JPS6330827A - Production of liquid crystal device - Google Patents

Abstract

PURPOSE:To obtain an uniform orientation power by thermally treating a horizontal orientation layer after rubbing it, thereby making the difference of depth of fine grooves on the surface of the horizontal orientation layer due to rubbing small and making the shape of the grooves smooth. CONSTITUTION:The horizontal orientation layer 5 and 6 are formed by baking a polyimide resin on substrates 1 and 2 formed electrodes 3 and 4 thereon followed by offset printing said layers 5 and 6 so as to be 700Angstrom film thickness and baking it at the film forming temp. of 180 deg.C, for 1hr, respectively. Subsequently, the horizontal orientation layers 5 and 6 are rubbed in the direction of uniaxial directions 7 and 8 by a rubbing machine followed by thermally treating for 1hr at more than the film- forming temp. for example, 300 deg.C respectively. And, the substrates 1 and 2 are disposed in such way that the rubbing directions 7 and 8 of the substrates 1 and 2 are almost parallel in the same direction with each other with a distance of 2mum. The ferroelectric liquid crystal 9 is enclosed a space between the substrates 1 and 2. Thus, reducing of the difference of the depth of the fine grooves on the surface of the horizontal orientation layer due to rubbing, smoothing of the shape of the grooves, and debarring of the grooves are executed, by providing the thermal treating step after the rubbing step.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method of manufacturing a liquid crystal device, and particularly relates to a method of manufacturing an optimal liquid crystal device when using ferroelectric liquid crystal. .

(Prior Art) In recent years, liquid crystal devices have been widely used as display devices for wristwatches, calculators, and the like. Traditionally, nematic liquid crystals and twisted nematic liquid crystals have been widely used in such liquid crystal devices, but nematic liquid crystals have a slow electro-optic response time of about 50m5, so they are not suitable for use in fields that require high-speed response. Furthermore, twisted nematic liquid crystals have a limited display capacity.

Therefore, liquid crystal devices using ferroelectric liquid crystals that can solve the above problems are attracting attention.

(Problems to be Solved by the Invention) Liquid crystal devices using ferroelectric liquid crystals have a technical problem in that alignment treatment is extremely difficult.

In other words, as orientation processing methods that have been proposed for improving visibility, there are a method of growing a smectic layer from a spacer edge using a temperature gradient, an oblique evaporation method of inorganic materials such as SiO, a shearing method, a rubbing method, etc., but from a practical point of view From this perspective, the rubbing method is the best.

However, the surface of the alignment layer that has been subjected to the alignment treatment using the above-mentioned rubbing method has problems such as minute steps, variations in the shape of the grooves, and cracks even when the rubbing conditions such as rubbing pressure are strictly controlled within the practically possible range. This causes variations in the alignment force.

In liquid crystal devices using conventional nematic liquid crystals or twisted nematic liquid crystals, the influence of the above-mentioned variations in alignment force on contrast, etc. was minimal, but in liquid crystal devices using ferroelectric liquid crystals, Due to the above-mentioned variation in the alignment force, many defective lines occur during molecular alignment, resulting in a problem of reduced contrast.

In a liquid crystal device with a large display capacity using a roughly ferroelectric liquid crystal, the above-mentioned decrease in contrast is significant, and this is an obstacle to practical use.

The present invention was proposed in 2001 in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a liquid crystal device that can obtain uniform alignment force, has good contrast, and has high display quality.

[Structure of the Invention] (Means for Solving the Problems) In other words, the method for manufacturing a liquid crystal device of the present invention includes an alignment layer forming step of forming a horizontal alignment layer made of an organic material on two substrates, and A rubbing step of rubbing the horizontal alignment layer formed on each substrate, a heat treatment step of heating the rubbed horizontal alignment layer of each substrate, and a horizontal alignment layer facing these substrates with a predetermined gap between them. The method is characterized by comprising an assembly step of arranging the liquid crystal as shown in FIG.

