JPS632094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a field effect liquid crystal display element,
In particular, the present invention relates to a liquid crystal display element in which liquid crystal molecules are vertically aligned on an electrode substrate 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. In the display element shown in the figure, a first substrate 1 and a second substrate 1' each made of transparent glass or the like are arranged at a predetermined distance, for example,
The peripheries are sealed with a sealing member made of fritted glass, organic adhesive, etc., that is, sealing material 2, and a nematic phase liquid phase is formed in the internal space formed by these. 3 is included. The predetermined distance is determined by a spacer 4 made of fiber glass, glass powder, etc.
obtained by. Note that the sealing material 2 may also be used as the spacer 4 without using the spacer 4 in particular.

The first and second substrates 1 and 1' each 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 formed by 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, a reflector 8 is provided on the back surface of the second polarizing plate 7'.
A light guide such as an acrylic resin plate or a glass plate having a desired thickness is inserted between the reflective display element arranged with the reflective display element, or the second polarizing plate and the reflector 8, and the light guide body such as an acrylic resin plate or a glass plate is inserted at an appropriate position on the side surface of the reflective display element. It is widely used as a nighttime display device equipped with a light source.

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 becomes weak and 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. , the orientation is inclined with respect 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, a desired display can be performed by applying a voltage to desired selected electrodes.

As described above, in the ECB type liquid crystal display element, the liquid crystal molecules sealed between both glass substrates must be oriented substantially perpendicular to the glass substrate surface. This liquid crystal alignment characteristic is determined by the alignment control film 6 formed on the glass substrate surface facing the liquid crystal.
6'.

As a material for this alignment control film, a material having low surface energy, that is, having high water repellency is generally used. Various proposals have been made for this type of material. For example, inorganic oxides and fluorides 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 only on predetermined areas, so they contaminate the sealing area. This has the disadvantage of reducing seal strength. A water-repellent film such as silicone oil is also useful, but it is still difficult to prevent sealing from contamination.

Furthermore, an important characteristic of an alignment control film is that it must eliminate a phenomenon in which the electrode portions formed on the substrate appear more conspicuous than other areas (hereinafter referred to as "electrode visibility"). This is a problem that commonly occurs when conventional alignment control films are used. This problem can be solved by inserting a film that can eliminate the "electrode visibility" between the alignment control film and the substrate, but in that case, the film forming process will increase. , which will lead to an increase in costs.

The present invention has been made to overcome these drawbacks of the prior art, and its first purpose is to provide an alignment control film in which patterned electrodes become substantially inconspicuous. Second, it provides an alignment control film that has high heat resistance and can withstand the process of sealing with frit glass. Thirdly,
An object of the present invention is to provide an alignment control film material that allows an alignment control film to be provided only at any desired location without contaminating a sealing part. The present invention
The periphery of two transparent glass substrates having electrodes according to a desired display pattern is sealed with a sealing material,
A liquid crystal display element comprising a liquid crystal sealed between glass substrates, characterized in that an alignment control film made of a fluoroalkylsilane-modified silanol oligomer and a film-forming polymer substance is formed on the entire electrode surface. Related to display elements.

First, we selected a silanol oligomer with fluoroalkyl groups introduced into some of its side chains as a material for the alignment control film that basically has high heat resistance. Silanol oligomer is called SOG, and silicon oxide is produced by forming a coating film from a solution and then baking it at high temperature, and it is inherently highly heat resistant. In order to impart water repellency to this product, a fluoroalkyl group is introduced into the side chain.

The term "fluoroalkyl group" as used herein is a general term for alkyl groups that contain a perfluorocarbon group and may have other substituents. Therefore, for example, cases where a perfluorocarbon group is bonded to an alkyl group through a direct bond or via -O-, -COO-, etc. are included.

The fluoroalkyl group is bonded to silicon, and this bond is stronger than the bond between a normal unsubstituted alkyl group and silicon, and the bond does not break even when treated at high temperatures, and water repellency is maintained. This provides an alignment control film with high heat resistance.

