JPH04223436A - Active matrix liquid crystal display element - Google Patents

Abstract

PURPOSE:To supress the generation of discrination by preventing the disturbance in the orientation of liquid crystal molecules by the electric fields generated between picture element electrodes and gate wirings (or between the picture element electrodes and drain wirings). CONSTITUTION:The electric fields generated between the picture elements and gate wirings of the TFT substrate formed with the gate wirings 1a, 1b, drain wirings 2a, 2b, picture element electrodes 4 and TFTs 5 are higher than the electric fields generated between the picture element electrodes and drain wirings. The orientation treatment of the TFT substrate is so executed that the liquid crystal molecules are arranged in parallel with the gate wirings if the discrimination is liable to be generated by the former. The orientation treatment is so executed that the liquid crystal molecules are arranged in parallel with the drain wirings in the opposite case.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display element constructed by connecting switching elements to individual display pixels.

0002

[Prior Art] A TFT type active matrix liquid crystal display element, which is a typical active matrix type display element, is a combination of a glass substrate having a thin film transistor and a pixel electrode, and a glass substrate on which a transparent electrode is formed on the entire surface. The structure is such that nematic liquid crystal is injected into the gap. The liquid crystal is usually oriented such that the long axes of the liquid crystal molecules are twisted around 90 degrees by alignment films on both glass substrates, forming a TN (twisted nematic) type liquid crystal element.

[0003] Here, the structure of a glass substrate (hereinafter referred to as a TFT substrate) having a thin film transistor will be explained. FIG. 2 is a plan view of one pixel portion of the TFT substrate. As shown in the figure, the pixel electrode 4 includes gate wirings 1a, 1b and drain wirings 2a arranged in a grid pattern.
, 2b on all sides. The signal that controls the display of this pixel is according to the control signal of the gate wiring 1a.
TFT 5 and its source electrode 3 from drain wiring 2a
is transmitted to the pixel electrode 4 via.

Conventionally, alignment treatment applied to a TFT substrate to align liquid crystal molecules in a desired direction is performed at an angle of about 45° with the gate wiring and drain wiring, as shown by d in the figure. The opposing substrate was subjected to alignment treatment in the direction indicated by e in the figure. Therefore, the internal liquid crystal was twisted in the direction indicated by f in the figure to constitute a TN type liquid crystal element.

[0005]

In an active matrix liquid crystal display element, gate wirings and drain wirings run around pixels, so an electric field is generated between the pixel electrode and these gate wirings and drain wirings. Therefore,
The alignment of liquid crystal molecules near the wiring is pushed out, and discontinuous boundaries of alignment called disclinations occur in the liquid crystal.

[0006] In the conventional alignment direction, the alignment of liquid crystals is affected by the electric field between both wiring lines and the pixel electrode, so disclination occurs even inside the pixel electrode.
As a result, there is a problem in that even if the display is changed, a burn-in phenomenon or an afterimage phenomenon occurs in which the previous display looks faint.

[0007]

[Means for Solving the Problems] The active matrix liquid crystal display element of the present invention includes a switching element substrate and a counter substrate facing the switching element substrate, and the switching element substrate has a plurality of signal wiring lines parallel to each other. , a plurality of pixel electrodes sandwiched between each wiring, and a switching element connected to each pixel electrode and one of the signal wirings are formed, and the switching element substrate has liquid crystal molecules near the signal wiring. Orientation processing is performed so that they are arranged at an angle of 20° or less.

[0008]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of one pixel portion of a TFT substrate according to an embodiment of the present invention.

As shown in the figure, on the TFT substrate are gate wirings 1a, 1b, drain wirings 2a, 2b, TF
T5, source electrode 3 of TFT5, and pixel electrode 4 are formed. And an alignment film is formed on its surface,
The orientation process is performed in a direction substantially parallel to gate wirings 1a and 1b, as indicated by a in the figure.

Correspondingly, the opposing substrate is aligned in the direction shown by b in the figure, and the liquid crystal inside is twisted in the direction shown by c in the figure to form a TN type liquid crystal element. There is.

