JPH04255826A - Liquid crystal electrooptical device - Google Patents

Abstract

PURPOSE:To easily control the layer structure of a ferroelectric liquid crystal and to uniformize the gap between substrates as the disposition of spacers in desired positions is possible as well as to obviate the generation of unequal contrasts. CONSTITUTION:The ferroelectric liquid crystal 4 has a smectic layer having a refracted structure. The angle formed by the layer normal of the smectic layer and the substrate 1 is within + or -10 deg. and the angle formed by the layer normal of the smectic layer and the orientation treatment direction of an oriented film 3 is within + or -10 deg.. The spacers 5 are respectively provided on the substrates 1 and are constituted of an insulating material. The spacers are formed in a stripe shape and are provided in parts exclusive of picture elements. The spacers on the respective substrates are pressed to each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid crystal electro-optical devices such as liquid crystal display elements and liquid crystal optical shutter arrays.

0002

[Prior Art] A liquid crystal electro-optical device using a ferroelectric liquid crystal is disclosed in US Pat. No. 4,367,924 by Clark et al. as having memory properties, being capable of high-speed response, and having good multiplex characteristics. Since it was reported, research has been intensively conducted.

The present applicant has proposed that in order to improve the memory performance of such a liquid crystal electro-optical device, it has a smectic layer with a structure in which ferroelectric liquid crystal is bent, and the layer normal of the smectic layer and the substrate are It is proposed that it is effective to set the angle between the layer normal of the smectic layer and the alignment treatment direction of the alignment film within ±10°.

FIG. 6 shows a cross-sectional view of a conventional liquid crystal electro-optical device. As shown in FIG. 6, conventionally commonly used spacers 45 include spherical ones such as silica beads. In a liquid crystal electro-optical device equipped with this spacer 45, the spacer 45 is usually scattered on one substrate 1 on which the electrode 2 and the alignment film 3 are formed, and then the spacer 45 is spread on the other substrate 1 on which the electrode 2 and the alignment film 3 are formed. The ferroelectric liquid crystal 4 is produced by sandwiching the ferroelectric liquid crystal 4 between the two substrates 1 and facing each other.

[0005]

Since the conventional liquid crystal electro-optical device was manufactured by scattering the spacers 45, it was impossible to arrange the spacers 45 at desired positions on the substrate 1. For this reason, it has been difficult to make the layer structure of the ferroelectric liquid crystal 4 into the above-mentioned specific layer structure. Also, spacer 4
Since the substrates 5 cannot be placed at desired positions, there are also problems in that the gap between the substrates 1 cannot be maintained uniformly and that uneven contrast occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal electro-optical device in which the layer structure of ferroelectric liquid crystal can be easily controlled.

[0007]

[Means for Solving the Problems] A liquid crystal electro-optical device of the present invention is a liquid crystal electro-optical device in which a ferroelectric liquid crystal is sandwiched between two substrates each having an electrode and an alignment film formed thereon. The dielectric liquid crystal has a smectic layer with a refracted structure, the angle between the normal of the smectic layer and the substrate is within ±10°, and the normal of the smectic layer and the orientation of the alignment film are within ±10°. The angle formed with the processing direction is within ±10°, and spacers are provided on each of the two substrates, and the spacers are made of an insulating material, have a striped shape, and are arranged in areas other than pixels. The spacers provided on the respective substrates are brought into contact with each other.

[0008]

[Operation] FIG. 1 shows a refracted smectic layer used in the liquid crystal electro-optical device of the present invention. The hatched portions 14 of the smectic layer 10 are portions that are in contact with the alignment film. The angles α1 and α2 formed by the layer normals l1 and l3 of the smectic layer 10 and the substrate (represented by line segments l2 and l4 in FIG. 1) must be within ±10°, respectively. Also, the layer normal l1 of the upper part of the chevron interface 15
The angle β1 formed between the smectic layer and the alignment treatment direction l6 of the alignment film in contact with the upper smectic layer must be within ±10°. Similarly, the angle β2 between the layer normal l3 of the lower part of the chevron interface 15 and the alignment treatment direction l8 of the alignment film in contact with the smectic layer below is ±
Must be within 10°.

The smectic layer having a refracted structure that can be used in the liquid crystal electro-optical device of the present invention is such that the angle between the layer normal of the smectic layer and the substrate is within ±10°, and the angle between the layer normal of the smectic layer and the substrate is within ±10°. The angle formed by the direction of the alignment process of the alignment film and the direction of alignment of the alignment film may be within ±10°, and is not limited to the smectic layer 10 in FIG. Further, the ferroelectric liquid crystal constituting the liquid crystal electro-optical device of the present invention may have the above-mentioned smectic layer, and may include a structure other than the above-mentioned smectic layer.

[0010] The liquid crystal electro-optical device of the present invention has particularly excellent memory properties due to the above-described configuration. Furthermore, the liquid crystal electro-optical device of the present invention has steep threshold characteristics, and can display clear images when used in a display device.

Examples of the insulating material for the spacer include photosensitive materials such as photosensitive polyimide and gelatin. In addition to photosensitive materials, polyimide, polyamide, etc. can also be used.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal electro-optical device of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view of the liquid crystal electro-optical device of the present invention. An example of a method for manufacturing the liquid crystal electro-optical device of the present invention will be described. First, photosensitive polyimide, which is the material of the spacer 5, is applied onto the substrate 1 on which the electrode 2 is formed, and then the photosensitive polyimide is exposed and etched using a mask provided with a desired pattern to form a striped pattern. Spacer 5
form. Next, a material for the alignment film 3 is applied onto the substrate 1, and an alignment treatment is performed to form the alignment film 3. The substrates 1 are placed facing each other as shown in FIG. 2, and the spacers 5 on each substrate 1 are brought into contact with each other. Next, a ferroelectric liquid crystal 4 is sandwiched between two substrates 1 to fabricate a liquid crystal electro-optical device. Figure 3
2 shows a diagram of the spacer 5 viewed from the substrate 1 side. In the present invention, the spacer 5 can be provided in a portion other than the pixel 6.

