JPH11142852A - Liquid crystal element and production of this liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the nonuniformity of the alignment state of chiral smectic liquid crystals. SOLUTION: A uniaxial alignment layer 7 is subjected to a rubbing treatment in a production process, by which a uniaxial alignment characteristic is imparted to liquid crystal molecules. A material of which the change in the dispersion term of the surface energy by the occurrence of film peeling attains <=4 dyne/cm by the rubbing treatment is used for the uniaxial alignment layer 7. Then, even if the film peeling is locally induced by the rubbing treatment, the difference in the surface energy between the part where the film peeling occurs and the part where the film peeling does not occur is small and the nonuniformity of the alignment state of the chiral smectic liquid crystals is lessened.

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 a chiral smectic liquid crystal and a method for manufacturing the liquid crystal device.

[0002]

2. Description of the Related Art A liquid crystal element in which transmitted light is controlled by combining with a polarizing element by utilizing the refractive index anisotropy of liquid crystal molecules has been proposed by Clark and Lagerwall (see, for example, Japanese Patent Application Laid-Open (Kokai) No. 2002-209, 1988). JP-A-56-107216, U.S. Pat.
No. 4 specification).

The chiral smectic liquid crystal used in this liquid crystal element generally has a non-helical structure chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range, and is added in this state. Has a property of taking one of a first optically stable state and a second optically stable state in response to an electric field and maintaining the state when no electric field is applied, that is, has bistable stability; It responds quickly to changes in the electric field, and is expected to be widely used as a liquid crystal for high-speed and storage devices.

The liquid crystal element has a matrix electrode composed of a scanning electrode and a signal electrode. A scanning signal is sequentially applied to the scanning electrode, and an information signal is applied to the signal electrode in synchronization with the scanning signal. Then, the chiral smectic liquid crystal is driven by multiplexing.

In such a liquid crystal device, it is necessary to form a uniaxial alignment film on at least one of the substrates and to perform a uniaxial alignment treatment on the alignment film to properly align the liquid crystal molecules. As such a uniaxial orientation method, there are various methods such as a rubbing treatment method, an oblique vapor deposition method, and an ion beam method. The rubbing treatment method requires only rubbing a rubbing cloth against a uniaxial orientation film, and the work is simple. Therefore, it is generally used.

In this rubbing treatment, usually 10 to 10
A rubbing cloth having a brushed pile having a thickness of about 0 μm is used. In order to achieve a uniform rubbing treatment, a brushed pile having a thickness of about 10 μm is preferable, and a large number of brushed piles are planted at high density. It is necessary to use a rubbing cloth.

[0007]

Since the composition (film composition) and structure (film structure) of the uniaxially oriented film 3 are not uniform in the direction of the film surface when viewed microscopically, the rubbing treatment is performed on the uniaxially oriented film 3. Even if the film is uniformly applied to the entire surface of the film, a portion where the film is separated and a portion where the film is not separated are mixed on the surface of the uniaxially oriented film 3. On the other hand, the dispersion term of the surface energy in the uniaxially oriented film 3 changes when the film is peeled off by the rubbing treatment. Is non-uniform, and as a result, there is a problem that the alignment state of the liquid crystal becomes non-uniform.

By the rubbing treatment, the main chain of the organic polymer on the new surface is stretched in the portion where the film has peeled off, and the organic polymer on the surface where the film has not peeled off in the portion where the film does not peel off Will be stretched.

Accordingly, an object of the present invention is to provide a liquid crystal device having high display quality by reducing the non-uniformity of the alignment state of the liquid crystal.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and includes a pair of substrates arranged at a predetermined distance and at least one of the pair of substrates. A liquid crystal device comprising: a uniaxial alignment film provided with uniaxial alignment characteristics for liquid crystal molecules by rubbing treatment; and a chiral smectic liquid crystal disposed between the pair of substrates so as to be in contact with the uniaxial alignment film. In the uniaxially oriented film, the change in the dispersion term of the surface energy due to the peeling of the film by the rubbing treatment is 4%.
dyne / cm or less.

[0011]

Embodiments of the present invention will be described below with reference to FIG.

FIGS. 1A and 1B are diagrams showing the structure of a liquid crystal element according to the present embodiment, wherein FIG. 1A is a front view and FIG. 1B is a bottom view.

As is apparent from FIG. 1, the liquid crystal element P according to the present embodiment includes a pair of substrates 1 and 2 which are arranged at a predetermined distance from each other. On one substrate 1, a uniaxial alignment film 3 to which uniaxial alignment characteristics for liquid crystal molecules are imparted by a rubbing process as described later is formed. A chiral smectic liquid crystal 5 is disposed between the pair of substrates 1 and 2 so as to be in contact with the uniaxial alignment film 3.

