JPH05158043A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain uniform, flawless and good orientation property by providing a liq. crystal oriented film consisting of a Langmuir-Blodgett's film in >=1 layer on the thin film of a specified org. high molecular substance. CONSTITUTION:The thin film consisting of an org. high molecular substance soluble in gamma-butylolactone by >=10wt.%, having a repeating unit shown by the formula and having 200Angstrom to 10mum thickness is formed. A liq. crystal oriented film consisting of the Langmuir-Blodgett' s film in >=1 layer is furnished thereon. In the formula, R<1> is a tetravalent group having at least two carbon atoms, and R<2> is a bivalent group having at least two carbon atoms. Consequently, defective orientation is not caused even when a substrate having a step of several thousand Angstrom to several mum such as a substrate on which a thin-film transistor of amorphous Si is formed, the substrate layer is easily formed, and an oriented film having uniform, flawless and good orientation property is formed without applying post treatment such as lapping.

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 having a novel underlayer and a liquid crystal alignment film composed of a Langmuir-Brogliet film.

[0002]

2. Description of the Related Art Flat displays using liquid crystals such as watches and televisions have come into wide use.

Liquid crystal display devices used in such flat displays have conventionally been rubbed in a fixed direction with a cloth or the like after applying an oblique vapor deposition method using SiO ₂ , Au or the like or applying a polyimide polymer resin on a substrate. A liquid crystal display element having an alignment film formed by the method (rubbing method) is used.

When the alignment film is formed by the oblique vapor deposition method, an alignment film which is very advantageous for giving a predetermined pretilt angle to the liquid crystal can be obtained.
^{Since it} requires a high vacuum of about ^-5 torr and the substrate must be tilted, it has the drawback of poor mass productivity.

On the other hand, the rubbing method has a drawback that dust and static electricity generated during rubbing have a bad influence.

[0006]

In order to solve such a problem of the prior art, by using a Langmuir-Brogget film (hereinafter, also referred to as an LB film) as a liquid crystal alignment film, it is uniform and has very few defects. Moreover, it has been proposed to obtain a liquid crystal alignment film having a good alignment property without rubbing, but in this method, the productivity of the LB film is lower than that of other thin film forming methods. ,
In addition, when the number of laminated layers of LB films having the ability to align liquid crystals is small, it is several thousand Å to several μ as on a substrate on which an amorphous Si thin film transistor (TFT) is formed.
There is a problem that a defective alignment is likely to occur on a substrate having a step of m.

[0007]

The present invention has been made in order to solve the problem of the case where the LB film is used, and is soluble in γ-butyrolactone in an amount of 10% (% by weight, hereinafter the same) or more. General formula (1):

[0008]

[Chemical 4]

An organic polymer substance having a repeating unit represented by the formula: wherein R ¹ is a tetravalent group having at least 2 carbon atoms and R ² is a divalent group having at least 2 carbon atoms. On a thin film with a thickness of 200 Å to 10 μm
The present invention relates to a liquid crystal device characterized in that a liquid crystal alignment film composed of a Langmuir-Brogliet film obtained by laminating one or more layers is provided.

[0010]

EXAMPLE In the present invention, 10 is used for γ-butyrolactone.
% Or more, preferably 20% or more of the general formula (1):

[0011]

[Chemical 5]

An organic polymer substance having a repeating unit represented by the following is used.

If the organic polymer is less than 10% soluble in γ-butyrolactone, the film forming property becomes poor and it becomes difficult to obtain a uniform film.

In the above general formula (1), R ¹ is a tetravalent group having at least 2, preferably 5 to 20 carbon atoms. When the number of carbon atoms is less than 2, the heat resistance of the obtained organic polymer substance becomes poor.

Specific examples of R ¹ include, for example,

[0016]

[Chemical 6]

And the like.

R ² is at least 2, preferably 5
A divalent group having 20 carbon atoms. When the number of carbon atoms is less than 2, the heat resistance of the obtained organic polymer substance becomes poor.

Specific examples of R ² include, for example,

[0020]

[Chemical 7]

And the like.

Specific examples of the repeating unit include, for example,

[0023]

[Chemical 8]

And the like.

Intrinsic viscosity of the organic polymer (η _inh =
ln (η _rel ) / C, C = 0.5 g / dl, 30 ° C. in DMF)
Is preferably 0.05 dl / g or more, 0.05 to 5 dl / g
Is more preferable. If the intrinsic viscosity is less than 0.05 dl / g, the heat resistance tends to decrease, and if it exceeds 5 dl / g, the solubility in γ-butyrolactone tends to decrease.

By using the organic polymer substance, the smoothness of the surface of the substrate is improved, and the film forming property of the LB film is significantly improved.

