JPS62192724A - Ferroelectric liquid crystal element and its production - Google Patents

Abstract

PURPOSE:To eliminate defective lines during molecular orientation and to obtain uniform orientation by respectively forming obliquely oriented layers having a specific range of angles on the opposed surfaces of substrates in such a manner that a pair of the obliquely oriented layers are obliquely oriented oppositely from each other. CONSTITUTION:The directions where the directions of the directions of the liquid crystal molecules on the substrate surfaces are projected to the substrate surfaces are made approximately parallel with each other to obliquely orient the oriented layers 6, 8 of the upper and lower substrates 2, 4 in such a manner that the directions of the inclination of said layers are opposite from each other between the upper and lower substrates. The liquid crystal 10 in the central part of the liquid crystal layer is parallel with the substrates when no electric field is impressed to the element and therefore, the orientation of the state of impressing the voltage to the element can be kept maintained and that a memory effect is easily generated. The angle of inclination of the liquid crystal molecules 9 on the substrate surfaces created by the obliquely oriented layers 6, 8 is preferably 5 deg.-40 deg. from the substrates. The control force of the substrate surfaces on the liquid crystal molecules is too strong if the angle is <=5 deg.. Continuous change between the upper and lower substrates is no longer possible and the defect of orientation is generated when the angle exceeds 40 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a liquid crystal element using ferroelectric liquid crystal and a method for manufacturing the same, and particularly relates to alignment of liquid crystal.

(Prior art) Ferroelectric liquid crystals are expected to be put to practical use because they exhibit high-speed response on the microsecond scale and have memory properties, so there is no limit to the display capacity in time-division drive displays. ing.

A technical problem when using ferroelectric liquid crystals is the difficulty in alignment. As an orientation technique for ferroelectric liquid crystal, for example, Japanese Patent Application Laid-Open No. 60-57821 describes an attempt to uniaxially align only the orientation surface of one substrate. Also,
JP-A-59-131913 describes an attempt to use a combination of a substrate with a rubbed polyimide orientation surface and a vertically oriented substrate. Furthermore, JP-A-60-66
233@ publication describes alignment by a rubbing method using polymers such as nylon, polyethylene, polyester, etc. as an alignment film.

(Problems to be Solved by the Invention) However, each of the above-mentioned methods has the following drawbacks.

In the method disclosed in JP-A-60-57821 for regulating molecular orientation on only one side, the molecular orientation regulating force is too weak, and many defective lines occur during molecular orientation, resulting in a decrease in contrast. Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 59-131913 does not provide an alignment having a memory effect, which is a characteristic of ferroelectric liquid crystals. Furthermore, in the technique of JP-A-60-66233, the presence of defect lines during molecular orientation is unavoidable.

Therefore, an object of the present invention is to obtain a ferroelectric liquid crystal element that has no defect lines in molecular alignment, achieves uniform alignment of ferroelectric liquid crystal, and has high contrast and a clear memory effect. .

[Structure of the Invention] (Means for Solving Problems) A ferroelectric liquid crystal element of the present invention is a ferroelectric liquid crystal element in which a ferroelectric liquid crystal is sandwiched between a pair of substrates having electrodes. have tilted alignment layers on opposing surfaces of the substrates, each having an angle between the director of the liquid crystal molecules and the substrate surface of 5 degrees to 40 degrees, and the tilted alignment layers on the surfaces of the pair of substrates have opposite tilted alignments. This is a ferroelectric liquid crystal element characterized by:

Further, in the method for manufacturing a ferroelectric liquid crystal element of the present invention, each of the pair of substrates has an angle of 7Q degrees to 8Q degrees with respect to the normal line of the substrates.
forming an alignment layer by vapor depositing an insulator on the substrate at a vapor deposition angle of 8 degrees, and making the alignment layer face each other so that the direction of vapor deposition of the insulator is substantially the same on the pair of substrates, and A method for manufacturing a ferroelectric liquid crystal element, comprising the steps of arranging a pair of substrates at a predetermined interval, and filling a gap between the pair of substrates with ferroelectric liquid crystal.

(Function) By using the inclined alignment layer, the regulating force that liquid crystal molecules receive from the substrate surface in a plane parallel to the substrate surface becomes weaker. This makes it possible to balance the twisting force between liquid crystal molecules and the force regulating the liquid crystal molecules by the substrate surface, and it is possible to obtain uniform alignment without defects.

If the direction of the tilt direction of the liquid crystal molecules on the substrate surface is approximately parallel to the direction projected onto the substrate surface, then as shown in FIG. In the case of inclined orientation, as shown in FIG. 1, the upper and lower substrates 2.
In No. 4, the direction of inclination of the alignment layer 6.8 is opposite between the upper and lower substrates. As shown in Fig. 5, in the case of forward tilt alignment, a positive or negative electric field is applied to the liquid crystal layer to make the molecular axes of the liquid crystal molecules 9 parallel to the substrate, inverting the dipoles of the liquid crystal molecules and causing switching. Afterwards, when the electric field is removed, the liquid crystal 10 at the center of the liquid crystal layer returns to its original tilted orientation due to the influence of the tilted orientation on the substrate surface, making it difficult to produce a memory effect.