By the way, the dispersion term of the surface energy in the uniaxially oriented film 3 changes when the film peels off by the rubbing treatment. A material having a term change of 4 dyne / cm or less is used. The uniaxial alignment film 3 may be made of an inorganic material such as silicon monoxide, silicon dioxide, aluminum oxide, or cerium oxide, or an organic material such as polyvinyl alcohol, polyimide, or polyimide amide.

Further, the uniaxial alignment film 3 is formed on both substrates 1,
The uniaxial alignment film 3 may be formed only on one substrate 1, and the other substrate 2 may be formed with a non-uniaxial alignment film 6 having non-uniaxial alignment characteristics with respect to liquid crystal molecules. You may make it. Here, these uniaxially oriented films 3
The non-uniaxial alignment film 6 may be formed of an organic film or an inorganic film.

In the present specification, "uniaxial orientation characteristics"
The term means a property of bringing the liquid crystal molecules into a uniaxial alignment state (for example, a uniaxial horizontal alignment state).

The substrates 1 and 2 may be made of glass or plastic.

Further, electrodes 7 and 9 may be formed on the surfaces of these substrates 1 and 2. The electrodes 7 and 9 include I
A transparent conductor such as TO (indium tin oxide) is preferred.

The chiral smectic liquid crystal 5 includes S
In the mC ^* phase, a liquid crystal material having a bookshelf structure in which the smectic layers are vertically arranged in parallel with the substrate or a structure in which the smectic layer is inclined nearly perpendicularly may be used. As such a liquid crystal material, for example, a fluorine-containing liquid crystal compound comprising a fluorocarbon terminal chain having at least one ether oxygen in the chain and a hydrocarbon terminal chain, wherein the terminal chains are bonded by a central nucleus;
A liquid crystal composition containing a compound exhibiting a smectic intermediate phase or a latent smectic phase can be given.

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

In manufacturing the liquid crystal element P, one substrate 1
Then, a uniaxial alignment film 3 is formed, and a rubbing process is performed on the uniaxial alignment film 3 to impart uniaxial alignment characteristics to liquid crystal molecules. Then, the one substrate 1 and the other substrate 2 are bonded to each other with a predetermined distance therebetween, and a chiral smectic liquid crystal is injected between the substrates 1 and 2 (a position in contact with the uniaxial alignment film 3).

Next, the effect of this embodiment will be described.

According to the present embodiment, since the uniaxially oriented film 3 having a change in the dispersion term γ _d of the surface energy of 4 dyne / cm or less due to the peeling of the film is used, the peeling of the film occurs by the rubbing treatment. Even if a portion and a portion that does not occur are mixed, the surface energy can be made substantially uniform, and the alignment state of the liquid crystal 5 can be made uniform. as a result,
The display quality of the liquid crystal element P is improved.

[0024]

Embodiment (Embodiment 1) A liquid crystal element P according to this embodiment is
Glass substrates 1 and 2 are used as substrates, and the surfaces of these glass substrates 1 and 2 are coated with ITO (indium tin).
Oxide) were formed. In addition, these transparent electrodes 7 and 9 were arranged so as to be orthogonal to each other.

The uniaxial alignment film 3 was formed only on one glass substrate 1 and so as to cover the transparent electrode 7.
The uniaxial alignment film 3 is formed of polyimide having the following structure.

[0026]

Embedded image The film thickness was about 5 × 10 ³ μm. This uniaxial alignment film 3
Is subjected to a rubbing treatment as described later, but the present inventor determines the value of the dispersion term of the surface energy by a predetermined method (Mr. Kitazaki, Journal of the Adhesion Society of Japan, 8 (3), 131-141 (197)
The measured and calculated values in 2)) were 44.3 dyne / cm before the rubbing treatment and no film separation, and 44.3 dyne after the rubbing treatment and film separation.
4.5 dyne / cm and the difference is 0.2 dyn
e / cm.

Further, a non-uniaxially oriented film 6 was formed on the other glass substrate 3 so as to cover the transparent electrode 9. The non-uniaxially oriented film 6 was formed of a silica film in which antimony-doped SnO ₂ ultrafine particles were dispersed, and the particle size of the SnO ₂ ultrafine particles was about 10 × 10 ³ μm. In addition, the non-uniaxial alignment film 6
Was about 150 × 10 ³ μm.

