JPH0826317B2 - Ferroelectric liquid crystal panel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a high-speed, high-contrast ferroelectric liquid crystal panel.

2. Description of the Related Art Liquid crystal display devices are used in watches, calculators, etc. due to their advantages such as thinness, lightness, and low voltage drive capability. However, the nematic liquid crystal currently used has a response speed as low as several milliseconds to several tens of milliseconds, so that high-speed response is impossible, and its application field is limited. On the other hand, the ferroelectric liquid crystal can be applied to the fields of high-speed display devices, memory-type displays, liquid crystal shutters, etc. because of its response speed in microseconds and memory effect. At present, a rubbing method, an oblique vapor deposition method, a magnetic field application method, an electric field application method, a sharing method, etc. have been devised as an alignment method, and the rubbing method is the best in terms of mass productivity and practicality. In the rubbing orientation method, uniaxiality is too strong, resulting in monostable or twist stable, and it is difficult to obtain good uniform type bistable characteristics. SmC from I _SO phase also in the ferroelectric liquid crystal
^* Phase sequence up to phase is I _SO → SmA → SmC ^* (IAC system) I _SO → N ^* → SmC ^* (INC system) I _SO → N ^* → SmA → SmC ^* (INAC system) I _SO → SmC ^* ( IC type) is possible.

The orientation of ferroelectric liquid crystals depends largely on the phase sequence on the higher temperature side than the SmC ^* phase. Conventionally, the N ^* phase is required to achieve uniform alignment in the SmC ^* phase, and the longer the pitch of the N ^* phase, the more untwisted the ferroelectric liquid crystal becomes in the thin cell and the SmA phase is formed. It was considered that the phases were aligned well and a good orientation was obtained even in the SmC ^* phase.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Ferroelectric liquid crystals exhibiting the N ^* phase as described above show good alignment and bistability in a ferroelectric liquid crystal cell aligned by SiO oblique vapor deposition, but by rubbing When oriented, the alignment control force at the interface is strong, so the layers are properly aligned in the SmA phase, but when the SmA phase transitions to the SmC ^* phase, the molecules tilt from the layer normal and the layers are distorted. Disclination occurs, and it becomes monostable or twist stable. In addition, the ferroelectric liquid crystal (INC
(IC type) does not regulate the layer direction, so the alignment is defective, and even if IAC type liquid crystal is used, the layer directions are difficult to align, although not as much as INC type and IC type.

Means for Solving the Problems A ferroelectric liquid crystal having a spontaneous power pole of 20 nC / cm ² or more and 100 nC / cm ² or less and having three points of an isotropic phase, a kaikalnematic phase and a smectic A phase in a phase transition sequence Orient by the rubbing method.

Action Using this ferroelectric liquid crystal, it is possible to fabricate a uniform and bistable ferroelectric liquid crystal cell with high speed and high contrast even in the rubbing alignment method.

Examples Hereinafter, a ferroelectric liquid crystal panel of an example of the present invention will be described with reference to the drawings.

As shown in Fig. 1, ITO films 3 and 4 are formed as transparent electrodes on transparent glass substrates 1 and 2, and a polyimide resin is applied as an alignment film on them by a spinner. Then, a rubbing treatment is performed on the substrate and the alignment film surfaces of the substrate are bonded to each other. The thickness of the panel is 2 μm due to the spacer mixed in the sealing resin 7. Ferroelectric liquid crystal 8 was enclosed in this panel. The phase sequence of this ferroelectric liquid crystal is
The contrast in each of A, B, and C states is shown in Table 1 by changing as shown in the figure.

As is clear from this result, in the A state (IAC system), I _SO
During the transition from the phase to the SmA phase, the orientation of the molecular long axis and the formation of the layer occur at the same time, which makes it difficult to align the layer directions. Also, in the C state (INAC system), the orientation in the SmA phase is good, but the regulation force in the SmA phase is too strong, and the layer is distorted when the SmA phase transitions to the SmC ^* phase. On the other hand, in the B state, A
The orientation in the SmA phase is better than that in the state, and the regulation power is not as strong as in the C state. Therefore, the layer does not bend even in the transition from the SmA phase to the SmC ^* phase, the orientation is good, and the contrast is high. Stable characteristics were obtained.

When the spontaneous polarization is less than 20 nC / cm ² , the twist becomes stable and the contrast deteriorates, and when it exceeds 100 nC / cm ² , it becomes monostable <Table 2>. In the above invention, at least one of the substrates should be transparent, and polyimide was described as an example of the alignment film. However, other materials may be used, and surface treatment may not be performed with the alignment film.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the spontaneous polarization is 20 nC / cm ² or more and 100 nC / cm ² or less, and in the phase transition series, the isotropic phase, the chiral nematic phase, and the chiral smectic phase By using the ferroelectric liquid crystal with emphasis, conventional monolithic rubbing has achieved only monostable and twist-stable orientation, while high-speed, high-contrast uniform bistable ferroelectric liquid crystal panel has been developed. You can get it.

[Brief description of drawings]

FIG. 1 is a block diagram of a ferroelectric liquid crystal panel according to an embodiment of the present invention, and FIG. 2 is a graph showing a phase sequence of ferroelectric liquid crystal. 1 upper glass substrate, 2 lower glass substrate, 3, 4 ITO
Electrodes, 5,6 ... Alignment film, 7 ... Seal resin, 8 ... Ferroelectric liquid crystal.

Claims (3)

[Claims] 1. A ferroelectric liquid crystal panel using a ferroelectric liquid crystal having a triple point of an isotropic phase, a chiral nematic phase and a smectic A phase in a phase transition sequence. 2. The ferroelectric liquid crystal panel according to claim 1, wherein the ferroelectric panel is orientated by rubbing. 3. A ferroelectric liquid crystal having a spontaneous polarization of 20 nC / cm ² or more 10
The ferroelectric liquid crystal panel according to claim 1, characterized in that it is 0 nC / cm ² or less.