JPH10161086A - Driving circuit for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display panel whose display quality is excellent even in an active matrix type liquid crystal display panel using non- single crystal transistors, especially in a panel in which peripheral driving circuits are an integrated type. SOLUTION: This driver is connected to scanning lines in which gate electrodes of thin film transistors whose sources electrodes or drain electrodes are connected to a pixel display line are different in thin film transistors for every adjacent pixel display line and also transmits a pixel signal arranged in up and down directions or in left and right directions to a liquid crystal panel. In this case, a signal to be time sequentially transmitted can be correctly transmitted to the liquid crystal panel by allowing the number of existing latches to be changed by one piece in the up and down directions or in the left and right directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the formation of a driving circuit for a liquid crystal display device, and more particularly, the driving circuit is integrated with a thin film transistor (TFT) using a non-single-crystal material for switching pixels inside a panel. The present invention relates to a configuration of a driver built-in type active matrix liquid crystal panel formed by the above method.

[0002]

2. Description of the Related Art A display using an active matrix type display substrate using TFTs has been intensively studied because higher image quality can be obtained as compared with a simple matrix type display device.

FIG. 3 is a perspective view schematically showing a liquid crystal panel of a conventional active matrix type liquid crystal display device.

In FIG. 3, reference numeral 104 denotes a scanning line (gate bus), 105 denotes a data line (source electrode or drain electrode), 106 denotes a source electrode (106s) or a drain electrode (106d) and a gate electrode (106g). 3 shows a pixel electrode 103 for driving a liquid crystal, which is electrically connected to the pixel electrode 103. Here, the TFT portion is the portion 106. In a normal transmission type liquid crystal display device, since it is necessary to transmit light from a back light source, the pixel electrode must be a transparent conductive film. The above elements are formed by repeating thin film formation and selective etching on the substrate 101 on the array side. Reference numeral 107 denotes a transparent conductive film serving as a counter electrode. When color display is performed on the liquid crystal panel, display can be performed by forming a color filter on each pixel of the counter substrate 102.

In such a liquid crystal panel, when a TFT is driven according to an image signal to change the voltage applied to the liquid crystal layer, the transmittance of the liquid crystal panel changes accordingly to display an image. . Here, as a material of the TFT, a-Si, poly-Si having high mobility and Cd
A material such as Se is used. When a TFT is formed of a material having high mobility, such as poly-Si or CdSe,
At the same time as the step of forming the TFT, peripheral drive circuits can be formed integrally.

In general, as a digital driving circuit for driving a liquid crystal panel, when signals of three primary colors of R, G, and B sent from the device side are digital signals, an analog video signal is not changed. In this case, digital signals (DR (1) to DR (n), DG (1) to DG
(N), DB (1) to DB (n): n is the number of bits), and after performing digital signal processing, frequency-divided into upper and lower or left and right, and each time-series digital data Is sampled for one line by the shift register operation, and is held in the first latch connected thereto, and at the same time, a latch pulse is generated during the horizontal blanking period. The liquid crystal panel is driven by a video signal that has been converted to analog by conversion (D / A conversion). These are shown in general blocks in FIG. FIG. 5 shows a timing chart of the clock, data, and latch pulse.

On the other hand, as a method of driving a liquid crystal panel in which the signal amplitude is reduced and the potential of the counter electrode is kept constant, a storage capacitor connected to the liquid crystal cell is provided between the preceding scanning electrode and one after the scanning signal. A method of applying a compensation voltage during a horizontal scanning period has been proposed (for example, Japanese Patent Application Laid-Open No.
No. 57815). As a result, low-voltage driving becomes possible, and it is not necessary to drive a counter electrode having a large capacitance, so that the power consumption of the liquid crystal panel can be reduced. However, in this method, the polarities of the vertically adjacent pixels are inverted, but the polarities of the horizontally adjacent pixels are the same.