On the other hand, as shown in FIG. 1, in the case of reverse tilt orientation,
When no electric field is applied, the liquid crystal 10 at the center of the liquid crystal layer is parallel to the substrate, so even after the electric field is removed, it can continue to be oriented in the electric field applied state, and a memory effect is likely to occur. Therefore, the relationship between the alignment layers between the pair of substrates is preferably such that they have oppositely inclined orientations.

The tilt angle of the liquid crystal molecules 9 formed by the tilted alignment layer 6.8 on the substrate surface is preferably between 5 degrees and 40 degrees from the substrate, and when the tilt angle is 5 degrees or less, the regulating force on the liquid crystal molecules on the substrate surface is strong. Otherwise, alignment defects will occur. Furthermore, when a positive or negative electric field is applied to the liquid crystal to reverse the dipole of the liquid crystal molecules and cause switching, the liquid crystal molecules near the substrate surface remain trapped by the substrate surface and do not move, eliminating the memory effect. Furthermore, if the tilt angle exceeds 40 degrees, the difference in reverse tilt between the surfaces of the two substrates is too large, and the alignment of the liquid crystal cannot be changed continuously between the upper and lower substrates, resulting in alignment defects.

The ferroelectric liquid crystal of the present invention is produced by forming an alignment layer by depositing an insulator on each of a pair of substrates at a deposition angle of 70 degrees to 88 degrees with respect to the normal line of the substrates; This can be achieved by a manufacturing method consisting of a process of arranging substrates facing each other so that the deposition direction of the material is almost parallel and in the same direction as shown in Figure 2, and a process of filling ferroelectric liquid crystal between the substrates. . Note that when the deposition angle is 70 degrees or less, the liquid crystal molecules are not inclinedly aligned, but are horizontally aligned with their molecular axes oriented in a direction perpendicular to the vapor deposition direction. Further, if the angle is 88 degrees or more, the tilted alignment layer cannot be efficiently formed.

(Embodiments) Embodiment 1 FIG. 2 shows an embodiment of the present invention, in which two substrates 10, 12 made of transparent glass are opposed to each other.

An electrode 14.16 is formed on the opposite side of each substrate, and a tilted alignment layer 18.20 is deposited on the electrode 14.16, respectively. A ferroelectric liquid crystal 22 is sandwiched between these substrates 10.12 in contact with inclined alignment layers 18.20 to form a liquid crystal element 24.

The method for manufacturing this ferroelectric liquid crystal element will be explained below.

On the electrode side surface of each of the substrates 10 and 12, SiO was deposited to a thickness of 50 mm using an oblique deposition method at a deposition angle of 86 degrees to form tilted alignment layers 18 and 20, respectively. Incidentally, the deposition angle is as shown in FIG. 4 on the substrate 14.
The angle α between the direction 26.28 perpendicular to 16 and the vapor deposition direction 30.32 was defined. In the figure, 34 is an evaporation source.

After this, the substrate 10.12 is attached in the M direction 30.32 to the substrate 1.
They were bonded together with an interval of about 2 μm so that the directions 36 and 38 projected on 0.12 were substantially parallel and in the same direction, and the inclined alignment layers 18 and 20 faced each other. MBRΔ8 was sealed between these substrates as a ferroelectric liquid crystal 22 to form a liquid crystal element 24.

Next, as shown in FIG. 2, a polarizing plate 40 with a polarizing axis 40a shifted by about 68 degrees from a direction 36 in which the vapor deposition direction of the inclined alignment layer 18 is projected onto the substrate 10 of the liquid crystal element 24 is attached.
Another polarizing plate 42 whose polarizing axis 40a and polarizing axis 42a were perpendicular to each other was installed on the substrate 12.

When electro-optical characteristics were measured using the above liquid crystal element, the contrast was approximately 35:1 when driven by a ±10 V rectangular wave. Furthermore, even when the electric field was removed, a clear memory property was confirmed in which the applied electric field remained unchanged. In addition, when observing the liquid crystal element using a polarizing microscope, we found that
A very uniform orientation was observed with no defect lines in the molecular orientation.

The tilt angle of the liquid crystal molecules was 23 degrees.

Example 2 DO was added to the liquid crystal cell used in Example 1 as a ferroelectric liquid crystal.
BANBC was enclosed. When the electro-optical characteristics were measured, the contrast was approximately 30=1 for square wave driving of ±10 V. Furthermore, the same memory properties as in Example 1 were confirmed. In this case as well, there were no defect lines in the molecular orientation, and the orientation was very uniform. Further, the tilt angle of the liquid crystal molecules was about 25 degrees.

