ON period.
i is supplied to the transistor T
r is written to the liquid crystal pixel section 52. On the other hand, since the transistor Tr is in the off state during the off period, the charge written in the liquid crystal pixel portion 52 is held as it is.

[0008]

As described above, in a liquid crystal display device, an image is displayed by writing / holding a video signal in a liquid crystal pixel by turning on / off a gate pulse signal. In the case, the pixel at the beginning of the vertical scanning has the same polarity as the polarity of the video signal output to the video signal line and the polarity of the video signal held by the liquid crystal pixel portion during most of the vertical scanning period. On the other hand, in the pixel at the end of the vertical scanning period, the polarity of the video signal output to the video signal line and the polarity of the video signal held by the liquid crystal pixel portion are opposite in most of the vertical scanning period. Therefore, there is a problem that the luminance of the screen is inclined in the vertical scanning direction due to a difference in leakage current of the transistor 53 caused by a difference in potential between the video signal line and the liquid crystal pixel portion.

For this reason, at present, line inversion driving is widely used as a driving method for solving the problem of frame inversion driving.

However, at the timing of writing the video signal to the liquid crystal pixel portion, discontinuity occurs in the polarity inversion because the polarity of the video signal on the line adjacent in the vertical direction of the screen is the same. As a result, when the image moves slowly in the vertical direction, the polarity inversion cycle appears to be halved, and the screen may appear to flicker, thereby deteriorating the display quality.

[0011]

In order to solve the above-mentioned problems, a method of driving a liquid crystal display device according to the present invention comprises an active matrix in which pixel electrodes having at least one or more switching transistors are arranged in a matrix. A method for driving a liquid crystal display device comprising a liquid crystal layer sandwiched between a substrate and a common electrode substrate having a transparent electrode, wherein a video signal is applied to the pixel electrode during a certain period during one vertical scanning period of the liquid crystal display device. It is characterized in that writing is performed simultaneously on all electrodes.

According to the present invention, the fluctuation of the electric charge held in the liquid crystal pixel portion caused by the driving of the liquid crystal display device is reduced, and it is possible to prevent the occurrence of a discontinuous portion in the polarity inversion. It is possible to provide a liquid crystal display device having good display quality while maintaining uniformity on a display screen.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A driving method of a liquid crystal display device according to the present invention is directed to a method of driving a liquid crystal display using a common electrode substrate having a transparent electrode and an active matrix substrate having pixel electrodes having at least one switching transistor arranged in a matrix. A method for driving a liquid crystal display device having a layer sandwiched therebetween, comprising: a sample-and-hold circuit for holding a video signal written to each of the pixel electrodes; and a switching circuit for writing a video signal to the pixel electrodes. After the input video signal is held by the sample and hold circuit for each of the pixel electrodes for one vertical scanning period of the liquid crystal display device, the switching transistor is used during a certain period during one vertical scanning period. The liquid crystal display device is characterized in that writing is performed simultaneously on all the pixel electrodes. The uniformity on the display screen is maintained by reducing the fluctuation of the electric charge held in the liquid crystal pixel portion caused by the driving of the liquid crystal display and preventing the occurrence of discontinuous portions in the polarity inversion. It has the effect that image quality can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a configuration diagram showing a configuration of a liquid crystal display device according to a method of driving a liquid crystal display device according to the present invention, wherein 1 is a liquid crystal panel, 2 is a liquid crystal pixel portion for displaying an image on the liquid crystal panel 1, Is a pixel transistor for controlling image display on the liquid crystal pixel unit 2, 4 is a hold capacitor unit for holding a video signal, and 5 is a sample for controlling a sample and hold operation of the video signal to the hold capacitor unit 4. A control transistor 6 is a common electrode power supply for applying a common electrode potential to a common electrode which is an electrode at one end of the liquid crystal pixel section 2. Circuit, 12
Is a vertical scanning driver circuit for similarly performing vertical scanning, 13 is a video signal line for transmitting a video signal from the horizontal scanning driver circuit 11, and 14 is a scanning signal from the vertical scanning driver circuit 12. Is a pixel signal driver circuit for controlling the pixel transistor 3 to write a video signal to the liquid crystal pixel section 2, and 16 is a pixel transistor driver circuit 1
A pixel transistor control signal line for transmitting a control signal from 5; a video signal processing circuit 21 for processing a video signal to be displayed on the liquid crystal panel 1; A synchronizing signal separating circuit 23 for separating a synchronizing signal is a liquid crystal panel drive control circuit for generating a control signal necessary for displaying an image on the liquid crystal panel 1 from the input synchronizing signal.

The operation of the liquid crystal display device using the method for driving the liquid crystal display device configured as described above will be described with reference to FIG. FIG. 2 is a timing chart for explaining the operation of the liquid crystal display device driving method according to the present invention.

As described in the background art, the vertical scanning of the liquid crystal panel 1 is performed by outputting the gate pulse signal from the vertical scanning driver circuit 12 for all the lines in order one line at a time. . FIG.
5 shows a gate pulse signal output from the first vertical scanning line to the Nth vertical scanning line on the assumption that the number of pixels in the vertical direction of the liquid crystal panel 1 is N.