Such a fluoroalkylsilane-modified silanol oligomer can be obtained by adding a silane having a fluoroalkyl group to a silanol oligomer solution and reacting the solution with stirring.

However, this alone cannot eliminate the "electrode visibility" problem, and furthermore, since the viscosity is low, local coating methods such as printing methods cannot be applied, and local film formation is difficult.

In order to solve this problem at the same time, we have found a method in which a highly viscous film-forming polymeric substance solution and a fluoroalkylsilane-modified silanol oligomer solution are mixed and applied.

If a material with high heat resistance and a high refractive index when formed into a mixed film is selected as the polymer substance, the effect will be significant.

For example, a polyimide-based polymer is a suitable material for the purpose of the present invention. Polyimide polymer materials generally have a higher refractive index than other polymer materials, and when mixed with fluoroalkylsilane-modified silanol oligomers, the refractive index of the film is high.
This was effective in eliminating the "electrode visibility" caused by the large difference in refractive index of the constituent materials.

However, the quality of heat resistance is not an essential condition for other purposes of the present invention, and even if heat resistance is not sufficient, polymeric substances with a high refractive index can be widely used. Examples of specific substances include aliphatic polyamide resin, aromatic polyamide resin, aromatic polyetheramide resin, polyamideimide resin, polyesterimide resin, polyhydrazidoimide resin, polybenzimidazole resin, polyamino bismaleimide resin, etc. It will be done.

Furthermore, other components may be added for the purpose of adjusting viscosity, improving adhesiveness, etc., to the extent that "electrode visibility" is not eliminated. In particular, cellulosic polymeric substances are useful for controlling viscosity.

The "electrode visibility" is explained by the specificity of reflection at the interface of media with greatly different refractive indices. One of the inventors of the present invention has clearly elucidated this problem and found that "electrode visibility" disappears when the refractive index of the film is 1.65 to 1.85. Therefore, an alignment control film whose refractive index is adjusted within this range is suitable for the purpose of the present invention.

The silanol oligomer in the present invention has the formula: (n is a number from 5 to 10) It is a silicone compound represented by:

This is manufactured, for example, as follows.

In a 200 ml flask equipped with a thermometer, stirrer, and condenser, add 20.5 ml of ethyl silicate Si (OC ₂ H ₆ ).
g, 37.4 g of ethanol, 14.4 g of ethyl acetate, 1.5 g of acetic anhydride, and 150 mg of phosphorus pentoxide were simultaneously charged.
The mixture is reacted at 70°C for 1.5 hours, and then 7 g of ion-exchanged water is added, and the mixture is reacted at 70°C for 1.5 hours to obtain a silanol oligomer solution.

Next, fluoroalkylsilane means a silane compound containing a fluoroalkyl group as defined above, and a typical one thereof is represented by the following general formula.

(Here, R _f is a perfluorocarbon group,
Z represents a direct bond or -O-, -COO-, X represents a lower alkyl group, Y represents a lower alkoxy group, p represents a number from 1 to 3, and q represents a number from 0 to 2).

Specific examples include the following compounds: The reaction process in which a fluoroalkylsilane-modified silanol oligomer is produced by reaction with a silanol oligomer is estimated to be as follows when schematically shown using 8D silane.

The above reaction progresses relatively easily, so
The reaction is completed by mixing and stirring at 70°C. The concentration of the fluoroalkyl group is determined by the blending ratio at the time of mixing, but in order to achieve vertical alignment, if it is bound to the silanol oligomer by about 10%, the objective can be achieved at the minimum. vice versa,
If the concentration of the fluoroalkyl group becomes too high, it will affect the stability of the liquid and may cause precipitation, so a range of 10 to 80% is appropriate. This corresponds to a ratio of the number of silicon in the silanol oligomer to the number of silicon in the fluoroalkylsilane of 20:1 to 1:1.

