JPH0594154A - Liquid crystal display panel device - Google Patents

Abstract

PURPOSE:To display an image specified by video data with high gradation on an active matrix type liquid crystal display panel device where picture elements are arranged in a matrix state by using a data driving circuit for comparatively low gradation. CONSTITUTION:This liquid crystal display panel device 30 is constituted by combining an active matrix type substrate 10 obtained by integrating a display driving element 12 executing a switching action every picture element and a counter substrate 20 provided with a display electrode 22 which is common to the picture elements arranged an a column direction. Then, the image data is divided to a pair of video data parts and loaded on a pair of data driving circuits 50 and 60. Besides, a display voltage from one of them is impressed on a data line 14 for the picture elements arranged in the column direction of the substrate 10 and the display voltage from the other is impressed on the display electrode 22 of the substrate 20. Then, the image specified by the video data is displayed on the liquid crystal display panel by the number of gradation which is equal to the product of the number of gradation which can be displayed by the respective driving circuits 50 and 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display panel device which performs gradation display based on video data on a display surface in which pixels are arranged in a matrix and which is particularly suitable for high gradation display.

[0002]

2. Description of the Related Art As is well known, a matrix type liquid crystal display panel device suitable for displaying a variable image in which a large number of pixels are arranged in a matrix on a display surface is an extremely thin and lightweight display device such as a television, a computer and an OA equipment. It has been adopted for a wide range of purposes. Liquid crystal display panel devices for computers and office automation equipment display digital video data, unlike those for displaying television images. At first, bright and dark display of characters and figures was the mainstream, but recently, complex images have been displayed. In order to display with high image quality, gradation display that can display not only light and dark but also intermediate tones is required. For high gradation display with 8 to 16 or more gradations, each pixel in the panel surface The active matrix type, which incorporates a display driving element for a display, becomes advantageous. The present invention relates to this active matrix type liquid crystal display panel device suitable for high gradation display, and as is well known, its outline will be briefly described below with reference to FIGS. 4 and 5.

FIG. 4 is a sectional view showing a conventional structure of an active matrix type liquid crystal display panel 30. As shown, the liquid crystal display panel 30 is a transparent glass plate or the like.
The pair of substrates 10 and 20 are closed at their peripheral portions by means of a sealing resin 31 or the like to enclose the liquid crystal 32 in the internal space, and the liquid crystal 32 is enclosed in the internal space. Polarizing films 33 and 34 are attached with their polarization directions orthogonal to each other.

One substrate 10 is on the active matrix side, a large number of pixel electrodes 11 are arranged in a matrix on the inner surface thereof, and a display drive element 12 is provided for each pixel. A portion of one pixel P in the liquid crystal display panel 30 of FIG. 5 is enlarged and shown. As shown in the figure, the pixel electrode 11 is a substantially rectangular transparent electrode, and the display drive element 12 is a field effect type thin film transistor, and it is common to the scanning lines 13 common to the pixels arranged in the left-right direction and the pixels arranged in the up-down direction. The data line 14 is provided on the one substrate 10 side, the gate of the display drive element 12 is connected to the former, the source is connected to the latter, and the drain is connected to the pixel electrode 11. On the other substrate 20 side, a transparent counter electrode 21 is provided in a large area pattern commonly to many pixels in the panel surface as shown by a thin line in FIG.

In the display circuit shown in FIG. 5, a liquid crystal display panel 30 is used.
The scanning lines 13 are sequentially driven by the scanning drive circuit 40 with the operation voltage SV synchronized with the scanning pulse SP, and in synchronization with the operation, the data lines 14 are supplied with the display voltage designated by the video data D from the data drive circuit 50. The pixels P arranged along the scanning line 13 are driven to be displayed by mounting DV all at once. In the case of gradation display, the video data D has a structure of a plurality of bits, for example, 4 bits, and the display voltage DV corresponding to the possible digital value of 0 to 15 is applied to each data line 14. The data circuit 70 applies the scan pulse SP to the scan drive circuit 40 and the like, and also applies the video data D to the data drive circuit 50 in synchronization with the clock pulse CP, so that one scan line 13 is included in one cycle of the scan pulse SP. Scan pulse after loading minute image data D
Display voltage DV is output all at once in synchronization with SP.

The counter electrode 21 on the other substrate 20 side is, for example, grounded as shown in the figure, and the above-mentioned display is applied from the data line 14 on the one substrate 10 side to the pixel electrode 11 via the display drive element 12. The display of the brightness according to the voltage DV is simultaneously performed on the pixels P along the scanning line 13, and this state is held within one frame period until the scanning line 13 is driven next time.

