JPH0618898A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To uniformalize optical characteristics, to unify the inclination directions of liquid crystal molecules when an electric field is impressed thereto and to enable the execution of stable display operations by laminating monomolecular films of the reaction compd. of polyamic acid and long-chain alkyl amine and imidizing the films at a specific imidization rate, thereby forming perpendicularly oriented films. CONSTITUTION:Transparent electrodes 4, 5 are respectively formed on the surfaces facing each other of a pair of transparent substrates 1, 2 consisting of glass, etc. The electrode forming surfaces of the two substrates 1, 2 are coated with transparent insulating films 6, 7 consisting of silicon oxide, etc., and the perpendicularly oriented films 8, 9 for orienting the liquid crystal molecules A nearly perpendicularly to the planes of the substrates 1, 2 are formed on these insulating films 6, 7. Both of the perpendicularly oriented films are formed by laminating the monomolecular films of the reaction compd. of the polyamic acid and the long-chain alkyl amine in plural layers and imidizing these films at the imidization rate alpha% in a 0<alpha<50 range.

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 which liquid crystal molecules are vertically aligned.

[0002]

2. Description of the Related Art A liquid crystal device in which liquid crystal molecules are vertically aligned has a dynamic scattering (DS) mode, an electric field controlled birefringence (EC
Among the B) modes, there are vertical alignment mode, phase transition mode, and the like.

In these liquid crystal elements, a transparent electrode and a vertical alignment film for vertically aligning liquid crystal molecules on the surfaces of a pair of transparent substrates facing each other across a liquid crystal layer are provided. The vertical alignment film is conventionally formed by coating a surface of a substrate with a surfactant solution having a long-chain alkyl group and drying.

[0004]

However, in the conventional liquid crystal device in which the vertical alignment film is formed by applying the surfactant solution as described above, the alignment property of the vertical alignment film varies, The liquid crystal molecules cannot be vertically aligned uniformly, so that uniform optical characteristics cannot be obtained.
In addition, since the liquid crystal molecules are aligned almost vertically to the alignment film surface, the tilt direction of the liquid crystal molecules when an electric field is applied to the liquid crystal layer is not constant, and thus stable display operation cannot be obtained. I had a problem.

An object of the present invention is to uniformly align liquid crystal molecules in a substantially vertical direction so that the optical characteristics are uniform, and moreover, the tilt direction of the liquid crystal molecules when an electric field is applied is kept constant to perform a stable display operation. It is to provide a liquid crystal element that can be manufactured.

[0006]

A liquid crystal device of the present invention comprises a transparent electrode and liquid crystal molecules on a surface of a pair of transparent substrates facing each other with a liquid crystal layer between them, with respect to a normal line of the substrate surface. A vertical alignment film for aligning with a predetermined inclination is formed, and the vertical alignment film is formed by laminating a monomolecular film of a reaction compound of a polyamic acid and a long-chain alkylamine and having an imidization ratio α%. It is characterized by comprising a film imidized in the range of 0 <α <50.

[0007]

The alignment film obtained by imidizing a film obtained by laminating a monomolecular film of the reaction compound of the polyamic acid and the long-chain alkylamine in the range where the imidization ratio α% is 0 <α <50 is such that the liquid crystal molecules are aligned. The orientation is such that it is oriented almost vertically with a slight pretilt angle with respect to the normal to the film surface, and the orientation is uniform over the entire orientation film. For this reason,
According to the liquid crystal element of the present invention, it is possible to uniformly align the liquid crystal molecules to obtain uniform optical characteristics, and the liquid crystal molecules are uniformly aligned with the above pretilt angle. A stable display operation can be performed by keeping the tilt direction of the liquid crystal molecules constant.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view of a liquid crystal element. In this liquid crystal element, a pair of transparent substrates 1 and 2 made of glass or the like are bonded via a frame-shaped sealing material 3, and liquid crystal is sealed in a region surrounded by the sealing material 3 between the substrates 1 and 2. The transparent electrodes 4 and 5 are formed on the surfaces of the substrates 1 and 2 that face each other. The electrode forming surfaces of the substrates 1 and 2 are covered with transparent insulating films 6 and 7 made of silicon oxide (SiO ₂ ), and the liquid crystal molecules A are formed on the insulating films 6 and 7. Vertically oriented films 8 and 9 for orienting the substrate substantially perpendicularly to the surfaces of the substrates 1 and 2 are formed.

