JPS62231221A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain a uniform and superior orientation film by forming an orientation film comprising Langmuir-Blodgett's film on a substrate. CONSTITUTION:An orientation film comprising Langmuir-Blodgett's film (LB film) is provided on a substrate in a liquid crystal element constituted by sealing liquid crystals in a hollow part formed by confronting substrates. The orientation film of the liquid crystal is formed by filling a water-bath having a barrier with water, and moving the barrier while dropping a deriv. of diacetylene on the water surface. On the water surface, the interaction of each single molecule scattered separately in the gaseous state film is enhanced gradually forming condensed film of two-dimensional solid. In the liquid crystal molecule, polar groups such as Schiff's base, etc., are distributed primarily in the central part of the molecule, and alkyl groups are distributed in the terminal part of the molecule. Accordingly, if hydrophobic groups are present on the surface of the substrate, the liquid crystal has smaller surface energy in perpendicular arrangement than in parallel arrangement, thus the liquid crystal is stably arranged in perpendicular for the substrate.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal element having a novel alignment film.

[Prior Art] In liquid crystal display elements, liquid crystal lenses, etc., by applying a voltage to the electrodes of a transparent conductive film provided on the inner surface of the liquid crystal cell, the liquid crystal molecules in the liquid crystal cell change their length in the direction of the electric field. They are rotated so that their axes are aligned, and the refractive index changes to display information and change the refractive power.

In order to facilitate the operation of the liquid crystal by applying this voltage, the surface of the substrate in the liquid crystal cell is subjected to alignment treatment and the liquid crystal is sealed within the cell, but this alignment treatment has conventionally been performed by rubbing treatment.

[Problems to be solved by the invention] However, this rubbing process has problems with reproducibility, and it is difficult to apply this process to liquid crystal cell substrates that use non-flat substrates such as spherical surfaces or small substrates. It's becoming difficult.

An object of the present invention is to provide a novel liquid crystal element in which a liquid crystal alignment film is formed using a Langmuir-Prodgett film (hereinafter referred to as LB film). therefore,
A liquid crystal element having a uniform and excellent alignment film can be provided without a difficult rubbing process as shown in the above conventional example.

[Means for Solving the Problems] A liquid crystal element according to the present invention is a liquid crystal element constructed by filling a hollow part formed by opposing substrates with a liquid crystal, in which an alignment film made of an LB film is provided on the substrates. This is a liquid crystal element comprising:

[Function] This LB film will be briefly described below. This LB
The film is an ultra-thin film of a surfactant having a parent group and a hydrophobic group, as shown in, for example, "Electronics", December 1985 issue, pp. 74-80.

This film forms a +1 molecular film on the container on the water surface, and this can be transferred onto a solid substrate by a vertical dipping method or the like. By repeating the same procedure, it has become possible to create multilayer films made of single molecules.

In this invention, an LB film of an organic substance such as a diacetylene derivative is formed on a substrate constituting a liquid crystal cell by a vertical dipping method or the like. Since this LB film has hydrophilic U and hydrophobic groups, these are utilized to orient the liquid crystal molecules.

Furthermore, if the LB film is mechanically weak, a strong LB film can be formed by irradiating the substrate on which the LB film is formed with light, heat, or an electron beam to cause a polymerization reaction. Furthermore, if the LB film is formed using a conductive material, the electrodes of the transparent conductive layer and the alignment film of the liquid crystal can be made using the same material and in the same process. Even if the container is shaped like a Fresnel lens, an alignment film that also serves as a transparent conductive electrode can be formed on the surface of the container.

[Example] Hereinafter, a method for forming a liquid crystal alignment film formed on the surface of a liquid crystal cell of a liquid crystal element of the present invention will be described.

A water tank with a barrier is filled with water, and a diacetylene derivative [CH3 (CH2) is placed on the surface of the tank. -2-Cmi c=-c-(CH2)
6-COOHI or straight chain fatty acids [CH3(CH2)n
A solution of 2-C0OH](]n-16 to 22 is dropped. Then, as the barrier is moved, the interaction of single molecules gradually changes from the gas film in which single molecules are scattered on the dropping surface. It becomes stronger and becomes a condensed film in a two-dimensional solid state.The C0OH group in the above organic substance is a hydrophilic group,
H(CH2). The -1 group and the CH3(CH2)n-3 group are hydrophobic groups. Therefore, the two-dimensional solid condensation film forms a 111-molecule film with the C0OH group facing down on the water surface in the aquarium.

