JPH08101376A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To decrease the voltage fluctuations of liquid crystals by ionic impurities and to prevent the occurrence of defects of the uneven display arising as a result of the voltage fluctuation by coating the transparent electrodes of a liquid crystal display device with oriented films and insulating films to prevent the elution of the ionic impurities into liquid crystals. CONSTITUTION: This liquid crystal display device is formed by coating the transparent electrodes 3 on a counter substrate 1a and a transparent substrate 1b with the oriented films 6 and the insulating films 4 to shut off the transparent electrodes 3 against the liquid crystals 8. The elution of the ionic impurities from the transparent electrodes 3 is, therefore, prohibited and the display defects to be caused by such elution is lessened. The insulating films 4 are formed exclusive of a juncture of a display region and an external driving circuit 5 exclusive of the liquid crystal sealing part. The display region is coated with the oriented films 6. The purpose of such coating is to avert the drop of the liquid crystal voltage by formation of the insulating films 4 in the display region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device which realizes high reliability by reducing impurities that are melted from other components in liquid crystal. The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, as shown in FIG. 3, a light shielding film 2, a transparent electrode 3 and an alignment film 6 are provided on a counter substrate 1a, and a switching element 11 is provided on the other transparent substrate 1b. An insulating film 4, a transparent electrode 3 and an alignment film 6 for protecting the substrate are provided, both substrates are sealed with a seal 7, and a liquid crystal 8 is filled inside. In addition, 9 is a polarizing plate, 1
Reference numeral 0 is a conductive film, and 5 is an external drive circuit terminal. When a color display function is provided, a colored layer is formed on or below the transparent electrode 3 on the counter substrate 1a.

In Japanese Patent Laid-Open No. 58-178325, an insulating film 4 is formed on the transparent electrode 3 as shown in FIGS.
In Japanese Utility Model Laid-Open No. 2-19032, a structure in which the colored layer 12 is extended to the outside of the seal 7 is disclosed as shown in FIG. Insulating film 4 and colored layer 12 on these transparent electrodes 3
This is for covering the terminal portion of the transparent electrode 3 exposed to the external environment outside the liquid crystal enclosing portion to avoid disconnection due to corrosion.

[0004]

In the liquid crystal display device, when impurities are mixed in the liquid crystal, the voltage applied to the liquid crystal changes. This is visually recognized as display unevenness and deteriorates the image quality of the liquid crystal display device. Elution of ionic impurities from the transparent electrode is one of the causes of mixing impurities into the liquid crystal. In the conventional liquid crystal display device shown in FIG. 3, FIG. 4- (a), and FIG. 5, the transparent electrode 3 not covered with the insulating film 4 or the alignment film 6 is in contact with the liquid crystal 8 and the liquid crystal 8 It is not possible to prevent the elution of impurities into it.

On the other hand, in the example of FIG. 4- (b), since the entire surface of the transparent electrode 3 in the liquid crystal sealed portion is covered with the insulating film 4, the transparent electrode 3 is not in direct contact with the liquid crystal 8 but the transparent electrode in the display area. Since the insulating film 4 is formed on the liquid crystal 3, the voltage applied to the liquid crystal 8 drops. In order to compensate for this voltage drop, it is necessary to supply a higher voltage, which causes a problem that driving power increases.

[0006]

An active matrix type liquid crystal device according to the present invention comprises an insulating film covering a transparent electrode on a counter substrate other than a display region of a liquid crystal enclosure and an alignment film covering a display region on the counter substrate side. It has and. A silicon nitride film or a silicon oxide film is used as the insulating film.

[0007]

Since the entire surface of the transparent electrode is covered with the liquid crystal encapsulation portion by the insulating film and the alignment film, the elution of ionic impurities from the transparent electrode into the liquid crystal is considered to be necessary. Since no insulating film is formed on the display portion, no voltage drop occurs due to this.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a liquid crystal display device according to a first embodiment of the present invention. As shown in FIG. 1, the liquid crystal display device of this embodiment has a light shielding film 2, a transparent electrode 3, an insulating film 4, and an alignment film 6 formed in a desired pattern on a counter substrate 1a.
The insulating film 4 is formed excluding the display region. In addition, the insulating film 4
Is a silicon nitride film, which can be formed by placing a mask on the counter substrate 1a on which the light shielding film 2 and the transparent electrode 3 are formed and depositing it only on a predetermined region by the CVD method. Further, on the transparent electrode 3, an alignment film 6 formed so that its end portion overlaps with the insulating film 4.
Have. The other transparent substrate 1b has a switching element 11, an insulating film 4 for protecting the element, a transparent electrode 3, and an alignment film 6. These two substrates are made to face each other and overlapped with a seal 7 with an appropriate gap, and a liquid crystal 8 is enclosed.
The polarizing plate 9 is attached. When the external drive circuit terminal 5 is connected to the end of the transparent electrode 3 on the transparent substrate 1b with the conductive film 10,
The liquid crystal display device according to the present embodiment can be obtained.

