JPS632095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a field effect liquid crystal display element,
The present invention relates to a liquid crystal display element in which liquid crystal molecules are vertically aligned over the entire surface of a display portion including an electrode surface.

An example of an electric field controlled birefringence type (ECB type) liquid crystal display element, which is one of the field effect type liquid crystal display elements according to the present invention, is shown in the accompanying drawings. The display element shown in the figure has a first substrate 1 and a second substrate 1' made of transparent glass, each having a predetermined distance, for example, 5 to 15 μm.
The peripheries thereof are sealed with a sealing member 2 made of, for example, fritted glass or organic adhesive, and a nematic phase liquid crystal 3 is sealed in the internal space formed by these members. The predetermined spacing is obtained by a spacer 4, for example of fiber glass, glass powder or the like. Note that the sealing member 2 may also be used as a spacer without using the spacer 4 in particular.

The first and second substrates 1 and 1' have a predetermined pattern of electrodes 5 on their opposing inner surfaces, respectively.
5' is formed, and the surface in contact with the liquid crystal is further coated with alignment control films 6, 6' for vertically aligning the liquid crystal molecules in the vicinity of the surface. Such an alignment control film has appropriate water repellency.

A first polarizing plate 7 and a second polarizing plate 7' are arranged on the outside of the substrates 1 and 1', respectively. In this case, the angle between the polarization axes of the two polarizing plates 7 and 7' is usually selected to be around 90 degrees. When such a display element performs a normal display when viewed from the first substrate side, it is a reflective display element in which a reflector 8 is disposed on the back surface of the second polarizing plate 7', or a reflective display element in which a reflector 8 is disposed on the back surface of the second polarizing plate 7', or a second polarizing plate is further used. A light guide such as an acrylic resin plate or a glass plate of a desired thickness is inserted between the reflector 8 and a light source (not shown) is placed on the side of the light guide, which is widely used as a nighttime display element. .

Here, the principle of display operation of a reflective liquid crystal display element will be explained. Now, when there is no electric field in the liquid crystal layer, external light (the first
When the ambient light incident on the first polarizing plate 7 first passes through the first polarizing plate 7, it becomes linearly polarized light along its polarization axis and enters the liquid crystal layer 3, but the liquid crystal molecules
Since this polarized light reaches the second polarizing plate 7' without any modulation, it hardly passes through this polarizing plate and the reflected light is weak, so that it appears dark to the observer.

In such a display element, when a predetermined voltage is applied to predetermined selected electrodes 5, 5' and an electric field is applied to a predetermined region of the liquid crystal layer, the liquid crystal molecules in that region will change when a certain critical condition is exceeded. Orients with an inclination to the electric field. As a result, the incident polarized light is modulated according to the inclination and becomes elliptically polarized light, so that the reflected light is observed as colored.

Therefore, desired display can be performed by applying a voltage to desired selected electrodes.

As mentioned above, in ECB type liquid crystal display elements,
In the liquid crystal sealed between both glass substrates, the liquid crystal molecules need to be aligned substantially perpendicular to the glass substrate surface. This liquid crystal alignment characteristic is achieved by alignment control films 6, 6' formed on the surface of the glass substrate facing the liquid crystal.

As this vertical alignment control film, a film having low surface energy, that is, high water repellency is generally used. Various materials have been proposed as this type of material. For example, inorganic oxides and fluorides such as CeO ₂ and MgF ₂ are used, but these require complicated film-forming methods such as vapor deposition, making continuous processing difficult. On the other hand, lecithin membranes and surfactant monomolecular membranes are simple methods, but these have poor heat resistance and are difficult to selectively form in specific areas, so they may contaminate the sealing area. , which has the disadvantage of reducing seal strength. Water-repellent treatment films such as silicone oil are also useful, but it is still difficult to prevent contamination of the seal portion. Further, there is a method in which a film is formed using a long-chain alkylsilane compound and then a fluoride film is further formed thereon by vapor deposition, but this method also requires complicated work for film formation.

The present invention has been made to overcome these drawbacks of the prior art, and provides an alignment film material that has good heat resistance and allows the alignment control film to be provided only at any desired location without contaminating the sealing part. This is what we provide.

The gist of the present invention is related to a composition that can stabilize long-chain alkyl groups involved in orientation control, and instead of applying long-chain alkylsilane in the monomer state, it is possible to use a composition that has good film-forming properties such as silanol oligomers. It is incorporated into oligomers to improve film formability and stability.