[0007]

As described above, the data line 14 of the active matrix type liquid crystal display panel 30 is supplied from the data driving circuit 50 to the display voltage DV corresponding to the video data D.
By driving with, it is possible to display a variable image having a gradation number corresponding to the number of constituent bits of the video data D with high image quality. There is a problem that the configuration of the semiconductor integrated circuit device for the drive circuit 50 becomes difficult and very expensive. This is because the accuracy of the DA conversion of the video data D to the display voltage DV is likely to decrease as the number of gradations increases.
It is required to integrate tens to hundreds and tens of pixels in each integrated circuit device, and a display voltage DV of 10 to 20V is required. The chip area is required, and it is difficult to achieve high integration. Therefore, the chip size increases substantially in proportion to the number of bits of the video data D.

As a means for solving this problem, a display method called a frame thinning method has been conventionally known. As is well known, this is a method in which a thinning frame for displaying only white or black or only light or dark is inserted for every plurality of frame periods on the display.
It is possible to obtain a grayscale display equivalent to increasing the number of bits, but it is necessary to increase the number of thinning frames to achieve a high grayscale, so there is a problem of flickering or flicker on the display, and practically 8 grayscale display is the limit. it is conceivable that.

For this reason, up to now, 16-bit display and 4 bits of video data are the highest, and 64-bit display of 6-bit video data is considered to be a practical limit in the future. At present, the difficulty in the configuration and the economical efficiency of the semiconductor device are a bottleneck in achieving high gradation of display. Under such circumstances, it is an object of the present invention to provide a liquid crystal display panel device which can easily display high gradation without using a high-grade or expensive integrated circuit device for a data driving circuit.

[0010]

According to the present invention, the object is to provide pixel electrodes arranged in a matrix on one substrate side of a liquid crystal display panel, a scanning line common to pixels arranged in one direction, and a scanning line. A display drive element for each pixel whose switching operation is controlled and a data line common to pixels arranged in the other direction are provided, and a display electrode is commonly provided to pixels arranged in the other direction on the other substrate side. This is achieved by dividing the bit-structured video data into two video data portions and applying a display voltage corresponding to each video data portion to the data line of one substrate and the display electrode of the other substrate, respectively.

It should be noted that the method of dividing the video data into the video data portion is arbitrary. For example, even-numbered bits or odd-numbered bits may be used. It is advantageous to divide the group into video data portions and apply display voltages corresponding to the video data portions on the upper bit side and the lower bit side to the data lines on one substrate side and the display electrodes on the other substrate side, respectively.

Further, the display driving element on one substrate side is preferably a three-terminal element, and this may be a thin film transistor similar to the conventional one, and its gate may be connected to the scanning line to control its switching operation. Further, it is purposeful that display voltages to be applied to the data lines on one substrate side and the display electrodes on the other substrate side, respectively, have polarities opposite to each other according to each video data portion.

[0013]

The present invention focuses on that the display brightness of each pixel of the liquid crystal display panel is determined by the voltage applied to the capacitor between the pixel electrode on one substrate side and the display electrode on the other substrate side.
By applying a display voltage to each of the pixel electrode and the display electrode and controlling the potentials of both electrodes independently of each other, the number of gradations equal to the product of the number of display gradations that can specify the voltage applied to the capacitor by each display voltage. Therefore, the display brightness of each pixel can be specified by a large number of gradations even if a data driving circuit for generating a display voltage having a relatively small number of gradations is used. .. For this reason, in the present invention, the video data is divided into a pair of video data portions as in the configuration of the preceding paragraph, and the display voltage corresponding to one of the video data portions is passed through the data line on one substrate side. The display voltage is applied to the pixel electrode and the display voltage corresponding to the other video data portion is applied to the display electrode on the other substrate side.

