JPH04141625A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain an oriented film which is formed not by a rubbing method and to obtain uniform liquid crystal orientation performance having almost no defect by setting the contact angle of liquid crystal on the oriented film to 10 - 20 deg. and performing orientation almost by the oriented film itself. CONSTITUTION:One electrode body 2a which is used for the liquid crystal element 1 consists of a glass substrate, a transparent electrode 5a formed on the glass substrate 4, and an oriented film 6 formed on the surface of the transparent electrode 5a and the other electrode body 2b consists of a glass substrate 4, an electrode 5b formed on the glass substrate 4, an electrode 5b formed on the glass substrate 4, and an oriented film 6 formed on the surface of the electrode 5b. Then the oriented films 6 uniform the molecule array of the liquid crystal 3 and has such surface property that the contact angle theta of the liquid crystal 3 is 10 - 20 deg., and nearly oriented thin films are used. Consequently, the oriented films 6 which are formed without rubbing are formed and the uniform orientation of the liquid crystal with almost no defect and a proper pretilt angle are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel liquid crystal element having a novel liquid crystal alignment film.

[Conventional technology]

In recent years, displays using liquid crystal elements have become widely used as display media for watches, televisions, and the like.

A schematic cross-sectional view of a liquid crystal element is shown in FIG. In the figure, (1) C is a liquid crystal element, (2a) and (2b) are electrode bodies, and (3) is a liquid crystal. The electrode bodies (2a) and (2b) include a glass substrate (4) and a transparent electrode (5a) formed on the glass substrate.
) or an electrode (5b). A surface-treated alignment film (6) is formed on the surface of the transparent electrode (5a) or electrode (5b) on the glass substrate (4) in order to make the molecular alignment of the liquid crystal uniform.

In conventional liquid crystal elements, the alignment film is made of SiO or Aυ
It is a thin film formed by a physical method such as an oblique vapor deposition method or a rubbing method, or a physicochemical method such as a method in which a polyimide resin is applied and then rubbed.

[Problem to be solved by the invention]

However, the alignment film formed by the cultivation method is
The formation method is very advantageous in giving the liquid crystal a predetermined pretilt angle, but on the other hand, since it is a vacuum evaporation method, the IC
It requires a high vacuum on the order of 1.44°F, and the substrate must be tilted, making it difficult to mass-produce.

In addition, the alignment film formed by the rubbing method tends to have reduced productivity due to dust and static electricity generated during rubbing (
However, it has the disadvantage that the quality is easily deteriorated.

Therefore, an alignment film formed without using such a technique is desired.

Therefore, the present inventors have previously proposed a new liquid crystal alignment film that does not require rubbing treatment using a Langmuir-Prodgett (LB) film (Japanese Patent Laid-Open No. 63-2313
(See Publication No. 1, etc.). However, it has been found that depending on the LB film material used, the liquid crystal may be aligned perpendicularly or completely parallel to the substrate, which may limit the practicality of the liquid crystal element.

The present invention has been made in order to solve the problems of the prior art, and has an alignment film formed without using a rubbing method, and exhibits a uniform liquid crystal alignment with almost no defects. The purpose is to provide an element.

[Means to solve the problem]

The present invention provides one electrode body consisting of a glass substrate, a transparent electrode formed on the glass substrate, and an alignment film formed on the surface of the transparent electrode; A liquid crystal element consisting of another electrode body consisting of an electrode and an alignment film formed on the surface of the electrode, and a liquid crystal disposed between the two electrode bodies, the liquid crystal element comprising: The present invention relates to a liquid crystal element having a contact angle of 10 to 20 degrees, and the alignment film itself being substantially aligned.

[Function and Examples]

One electrode body used in the liquid crystal element of the present invention consists of a glass substrate, a transparent electrode formed on the glass substrate, and an alignment film formed on the surface of the transparent electrode, and the other electrode body consists of a glass substrate , consisting of an electrode formed on the glass substrate and an alignment film formed on the surface of the electrode.

The transparent electrode used for one electrode body is ITO1S1
02 etc. As the electrode used for the other electrode body, the transparent electrode, a thin film transistor (TFT),
Examples include metals such as thin film diode (TFD) A.