In the present invention, a thin film made of the organic polymer material is provided on a transparent electrode layer having a step of several thousand Å to several μm provided on a glass substrate or the like.

The thickness of the thin film is usually 200Å-10 μm.
m, preferably 500 Å to 1 μm. If the film thickness is less than 200 Å, smoothing of the surface of the substrate becomes insufficient,
If it exceeds 10 μm, a sufficient voltage cannot be applied to the liquid crystal when the liquid crystal element is assembled.

As a method for forming the thin film, the organic polymer substance is mixed at an appropriate concentration such that the concentration is 10% or more.
Examples of the method include a method in which it is dissolved in butyrolactone and then applied on a transparent electrode, but the method is not limited to these methods.

Examples of the coating method include spin coating method, printing method, dipping method, roll coater method and the like, and there is no particular limitation, but spin coating method and printing method are thin films having a uniform film thickness. From the viewpoint of forming Further, as a solvent used at the time of coating, N-
A solvent such as methyl-2-pyrrolidone, N, N'-dimethylacetamide, N, N'-dimethylformamide, dimethylsulfoxide may be used.

In the present invention, a liquid crystal alignment film composed of an LB film obtained by laminating one or more layers is provided on the thin film.

The LB film has, for example, the general formula (2):

[0033]

[Chemical 9]

A film formed from an amphipathic polymer having a repeating unit represented by

The amphiphilic polymer substance can be formed into a monomolecular film by spreading it on the water surface, and this can be laminated as a monomolecular film, and the repeating unit represented by the general formula (2) can be used. The amphiphilic polymer substance having a general formula (4):

[0036]

[Chemical 10]

A polyimide having a repeating unit represented by

In the above general formula (2), R ³ is a tetravalent group containing at least 2, preferably 5 to 20 carbon atoms, which may be an aromatic group or a cycloaliphatic group. It may be a group, may be a group in which an aromatic group and an aliphatic group are bonded, and further, these groups have 1 to 30 carbon atoms.
A group substituted with an aliphatic group, a cycloaliphatic group or a group in which an aromatic group and an aliphatic group are bonded, and further, those groups are a halogen atom, a nitro group, an amino group or a cyano group. , A methoxy group, an acetoxy group, and the like, or a monovalent group such as -O-, -COO-, -NHCO-, -CO-,
It may be a group which is substituted with a bonded group such as -S-, -CSS-, -NHCS-, and -CS- to become a derivative.
Of these, R ³ is preferably a group characterized by benzenoid unsaturation having at least 6 carbon atoms from the viewpoint of heat resistance, chemical resistance, mechanical properties and the like.

The benzenoid unsaturation is a term used in comparison with a quinoid structure for the structure of a carbocyclic compound, and refers to a structure having the same shape as the carbocycle contained in a common aromatic compound.

[0040]

[Chemical 11]

Specific examples of R ³ as described above include, for example:

[0042]

[Chemical 12]

And the like.

Four bonds of R ³ , that is, the general formula (2)
In the repeating unit represented by

[0045]

[Chemical 13]

There is no limitation on the position of the hand that is joined by
Of the individual bonds, the divalent bond and the monovalent bond are R
^When it is present in two adjacent carbon atoms constituting ³ , it is easy to form a 5-membered ring and imidized when a film formed using the amphiphilic polymer substance (polyimide precursor) is polyimidized. It is preferable because it becomes easy.

In the general formula (2), R ⁴ is at least 2
A divalent group containing 1 carbon atom, which may be an aromatic group, an aliphatic group, a cycloaliphatic group, or an aromatic group. It may be a group bonded to an aliphatic group, and these divalent groups have 1 to 1 carbon atoms.
30 aliphatic groups, cycloaliphatic groups or groups substituted with a group in which an aromatic group and an aliphatic group are bonded, or a group in which these groups are a halogen atom, a nitro group, an amino group or a cyano group , Monovalent groups such as methoxy group and acetoxy group and these monovalent groups are -O-, -COO-, -NHCO-, -C.
It may be a group substituted with a group bonded to O-, -S-, -CSS-, -NHCS-, -CS- and the like. Of these, R ⁴ is preferably a group characterized by benzenoid unsaturation having at least 6 carbon atoms from the viewpoint of heat resistance, chemical resistance, mechanical properties, and the like.

Specific preferred examples of R ⁴ as described above include, for example,

[0049]

[Chemical 14]

(R ¹⁰ and R ¹¹ are both C 1
~ 30 alkyl or aryl groups)) and the like.

