JPH04240620A - Liquid crystal oriented film - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal element which can make uniform display by uniformizing the orientation of the liquid crystal molecules near oriented films. CONSTITUTION:The liquid crystal oriented films 10, 11 of the liquid crystal element formed by sealing a liquid crystal 9 between electrode substrates 1 and 2 are constituted by laminating electrode substrates 3, 4, org. resin films 5, 6 and layers 7, 8 consisting of extremely thin org. low moleculars in this order. The layers 7, 8 consisting of the org. low polymers which are as extremely thin as preferably about monomolecular layers are formed by adsorbing the org. low polymers on the surfaces of the org. resin films or bringing the functional groups existing on the surfaces and the org. low moleculars into reaction. The org. low moleculars are preferably an amine compd. and more particularly primary amine compd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device. In particular, it relates to the orientation of liquid crystal molecules, which affects the characteristics of liquid crystal elements.

0002

2. Description of the Related Art Conventionally, a liquid crystal element can be obtained by filling a gap between two substrates with a liquid crystal composition. In this case, alignment films that are generally used are often composed of a single polyimide material that has been rubbed, that is, its main chain has been stretched.

The concept of alignment films for liquid crystal molecules is detailed in ``Fundamentals and Applications of Liquid Crystal Electronics'' edited by Akio Sasaki.

0004

Problems to be Solved by the Invention In nematic liquid crystal elements and ferroelectric liquid crystal elements, the alignment of liquid crystal molecules near the alignment film is not uniform, and therefore it is often difficult to display a uniform liquid crystal element.

[0005] This indicates that in the conventional alignment technology, there is a limit to the uniformity of alignment of liquid crystal molecules in the vicinity of the alignment film.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the liquid crystal alignment film of the present invention is a liquid crystal alignment film provided in a liquid crystal element formed by sealing liquid crystal between opposing electrode substrates, This is characterized by laminating in this order an electrode substrate, an organic resin film, and an extremely thin organic low-molecular layer.

[0007] In order to form an extremely thin, preferably monomolecular layer of organic low molecules, organic low molecules can be adsorbed onto the surface of an organic resin film, or organic low molecules can be combined with functional groups present on the surface. It is desirable to react.

[0008] The organic low molecule is preferably an amine compound. In particular, primary amine compounds are more desirable. As a method for adsorbing the organic low molecule on the surface of the organic resin film or reacting the organic low molecule with a functional group present on the surface, it is desirable to expose it to a gas (vapor) of the primary amine compound, In this case, the primary amine is preferably benzylamine or cyclohexylamine (in the sense that it has a high vapor pressure).

As the organic resin film, at least a rubbed polyimide film, a rubbed polyamide film,
A rubbed polyacrylonitrile film or a rubbed polyparabanic acid resin film is desirable.

As the liquid crystal material used, nematic liquid crystal or ferroelectric liquid crystal is suitable.

[0011] It is possible to form a layer made of polyacrylonitrile containing an antistatic agent, rub this layer, and then adsorb a vertical alignment agent to the surface of the layer to use it as the above-mentioned organic resin film.・Twisted nematic mode (STN) and surface
It is quite effective in stabilized ferroelectric liquid crystal mode (SSFLC).

[0012] Furthermore, a layer made of polyparabanic acid resin containing an antistatic agent is formed, and this is further rubbed,
Furthermore, it is possible to use a material obtained by adsorbing a vertical alignment agent on the layer surface as the above-mentioned organic resin film, such as STN and SSFL.
It is quite effective for C.

[0013] The rubbing operation is to stretch the main chain of the macromolecules constituting the layer. This is revealed by birefringence measurements.

[0014]

[Operation] When using the current rubbing method, that is, stretching an organic resin film by friction using a fiber bundle, it seems to be difficult to achieve microscopically uniform stretching. In fact, this stretching imparts directionality to the arrangement of liquid crystal molecules in contact with it. As another degree of freedom in the arrangement of liquid crystal molecules, there is another parameter called the pretilt angle at the interface of the organic resin film.

It is thought that the interaction between the organic resin film molecules and the liquid crystal molecules at the interface determines the alignment of the liquid crystal molecules.
This is thought to originate from the electrical interaction (so-called dispersion force) between permanent dipoles or induced dipoles of each other's molecules.

