JPH0548056A - Method for driving liquid crystal display device - Google Patents

Abstract

PURPOSE:To normalize the facial average display among picture elements where the leak pass occurs and prevent the picture element fault so as to improve the yield by devising the polarity arrangement for writing data. CONSTITUTION:The title device has many picture elements arranged in the data line direction and scanning line direction and the voltage written corresponding to respective display gradations of the elements according to the specified display cycle, and it accumulates the written voltage in the picture element capacity. In the device, two picture elements for writing voltage with same polarity are arranged along the data line direction and/or scanning line, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device, and more particularly to a method for driving an active matrix type liquid crystal display device. Generally, as a display device of a portable computer called a laptop type or a book type type, a thin type, a light weight type, and a low power type such as a liquid crystal display device are used.

Among the liquid crystal display devices, the active matrix type liquid crystal is capable of multi-gradation display, and even when high definition display is performed, a reduction in contrast and a viewing angle without causing a reduction in drive duty ratio. It has excellent features such as no reduction, and can obtain color coloring and display quality comparable to that of a cathode ray tube (CRT), and its application is expanding as a thin flat display.

[0003]

2. Description of the Related Art FIG. 5 is a diagram showing an active matrix type liquid crystal display device. Two glass substrates 1 facing each other are shown.
The liquid crystal layer 12 is sandwiched between 0 and 11. On the upper glass substrate 10, n (n = 6 in the figure) scan lines i _{1 to} i ₆ and m (m = 7 in the figure) data lines j _{1 to} j ₇ are formed in a grid pattern. Pixels (represented by squares) are connected to each point of the grid.

FIG. 6 shows an equivalent circuit of one pixel, which is a pixel located at coordinates (i _x , j _y ). i _x th thin film transistor TF having a gate electrode connected to the scan lines
T _xy is built into the liquid crystal layer 12. Further TFT _xy
The liquid crystal C _xy is formed between the pixel electrode connected to the j _y -th data line via the common electrode G and the common electrode G formed on the lower glass substrate 11.

[0005] In such a configuration, to turn on the TFT _xy Select i _x th scan line, j
_When the display data d _y of an arbitrary voltage (for example, V _A ) is applied to the _y- th data line, this data d _y is written to the liquid crystal C _xy via the TFT _xy, and is written (refreshed) until new data is written. Held). As a result, the liquid crystal C _xy has a transmittance according to the magnitude of the holding voltage ( _VA ) and keeps the transmittance until refreshed.

Generally, if the voltage waveform written in the liquid crystal is positive and negative symmetrical, the light passing through the liquid crystal display does not fluctuate with time and flicker does not occur. However, in the actual liquid crystal, the transmissivity is not always symmetrical with respect to the positive and negative data voltages. For this reason, a difference in transmittance occurs and flicker appears. Therefore, in order to suppress such flicker, conventionally, a driving method in which the polarity of the data voltage is made different for each column of data lines is adopted. Further, in order to improve the reliability of the liquid crystal, the polarity is switched between the odd frame and the even frame. FIG. 7 is a diagram showing changes in the voltage polarities of the pixel electrodes due to such a driving method. In the figure, white circles (◯) are pixels in which a data voltage that becomes a positive voltage is written to the common electrode, and black circles (●) are pixels in which a data voltage that becomes a negative voltage is written.

In this way, since the luminance change is averaged over the surface and the time, the flicker becomes difficult to see.

[0008]

However, in such a conventional driving method for a liquid crystal display device, since the data voltages of adjacent pixels are arranged in opposite polarities, for example,
When a leak path is generated between adjacent pixels, there is a problem that the data voltages of opposite polarities influence each other through the path and normal display cannot be performed.

FIG. 8 is an equivalent circuit including a pair of adjacent pixels X and Y having a leak path. The following two leak paths are known. One is a path (hereinafter referred to as “leak path A”) formed by dust-like substances adhering between the pixel electrodes, and the other is a capacitance due to a gate insulating film between the glass substrate and the pixel electrode. And a remaining conductive material on the surface of the glass substrate (hereinafter referred to as a leak path B). The residual conductive material is a residual conductive material after forming a scan line on the glass substrate surface, and is a residual conductive material such as titanium or aluminum film sputter-deposited on the glass substrate surface.