Each of the vertical alignment films 8 and 9 is a film in which a monomolecular film of a reaction compound of a polyamic acid and a long-chain alkylamine is laminated in a plurality of layers and the imidization ratio α% is 0 <α <.
It is imidized in the range of 50.

The vertical alignment films 8 and 9 are formed by the following method. Although the formation of the vertical alignment film 8 provided on one substrate 1 will be described here, the vertical alignment film 9 provided on the other substrate 2 is also formed in the same manner.

The above polyamic acid is represented by the following structural formula [Chemical Formula 3], and this polyamic acid is composed of the tetracarboxylic dianhydride represented by the structural formula [Chemical Formula 1] and [Chemical Formula 2]. It is obtained by synthesizing the diamine represented by the structural formula.

[0013]

[Chemical 1]

[0014]

[Chemical 2]

[0015]

[Chemical 3]

The long-chain alkylamine is for imparting hydrophobicity to the hydrophilic polyamic acid, and the long-chain alkylamine is represented by the following structural formula [Chemical formula 4].

[0017]

[Chemical 4]

A solution prepared by dissolving the polyamic acid in a solvent and a solution prepared by dissolving the long-chain alkylamine in the same solvent are mixed at a ratio of 1: 1, and the polyamic acid and the long-chain alkylamine are subjected to an ionic bond reaction. Then, a solution of the polyamic acid derivative compound (polyamic acid salt) represented by the following structural formula [Chemical Formula 5] is prepared. As the solvent for the polyamic acid and the long-chain alkylamine, a mixed solvent in which NMP (N-methyl-2-pyrrolidinone) and benzene are mixed at a ratio of 1: 1 is used. Also,
The concentration of the long-chain alkylamine solution is the same as or higher than the concentration of the polyamic acid solution.

[0019]

[Chemical 5]

The horizontal alignment film 8 is formed by laminating the monomolecular film of the polyamic acid derivative compound as a required layer on the substrate 1 on which the transparent electrode 4 is formed and the insulating film 6 is formed thereon by the LB method. It is adhered, and the laminated film of this monomolecular film is formed by imidization by heat treatment. FIG. 2 shows a method of depositing a monomolecular film of a polyamic acid derivative compound on the substrate 1 by the LB method. The deposition of this monomolecular film is performed as follows. First, the surface of the substrate 1 on which the monomolecular film is adhered (the surface of the insulating film 6) is subjected to a hydrophilic treatment, and the substrate 1 is vertically immersed in water in the water tank 10.

Next, after the water surface in the water tank 10 is made to be a still water surface, the bar-shaped moving barrier 11 and the substrate 1 provided at the water surface height.
The solution of the above polyamic acid derivative compound is dropped on the water surface between and to develop the monomolecular film a thereof on the water surface.

Next, the moving barrier 11 is moved toward the substrate so that the single molecules on the water surface are densely packed, and the surface pressure of the monomolecular film a is adjusted to a constant pressure (25 dyn / cm), while the moving barrier 11 is moved to the substrate. The monomolecular film a is moved in a predetermined direction (2 mm / min) while pushing the monomolecular film a toward the substrate, and the substrate 1 is pulled up in synchronization with this to deposit the monomolecular film a on the water surface onto the substrate 1. .

At this time, the monomolecules on the water surface are pulled up by adhering to the substrate 1 whose hydrophilic portion has been subjected to the hydrophilic treatment, so that the molecules of the monomolecular film a are aligned in almost one direction. In this state, it is deposited on the substrate 1. The following is the monolayer a
The above-mentioned deposition process is repeated to laminate the monomolecular film a on the substrate 1 into a required layer.

