JP2000111920A - Liquid crystal element, and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of fine alignment defects. SOLUTION: This method for manufacturing comprises rubbing treatment on the surfaces of alignment films 2 in a manufacturing process of a ferroelectric liquid crystal panel. Microstructures of specified shapes (widths; >=1 nm and <=100 nm, depths; >=0.1 nm and <=20 nm, lengths; >=100 nm) are formed with >=5 grooves/1,000 nm density (i.e., numbers of grooves per 1,000 nm length in a direction perpendicularly intersecting a direction in which microstructures are formed) on the surfaces of the alignment films 2 with this rubbing treatment. Generation of fine alignment defects is prevented thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a liquid crystal device having an alignment film and a method for manufacturing the liquid crystal device.

[0002]

2. Description of the Related Art Since a TV image is a moving image with high definition and halftone, a device for displaying the TV image has high resolution, high response speed, high contrast and high reliability (high resolution, high speed response, (High contrast and high reliability), multi-tone display and color display must be possible, and a CRT has been used conventionally.

[0003] In recent years, demands for displaying such TV images on a large screen have been increasing, and accordingly, attention has been focused on liquid crystal elements as display devices that are lighter than CRTs. Recently, a method of displaying a TV image by using an active matrix type liquid crystal element (a switching element is provided for each pixel to directly drive a nematic liquid crystal) among liquid crystal elements has been actively studied recently. I have. As such a liquid crystal element, a TFT type is considered to be the most excellent,
Since the manufacturing process is complicated and requires a large number of processes, it is a great obstacle in mass-producing a large-screen liquid crystal element.

On the other hand, a liquid crystal panel (liquid crystal element) of a type that controls transmitted light by using the refractive index anisotropy of liquid crystal molecules exhibiting ferroelectricity and combining it with a polarizing element has been proposed by Clark and Lagerwall. Lagerwa
11) (JP-A-56-10721).
No. 6, US Pat. No. 4,367,924, etc.). This liquid crystal (hereinafter referred to as “ferroelectric liquid crystal”) generally has a non-helical chiral smectic C phase (SmC *) or H phase (SmH *) in a specific temperature range. Has a property of taking one of a first optical stable state and a second optical stable state in response to an applied electric field, and maintaining the state when no electric field is applied, that is, bistability; In addition, it responds quickly to changes in the electric field, and is expected to be widely used as a high-speed and storage-type liquid crystal panel. I have.

Incidentally, in the production of the above-mentioned liquid crystal panel, a rubbing treatment technique for imparting an alignment regulating force is very important. This rubbing technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-100228. ing.
Further, in order to prevent defects due to the mixture of the liquid crystal layer structures, for example, JP-A-8-43827 discloses the control of the number of surface irregularities.

[0006]

When the rubbing treatment is performed on the surface of the alignment film as described above, fine streaks are formed on the surface, but the shape of the streaks (ie, the thickness and depth of the streaks, etc.). The length and the like vary depending on the rubbing conditions, and the shape (that is, the surface shape of the alignment film) and the alignment state of the liquid crystal are closely related. In the case of a liquid crystal panel using a ferroelectric liquid crystal, there is a problem that minute alignment defects having different alignment angles depending on the surface shape of the alignment film (hereinafter, simply referred to as “fine alignment defects”) are likely to occur.

Accordingly, the present invention prevents the occurrence of minute alignment defects, realizes uniform and good alignment of liquid crystal, and achieves high reliability and high reliability.
It is an object to provide a high quality liquid crystal element.

Another object of the present invention is to provide a method of manufacturing a liquid crystal element which prevents the occurrence of micro-alignment defects, realizes uniform and good liquid crystal alignment, and manufactures a highly reliable and high quality liquid crystal element. It is intended for.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a pair of substrates arranged with a predetermined gap therebetween, and supports at least one of the pair of substrates. A liquid crystal element having a thickness of 1 nm or more and 100 nm or less and a depth of 0.1 nm or more and 2 nm or less.
Microstructures having a length of 0 nm or less and a length of 100 nm or more are formed on the surface of the alignment film at a density of 5/1000 nm or more.