Now, consider the case where a positive (+) data voltage is written to the common electrode in the liquid crystal capacitance of the pixel X. According to the conventional driving method, the opposite polarity data voltage (−) is written in the liquid crystal capacitance of the adjacent pixel Y. The two data voltages having different polarities are connected via the leak paths A and B, and if the magnitudes of the data voltages are the same, for example, the positive and negative are canceled, and as a result, the charge held in the liquid crystal capacitances of the pixel X and the pixel Y is canceled. Becomes equivalent to the potential of the common electrode (approximately 0 V), and normal display can no longer be expected. Such a leak path is apt to occur during the manufacture of a high-definition liquid crystal display device having a particularly large number of pixels, which is one of the factors that deteriorate the yield.

Therefore, an object of the present invention is to improve the yield by devising the polarity arrangement of the write data to normalize the display between pixels in which a leak path has occurred by surface averaging, to remedy pixel failures. To do.

[0012]

In order to achieve the above-mentioned object, the present invention arranges a large number of pixels in the data line direction and the scan line direction, and displays a gradation in each of the pixels according to a predetermined display cycle. In a liquid crystal driving device that writes a voltage according to the voltage and accumulates the written voltage in a pixel capacitance, writing voltages of the same polarity are arranged every two pixels along the data line direction and / or the scan line direction. And

[0013]

In the present invention, two pixels (for convenience, pixel a _-1 , pixel a for convenience) which are adjacent to both sides of one pixel (for convenience, pixel a) are provided.
₊₁ ) The data voltage of the same polarity is written in one side and the data voltage of the opposite polarity is written in the other side. Therefore, when a leak path occurs between the pixels, one of the two pixels adjacent to a certain pixel has the same polarity and the other has the opposite polarity. Therefore, the conventional example (the two pixels have opposite polarities). The effect of the leak path is halved as compared with the case of (polarity), and the display is salvaged.

[0014]

Embodiments of the present invention will now be described with reference to the drawings.
To do. 1 to 4 are driving methods of a liquid crystal display device according to the present invention.
It is a figure which shows one Example of a method. In Fig. 1, each frame
For convenience, 9 data lines j₁~ J₉And love
Online i₁~ I₉It is assumed to be composed of. You
That is, 9 × 9 / frame, 81 pixels / frame
Becomes The display order is n frames and n + 1 frames.
Frame, n + 2 frame, n + 3 frame ... Na
Note that here, for the sake of simplification of explanation, sequential scanning is taken as an example.
However, interlaced scanning may be used. Inter
In the case of race scan, scan lines of odd frames
i₁, I₃, I _Five, I₇, I₉And even frame scan
Online₂, I_Four, I₆, I₈And On each frame
The data line array direction (hereinafter, data line
Direction), there are two white circle (○) or black circle (●) pixels
They are lined up one by one. The white circle is, for example, positive for the common electrode.
A pixel that has a data voltage written to it
On the contrary, the black circle indicates that a negative voltage is applied to the common electrode.
It is a pixel in which such a data voltage is written.

Such regularity of the pixel arrangement is also recognized in the arrangement direction of scan lines (hereinafter, scan line direction). That is, two white circles or two black circles are arranged in the scan line direction. FIG. 2 is an extraction diagram of one pixel and four pixels adjacent to the pixel in an arbitrary frame. Here, the pixel located at the coordinate (i _3, j ₄ ) of the n + 3 frame and the pixel 4 adjacent to the pixel
Two coordinates (i _3, j ₃ ) (i _2, j ₄ ) (i _3, j ₅ ) (i
Each pixel located at _4, j ₄ ) is taken as an example. Hereinafter, the coordinates will be referred to as pixel numbers.

