JPS58172685A - Liquid crystal display body device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device. Furthermore, the present invention relates to a liquid crystal display device using an active matrix substrate as one substrate.

In recent years, with the rapid development of the information society, combiators
The current situation is that the market for various peripheral mW and personal combinators is becoming more and more popular. Under these circumstances, although ORT has an overwhelming market share in display devices, development of flat display devices that can replace ORT is also becoming more and more popular. Among flat display devices, liquid crystal display devices can be driven at low voltage and low power, and are already widely used as light-receiving, easy-to-read displays in watches, 'WL4, etc., and will continue to be used in home appliances, automobiles, etc. It is thought that the market for this type of display will continue to expand.

Furthermore, in liquid crystal display devices, an active matrix substrate is used as one of the substrates, and by selecting the display of each pixel using an external signal, it is possible to display several hundred or more lines, and therefore it is possible to display images. Is possible. Being able to display images on a liquid crystal display device means that a small and portable television receiver can be made, and a large market is expected for this in the future as information transmission through text broadcasting and the like is promoted.

FIG. 1 is a cross-sectional structural diagram of a liquid crystal display device using an active matrix substrate in which silicon thin film transistors are formed on a transparent substrate. In FIG. 1, 1 is a transparent glass substrate, 2 is a channel portion of a thin film transistor, 3 is a source region, 4 is a gate electrode, a pole, 5 is an insulating film, and 6 is a metal wiring. 7 is a liquid crystal drive electrode made of a transparent conductive film such as tin oxide or indium oxide. 8 is a liquid crystal layer, 9 is an upper glass substrate, and 10 is a liquid crystal drive electrode formed on the entire surface of the upper glass substrate. 11 and 12 are polarizing plates 1, 11 and 13 are reflecting plates. The area indicated by P in the figure corresponds to one pixel. This panel is an 'I'M (twisted nematic) panel that uses two polarizing plates because the upper and lower substrates are transparent.
This is a type of LCD panel. FIG. 2 shows a pixel circuit corresponding to one pixel. In the figure, 14 is a data signal line, and 15 is a gate signal line. 16 is a switching transistor, 17 is a liquid crystal drive electrode indicated by 7 in FIG. 1, 18 is a liquid crystal layer, and 19 is a counter electrode indicated by 10 in FIG. When displaying an image on this panel, the image signal sent from the data signal line is temporarily stored in the capacitance of the liquid crystal layer by turning on the switching transistor, and the liquid crystal is driven until the next signal is input. It is executed in this mode.

FIG. 3 shows a plan view of a pattern for one pixel on an active matrix substrate. Numbers 14 to 17 in the diagram are second
They correspond to the numbers in the figure. As is clear from the figure, in the conventional plan view, the gate signal line 15 and the liquid crystal drive electrode 17, or the data signal line 14 and the liquid crystal drive electrode 17, do not overlap but are separated from each other in a plane.

When the gate signal line and the liquid crystal drive electrode are separated in this way, the voltage applied between the gate signal line and the counter electrode is different from the voltage applied between the liquid crystal drive electrode and the counter electrode. Therefore, a liquid crystal domain is generated between the gate signal line pattern and the liquid crystal drive electrode pattern. In other words, since the area on the gate signal line does not contribute to display at all, the contrast deteriorates and the display quality is significantly impaired. An explanatory diagram of the alignment state of liquid crystal molecules in such a case is shown in FIG. Here, the gate signal line
Assuming that the voltage applied to the data signal line is VO and the voltage applied to the data signal line is VD, as shown in FIG. It is assumed that the data voltage VD is applied in an alternating current manner at a frame period centering on yoo. FIG. 4 shows the alignment state of liquid crystal molecules in the AA cross section of FIG. If the liquid crystal molecules are aligned horizontally in advance, the liquid crystal on the gate signal line will be aligned vertically even if a data voltage is applied between the gate signal line and the counter electrode and the liquid crystal molecules are aligned vertically. The molecules maintain horizontal alignment, and liquid crystal domains as shown by the broken line 21 in FIG. 4 are generated. Furthermore, since the gate signal line is usually formed of thin film wiring such as a silicon thin film and is higher than the surrounding area, it is difficult to
Due to the strong alignment, the domain regions exist fairly stably, and are a major cause of deterioration in the display quality of liquid crystals, especially the contrast.

The present invention was invented to solve the drawbacks of such conventional liquid crystal panels, and by covering part of the gate signal line, data signal twin, and switching transistor with a liquid crystal drive electrode through an insulating film. ,
The feature is that it prevents the reduction in contrast caused by the generation of liquid crystal domains. FIG. 6 shows a pixel pattern for one pixel of an active matrix type liquid crystal display device according to the present invention.
A portion of 5 is covered with a liquid crystal drive electrode 17 via an insulating film. The alignment state of liquid crystal molecules in such a case is shown in FIG. FIG. 7 shows the orientation state of liquid crystal molecules in the BB cross section of FIG. 6, and the gate signal line 15 in the figure is completely covered with the liquid crystal drive electrode 17. In this case, even if the gate signal line has the same potential as the counter electrode, a voltage is applied between the liquid crystal drive electrode on the gate signal line and the counter electrode 10, so the liquid crystal molecules will be aligned vertically. Become. At this time, since the liquid crystal 22 located in the gap between the opposing liquid crystal drive electrodes is an area to which no voltage is applied, it is affected by the liquid molecules on both sides even though it is initially aligned horizontally. This gap also contributes to the display, so an increase in contrast can be expected.