When the polarities on the horizontal scanning lines are the same, the display area of the liquid crystal panel increases, and white and
Alternatively, when a black pattern is displayed, crosstalk occurs in the horizontal direction along this display pattern (see FIG. 6,
AMLCD94, p228).

In FIG. 6, a region A is a case where halftone display is performed, and a region B is a case where white display is performed. Horizontal crosstalk occurs in a portion indicated by an arrow. The cause of this phenomenon is that the polarity of the image signals written at the same time is the same, so that as the panel becomes larger and the resistance of the counter electrode increases, the potential of the counter electrode changes in one horizontal scanning period. It is known that it occurs by receiving. Therefore, as an effective means for preventing this phenomenon, it is effective to invert the polarities of pixels simultaneously written by the scanning signal.

As a driving method corresponding to this, in a pixel configuration, as shown in FIG. 7, a configuration in which gate electrodes of thin film transistors adjacent in the horizontal direction are connected to different scanning signal lines can be considered. By adopting this configuration and superimposing an additional pulse before and after the scanning signal, it is possible to invert the polarity of a pixel in one horizontal period and at the same time invert the polarity of a horizontally adjacent pixel. FIG. 8 shows this driving waveform. In this case, the pixels connected to the odd-numbered image display lines are supplied with the compensation voltage Vea (−) or Vea (+) added to the next-stage scanning signal Vg.
, And the pixels connected to the even-numbered image display lines receive the compensation voltage Veb (−) or Ve added to the preceding scanning signal Vg.
The signal is modulated by the storage capacitor Csb by b (+).
Pixels written at the same time are pixels A and B in FIG.
Therefore, since images of different polarities are simultaneously written to the counter electrode, an image without crosstalk can be displayed.

[0011]

According to the above technique, the signal amplitude is reduced, but the following problems exist.

That is, since the gate lines of the TFTs connected to the pixels adjacent in the horizontal direction are shifted back and forth, even in the case of a signal for displaying a horizontal straight line, for example, a rattling signal is displayed. In FIG. 9, signals displayed simultaneously are, for example, R11 and G in the first column.
11, B11 and R21, G21, B21 ... Rn1, G
n1 and Bn1.

Therefore, a signal that should be displayed as a horizontal line is displayed with a shift of one pixel for every one dot in the horizontal direction. In particular, this problem is caused by a display display for a personal computer, which often displays a still image or the like. Is a fatal problem for us.

[0014]

Therefore, a liquid crystal display device driving circuit according to the present invention is connected to each stage of a shift register for transferring image data, and the shift register holds the transferred image data. It is formed of a group of latches, and the number of the latches in the group of latches differs by one step in the vertical and horizontal directions of the display panel. Generally, it is sufficient that the number of latches is the necessary minimum and one is two stages and one is three stages.

Further, the effect is further emphasized in terms of cost by forming the driving circuit from a material having high mobility represented by polysilicon or CdSe formed on a glass substrate.

By adopting the above configuration, for example, one extra latch is provided on the side of the peripheral drive circuit that drives the source electrode of the TFT connected to the pixel which is earlier in time by one horizontal scanning period as an image signal. By providing
The timing for outputting the image signal can be shifted by one horizontal scanning period.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device driving circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a driving circuit for a liquid crystal display device according to an embodiment of the present invention.

In FIG. 1, 1 is an A / D converter, 2 is a horizontal scanning shift register, 3 is a latch circuit for retaining data, 4 is a thin film transistor element for driving pixels, and 5 is a column signal electrode. , 6 are row scanning electrodes, 7 is a liquid crystal cell as a display element, 8 is a vertical scanning shift register, 9
Indicates a display panel. The portions surrounded by the dotted lines are the driver A disposed at the upper part of the panel connected to the odd-numbered image signal wiring and the driver B located at the lower part of the panel connected to the even-numbered image signal wiring. The driver A has a three-stage latch configuration compared to the conventional two-stage latch, whereas the driver B has a two-stage latch similarly to the conventional driver configuration.