(Function) In the method for manufacturing a liquid crystal device of the present invention, by providing a heat treatment step after the rubbing step, the molecules of the rubbed horizontal alignment layer made of material move thermally during the heat treatment, resulting in horizontal alignment. The layer surface shape changes. This change reduces the difference in the depth of fine grooves on the surface of the horizontal alignment layer caused by rubbing, smoothes the shape of the grooves, and removes pars.

Therefore, the alignment force becomes uniform and it becomes possible to prevent the generation of defective lines.

Furthermore, if the heat treatment process is performed after the assembly process, for example, the sealing performance of the part where adhesive is used to seal between the substrates will deteriorate, and the clamping pressure between the substrates will be reduced due to the difference in thermal expansion coefficient between the substrates and the adhesive. Since there are problems such as uneven orientation due to the influence of gas generated during heating, etc., the heat treatment process is preferably performed between the rubbing process and the assembly process.

In addition, in the heat treatment process, the heating temperature is from ioo'c to 350°.
C is good. That is, at a heating temperature of 100°C or less, 1 to
The above effects cannot be obtained in a practical heating time of about 2 hours. Further, at a heating temperature of 350° C. or higher, the horizontal alignment layer may thermally decompose, resulting in adverse effects such as loss of alignment force.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

Example 1 FIG. 1 is a diagram showing an example of a liquid crystal device manufactured by the method of the present invention.

The liquid crystal device shown in the figure is manufactured by the method shown below.

That is, electrodes 3.4 made of Nesa film are formed on one surface of each of two substrates 1.2 made of transparent glass. After baking the polyimide resin on the substrate 1.2 on which the electrode 3.4 was formed, offset printing was performed so that the film thickness was 700 mm, and baking was performed at a film forming temperature of 180° C. for 1 hour to form the horizontal alignment layer 5. form 6.

Thereafter, each of the horizontal alignment layers 5.6 is rubbed in a uniaxial direction 7.8 using a rubbing machine. After this,
The horizontal alignment layer 5.6 is formed at a temperature higher than the above film formation temperature, for example, 300℃.
Heat treatment at ℃ for 1 hour. Then, the substrate 1.2 is rubbed with the horizontal alignment layer 5.8 in substantially parallel and the same direction.
6 are arranged facing each other with a gap of 2 μm,
DOBAMBG (4-c
lecyloxybenzylidene 4'-
amino(2-methylbutyl) cinn
A ferroelectric liquid crystal 9 made of a mixed composition of amate type is sealed.

Next, as shown in FIG. 2, the polarizing plate 12 is placed on the substrate 1 with the polarizing axis 12a shifted by about 22 degrees from the rubbing direction 7 of the horizontal alignment layer 5, and the polarizing axis 11 is aligned with the polarizing axis 12a of the polarizing plate 12.
This is done by attaching the polarizing plate 11 onto the substrate 2 so that a is perpendicular to the polarizing plate 11.

As a result of observing the above liquid crystal device using a polarizing microscope, it was found that a uniform alignment force was obtained in which almost no defect lines were observed during molecular alignment. In addition, when we measured the electro-optical characteristics, it was found that ±10
The contrast was 30.1 for square wave driving (2). A memory effect was also clearly observed in which the applied state of the electric field remained semi-permanently even after the electric field was roughly removed.

Comparative Example 1 After rubbing the alignment layer 5.6 in Example 1 described above, the substrate 1.2 was placed with a predetermined gap without being subjected to heat treatment, and the liquid crystal 9 was sealed in this gap.

As a result of observing the above liquid crystal device using a polarizing microscope, many defective lines were observed in the molecular orientation. Further, when electro-optical characteristics were measured, the contrast was 9:1 for driving with a ±10 V rectangular wave. Furthermore, after the electric field is removed, the alignment force remains uniform for several tens to hundreds of milliseconds.
As a result, the memory effect became significantly weaker.

