JPH02223927A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To reduce the electrostatic capacity of liquid crystal between a common electrode and a signal line by constituting the common electrode lest it should be overlapped on the signal line. CONSTITUTION:Signal voltage and scanning voltage generated from a signal circuit 2 and a scanning circuit 3 are impressed on the TFT 1 of each picture element 4 through a signal line 6 and a scanning line 7 and DC or AC voltage is impressed on the common electrode 5 as common voltage. The common electrode 5 is formed of a transparent electrode such as an ITO, etc., and constituted in such a pattern that the common electrode 5 and the signal line 6 are not overlapped in the state of putting a liquid crystal layer between them. Thus, the electrostatic capacity of the liquid crystal between the common electrode 5 and the signal line 6 is drastically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display panel, and more particularly to a pattern for forming a common electrode of a TPT-driven liquid crystal active matrix display panel.

[Conventional technology]

Figure 2 shows a conventional TPT drive liquid crystal actitomato 99.
People display panel.

Scanning circuit 2. The gate voltage and signal voltage generated from the signal circuit 3 are applied to the gate electrode and drain electrode of the TFTI of each pixel 4 through the scanning line 7 and the signal line 6.

On the other hand, a transparent electrode such as ITO is formed as a common electrode on the entire surface of the glass substrate facing each other with the liquid crystal layer in between, and a DC or AC voltage is applied as a common voltage.

Since one common electrode 5 is formed on the entire surface, it overlaps with the signal line, the scanning line, and the liquid crystal layer. For this reason, a capacitance exists in the liquid crystal layer between these wiring lines and the common electrode.

However, in conventional small panels, the area of the wiring is small, so this capacitance is so small that it does not affect the display quality at all.

[5I problems that the invention is trying to solve] The above conventional technology does not take into account the influence of the capacitance of the liquid crystal between the signal line and the common electrode. The electrostatic capacitance of the liquid crystal between the two increases, causing problems such as distortion in the waveform of the signal voltage.

The purpose of the present invention is to reduce this capacitance.

[Means to solve the problem]

The above object is achieved by patterning the common electrode so that there is no overlap between the common electrode and the signal line.

[Effect]

The common electrode has a structure that does not overlap with the signal line. As a result, the capacitance of the liquid crystal between the common electrode and the signal line is greatly reduced, and distortion of the signal voltage waveform can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a TPT, 2 is a signal circuit, 3 is a scanning circuit, 4 is a pixel, 5 is a common electrode, 6 is a signal line, and 7 is a scanning line. Signal voltages and scanning voltages generated from the signal circuit 2 and the scanning circuit 3 are applied to the signal line 6 and the scanning line 7.
is applied to the TFTI of each pixel 4 through. Common electrode 5
A direct current or alternating current voltage is applied as a common voltage.

The common electrode 5 is formed of a transparent electrode such as ITO, and is formed in a pattern such that the common electrode 5 and the signal line 6 do not overlap across the liquid crystal layer.

Thereby, the capacitance of the liquid crystal between the common electrode 5 and the signal line 6 can be significantly reduced. Therefore, it is possible to prevent the waveform of the signal voltage from being rounded due to the capacitance of the liquid crystal between the common electrode 5 and the signal line 6.

FIG. 3 is an equivalent circuit of one pixel of a liquid crystal display panel. 6 is a signal line, 7 is a scanning line, 9 is a common electrode, 13 is a capacitance between gate and source, 14 is a capacitance between gate and drain, 15 is a capacitance between drain and source, and 16 is a capacitance between drain and source. The capacitance between the signal line and the scanning line, 17 is the capacitance of the liquid crystal, etc. between the source electrode and the common electrode,
18 is a capacitance between the signal line and the common electrode, and 19 is a capacitance between the scanning line and the common electrode.

Liquid crystal capacitance Ca18 between the signal line 6 and the common electrode 9
is when the common electrode is formed on the entire surface.

Proportional to the area of the signal line. Therefore, in a small-sized panel, the area of the signal line is small, so the electrostatic capacitance C118 is small, and the influence on the signal voltage waveform can be almost ignored. However, as liquid crystal displays become larger in size in the future, the signal lines 6 will become longer and the area of the signal lines will become larger. Accordingly, the capacitance C118 between the signal line 6 and the common electrode increases. In addition, as the length of the signal line 6 increases, the resistance value Ra of the signal line 6 also increases. Since the rounding of the signal voltage waveform is determined by the time constant τ τ=R−・C−, the rounding of the signal voltage waveform becomes a serious problem as the area of liquid crystal display panels becomes larger. The capacitance between the signal line 6 and the common electrode is reduced. It is something.

FIG. 4 is a sectional view of one embodiment of the present invention. As shown in the figure, the structure is such that the common electrode does not overlap on the signal line 10. Note that when displaying, a major feature is that since the area on the signal line lo is not included in the effective pixel area, the aperture ratio does not decrease.

Further, since the pattern of the common electrode 9 of the present invention is simple, the process does not become complicated.

This embodiment is a display device using TPT as a switching element and liquid crystal as a display device. The present invention uses a-8i, p-8iT as other switching elements.
A three-terminal element such as FT or a two-terminal element such as AIM may be used.

In addition to non-emissive display devices such as liquid crystals,
A light emitting type such as EL may be used.

(Effects of the Invention) According to the present invention, it is possible to greatly reduce the capacitance between the signal line and the common electrode without reducing the aperture ratio, so it is possible to prevent phenomena such as waveform distortion of the signal voltage. can.

[Brief explanation of the drawing]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is a plan view showing a conventional example, FIG. 3 is an equivalent circuit diagram of the panel, and FIG. 4 is a sectional view of FIG. 1. DESCRIPTION OF SYMBOLS 1... TFT, 2... Signal circuit, 3... Scanning circuit, 4... Pixel, 5... Common electrode, 6... Signal line, 7... Scanning line, 8...・Glass substrate, 9...
- Common electrode, 10... Signal line, 1-1... Pixel electrode, 12... Liquid crystal. S~-Ichiei Ih permanent position +2--~Decrease Akira

Claims (1)

[Claims] 1. A plurality of scanning electrodes and signal electrodes are provided on a substrate, switching elements are arranged in a matrix at the intersections of these electrodes to form one pixel, and a common electrode is provided on a substrate facing the substrate with a liquid crystal interposed therebetween. A liquid crystal display panel characterized in that the common electrode and the signal electrode do not overlap with each other via the liquid crystal.