[0016] It seems that the arrangement of liquid crystal molecules by the current rubbing method lacks uniformity. That is, when considered microscopically, it seems difficult to control the properties of organic resin film molecules at the interface.

The author did not bring the surface of the organic resin film into direct contact with the liquid crystal molecules, but instead interposed a layer of different molecules, ideally a monomolecular layer, between them as a buffer, and as a result, the organic resin film and the liquid crystal molecules The aim is to equalize the interactions between the two.

It is understood that primary amines having strong ionicity, ie, a large permanent dipole moment, are effective as organic low molecules. It is also desirable that the organic resin film has a considerable density of cyano groups, ketone groups, carboxyl groups, etc.

[0019]

[Examples] Examples of the present invention will be described below.

FIG. 1 is a sectional view showing a liquid crystal element obtained according to an embodiment of the present invention. In the figure, 1 and 2 are, for example, first and second substrates made of transparent glass; 3 and 4;
is a rectangular transparent conductive electrode made of, for example, an ITO film on the main surface; 5 and 6 are organic resin films; 7 and 8 are layers made of organic low molecules; and 9 is a liquid crystal layer. 5 and 7, and 6 and 8 constitute liquid crystal alignment films 10 and 11.

(Example 1) Nylon 6.6 resin was dissolved in metacresol to obtain a 2% nylon 6.6 varnish, and polyacrylo resin (PAN) was further dissolved in normal methyl pyrrolidone (NMP). A 2% PAN varnish was obtained. Polyparabanic acid resin (product name Sollac)
NMP solution was obtained from Tonen Petrochemical. This was further diluted with NMP to obtain a 2% varnish.

Each of them was applied using a spinner onto the main surfaces of glass substrates 1 and 2 having microfabricated ITO electrodes 3 and 4 as base materials, and heated (heating temperature was about 150° C. for about 20 minutes). The film thickness was approximately 400 nm.

Next, a normal rubbing treatment was performed. Glass substrates 1 and 2 are bonded together with a predetermined gap so that their main surfaces face each other. As the sealing resin, an epoxy resin that can be cured at about 150° C. for 3 hours was used. Next, it was exposed to cyclohexylamine gas at room temperature for 48 hours. In this case, the cyclohexylamine solution and the bonded glass substrate were allowed to coexist in a sealed container. That is, the bonded glass substrates were placed in a rich cyclohexylamine gas atmosphere.

Next, the gap is filled with a nematic liquid crystal composition. A liquid crystal element is thus obtained. Said ITO
A voltage is applied to the electrodes and observed by sandwiching them between polarizing plates.

[0025] The uniformity of the display characteristics of the liquid crystal elements was significantly superior to that of the conventional devices.

(Example 2) Polyimide varnish SE-4140 manufactured by Nissan Chemical Co., Ltd. was obtained. This was diluted to 2% with a dedicated solvent, and rubbed and glass substrates were bonded together in the same manner as in Example 1. Next, this bonded glass substrate was exposed to benzylamine gas for 24 hours. At this time, the same procedure as in Example 1 was carried out except that the benzylamine solution was kept at 90°C.

Next, in the same manner as in Example 1, the gap is filled with a nematic liquid crystal composition. A liquid crystal element is thus obtained. A voltage is applied to the ITO electrode, and it is observed while being sandwiched between polarizing plates.

[0028] The uniformity of the display characteristics of the liquid crystal elements was significantly superior to that of the prior art.

(Example 3) Polyacrylonitrile (PA
N) to be 0.7%, normal methyl
Add to pyrrolidone (NMP). Next, the whole is heated to about 80°C to dissolve the PAN. After this, it is immediately cooled. The fresh solution obtained in this way should be used. In the old case, solvation of NMP and PAN progresses.

As antistatic agents, Eletat S (trade name) was obtained from Hitoshisha Co., Ltd., Elegan-264P was obtained from Nihon Yushi Co., Ltd., and Dasper-125B was obtained from Miyoshi Oil Co., Ltd. These were dissolved in NMP in advance. The antistatic agent itself is added to the solution at a concentration of 0.0000
It was added so that it contained 3% and stirred well. Thus, three PAN solutions containing respective antistatic agents were obtained.

Each of these solutions is applied to glass substrates 1 and 2 having microfabricated ITO electrodes 3 and 4 as base materials.
was applied to the main surface of the film using a spinner and heated (heating temperature was approx.
(approximately 20 minutes at 50°C). The film thickness was about 10 nm. In this way, a substrate having three types of resin films is obtained.