In the general formula (2), R ⁵ , R ⁶ , R ⁷ and R ⁸ are all 1 to 30 carbon atoms, preferably 1 to 22 carbon atoms.
Valent aliphatic group, 1 to 3 to 30 carbon atoms, preferably 3 to 22 carbon atoms
Valent cycloaliphatic group having 6 to 30 carbon atoms, preferably 6 to 22 carbon atoms
A monovalent aromatic group, a monovalent group formed by combining these groups with each other, those groups substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group, Is a group or a hydrogen atom which is a derivative of the group. However, at least one of R ⁵ , R ⁶ , R ⁷ , and R ⁸ is represented by the general formula (5):

[0052]

[Chemical 15]

Hydrophobicity is imparted to the polyamic acid unit represented by the formula (wherein R ³ and R ⁴ are the same as above) to form a stable condensed film on the water surface, and the polyamic acid unit is formed on a glass substrate having a thin film electrode. 12-30 carbon atoms, preferably 16 carbon atoms, to accumulate
It is preferable that the above groups are ˜22.

Specific examples of the groups other than the hydrogen atom of R ⁵ , R ⁶ , R ⁷ and R ⁸ as described above include, for example,

[0055]

[Chemical 16]

(All of the above n are 12 to 30, preferably
16-22) and so on. Of these, in order to achieve the object of the present invention, it is preferable to use a straight chain alkyl group represented by CH ₃ (CH ₂ ) _n-1- , in terms of performance and cost. In addition, among the halogen atom, nitro group, amino group, cyano group, methoxy group, acetoxy group, etc., since the hydrophobic property is dramatically improved by the fluorine atom as compared with the hydrogen atom, it is necessary to use the one containing the fluorine atom. Is preferred.

Specific examples of the repeating unit represented by the general formula (2) include, for example,

[0058]

[Chemical 17]

And the like.

In the case where the amphiphilic polymer substance has a repeating unit represented by the above general formula (2), the number average molecular weight is 2000 to 300,000, more preferably 2000.
It is preferably ˜30,000. The number average molecular weight is 20
If the value is out of the range of 00 to 300,000, there is a tendency that the strength when the LB film is formed is too low, or that the viscosity is too high and the LB film is not successfully produced.

In the present invention, the liquid crystal alignment film formed of the amphiphilic polymer substance is provided on the thin film formed of the organic polymer substance composed of the repeating unit represented by the general formula (1). It is preferable from the viewpoint of eliminating the liquid crystal alignment defect in the step portion on the substrate on which the electrode layer is formed.

Further, the more similar the skeleton of the amphiphilic polymer substance forming the LB film and the skeleton of the amphiphilic polymer substance forming the LB film, the better the adhesion and the LB having the preferable properties as the alignment film. The film is easily formed.

The amphipathic polymer substance may be a known Langmuir-type long-chain fatty acid or long-chain alcohol.
Blodgett film material may be mixed.

The number of laminated LB films is 1 or more, preferably 1 to 3.

Examples of the method for laminating the LB film include a vertical dipping method (LB method), a horizontal attachment method, a rotating cylinder method and the like. Among these, the vertical dipping method that causes the flow orientation of the monomolecular film during lamination is particularly preferable.

After the LB film is laminated, usually, when a polymer substance having a repeating unit represented by the general formula (2) is used, the orientation of the polymer substance is increased in order to cause a cyclization reaction. After film formation, heat treatment at a temperature higher than that required in the liquid crystal element assembly process and lower than the temperature at which the alignment film material decomposes, specifically 150 to 450 ° C, preferably 150 to 2
Heat treatment is performed at a temperature of 50 ° C. for 10 minutes to 3 hours.

The liquid crystal alignment film thus formed is
It has the ability to control the orientation of liquid crystals to the same extent as a conventional treatment layer (orientation film) formed by physical or physicochemical treatment.

In the liquid crystal element of the present invention, usually, a sealing resin is printed on the surface of the substrate on which the alignment film is formed, on which the transparent electrode layer is formed, and then another film is formed. The substrates are stacked so that the pulling directions of the substrates at the time of forming the LB film are perpendicular to each other, and the substrates are pressed and heated to be bonded together.
It can be obtained by injecting and sealing liquid crystal.

Since the liquid crystal element of the present invention uses the LB film as the alignment film as described above, the alignment film has a uniform, defect-free and good alignment property without being subjected to a treatment such as rubbing. In addition, the substrate on which the LB film having the ability to align the liquid crystal is laminated is, for example, several thousand Å like a glass substrate on which a thin film transistor (TFT) of amorphous Si is formed.
Even if it has a step of several μm, a thin film made of a polymer substance having the repeating unit represented by the general formula (1) is provided as an underlayer, so that the alignment failure at the step is caused. Does not occur. In addition, γ as the underlayer
-By using a substance represented by the general formula (1) which is soluble in butyrolactone in an amount of 10% or more, an alignment film having good performance is formed even when the number of laminated layers is 3 or less.
The low productivity when the film is used as a liquid crystal alignment film is improved.

