JPS6380226A - Liquid crystal electrooptic device - Google Patents

Abstract

PURPOSE:To prevent lowering of contrast due to orientation defect, and to enable an application for a display device, and an electron shutter, etc., by effecting dislocation orientation at the time of operation of the titled device. CONSTITUTION:The titled device is effected at least dislocation orientation at the time of the operation of said device. The dislocation orientation is effected by impulsing a high frequency bias pulse train to the liquid crystal which is uniaxially orientated with relatively smooth. At this time, the defect is removed by cutting a zigzag wall, etc., which is one of defects, in piece, thereby operating uniformly the whole liquid crystal device. Thus, the excellent titled device having less lowering of the contrast is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal electro-optical device, and particularly to a liquid crystal electro-optic device using ferroelectric liquid crystal.

[Prior art] Conventional ferroelectric liquid crystal elements include mob, 0ryst, etc.
, Liq.

Oryat, 1983. Vo19a, PP, 213-2
F'igure in 34 7. Or F'igure &
Generally, a relatively uniform and smooth alignment state (monodomain) is used, as typified by the photograph.

These are the ninth reasons that if there is an alignment defect in the element, it will lead to a decrease in contrast due to light leakage. Orientation methods include using an alignment film, applying shear force to liquid crystal molecules, or growing liquid crystal from a cross section of a film using crystal growth technology. , the liquid crystal molecules operate while maintaining their oriented appearance. However, the liquid crystal electro-optical device produced by the above alignment method is manufactured by IFerroelectrics, 19
84. Vo159, PP! , 69-1) The zigzag wall δ-φ defect shown in 6 is likely to occur. This defect is said to be caused by the interaction between the cell configuration and the polarization of liquid crystal molecules. Furthermore, our experiments have shown that, in addition to the above, many occurrences occur in environments where stress is applied to the liquid crystal layer. When this defect occurs in a liquid crystal electro-optical element due to any of the causes mentioned above, in the conventional liquid crystal electro-optical element, a large contrast decrease occurs due to light leakage due to this defective portion.

[Problem that the invention seeks to solve]

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a submerged liquid crystal electro-optical element with less reduction in contrast by operating the liquid crystal electro-optical element in a dislocation orientation. It is.

[Ninth way to solve the problem]

The liquid crystal electro-optical element of the present invention is characterized in that it has at least dislocation alignment during operation.

[Operation] Dislocation orientation in the present invention will be explained. First, the dislocation orientation in the present invention is
It is an oriented structure in which a striped structure appearing in a direction approximately perpendicular to the layer direction, which is expected to be caused by disorder of the layer structure of the ferroelectric liquid crystal, is relatively densely assembled, and reference photo 1. Reference photo 2 shows a typical external photo.

In order to create this dislocation alignment, a high-frequency bias pulse train is applied to the liquid crystal layer, which has been relatively smoothly uniaxially aligned by the conventional alignment method, at a magnitude (frequency and peak value) or higher that generates the dislocation alignment. It will be done. At this time, the zigzag walls and δ-φ defects generated due to uncontrolled orientation are cut into pieces and removed due to the dislocation orientation. Therefore, the entire liquid crystal element is in a uniform operating state. The electro-optic effect at this time is almost the same as the electro-optic effect in the conventional orientation, although some scattering effect occurs. Furthermore, although the mechanism by which dislocation alignment occurs is not clear at present, we applied a high-frequency bias to the next layer tilted in the thickness direction of the device, and by coupling the spontaneous polarization of the liquid crystal with the electric field, Part of the smectic layer is curved K
I think this will occur more often.