On the other hand, a spacer (not shown) made of silica beads having an average particle size of 2.6 μm is arranged between these glass substrates 1 and 2, and this spacer is used to make a gap between the two glass substrates 1 and 2. Stipulated.

Further, a sealing material 10 having a shape shown in FIG. 1A was disposed in the gap between the glass substrates 1 and 2, and the two glass substrates 1 and 2 were bonded by the sealing material 10. Note that an epoxy resin adhesive was used for the sealing material 10. Reference numeral 11 in the figure denotes an injection port for injecting the chiral smectic liquid crystal 5.

Further, a polyfluorinated liquid crystal 5 was used. The following compounds are represented by A, B ₁ , B ₂ , B ₃ ,
C, their weight ratio in the liquid crystal 5 A /
Was _{B 1 / B 2 / B 3} / C of 80/3/3/4/5.
The spontaneous polarization of the composition at 25 ° C. was 26 nC / cm.
^2. The layer inclination angle δ at 20 ° C. was 0 °, and the tilt angle was 27 °.

[0031]

Embedded image Next, a method for manufacturing the liquid crystal element P will be described.

First, a glass substrate 1 was formed by sputtering.
On the surface of No. 2, an ITO film having a thickness of 100 × 10 ³ μm was formed, and this was patterned by photolithography to form transparent electrodes 7 and 9.

Next, a polyimide film was applied to the surface of one of the glass substrates 1 by a spinner so as to cover the transparent electrode 7, and was subjected to a heating and baking treatment to form a uniaxially oriented film 3. Then, the surface of the uniaxial alignment film 3 has a diameter of about 15
A rubbing treatment was performed by rubbing with a rubbing cloth made of a nylon pile of μm.

On the other glass substrate 3, a silica solution in which antimony-doped SnO ₂ ultrafine particles were dispersed was applied by a spinner, and this was heated and dried to form a non-uniaxially oriented film 6. The non-uniaxial alignment film 6 was not subjected to a rubbing process.

Then, spacers were scattered on one glass substrate 1 and a sealing material 10 was applied on the other glass substrate 3, and these glass substrates 1 and 2 were bonded.

Thereafter, a chiral smectic liquid crystal 5 was injected between the substrates 1 and 2, and the injection port 11 was sealed.

According to the present embodiment, the same effects as those of the above-described embodiment of the present invention can be obtained. In addition, when the orientation state of the liquid crystal element P was observed with a polarizing microscope and the number of defects was counted,
It was found that the alignment state was as small as about 0.1 / cm ² , indicating a uniform alignment state. (Embodiment 2) In this embodiment, the uniaxial alignment film 3 was formed of polyimide having the following structure.

[0038]

Embedded image The inventor of the present invention measured and calculated the value of the dispersion term of the surface energy for the uniaxially oriented film 3 in the same manner as described above. As a result, before the rubbing treatment and no film peeling, the value was 43.2 dyne / cm. In the state after the rubbing treatment and the film was peeled off, it was 44.7 dyne / cm, and the difference was 1.5 dyne / cm.

The rest of the structure and the manufacturing method were the same as in the first embodiment.

According to this embodiment, the same effects as those of the above-described embodiment of the present invention can be obtained. In addition, when the orientation state of the liquid crystal element P was observed with a polarizing microscope and the number of defects was counted,
It was found to be as small as about 0.5 particles / cm ² , indicating a uniform alignment state. (Comparative Example 1) Here, the change in the dispersion term of the surface energy due to the peeling of the film caused by the rubbing treatment was 4 dy.
Experimental results in the case where a uniaxial alignment film having a ne / cm or more is used will be described as “Comparative Example 1” and “Comparative Example 2”.

In this comparative example, the uniaxial alignment film 3 is
1800 (manufactured by Hitachi Chemical Co., Ltd.). When the present inventor measured and calculated the value of the dispersion term of the surface energy for the uniaxially oriented film 3 in the same manner as described above, it was 37.1 dyne / cm before the rubbing treatment and without film peeling. Yes, 42.4 dyne / cm after rubbing and with film peeling
And the difference was 5.3 dyne / cm.

Other structures and the manufacturing method were the same as those in the first embodiment.

According to this comparative example, the uniaxiality of the liquid crystal 5 was partially weakened, and many alignment defects occurred. When the alignment state of the liquid crystal element P was observed with a polarizing microscope and the number of defects was counted, it was found that the number was as large as about 120 / cm ² . (Comparative Example 2) In this comparative example, the uniaxially oriented film 3 was LX
-S401 (made by Hitachi Chemical Co., Ltd.). The inventor measured and calculated the value of the dispersion term of the surface energy for the uniaxially oriented film 3 by the same method as described above. As a result, before the rubbing treatment and without film peeling, the value was 32.5 dyne / cm. Yes, 43.3 dyne / c after film rubbing and film peeling
m, and the difference was 10.8 dyne / cm.