When the layer structure of the ferroelectric liquid crystal of the liquid crystal electro-optical device manufactured in this manner was investigated, it was found that the smectic layer had a refracted structure, and the angle between the layer normal of the smectic layer and the substrate was ±. 10° or less, and the angle between the layer normal of the smectic layer and the alignment treatment direction of the alignment film is ±
It was within 10°.

[0015] As the material of the spacer 5, an insulating material other than a photosensitive material can also be used. In this case, an insulating material is laminated on the substrate 1 on which the electrode 2 is formed, a photosensitive resist film is laminated on top of the insulating material, and then exposed using a mask provided with a desired pattern, developed, Etching is performed to pattern the resist film and the insulating material, and then the resist film is removed to form striped spacers 5.

Next, the memory properties of the liquid crystal electro-optical device of the present invention will be explained using FIG. 4. The upper pulse waveform in FIG. 4 represents the pulse waveform of the voltage applied to the liquid crystal electro-optical device, and the lower line represents the change in light transmittance as the applied voltage changes.

First, reset pulse 3 is applied to the liquid crystal electro-optical device.
If a black writing pulse 32 is applied after applying 1, the light transmittance becomes a value close to 0, and black is displayed. After that, the black state is maintained, and the light transmittance changes slightly while remaining close to 0. Next, when half-selective pulses 33 and 34 are applied,
The light transmittance changes once, but immediately returns to its original state, and the display maintains its original black state. Then reset pulse 3
When a white writing pulse 36 is applied after applying 5, the light transmittance becomes maximum and the liquid crystal electro-optical device displays white. After that, the white state is maintained and the light transmittance changes slightly at a value close to the maximum value. Next, half-select pulses 37, 38
When applied, the light transmittance changes once but immediately returns to its original state, and the display remains white. As described above, in the liquid crystal electro-optical device of the present invention, the display state is stably maintained before and after the application of the half-selective pulse, and in particular, the display state can be quickly returned to the original state after the application of the half-selective pulse.

Further, the characteristics of the liquid crystal electro-optical device of the present invention will be explained using FIG. Line 41 represents the relationship between light transmittance and applied voltage during black writing (display state changes from white to black, or light transmittance changes from maximum to minimum), and line 42 represents white writing. (The display state changes from black to white, or the light transmittance changes from the minimum to the maximum.) This graph shows the relationship between the light transmittance and the applied voltage. As shown in FIG. 5, the lines 41 and 42 are approximately symmetrical. This means that in the liquid crystal electro-optical device of the present invention, it is possible to perform black writing and white writing with the same voltage, that is, it is easy to drive.

In FIG. 5, the threshold characteristics will be explained by taking white writing (line 42) as an example. Set the minimum value of light transmittance to 0
, the maximum value is 100. At this time, the voltage required to increase the light transmittance from 0 to 10% of the total is V10, and the voltage required to increase the light transmittance from 0 to 90% of the total is V90. As is clear from FIG. 5, the ratio between V10 and V90, which represents the threshold characteristic, is a very small value, indicating that the liquid crystal electro-optical device of the present invention has a steep threshold characteristic. Also, in the case of black writing (line 41)
, it can be seen that it also has steep threshold characteristics.

[0020]

Effects of the Invention In the liquid crystal electro-optical device of the present invention, the angle between the layer normal of the smectic layer and the substrate is within ±10°, and the angle between the layer normal of the smectic layer and the alignment treatment direction of the alignment film. can be easily controlled within ±10°. Therefore, it is possible to easily manufacture a liquid crystal electro-optical device with excellent memory properties, drive characteristics, and threshold characteristics. Furthermore, in the present invention, since the spacer can be placed at a desired position, the gap between the substrates can be made uniform, and contrast unevenness does not occur.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the layer structure of a refracted smectic layer used in the present invention.

FIG. 2 is a sectional view of the liquid crystal electro-optical device of the present invention.

FIG. 3 is a top view of the liquid crystal electro-optical device of the present invention.

FIG. 4 is a drawing showing the relationship between applied voltage pulses and light transmittance of the liquid crystal electro-optical device of the present invention.

FIG. 5 is a drawing showing the relationship between applied voltage and light transmittance of the liquid crystal electro-optical device of the present invention.

FIG. 6 is a cross-sectional view of a conventional liquid crystal electro-optical device.

[Explanation of symbols]

1 Board 2 Electrode 3 Alignment film 4 Ferroelectric liquid crystal 5 Spacer 6 pixels

Claims (1)

[Claims] 1. A liquid crystal electro-optical device comprising a ferroelectric liquid crystal sandwiched between two substrates each having an electrode and an alignment film formed thereon, wherein the ferroelectric liquid crystal has a smectic layer with a refracted structure. , the angle between the layer normal of the smectic layer and the substrate is within ±10°, and the angle between the layer normal of the smectic layer and the alignment treatment direction of the alignment film is within ±10°. , a spacer is provided on each of the two substrates, the spacer is made of an insulating material, has a striped shape and is provided in a portion other than the pixel, and is provided on each of the substrates. A liquid crystal electro-optical device characterized in that the spacers are brought into contact with each other.