Further, the present invention provides a process for forming an alignment film on one substrate, a process for performing a rubbing treatment on the surface of the formed alignment film, and a process for forming the alignment film between one substrate and another substrate. And a step of injecting a liquid crystal into the gap between these two substrates, wherein the rubbing treatment includes rubbing a rubbing cloth against the alignment film. And a thickness of 1 nm or more and 100 nm or less and a depth of 0.1 n
The microstructure having a length of 100 nm or more and a length of 100 nm or more was obtained by the rubbing treatment.
Formed on the surface of the alignment film at a density of 000 nm or more,
It is characterized by the following.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2,
An embodiment of the present invention will be described. Here, FIG.
FIG. 2 is a cross-sectional view illustrating an example of the structure of the liquid crystal element according to the present invention, and FIG. 2 is a plan view illustrating the structure of the liquid crystal element.

First, the structure of the liquid crystal element P according to the present invention will be described.

As shown in FIG. 1, a liquid crystal element P according to the present invention comprises a pair of substrates 1 arranged with a predetermined gap therebetween.
a, 1b, and an alignment film 2a or 2b is supported on at least one of the pair of substrates 1a or 1b (in the figure, the alignment films 2a and 2b are supported on both substrates 1a and 1b, respectively).
b are formed respectively), the pair of substrates 1a,
The liquid crystal 3 is arranged in the gap 1b. The thickness of the alignment films 2a and 2b is 1 nm or more and 100
5 microstructures with a depth of 0.1 nm to 20 nm and a length of 100 nm or more
It is formed with a density of 00 nm or more (meaning the number per 1000 nm length in a direction perpendicular to the direction in which the microstructures are formed; the same applies hereinafter) (details will be described later).

Here, as the liquid crystal 3, a ferroelectric liquid crystal having anti-spontaneous polarization or an antiferroelectric liquid crystal is used as the alignment film 2a,
As 2b, a polyimide film can be mentioned. Further, a glass substrate can be used as the substrates 1a and 1b.

The electrodes 4a and 4a are provided on the surfaces of the substrates 1a and 1b.
4b, or insulating films 5a, 5b may be formed so as to cover the electrodes 4a, 4b. In such a case, the above-mentioned alignment films 2a, 2b are used to form the electrodes 4a, 4b.
b and the insulating films 5a and 5b may be formed.

A plurality of electrodes 4a, 4b are formed on both substrates 1a, 1b, respectively, and these electrodes 4a, 4b are formed.
A simple matrix may be formed by a and 4b (see FIG. 2). Further, the gap between the substrates 1a and 1b may be sealed with the seal adhesive 5. Further, a spacer 6 may be arranged in the gap between the substrates, and the gap between the substrates may be defined by the spacer 6. Further, coating type insulating films 7a and 7b for assisting short-circuit prevention may be formed on the surface of the above-mentioned insulating films 5a and 5b. May contain fine particles having a diameter of several hundreds of millimeters.

In the liquid crystal element P according to the present invention, specific members (for example, substrates, electrodes, insulating films, alignment films, etc.)
This includes the case where two substrates are provided, one for the upper substrate and the other for the lower substrate. However, in this specification, "a" and "b" are added when it is necessary to distinguish them. They are distinguished by a code (for example, substrate 1a, substrate 1
b) When there is no need for distinction, it is simply represented by a numeral (for example, substrate 1).

Next, a method for manufacturing a liquid crystal element according to the present invention will be described.

First, an alignment film 2a is formed on one substrate 1a, and the surface of the formed alignment film 2a is subjected to a rubbing treatment.