Example 2 The polyimide resin in Example 1 was changed to nylon 6, the film forming temperature was 100°C, and the heat treatment conditions after rubbing were 180°C, which is higher than the film forming temperature, for 1 hour.

As a result of observing the above liquid crystal device using a polarizing microscope, it was found that a uniform alignment force was obtained in which almost no defect lines were observed during molecular alignment. In addition, when we measured the electro-optical characteristics, it was found that ±10
The contrast was 28.1 for V square wave driving.

Comparative Example 2 After rubbing the alignment layer 5.6 in Example 2 described above, the substrate 1.2 was placed with a predetermined gap without being subjected to heat treatment, and the liquid crystal 9 was sealed in this gap.

As a result of observing the above liquid crystal device using a polarizing microscope, many defective lines were observed in the molecular orientation as in Comparative Example 1 described above. Further, when electro-optical characteristics were measured, the contrast was 7:1 with respect to ±IOV square wave driving. Further, after the electric field was removed, the time period during which the alignment force remained uniform was several milliseconds, and the memory effect was significantly weakened.

Example 3 The polyimide resin in Example 1 was changed to polyethylene terephthalate, the film forming temperature at this time was 100°C, and the heat treatment conditions after rubbing were 180°C above the formation IIA temperature.
It was one hour.

As a result of observing the above liquid crystal device using a polarizing microscope, it was found that a uniform alignment force was obtained in which almost no defect lines were observed during molecular alignment. In addition, when we measured the electro-optical characteristics, it was found that ±10
The contrast was 27.1 for V square wave driving.

Comparative Example 3 In the step of arranging the substrates 1.2 with a predetermined gap in Example 1 described above, the substrates 1.2 were arranged so that the rubbing directions 7.8 were substantially parallel and opposite directions.

When we measured the electro-optical characteristics of the above liquid crystal device, it was found that ±1
Although the contrast was good at 25:1 for driving with a square wave of 0, as a result of observation with a polarizing microscope, more defect lines were observed than in Example 1 described above.

Therefore, by making the rubbing directions 7.8 of the substrates 1.2 in the same direction, the stress inside the liquid crystal can be more effectively relaxed, combined with the spiraling property of the liquid crystal itself, and the defect lines during molecular orientation can be removed. It's valid.

[Effects of the Invention] As explained above, according to the method for manufacturing a liquid crystal device of the present invention, by heat-treating the horizontal alignment layer after rubbing, the difference in depth of fine grooves on the surface of the horizontal alignment layer due to rubbing can be reduced. However, since the shape of the groove can be made smooth and the particles can be removed, the generation of defective lines becomes minute and a uniform alignment force can be obtained.

Therefore, if the method of the present invention is used, liquid crystal devices using ferroelectric liquid crystals, and furthermore, liquid crystal devices of the x-y simple matrix type that do not use active elements, with large display times, can be manufactured with high contrast.
It can be manufactured with high display quality.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a liquid crystal device according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of FIG. 1.2... Substrate 3.4... Electrode 5.6... Horizontal alignment layer 7.8... Rubbing direction 9... Ferroelectric liquid crystal 11.12... ...Polarizing plate Figure 1 Figure 2

Claims (3)

[Claims] (1) An alignment layer forming step of forming a horizontal alignment layer made of an organic material on two substrates, a rubbing step of rubbing the horizontal alignment layer formed on each substrate, and a horizontal alignment of each rubbed substrate. It is characterized by comprising a heat treatment step of heating the alignment layer, an assembly step of arranging these substrates so that the horizontal alignment layers face each other with a predetermined gap, and a liquid crystal filling step of filling the gap with liquid crystal. A method for manufacturing a liquid crystal device. (2) The method for manufacturing a liquid crystal device according to claim 1, wherein the heat treatment step is performed by maintaining a temperature of 100° C. to 350° C. for at least 30 minutes. (3) The assembly process is characterized in that the two substrates are arranged so that the directions of rubbing of the two substrates are substantially parallel and in the same direction.
A method for manufacturing a liquid crystal device as described in Section 1.