That is, to summarize the present invention, the present invention provides a liquid crystal display in which the peripheries of two transparent glass substrates having electrodes according to a desired display pattern are sealed with a sealing material, and the liquid crystal is sealed between the glass substrates. The present invention relates to a liquid crystal display element characterized in that the alignment control film is formed of a substance containing a silane-modified silanol oligomer containing a long-chain alkyl group.

Examples of materials containing the above-mentioned long-chain alkyl group-containing silane-modified silanol oligomers include the long-chain alkyl silane-modified silanol oligomers themselves and mixtures thereof with viscosity modifiers.

The silanol oligomer that plays an important role in the present invention is generally referred to as spin-on glass (SOG), which forms a silicon oxide film by forming a coating film from a solution and then baking it at a high temperature. High heat resistance. In order to impart water repellency to this, the side chain contains long-chain alkyl (C _o H _2o+1 : where n=
8-20). By doing so, the long-chain alkyl group is stabilized by bonding to the silanol skeleton, so even when subjected to high temperature treatment, this bond does not break and water repellency is maintained, resulting in a highly heat-resistant alignment control film. Become.

Such a long-chain alkylsilane-modified silanol oligomer can be obtained by adding a silane having a long-chain alkyl group to an SOG solution and reacting with stirring. Depending on the solvent used during the reaction, long-chain alkylsilane-modified silanol oligomers may precipitate out.
This can be solved by choosing a suitable solvent. It can be said that selecting a good combination of solvents is a major point in effectively implementing the present invention. The basic idea is to mix polar and non-polar solvents appropriately.

The viscosity of the solution is adjusted by adding a highly thickening resin such as nitrified cotton to the long-chain alkylsilane-modified silanol oligomer to an extent that does not impair vertical alignment.
An alignment control film is formed on a substrate by a printing method. Thereby, there is no fear of contamination of the seal portion, and the film can be formed only at any desired location, thereby achieving the objective.

Representative examples of long-chain alkylsilanes for producing long-chain alkylsilane-modified silanol oligomers include the following.

C ₈ H ₁₇ Si (OC ₂ H ₅ ) ₃ C ₁₀ H ₂₁ Si (OC ₂ H ₅ ) ₃ C ₁₂ H ₂₅ Si (OC ₂ H ₅ ) ₃ C ₁₂ H ₂₅ Si (OCH ₃ ) ₃ C ₁₄ H ₂₉ Si( _{OCH3 ) 3C16H33Si ( OCH3 )3C18H37Si(OC2H5)3C20H41Si ( OCH3 ) 3 Considering the reactivity with} silanol oligomers _,
Silane compounds having at least one methoxy or ethoxy group are effective, but other compounds can also be used if the reactivity and reaction conditions are adjusted.

Therefore, the present invention is not limited to the above representative examples.

The mechanism by which long-chain alkylsilane-modified silanol oligomers are produced by reaction with silanol oligomers is estimated to be schematically shown below.

The above reaction proceeds relatively easily, so 50
The reaction is completed by mixing and stirring at ~70°C. The concentration of long-chain alkyl groups is determined by the blending ratio during mixing, but in order to achieve vertical alignment, 5% of the hydroxyl groups in the silanol must be
If they are combined to a certain degree, the objective can be achieved at least.
On the other hand, if the concentration of long-chain alkyl groups becomes too high, the stability of the liquid may be affected and precipitation may occur, so a range of 5 to 50% is appropriate. However, when the long-chain alkyl group is an octyl group, it is necessary to increase the degree of modification.

The thickness of the alignment control film in the present invention is generally as follows:
It is 100 to 1000 Å. Further, in the present invention, the membrane may or may not be rubbed.

Note that the liquid crystal display element using the alignment control film according to the present invention can be applied to other uses by changing the liquid crystal to be sealed. For example, a color display element using a guest-host type liquid crystal added with a dichroic dye, a phase change type display element using a cholesteric liquid crystal, a display element using a smectic liquid crystal,
Furthermore, it is also useful for DSM type display elements that utilize dynamic scattering effects.

Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited thereto.

Reference example [Production example of silanol oligomer] It was manufactured using the solution polymerization method using the following procedure.

In a 200 ml flask equipped with a thermometer, stirrer, and condenser, add 20.5 g of ethyl silicate Si (OC ₂ H ₅ ) ₄ .
37.4g of ethanol, 14.4g of ethyl acetate, 1.5g of acetic anhydride, and 150mg of phosphorus pentoxide were simultaneously charged at 70°C.
to react for 1.5 hours, then add 7 g of ion-exchanged water.
was added and reacted at 70°C for 1.5 hours to obtain a silanol oligomer.