The other structures and the manufacturing method were the same as in the first embodiment.

According to this comparative example, the uniaxiality of the liquid crystal 5 was partially weakened, and many alignment defects occurred. When the orientation state of the liquid crystal element P was observed with a polarizing microscope and the number of defects was counted, it was found that the number was as large as about 220 / cm ² . (Embodiment 3) In this embodiment, the uniaxial alignment film 3 was formed of polyimide having the following structure.

[0046]

Embedded image Further, the inventor measured and calculated the value of the dispersion term of the surface energy for the uniaxially oriented film 3 in the same manner as described above, and found that the value was 40.5 dyne / cm before the rubbing treatment and no film peeling. In the state after the rubbing treatment and the film was peeled off, it was 44.5 dyne / cm, and the difference was 4.0 dyne / cm.

The other structure and manufacturing method were the same as those in the first embodiment.

According to this embodiment, the same effects as those of the above-described embodiment of the present invention can be obtained. The number of defects was counted by observing the alignment state of the liquid crystal element P with a polarizing microscope.
Particles / cm ^2, which was small, indicating a uniform alignment state. (Embodiment 4) In this embodiment, the non-uniaxial alignment film 6 is not used, and instead, the uniaxial alignment film 3 is formed on both the glass substrates 1 and 2 so as to cover the transparent electrodes 7 and 9, respectively. The uniaxial alignment film 3 was subjected to a rubbing treatment. The uniaxial alignment film 3
The same one as in Example 1 was used.

The other structure and manufacturing method were the same as those in the first embodiment.

According to this embodiment, the same effects as those of the above-described embodiment of the present invention can be obtained. In addition, when the orientation state of the liquid crystal element P was observed with a polarizing microscope and the number of defects was counted,
It was found to be as small as about 0.9 / cm ² , indicating a uniform alignment state.

[0051]

As described above, according to the present invention,
The alignment state of the chiral smectic liquid crystal becomes uniform, and the display quality of the liquid crystal element is improved.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a structure of a liquid crystal element, wherein FIG. 1A is a front view and FIG. 1B is a bottom view.

[Explanation of symbols]

 1a, 1b Glass substrate (substrate) 3 Uniaxial alignment film 5 Chiral smectic liquid crystal 6 Non-uniaxial alignment film P Liquid crystal element

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumikazu Kobayashi Canon Inc. 3- 30-2 Shimomaruko, Ota-ku, Tokyo

Claims (5)

[Claims] A pair of substrates arranged at a predetermined distance from each other; a uniaxial alignment film formed on at least one of the pair of substrates and provided with uniaxial alignment characteristics for liquid crystal molecules by a rubbing process; A chiral smectic liquid crystal disposed between the pair of substrates so as to be in contact with the uniaxial alignment film, wherein the uniaxial alignment film has a dispersion term of surface energy due to peeling of the film due to rubbing treatment. Change of 4dyn
e / cm or less. 2. The method according to claim 1, wherein the uniaxial alignment film is formed only on one of the pair of substrates, and a non-uniaxial alignment film having non-uniaxial alignment characteristics on liquid crystal molecules is formed on the other substrate. The liquid crystal device according to claim 1, wherein: 3. The liquid crystal device according to claim 2, wherein the uniaxial alignment film and the non-uniaxial alignment film are formed of an organic film or an inorganic film. 4. The liquid crystal is a fluorine-containing liquid crystal compound comprising at least one fluorocarbon terminal chain having ether oxygen in the chain and a hydrocarbon terminal chain, wherein the terminal chains are bonded by a central nucleus, and the compound is The liquid crystal device according to any one of claims 1 to 3, wherein the liquid crystal composition contains a liquid crystal composition exhibiting a smectic intermediate phase or a latent smectic phase. 5. A step of forming a uniaxial alignment film on one substrate, a step of subjecting the uniaxial alignment film to rubbing treatment to impart uniaxial alignment characteristics to liquid crystal molecules, and A method of manufacturing a liquid crystal device, comprising: a step of bonding in a state separated by a predetermined distance, and a step of injecting a chiral smectic liquid crystal between these substrates at a position in contact with the uniaxial alignment film, wherein the uniaxial alignment film is The change in the dispersion term of the surface energy due to the film peeling caused by the rubbing treatment is 4d.
yne / cm or less.