JPH05150247A - Liquid crystal oriented film - Google Patents

Abstract

PURPOSE:To facilitate the impartation of a pretilt angle and to suppress the generation of reverse tilts and reverse twists when a TN type liquid crystal element is formed by using a specific amphiphatic high-polymer material. CONSTITUTION:The monomolecular films obtd. by developing the amphiphatic high-polymer material having the repeating unit expressed by formula on a water surface are laminated in >=1 layers on a substrate formed with at least an electrode layer and thereafter the films are subjected to such a heat treatment that the amphiphatic high-polymer material expressed by the formula induces a complete or partial ring closure reaction. In the formula, R is a quadrivalent group having at least 2 C; R<2> is a bivalent group having at least 2 C; R<3> to R<6> are 1 to 30C univalent group, of aliphat. group, or hydrogen atom. At least one among R<3> to R<6> are 12 to 30C univalent group, of aliphat. group. At least one of R<1> and R<2> have >=1 pieces of 2 to 8C long-chain alkyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal alignment film for aligning liquid crystals, and more specifically, it is easy to provide a pretilt angle, and a reverse tilt or reverse tilt can be obtained when a TN type liquid crystal element is manufactured. The present invention relates to a liquid crystal alignment film capable of suppressing the generation of twist.

[0002]

2. Description of the Related Art Flat displays using liquid crystals have been widely used in clocks, televisions, etc.
A liquid crystal is formed using an alignment film formed by an oblique vapor deposition method in which SiO ₂ , Au, etc. are obliquely deposited, or a rubbing method in which a polyimide-based polymer resin is applied on a substrate and then rubbed in a certain direction with a cloth or the like. To obtain a liquid crystal alignment film. However, the liquid crystal alignment film formed by the oblique evaporation method is very advantageous for giving a predetermined pretilt angle to the liquid crystal, but on the other hand, since it is a vacuum evaporation method, a high vacuum of about 10 ⁻⁵ torr is required. However, it has a drawback that it is poor in mass productivity because the substrate must be inclined. Also,
The liquid crystal alignment film formed by the rubbing method is likely to reduce productivity due to dust and static electricity generated during rubbing,
It has the drawback of adversely affecting quality.

In order to solve the above problems, the present inventors have proposed a polyimide LB film as a new liquid crystal alignment film which is uniform, has very few defects, and has a good alignment property without rubbing. (JP-A-63-23131, JP-A-3-53223). However, it is difficult for the LB film to give a predetermined pretilt angle, and there is a problem that a reverse tilt or a reverse twist defect occurs when a TN type liquid crystal element is manufactured using the LB film as a liquid crystal alignment film.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a liquid crystal alignment film capable of easily imparting a predetermined pretilt angle to liquid crystal and suppressing the occurrence of reverse tilt and reverse twist in the case of a TN liquid crystal element. To do.

[0005]

The present invention provides the following structural formula (1):

[0006]

[Chemical 4]

[Wherein R ¹ is a tetravalent group having at least 2 carbon atoms, R ² is a divalent group having at least 2 carbon atoms, R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms (these groups are halogen atoms, nitro groups, amino groups, It may be substituted with a cyano group, a methoxy group, an acetoxy group) or a hydrogen atom. Also, at least R ³ ,
One of R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other).
Is a monovalent group having 12 to 30 carbon atoms (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). Also,
One of R ¹ and R ² has one or more long-chain alkyl groups having 2 to 8 carbon atoms. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( A liquid crystal alignment film obtained by subjecting the amphipathic polymer represented by 1) to a heat treatment in which a ring-closing reaction occurs completely or partially,

The present invention also provides the following structural formula (2)

[0009]

[Chemical 5]