Example 1 A transparent electrode pattern of a predetermined shape was formed on a soda glass substrate, and an alignment control film was formed thereon.
As the orientation control film, a modified silanol oligomer obtained by reacting octadecyltriethoxysilane [C ₁₈ H ₃₇ Si(OC ₂ H ₅ ) ₃ ] with a silanol oligomer was used. (This modified oligomer is made by adding the long-chain alkylsilane to the silanol oligomer obtained as shown in the reference example, and adding the long-chain alkylsilane to the solid content concentration by weight.
The mixture was added to a concentration of 40% and reacted with stirring at 70°C for 2 hours. The solvent in this case is a mixture of butyl cellosolve and toluene in a 1:1 volume ratio. ) The solids concentration of the final solution was 4%.

This solution was applied to the glass substrate 1,
An alignment control film was formed on 1'. This alignment control film did not lose its ability to vertically align phenylcyclohexane liquid crystal (ZLI-1132 manufactured by Merck & Co.) up to a heat treatment temperature of 300°C.

Example 2 A long-chain alkylsilane- _modified silanol oligomer using octyltriethoxysilane [ _C8H17Si ( _{OC2H5 ) 3} ] as the long-chain alkylsilane was prepared in the same manner as in Example 1, and The formed alignment control film did not lose its ability to vertically align the liquid crystals of ZLI-1132 up to a heat treatment temperature of 300°C.

Example 3 A long-chain alkylsilane-modified silanol oligomer using decyltriethoxysilane [C ₁₀ H ₂₁ Si(OC ₂ H ₅ ) ₃ ] as the long-chain alkyl silane was prepared in the same manner as in Example 1, and The formed alignment control film did not lose its ability to vertically align the liquid crystals of ZLI-1132 up to a heat treatment temperature of 300°C.

Example 4 A long-chain alkylsilane-modified silanol oligomer using dodecyltrimethoxysilane [C ₁₂ H ₂₅ Si(OCH ₃ ) ₃ ] as the long-chain alkylsilane was prepared in the same manner as in Example 1, and a film was formed in the same manner. The alignment control film also vertically aligned the liquid crystal of ZLI-1132 up to a heat treatment temperature of 300°C.

Example 5 Tetradecyltrimethoxysilane [C ₁₄ H ₂₉ Si(OCH ₃ ) ₃ ] or hexadecyltrimethoxysilane [C ₁₆ H ₃₃ Si
(OCH ₃ ) ₃ ] or eicosyltriethoxysilane [C ₂₀ H ₄₁ Si(OC ₂ H ₅ ) ₃ ] was prepared in the same manner as in Example 1. Each of the alignment control films applied vertically aligned the liquid crystals of ZLI-1132 up to a heat treatment temperature of 300°C.

Example 6 To each of the solutions prepared in Examples 1 to 5, 1% by weight of nitrified cotton (HE2000 manufactured by Asahi Kasei Corporation) was added,
The viscosity was increased and an orientation control film was formed by a printing method. The alignment control film created in this way vertically aligned the liquid crystals of ZLI-1132 up to a heat treatment temperature of 300°C.

Comparative Example 1 The alignment control film formed by spin coating using only each of the long-chain alkylsilanes shown in Examples 1 to 5 was not uniform, and after heat treatment at 150°C for 1 hour, ZLI-1132 did not exhibit vertical orientation.

Comparative Example 2 An alignment control film formed by spin coating a solution in which 1% by weight of the nitrified cotton shown in Example 6 was added to each of the long-chain alkylsilanes shown in Examples 1 to 5 was a uniform film. However, after heat treatment at 150℃, ZLI
-1132 did not show vertical orientation.

As is clear from the above examples and comparative examples,
The alignment control film of the present invention has high heat resistance, a uniform film can be obtained, the film can be formed only at desired locations by a printing method without contaminating the sealing part, and when used in a liquid crystal display element, All showed good vertical alignment.

[Brief explanation of the drawing]

The accompanying drawing is a cross-sectional view of a liquid crystal element. 1, 1': glass substrate, 2: sealing material, 3: liquid crystal layer, 4: spacer, 5, 5' transparent electrode, 6,
6': Orientation control film, 7, 7': Polarizing plate, 8: Reflector.

Claims (1)

[Claims] 1. In a liquid crystal display element in which the peripheries of two transparent glass substrates having electrodes according to a desired display pattern are sealed with a sealing material, and liquid crystal is sealed between the glass substrates, a long chain A liquid crystal display element comprising an alignment control film made of a substance containing an alkyl group-containing silane-modified silanol oligomer. 2. The liquid crystal display element according to claim 1, wherein the substance containing the modified silanol oligomer is a mixture of a long-chain alkylsilane-modified silanol oligomer and a viscosity modifier.