JP2000330116A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregularity in display contrast and an image sticking caused with time in a liquid crystal display device having an insulating film on one substrate, by disposing alignment films having different holding rates. SOLUTION: In the liquid crystal display having a pair of substrates 11A, 11B having transparent electrodes 12, a liquid crystal sealed between the substrates, and an insulating film 13 formed on one substrate 11B to prevent short circuits between the upper and lower substrates, alignment films 14 having mutually different holding rates are arranged. After polyimide alignment films are formed on both of the substrates 11A, 11B, the substrate 11A is calcined at 280 deg.C, while the substrate 11B is baked at 200 deg.C. When the alignment films 14 are baked under the aforementioned production conditions, the substrate 11A has a higher holding rate by >=5% than the substrate 11B. Or, in the process of forming polyimide alignment films on both of the substrates 11A, 11B, an alignment film having 95% holding rate is applied on the substrate 11A, while an alignment film having 70% holding rate is applied on the substrate 11B, and then both are baked. By this method, the substrate 11A has a higher holding rate than the substrate 11B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a liquid crystal display device generally used at present. A pair of upper and lower substrates 1
Transparent electrode films 2A and 2B are pattern-formed on the respective surfaces so as to face the surfaces of A and 1B. Insulating films 3A and 3B are formed on the transparent electrode to prevent a short circuit due to dust or the like generated during manufacturing. The alignment films 4A and 4B are applied on both substrates thus formed, and rubbing is performed to perform alignment.

Further, after forming frame-shaped seals 5A and 5B on one side substrate, the two substrates 1A and 1B are joined at a predetermined interval, and a liquid crystal 6 is sealed in the gap to thereby provide a liquid crystal display element. Is obtained. In the process, usually the insulating film 3
A and 3B are ideal for preventing a short circuit state because they are more symmetrically equivalent in terms of equivalent circuit when disposed on both surfaces of the transparent electrode substrate.

[0004] However, even when the insulating film layer is arranged only on one side, it is possible to suppress the short circuit, and it is advantageous in terms of cost from the viewpoint of the number of manufacturing steps. FIG. 5 shows a liquid crystal panel provided with an insulating layer only on one side. A transparent electrode film 2B, an insulating film 3B and an alignment film 4B are provided on a substrate 1B, and a transparent electrode 2A is provided on an opposing substrate 1A.
A liquid crystal 6 is injected between B by providing an interval between the seals 5A and 5B. Therefore, from the viewpoint of the number of manufacturing steps, a manufacturing method in which an insulating film is applied only to one substrate is also used.

[0005]

However, when the insulating film on one side is formed as described above, an electrically equivalent circuit is not obtained, and the holding ratio on the insulating film side is increased. Therefore, when performing a high-temperature operation test while applying a static waveform or a multiplex waveform to the liquid crystal element,
For example, display contrast unevenness or the like occurs after the end of the 120 h test.

In the display contrast unevenness, since a symmetric electric field is not applied to the liquid crystal display element, a DC component is generated, and an ionic component adhering to the liquid crystal material or the alignment film is applied to the one-side substrate, especially when the It has been clarified experimentally that it is easy to be adsorbed to a place where it has occurred. When this ion component is adsorbed on the alignment film, an electric double layer is formed on the alignment film, and the voltage applied to the liquid crystal differs between the electric double layer portion where the ions are adsorbed and the portion where the ions are not adsorbed. It is observed as unevenness. Therefore, in the related art, when the high-temperature reliability test was performed, the display contrast unevenness over time occurred.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. As described above, a pair of substrates having transparent electrodes and a liquid crystal element in which liquid crystal is sealed between the pair of substrates are provided. Provided is a liquid crystal display element having no display unevenness, characterized in that, in a liquid crystal element in which an insulating film is provided on at least one substrate to prevent a short circuit between upper and lower substrates, alignment films having different holding ratios of the alignment film are arranged.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for manufacturing a liquid crystal display device according to the present invention, an insulating film for preventing short circuit due to the influence of foreign matter or the like generated during manufacturing is formed on a pair of substrates having transparent electrodes. Provided is a liquid crystal optical element in which alignment films having different holding ratios are arranged in a liquid crystal display element to avoid application unevenness or the like generated by applying a voltage.

An embodiment of the present invention will be described below. (Example 1) An example of a liquid crystal display element and a manufacturing method will be described with reference to FIG. ITO (indium oxide or tin oxide) is provided on each of the upper and lower substrates 11A and 11B, which use a pair of glass or the like, facing the surfaces of the substrates.
Is disposed. An insulating film 13 made of SiO2 is provided on the transparent electrode film 12 to prevent a short circuit caused by the influence of dust such as foreign matter generated during manufacturing.
Are formed. After a polyimide alignment film 14 is applied on both substrates formed in this way, it is baked and aligned by a rubbing method.