The alignment film is for making the molecular alignment of the liquid crystal uniform, and in the present invention, a substantially oriented thin film having surface properties such that the contact angle of the liquid crystal is 10 to 20 degrees is used.

The substantially oriented thin film refers to, for example, an LB film obtained by the LB method or a stretched film obtained by axial stretching, in which material molecules are substantially oriented in one direction within the plane of the thin film.

When the contact angle between the oriented thin film and the liquid crystal is 10 to 20 degrees, when a liquid crystal element is fabricated with the configuration shown in Figure 1, the liquid crystal has a stable contact angle of greater than 0 degrees and less than 20 degrees. Has a pre-tilt angle.

On the other hand, if the contact angle is out of the above range, the liquid crystal will be 0.
This results in a pretilt angle close to 90 degrees or 90 degrees, which limits its practicality as a liquid crystal element.

The contact angle (θ) between the substantially oriented thin film and the liquid crystal is determined by the contact angle (θ) between the approximately oriented thin film and the liquid crystal when the oriented film is placed on the electrode body on which the oriented film is formed, with a diameter of about 1.5 m.
The measurement is carried out as shown in FIG. 2 by dropping a liquid crystal droplet of m in size. In the figure, (3) is a liquid crystal, (4) is a glass substrate,
(5a) is a transparent electrode, and (6) is an alignment film.

Furthermore, the alignment film is a monomolecular film obtained by spreading an amphiphilic polymer substance having a repeating unit represented by the general formula (1) on a water surface, and a transparent electrode formed on a glass substrate. After laminating one or more layers, preferably about 1 to 11 layers, on the surface of the electrode formed on the glass substrate or on the surface of the electrode formed on the glass substrate, the amphiphilic polymer substance is completely or partially formed by the general formula (If ): A thin film obtained by heat treatment to form a polyimide having a repeating unit represented by is preferred.

The amphiphilic polymer substance represented by the general formula (+) has a surface property determined by the properties of R3RR and R6 without any heat treatment;
) As the cyclization reaction to form a polyimide having a repeating unit represented by formula (I1) progresses, the surface properties of the polyimide represented by general formula (I1) become dominant.

Since the contact angle of the liquid crystal on the thin film is determined by the surface properties of the thin film, it is possible to manipulate the contact angle of the liquid crystal on the alignment film by changing the heat treatment temperature and heat treatment time.

The number average molecular weight of the amphipathic molecular substance is LB as described below.
From the point of view of obtaining a substantially oriented thin film using the method,
00,000, more preferably 2,000 to 30,000.

R1 in the general formula (I) is a tetravalent group having at least 2, preferably 5 to 20 carbon atoms, and may be an aromatic group or a cycloaliphatic group. Often, it may be a group in which an aromatic group and an aliphatic group are bonded, and furthermore, these groups may be combined with an aliphatic group having 1 to 30 carbon atoms, a cycloaliphatic group, or an aromatic group. It may be a group bonded to an aliphatic group, and these groups may be monovalent groups such as halogen atoms, nitro groups, amino groups, cyano groups, methoxy groups, acetoxy groups, or 〇--Co.

-Nl(CO-1-CO-1-S--CSS--NHC
It may also be a derivative group substituted with a group bonded to S-1-C8 or the like. Among these, groups characterized by benzenoid unsaturation having at least 6 carbon atoms are preferred from the viewpoint of heat resistance, chemical resistance, mechanical properties, and the like.

Benzenoid unsaturation as used herein is a term used in contrast to quinoid structure in relation to the structure of carbocyclic compounds, as shown in the following formula, and is a structure with the same shape as the carbocycle contained in ordinary aromatic compounds. means.

p-quinoid structure The four bonds of benzenoid unsaturated R1, that is, the positions of the bonds in the repeating unit represented by the general formula (Il) are not limited, but two of each of the four bonds are When present in two adjacent carbon atoms constituting R1, a film formed using an amphiphilic polymer substance (ampholytic polyimide precursor) having a repeating unit represented by general formula (1), etc. When converting into polyimide, 5
It is preferable because it forms a member ring and is easily imidized.

