Insulation film coating liquid composition and liquid crystal display device provided with the insulation film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an insulating film coating liquid composition and a liquid crystal display element having the insulating film. More specifically, when forming an insulating film on a transparent electrode of the liquid crystal display element, the insulating film can be fired at a low temperature. The present invention relates to an insulating film coating liquid composition particularly suitable for a color liquid crystal display element.

【0002】

[Conventional technology]

The liquid crystal display element is basically configured by laminating a pair of transparent electrode substrates on which transparent electrodes are formed via a peripheral sealing material and enclosing a predetermined liquid crystal in the cell. In this case, an insulating film is formed on the transparent electrodes in order to secure insulation between the transparent electrodes facing each other.

【0003】

When forming this insulating film, a coating liquid of the so-called sol-gel method has been widely used conventionally. The composition of this coating liquid is a metal alkoxide and a hydrolyzate solution thereof, and silicon, titanium, zirconium and the like are mainly selected as the metal. Of these, titanium is considered to be the most suitable.

【0004】

The main reason for this is that titania obtained by firing alkoxytitanium has a high dielectric constant and a small decrease in drive voltage. Not only that, Titania has a high refractive index of light, which is close to the refractive index of ITO (Indium Tin Oxide), which is a transparent electrode, and makes it possible to achieve the so-called "bone-seeing" phenomenon in which the pixel outline looks thin when not lit. Because it can be made smaller.

【0005】

However, titanium alkoxide has a high decomposition temperature and cannot be converted to titanium oxide unless it is fired at a high temperature of 400 ° C. or higher. However, when the transparent electrode substrate is heated to 400 ° C. or higher, the resistivity of the transparent electrode made of ITO increases. Therefore, by irradiating titanium alkoxide with ultraviolet rays to promote its decomposition and then firing it, it has become possible to fire at a temperature of about 300 ° C.

【0006】

[Problems to be Solved by the Invention]

However, the firing temperature may still be too high even at 300 ° C. That is, for example, when a color filter is attached to a transparent electrode substrate.

【0007】

That is, since the heat resistant temperature of the color filter is 250 ° C. or less, it is difficult to form a good film even by the above-mentioned ultraviolet irradiation method. Further, even when the firing temperature is about 300 ° C., the resistance value of ITO tends to increase slightly, so that a thicker ITO film is required to obtain the same conductivity.

【0008】

[Means for solving problems]

In order to solve such a problem, the present invention is characterized in that titanium peroxide is contained in an insulating film coating liquid composition which is applied to a transparent electrode substrate and forms an insulating film on the transparent electrode. There is.

【0009】

In this case, it is preferable that the titanium oxide contains other metal elements other than titanium and has an alternating bond with the other metal oxide.

【0010】

Further, the present invention comprises a pair of transparent electrode substrates having a transparent electrode and an insulating film formed on the transparent electrode, which are bonded to each other via a peripheral sealing material, and a predetermined liquid crystal is sealed in the cell. The liquid crystal display element is characterized in that the insulating film is formed of an insulating film coating liquid composition containing titanium peroxide.

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, titanium peroxide is a polymer of peroxotitanic acid having a peroxo bond. This titanium peroxide can be obtained by adding hydrogen peroxide to titanium hydroxide and heating at room temperature or 90 ° C. or lower.

【0012】

Titanium hydroxide is produced, for example, by a method of hydrolyzing an inorganic titanium compound such as titanium tetrachloride or ferric sulfate or an organic titanium compound such as titanium alkoxide. Next, hydrogen peroxide is added thereto, and the mixture is stirred and heated to obtain titanium peroxide. Titanium peroxide can also be obtained by directly reacting titanium tetrachloride, titanium sulfate, and titanium alkoxide with a hydrogen peroxide solution.

【0013】

In order to apply this insulating film coating liquid composition to the insulating film of a liquid crystal display element, in order to minimize so-called bone visibility, the refractive index of the film obtained by mixing with a silicon compound, a zirconium compound, etc. and firing is adjusted. It is preferable to optimize.