It has been found that oligomerization in this manner improves compatibility with the polymeric substance to be mixed, and also has the secondary effect of making it easier to create a uniform solution.

The blending ratio of the film-forming polymeric substance and the fluoroalkylsilane-modified silanol oligomer can be set to an arbitrary value. The blending ratio is determined so as not to make the content of fluoroalkyl groups extremely small and so that the refractive index of the mixed film meets the objective of the present invention.

In addition, the liquid crystal display element using the alignment control film according to the present invention can be improved by changing the liquid crystal to be sealed.
It can also be applied to other uses. For example, color display devices using guest-host liquid crystals doped with dichroic dyes, phase change display devices using cholesteric liquid crystals, display devices using smectic liquid crystals, and display devices using dynamic scattering effects.
It is also useful for DSM type display elements.

Hereinafter, the present invention will be specifically explained based on Examples.

In each example, the refractive index of the alignment control film was determined by forming a predetermined film on a silicon wafer and using an automatic ellipsometer AUTOEL manufactured by Rudolph Research.
- was used for measurement at a measurement wavelength of 6328 Å.

Example 1 A transparent electrode was formed on a soda glass substrate, and after patterning the transparent electrode into a predetermined shape by a predetermined process, an alignment control film was formed thereon. As the orientation control film, we used oligomerized 8D silane.
A mixture of 8D silane-modified silanol oligomer and polyimide resin (PIQ registered trademark, manufactured by Hitachi Chemical) was used.

8D silane-modified silanol oligomer is made by adding 8D silane to a 6% silanol oligomer solution using butyl cellosolve as a solvent, with a solid content concentration of 40% by weight.
% and reacted with stirring at 70°C for 2 hours.

Further, PIQ is a 3.5% by weight N-methyl-2-pyrrolidone solution. A mixed solution of both was prepared so that the weight ratio of solid content was 1:1.

The orientation control film formed in this way was heated to 450°C.
Up to this point, the ability to vertically align phenylcyclohexane liquid crystals (manufactured by Merck & Co., Ltd., ZLI-1132) was not lost. Further, there was no phenomenon in which the electrode pattern was noticeable.

However, if the composition of the fritted glass is, for example,
The basic composition is B ₂ O ₃ : 28 mol %, P ₂ O ₅ : 61 mol %, ZnO: 5 mol %, CuO: 5 mol %, Bi ₂ O ₃ : 1 mol %, and this basic composition is 100 parts by weight. for,
When using low melting point fritted glass, which is a mixture of 1.5 parts by weight of SiO ₂ and 2.0 parts by weight of Al ₂ O ₃ , the glass substrate 1
Seal 1'. In this case as well, a good alignment film was obtained in this example, and there was no "electrode visibility" at all.

Note that the refractive index of the alignment control film according to this example is:
It was 1.70.

Example 2 A 5.0% by weight dimethylformamide solution of aliphatic polyamide (Trogamid-T manufactured by Dynamite Nobel) was prepared, and the same 8D silane-modified silanol oligomer solution used in Example 1 was mixed in a solid content weight ratio of 1:1. 1 to form a solution, and an alignment control film was formed by spin coating. The refractive index of this film was 1.72.

Example 3 Polybutadiene (BC-1000 manufactured by Nippon Soda) 5
Create a wt% toluene solution and add the same 8D silane-modified silanol oligomer solution used in Example 1,
A solution was prepared by mixing at a solid content weight ratio of 1:1, and an alignment control film was formed by spin coating. The refractive index of this film was 1.65.

Example 4 2,2-bis[4-(4-aminophenoxy)
-Phenyl]-Propane and isophthalic acid chloride are reacted by a solution polymerization method to synthesize aromatic ether polyamide, and a 3.0% by weight solution of the same in dimethylformamide is prepared, which is then modified with the same 8D silane used in Example 1. a silanol oligomer solution,
A solution was prepared by mixing at a solid content weight ratio of 1:1, and an orientation control film was formed by spin coating. The refractive index of this film was 1.85.