Further, in the present invention, in order to simplify the structure of the liquid crystal display panel as much as possible, the fact that the display drive element on one substrate side performs a switching operation is used to display on the other substrate side as described in the above constitution. Electrodes are commonly provided for pixels arranged in the other direction, that is, in the same direction as the data line on one substrate side. The potential of the display electrode naturally changes according to the display voltage which is sequentially switched in synchronism with the driving of the scanning line, but in order to bring a certain pixel into a predetermined display state, the display drive element of the pixel is turned on within a short time. When it is turned off, the pixel electrode becomes insulated, so even if the potential of the display electrode fluctuates, the potential of the pixel electrode changes accordingly, and the charging state of the capacitor does not change at all. Therefore, the initial display of the pixel The condition is kept stable.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 shows an embodiment of a liquid crystal display panel device according to the present invention together with a display circuit, FIG. 2 shows a structural example of the liquid crystal display panel in cross section, and FIG. 3 shows related main signal waveforms and display voltage distributions. Since the same reference numerals are given to the parts corresponding to those in FIG. 4 and the subsequent parts described above, the description of the overlapping parts will be appropriately omitted.

In FIG. 1, a pair of substrates 10 and 20 constituting a liquid crystal display panel device 30 are shown separately in an upper half portion and a lower half portion of the drawing for convenience of illustration. One of the substrates 10 is an active matrix type substrate, and a pixel electrode 11 made of a transparent conductive film for each of a number of pixels P arranged in a matrix on the surface thereof and a three-terminal element for switching operation. A certain display drive element 12 is provided, and a scanning line 13 and a data line 14 are commonly provided for the pixels P arranged in the left and right and up and down directions in the drawing. In this embodiment as well as in the conventional case, the display drive element
A thin film transistor is used for 12, and its gate is a scanning line 13, its source is a data line 14, and its drain is a pixel electrode 11
The switching operation is controlled by the scanning voltage SV which is connected to the respective gates and is received by the gate via the scanning line 13.

In the present invention, the display electrode 22 made of a transparent conductive film is provided on the other substrate 20 side in common with the pixels P arranged in the vertical direction in a stripe pattern as shown in the drawing. FIG. 2 shows a liquid crystal display panel 30 in which these substrates 10 and 20 are combined, in a section similar to that of FIG. The structure of the liquid crystal display panel device 30 of this embodiment is different from the conventional one in that a display electrode 22 having a narrow width is provided on the side of the other substrate 20 instead of the counter electrode 21 having a large area in FIG. Of course, the illumination light IL is given from the back side through the polarizing film 34 to display light of each pixel P.
The same applies to taking out DL from the surface side through the polarizing film 33. For the sake of convenience of explaining the procedure of high-gradation display by the liquid crystal display panel device 30 configured as described above, in this embodiment, the display is based on 8-bit video data D 256.
One board 10 in which the gradation and the image data D are 4 bits each
It is assumed that the image data portion D1 to the side and the image data portion D2 to the other substrate 20 side are divided.

The scan drive circuit 50 shown in FIG. 1 may be the same as the conventional one, and receives the scan pulse SP shown in FIG. 3 (a) from the data circuit 70 and outputs the scan voltage SV shown in FIG. 3 (c) or (d). Board 10
The scanning lines 13 on the side are sequentially driven. For example, the scan voltage SV in FIG. 3C is for the first scan line 13, and the scan voltage SV in FIG.
SV is for the second scan line 13. As can be easily understood, this operation drive circuit 50 is composed of, for example, a shift register,
The display driving elements 12 for the pixels P arranged along each scanning line 13 are simultaneously ON-controlled for a short time by the scanning voltage SV which is the output of the stage.

The data lines 14 on one substrate 10 and the other substrate 20
Data driving circuits 50 and 60 are respectively provided for driving the display electrodes 22 of FIG. 3 and the video data portions D1 and D2 of the above-mentioned 4-bit configuration obtained by dividing the video data D from the data circuit 70 are respectively shown in FIG. 3 (b). Scan line 13 received in synchronization with clock pulse CP
After the loading of the video data portions D1 and D2 for one pixel P, the display voltages DV1 and DV2 corresponding thereto are output in synchronization with the scanning pulse SP. The method of dividing the video data D into a pair of video data portions D1 and D2 is arbitrary in principle, but in this embodiment, the upper 4 bits of the video data D are the video data portion D1 and the lower 4 bits are the video data. part
Divided as D2.

The display voltage DV1 for the data line 14 by the data driving circuit 50 is shown in FIGS. 3 (e) and 3 (f). These show, for example, the distribution of the display voltage DV1 which is simultaneously applied to the plurality of data lines 14 in synchronization with the scanning voltage SV shown in FIGS. Of course, this distribution state usually takes a very complicated form depending on the contents of the video data D1, but for convenience of illustration, the distribution is shown as a simple shape consisting of gentle peaks and valleys. As described above, since the video data portion D1 has a 4-bit structure, the display voltage DV1 changes in 16 steps, and since the video data portion D1 is a high-order bit portion of the original video data D, the one substrate 10 side of this active matrix type is The display voltage DV1 to be given is set so that its stepwise change is large, for example, different by 1V, and as shown in the figure, from 0V
It is made to change within the range of V1 = 15V. In addition,
In Fig. 3 (e), the unit change of this display voltage DV1 for one gradation is shown.
Shown in V2.