[Wherein R ¹ is a tetravalent group having at least 2 carbon atoms, R ² is a divalent group having at least 2 carbon atoms, R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms (these groups are halogen atoms, nitro groups, amino groups, It may be substituted with a cyano group, a methoxy group, an acetoxy group) or a hydrogen atom. Also, at least R ³ ,
One of R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other).
Is a monovalent group having 12 to 30 carbon atoms (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). m is 1
~ 7. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( A liquid crystal alignment film obtained by subjecting the amphipathic polymer represented by 2) to a heat treatment in which a ring closure reaction completely or partially occurs,

Furthermore, the present invention provides the following structural formula (3):

[0012]

[Chemical 6]

[Wherein R ¹ is a tetravalent group having at least 2 carbon atoms, R ² is a divalent group having at least 2 carbon atoms, R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms (these groups are halogen atoms, nitro groups, amino groups, It may be substituted with a cyano group, a methoxy group, an acetoxy group) or a hydrogen atom. Also, at least R ³ ,
One of R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other).
Is a monovalent group having 12 to 30 carbon atoms (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). Also,
One of R ¹ and R ² has one or more long-chain alkyl groups having 2 to 8 carbon atoms. m is 1-7. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( The content of the liquid crystal alignment film obtained by subjecting the amphipathic polymer represented by 3) to a heat treatment in which a ring-closing reaction completely or partially occurs.

The number average molecular weight of the amphipathic polymer represented by the structural formulas (1), (2) and (3) is 2000 to 300.
About 000 is preferable. If the number average molecular weight is out of the above range, the monomolecular film may have too low strength, or the viscosity may be too high, which may hinder the production of the monomolecular film.

The amphipathic polymer represented by the structural formulas (1), (2), and (3) can be easily converted into a single molecule by spreading on the water surface by, for example, the Langmuir-Blodgett method (LB method). A film is formed, and one or more layers are laminated on a substrate on which at least an electrode layer is formed, and then the film is completely or partially closed to form a polyimide. The polyimidization can be performed chemically or thermally, but in the case of partial polyimidation, the polyimidization is thermally performed because it is easy to control the number of hydrophobic groups per repeating unit of the polyimide precursor. Is desirable.

The heat treatment temperature is higher than the temperature received in the liquid crystal element assembling step after the alignment film is formed and lower than the temperature at which the alignment film material is decomposed, and is usually preferably 15
It is in the range of 0 to 450 ° C, and more preferably 150 to 250 ° C.

[0017]

The film (LB film) obtained by laminating at least one monomolecular film obtained by spreading the polyimide precursor on the water surface on a substrate having an electrode layer is uniaxially oriented. It is an oriented film, and a liquid crystal substance can be favorably oriented on the film. The pretilt angle of the liquid crystal is determined by the excluded volume effect of long-chain alkyl groups existing in the LB film material [“Japanese Journal of Applied Physics”, 29 (1
990), 2045], but R ³ , R ⁴ , R ⁵ and R in the structural formulas (1), (2) and (3).
^{The amount of 6} is different depending on the degree of imidization of the polyimide precursor, and it is very difficult to control the amount.
In addition, the number of carbon atoms required to be amphiphilic is 12 to 3
Since a very long long-chain alkyl group of 0 is bent in various directions, the pretilt angle of the liquid crystal generated by the excluded volume effect of R ³ , R ⁴ , R ⁵ , and R ⁶ is very unstable. . This problem is solved by introducing an alkyl group having 2 to 8 carbon atoms into the terminal or the main chain skeleton of the polyimide precursor, and the excluded volume effect of the alkyl group imparts a stable pretilt angle to the liquid crystal. It becomes possible to do. Further, it is possible to suppress the occurrence of reverse tilt and reverse twist when a TN type liquid crystal element is manufactured. When the number of carbon atoms in the alkyl group is 1 or less, a pretilt angle cannot be stably imparted to the liquid crystal, and when the number of carbon atoms exceeds 8, the probability that the alkyl group bends increases and the pretilt angle of the liquid crystal also increases. Corner stability tends to decrease.