Next, the liquid crystal element of the present invention will be described in detail with reference to Examples, but the present invention is not limited to such Examples.

Example 1 On a glass substrate on which an amorphous Si TFT having a step of about 1 μm was formed and on a glass substrate on which ITO and a black matrix were formed, the formula:

[0072]

[Chemical 18]

A 10% γ-butyrolactone solution of polyimide having an intrinsic viscosity η _inh = 0.7 dl / g consisting of repeating units represented by
The polyimide thin film was formed by performing a heat treatment at 1 ° C. for 1 hour.

Then, a formula obtained by reacting acid chloride of pyromellitic acid distearyl ester with para-phenylenediamine on the polyimide thin films on the two types of substrates:

[0075]

[Chemical 19]

Molecular weight consisting of repeating units represented by
Three thousand layers of 4000 polyimide precursors were accumulated by the Langmuir-Bloget method (LB method) and heat-treated at 200 ° C. for 1 hour. By this heat treatment, the polyimide precursor becomes 50
Formula as a percentage:

[0077]

[Chemical 20]

By becoming a polyimide like the repeating unit represented by, the LB film has good chemical resistance that it is not affected by a substance having a strong polarity such as liquid crystal, and heat resistance of 200 ° C.

Next, the above-mentioned two types of substrates were prepared, and an acid anhydride-curable epoxy resin in which plastic beads having a diameter of 5 μm were dispersed was used as a sealing resin on the surface of one substrate on which the transparent electrode layer was formed. Only the sides are printed with a width of 1 mm on the entire circumference while leaving a length of 5 mm in the center of the side, and transparent electrodes are placed so that the pulling directions of the substrates when forming the LB film of two substrates are perpendicular to each other. While facing ^each other, the pressure was applied at a pressure of 1 kg / cm ² , and the mixture was heated and cured at 140 ° C. for 3 hours to be cured and adhered to form a cell having a gap of 5 μm between the two substrates having the LB film formed thereon. After the adhesion, nematic liquid crystal (manufactured by Merck & Co., trade name ZLI1565) was injected from the opening under reduced pressure. After the injection, the opening was fixed with a commercially available acid anhydride-curable epoxy resin and the liquid crystal was sealed to complete a TN type liquid crystal cell. By heating the completed liquid crystal cell once to 100 ° C. and then gradually cooling it for initial alignment, a cell having a uniform and defect-free alignment state was obtained over the entire surface including the stepped portion of the substrate.

[0080]

The liquid crystal element of the present invention has a thickness of several thousand Å like a substrate on which an amorphous Si TFT is formed.
Even when a substrate having a step of several μm is used, since the liquid crystal alignment film is provided after the underlayer is provided, no alignment failure occurs. Further, since the polyimide that is easily dissolved in γ-butyrolactone is used as the underlayer, the formation of the underlayer is easy,
Its characteristics are also good. Furthermore, since the LB film is used as the alignment film, it is possible to form a uniform alignment film having no defects and good alignment properties without performing post-treatment such as rubbing.

Claims (3)

[Claims] 1. A general formula (1) soluble in 10% by weight or more in γ-butyrolactone: (Wherein R ¹ is a tetravalent group having at least 2 carbon atoms and R ² is a divalent group having at least 2 carbon atoms) and is composed of an organic polymer substance having a repeating unit. A liquid crystal device comprising a thin film having a thickness of 200 Å to 10 μm and a liquid crystal alignment film made of a Langmuir-Brogliet film obtained by laminating one or more layers. 2. The Langmuir-Broggett membrane comprises:
General formula (2): (In the formula, R ³ is a tetravalent group having at least 2 carbon atoms, R ⁴ is a divalent group having at least 2 carbon atoms, and R ⁵ , R ⁶ , R ⁷ and R ⁸ are carbon atoms. A monovalent aliphatic group having 1 to 30 carbon atoms, a monovalent cycloaliphatic group having 3 to 30 carbon atoms, or a monovalent aromatic group having 6 to 30 carbon atoms (these may be combined with each other. A halogen atom, a nitro group, an amino group, a cyano group, a methoxy group, an acetoxy group) or a hydrogen atom, and R ⁵ , R ⁶ ,
At least one of R ⁷ and R ⁸ has 12 to 12 carbon atoms.
30 monovalent aliphatic groups, C 12-30 monovalent cycloaliphatic groups or C 12-30 monovalent aromatic groups (which may be combined with each other, such as a halogen atom and a nitro group). Group, an amino group, a cyano group, a methoxy group, and an acetoxy group)), which is a film made of an amphiphilic polymer substance having a repeating unit represented by the formula). 3. The repeating unit represented by the general formula (1) is represented by the general formula (3): The liquid crystal element according to claim 1, which is a repeating unit represented by the formula (wherein R ² is the same as above).