3 (g) and 3 (h) show the distribution of the display voltage DV2 for the display electrode 22 on the other substrate 20 side by the data driving circuit 60 in the same manner as the above-mentioned display voltage DV1. Since the video data portion D2 received by the data driving circuit 60 is the lower 4 bits of the original video data D, it is the same that the display voltage DV2 changes in 16 steps, but the change for one step is much smaller and the maximum change is It is set equal to the above-mentioned unit change V2 of the display voltage DV1. In addition, this display voltage is
The change of DV2 is shown in a larger scale than the case of the display voltage DV1. It is the same that the display voltage DV2 having the distributions shown in FIGS. 3 (g) and 3 (h) is generated in synchronization with the scanning voltage SV shown in FIGS. 3 (c) and 3 (d), respectively. Are simultaneously applied to a large number of display electrodes 22 on the other substrate 20 side.

Further, in this embodiment, the display voltage DV2 is generated with the opposite polarity to the display voltage DV1 as shown in the figure, and the sum of the two display voltages is the pixel electrode 11 on the one substrate 10 side and the other substrate 20.
So that it hangs between the display electrode 22 on the side. Note that FIG.
The distribution of the display voltage DV2 in (g) and (h) shows the case where the distribution of the original video data part D2 is all the same as that of the video data part D1, and the polarity is opposite to that of the display voltage DV1, as shown in the figure. The peaks and valleys in Figures (e) and (f) are just opposite.

In this way, the liquid crystal display panel device 30 and the display circuit are configured, and both of them are provided with the data driving circuit 50 for displaying 16 gradations.
And 60 to synchronize the operation of the scan drive circuit 40 with one board
By independently driving the data line 14 on the 10 side and the display electrode 22 on the side of the other substrate 20, it is easy to see that the liquid crystal display panel device 30 has 256 levels specified by the video data D of 8 bit configuration. High gradation display can be performed. The data driving circuits 50 and 60 may be of conventional performance, and the liquid crystal display panel device 30 may be the other active matrix type substrate 20 of the conventional type.
Since it suffices to form the display electrode 22 on the side in an elongated pattern common to the pixels P arranged in the direction along the data line 14, it is possible to easily realize a high gradation display with a minimum cost increase. Of course, the data driving circuits 50 and 60 are not limited to those for 16 gradations. If both or one of them is used for 8 gradations, high gradation display of 64 or 128 steps can be performed.

When the display electrode 22 on the other substrate 10 side is provided in common to the pixels P arranged in the same direction as the data line 14 as described above, the potential is switched in synchronization with the driving of the scanning line 13. Although it changes according to the voltage DV2, when the display driving element 12 is turned off after the certain pixel P enters the display state as described above, the pixel electrode 11 is substantially in the insulating state, and thus the display electrode which is the counter electrode. Even if the potential of 22 fluctuates, the charge state of the capacitor, that is, the voltage applied between the two opposite electrodes does not change, and the display state of the pixel P is stably maintained during one frame period when the scan voltage SV is received next. It

However, since the display driving element 12 such as a thin film transistor is not a complete switching element and has a high resistance in the off state but a finite off resistance, the display electrode
When the potential of 22 fluctuates, the display state of the pixel P may be slightly affected. To prevent this, it is preferable to reduce the potential fluctuation of the display electrode. Therefore, as described above, the upper bit group and the lower bit group of the video data D are divided into the video data portions D1 and D2, respectively, and according to the video data portion D1. The display voltage DV1 having a larger change is applied to the data line 14 of one substrate 10 and the display voltage V2 having a smaller change corresponding to the image data D2 is applied to the display electrode 22 of the other substrate 20 to improve the image quality. It is desirable to raise it. When the display drive element 12 has good switching characteristics or when the image quality is not so important, for example, if the video data portions D1 and D2 are divided according to whether the video data D is an even-numbered bit or an odd-numbered bit, the data driving circuit 50 You can use 60 for the same voltage.

