JPH0769545B2 - Liquid crystal display element manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a liquid crystal display device having an alignment film having a high liquid crystal alignment ability, and in particular, the alignment film shows high alignment properties. The present invention relates to a method of manufacturing a liquid crystal display device which is made of a liquid crystal polymer and has high contrast and high quality.

[Conventional technology]

As the alignment film used in the conventional liquid crystal display element,
There are those obtained by rubbing a polymer thin film such as polyimide, or an oblique vapor deposition film of silicon oxide, and an alignment film using a liquid crystal polymer has been proposed.

Japanese Patent Laid-Open No. 61-42618 discloses a liquid crystal display device in which a liquid crystal polymer is aligned by a magnetic field and used as an alignment film.

[Problems to be Solved by the Invention]

However, the method of aligning a liquid crystal polymer by a magnetic field is not suitable for industrialization. Because in order to align the liquid crystal molecules in parallel, the liquid crystal polymer must also be aligned in parallel to the glass surface, but when the glass substrate becomes large for a large area display, a very strong magnetic field is required,
This is because current magnets cannot achieve this.

The present invention has been made in view of the circumstances of the prior art as described above, and has an alignment film made of a liquid crystal polymer having uniform alignment over the entire surface even in a large screen, and has high contrast and high contrast. It is an object of the present invention to provide a method for manufacturing a liquid crystal display device capable of displaying quality.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, an alignment film is composed of a liquid crystal polymer, and the alignment film is subjected to an alignment treatment by a method such as rubbing, and then heat treated at a liquid crystal temperature of the liquid crystal polymer. Use it as a solution.

Hereinafter, the present invention will be described in detail.

In the present invention, as the liquid crystal polymer material used for the alignment film, a thermotropic liquid crystal polymer is used, and a thermotropic liquid crystal polymer showing a nematic phase at high temperature is particularly preferably used. More preferably, a crystalline liquid crystal polymer is used. The liquid crystal polymer of the present invention comprises Hoechst
It may be a wholly aromatic type such as Vectra type manufactured by Celanese, or may be a type in which a bent chain is inserted between aromatic rings such as X7G type manufactured by Eastman Kodak. Liquid crystal polymers of these types are generally difficult to dissolve in a solvent, but it is known that the solubility is improved by introducing a non-linear molecule or a halogen substituent. Also, the solubility can be controlled by adjusting the molecular weight.

Generally, it is shown in JP-A-59-62630 and the like that a liquid crystal polymer is made to have high elongation and high strength by being reheated at a liquid crystal temperature after being spun. The present invention is based on the finding that it is possible to similarly enhance the orientation of a thin film of a liquid crystal polymer formed on a substrate such as glass by performing heat treatment.

As a specific manufacturing method of the liquid crystal display device according to the present invention, first, a known coating method of a dilute solution of a liquid crystal polymer on a glass substrate in advance, for example, a spin coating method, a roll coating method, an offset printing method, a screen printing method, Alternatively, a thin film of a liquid crystal polymer is obtained by applying by a dip coating method and drying the solvent. Then, the liquid crystal polymer film thus formed by coating is aligned in a certain direction by an alignment treatment method such as rubbing, and then the substrate is heated preferably under nitrogen reflux in the liquid crystal temperature range of the liquid crystal polymer. A liquid crystal cell is formed from the two substrates thus treated so that the alignment treatment directions are orthogonal to each other so as to have a constant cell thickness, and, for example, a nematic low-molecular liquid crystal is injected to obtain a desired liquid crystal cell. A liquid crystal display device can be obtained.

As the above-mentioned orientation treatment, flow, shear stress, temperature gradient method and the like can be used other than rubbing. A heat treatment time of about 5 to 10 minutes is sufficient.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples illustrated herein.

(Example 1) As a liquid crystal polymer for an alignment film, a Vectra-based material manufactured by Hoechst Celanese was used. This liquid crystal polymer is 297 ℃
It shows a liquid crystal phase up to 326 ° C. A 2 wt% N tylpyrrolidone solution of this polymer was prepared and applied on a glass substrate having a transparent electrode (ITO) with a spin coater at a rotation speed of 1500 r.ms for 30 seconds, and then dried at 200 ° C. for 1 hour. About 1
An alignment film with a thickness of 00 nm could be obtained. After rubbing this alignment film with a nylon cloth in a certain direction, the birefringence of the alignment film was measured with a birefringence measuring device of Oak Manufacturing Co., Ltd.
The birefringence of

When this substrate was heat-treated at 300 ° C. for 10 minutes and the birefringence was similarly measured, it was found to increase to 12.2 nm.

The two substrates thus obtained were superposed in parallel with each other with a 9 μm spacer so that the orientation directions were orthogonal to each other, and then 0.1 wt% of cholesteric nonanate was used as a chiral agent.
A liquid crystal cell was prepared by injecting the added nematic liquid crystal (manufactured by ZLI1565 Merck). When a rectangular wave of 60 Hz was applied to this liquid crystal cell, an optical change was observed at a threshold value of 1.9V. This optical change reached 90% saturation at 2.7V.

(Example 2) The alignment film obtained by forming in the same manner as in Example 1 was rubbed with a nylon cloth. At that time, the distance between the rubbing roll and the substrate was changed to 1.0, 1.1, 1.2, 1.3 and 1.4 mm. Furthermore, some substrates were heat-treated at 300 ° C. for 10 minutes. A nematic liquid crystal in which these substrates were heat-treated or not heat-treated, and those not heat-treated were stacked in parallel through a 9 μm spacer, and then 3% by weight of a dichroic dye was added. (ZLI1565) was injected into a liquid crystal cell. When the dichroic ratio of these liquid crystal cells was measured,
It became like 1. The dichroic dye was reddish purple, and the dichroic ratio was measured at a central wavelength of 550 nm.

As shown in Table 1, the heat-treated product exhibited a higher dichroic ratio than the untreated product, and was not significantly affected by the change in the rubbing conditions, showing a high dichroic ratio.

〔The invention's effect〕

As described above, according to the present invention, even with a large screen, the entire surface is uniform and has an alignment film with a high degree of alignment,
It is possible to obtain a liquid crystal display device capable of performing high-quality liquid crystal display with high contrast even on a large screen. Further, the formation of the alignment film in the present invention may be performed by subjecting a thin film made of a liquid crystal polymer to alignment treatment and then heat treatment, which has an advantage of being industrially advantageous.

Claims (1)

[Claims] 1. A method of manufacturing a liquid crystal display device having an alignment film, comprising forming a thin film of a liquid crystal polymer on a substrate, subjecting the thin film to an alignment treatment, and then a temperature range showing liquid crystallinity of the liquid crystal polymer. A method for manufacturing a liquid crystal display element, which comprises heat-treating to form an alignment film.