JPS58176623A - Electrooptic device - Google Patents

Abstract

PURPOSE:To control a background part and to speed up response, by using a ferroelectric smectic liquid crystal having a liquid-crystal layer whose molecular axes are arrayed in a specific direction nearly parallel to a substrate surface, and providing an electrode for energizing the whole liquid-crystal layer and an electrode for energizing the layer partially. CONSTITUTION:Smectic liquid crystal is applied with orienting process over the surface of the substrate to obtain a single domain. Transparent substrates 1 and 1' are provided with entire-surface electrode films 2 and 2' for energizing the whole liquid crystal and patterned partial electrode films 2 and 2' for energizing only specific parts; and insulating films 5 and 5' are sandwiched between the both. A surface contacting the liquid crystal is applied with orienting process. A polarizer is used on an external-surface side of the substrate when necessary. A DC voltage is applied to the entire-surface electrode to form a uniform background. Then, a DC voltage having the opposite polarity is applied to the partial electrode according to a display pattern to obtain different display from the background. The polarity of the applied voltage is selected to obtain positive or negative display.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optical device using ferroelectric liquid crystal,
The present invention relates to an electro-optical device that is sometimes suitable as a display device.

Conventionally, liquid crystal materials such as nematic liquid crystals and cholesteric liquid crystals have been used in electro-optical devices mainly used as display devices. As shown in FIG. 1(1), an electro-optical device used as such a display device has an electrode pattern 2. corresponding to a pattern for desired display.
The liquid crystal layer 3 is sandwiched between the substrates 1.1' and 2' formed thereon;
As shown in FIG. 1 (2), by applying an electric field to the overlapping part of the electrode patterns of the two substrates, a state different from the background part is created and the pattern is displayed.

However, in such conventional electro-optical devices, it is not possible to apply an electric field to the background portion, so the state of the background portion cannot be controlled, and the optical response speed to switching of electrical signals is The problem is that it is slow compared to luminescence and the like.

Smectic liquid crystals have also been proposed for application as thermo-optical devices that write and erase data using thermal energy, but the optical response speed is comparable to the electro-optical device described in miJ, and the device is expensive. There is a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electro-optical device that quickly responds to an electric signal and has a function of controlling the state of a background portion.

In order to achieve the above object, the present invention has a means for sandwiching a liquid crystal layer between two transparent substrates having transparent electrodes and disposed so that the transparent electrodes face each other, and applying an electric field to the liquid crystal layer. In the electro-optical device provided with the liquid crystal layer,
The transparent electrode is composed of a composition containing a smectic liquid crystal exhibiting ferroelectricity whose molecular axes are substantially parallel to the substrate surface and aligned in a substantially constant direction, and the transparent electrode includes an electrode film that excites the entire liquid crystal layer and a liquid crystal layer. It consists of an electrode film that excites only a predetermined portion of the electrode. An insulating film is sandwiched between the electrode films.

Smectic liquid crystals exhibiting ferroelectricity used in the present invention include a chiral smectic C phase and a chiral smectic H phase. This smectic liquid crystal has a layered structure common to smectic liquid crystals, but
It is said that the direction of the liquid crystal molecular axes changes in each layer, and the molecules are arranged as if they were drawn in a spiral with the helical axis perpendicular to the layer, and this helical structure gives rise to ferroelectricity. It is thought that it shows. A material exhibiting ferroelectric ridges responds to a direct current electric field as a ferroelectric material, and reversing the direction of spontaneous polarization and rearranging it according to the direction of the electric field is
This is well known from the example of ferroelectric crystals. In the case of smectic liquid crystal, the above-mentioned helical axis dissolves,
The long axes of the liquid crystal molecules are rearranged perpendicular to the direction of the electric field and at an angle corresponding to the material-specific angle (hereinafter referred to as tilt angle θ) with respect to the helical axis before being excited. Note that the tilt angle θ is
The direction is reversed depending on the direction of the electric field. The smectipack liquid crystal used in the present invention is mainly a Schiff base type liquid crystal as shown below.

p-hexyloxybenzylidene-p'-
amino-2-methylbutyl-cinna
mate (HOBAMBC) p-octy 1oxybenzyl 1dene-
p'-am 1no1-2-methylbutyl-
cinnamate (COBAMBC) p-decy 1oxybenzy11dene-p'
-amino-2-methylbutyl-cinn
amateCDOBAMBC) p-dodecy 1oxybenzy 11dene
-p'-amino-2-methylbutyl-c
innate (DDOBAMBC) p-tetridecyloxybenxy order dene
-p'-ami no-2-methylbutyl-
clnnnamate (TDOBAMBC) The smectic liquid crystal of the present invention is subjected to so-called single domain formation in which the helical axis direction of the liquid crystal is aligned in a certain direction. By doing so, ferroelectric rearrangement can produce large optical changes. As a result, a device with a large modulation degree can be realized and can be applied to many fields. A single domain in which the helical axis direction is aligned in a constant direction over a certain area as described above can be achieved by performing alignment treatment on the surface of the substrate in contact with the liquid crystal.

