JPH0444010A - Active matrix liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent a printing phenomenon and an after-image phenomenon from generating by providing a distribution film wherein liquid crystal molecules on the surface of a substrate are oriented at a 2-10 deg. tilt angle. CONSTITUTION:In an ON state, an electric field is applied between a transparent electrode 4 and a transparent electrode 5, so liquid crystal molecules 8a nearby the center of a liquid crystal layer 8 are almost perpendicular to the electrodes as usual. Liquid crystal molecules 8b nearby the substrate, on the other hand, are oriented almost in parallel to the electrodes, i.e. at a 2-10 deg. tilt angle to the electrodes under the influence of the orienting film 7. Consequently, even when an electric field which has the same intensity as before is applied from an electric conductor, the liquid crystal molecules 8c nearby the electric conductor 3 never enters a metastable state wherein they are at a different angle from the liquid crystal molecules 8b. No disclination is therefore generated. Consequently, generation of the printing phenomenon and after-image phenomenon can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and particularly to an active matrix liquid crystal display device having active elements such as transistors and diodes in each display pixel.

[Conventional technology]

An active matrix liquid crystal display element has a structure in which a glass substrate having an active element and a glass substrate having a transparent electrode are stacked on top of each other, and a nematic liquid crystal is injected in between. The liquid crystal is oriented such that the direction of the long sleeve of the liquid crystal molecules is twisted by about 90 degrees by the alignment films on both glass substrates, and constitutes a TN (twisted nematic) type liquid crystal element.

Liquid crystal display elements that do not have active elements have fewer irregularities on the substrate, whereas active matrix display elements have fewer irregularities on the substrate.
Because there are semiconductor layers, insulating layers, wiring layers, etc. that make up the active elements, the substrate surface has many irregularities. If there are many irregularities, the alignment of the liquid crystal is distorted, a phenomenon occurs in which the direction of rotation of the liquid crystal is reversed (called reverse tilt), and a boundary is formed with the normally oriented area (called disclination), resulting in poor alignment. It is more likely to occur.

In order to prevent this reverse tilt from occurring, conventional active matrix liquid crystal display devices use an alignment film that orients the liquid crystal on the substrate so that it is tilted back and forth by 1° from the substrate surface (referred to as a tilt angle of around 1°). .

[Problem to be solved by the invention]

In active matrix liquid crystal display devices with a tilt angle of around 1°, when the display is in a stopped state, such as when the switch is turned off, or when a low voltage is applied to the display pixels,
No orientation defects occur.

Next, a case of an ON state in which a high voltage is applied to a display pixel will be described. FIG. 2 is a cross-sectional view of a conventional example, in which transparent electrodes 41. alignment film 6], a substrate 11 provided with a black matrix 91, and a transparent electrode 51. Wiring 31. It is composed of a substrate 22 on which an alignment film 71 is provided and a liquid crystal layer 81.

In the ON state, since an electric field is applied between the transparent electrode 41 and the transparent electrode 51, the liquid crystal molecules 81a near the center of the liquid crystal layer 81 are substantially perpendicular to the electrodes. On the other hand, the liquid crystal molecules 81b located near the substrate are
It is almost parallel to the electrode with an angle (around 1°) determined by the influence of 1.

Here, a voltage for driving an active element such as a transistor is applied to the wiring 31, but due to the influence of the electric field from the wiring, the liquid crystal molecules 81c near the wiring 31
is the liquid crystal molecule 81. A phenomenon occurs in which a disclination 100 occurs, which is a discontinuous boundary between the orientations of both liquid molecules.

Because of this phenomenon, there is a problem in that even if the display is changed, a burn-in phenomenon or afterimage phenomenon occurs in which the previous display looks faint.

[Means to solve the problem]

The active matrix liquid crystal display element of the present invention includes an alignment film in which liquid crystal molecules on the substrate surface are aligned with a tilt angle of 2° or more and 0''C or less.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an active matrix liquid crystal display device according to an embodiment of the present invention, in which transparent electrodes 4° alignment film 6. A substrate 1 provided with a black matrix 9 and a transparent electrode 5.
Active cables such as transistors (omitted in the diagram), wiring 3
．． It is composed of a substrate 2 provided with an alignment film 7 and a liquid crystal layer 8.

In the ON state, an electric field is applied between the transparent electrode 4 and the transparent electrode 5, so that the liquid crystal molecules 8a near the center of the liquid crystal layer 8 are different from the conventional example up to the point where they are perpendicular to the electrodes. It's the same. On the other hand, the liquid crystal molecules 8b located near the substrate are oriented almost parallel to the electrodes due to the influence of the alignment film 7, and more precisely, at a tilt angle of 2° to 10°.

Even if an electric field of the same intensity as in the conventional example is applied from the wiring 3, the liquid crystal molecules 8c near the wiring 3 should also take a tilt angle different from that of the liquid crystal molecules 8b because the tilt angle is large (so that the liquid crystal molecules 8c do not shift to a stable state). .Therefore, disclination does not occur.

Here, the results of a prototype are shown for reference.

When using an alignment film material with a tilt angle of 11°,
When changing the display, a burn-in phenomenon or afterimage phenomenon that left a tingling sensation from the previous display occurred. In comparison, when an alignment film material with a tilt angle of 24° or 31° was used, the incidence of image sticking was halved.

Furthermore, when an alignment film coating material with a tilt angle of 5° was used, no seizure phenomenon occurred at all.

In addition, when a high tilt angle alignment film material having a tilt angle of 2° to 10° was used, the above-mentioned image sticking phenomenon was reduced or did not occur at all.

〔Effect of the invention〕

As described above, the present invention has the advantage that disclination does not occur due to the influence of electric fields from wiring, and therefore burn-in and afterimage phenomena do not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. 3... Wiring, 4... Transparent electrode, 5... Transparent electrode, 6.7... Alignment film, End...
Liquid crystal layer, 8a, 8b. 8c...Liquid crystal molecule. Agent Susumu Hara, Patent Attorney Procedural Amendment (Voluntary) 3.2.1991. -4 Year Display of the case in the "Detailed Description of the Invention" section of the specification subject to amendment 1st
In the 8th line, "reverse tilt" is corrected to "reverse twist." (2) "10°C" on page 4, line 13 of the specification is corrected to "10°." Name of the invention Active matrix liquid crystal display device Agent Patent attorney Susumu UchiharaRelationship with the amendment case

Claims (1)

[Claims] An active matrix liquid crystal display device having active elements such as transistors and diodes in each display pixel, characterized in that liquid crystal molecules on both substrate surfaces are oriented with an inclination of 2° or more and 10° or less. element.