Specific examples of R1 as described above include, for example.

R2 in the general formula (1) is a divalent group containing at least two carbon atoms, and may be an aromatic group, an aliphatic group, or a cycloaliphatic group. It may be a group in which an aromatic group and an aliphatic group are bonded, and furthermore, these divalent groups may have 1 to 1 carbon atoms.
30 aliphatic groups, cycloaliphatic groups, or aromatic groups bonded to aliphatic groups; group, a monovalent group such as an acetoxy group, or the monovalent group -o--co.

NHCO-1-CO-1zu--C5S--NHCS-1
It may also be a group substituted with a group bonded to -CS- or the like.

Among these, groups characterized by benzenoid unsaturation having at least 6 carbon atoms are preferred from the viewpoint of heat resistance, chemical resistance, mechanical properties, and the like.

Preferred specific examples of R2 as described above include, for example, CH3U (R8 and R9 each represent an alkyl or aryl group having 1 to 30 carbon atoms).

RRR and R6 in the general formula (1) are respectively a nitrogen atom, a nitro group, an amino group,
Aliphatic, cycloaliphatic or aromatic (these may be combined with each other) carbon atoms having 1 to 30, preferably 1 to 22, optionally substituted with a cyano group, methoxy group, or acetoxy group. It is a monovalent hydrocarbon group or a hydrogen atom. In addition, in the general formula (1), RRR and R6 both represent the general formula (Il+): (wherein, RR
is a group introduced in order to impart hydrophobicity to the polyamic acid unit represented by , aliphatic, cycloaliphatic, or aromatic (these groups may be combined with each other) which may be substituted with a cyano group, a methoxy group, or an acetoxy group, and has 12 to 30 carbon atoms. Since it is preferably a group of 16 to 22, a stable condensed film is formed on the water surface, which is accumulated on the substrate by the LB method.

Specific examples of groups other than hydrogen atoms in R3456 RRR as described above include, for example, C1l 3 (
CH mountain shoulder - (CH3)2 CH (CH2 dimension, (all of the above values are 12-30, preferably 16-2
2) etc. Among these, C113 (
It is particularly desirable to use a straight chain alkyl group represented by CH2) L-4- from the viewpoint of performance and cost. Moreover, since hydrophobicity is dramatically improved by a fluorine atom compared to a hydrogen atom, one containing a fluorine atom is more preferable.

Specific examples of amphiphilic polymer substances having repeating units represented by the general formula (1) as described above include, for example, amphiphilic polymers having units such as (wherein RIO is CH3(C112)+7). Substances can be given.

Although there are no particular limitations on the method for producing the monomolecular film (LH film) of the amphiphilic polymer substance, a method that causes flow orientation during accumulation is desirable, and a vertical immersion method is one of the preferred embodiments.

At this time, known L such as long chain fatty acids and long chain alcohols
B film material and the present inventors previously disclosed JP-A-63-21872
The polymer LB film materials proposed in Publication No. 7 may be used in combination.

It is also a desirable embodiment of the present invention to perform surface treatment on the glass substrate on which the electrodes are formed before depositing the LB film.

An amphiphilic polymeric substance having a repeating unit represented by the above general formula (+) is cyclized and completely or partially represented by the general formula (
The heat treatment temperature for forming the polyimide having the repeating unit represented by 11) is usually above the temperature used in the liquid crystal element assembly process after forming the alignment film, but below the temperature at which the alignment film material decomposes, and is 150 to Preferably 450°C, 1
More preferably, the temperature is 50 to 250°C.

There is no particular limitation on the liquid crystal or liquid crystal element format that can be used in the present invention, and the liquid crystal element of the present invention includes, for example, a TN type liquid crystal element using nematic liquid crystal, a guest-host type liquid crystal element, an STN type liquid crystal element, and a ferroelectric liquid crystal element. It is manufactured and used as a liquid crystal element.

Next, the liquid crystal element of the present invention will be described in more detail based on Examples.

