JPH06289408A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent a display defect, after-image and seizure and to improve display quality by forming electrodes in parts exclusive of electrodes for display on the inside surface of substrates and varying the applied voltage of a liquid crystal layer near these electrodes from the applied voltage of other liquid crystal layer. CONSTITUTION:The transparent electrodes 14 are formed in the parts exclusive of the transparent electrodes 10 corresponding to the effective display area of the lower glass substrate 11 of the liquid crystal display device composed of the liquid crystal layer 6 clamped between two sheets of the glass substrates 2, 11 and the electrodes 3, 10 for display formed on the inside surfaces of the substrates 2, 11. Either or both of insulating overcoats 9 and oriented films 8 are not deposited above and below these transparent electrodes 14. As a result, a difference is generated in the waveforms acting on the liquid crystal layer and a residual DC component is generated between the upper and lower electrodes when electrical AC signal are applied to the upper and lower transparent electrodes. The deterioration in the liquid crystal is lessened if the residual DC component is acted at 5 to 100mV by the electrical signal to be impressed to the transparent electrodes 14 to periodically invert the residual DC component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using liquid crystal.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, if the display state to which an electric signal is applied is kept as it is, it is difficult to see the display due to a burned-in display pattern or an afterimage phenomenon. There is a defect that a display pattern is missing due to a decrease in the contrast ratio of a part of the display pattern. These are caused by ionic contamination of the constituent materials of the liquid crystal display device. Further, due to variations in the electric signal voltage applied to the liquid crystal layer, the liquid crystal layer can have strong and weak electric field strengths. The ions dissolved in the liquid crystal layer or the ions in the alignment film migrate in the liquid crystal layer or the alignment film due to the strength of the electric field strength, and the ions are locally concentrated in the liquid crystal having the strong electric field strength. This causes the display pattern to be missing. Further, ions are locally collected in the alignment film to form an electric double layer, which causes image sticking or an afterimage.

The cause of this ionic contamination is contamination from a sealing material of an organic material, a sealing material after injection, an alignment film for orienting liquid crystal molecules, contamination by ions dissolved in the liquid crystal material itself, and the like. This is due to cleaning in the process of manufacturing the liquid crystal cell, and processing such as rubbing, printing, firing and injection.

[0004]

It is impossible to reduce the number of ions in these manufacturing processes and constituent materials to zero. Therefore, the present invention forcibly collects the ions in a certain electrode even if the ions are dissolved in the liquid crystal layer to some extent or exists in the alignment film, and thus the electrode in the original effective area for display is provided. I tried to reduce the number of ions in the part. This is intended to prevent burn-in of a display pattern, an afterimage, and a lack of a display pattern. The present invention is a display device in which an electrode, an alignment film, and an overcoat are devised in order to achieve the above object when used as a product after manufacturing the display device.

[0005]

A means for solving the problems will be described below with reference to the drawings. FIG. 2 shows a conventional example. A polarizing plate 1 and a transparent electrode 3 are attached to the upper glass substrate 2. A polarizing plate 12 and a transparent electrode 10 are attached to the lower glass substrate 11 via the liquid crystal 6. Further transparent electrodes 3, 10
Are coated with insulating overcoats 4 and 9, and alignment films 5 and 8 are coated thereon. The upper and lower glass substrates 2 and 11 are adhered by a sealing material 13, and the liquid crystal injection hole is sealed by a sealing material 7.

In the liquid crystal display device according to the conventional example, the liquid crystal 6, the sealant 13, the alignment films 5 and 8 and the encapsulant 7, which are the constituent materials, or the color filter, if any, is used to generate the ions. Are dissolved in the liquid crystal, and these materials are ionically contaminated by the washing, printing and firing environments during the manufacturing process. In this state, when an electric alternating current signal is applied to the upper and lower transparent electrodes 3 and 10, portions where the film thicknesses of the alignment films 5 and 8 are thin, portions where the insulating overcoats 4 and 9 are thin, or transparent electrodes At the edge portions and the protruding portions of 3 and 10, the electric field strength applied to the liquid crystal layer locally becomes strong, and the ions are attracted there, so that the ion concentration becomes high. The voltage applied to the liquid crystal in the portion where the electric field strength is locally strong is lowered, the contrast ratio is lowered, and the phenomenon of display loss appears. Ions in the alignment film and ions that have migrated in the liquid crystal enter the alignment film to form an electric double layer, which causes an afterimage and burn-in during display. Ion contamination and elution from the material during these manufacturing steps, film thickness unevenness, scratches, alignment film 5 during formation of the insulating overcoats 4 and 9,
It is difficult to eliminate film thickness unevenness, scratches, and scratches on the alignment film during the rubbing process, especially deep scratches on the alignment film corresponding to the edge portion of the transparent electrode. There is a phenomenon.

[0007]

FIG. 1 shows an embodiment according to the present invention. In a cell of a liquid crystal display device, a transparent electrode 14 is formed separately from a transparent electrode corresponding to an effective display area, and an insulating overcoat or an alignment film or both of the upper and lower parts of the electrode portion is not formed. It was done like this. As a result, when an electric AC signal is applied to the upper and lower transparent electrodes, a difference occurs in the waveform applied to the liquid crystal layer between the upper and lower electrodes, and a residual DC component is generated. Since the ions in the cell gather in this intentionally set residual DC component area,
It is possible to prevent display defects, afterimages, and image sticking in the effective display area.

Example 1 In FIG. 2, the transparent electrode 14
Has a structure in which the upper and lower insulating overcoats and the alignment film are all removed, and the electric field strength applied to the liquid crystal can be made larger than that on other transparent electrodes in the effective display area, and the same effect can be obtained.

(Embodiment 2) Similar effects can be obtained even if the DC residual component is applied from 5 mV to 100 mV by the electric signal applied to the transparent electrode 14. At this time, if the plus and minus of the DC residual component are periodically inverted, the deterioration of the liquid crystal can be reduced.

[0010]

As described above in detail in the embodiments,
In the liquid crystal cell, a special electrode for adsorbing ions according to the present invention is provided, and at least one of the upper and lower insulating overcoats or the alignment film on the electrode is removed or a DC residual component is intentionally generated by an electric signal. By collecting and adsorbing such ions, it is possible to prevent display defects, afterimages, and image sticking in the effective display area portion, and improve the display quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the present invention.

FIG. 2 is a cross-sectional view of an example of a conventional display device.

[Explanation of symbols]

 1, 12 Polarizing plate 2, 11 Glass substrate 3, 10 Transparent electrode 4, 9 Insulation overcoat 5, 8 Alignment film 6 Liquid crystal 7 Sealing material 13 Sealing material 14 Ion adsorption transparent electrode

Claims (2)

[Claims] 1. A liquid crystal display device comprising a liquid crystal layer sandwiched between two substrates and a display electrode formed on the inner surface of the substrate, wherein the inner surface of at least one substrate is An electrode is formed in a portion other than the display electrode, and the voltage applied to the liquid crystal layer near the electrode is different from the voltage applied to the liquid crystal layer near the display electrode. Liquid crystal display device. 2. The voltage to the liquid crystal layer near the electrode is
A liquid crystal display device, wherein the voltage is higher than the voltage applied to the liquid crystal layer near the display electrode or the voltage applied to the liquid crystal layer near the electrode is a voltage containing a DC component.