According to experiments by Akira Motomoto et al., some of the methods used to control the alignment of conventional nematic liquid crystals and cholesteric liquid crystals are applicable to the single domain structure of the present invention, in which the molecular axes are aligned parallel to the substrate surface. It is confirmed that you will get it. In the present invention, liquid crystal molecules are arranged parallel to the substrates by subjecting the surfaces of the substrates to a soft rubbing treatment and combining two substrates so that the rubbing directions are parallel to each other.

In this case, by providing a polyimide thin film on the substrate surface in advance, the uniformity of orientation could be improved.

The liquid crystal materials exemplified above all have spontaneous polarization in a direction perpendicular to the long axis of the liquid crystal molecules, so when an electric field is applied, the direction of the long axis of the liquid crystal molecules is perpendicular to the direction of the electric field. Therefore, the displacement of the product molecules by arranging the helical axes parallel to all the substrates and applying an electric field that moves the liquid crystal laterally only requires changing the direction of the molecular axes within the same plane. It can operate at low pressure and respond quickly.

The above liquid crystal is used in combination with a dichroic dye if necessary. As such dichroic dyes, materials that have conventionally been used in nematic liquid crystals and cholesteric liquid crystals for the electro-optic effect collectively called the guest-host effect are used, such as anthraquino/derivatives, azo derivatives, diazo derivatives, and merocyanine. Derivatives, tetrazine derivatives, etc. may be used alone or in combination of two or more.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention. In FIG. 2, parts corresponding to those in FIG. 1 are given the same reference numerals.

Each of the transparent substrates 1, 1' includes a full-surface electrode film 4, 4' for exciting the entire liquid crystal, and a partial electrode film 2, 2' patterned according to the display pattern for exciting only a predetermined portion of the liquid crystal. An insulating film 5.degree. 5' is sandwiched between the entire surface 11iL thin film and the partial electrode film. A parallel alignment process such as a rubbing process is performed on the surfaces of the insulating film and the electrode film that are in contact with the liquid crystal, or an alignment control film is provided.

The liquid crystal cell as described above was manufactured as follows. First, an indium oxide, tin oxide (ITO) transparent electrode film, etc. is provided on a glass transparent substrate. ) was placed on a transparent substrate provided with ITO transparent ridge electrodes, and rubbed in a certain direction. The formation conditions were as follows: A 3.5% P I Q NMP (N-methyl-2-pyrrolidone) solution was applied by rotation using a spinner rotating at about 350 Or, p, m, and baked at 250 C for 1 hour.

The film thickness at this time is about 800λ.

Subsequently, the rubbing directions of the two substrates were made parallel to each other, a 6 μm glass fiber was sandwiched between the substrates as a spacer, a liquid crystal cell was assembled, and the liquid crystal was transparently sealed. The above-mentioned DOBAMBC was used as the liquid crystal material. After encapsulation, it was heated to the isotropic liquid temperature and gradually cooled (o, s
C/m, degree) and the helical axis is aligned.

Note that one or two polarizing cables may be used on the outer surface of the substrate depending on safety.

Displaying a pattern according to this embodiment is performed as follows. First, a DC voltage of constant polarity (
(for example, in the positive direction) to create a uniform background.

This state may be permanently memorized, but there are also cases where it is safe to continue excitation at appropriate time intervals. next,
The polarity opposite to that described above (
For example, by applying a direct current voltage (for example, in the negative direction), a pattern is displayed by realizing a state different from the background. For example, if the background is set to a transparent state, a display like the one shown in Figure 3 will be created, and if the background is set to a light-absorbing state, the display shown in Figure 4 will be displayed.
A display like the one shown is displayed.

According to this embodiment, as shown in Figure 6 above, by selecting the polarity of the applied voltage, it is possible to display either type of display as shown in FIGS. 3 and 4.

As described above, the present invention has the advantage that the background can be controlled and an electro-optical device with a fast response speed can be used.

[Brief explanation of drawings]

FIGS. 1 (1) and (2) are cross-sectional views showing a conventional electro-optical device, FIG. 2 is a cross-sectional view showing an embodiment of the present invention, and FIGS. FIG. 4 is a diagram illustrating an example of a pattern display according to an example. 1.1'...transparent electrode, 2.2'...partial electrode film,
3...Liquid crystal layer, 4.4'... Whole electrode film, 5,5'
Insulation v5) sentinel 4

Claims (1)

[Claims] 1. Two transparent substrates provided with transparent electrodes and arranged so that the transparent electrodes face each other, a liquid crystal layer sandwiched between the transparent electrodes, and a liquid crystal layer connected to the transparent electrodes. and a means for applying an electric field to the liquid crystal layer, wherein the liquid crystal layer is made of a composition containing a smectic liquid crystal exhibiting ferroelectricity whose molecular axes are substantially parallel to the substrate and aligned in a substantially constant direction. A. An electrode that excites only a predetermined portion of the electro-optical film, wherein the transparent electrode is composed of an electrode film that excites the entire liquid crystal layer and an electrode film that excites only a predetermined portion of the liquid crystal layer. 2. The electro-optical device according to claim 1, wherein an insulating film is sandwiched between the layers.