Further, after a sealing material 15 is formed on a thermosetting resin or an ultraviolet curable resin mixed with a spacer on a one-sided substrate, both substrates are joined at a predetermined interval, and a liquid crystal 1 is inserted into the gap.
A liquid crystal element is obtained by enclosing 6. Here, a substrate 1A and a substrate 11B are formed of a glass substrate 11A on which an insulating film is not formed on one side and a substrate 11B on which an insulating film is formed.
In both cases, after forming the polyimide alignment film, the substrate 11A is baked at 280 ° C., and the substrate 11B is baked at 200 ° C. When the alignment film is baked under such manufacturing conditions, the holding ratio of the 11A substrate is higher than that of the 11B substrate by 5% or more. Example 2 An example of a liquid crystal display device and a manufacturing method will be described with reference to FIG. A transparent electrode film 12 usually made of ITO (indium oxide or tin oxide) is disposed on each of the upper and lower substrates 11 using a pair of glass and the opposing surfaces opposing the surface of 11B. An insulating film 13 made of SiO 2 is formed on the transparent electrode film 12 to prevent a short circuit caused by dust or other foreign matter generated during manufacturing.

After a polyimide alignment film 14 is applied on both substrates thus formed, they are baked and aligned by a rubbing method. Furthermore, after forming a sealing material in which a spacer 15 is mixed with a frame-shaped thermosetting resin or an ultraviolet-curing resin on one side substrate, the two substrates are joined at a fixed interval, and a liquid crystal is sealed in the gap. To obtain a liquid crystal element. Here, in the glass substrate 11A on which the insulating film is not disposed on one side facing the other and the substrate 11B on which the insulating film is disposed, the substrate 11A and the substrate 11B both have a high holding ratio of 95% when the polyimide alignment film is formed. Apply an orientation film with a retention rate,
On the substrate 11B, an orientation film having a low retention of 70% is applied and baked. In this case, the holding ratio of the substrate 11A is higher than that of the substrate 11B. With the above-described manufacturing method, it was possible to avoid display contrast unevenness occurring at the time of application. (Comparative Example) Next, a comparative example of display unevenness and burn-in when the prior art and the present invention are performed will be described. FIG. 2 shows a transmitted light intensity value 22 obtained by converting a change in transmittance when a static waveform 21 is applied to the liquid crystal into a voltage when the substrate 11A and the substrate 11B are performed at the same firing temperature.

As can be seen from FIG. 2, the amplitude change of the transmitted light intensity on the plus side and the minus side is not constant even though a static waveform having a symmetric potential is applied. This is because the waveform applied to the liquid crystal material is in the same state as when a pseudo DC bias is applied because the holding ratio is different only on one side of the substrate despite the symmetry of the voltage applied to the liquid crystal molecules. . When such a liquid crystal display element is continuously driven in a 60 ° C. environment, ions contained in the liquid crystal are easily adsorbed to the alignment film on the surface of the one-sided substrate, resulting in a liquid crystal display element having poor reliability.

FIG. 3 shows a waveform of the liquid crystal display device according to the present invention. FIG. 3 shows a static waveform 31 on the liquid crystal.
Shows the change in the transmitted light intensity 32 when.
Compared with the voltage waveform of the conventional liquid crystal display device, the waveform of the liquid crystal display technology of the present invention has a waveform whose amplitude is symmetric. When the liquid crystal display device of the present invention is continuously driven and tested in a 60 ° C. environment, contrast unevenness and image sticking can be suppressed as compared with the conventional liquid crystal display device.

[0014]

According to the above-described structure, the present invention provides a liquid crystal display device having an insulating film provided on one side of a substrate. A liquid crystal display element that can be suppressed can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device showing an embodiment of the present invention.

FIG. 2 shows the relationship between the applied waveform and the transmitted light intensity according to the prior art.

FIG. 3 shows a relationship between an applied waveform and transmitted light intensity according to the present invention.

FIG. 4 is a sectional view of a conventional liquid crystal display device.

FIG. 5 is a sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Transparent electrode film 13 Insulating film 14 Alignment film 15 Seal 21 Applied voltage 22, 31 Transmitted light intensity 32 Applied voltage waveform

Claims (4)

[Claims] 1. A liquid crystal display device having a liquid crystal sealed between two substrates each having an electrode and an alignment film formed on a surface thereof, and having an insulating film layer between the electrode and the alignment film on at least one of the substrates. A liquid crystal display element, wherein the holding ratios of the alignment films of two substrates are different from each other. 2. The liquid crystal display device according to claim 1, wherein the holding ratio of the alignment film differs by 5% or more. 3. A method of manufacturing a liquid crystal display element, in which a liquid crystal is sealed between two substrates having electrodes formed on the surface, and an insulating film layer and an alignment film formed on at least one electrode layer are provided. 3. The method for manufacturing a liquid crystal display device according to claim 1, wherein a firing temperature of an alignment film formed on one of the insulating layers is different from a firing temperature of an alignment film formed on the transparent electrode. 4. A manufacturing method of a liquid crystal display device, wherein a difference between a firing temperature of the alignment film formed on the insulating layer and a firing temperature of the alignment film formed on the transparent electrode is 20 ° C. or more. Method.