JPS59131911A - Liquid crystal electrooptic device - Google Patents

Abstract

PURPOSE:To improve remarkably orientation characteristic of a liquid crystal having a chiral smectic C phase or H phase and to obtain a good contrast characteristic by coating a polyimide resin on the surface on the liquid crystal layer side of two sheets of upper and lower glass substrates to be sealed therein with said liquid crystal and curing said resin, then rubbing and combining the rubbing direction on the two glass substrates in prallel in the same upper and lower directions. CONSTITUTION:Transparent electrodes 23 are provided on the liquid crystal layer 25 side on upper and lower glass substrates 21, 22, and furthr a polyimide resin 24 is coated thereon and is rubbed in parallel with a bleached fabric or the like by a rubbing machine. The substrates 21, 22 are further pasted together at a suitable space so as to have the same rubbing direction. The polarizing plates are further set on the top and bottom of the cell with the optical axis 14 of the one polarizing plate deviated to an angle psi0 of about 22.5 deg. relative with the rubbing direction so as to intersect orthogonally with the optical axis 13 of the other polarizing plate. When an electric field is impressed on the cell, an electrooptic device wherein the light is passed or interrupted and is thus turned on and off is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal electro-optical device, and more particularly to a method for aligning liquid crystal in a liquid crystal electro-optical device that rapidly responds to polarity due to a strong bond between applied voltage and molecular orientation. Used in equipment.

It is particularly used in devices that require small size and low power consumption, such as clocks and calculator display devices. These devices utilize the alignment effect of dielectrics in nematic, smectic, and cholesteric phases.The coupling between the applied electric field and liquid crystal molecules in these methods is quite weak, so the electro-optical response time of the above devices is extremely slow. Become something. However, liquid crystal electro-optical devices are low voltage, low power consumption, small size,
Because it can be made thinner, it is considered the most promising non-emissive electro-optical device. Therefore, if the slow response speed and amorphous property of liquid crystal electro-optical devices can be improved, a significant expansion of applications can be expected.

Under these circumstances, an attempt was made to use chiral smectic liquid crystal as an electro-optical element in Japanese Patent Application Laid-open No. 56-IO72.
16. According to this, chiral smectic C- or H-phase liquid crystals are generally said to be ferroelectrics with an electric dipole density, and furthermore, the electric dipole density is perpendicular to the direction of molecular inclination. be. The presence of electric dipoles within these chiral smectics creates a strong coupling between the applied electric field and molecular orientation.

This coupling is stronger than that obtained by dielectric anisotropy. Furthermore, the bond is polar and the preferred orientation of the electric dipole density is parallel to the applied electric field. As a result, the preferred orientation electric dipole can be reversed by reversing the polarity of the applied electric field, so that reversal of the electric field can be effectively used to control molecular orientation. This results in an improvement of 100% compared to conventional electro-optical devices that use liquid crystals.
The response speed is 0 to 10,000 times faster and sufficient inherent nonlinearity can be obtained. It is also described that ferroelectric smectic liquid crystals require favorable orientation, unlike crystalline ferroelectrics. Furthermore, the orientation method is decyloxybenzylidene p'-amino 2methylbutyl cinnamate (DOB
In the case of the compounds AMBO) and hexyloxybenzylidene p'-amino 2chloropropylcinname) (HOBAOPc), they are oriented by an intact glass or an intact tin oxide layer. Also, when a smectic phase is formed from a nematic phase, when a sufficient magnetic field is applied, it has an average molecular orientation along the magnetic field. Furthermore, as a method for achieving bistability more reliably, a rectangular ridge is provided on two glass substrates as shown in FIG. 1, and each glass substrate is fixed at a deflection angle of 2ψ of the liquid crystal.

A method for orienting two liquid crystals by coordinating them so as to form an angle is described. However, our experimental results show that when using a glass substrate that is not subjected to orientation treatment, each domain is randomly oriented, making it impossible to obtain sufficient contrast.

Furthermore, in the method of orientation in a magnetic field, when a magnetic field is applied, it becomes a monodomain and is oriented in one direction, but
Since it requires a G magnetic field, a large magnetic field generator is required, which is not practical. Furthermore, a ridge is provided on the glass substrate, and the deflection angle of the cone is 2ψ. Even with the method of shifting the glass substrate by the same angle as the above, almost no contrast could be obtained.

Further, recent literature reports have not shown any good method for aligning chiral smectic liquid crystals outside of a magnetic field.

The present invention has been made in view of the above points, and provides a simple and practical method for aligning chiral smectic liquid crystals. This makes it possible to effectively utilize the excellent response speed of chiral smectic liquid crystals.Polyimide resin is coated on the liquid crystal layer side surfaces of two upper and lower glass substrates that encapsulate liquid crystals having 0, that is, chiral smectic C phase or H phase. is applied and rubbed after curing, and the rubbing directions on the two glass substrates are parallel to each other in the same direction above and below. This significantly improves the alignment of chiral smectic liquid crystals and provides good contrast characteristics. This is what made it possible.

