JPH0618889A - Liquid crystal element - Google Patents

Abstract

(57) [Abstract] [Purpose] A horizontal alignment film has an alignment control force suitable for ferroelectric or antiferroelectric liquid crystals to improve the memory property of the alignment state of liquid crystal molecules and to prevent "flickering". Get the display. [Structure] Horizontal alignment films 8 and 9 are formed on substrates 1 and 2 by the LB method.
It was formed of a monolayer deposited on top.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal element using a ferroelectric or antiferroelectric liquid crystal.

[0002]

2. Description of the Related Art Recently, a ferroelectric liquid crystal element using a ferroelectric or antiferroelectric liquid crystal has attracted attention. This ferroelectric liquid crystal element is one in which a ferroelectric or antiferroelectric liquid crystal is sealed between a pair of transparent substrates provided with a transparent electrode and a horizontal alignment film, and a pair of transparent substrates are provided on the light incident side and the light emitting side. It is used with a polarizing plate.

This ferroelectric liquid crystal element utilizes the memory property of the molecular alignment state possessed by the ferroelectric or antiferroelectric liquid crystal, and the ferroelectric or antiferroelectric liquid crystal has a smectic layer structure. Thus, the liquid crystal molecules have a plurality of molecular alignment states and the alignment direction of the liquid crystal molecules changes according to the electric field.

That is, the ferroelectric liquid crystal has the stability (bistability) of two molecular alignment states, and when an electric field of one polarity is applied, all liquid crystal molecules are in the normal line of the smectic layer structure. On the other hand, they are arranged uniformly in a direction tilted at a tilt angle in one direction, and the state is maintained even after the application of the electric field is stopped. When an electric field of opposite polarity is applied, all liquid crystal molecules are uniformly arranged in a direction tilted by a tilt angle opposite to the normal line, and the state is maintained even after the application of the electric field is cut off. keep.

Further, the antiferroelectric liquid crystal has the stability of three molecular alignment states. The first stable state is a state when an electric field of one polarity is applied, and in this case, all liquid crystal molecules are tilted at a tilt angle in one direction with respect to the normal line of the smectic layer structure. Are evenly arranged, and the state is maintained even after the application of the electric field is cut off. The second stable state is a state when an electric field of opposite polarity is applied, and at this time, all liquid crystal molecules are uniformly arranged in a direction tilted by a tilt angle opposite to the normal line. However, the state is maintained even after the application of the electric field is stopped. The third stable state is a state when no electric field is applied or when a weak electric field is applied, and in this state, liquid crystal molecules are alternately arranged in opposite directions with respect to the normal of the smectic layer structure at the same tilt angle. (Arrange in alternate directions for each layer). The average alignment direction of the liquid crystal molecules in the entire liquid crystal layer in the third stable state is the normal direction of the smectic layer structure.

Then, when a ferroelectric or antiferroelectric liquid crystal is sealed between a pair of transparent substrates provided with a transparent electrode and a horizontal alignment film, the direction of the normal line of the smectic layer structure is horizontal alignment films of both substrates. The alignment treatment directions of these alignment films are substantially parallel to each other (the alignment treatment directions are the same or opposite), and a pair of liquid crystal elements are arranged on the light incident side and the light emitting side. If the polarization axis (transmission axis or absorption axis) of the polarizing plate is set according to the orientation processing direction, the transmission state of light is controlled by changing the alignment state of liquid crystal molecules by applying an electric field, Display can be performed.

By the way, as a horizontal alignment film provided on both substrates of the ferroelectric liquid crystal device, conventionally, an organic polymer compound film such as polyimide is formed on the substrate and the film surface is rubbed in one direction. Has been formed.

[0008]

However, a conventional ferroelectric liquid crystal device in which a horizontal alignment film obtained by rubbing an organic polymer compound film of polyimide or the like is formed on both substrates is a memory having a liquid crystal molecule alignment state. There is a problem that the property (retention of the array state after the application of the electric field is cut off) is weak, and therefore "flicker" occurs in the display.

