JPH03167529A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To collect an impure ion in a moment when a panel is driven and to realize display which is uniform and high quality by making at least a part of the surface of a gate bus line abut on a liquid crystal through an oriented film. CONSTITUTION:A thin film transistor for driving a picture element and the gate bus line GB which impresses a selecting signal on the thin film transistor are provided on one of a pair of insulating substrates interposing the liquid crystal and a part of the surface of the gate bus line GB is made to abut on the liquid crystal through only the oriented film. Since the oriented film is thin, the potential of the gate bus line GB acts on the liquid crystal at the part of the oriented film and attracts a positive ion in the liquid crystal by the negative potential. Thus, the positive ion exists extremely few in the liquid crystal at the other part and the excellent display is obtained.

Description

[Detailed Description of the Invention] [Summary] An object of the present invention is to provide a function for collecting impurity ions that cause a decrease in resistance even if a decrease in liquid crystal resistance occurs within the panel in an active matrix type liquid crystal display device. A thin film transistor for pixel driving is provided on one of the insulating substrates of a pair of insulating substrates sandwiching the liquid crystal, and a gate bus line for applying a selection signal to the thin film transistor, and a surface of the gate bus line is provided. At least a portion of the liquid crystal is in contact with the liquid crystal via an alignment film.

[Industrial application field]

The present invention relates to an active matrix type liquid crystal display device, and in particular to a TP for preventing a drop in liquid crystal resistance and further increasing the resistance.
Regarding T-substrate structure.

In active matrix liquid crystal display devices, TP
Along with the off-characteristics of T, the liquid crystal resistance is extremely important in terms of display quality.

The smaller the off-state current is, the better the TPT's off-state characteristics are, and the higher the liquid crystal resistance, the higher the contrast display can be obtained. From this perspective, research on reducing off-state current in TPT element characteristics is progressing, and regarding liquid crystal resistors, technology to prevent liquid crystal contamination during the manufacturing process, and
Research is being conducted on increasing the resistance of liquid crystals.

Furthermore, regarding the liquid crystal resistor, there is a requirement that this high resistance state must be maintained for a long period of time in order to uniformly increase the resistance of the liquid crystal resistor within the display area and maintain high reliability.

[Conventional technology]

In conventional active matrix liquid crystal display devices, in order to increase the liquid crystal resistance, (1) a liquid crystal with a high resistance value is used as the injected liquid crystal;

■ Use a material with excellent voltage holding properties as the alignment material.

There are two requirements, and only when these two requirements are met simultaneously can a liquid crystal display panel having high resistance characteristics be obtained.

[Problem to be solved by the invention]

However, factors that prevent the above-mentioned liquid crystal from becoming high in resistance include the occurrence of localized areas where the liquid crystal resistance decreases due to foreign matter (particularly human body dust) mixed into the panel during panel fabrication;
Furthermore, there is a problem in that, due to long-term running or storage, the underlying contamination of the substrate gradually dissolves into the liquid crystal layer, reducing the liquid crystal resistance.

An object of the present invention is to provide a function to recover impurity ions that cause a decrease in liquid crystal resistance even if a decrease in liquid crystal resistance occurs within the panel.

[Means to solve the problem]

In the present invention, at least a part of the surface of the gate bus line that applies a selection signal to the pixel driving thin film transistor is in contact with the liquid crystal via an alignment film.

In such a structure, a part of the insulating film normally formed on the gate bus line is removed on the gate bus line to form an opening that exposes the surface of the gate bus line at the bottom. It can be easily manufactured by shaping the alignment film.

[For production]

In active matrix liquid crystal display devices, it is known that the main impurity ions that cause a decrease in liquid crystal resistance are metal cations (such as Na'').

The present invention realizes a configuration in which these metal cations can be recovered electrically.

An active matrix liquid crystal display device includes a thin film transistor element for each display pixel, and writes and holds data in the display pixel by turning on and off TPT.

Here, to turn on the TPT, a positive voltage is applied to the gate, and to turn it off (voltage holding state), a negative voltage is applied to the gate. By repeating this process, various images are displayed.

The time change in the voltage applied to one gate bus line is such that a positive voltage is applied to the gate bus line only when it is selected, and a negative voltage is applied to the bus line when another line is selected. Voltage is applied. That is, a negative voltage is applied to the gate pass line most of the time.