The subsequent treatments were carried out for all three types of substrates. I did the normal rubbing process. However, it was necessary to devise ways to reduce electrostatic charging caused by friction of the fibers of the rubbing cloth used for rubbing. Next, a vertical alignment agent, ZLI-3334 (manufactured by Merck & Co., Ltd.), was applied to the rubbed resin surface using a spinner. This vertical alignment agent was diluted to about 0.01% and used. In this way, three types of organic resin films are obtained.

Glass substrates 1 and 2 of the same type are bonded to each other with a predetermined gap so that their main surfaces face each other so that the intersection angle of liquid crystal molecules is 250°. The sealing resin used was an ultraviolet curing resin. In addition, when irradiating ultraviolet light during curing, areas other than the seal were strictly masked. Next, it was exposed to cyclohexylamine gas at room temperature for 48 hours. In this case, the cyclohexylamine solution and the bonded glass substrate were allowed to coexist in a sealed container. That is, the bonded glass substrates were placed in a rich cyclohexylamine gas atmosphere.

[0034] A nematic liquid crystal composition is filled into the gap. A liquid crystal element is thus obtained. A voltage was applied to the ITO electrode, which was sandwiched between polarizing plates, and the uniformity of optical change of the liquid crystal element was evaluated. Uniformity was improved by about 30% compared to the conventional one. The best results were obtained using Eretat S as the antistatic agent.

Next, the glass substrates 1 and 2 are bonded together with a predetermined gap so that the principal surfaces of the three types of substrates face each other so that the rubbing directions are antiparallel to each other. As the sealing resin, an epoxy resin that can be cured at about 150° C. for 3 hours was used. Next, it was exposed to cyclohexylamine gas at room temperature for 48 hours. In this case, the cyclohexylamine solution and the bonded glass substrate were allowed to coexist in a sealed container. That is, the bonded glass substrates were placed in a rich cyclohexylamine gas atmosphere.

Next, the gap is filled with a ferroelectric liquid crystal composition. A liquid crystal element is thus obtained. A voltage is applied to the ITO electrode, and it is observed while being sandwiched between polarizing plates.

All initial orientations were uniform orientations. There were also very few zigzag defects. Conventionally, even if this state can be obtained, when a voltage is applied, the twisted orientation becomes dominant and the contrast is significantly reduced. However,
In this example, a stable bistable uniform orientation was obtained even when a voltage was applied. Naturally, the contrast has also been significantly improved compared to the previous model.

Regarding the bistable uniform orientation,
We were able to obtain sufficient reliability. This is something that could not have been expected in the past.

(Example 4) As antistatic agents, Eletat S (trade name) was obtained from Hitoshisha Co., Ltd., Elegan-264P was obtained from Nippon Oil & Fats Co., Ltd., and Dasper-125B was obtained from Miyoshi Oil Co., Ltd. As in Example 1, an NMP solution was prepared to contain about 0.7% of the polyparabanic acid resin. This solution must be used fresh. The antistatic agent itself was added to the solution so as to contain 0.00003%, and stirred well. Thus, three types of polyparabanic acid resin solutions containing respective antistatic agents were obtained.

[0040] If the amount of antistatic agent is 0.0001% or more, the results tend to be unfavorable.

Each of these solutions was applied to glass substrates 1 and 2 having microfabricated ITO electrodes 3 and 4 as base materials.
was applied to the main surface of the film using a spinner and heated (heating temperature was approx.
(approximately 20 minutes at 5°C). The film thickness was about 10 nm. Thus,
A substrate having three types of resin films is obtained.

The subsequent treatments were carried out for all three types of substrates. I did the normal rubbing process. However, it was necessary to devise ways to reduce electrostatic charging caused by friction of the fibers of the rubbing cloth used for rubbing. Next, a vertical alignment agent, ZLI-3334 (manufactured by Merck & Co., Ltd.), was applied to the rubbed resin surface using a spinner. This vertical alignment agent was diluted to about 0.01% and used. In this way, three types of organic resin films are obtained.