This is because the horizontal alignment film obtained by rubbing an organic polymer compound film of polyimide or the like has too strong an alignment regulating force. If the alignment film has an excessively strong alignment regulating force,
When the liquid crystal molecules aligned in a direction tilted at a certain tilt angle to the normal of the smectic layer structure by the application of an electric field are pulled back by the alignment regulating force of the alignment film, and the alignment state of the liquid crystal molecules is not applying an electric field. In order to return to the initial alignment state (the third stable state in the antiferroelectric liquid crystal), the alignment state of the liquid crystal molecules is changed and "flicker" occurs in the display.

An object of the present invention is to provide a horizontal alignment film with an alignment regulating force suitable for a ferroelectric or antiferroelectric liquid crystal to improve the memory property of the alignment state of liquid crystal molecules and to obtain a good flicker-free property. An object of the present invention is to provide a ferroelectric liquid crystal element capable of obtaining a display.

[0011]

The present invention provides a liquid crystal device in which a ferroelectric or antiferroelectric liquid crystal is sealed between a pair of transparent substrates provided with a transparent electrode and a horizontal alignment film. , Langmuir-Blodgett method.

The horizontal alignment film is, for example, a film obtained by laminating a plurality of monomolecular films of a compound obtained by reacting a polyamic acid with a long-chain alkylamine. Even a polyimide film obtained by imidizing multiple layers of a monomolecular film of a compound obtained by reacting a chain alkylamine, or a monomolecular film of a compound obtained by reacting the polyamic acid with a long-chain alkylamine, It may be a non-imidized film laminated in a plurality of layers.

[0013]

The horizontal alignment film, which is a laminated film of monomolecular films deposited on the substrate by the Langmuir-Blodgett method, has an alignment property for horizontally aligning liquid crystal molecules in one direction, and has ferroelectricity or antiferroelectricity. The alignment regulating force with respect to the dielectric liquid crystal is sufficient to regulate the direction of the normal line of the smectic layer structure, and is weaker than the conventional horizontal alignment film obtained by rubbing an organic polymer compound film such as polyimide. That is, this alignment film has an alignment regulating force suitable for the ferroelectric or antiferroelectric liquid crystal, which does not affect the stability of the molecular alignment state of the ferroelectric or antiferroelectric liquid crystal. Therefore, in the ferroelectric liquid crystal device of the present invention, liquid crystal molecules arranged in a direction tilted at a certain tilt angle with respect to the normal to the smectic layer structure are not pulled back by the alignment regulating force of the alignment film by the application of an electric field. Therefore, since the alignment state of the liquid crystal molecules does not change, the memory property of the alignment state of the liquid crystal molecules is improved, and the "flicker" of the display is eliminated.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a sectional view of a ferroelectric liquid crystal element.
In this ferroelectric liquid crystal element, a pair of transparent substrates 1 and 2 made of glass or the like are joined via a frame-shaped sealing material 3, and a region surrounded by the sealing material 3 between the substrates 1 and 2 is Ferroelectric liquid crystal or anti-ferroelectric liquid crystal A is sealed, and transparent electrodes 4 and 5 are provided on the surfaces of the substrates 1 and 2 facing each other. In addition, the electrode forming surfaces of the two substrates 1 and 2 are covered with transparent insulating films 6 and 7 made of silicon oxide (SiO ₂ ) or the like.
Horizontal alignment films 8 and 9 are provided for horizontally aligning the liquid crystal molecules of the ferroelectric liquid crystal A. The liquid crystal element is of a simple matrix type. The electrode 4 formed on one substrate 1 is a scanning electrode, and the electrode 5 formed on the other substrate 2 is a signal electrode.

A horizontal alignment film 8 provided on both the substrates 1 and 2,
Each of 9 is formed of a laminated film of monomolecular films deposited on the substrates 1 and 2 by the Langmuir-Blodgett method.

In the Langmuir-Blodgett method (hereinafter referred to as the LB method), a monomolecular film is formed on a still water surface, and a substrate previously dipped in water vertically is pulled up at a constant speed while a single film on the water surface is pulled up. This is a method of depositing a molecular film on a substrate, and the alignment films 8 and 9 made of a laminated film of monomolecular films deposited on the substrates 1 and 2 by the LB method make liquid crystal molecules unidirectionally. It has a horizontal orientation.