In the present invention, a portion of the gate bus line surface is in contact with the liquid crystal only through the alignment film. Since the alignment film is thin, the potential of the gate bus line acts on the liquid crystal in this part, and the negative potential adsorbs the cations in the liquid crystal, so in other parts there are very few cations in the liquid crystal. , a good display can be obtained.

Since the present invention has a function of increasing the liquid crystal resistance by driving the active matrix type liquid crystal display device in this way, it is possible to eliminate any display defects related to a decrease in liquid crystal resistance, and the reliability can be improved. A liquid crystal display device with high display quality can be obtained.

〔Example〕

The structure of an embodiment of the present invention is shown in FIG. 1, and the structure of a conventional thin film transistor matrix is shown in FIG. 4 for comparison.

Conventionally, as shown in FIG. 4, a gate insulating film is usually formed on the gate bus line GB, and the gate? Sline CB
is covered. Therefore, as described above, even though the gate bus line GB is kept at a negative potential most of the time during driving, that potential does not affect the liquid crystal and does not collect impurity ions.

In contrast, in this embodiment, as shown in FIG. 1, a part of the gate 1 edge film formed on the gate bus line GB is selectively etched away to form an opening 1 in the gate insulating film. A part of the gate bus line GB is exposed at the bottom thereof.

In this example, the gate insulating film has a thickness of approximately 30 mm.
00 SiN. The membrane was shaped. Next, chemical vapor phase etching (Chemical Dry Etching)
) method to selectively remove the hatched portion in the figure, exposing the surface of the gate bus line GB at this portion.

The ethoching conditions were a mixed gas atmosphere with a ratio of 2:1 of CF4 and 0■, a pressure of 0.3 Torr, and an RF power of 50
It was set to 0W.

In the figure, E is a pixel electrode, G is a gate electrode, and S is a pixel electrode.
indicates a source electrode, D indicates a drain electrode, and DB indicates a drain bus line.

A liquid crystal display device was manufactured using the thus manufactured TPT substrate and a conventional TPT substrate (SiNX covers all gate bus lines), and the display states of the two were compared.

The display state is shown in FIGS. 2(a) and (bl).

In the conventional panel, contamination of the liquid crystal occurs due to foreign matter, and as shown in FIG. 3A with the reference numeral 10, a portion with low contrast is observed (white in the crossed Nicols method).

In contrast, in this example, a uniform high-contrast display was obtained as shown in (bl). Also, no abnormality occurred during long-term running and storage tests. Furthermore, impurities in the liquid crystal was recovered almost instantaneously after the panel was driven, and was found to be at a non-problematic level.

Next, in order to clarify the effects of the present invention, liquid crystal display devices having a conventional structure and a structure according to the present invention were manufactured using a liquid crystal having a resistivity of about 1010 Ωcm to be injected into the panel, and the display of both was We compared the situation. The result is the third
Shown in Figures (a) and (b).

In the display device with the conventional structure, impurities in the liquid crystal were adsorbed near the injection port, resulting in striped display irregularities 1l, as shown in FIG.

On the other hand, in the display device with the structure of the present invention, as in the conventional example, impurity ions are adsorbed near the injection port, and although the liquid crystal resistance is reduced, the non-uniformity remains in the display state as shown in (b). Not observed.

This is understood to be because in the structure of the present invention, impurity ions are quickly adsorbed and collected in the exposed area of the gate bus line GB at the moment driving is started, and the liquid crystal resistance of the display pixel portion becomes uniformly high. .

(Effects of the Invention) As explained above, according to the present invention, impurity ions are instantly collected during panel drive to eliminate all display defects and display unevenness caused by a decrease in liquid crystal resistance, thereby providing a uniform and high-quality display. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of the effects of the above-mentioned embodiment, and FIG. 4 is an explanatory diagram of the configuration of a conventional device. In the figure, GB indicates a gate bus line, and ■ indicates an opening provided in the gate insulating film. (Q) (b)

Claims (1)

[Claims] A thin film transistor for driving a pixel and a gate bus line (GB) for applying a selection signal to the thin film transistor are provided on one of a pair of insulating substrates sandwiching a liquid crystal, and a surface of the gate bus line is provided. An active matrix type liquid crystal display device, wherein at least a part of the liquid crystal is in contact with the liquid crystal via an alignment film.