Glass substrates 1 and 2 of the same type are bonded to each other with a predetermined gap so that the main surfaces thereof face each other so that the intersection angle of liquid crystal molecules is 250°. The sealing resin used was an ultraviolet curing resin. In addition, when irradiating ultraviolet light during curing, areas other than the seal were strictly masked. Next, it was exposed to cyclohexylamine gas at room temperature for 48 hours. In this case, the cyclohexylamine solution and the bonded glass substrate were allowed to coexist in a sealed container. That is, the bonded glass substrates were placed in a rich cyclohexylamine gas atmosphere.

[0044] A nematic liquid crystal composition is filled into the gap. A liquid crystal element is thus obtained. A voltage was applied to the ITO electrode, which was sandwiched between polarizing plates to evaluate the uniformity of optical changes of the liquid crystal panel. Uniformity was improved by about 30% compared to the conventional one. The best results were obtained using Eretat S as the antistatic agent.

Next, the glass substrates 1 and 2 are bonded together with a predetermined gap so that the principal surfaces of the three types of substrates face each other so that the rubbing directions are antiparallel to each other. As the sealing resin, an epoxy resin that can be cured at about 150° C. for 3 hours was used. Next, it was exposed to cyclohexylamine gas at room temperature for 48 hours. In this case, the cyclohexylamine solution and the bonded glass substrate were allowed to coexist in a sealed container. That is, the bonded glass substrates were placed in a rich cyclohexylamine gas atmosphere.

Next, the gap is filled with a ferroelectric liquid crystal composition. A liquid crystal element is thus obtained. A voltage is applied to the ITO electrode, and it is observed while being sandwiched between polarizing plates.

All initial orientations were uniform orientations. There were also very few zigzag defects. Conventionally, even if this state can be obtained, when a voltage is applied, the twisted orientation becomes dominant and the contrast is significantly reduced. However,
In this example, a stable bistable uniform orientation was obtained even when a voltage was applied. Naturally, the contrast has also been significantly improved compared to the previous model.

Regarding the bistable uniform orientation,
We were able to obtain sufficient reliability. This is something that could not have been expected in the past.

[0049]

As described above, the present invention makes it possible to obtain an excellent liquid crystal element through appropriate processing, thereby greatly contributing to industry.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a liquid crystal element obtained by an example of the present invention.

[Explanation of symbols]

1, 2 First and second substrates 3, 4 Rectangular transparent conductive electrode 5 made of ITO film
, 6 organic resin film 7, 8 layer consisting of organic low molecules 9 liquid crystal layer 10, 11 liquid crystal alignment film

Claims (10)

[Claims] Claim 1: A liquid crystal alignment film provided in a liquid crystal element comprising a liquid crystal sealed between opposing electrode substrates, which comprises an organic resin film and an ultra-thin organic low molecule film on the electrode substrates. A liquid crystal alignment film characterized by being formed by laminating layers in this order. 2. A liquid crystal alignment film provided in a liquid crystal element formed by sealing a liquid crystal between opposing electrode substrates, wherein the liquid crystal alignment film adsorbs organic low molecules to the surface of an organic resin film or exists on the surface. 2. The method for producing a liquid crystal alignment film according to claim 1, wherein the functional group is reacted with an organic low molecule. 3. The liquid crystal alignment film according to claim 1, wherein the organic low molecule is an amine compound. 4. The liquid crystal alignment according to claim 1, wherein the organic resin film comprises a rubbed polyimide film, a rubbed polyamide film, a rubbed polyacrylonitrile film, or a rubbed polyparabanic acid resin film. film. 5. The liquid crystal alignment film according to claim 1, wherein the liquid crystal is a nematic liquid crystal or a ferroelectric liquid crystal. 6. A claim characterized in that the organic resin film is formed by forming a layer made of polyacrylonitrile containing an antistatic agent, further rubbing this layer, and further adsorbing a vertical alignment agent on the layer surface. 1. The liquid crystal alignment film according to 1. [Claim 7] A claim characterized in that the organic resin film is formed by forming a layer made of polyparabanic acid resin containing an antistatic agent, further rubbing this layer, and further adsorbing a vertical alignment agent on the layer surface. Item 1. Liquid crystal alignment film according to item 1. 8. The method for producing a liquid crystal aligning film according to claim 1, wherein the organic resin film is exposed to a gas of the organic low molecule in adsorbing or reacting the organic low molecule with the organic resin film. . 9. The liquid crystal alignment film according to claim 3, wherein the organic low molecule is a primary amine. 10. The liquid crystal alignment film according to claim 9, wherein the organic low molecule is benzylamine or cyclohexylamine.