The rubbing treatment is performed by rubbing a rubbing cloth against the alignment film 2a, and the rubbing treatment causes microstructures (thickness of 1 nm or more and 100 nm or less and depth of 0.1 nm or less) on the surface of the alignment film 2a. (The length is not less than 20 nm and the length is not less than 100 nm) at a density of 5 lines / 1000 nm or more. In order to form the microstructure at such a density, the moving speed of the rubbing cloth (for example, when the rubbing cloth is wound around a roller and the roller is rotated) is increased, Relative speed to the substrate 1a (for example, when the roller is stopped at a fixed position and the substrate 1a is moved, the moving speed of the substrate 1a is meant.
In the case where the roller is stopped at a fixed position and the roller is moved, the moving speed of the roller is reduced), and the rubbing density may be increased. Here, the appropriate range of the rubbing conditions such as the moving speed of the rubbing cloth and the relative speed between the rubbing cloth and the substrate 1a (the range in which the microstructure is formed at the above density) is determined by the surface shape of the alignment film surface and the Since it greatly differs depending on the material and the shape of the rubbing cloth, it is necessary to make it different according to them.

Then, the one substrate 1a on which the alignment film 2a is formed and the other substrate 1b are bonded together with a predetermined gap therebetween, and the liquid crystal 3 is inserted into the gap between the two substrates 1a and 1b. Inject.

Next, the effect of this embodiment will be described.

According to the present embodiment, the occurrence of minute alignment defects can be suppressed, and a uniform and favorable alignment state can be obtained. Further, a liquid crystal element having good driving characteristics and high reliability and image quality can be obtained.

[0024]

The present invention will be described below in more detail with reference to examples.

Example 1 In this example, a liquid crystal panel (liquid crystal element) shown in FIG. 1 was prepared. That is, a large number of transparent electrodes 4a, 4a are provided on the surface of each of the substrates 1a, 1b.
4b, inorganic insulating films 5a and 5b for short-circuit prevention and coating-type insulating films 7a and 7b for assisting short-circuit prevention were formed so as to cover the transparent electrodes 4a and 4b. The alignment films 2a and 2b were formed on the surfaces of the coating type insulating films 7a and 7b. Further, a large number of bead spacers 6 are arranged in the substrate gap, and the bead spacers 6 define the substrate gap. Further, the substrates 1a, 1
A seal adhesive 5 was disposed at the end of the portion b, and the gap between the substrates was sealed by the seal adhesive 5.

The substrates 1a and 1b have a thickness of 1.1.
mm glass substrate, and striped ITO (indium tin oxide) is used for the transparent electrodes 4a and 4b.
Was used. Further, Ta ₂ O ₅ is formed on the inorganic insulating films 5a and 5b.
As the coating type insulating films 7a and 7b, Ti-Zr-Si based coating type insulating films (thickness: about 170 °) containing SiO ₂ fine particles having a diameter of 500 ° were used. Further, the alignment film 2
For a and 2b, a polyimide film with a thickness of about 200 ° is used.
As the liquid crystal 3, a ferroelectric liquid crystal was used.

Next, a method of manufacturing the liquid crystal panel according to the present embodiment will be described.

First, an ITO film is formed to a thickness of about 700 ° on the surface of the glass substrate 1 by using the sputtering method.
The transparent electrode 4 was formed by patterning the film by photolithography.

Next, an inorganic insulating film 5 was formed to a thickness of about 900 ° by a sputtering method, and a coating type insulating film 7 was formed by a printing method. Then, as described above, the insulating film 5
The glass substrate 1 on which the above and the like were formed was fired.

Further, a polyimide film was applied by a printing method, and was baked to form an alignment film 2.

Thereafter, the surface of the alignment film 2 was subjected to a rubbing treatment. At the time of this rubbing treatment, two rollers having a rubbing cloth (a cotton cloth having a thickness of 3.3 mm) wound on the outer peripheral surface are rotated in the same direction, and the glass substrate 1 (exactly Presses the alignment film 2) formed on the glass substrate 1 and, in that state,
Was moved (in a direction that does not oppose the rotation of the roller). The amount of the rubbing cloth pushed into the surface of the alignment film 2 was set to about 1.9 mm, and the rotation speed of the roller was set to 11.
7 rotations / sec, and the feed speed of the glass substrate 1 is 10 mm
/ Sec.