Example 5 Isobutylene-maleic anhydride copolymer (Isoban-04 manufactured by Kuraray Isoprene Chemical)
A 5.0% by weight ethanol solution was prepared and mixed with the same 8D silane-modified silanol oligomer solution used in Example 1 at a solid content weight ratio of 1:1 to form a solution, and an alignment control film was prepared using a spin coating method. was formed. The refractive index of this film was 1.75.

Example 6 A 4D silane-modified silanol oligomer solution was prepared by the same method as described in Example 1, and mixed with the same aromatic ether polyamide solution used in Example 4 at a solid content weight ratio of 1:1. A solution was prepared and an orientation control film was formed by spin coating. The refractive index of this film was 1.85.

Using the substrates provided with the alignment control films of Examples 2 to 6, each was sealed with an epoxy adhesive and injected with ZLI-1132 to produce a liquid crystal display element as shown in the attached drawings. All of these devices showed good vertical alignment and no "electrode visibility" at all.

Examples 7 to 11 Using the same method as described in Example 1, a 4T silane-modified silanol oligomer solution (Example 7),
8T silane-modified silanol oligomer solution (Example 8), 4FD silane-modified silanol oligomer solution (Example 9), 14T silane-modified silanol oligomer solution (Example 10), and 14D silane-modified silanol oligomer solution (Example 11) were produced. Ivy. Each of these was mixed with the same PIQ used in Example 1 at a solid content weight ratio of 1:1 to prepare a solution, and an alignment control film was prepared. Using these substrates, each was sealed with low-melting fritted glass and injected with ZLI-1132 to create a liquid crystal display element. All of these exhibited good vertical alignment, and there was no "electrode visibility" at all. In addition,
The refractive index of each film was 1.65 (Example 7), 1.70 (Example 8), 1.70 (Example 9), 1.70 (Example 10), and 1.68 (Example 11).

Comparative Example 1 Using the same 8D silane-modified silanol oligomer solution as used in Example 1, an alignment control film was formed by spin coating. Using these substrates, they were sealed with low-melting frit glass and injected with ZLI-1132 to create a liquid crystal display element. This device showed good vertical alignment, but the electrode pattern was noticeable. Note that the refractive index of this film was 1.52.

Comparative Example 2 An alignment control film was formed using a 20% ethanol solution of 8D silane. Using this, we sealed it with epoxy adhesive and injected ZLI-1132 to create a liquid crystal display element. This device showed good vertical alignment, but the electrode pattern was noticeable.

The refractive index of this film was not measurable.

Comparative Example 3 A substrate with the same alignment control film as in Comparative Example 2 was used, but it was sealed with low melting point fritted glass and ZLI-
1132 was injected to create a liquid crystal display element. This device did not exhibit a uniform vertical alignment, but rather a random alignment.

As is clear from the above examples and comparative examples,
A liquid crystal display element using the alignment control film according to the present invention exhibits good vertical alignment and has high heat resistance.
Both organic adhesive seals and glass frit seals are applicable and are of good quality with inconspicuous electrode patterns.

[Brief explanation of the drawing]

The accompanying drawing is a sectional view showing an example of a liquid crystal display element used in the present invention. 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. Having electrodes according to a desired display pattern. 2.
In a liquid crystal display element in which the periphery of two transparent glass substrates is sealed with a sealant and a liquid crystal is sealed between the glass substrates, the entire electrode surface is coated with a fluoroalkylsilane-modified silanol oligomer and a film-forming polymer substance. A liquid crystal display element comprising an alignment control film formed thereon. 2. The refractive index of the alignment control film is 1.65 to 1.85.
A liquid crystal display element according to claim 1. 3. The liquid crystal display element according to claim 1, wherein the alignment control film is provided with wear grooves in a certain direction. 4. The liquid crystal display element according to claim 1, wherein the sealing material is made of glass frit. 5. The liquid crystal display element according to claim 1, wherein the sealing material is made of an organic adhesive.