Example 1 ITO was vacuum deposited to a thickness of 200 nm using a mask with a pattern formed on one side of a glass substrate. On the other hand, a polyimide precursor (number average molecular weight +0000) having a unit represented by the formula obtained by reacting the acid chloride of pyromellitic acid distearyl ester and paraphenylene diamine was added to the above-mentioned ITO-deposited glass. Eleven layers were accumulated on the substrate by the LB method. Thereafter, the substrate was further heat-treated at 180° C. for 1 hour. Through this heat treatment, the polyimide precursor becomes a polyimide having units represented by the formula, and the LB film has the following:
It has very good chemical resistance and heat resistance.

Note that the imidization rate in this case was 40%.

Two identical glass substrates (electrode bodies) on which alignment films have been formed by processing as described above are prepared, and cells are arranged so that the pulling directions of the two substrates when forming the LB film are perpendicular to each other. Acid anhydride-curing epoxy resin in which plastic beads with a diameter of 8 μm are dispersed is applied as a sealing resin to the surface of one of the substrates on which the transparent electrode layer is formed, leaving a 5 mm length in the center of one side. After printing with a width of 1 mm around the entire circumference, pressurize with transparent electrodes facing each other and heat at 140℃.
The adhesive was cured and bonded by heating for 3 hours.

After adhesion, a nematic liquid crystal (manufactured by Merck & Co., trade name 2LI 2701: chiral agent C-) is inserted from the opening under reduced pressure.
15 (containing 0.5% by weight) was injected. After the injection, the opening was fixed with a commercially available acid anhydride-curable epoxy resin to seal the liquid crystal and complete a TN-type liquid crystal element. By heating the completed liquid crystal cell to 100° C. and then gradually cooling it for initial alignment, a cell with a uniform, defect-free and good alignment state was obtained.

The contact angle of the nematic liquid crystal used in this example on the alignment film obtained in this example was 16.7 degrees.

In addition, a liquid crystal element (anti-para type liquid crystal element) manufactured in the same manner was used, except that the cell was configured so that the pulling direction of the substrates was antiparallel when forming the LB film on the two substrates. When the pretilt angle was measured using the crystal rotation method, the result was 6.1 degrees.

Example 2 A TN-type liquid crystal device and an anti-para-type liquid crystal device were produced in the same manner as in Example 1, except that the glass substrate on which the LB film was formed was heat-treated at 200° C. for 1 hour.

Note that the imidization rate in this case was 40%.

The contact angle of the nematic liquid crystal used in this example on the alignment film obtained in this example was 13.0 degrees.

Furthermore, when the pretilt angle of the liquid crystal was measured using the crystal rotation method, the result was 0.5 degrees.

Example 3 ITO was vacuum deposited to a thickness of 200 nm using a mask with a pattern formed on one side of a glass substrate.

On the other hand, a polyimide precursor (with a number average molecular weight of 10,000+) having the formula % formula %) obtained by reacting the acid chloride of pyromellitic acid distearyl ester with diaminoanthraquinone (number average molecular weight 10,000+) was used on the glass substrate on which the above-mentioned ITO was vapor-deposited. By the Langmuir-Prodgett method (LB method),
11 layers were accumulated. Thereafter, the substrate was further heated to 180°C.
It was heat-treated for 1 hour. With this heat treatment, the polyimide precursor has the formula:

The LB film is a polyimide having units shown as
It has very good chemical resistance and heat resistance.

The imidization rate at this time was 60%.

Two of the same treated glass substrates described above were prepared, and a cell was constructed so that the pulling directions of the substrates during LH film formation on the two substrates were perpendicular to each other, and the surface of one substrate on which the transparent electrode layer was formed. As a sealing resin, an acid anhydride-curing epoxy resin in which plastic beads with a diameter of 8 μm are dispersed is applied around the entire circumference, leaving a 5 mm length in the center of one side. After printing with a width of mm, pressure was applied with the transparent electrodes facing each other, and the adhesive was cured by heating at 140° C. for 3 hours. After adhesion, a manetic liquid crystal (manufactured by Merck & Co., Ltd.,
Product name 2LI 1565 Chiral agent C-15 05
% by weight) was injected. After injection, the opening is fixed with a commercially available acid anhydride-curing epoxy resin, the liquid crystal is sealed, and the TN
A type of liquid crystal element was completed. Once the completed liquid crystal cell is 100
By heating to ℃ and then gradually cooling for initial orientation, cells with uniform, defect-free, and good orientation were obtained.