After the completion of the rubbing process, the AFM
The surface shape of the alignment film 2 was measured. According to the measurement, it was found that countless fine streaks (microstructures) were formed on the surface of the alignment film 2 in a direction of about 60 ° with respect to the horizontal axis, as shown in FIG. These microstructures are recessed and groove-shaped, have a thickness of about 10 nm, a depth of several nm,
The length was 100 nm or more. Further, the density (the number per 1000 nm length in a direction orthogonal to the direction in which the microstructures are formed; the same applies hereinafter)
Was 13 lines / 1000 nm on average. Further, the pretilt angle was 14.5 °.

In this way, two glass substrates 1 on which the electrodes 4 and the like were formed were prepared. On one glass substrate 1a, 300 silica beads having an average particle size of 1.25 × 10 ³ nm were formed. / Mm ² , and a sealing adhesive 5 is applied to the other glass substrate 1b.
1b was bonded to form a liquid crystal cell. Then, the ferroelectric liquid crystal 3 was injected into the liquid crystal cell thus formed.

Next, the effect of this embodiment will be described.

According to this embodiment, the occurrence of minute alignment defects can be suppressed, and a uniform and favorable alignment state can be obtained.
That is, a liquid crystal panel having good driving characteristics and high reliability and image quality could be produced.

(Embodiment 2) The liquid crystal panel produced in this embodiment has the same structure as that of Embodiment 1.

The manufacturing method was the same as that of Example 1 except for the rubbing treatment.

That is, the rubbing treatment uses the same rubbing cloth (cotton cloth having a thickness of 3.3 mm) and the rollers (two rollers) as in Example 1, and the same rotation speed of the rollers (11. 7 revolutions / sec), but the amount of pushing of the rubbing cloth was about 1.6 mm, and the feed speed of the substrate 1 was 30 mm / sec.

Further, the surface shape of the alignment film 2 was measured by AFM in the same manner as in Example 1. As shown in FIG. It turned out that countless fine streaks (microstructures) were formed. These microstructures were dented and groove-shaped, and the thickness, depth, and length were almost the same as those in Example 1 (thickness was about 10 nm, depth was several nm, and length was 100 nm or more). . The average density of the microstructure was 10 lines / 1000 nm, and the pretilt angle was 27.6 °.

According to this embodiment, substantially the same effects as those of the first embodiment were obtained.

(Embodiment 3) The liquid crystal panel produced in this embodiment has the same structure as that of the first embodiment.

The manufacturing method was the same as that of Example 1 except for the rubbing treatment.

That is, the rubbing treatment uses the same rubbing cloth (cotton cloth having a thickness of 3.3 mm) and a roller (two rollers) as in Example 1, and the same rotation speed of the roller (11. 7 rotations / sec), but the amount of rubbing cloth pushed in was about 1.7 mm, and the feed speed of the substrate 1 was 50 mm / sec.

Further, the surface shape of the alignment film 2 was measured by AFM in the same manner as in Example 1. As shown in FIG. 5, the surface was oriented at about 60 ° with respect to the horizontal axis. It was found that some somewhat rough streaks (microstructures) were formed. These microstructures have a concave groove shape, a thickness of about 20 nm, and a depth and a length which are almost the same as those of the first embodiment (depth: several n
m, length; 100 nm or more). The density of the microstructure was 5 lines / 1000 nm on average, and the pretilt angle was 31.4 °.

According to the present example, in the initial alignment inspection, a thin streak-like minute alignment defect was observed on the entire surface, but when driven, it was inverted and barely a problem as a panel.

Comparative Example In this comparative example, the coating type insulating films 7a and 7b used were Ti-Si based materials having a thickness of about 650 °. Other structures were the same as those of Example 1 and the like.