Next, when the substrate that forms the liquid crystal cell, which is made of glass or optical resin and has both sides polished to an optical surface, is vertically inserted or pulled up into the water tank under this surface pressure, the surface of the liquid crystal cell on the water surface is A monolayer of an acetylene derivative or a straight chain fatty acid is transferred onto a substrate.

That is, when the substrate is hydrophilic, such as a slide glass, the initial single molecule does not adhere to the substrate when it is inserted, but the hydrophobic group of the single molecule adheres to the substrate when it is pulled up. Further, when the substrate is hydrophobic such as acrylic, the hydrophobic group of the monomolecule is attached to the substrate when the substrate is first inserted. After the first single molecule adheres, it is mainly controlled by the chemical structure of the Li molecule, but depending on the concentration of pH 1-containing salts in the aqueous phase, surface pressure, temperature, etc. can. As a general tendency, a Y-shaped cumulative film tends to be formed. For example, the diacetylene derivative CH3(CH2)m-(jC-(:=C-(C)(2)
For n-COOH (m-8,9, n-8, Cd salt), pH
-7, the temperature is 15'', and the surface pressure is -20 mN/m, resulting in a Y-shaped cumulative film.

Also, straight chain fatty acid CH3 (CH2). -, -COOH(
n-16 to 22, Ba salt), pH-7.1, temperature 2
At 0° C. and a surface pressure of 30 mN/m, a Y-shaped cumulative film is formed.

If the accumulated film transferred to the substrate by the above operation is mechanically weak, it is irradiated with light, heat, or electron beams to cause a polymerization reaction to improve its mechanical strength. For example, in the case of a diacetylene derivative, irradiation with a 240W mercury UV lamp for about 30 minutes results in a polymerized and strong cumulative film.

Next, the relationship between the alignment film formed on the substrate of the liquid crystal cell formed of the LB film and the liquid crystal molecules will be explained. Liquid crystal molecules mainly have a polar group such as a ship base at the center of the molecule and an alkyl group at the end. Therefore, when hydrophobic groups are formed on the surface of the substrate of a liquid crystal cell, the liquid crystal molecules are more stable when they are arranged in a direct manner, since the surface free energy is smaller than when they are arranged in parallel. That is, the liquid crystal molecules are vertically aligned. Further, when hydrophilic groups are formed on the substrate surface, the surface free energy becomes smaller when the liquid crystal molecules are arranged in parallel due to the bonding force between the polar group at the center and the hydrophilic group. Therefore, the long axes of liquid crystal molecules are aligned parallel to the substrate.

The alignment film formed on the substrate in this way can be easily formed even when the surface of the substrate is a discontinuous surface such as a spherical surface or a Fresnel lens surface, and it can be easily formed even if the surface of the substrate is a discontinuous surface such as a spherical surface or a Fresnel lens surface. It is not necessary to form the alignment film by a special operation.

In addition, if the monomolecular film is formed from a conductive material such as a diacetylene derivative or a pyridinium-TCNQ complex, the transparent conductive film can be used on the substrate of a liquid crystal cell, which has difficulty adhering to plastic. Since the step of forming the liquid crystal element can also be omitted, the liquid crystal element can be manufactured at low cost.

The liquid crystal element of the present invention is constructed by forming a liquid crystal cell by opposing transparent substrates on which alignment films are formed as described above, and sealing liquid crystal inside the cell. Therefore, it is possible to provide an excellent liquid crystal element with uniform alignment of liquid crystals, whether it is a liquid crystal element having a flat liquid crystal cell or a liquid crystal lens element having a lens shape.

[Effects of the Invention] The liquid crystal element of the present invention uses a Langmuir-Prodgett film to align the liquid crystal cell to the substrate, compared to the conventional rubbing process. Even elements and curved substrates can be easily formed. In addition, even when the surface of the substrate is composed of discontinuous surfaces such as a Fresnel lens surface, and alignment treatment using conventional rubbing processing is impossible,
A liquid crystal element can be obtained in which alignment treatment is performed over the entire surface of the liquid crystal cell and is much more uniform and highly accurate than that of conventional devices.

Claims (1)

[Claims] A liquid crystal element configured by sealing a liquid crystal in a hollow formed by opposing substrates, characterized in that an alignment film made of a Langmuir-Prodgett film is provided on the substrates. liquid crystal element.