[0018]

EXAMPLES Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example ITO was formed in a thickness of 100 nm on a glass substrate by a vacuum deposition method. Then, the following structural formula (4)

[0020]

[Chemical 7]

11 layers of a monomolecular film of a polyimide precursor (number average molecular weight of 4000) represented by the above were accumulated on the glass substrate on which the ITO was formed by the Langmuir-Blodgett method (LB method). Further, the glass substrate having the LB film formed thereon was heat-treated at 200 ° C. for 1 hour.

Two glass substrates processed by the same method as described above are prepared, and the cells are constructed so that the pulling-up directions of the two substrates are perpendicular to each other when the LB film is formed, and the nematic under reduced pressure is used. Liquid crystal (Merck, brand name ZLI15
65: 0.5% by weight of chiral agent C-15) was injected. 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 element. The completed liquid crystal cell was once heated to 100 ° C. and then gradually cooled to be initially aligned. The obtained TN type liquid crystal element showed a good liquid crystal alignment property, could impart a pretilt angle of about 10 °, and had no defects such as reverse tilt even when driven by a voltage.

Comparative Example The following structural formula (5)

[0024]

[Chemical 8]

A TN type liquid crystal device was produced in the same manner as in the example by using the polyimide precursor represented by (number average molecular weight 4000). The pretilt angle of the obtained TN type liquid crystal element was 0 °, and the reverse tilt defect was partially generated.

[0026]

The liquid crystal alignment film of the present invention does not need to be subjected to a treatment such as rubbing and has a uniform, defect-free and good alignment property. Further, it is easy to give a predetermined pretilt angle, and when a TN type liquid crystal element is manufactured, the occurrence of reverse tilt or reverse twist is suppressed.

Claims (3)

[Claims] 1. The following structural formula (1): [Wherein R ¹ has at least 2 carbon atoms and is 4
A valent group, R ² is ² having at least 2 carbon atoms
The valent group R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms ( These groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group) or a hydrogen atom. At least one of R ³ , R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other) and has 12 carbon atoms.
To 30 monovalent groups (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). Further, ^one of R ¹ and R ² has one or more long-chain alkyl groups having 2 to 8 carbon atoms. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( A liquid crystal alignment film obtained by subjecting the amphipathic polymer represented by 1) to a heat treatment in which a ring-closing reaction completely or partially occurs. 2. The following structural formula (2): [Wherein R ¹ has at least 2 carbon atoms and is 4
A valent group, R ² is ² having at least 2 carbon atoms
The valent group R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms ( These groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group) or a hydrogen atom. At least one of R ³ , R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other) and has 12 carbon atoms.
To 30 monovalent groups (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). m is 1-7. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( A liquid crystal alignment film obtained by subjecting the amphipathic polymer represented by 2) to a heat treatment in which a ring-closing reaction occurs completely or partially. 3. The following structural formula (3): [Wherein R ¹ has at least 2 carbon atoms and is 4
A valent group, R ² is ² having at least 2 carbon atoms
The valent group R ³ , R ⁴ , R ⁵ and R ⁶ is an aliphatic, cycloaliphatic or aromatic (which may be combined with each other) monovalent group having 1 to 30 carbon atoms ( These groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group) or a hydrogen atom. At least one of R ³ , R ⁴ , R ⁵ and R ⁶ is aliphatic, cycloaliphatic or aromatic (these may be combined with each other) and has 12 carbon atoms.
To 30 monovalent groups (these groups may be substituted with a halogen atom, a nitro group, an amino group, a cyano group, a methoxy group or an acetoxy group). Further, ^one of R ¹ and R ² has one or more long-chain alkyl groups having 2 to 8 carbon atoms. m is 1-7. ] A monomolecular film obtained by spreading an amphipathic polymer having a repeating unit represented by the following on the water surface is laminated on at least one substrate on which an electrode layer is formed, and then the above structural formula ( A liquid crystal alignment film obtained by subjecting the amphipathic polymer substance represented by 3) to a heat treatment such that a ring closure reaction occurs completely or partially.