[Example of real power]

Example 1 A chiral smectic liquid crystal (O8-101, manufactured by Chitsun Corporation) was sealed between two substrates each having a rubbed transparent electrode on the surface, and assembled so that the cell thickness was approximately 2 μm. This liquid crystal electro-optical element is sandwiched between two mutually orthogonal polarizing plates, and a high frequency bias waveform as shown in FIG. 1 is applied to the liquid crystal layer. At this time, the pulse width and peak value of the high-frequency bias applied to the common electrode were varied to find conditions for dislocation orientation. In the case of this liquid crystal, when a pulse width of 20 to 50 .mu.m is applied at 30.degree. C., a good dislocation alignment can be obtained if a voltage exceeding the peak value range of ±50 to +50 V is applied. Under this condition, set the voltage and pulse width when selecting, for example, Pvt6rJOpe, V, = -20V
When the liquid crystal element was operated at , V, = 10 V, Vd = ±8 ■, uniform dislocation alignment was achieved even in the initial zigzag wall and δ-φ defects, and the overall contrast property was 50:1. was gotten. The alignment state of the Doki optical element at this time was the state shown in Reference Photo 1. Moreover, the nine elements oriented by -degree dislocation are:
In subsequent operations, the dislocation orientation is maintained even without applying a high-frequency bias pulse train or even when a low voltage is applied.

It is also possible to apply a high-frequency pulse train each time as shown in FIG.

On the other hand, for comparison, when a high-frequency bias of a magnitude that does not cause the dislocation orientation is applied, a good contrast ratio of 55:1 is obtained in a place where the initial alignment state is good, but the zigzag wall, δ-φ In places with defects, light leaks, and in places with especially large δ-φ defects, the contrast ratio drops to about 5:1.

Practical Example 2 A chiral smectic liquid crystal, zL 3489 manufactured by Merck, was sealed in the same device as in Example 1 and assembled. Next, a high frequency bias waveform as shown in Fig. 1 is applied to this element. At this time, the pulse width and peak value of the high-frequency pulse applied to the common electrode were varied to find conditions for dislocation orientation. In the case of this liquid crystal, good dislocation alignment was obtained when a voltage of vll greater than the peak value range of ±60 to ±25 V was applied at 40° C. and with a pulse width of 5 to 20 μm. This orientation state is shown in Reference Photo 2. Further, when the temperature is lowered, the pulse width becomes good in the long direction, resulting in a good dislocation orientation. Furthermore, the voltage and pulse width at the time of selection are set in the high frequency pulse condition, for example, PwlO.
O#sec, V+=-1sv.

When the liquid crystal electro-optical element was driven with v, = +5v and vα = ±3v, the locations where there were initially zigzag defects and δ-φ defects became uniformly dislocated, and the overall contrast ratio was 38:1. was gotten.

The above-mentioned embodiments illustrate a part of the present invention, and the liquid crystal material is not limited to the above-mentioned materials, and the high-frequency bias conditions that cause dislocation alignment can be arbitrarily selected within the range of conditions that cause the dislocation alignment. Furthermore, the configuration of the alignment film of the element can be selected arbitrarily, but it is possible to select a combination of different materials at the interface with the liquid crystal layer (for example,
PJ-Engineering To.

P-nee EliO, PI-PVA, etc.) are preferable because dislocation orientation occurs more easily on the low voltage side. Further, the driving method is not limited to this embodiment, and static driving is also possible.

〔Effect of the invention〕

As described above, according to the present invention, contrast reduction due to alignment defects, which is a problem in conventional liquid crystal electro-optic elements, can be prevented,
Moreover, it is carefully designed to obtain uniform contrast characteristics throughout the entire body.
It can be applied to display elements, electronic shutters, etc.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing driving waveforms of an example of the liquid crystal electro-optical element of the present invention.

Claims (3)

[Claims] (1) In a liquid crystal electro-optical element in which a ferroelectric liquid crystal is sandwiched between two substrates having opposing electrodes, the liquid crystal electro-optical element is at least dislocation oriented during operation. A liquid crystal electro-optical device featuring: (2) The liquid crystal electro-optical element according to claim 1, wherein the driving method for the liquid crystal electro-optical element is high frequency bias driving. (3) The size of the high-frequency bias voltage pulse group applied to the liquid crystal electro-optical element is larger than a threshold value for producing a dislocation alignment. Liquid crystal electro-optical element.