The manufacturing method was the same as that of Example 1 except for the rubbing treatment.

That is, the rubbing treatment uses the same rubbing cloth (cotton cloth having a thickness of 3.3 mm) and rollers (two rollers) as in Example 1, and the rotation speed of the rollers is the same (11. 7 revolutions / sec), but the amount of pushing of the rubbing cloth was about 0.8 mm, and the feed speed of the substrate 1 was 70 mm / sec.

Further, the surface shape of the alignment film 2 was measured by AFM in the same manner as in Example 1, and as shown in FIG. It was found that one streak (microstructure) was formed. This microstructure had a concave groove shape, and the thickness, depth and length were almost the same as those in Example 3 (thickness: about 20 nm, depth: several nm, length: 100 nm or more). The microstructure has an average density of 1 line / 1000 nm and a pretilt angle of 3 nm.
1.0 °.

According to this comparative example, a number of streak-like micro-alignment defects were observed, and the micro-defect portions did not reverse during driving, which was a problem as a panel.

[0051]

As described above, according to the present invention,
The generation of minute alignment defects can be suppressed, and a uniform and favorable alignment state can be obtained. Further, a liquid crystal element having good driving characteristics and high reliability and image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the structure of a liquid crystal element according to the present invention.

FIG. 2 is a plan view showing the structure of the liquid crystal element of FIG.

FIG. 3 is a photograph replacing a drawing showing a particle structure on the surface of an alignment film.

FIG. 4 is a photograph replacing a drawing showing a particle structure on the surface of an alignment film.

FIG. 5 is a photograph replacing a drawing showing a particle structure on the surface of an alignment film.

FIG. 6 is a photograph replacing a drawing showing a particle structure on the surface of an alignment film.

[Explanation of symbols]

 1a, 1b Glass substrate (substrate) 2a, 2b Alignment film 3 Ferroelectric liquid crystal (liquid crystal) P Liquid crystal panel (liquid crystal element)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA03 FA10 HA01 HA02 HA03 HA04 JA17 JA20 KA30 MA04 MA18 2H090 HA03 HA14 HB04X HB06X HB08Y HB17X HC05 HD14 JB02 KA14 KA15 LA01 LA02 LA03 MB01 4J043 ZB11 ZB23

Claims (6)

[Claims] A pair of substrates arranged with a predetermined gap therebetween, an alignment film supported on at least one of the pair of substrates, and a liquid crystal arranged in a gap between the pair of substrates. A microstructure having a thickness of 1 nm or more and 100 nm or less, a depth of 0.1 nm or more and 20 nm or less, and a length of 100 nm or more is provided on the surface of the alignment film by 5 lines / 1000 nm.
A liquid crystal element formed with the above density. 2. The liquid crystal device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal having spontaneous polarization or an antiferroelectric liquid crystal. 3. The liquid crystal device according to claim 1, wherein the alignment film is a polyimide film. 4. A step of forming an alignment film on one substrate, a step of performing a rubbing treatment on a surface of the formed alignment film, and a predetermined gap between the one substrate on which the alignment film is formed and another substrate. In a method for manufacturing a liquid crystal element, comprising: a step of bonding in an open state, and a step of injecting liquid crystal into a gap between these two substrates, wherein the rubbing treatment is performed by rubbing a rubbing cloth against the alignment film, In addition, 5/100 microstructures having a thickness of 1 nm or more and 100 nm or less, a depth of 0.1 nm or more and 20 nm or less, and a length of 100 nm or more are obtained by the rubbing treatment.
A method for producing a liquid crystal element, comprising: forming a film at a density of 0 nm or more on the surface of the alignment film. 5. The method according to claim 4, wherein the liquid crystal is a ferroelectric liquid crystal having spontaneous polarization or an antiferroelectric liquid crystal. 6. The method according to claim 4, wherein the alignment film is a polyimide film.