In the liquid crystal display device of this embodiment, since the transparent electrode 3 in the liquid crystal enclosure is completely covered with the insulating film 4 and the alignment film 6, it is not in direct contact with the liquid crystal 8. Therefore, elution of ionic impurities from the transparent electrode 3 to the liquid crystal 8 can be suppressed. Further, since the insulating film 4 is not formed on the transparent electrode 3 in the display area, the insulating film 4 does not cause a voltage drop. By applying the present embodiment, the appearance of display unevenness due to the mixing of impurities can be reduced by about 15% as compared with the conventional example of FIG.

Further, when the insulating film 4 is a silicon oxide film or a multi-layer of a silicon oxide film and a silicon nitride film, the same effect can be obtained. On the other hand, however, when the insulating film 4 is formed of the resin film, the adhesion with the seal 7 deteriorates and the seal 7 peels off. Therefore, it is desirable to use a film of silicon oxide, silicon nitride or the like that can maintain the adhesiveness with the seal 7 as the insulating film 4.

FIG. 2 is a sectional view showing a liquid crystal display device according to a second embodiment of the present invention. In the second embodiment, the light shielding film 2, the coloring layer 12, the transparent electrode 3, the insulating film 4 and the alignment film 6 are formed on the counter substrate 1a. The insulating film 4 was obtained by placing a mask on the transparent electrode 3 and depositing a silicon oxide film by a sputtering method. Since the alignment film 6 is formed so that its end portion overlaps with the insulating film 4, the transparent electrode 3 does not contact the liquid crystal 8. Transparent substrate 1b
The structure on the side is the same as that of the first embodiment, and the transparent electrode is not in contact with the liquid crystal. When the colored layer 12 is formed on the counter substrate 1a for colorization, the insulating layer 4 is formed by the colored layer 12.
The formation temperature is limited, but low temperature film formation is possible by selecting the sputtering method. Also in this embodiment, the same effect as that of the first embodiment was obtained.

[0012]

As described above, according to the present invention, the display areas of the counter substrate and the transparent substrate of the active matrix type liquid crystal display device are oriented films, and the outside of the display area (excluding the connection portion to the external drive circuit) is insulated. Covering with a film has the effect of blocking the transparent electrode from the liquid crystal and suppressing the elution of ionic impurities from the transparent electrode. As a result, it is possible to reduce the occurrence of display unevenness due to voltage fluctuation due to the mixing of ionic impurities in the liquid crystal.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional liquid crystal display device.

4A and 4B are cross-sectional views of the liquid crystal display device disclosed in JP-A-58-178325.

FIG. 5 is a cross-sectional view of the liquid crystal display device shown in Japanese Utility Model Laid-Open No. 19032/1990.

[Explanation of symbols]

 1a Counter substrate 1b Transparent substrate 2 Light-shielding film 3 Transparent electrode 4 Insulating film 5 External drive circuit terminal 6 Alignment film 7 Seal 8 Liquid crystal 9 Polarizing plate 10 Conductive film 11 Switching element 12 Coloring layer

Claims (3)

[Claims] 1. An active matrix liquid crystal display device in which liquid crystal is sealed between a transparent substrate having a transparent electrode having a switching element and a counter substrate having a transparent electrode, wherein the transparent electrode is formed on the counter substrate. 2. A liquid crystal display device having a structure in which a portion other than the display portion is covered with an insulating film, and the display portion is covered with an alignment film for aligning liquid crystals. 2. The liquid crystal display device according to claim 1, wherein the insulating film covering the portion other than the display portion of the counter substrate is a silicon nitride film or a silicon oxide film. 3. The liquid crystal display device according to claim 1, wherein the insulating film covering the portion other than the display portion of the counter substrate has a multilayer structure of a silicon nitride film and a silicon oxide film.