Example 3 When the electro-optical characteristics were measured in Example 1 by changing the deposition angle to 75 degrees, the contrast was 27:1. Furthermore, the same memory properties as in Example 1 were confirmed. In this case as well, there were no defects in molecular orientation, and the orientation was uniform. The tilt angle of the liquid crystal molecules was about 38 degrees.

Example 4 When the electro-optical characteristics were measured in Example 1 by changing the deposition angle to 87 degrees, the contrast was found to be 34:1. Furthermore, the same memory properties as in Example 1 were confirmed. In this case as well, there were no defects in molecular orientation, and the orientation was uniform. The tilt angle of the liquid crystal molecules was 18 degrees.

Example 5 In Example 1, the inclined alignment layers 18 and 20 were formed by changing the vapor deposition material to aluminum trifluoride. When electro-optical properties were measured, the contrast was 32:1. In addition, memory properties were confirmed. In this case as well, there were no defect lines in the molecular orientation, and the orientation was uniform. The tilt angle of liquid crystal molecules is
It was about 14 degrees.

Comparative Example 1 In Example 1, a forward tilt alignment liquid crystal cell was formed with the projection directions 36 and 38 of the vapor deposition direction on the substrate being opposite to each other as shown in FIG. Enclosed. When we measured the electro-optical characteristics, the contrast was 1
The ratio was 4:1. In addition, no memorability was observed depending on the location. The tilt angle of the liquid crystal molecules was 23 degrees.

Comparative Example 2 In Example 1, as the alignment layer 18.20, polyimide resin (PIX1400: manufactured by Hitachi Chemical Co., Ltd.) was applied to the substrate using a spinner, and then rubbed in one direction, so that the rubbing directions were in the same direction, resulting in a reverse tilt orientation. A cell was assembled so that MBRAS was sealed as a liquid crystal in this cell.When electro-optical measurements were taken, the contrast was approximately 5:1.
Many alignment irregularities occurred. Note that the tilt angle of the liquid crystal molecules was about 2 degrees.

Comparative Example 3 In Example 1, FC-805 (
(manufactured by Sumitomo 3M) was applied to the substrate, and then rubbed in one direction, and the liquid crystal cell was assembled so that the rubbing directions were in the same direction and oppositely inclined orientations were obtained.

MBRAS was sealed in this liquid crystal cell as a liquid crystal. When measured in electro-optical mode, the contrast was approximately 2.5:
In No. 1, there were almost no memory locations in the cell, and many uneven orientations occurred. Note that the tilt angle of the liquid crystal molecules was approximately 55 degrees to 80 degrees.

[Effects of the Invention] As described in the above embodiments, according to the present invention, by making the tilted orientation layers of the substrates have reverse tilted orientation, the twisting force applied to the liquid crystal molecules between the pair of substrates can be reduced. This makes it possible to achieve uniform alignment without defect lines. Thus, a liquid crystal element having high contrast and a clear memory effect can be obtained. Therefore,
If the liquid crystal element of the present invention is used, X-
It is possible to realize a high-contrast, large-capacity liquid crystal display element using the Y simple matrix type.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the reverse tilt orientation in the present invention, and FIG.
Figure 3 is a perspective view showing an embodiment of the present invention, Figure 3 is a schematic exploded perspective view explaining the invention in detail, Figure 4 is a diagram explaining the deposition angle, and Figure 5 is a cross section showing forward tilt orientation. It is a diagram. 2.10... Upper substrate, 4.12... Upper substrate, 9.10... Liquid crystal molecule, 14.16... Electrode, 18.20... Alignment layer, 22... Ferroelectric liquid crystal, 24... Liquid crystal element, 40, 42... Polarizing plate. Agent Patent Attorney Ken Nori Chika IIcJ Norio Ogo Figure 5 Figure 2 fρ Figure 3 Figure 4

Claims (2)

[Claims] (1) In a ferroelectric liquid crystal element in which a ferroelectric liquid crystal is sandwiched between a pair of substrates having electrodes, the angle between the director of the liquid crystal molecules and the substrate surface is set to 5 on the opposing surfaces of the substrates. 1. A ferroelectric liquid crystal device, characterized in that the tilted alignment layers on the surfaces of the pair of substrates have opposite tilted orientations, each having a tilted orientation layer having an angle of 40 degrees to 40 degrees. (2) forming an alignment layer on each of a pair of substrates by depositing an insulator at a deposition angle in a range of 70 degrees to 88 degrees with respect to the normal line of the substrate; and depositing the insulator. a step of arranging the pair of substrates with the alignment layers facing each other so that the directions are substantially the same in the pair of substrates and with a predetermined interval therebetween; and a step of disposing a ferroelectric liquid crystal in the gap between the pair of substrates. 1. A method for manufacturing a ferroelectric liquid crystal element, comprising the step of encapsulating a ferroelectric liquid crystal element.