When a gate pulse signal is output from the vertical scanning driver circuit 12, the sample control transistor 5 connected to the scanning signal line 14 is turned on, and is output from the horizontal scanning driver circuit 11 to the video signal line 13. The stored video signal is stored in the hold capacitor unit 4. At this time, since the pixel transistor 3 is turned off by the pixel transistor driver circuit 15, no video signal is written to the liquid crystal pixel unit 2. When scanning is performed from the first vertical scanning line to the Nth vertical scanning line by the vertical scanning driver circuit 12, video signals for one screen are accumulated in the hold capacitor unit 4 of each pixel.

Next, a control signal is output from the pixel transistor driver circuit 15 to the pixel transistor control signal line 16 during a blanking period of the video signal, and when the pixel transistor 3 is turned on, the control signal is stored in each hold capacitor section 4. Video signals for one screen are simultaneously written to the liquid crystal pixel unit 2. At this time, since the sample control transistor 5 of each pixel is in the off state, the video signals do not interfere with each other.

By driving so that video signals are written to all the pixels of the liquid crystal panel 1 at the same time, in the case of line inversion driving, the polarity of the video signals of the vertically adjacent lines becomes the same depending on the scanning timing. Can be prevented. Further, since the polarity of the video signal output to the scanning signal line and the polarity of the signal held by the liquid crystal pixel portion do not differ between the upper and lower portions of the screen, a leak current due to a potential difference between the two can be reduced.

As described above, by providing the sample and hold circuit in the liquid crystal panel and driving it so that the video signal is simultaneously written into the liquid crystal display unit, discontinuous portions where the polarity is inverted can be eliminated and the leak current can be reduced. Therefore, a great effect is obtained that uniformity on the display screen can be maintained and good display image quality can be obtained.

The liquid crystal panel used in the method for driving the liquid crystal display device of the present invention is a transmissive liquid crystal panel of a type that transmits an irradiation light from a light source to display an image by reflecting the irradiation light. Obviously, a reflective liquid crystal panel of a type for displaying an image may be used.

[0023]

As described above, according to the method of driving a liquid crystal display device of the present invention, an active matrix substrate in which pixel electrodes having at least one switching transistor are arranged in a matrix and a transparent electrode are provided. A method for driving a liquid crystal display device having a liquid crystal layer sandwiched between common electrode substrates, comprising: a sample and hold circuit for holding a video signal to be written to each of the pixel electrodes;
A switching transistor for writing a video signal to the pixel electrode, and holding the input video signal in a sample and hold circuit for each pixel electrode for one vertical scanning period of the liquid crystal display device; A liquid crystal display device that is configured to be driven so as to simultaneously write to all the pixel electrodes by the switching transistor during a certain period during the period to maintain uniformity on a display screen and obtain good display image quality. There is a great effect that it can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a liquid crystal display device according to a driving method of the liquid crystal display device according to the present invention.

FIG. 2 is a timing chart for explaining states of a gate pulse signal and a pixel transistor control signal in the present invention.

FIG. 3 is a configuration diagram of a conventional liquid crystal display device.

FIG. 4 is a timing chart showing a driving method of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Liquid crystal pixel part 3 Pixel transistor 4 Hold capacitor part 5 Sample control transistor 6 Common electrode power supply 11 Horizontal scanning driver circuit 12 Vertical scanning driver circuit 13 Video signal line 14 Scanning signal line 15 Pixel transistor driver circuit 16 Pixel transistor control signal Line 21 Video signal processing circuit 22 Synchronous signal separation circuit 23 LCD panel drive control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA16 NA34 NA43 NC23 NC34 NC35 NC40 ND15 5C006 AA01 AC28 AF42 BB16 BB28 BC03 BC12 BF11 EA01 FA22 FA23 FA36 5C080 AA10 BB05 DD05 DD06 EE17 FF11 JJ02 JJ04

Claims (3)

[Claims] 1. A driving method for a liquid crystal display device comprising a liquid crystal layer sandwiched between an active matrix substrate having pixel electrodes having at least one or more switching transistors arranged in a matrix and a common electrode substrate having transparent electrodes. Wherein a video signal is simultaneously written to all of the pixel electrodes during a certain period of time during one vertical scanning period of the liquid crystal display device. 2. A method for driving a liquid crystal display device comprising a liquid crystal layer sandwiched between an active matrix substrate having pixel electrodes having at least one or more switching transistors arranged in a matrix and a common electrode substrate having transparent electrodes. And a sample-and-hold circuit for holding a video signal to be written to each of the pixel electrodes, and a switching transistor for writing a video signal to the pixel electrodes. A liquid crystal display, wherein the liquid crystal is simultaneously written to all the pixel electrodes by the switching transistor during a certain period of one vertical scanning period after the sample and hold circuit holds the pixel electrodes for one vertical scanning period of the display device. A method for driving a display device. 3. The driving method for a liquid crystal display device according to claim 2, wherein the liquid crystal display device is a reflection type or transmission type liquid crystal display device.