In FIG. 6, since the gate signal line and the liquid drive electrode overlap each other via an insulating film, the capacitance of this overlapped portion becomes an additional capacitance on the drain side of the switching transistor. In this case, when added to the liquid crystal capacitance, the write voltage holding capacity becomes larger, so there is an advantage that the margin becomes larger. However, the present invention is not limited to this, and is also effective in a pixel pattern as shown in FIG. 8 shows a pattern in which the gate signal line 15 is covered with a liquid crystal drive electrode 17, similar to the pixel pattern in FIG. 6, but in the case of FIG. 8, the liquid crystal drive electrode connected to the switching transistor is , has a pattern that covers its own gate signal line. In such a case, the weight capacitance between the gate signal line and the liquid crystal drive electrode has no effect as an additional capacitance as explained in FIG. 6. However, even in the pixel pattern shown in FIG. 8, a liquid crystal domain as described in FIG. 4 does not occur, so that display quality with high contrast can be obtained. Furthermore, in FIG. 6, since the switching transistor region is also covered with the liquid crystal drive electrode, this region also contributes to display, further improving the display quality. FIG. 9 is also an example of a pixel pattern according to the present invention. In this embodiment, since a portion of the data signal line is also covered with the liquid crystal drive electrode, further improvement in contrast can be expected.

FIG. 10 is an explanatory diagram for further modeling and explaining the effects of the present invention, in which (a) is an example of a display on a conventional liquid crystal panel, and (Cb) is an example of a display on a liquid crystal panel according to the present invention. In other words, in the conventional liquid crystal panel, the gap between the liquid crystal drive electrodes was occupied by the gate signal line and did not contribute to the display, whereas in the liquid crystal panel of the present invention, the gap between the liquid crystal drive electrodes was occupied by the gate signal line and did not contribute to the display. We can expect improvement.

In FIG. 10, 23 is a liquid crystal drive electrode, and 24 is a gap between the liquid crystal drive electrodes.

As described above based on the embodiments, the present invention provides a liquid crystal display device in which an active matrix substrate is used as one substrate constituting a liquid crystal panel. The present invention relates to a liquid crystal display device characterized in that a part of a transistor is covered with a liquid crystal drive electrode via an insulating film, and particularly in a substrate where the active matrix substrate is a thin film transistor matrix formed on a transparent substrate. Since the gate signal line, data signal line, and switching transistor parts are higher than the surrounding area, if these parts are not covered with the liquid crystal drive electrode, they will be strongly oriented due to rubbing, and domains will be generated and displayed. This has the effect of preventing deterioration in quality, and therefore greatly contributes to improving the contrast of active matrix liquid crystal display devices using thin film transistors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of a liquid crystal display device using a thin film transistor matrix substrate, and FIG. 2 is a circuit diagram of one pixel of an active matrix circuit. Figure 3 is a pattern diagram for one stroke. FIG. 4 is an explanatory diagram of the alignment state of liquid crystal molecules when the gate signal line is not covered with a liquid crystal drive electrode. FIG. 5 is a potential diagram showing the relationship between gate signal voltage, data signal voltage, and counter electrode potential, and FIGS. 6 to 9 show pixel patterns of a liquid crystal display panel according to the present invention and gate signals covered by liquid crystal drive electrodes. FIG. 3 is an explanatory diagram showing the alignment state of liquid crystal molecules on a line and in the vicinity thereof. FIG. 10 is an explanatory diagram showing a model of improvement in contrast of a liquid crystal panel according to the present invention. 1... Transparent substrate 2... Channel part 3 of thin film transistor...
... Source, drain region 4 ... Gate electrode 5 ... Insulating film 6 ... Metal wiring 7 ... Transparent conductive film 8 ... ...Liquid crystal layer 9...Upper glass 10...Counter electrode 11...Polarizing plate 12...Polarizing plate 13...Reflecting plate 14 ...Data signal line 15...Gate signal line 16...Switching transistor 1 door--
・Liquid crystal driving electrode゛::□ 18...Liquid crystal layer 19...Counter electrode 20...Liquid crystal molecule 21...Domain 22... Liquid crystal molecules 23 in the gap between the liquid crystal drive electrodes
...Liquid crystal drive electrode 24...Liquid crystal drive electrode gap tool Applicant: Suwa Seikosha Co., Ltd.? ;S1 Day 2 Figure 3\I Figure 4 Figure 5 Figure 7 Shi1

Claims (2)

[Claims] (1) As one of the substrates constituting the liquid crystal panel, multiple gate signal lines and multiple data signal lines are orthogonal to each other, and each intersection is connected to an active pixel circuit consisting of a switching element and a liquid crystal drive electrode. A liquid crystal display device using a matrix substrate, wherein a portion of the gate signal line, the data signal line, and the switching element are covered with the liquid crystal drive electrode via an insulating film. Device. (2) The liquid crystal display device according to claim 1, wherein the active matrix substrate is a silicon thin film transistor matrix substrate formed on a transparent substrate.