After laminating the monomolecular film a of the polyamic acid derivative compound on the substrate 1 in the above-described manner, the laminated film of the monomolecular film a is imidized at a rate of less than 50% α (0 % <Α <50%) to form the vertical alignment film 8 by imidization.

The imidation of the laminated film of the monomolecular film a is performed by heat treatment, chemical treatment with a solution of acid anhydride or the like, or both of the heat treatment and the chemical treatment. Further, the imidization ratio α is controlled by the heat treatment temperature or the concentration of the chemical treatment solution (solution of acid anhydride or the like).

The vertical alignment film 8 formed by imidizing the laminated film of the monomolecular film a of the polyamic acid derivative compound is a polyimide-based film.
It has a structure like.

[0027]

[Chemical 6]

The alignment films 8 and 9 formed of the polyimide films formed on the substrates 1 and 2 as described above align the liquid crystal molecules A substantially vertically with a slight pretilt angle with respect to the normal line of the alignment film surface. It has an orientation, and the orientation is uniform over the entire alignment film. The alignment films 8 and 9 made of the polyimide film have such an alignment property.
This is because the imidization ratio α is less than 50% (0% <α <50%).

That is, since the monomolecular film a of the polyamic acid derivative compound itself has a vertical alignment property, even if the laminated film of this monomolecular film a is not imidized to form a polyimide film, can do. However, this non-imidized vertical alignment film has a uniform alignment property over the entire alignment film, but since the liquid crystal molecules are aligned almost completely perpendicular to the alignment film surface, an electric field is applied to the liquid crystal layer. The tilt direction of the liquid crystal molecules when applied is not constant, so that stable display operation cannot be obtained.

Further, the polyimide film obtained by imidizing the laminated film of the monomolecular film a with an imidization ratio of 50% or more has an inclination angle of the liquid crystal molecules with respect to the normal line of the film surface to be larger than 45 °, and Will be oriented horizontally.

On the other hand, the alignment films 8 and 9 made of a polyimide film having an imidization ratio of less than 50% have a uniform alignment property over the entire alignment film, and moreover, the liquid crystal molecules A on the alignment film surface. It has an orientation property of orienting almost vertically with a slight pretilt angle with respect to the normal line.

Therefore, according to the liquid crystal element of the above embodiment, the liquid crystal molecules A can be uniformly aligned to obtain uniform optical characteristics, and the liquid crystal molecules A are uniformly aligned with the pretilt angle. Therefore, the tilt direction of the liquid crystal molecules A when an electric field is applied can be made constant, and a stable display operation can be performed.

[0033]

According to the liquid crystal element of the present invention, a vertical alignment film formed on both substrates is a film obtained by laminating a monomolecular film of a reaction compound of a polyamic acid and a long-chain alkylamine, with an imidization ratio α%. Is imidized in the range of 0 <α <50, the liquid crystal molecules can be uniformly aligned vertically with an appropriate inclination with respect to the normal to the substrate surface, resulting in uniform optical characteristics. Moreover, the tilting direction of the liquid crystal molecules when an electric field is applied can be made constant, and a stable display operation can be performed.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal element showing an embodiment of the present invention.

FIG. 2 is a diagram showing a method for depositing a monomolecular film.

[Explanation of symbols]

 1, 2 ... Substrate 4,5 ... Electrode 6,7 ... Insulating film 8,9 ... Vertical alignment film (less than 50% imidized film) A ... Liquid crystal molecule

Claims (1)

[Claims] 1. A vertical alignment film for aligning a transparent electrode and liquid crystal molecules on a surface of a pair of transparent substrates facing each other across a liquid crystal layer with a predetermined inclination with respect to a normal line of the substrate surface. And the vertical alignment film is formed by laminating a monomolecular film of a reaction compound of a polyamic acid and a long-chain alkylamine, and is imidized at an imidization ratio α% of 0 <α <50. A liquid crystal element characterized by comprising a film.