The alignment regulating force of the alignment films 8 and 9 on the ferroelectric or antiferroelectric liquid crystal A is sufficient to regulate the direction of the normal line of the smectic layer structure, and
It is weaker than the conventional horizontal alignment film obtained by rubbing an organic polymer compound film such as polyimide. That is, the alignment films 8 and 9 are suitable for the ferroelectric or antiferroelectric liquid crystal A without affecting the stability of the molecular alignment of the ferroelectric or antiferroelectric liquid crystal A. Have power

Therefore, in the ferroelectric liquid crystal element, liquid crystal molecules arranged in a direction tilted at a certain tilt angle with respect to the normal of the smectic layer structure by applying an electric field have alignment films 8 and 9.
It is not pulled back by the alignment control force of the liquid crystal, and therefore the alignment state of the liquid crystal molecules does not change, so the memory property of the alignment state of the liquid crystal molecules is improved, and the "flickering" of the display occurs.
Disappears. Next, specific examples of the present invention will be described. (First embodiment)

In the first embodiment, the horizontal alignment films 8 and 9 are composed of a plurality of layers (for example, 5 to 6) of a monomolecular film of a compound obtained by reacting a polyamic acid with a long-chain alkylamine.
The film laminated on (layer) was used as an imidized polyimide film.

The horizontal alignment films 8 and 9 are formed by the following method. Although the formation of the horizontal alignment film 8 provided on one substrate 1 will be described here, the horizontal 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 the polyamic acid includes a tetracarboxylic dianhydride represented by the structural formula [Chemical Formula 1] and a chemical formula [Chemical Formula 2]. It is obtained by synthesizing the diamine represented by the structural formula.

[0023]

[Chemical 1]

[0024]

[Chemical 2]

[0025]

[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].

[0027]

[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.

[0029]

[Chemical 5]

The horizontal alignment film 8 is formed by laminating the monomolecular film of the above polyamic acid derivative compound in a required layer by the LB method on the substrate 1 on which the transparent electrode 4 is formed and the insulating film 6 is formed thereon. 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 to condense the single molecules on the water surface, and the surface pressure of the monomolecular film a is adjusted to a constant pressure (25 dyn / cm). 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 in the monomolecular film a, the molecules are arranged almost in 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 as a required layer in this way, 3
A heat treatment of heating at a high temperature of 00 ° C. or higher for about 1 hour is performed to form the laminated film of the monomolecular film a into a polyimide film.

This polyimide film is obtained by removing the alkylamine of a polyamic acid derivative compound, which is a compound in which a polyamic acid and a long-chain alkylamine are ion-bonded, and imidizing it, and has a structure as shown in the following [Chemical formula 6]. I have

[0036]

[Chemical 6]

The polyimide film thus formed is a film in which the polyimide main chain is oriented in the pulling direction of the substrate 1 when the monomolecular film a is deposited by the LB method,
Since the liquid crystal molecules are oriented horizontally in one direction, the polyimide film can be directly used as the horizontal alignment film 8 without rubbing the film surface.

That is, in this embodiment, a monomolecular film a of a polyamic acid derivative compound obtained by reacting a polyamic acid with a long-chain alkylamine is formed on a pair of substrates 1 and 2 of a ferroelectric liquid crystal element by the LB method. The laminated film of the monomolecular film a is imidized into a polyimide film by heat treatment, and the polyimide film is used as the horizontal alignment films 8 and 9.

The horizontal alignment films 8 and 9 thus formed
Is sufficient to regulate the direction of the normal line of the smectic layer structure to the ferroelectric or antiferroelectric liquid crystal A, and does not affect the stability of the alignment state of liquid crystal molecules. It has an alignment regulating force suitable for the ferroelectric or antiferroelectric liquid crystal A.

Therefore, according to the ferroelectric liquid crystal element of the above-mentioned embodiment, the liquid crystal molecules arranged in a direction tilted at a certain tilt angle with respect to the normal of the smectic layer structure by the application of the electric field have the alignment regulating force of the alignment film. Since the arrangement state does not change due to being pulled back by, the memory property of the arrangement state of the liquid crystal molecules can be improved, and a good display without "flicker" can be obtained. (Second Embodiment) Next, a second embodiment of the present invention will be described.