【0014】

Examples of the silicon compound and zirconium compound include silicon hydroxide (silicic acid), zirconium hydride (zirconic acid), or silicon, alkoxides of zirconium, halides and their hydrolyzates, and mixtures thereof. it can. The mixing ratio of titanium and other metals is appropriately determined according to the refractive index of the film obtained by firing.

【0015】

By the way, it is known that titanium oxide has a photocatalytic action. That is, when exposed to light in a certain wavelength range, organic substances in contact with titanium oxide may be oxidized and decomposed. Therefore, when applied to a liquid crystal display element, display defects may occur due to exposure to light. There is.

【0016】

In order to prevent this, alternating bonds that reduce the homozygotes of Ti-O-Ti and increase the heterozygotes Ti-OM (M is a metal other than Ti) are effective. The reduction of homozygotes can be basically achieved by uniformly mixing the Ti compound as a starting material with the starting material of another metal in advance and then preparing the liquid.

【0017】

This insulating film coating liquid composition is printed on a transparent electrode substrate by an offset method flexographic printing method or the like as a solution of a polyhydric alcohol having a high boiling point and a high viscosity or a derivative thereof.

【0018】

The drying temperature for the main purpose of removing the solvent after printing is usually in the range of about 50 to 150 ° C. Firing is a process performed to convert titanium peroxide to titanium oxide and other metal compounds such as silicon to metal oxides, and the firing temperature is 150 to 300 ° C, especially 200 to 250. It is in the range of ° C.

【0019】

[Example]

<< Example 1 >> 100 ml of a 50% solution of titanium tetrachloride (manufactured by Sumitomo Cytics Co., Ltd.) was diluted 70-fold with pure water. 2.5% aqueous ammonia was added to this solution to react it so that the pH became 2, and after leaving it to stand, the supernatant was discarded. Remaining Ti (OH) orthotitanium₄The gel was repeatedly washed with water and purified.

【0020】

This gel is suspended in pure water again and TiO₂A 35% hydrogen peroxide solution was added separately to a slurry having a concentration of 2% by weight, and the mixture was stirred at 5 ° C. for 10 hours and then stirred at room temperature for 7 days to obtain yellow transparent titanium peroxide. And the silica sol "Snowtex EG-ST (trade name)" (SiO)₂20% solid content, ethylene glycol solution, manufactured by Nissan Chemical Industries, Ltd.) after firing, TiO₂: SiO₂Was mixed so that the weight ratio was 1: 1 to obtain an inorganic insulating film coating liquid.

【0021】

Separately from this, a pair of transparent electrode substrates (multi-faceted mother substrate) formed by forming transparent electrodes made of ITO in a predetermined pattern on a glass substrate are prepared, and the above-mentioned inorganic insulating film coating is applied to each electrode surface side. The liquid was printed. Next, each of the transparent electrode substrates was dried at 100 ° C. for 10 minutes, then heated at 250 ° C. for 30 minutes and fired to obtain an insulating film of about 500 Å of titanium oxide-silicon oxide.

【0022】

After that, a polyimide-based alignment film was formed according to a conventional method, and a rubbing alignment treatment was performed. Then, an in-plane spacer was sprayed, and two transparent electrode substrates were bonded and crimped via a peripheral sealing material to prepare a liquid crystal display cell. After vacuum-injecting the liquid crystal into the cell, each liquid crystal display cell was separated into individual units to complete the liquid crystal display element. When this liquid crystal display element was turned on, a display without short-circuit defects was obtained between the substrates.

【0023】

<< Example 2 >> A color liquid crystal display element was obtained in the same manner as in Example 1 except that a transparent electrode substrate with a color filter was used as the transparent electrode substrate. When this color liquid crystal display element was turned on, a display without short-circuit defects was obtained between the substrates as in the first embodiment.

【0024】

[Effect of the invention]

As described above, according to the present invention, the following effects are obtained by using the insulating film coating liquid containing titanium peroxide.

【0025】

Since a dense insulating film can be obtained by low-temperature firing, a high-quality liquid crystal display element without a short circuit between substrates can be obtained, which is particularly suitable for a color liquid crystal display element. Since the insulating film is low-temperature curable, both the equipment cost and the running cost can be reduced. A highly reliable insulating film can be obtained due to the strong adhesion to the substrate, which is a characteristic of titanium peroxide.