FIG. 2 is a simplified diagram of the configuration of the present invention. In the state of smectic physiognomy, the rubbing directions are the same up and down, so the liquid crystal molecules are oriented with their long axes aligned in the rubbing direction. When the temperature decreases and it transitions to the smectic C phase, it becomes a cone-shaped molecule with chirality and 2ψ0 appears. This 2ψ increases as the temperature decreases. gradually increases in size and extends up to 50°. The liquid crystal molecule 11 is this 2ψ. It has degrees of freedom within the angle of (indicates chirality). Furthermore, since the electric dipole and the long axis of the liquid crystal molecules are perpendicular to each other, when a positive or negative electric field is applied from the outside, the cone stabilizes in the linear state 11 or 15, where it swings the most.

Therefore, by aligning the optical axes of the polarizing plates 13 or 14 in one of these two stable directions and orthogonal to the other, and applying an electric field, an electro-optical device can be created in which light passes through or is blocked and is turned on or off. Also, to obtain the ideal contrast, 2ψ0
is 45°. This can be set by the temperature of the liquid crystal.

Hereinafter, the present invention will be explained in more detail according to Examples.

Example FIG. 3 schematically shows the cell structure of the electro-optical device of the present invention.

21 and 22 are upper and lower glass substrates.

A transparent electrode 23 is provided on the liquid crystal layer 25 side on this substrate, and a polyimide resin (Drainice 200 manufactured by Toshisha Co., Ltd.) is further applied thereon.
0#) Apply approximately soX amount of 24, rub it in parallel with a drying cloth etc. using a 4-ping machine, and then apply 2
The liquid crystal layer 25, which is made by laminating two glass substrates at appropriate intervals (01 to 5.0 μm) so that the rubbing directions are the same as shown in FIG. 4, is a DOBAMBC or HOBAOPO liquid crystal. Further, polarizing plates were set above and below this cell, and the optical axis of one polarizing plate was shifted at an angle of about 22.5 degrees with respect to the rubbing direction, and the optical axis of the other polarizing plate was set perpendicular thereto.

When a DQBAMB liquid crystal was used in such a cell at a temperature of 82° C., the response speed was 10 μm and the contrast ratio was 13:1 depending on the on/off of ±IDV. Further, when the temperature was 70° C., the response speed was 16 μm and the contrast ratio was 15:1 using the HOBACPC liquid crystal with ±5 V on/off switching. Furthermore, in the non-oriented sample and the sample shown in FIG. 1, which were used for comparison, the response speed could hardly be measured, and the contrast ratio was 1 to 1.3:1, which could hardly be confirmed.

Further, the contrast ratio of the sample according to the present invention without coating the polyimide resin was about 5:1.

As described above, according to the present invention, chiral smectic liquid crystal can be easily and well aligned, so that liquid crystal electro-optical devices such as electronic shutters and high-density television screens that utilize its high-speed response can be produced inexpensively and easily. is possible.

[Brief explanation of drawings]

FIG. 1 is an enlarged schematic diagram showing an example of a conventional orientation method. FIG. 2 is a simplified diagram of the configuration of the method of the invention, and FIG. 3 is a schematic diagram of the cell structure of the invention. FIG. 4 is a schematic diagram of the rubbing direction of the present invention. 1... Upper glass substrate ridge 2... Lower glass substrate ridge 3... Average ridge direction of upper glass substrate 4... Average ridge direction of lower glass substrate 11... Liquid crystal molecules 12... Rubbing direction 13, 14...Polarizing plate optical axis 15...2 Stable position 21...Upper glass substrate 22...Lower glass substrate 23...Transparent electrode 24...Polyimide resin layer and rubbing surface 25...
Liquid crystal layer 31...average rubbing direction or more Applicant Suwa Seikosha Co., Ltd. Agent Patent attorney Tsutomu Mogami (9) Figure 1 Figure 2 Figure 3 Figure 40

Claims (1)

[Claims] A liquid crystal having a chiral smectic C phase or a smectic H phase is encapsulated in two glass substrates on which electrodes have been provided and which have been subjected to alignment treatment, polarizing plates are provided vertically above and below the two glass substrates, and further In a liquid crystal electro-optical device in which light is turned on and off by passing or blocking light by applying an electric field to the electrodes and reversing the polarity, the method for aligning the two glass substrates is to apply a polyimide resin and rub 1° after baking. 1. A liquid crystal electro-optical device characterized in that the rubbing directions of two glass substrates are parallel.