JPS6170528A - Liquid crystal cell - Google Patents

Abstract

PURPOSE:To easily form a monodomain of a smectic phase and to obtain a liquid crystal cell having a good contrast by arranging a liquid crystal cell using a smetic liquid crystal of ferro-electricity with a comb-shaped exothermic resistor. CONSTITUTION:The comb-shpaed exothermic resistor composed of In2O3 etc. and an electrode impressing a voltage are formed on two insulating base plates made of a transparent glass respectively, and an insulating film of SiO2 is vapor - deposited on the resistor and the electrode, and then an orientation film is formed on the insulating film with the aid of a horizontal orientation treating agent. The smectic liquid crystal of ferro-electricity such as P- decyloxybenzylidene-p-amino-2-merbutylcinnamate is sealed in a space between the base plates. The monodomain formation of the chiral smectic C phase from an isotropic liquid facilitates by arranging the above-describe heating element, thereby obtaining the liquid crystal cell having an excellent contrast and a good orientation state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid crystal display device, and particularly to a liquid crystal cell using ferroelectric liquid crystal.

(Structure of conventional example and its problems) In order to control the alignment of a conventional nematic liquid crystal cell, l-axis alignment treatment was performed by rubbing or oblique deposition of a dielectric material.

However, smectic liquid crystals have high viscosity and no fluidity, so once a layer is formed and fixed at the interface, an extremely large force is required to move the entire layer.

As a currently well-known orientation treatment method, a cell subjected to rubbing or oblique evaporation is injected in an isotropic liquid state while being held at a high temperature in a heat treatment furnace, etc., and then the smectic A phase is crystal-grown over a long period of time. After that, the temperature is slowly lowered to a smectic phase (for example, chiral smectic C phase, chiral smectic F phase, etc.) exhibiting a predetermined ferroelectric state. This method has the disadvantages that it takes a very long time to obtain the desired orientation state and that delicate temperature control is difficult.

(Object of the Invention) The present invention is characterized in that a smectic liquid crystal composition exhibiting ferroelectricity is sealed in a liquid crystal cell equipped with a comb-shaped heating resistor. The object of the present invention is to provide a liquid crystal cell having a good monodomain phase by heating a smectic liquid crystal exhibiting dielectric properties with the above-mentioned comb-shaped heating resistor.

(Structure of the Invention) Typical examples of smectic liquid crystals exhibiting ferroelectricity include chiral smectic C phase (SmC''), chiral smectic F phase (SmF''), and chiral smectic F phase (SmI'').

Cells using these smectic liquid crystals exhibiting ferroelectric properties exhibit extremely fast response times compared to conventionally used twisted nematic type cells, and have microsecond response times that cannot be achieved with twisted nematic type panels. It is to show that. Further, normally, a smectic liquid crystal has several phases in which the liquid crystal molecular arrangement is slightly different depending on its temperature range. For example, if a liquid crystal compound having Sc* is heated to become an isotropic liquid and then cooled, it generally exhibits the following phase change.

Isotropic liquid → Smectic A phase → 5IIlG” → SmH
”→Crystalline smectic A phase (SmA) has no regularity in the molecular position within the layer, and the director is perpendicular to the plane of the layer.The structure of SmA is usually a long diamond-shaped structure called a fan-shave structure. , has a slightly distorted organization.

When changing from SmA to SmC''.

Stripes appear evenly spaced within each rhombus of fanciable tissue. By utilizing such a phase change, the desired smectic phase can be monomained. For this purpose, temperature control with an accuracy of about 0.1° C. is required, and it is not possible to obtain monodomains of sufficient size using conventional methods of controlling temperature from the outside.

The present invention enables effective temperature control by integrating a resistance heating element for temperature control into a liquid crystal cell in a comb shape.

(Explanation of Examples) Next, examples of the present invention will be described.

A comb-shaped heating resistor mainly composed of indium oxide and a voltage application electrode are formed on two transparent Garay insulating substrates, and an insulating film of silicon oxide is formed by vapor deposition, and a horizontal An alignment film is formed by treatment with an alignment treatment agent. The substrates made in this way are bonded together using a predetermined method to make a liquid crystal cell, in which ρ-decyloxybenzylidene-pl-amino-
2-Methylbutyl cinnamate (DOBAMBC), a liquid crystal compound having the following chemical structural formula, is sealed.

Then, a pulse current is passed through the heating resistor to heat it to 117°C or higher, and once it becomes an isotropic liquid, about 0.0°C per minute.
The temperature is gradually lowered to 117° C. by 1° C. to form SmA and a fan-shaved structure.

Then, cooling is further performed at the above rate, and from SmA to Sm
The temperature is lowered to several degrees lower than the transition temperature (93°C) to C", and stripe domains are formed in the fan shive structure. By doing this, a uniform smectic liquid crystal with a monodomain structure of "Sac" is formed. A cell can be created.

Although the horizontal alignment in the above embodiments was carried out using an alignment treatment agent, other alignment treatments such as rubbing, oblique vapor deposition, and methods using spacer edges are also effective. Further, if the cooling rate is about 0.5° C. per minute or less, good monodomain formation is possible, and good liquid crystal cells can be obtained including the above examples.

On the other hand, the resistance heating element of the present invention has a comb-shaped shape, and it is possible to control the temperature in accordance with the production rate of monodomains, and in particular, when transitioning from an isotropic liquid to SnA, rod-shaped islands of Sa+A are formed. The degree to which the growth of (batone) is restricted to the glass interface is very small. That thing is SmC”
The comb-shaped resistance heating element of the present invention is highly effective.

(Effects of the Invention) By integrating the comb-shaped resistance heating element of the present invention into a liquid crystal cell, it is possible to promote the growth of batonnet.

Therefore, it is possible to easily form the desired smectic phase into a monodomain, and it is possible to provide a ferroelectric smectic cell with a good orientation state. A liquid crystal display device using such a cell has good display contrast and is of great industrial value.

Claims (1)

[Claims] A liquid crystal cell using a smectic liquid crystal exhibiting ferroelectricity, characterized by being equipped with a comb-shaped heating resistor.