In the second embodiment, a compound obtained by reacting a polyamic acid represented by the structural formula [Chemical Formula 3] with a long-chain alkylamine represented by the structural formula [Chemical Formula 4], That is, a monomolecular film of the polyamic acid derivative compound represented by the structural formula of [Chemical Formula 5] is laminated in a plurality of layers (for example, 5 to 6 layers) on the substrates 1 and 2 by the above-mentioned LB method,
The monolayer film is dried at a temperature at which it does not imidize to evaporate the solvent of the polyamic acid and the long-chain alkylamine (mixed solvent of NMP and benzene), and the film remaining on the substrate 1 is leveled. The alignment films 8 and 9 are used.

The orientation of the orientation film formed by laminating the monomolecular films of the polyamic acid derivative compound varies depending on the carbon number of the long-chain alkyl group represented by R ₃ in the structural formula [Chemical Formula 5]. , For example, the carbon number of R ₃ is 18
The monomolecular film made of the polyamic acid derivative compound of 1 has vertical alignment, and the monomolecular film made of the polyamic acid derivative compound of R ₃ having 14 carbon atoms has horizontal alignment.

Therefore, in this example, as the polyamic acid derivative compound, the polyamic acid derivative compound in which R ₃ has 14 carbon atoms was used. The monomolecular film obtained by depositing the polyamic acid derivative compound on the substrates 1 and 2 by the LB method has an orientation property of horizontally aligning liquid crystal molecules in one direction, and thus the laminated film of the monomolecular film is formed. The horizontal alignment films 8 and 9 can be formed without imidization.

That is, in this embodiment, a monomolecular film of a polyamic acid derivative compound obtained by reacting a polyamic acid with a long-chain alkylamine is formed on a pair of substrates 1 and 2 of a ferroelectric liquid crystal element by the LB method. The horizontal alignment films 8 and 9 are formed by laminating the monomolecular films in a plurality of layers.

The horizontal alignment films 8 and 9 thus formed
Is sufficient to regulate the direction of the normal line of the smectic layer structure to the ferroelectric or antiferroelectric liquid crystal A, and does not affect the stability of the alignment state of liquid crystal molecules. , And has an alignment regulating force suitable for the ferroelectric or antiferroelectric liquid crystal A.

Therefore, also in the ferroelectric liquid crystal element of this embodiment, liquid crystal molecules arranged in a direction tilted at a certain tilt angle with respect to the normal of the smectic layer structure by the application of an electric field are the alignment regulating force of the alignment film. The arrangement state does not change due to being pulled back, and therefore, the memory property of the arrangement state of the liquid crystal molecules can be improved, and a good display without “flicker” can be obtained.

Further, in this embodiment, the horizontal alignment film 8,
Since the non-imidized film obtained by laminating a plurality of monomolecular films of the compound obtained by reacting the polyamic acid described in 9 with a long-chain alkylamine contains a long-chain alkyl group,
Compared with the imidized alignment film (polyimide film) used as the horizontal alignment films 8 and 9 in the first embodiment, the surface tension and polar force components are smaller, and therefore the memory property of the alignment state of liquid crystal molecules is further improved. be able to.

[0048]

According to the liquid crystal element of the present invention, since the horizontal alignment films provided on both substrates are formed by the LB method, the horizontal alignment films are aligned suitable for ferroelectric or antiferroelectric liquid crystals. It is possible to improve the memory property of the alignment state of the liquid crystal molecules by providing the regulation power, and to obtain a good display without "flickering".

[Brief description of drawings]

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

FIG. 2 is a diagram showing a method of depositing a monomolecular film on a substrate.

[Explanation of symbols]

 1, 2 ... Transparent substrate 4, 5 ... Transparent electrode 6, 7 ... Insulating film 8, 9 ... Horizontal alignment film (laminated film of monomolecular film) A ... Ferroelectric or antiferroelectric liquid crystal

Claims (3)

[Claims] 1. In a liquid crystal device in which a ferroelectric or antiferroelectric liquid crystal is sealed between a pair of transparent substrates provided with transparent electrodes and a horizontal alignment film, the horizontal alignment film is formed by a Langmuir-Blodgett method. A liquid crystal device characterized in that 2. The horizontal alignment film is a polyimide film obtained by imidizing a film obtained by laminating a plurality of monomolecular films of a compound obtained by reacting a polyamic acid with a long-chain alkylamine. 1. The liquid crystal device according to item 1. 3. The liquid crystal device according to claim 1, wherein the horizontal alignment film is a film obtained by laminating a plurality of monomolecular films of a compound obtained by reacting a polyamic acid with a long-chain alkylamine. .