[0026]

As described above, according to the present invention, the pixel electrodes arranged in a matrix on one substrate side, the scanning lines common to the pixels arranged in one direction, and the display for each pixel whose switching operation is controlled by the scanning lines. A drive element and a data line common to the pixels lined up in the other direction are provided, and a display electrode is commonly provided to the pixels lined up in the other direction on the side of the other substrate to display two video data of a multi-bit configuration in gradation display. By dividing into the data portion and applying the display voltage corresponding to each video data portion to the data line of one substrate and the display electrode of the other substrate, respectively,
The following effects can be obtained.

(A) A pixel electrode on one substrate side and a display electrode on the other substrate side are respectively supplied with a display voltage according to a video data portion to control the potentials independently of each other, so that a capacitor between the two electrodes is formed. Since the applied voltage can be controlled by the number of gradations equal to the product of the number of display gradations that can be specified by each display voltage, the display panel can be used while using a data driving circuit that generates each display voltage with a relatively small number of gradations. The display of the device can have higher gradation than ever. (b) By using the display drive element on one substrate side to perform the switching operation, the display electrode on the other substrate side is provided in common to the pixels lined up in the same direction as the data line on the one substrate side. High-gradation display is possible with the liquid crystal display panel device having various configurations, and the high-gradation display state of the pixel is stably maintained even if the potential of the display electrode is changed due to the switching of the drive to the operation line, and the image quality is improved. You can (c) If the high-order bit group and the low-order bit group of the video data are separated as the video data portion, the data for generating a low display voltage according to the video data portion on the low-order bit side while improving the image quality of high gradation display The breakdown voltage of the integrated circuit device for the drive circuit can be lowered and the cost can be reduced. As described above, the present invention makes it possible to economically eliminate the bottleneck of the related art in increasing the gradation of the display of the liquid crystal display panel device.

[Brief description of drawings]

FIG. 1 is a configuration circuit diagram showing an embodiment of a liquid crystal display panel device according to the present invention together with a display circuit.

FIG. 2 is a cross-sectional view showing a structural example of a liquid crystal display panel device according to the present invention.

3A and 3B show main signal waveforms and display voltage distributions related to the embodiment of FIG. 1, where FIG. 3A is a scan pulse waveform diagram, FIG. 3B is a clock pulse waveform diagram, and FIG. Figures (c) and (d) show the waveforms of the scanning voltage, (e) and (f) show the distribution of the display voltage applied to the data line, and (g) and (h) show the display electrodes. It is a distribution diagram of a given display voltage.

FIG. 4 is a cross-sectional view showing a structure of a conventional liquid crystal display panel.

FIG. 5 is a configuration circuit diagram showing a conventional liquid crystal display panel together with a display circuit.

[Explanation of symbols]

 10 One substrate 11 Pixel electrode 12 Display drive element 13 Scan line 14 Data line 20 Other substrate 22 Display electrode 30 Liquid crystal display panel device 40 Scan drive circuit 50 Data drive circuit for one substrate 60 Data drive for the other substrate Circuit 70 Data circuit for video data CP Clock pulse for loading video data D Video data D1 Video data part D2 Video data part P pixel DV1 Display voltage for one board DV2 Display voltage for the other board SP Scan pulse SV scan Scan voltage for line

Claims (5)

[Claims] 1. An active matrix type liquid crystal display panel device for performing gradation display based on video data on a display surface in which pixels are arranged in rows and columns, and pixel electrodes arranged in rows and columns on one substrate side of the display panel. , A scanning line commonly provided to pixels lined up in one direction, a display driving element provided for each pixel, and a switching operation of which is controlled by the scanning line,
Data lines commonly provided to pixels lined up in the other direction and display electrodes commonly provided to pixels lined up in the other direction on the other substrate side. A liquid crystal display panel device characterized in that a display voltage according to each video data portion is divided into portions and applied to a data line on one substrate side and a display electrode on the other substrate side, respectively. 2. The device according to claim 1, wherein a high-order bit group and a low-order bit group of the video data are divided into two video data parts, and a display voltage corresponding to the video data parts on the high-order bit side and the low-order bit side. A liquid crystal display panel device, characterized in that each is provided to a data line and a display electrode. 3. A liquid crystal display panel device according to claim 1, wherein display voltages having opposite polarities are applied to the data lines and the display electrodes. 4. A liquid crystal display panel device according to claim 1, wherein the display driving element is a three-terminal element. 5. The liquid crystal display panel device according to claim 1, wherein the display driving element is a thin film transistor whose switching operation is controlled by a gate connected to a scanning line.