JPS5847686B2 - Orientation treatment method for liquid crystal display glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for aligning glass for liquid crystal display.

Various display systems are known for liquid crystal display devices, and nematic liquid crystal is particularly being put into practical use as an electro-optical display device.

There are several display principles using nematic liquid crystals, but they can be divided into the following two types.

1. Light scattering caused by nondestructive disturbance of nematic liquid crystal domains by ions traveling through the liquid crystal layer by applying an electric field is used for display.

2. The birefringence of the molecules in the liquid crystal layer is controlled by an electric field, and in combination with a polarizing filter, it has a display function.

There are two types of nematic liquid crystals used in electro-optical displays, one with positive dielectric anisotropy and the other with negative dielectric anisotropy, and principle 1 is used.

Liquid crystal compositions have negative dielectric anisotropy, and those that utilize the second principle are mainly liquid crystal compositions that have positive dielectric anisotropy.

In a nematic liquid crystal with positive dielectric anisotropy, the direction of the electric dipole substantially coincides with the long axis direction of the molecules, and also in the long axis direction or the optical axis direction of the molecules.

Therefore, by applying an electric field, the long axis of the molecule aligns with the direction of the electric field.

On the other hand, a liquid crystal with negative dielectric anisotropy is one in which the direction of the electric dipole and the direction of the long axis of the molecules are orthogonal.

The nematic liquid crystal composition to be applied in the present invention has a positive dielectric anisotropy of 1, and the principle of operation of this display is to cover the glass surface with gauze, absorbent cotton, etc. in order to make the thin layer of the nematic liquid crystal composition take a twisted alignment. He was performing a rubbing operation.

When a liquid crystal is sandwiched between two pieces of glass that have been rubbed, the liquid crystal molecules in contact with the transparent electrode are aligned in a direction that makes the rubbing direction coincide with the long axis direction.

Therefore, the nematic liquid crystal parabolic thin layers of the upper and lower glasses are arranged in a continuous manner with exactly 900 twists.

However, the conventional rubbing operation is now applied directly to the glass.

Alternatively, there are methods such as applying lecithin or silicone grease to the glass surface, treating the glass with acid, adding benzoic acid derivatives, certain polyamides, etc. to the liquid crystal, but these methods do not necessarily ensure that the liquid crystal molecules are arranged uniformly over the entire surface of the glass. However, there is a problem in that coating materials and additives adversely affect the life of the liquid crystal.

The present invention solves this problem and eliminates the decrease in yield due to poor orientation by applying a mixture of one or more of polyvinyl alcohol and polyvinyl acecool to the glass surface before rubbing and melasin for crosslinking. A thin film is coated on the glass surface by applying and baking a solution containing resin at a solid content ratio of 100:0.5 to 100:40, and then rubbing in a certain direction with gauze, absorbent cotton, etc. to form this thin film. Due to its plasticity, various long, smooth scratches are formed to encapsulate the liquid crystal, allowing it to be blended well.

Even with polyvinyl alcohol and polyvinyl acecool alone, the initial orientation is relatively good, but the moisture resistance is poor and long-term stability is compromised, so this has been improved by adding melasin resin for crosslinking, and the blending ratio is 0.5 ~ The reason why there is a range of 40 is because the effects of blending vary depending on the material of the melasin resin and the firing conditions.The effect of improving moisture resistance appears when the blending ratio of the crosslinking melasin resin is at least 05, and the blending ratio is 40.
This is because, when the temperature exceeds that level, the adhesion of the glass deteriorates even if the firing conditions are changed.

The details of the present invention will be explained below according to Examples.

Example 1 Glass was immersed in a 2% aqueous solution containing polyvinyl butyral and melasin formaldehyde resin mixed at a solid content ratio of 100:10, and then fired at 110° C. for 30 minutes.

This was rubbed in a certain direction with gauze and a nylon film (softening point: about 190° C.) was used as a spacer and thermocompression bonded to assemble the cell.

Liquid crystal was injected into this cell, the injection port was sealed, and the orientation of the liquid crystal was examined. As a result, only 2 out of 1000 cells suffered from poor alignment.

Compared to the conventional method of directly rubbing glass, the yield has been greatly improved.

Example 2 After applying an alcohol solution containing a mixture of polyvinyl alcohol and methylol melamine resin at a solid ratio of 100:20 to a glass surface using a spinner (3000 rpm 15
seconds), 1. After baking at 20°C for 45 minutes, a cell was assembled in the same manner as in Example 1, and a liquid crystal was sealed, and the initial alignment and long-term alignment were compared with those in which the glass surface was rubbed directly and the one in which only polyvinyl alcohol was coated and then rubbed. The result after adjustment was as shown in Table 1.

As described above, the material according to the present invention exhibits excellent initial orientation and long-term stability, and is extremely effective in practical use.

Moreover, this effect cannot be seen in any combination of polyvinyl acecool resin and crosslinking melamine resin other than those in the examples.

Claims (1)

[Claims] 1 Coating a glass surface with a substance containing a mixture of one or more of polyvinyl alcohol and polyvinyl acetal and a crosslinking melamine resin in a solids ratio of 100:0.5 to 100:40. A method for aligning liquid crystal display glass, which is characterized by forming an extremely thin directional film by rubbing in the same direction.