The contact angle of the nematic liquid crystal used in this example on the alignment film obtained in this example was 150 degrees. Also, 2
Using a liquid crystal element (anti-para type liquid crystal element) obtained in the same manner except for configuring the cell so that the direction in which the substrate is pulled up during formation of the LB film on the two substrates is an antiparallel direction, the pretilt angle of the liquid crystal is When measured using the crystal rotation method, the result was 1.0 degrees.

Comparative Example I A TN-type liquid crystal element was produced in the same manner as in Example 1, except that the glass substrate on which the LB film was formed was heat-treated at 150° C. for 1 hour.

In the obtained liquid crystal element, the liquid crystals were aligned almost perpendicularly to the substrate, and did not exhibit optical rotation.

The contact angle of the nematic liquid crystal used in this comparative example on the alignment film obtained in this comparative example was 29.0 degrees.

Comparative Example 2 A TN-type liquid crystal device and an anti-para-type liquid crystal device were produced in the same manner as in Example 1, except that the glass substrate on which the LB film was formed was heat-treated at 300° C. for 1 hour.

When the obtained liquid crystal element was subjected to static drive, a reverse tilt defect occurred, and the display quality was clearly degraded compared to Examples 1 and 2.

The nematic liquid crystal used in this comparative example on the alignment film obtained in this comparative example was completely (wet),
The contact angle was 0 degrees. Furthermore, when the pretilt angle of the liquid crystal was measured using the crystal rotation method, the result was completely 0 degrees and 5+ degrees.

〔Effect of the invention〕

As explained above, the liquid crystal element of the present invention has an alignment film formed without performing a rubbing process, and can achieve uniform alignment of the liquid crystal with almost no defects and an appropriate pretilt angle. .

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a liquid crystal element, and Fig. 2 is an explanatory diagram of a method for measuring the contact angle on an alignment film of liquid crystal. (Symbols in drawings) (1): Liquid crystal element (2a), ( 2b): Electrode body (3): Liquid crystal (4), glass substrate (5a): Transparent electrode (5b), electrode (6): alignment film

Claims (1)

[Claims] 1. One electrode body consisting of a glass substrate, a transparent electrode formed on the glass substrate, and an alignment film formed on the surface of the transparent electrode, a glass substrate, and an electrode body formed on the glass substrate. A liquid crystal element comprising a second electrode body comprising an electrode and an alignment film formed on the surface of the electrode, and a liquid crystal disposed between the two electrode bodies, the liquid crystal element comprising: A liquid crystal element having a contact angle of 10 to 20 degrees on the liquid crystal element, and the alignment film itself being substantially aligned. 2. The liquid crystal element according to claim 1, wherein the alignment film is made of an organic material containing an alkyl group having 12 or more carbon atoms. 3 The alignment film has the general formula (I): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (wherein R^1 is 4 having at least 2 carbon atoms)
a valent group, R^2 having at least 2 carbon atoms;
The valent groups R^3, R^4, R^5 and R^6 are each an aliphatic group which may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group, an acetoxy group,
Cycloaliphatic or aromatic (these may be combined with each other) monovalent group having 1 to 30 carbon atoms or hydrogen atom, R^3, R^4, R^5 and R^6 At least one of them is an aliphatic, cycloaliphatic, or aromatic group that may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group, or an acetoxy group (even if these are combined with each other) good) with 12 to 30 carbon atoms
Forming a monomolecular film obtained by spreading an amphiphilic polymeric substance having a repeating unit represented by (a valent group) on a water surface on the surface of a transparent electrode formed on a glass substrate or on a glass substrate. After one or more layers are laminated on the surface of the electrode, the amphiphilic polymer substance is completely or partially formed into the general formula (II): ▲Mathematical formula, chemical formula, table, etc.▼(II) (Formula 2. The liquid crystal element according to claim 1, wherein the thin film is a thin film obtained by heat treatment to obtain a polyimide having a repeating unit represented by R^1 and R^2 respectively as defined above.