Three pixels (i _{3,
j 3) (i 3, j4} ) (i 3, j 5) is a single middle black circle is a two neighboring the white circle black circle. That is, data of the same polarity is written in one of the pixels (i _3, j ₃ ) (i _3, j ₅ ) on both sides, and data of the opposite polarity is written in the other. Similarly, three pixels (i _2, j ₄ ) arranged in the scan line direction
_{(I 3, j4) (i} 4, j 4) is a single middle black circle is a two neighboring the white circle black circle. That is, the data of the same polarity is written in one of the pixels (i _2, j ₄ ) (i _4, j ₄ ) on both sides, and the data of the opposite polarity is written in the other. Here, consider a case where a leak path is generated between pixels (i _3, j ₄ ) (i _3, j ₅ ) in the data line direction. Both of these pixels are black circles. That is, data of the same polarity is written. Therefore, the potential difference between pixels becomes small (almost 0 V for the same gradation), the adverse effect of the leak path can be avoided, and the display can be salvaged. This is because the write voltages of the same polarity are arranged every two pixels along the data line direction.

Consider also a case where a leak path is generated between pixels (i _3, j ₄ ) (i _4, j ₄ ) in the scan line direction. These pixels are also black circles as in the above example, and the data of the same polarity are written therein. Therefore, also in this case, the potential difference between the pixels becomes small (almost 0 V for the same gradation), the adverse effect of the leak path can be avoided, and the display can be salvaged. This is because the write voltages of the same polarity are arranged every two pixels along the scan line direction.

By the way, the pixel (i _3,
If a leak path occurs between j ₃ ) (i _3, j ₄ ) or between pixels (i _2, j ₄ ) (i _3, j ₄ ) in the scan line direction, the above-mentioned display rescue effect is I can't get it. This is because the white circles and the black circles are lined up to form a write data array with opposite polarities. On the other hand, in the present invention, two pixels (pixels (i _2, j ₄ ), (i _4, j ₄ )) adjacent to both sides of one pixel (for example, pixel (i _3, j ₄ )) A data voltage of the same polarity is written in one (i _4, j ₄ ) and a data voltage of the opposite polarity is written in the other (i _2, j ₄ ). Therefore, when a leak path occurs between pixels, one of two pixels adjacent to any one pixel has the same polarity and the other has the opposite polarity. However, the influence of the leak path is halved, and the display is relieved.

In the above embodiment, the present invention is applied to both the data line direction and the scan line direction, but it may be applied to either one. Further, in the above embodiment, the pixel array in the data line direction (white circles,
The arrangement of black circles) is shifted by one pixel for each frame.
FIG. 3 is a conceptual diagram thereof, in which pixels arranged in the order of white, white, black, and black in n frames are black in n + 1 frames.
The order is white, white, and black. In the n + 2 frame, black, black,
It shifts to the right one pixel at a time in the order of white, white, and so on.

The present invention is not limited to this. For example, one pixel may be shifted to the left as shown in FIG. 4 (a), or two pixels as shown in FIG. 4 (b). You may shift right or left one by one. From the viewpoint of reducing flicker, the driving method of FIG. 4B is preferable. This is because the other method is to drive the same pixel positively and negatively for every two frames.

[0021]

According to the present invention, since the polarity arrangement of the write data is devised, the display between the pixels having the leak path can be normalized by the surface average, and the pixel failure can be relieved to improve the yield.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an entire pixel array according to an embodiment.

FIG. 2 is a conceptual diagram of a pixel array of an essential part of one embodiment.

FIG. 3 is a conceptual diagram of a pixel array for each frame according to an embodiment.

FIG. 4 is a conceptual diagram of a pixel array for each frame of another example.

FIG. 5 is a liquid crystal panel diagram of a conventional example.

FIG. 6 is an equivalent circuit diagram of a pixel of a conventional example.

FIG. 7 is a conceptual diagram of a pixel array for each frame of a conventional example.

FIG. 8 is an equivalent circuit diagram of two pixels in which a leak path is generated in a conventional example.

[Explanation of symbols]

i ₁ through i _9: scanline j ₁ to j _9: Data line _{(i 3, j 3) (} i 2, j 4) (i 3, j 5) (i 4, j 4): coordinates (pixels)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Takahara 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (1)

[Claims] 1. A plurality of pixels are arranged in a data line direction and a scan line direction, a voltage according to a display gradation is written to each of the pixels according to a predetermined display cycle, and the written voltage is stored in a pixel capacitor. In the liquid crystal driving device, the driving method is characterized in that write voltages of the same polarity are arranged every two pixels along the data line direction and / or the scan line direction.