By adopting such a configuration as upper and lower drivers, pixels connected to odd-numbered image signal lines are latched one stage with respect to pixels connected to even-numbered image signal lines. Because the number of times increases,
Data is displayed with a delay of one horizontal scanning period. Therefore, the above-described phenomenon in which the image signal wiring is vertically shifted by one dot between adjacent image signal wirings is solved.

FIG. 2 shows a display pattern of the pixels connected to each image signal line in this case. In FIG. 2, R1
1, G11, B11 and R21, G21, B21 ... Rn
R11, B11, G21,... Gn1 connected to odd-numbered image signal lines among pixels of 1, Gn1, Bn1
Is displayed later than the even-numbered lines by one horizontal period, so that it was conventionally possible to avoid a phenomenon in which display signals adjacent to the left and right are shifted by one dot. In addition,
In this case, the timing chart of the latch pulse, data, clock, and the like sent to the upper and lower drivers is the same as the conventional one.

When the above driving circuit is externally mounted as a peripheral driver of a liquid crystal panel, it is necessary to change the internal configuration of the drivers mounted on the upper and lower sides, and two types of image signal drivers can be mounted on one liquid crystal panel. Since it becomes necessary, it causes a cost increase. Therefore, in the process of forming the switching elements inside the panel using polysilicon for the upper and lower drivers, peripheral drivers were created at the same time. In this case, the cost does not increase even if the configuration of the drivers existing above and below is different.

In this embodiment, the case where the driving circuits for the image signals are arranged above and below the liquid crystal panel has been described. However, the same effect can be obtained even when the driving circuits are arranged on the left and right sides of the panel. It is. Further, in the present embodiment, the number of latches of the upper and lower drivers is two and three. However, it is needless to say that the same effect can be obtained by shifting one between the upper and lower (left and right) drivers. Further, it is possible to use CdSe having high mobility in addition to polysilicon as a material for forming the driver.

[0024]

As described above, the polarity of adjacent pixels is inverted by driving the latch group included in the driving circuit so that the number of the latches differs by one stage in the vertical and horizontal directions of the display panel. In addition, it has become possible to produce a liquid crystal display panel having excellent display quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a drive circuit for a liquid crystal display device of the present invention.

FIG. 2 is a timing chart of a driving circuit for a liquid crystal display device of the present invention.

FIG. 3 is a perspective view of a conventional active matrix liquid crystal panel.

FIG. 4 is a configuration diagram of a driving circuit for an image signal used in a conventional active matrix liquid crystal display panel.

FIG. 5 is a timing chart of a driving circuit for an image signal used in a conventional active matrix liquid crystal display panel.

FIG. 6 is a diagram showing horizontal crosstalk.

FIG. 7 is a configuration diagram of an active matrix liquid crystal panel having a structure in which a scanning line to which a gate electrode of a TFT is connected is switched for each image signal in which an array of TFTs connected to a pixel is adjacent to each other;

FIG. 8 is a diagram showing a driving waveform of a scanning-side electrode.

FIG. 9 is a diagram showing that the display of horizontally adjacent pixels is shifted by one dot in the conventional driver configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Substrate 102 Counter substrate 103 Pixel electrode 104 Scanning line 105 Data line 106 TFT part 107 Transparent conductive film

Claims (2)

[Claims] 1. A driving circuit for a liquid crystal display device having a switching element comprising a thin film transistor arranged in a matrix and a pixel comprising a liquid crystal display element, wherein a source electrode or a drain electrode is connected to an image display line. A gate electrode of the thin film transistor is connected to a different scanning line by a thin film transistor for each adjacent image display line, and is connected to each stage of a shift register for transferring image data, and digital data sampled by the shift register is connected to one stage. A latch group for holding a horizontal period is formed, and the number of the latch groups included in the driving circuit is different by one stage at the top and bottom or left and right of the display panel. circuit. 2. The liquid crystal display device driving circuit according to claim 1, wherein the number of latches of the liquid crystal driving circuit arranged vertically is one in two stages and the other is in three stages.