In a normal TFT driving state, the electric field between the pixel electrode and the gate wiring is higher than that between the pixel electrode and the drain wiring. Therefore, the nematic liquid crystal molecules used here are more strongly influenced by the electric field in the direction of the long axis of the molecule, and are not so affected by the electric field in the direction of the short axis of the molecule. Therefore, when the liquid crystal is oriented substantially parallel to the gate wiring as in this embodiment, although the electric field between the gate wiring and the pixel electrode is strong, the alignment direction of the liquid crystal molecules is not greatly disturbed. There is no possibility that disclination will occur in the liquid crystal and the liquid crystal will enter a metastable state.

On the other hand, in the alignment direction of the embodiment, the liquid crystal molecules are easily influenced by the electric field between the pixel electrode and the drain wiring. However, since the electric field on this side is usually lower than the electric field between the pixel electrode and the gate wiring, disclination does not occur on this side either.

In the above embodiment, since the electric field between the pixel electrode and the gate wiring is higher, the alignment is made parallel to the gate wiring, but this alignment direction is not always the best. This is because a high electric field is not always generated on the gate wiring side. The question of whether it is better to orient parallel to the drain wiring or the gate wiring depends on the distance and shape between each wiring and the pixel electrode, the drive voltage of each wiring, and which side disclination is more likely to occur. determined by

[0014] In the above embodiment, the wiring was parallel to the wiring, but even if the wiring was slightly deviated from parallel, disclination could be reduced. If the directions of the wiring and the orientation were within ±20°, the burn-in phenomenon and afterimage phenomenon were reduced due to the above-mentioned effects. On the other hand, in the range of more than 20° to 45° (the direction of the conventional example), burn-in phenomena and afterimage phenomena occurred as in the conventional case.

[0015] In the above embodiment, a TFT type active matrix liquid crystal display element has been described, but the present invention is not limited thereto, and is also applicable to those using other switching elements such as MIM. When a two-terminal switching element is used, the switching element substrate is aligned so as to form an angle of 20° or less with the signal wiring.

[0016]

As explained above, the present invention provides a switching device substrate for an active matrix liquid crystal display device in which when there is only one type of signal wiring, the signal wiring is arranged to be approximately parallel to the signal wiring; If there are two types, the orientation process is performed so that the signal wiring is approximately parallel to the side where disclination is more likely to occur, so according to the present invention, the signal wiring on the side where disclination is more likely to occur The electric field between the signal wiring and the pixel electrode acts in the short axis direction of the liquid crystal molecules, so that the alignment of the liquid crystal is not disturbed by this electric field, and the occurrence of disclination is suppressed. Therefore, according to the present invention, burn-in phenomena and afterimage phenomena are reduced.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the present invention.

FIG. 2 is a plan view of a conventional example.

[Explanation of symbols]

1a, 1b Gate wiring 2a, 2b Drain wiring 3 Source electrode 4 Pixel electrode 5 TFT a, d　TFT substrate side liquid crystal alignment direction b, e　Counter substrate side liquid crystal alignment direction c, f Twisting direction of liquid crystal molecules

Claims (2)

[Claims] 1. A plurality of signal wirings arranged in parallel to each other on a switching element substrate, a plurality of pixel electrodes arranged between each signal wiring, and a plurality of pixel electrodes connected between each pixel electrode and the signal wiring. In the active matrix liquid crystal display device comprising a switching element, the switching element substrate is subjected to alignment treatment such that liquid crystal molecules near the switching element substrate are aligned at an angle of 20° or less with respect to the signal wiring. An active matrix liquid crystal display element characterized by: 2. A plurality of gate wirings arranged parallel to each other on a TFT substrate, a plurality of drain wirings arranged perpendicularly to the gate wirings, and a region surrounded by each gate wiring and each drain wiring. In an active matrix liquid crystal display element, the active matrix liquid crystal display element includes a pixel electrode provided for each pixel electrode, a plurality of thin film transistors whose sources and drains are connected between the pixel electrode and the drain wiring, and whose gates are connected to the gate wiring, The TFT substrate has the TFT substrate
An active matrix liquid crystal display element characterized in that an alignment treatment is performed so that liquid crystal molecules near the FT substrate are aligned at an angle of 20 degrees or less with the gate wiring or the drain wiring.