JPS6220530B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-optical electrode substrate. For details, please refer to the field effect twist type (hereinafter referred to as FETN).
The present invention relates to an electro-optic electrode substrate used in a liquid crystal display element (referred to as a type).

[Conventional technology]

FETN type liquid crystal display elements are made by aligning a nematic liquid crystal compound with positive dielectric anisotropy parallel to the substrate.
Obtained by imparting optical rotation. this
The operating principle of FETN display elements is to control or rearrange the initial alignment of liquid crystals using an electric field and to utilize the changes in optical properties at that time.
The uniformity of the initial alignment of the liquid crystal is particularly important.

Conventionally, a method of rubbing an electrode substrate in one direction with cloth or the like has been known as a means of imparting initial orientation to liquid crystal.

[Problem that the invention seeks to solve]

However, in the above method, the orientation of the liquid crystal molecules is partially different, and the uniformity of the orientation is not sufficient, and there is a drawback that the orientation is lost within a short time. In order to improve the above-mentioned drawbacks, a method has been used in which a certain type of surfactant is used in combination to rub the electrode base material in one direction. However, although this method improves the uniformity of alignment to some extent, it has the disadvantage that the surfactant has no heat resistance and that the surfactant causes deterioration of the liquid crystal. Furthermore, if the electric field is continuously applied, the surfactant is decomposed and altered by the electric field, resulting in destruction of the orientation. In addition, the liquid crystal deteriorates and decomposes due to charge injection from the electrode surface due to the application of an electric field, and furthermore, the electrode surface is electrochemically reduced by trace amounts of moisture in the liquid crystal, causing deterioration.
This results in destruction of orientation. Further, the above-described deterioration of the electrode surface also occurs due to a small amount of moisture entering from the outside of the electro-optic cell. Furthermore, when producing an electro-optic cell after aligning the electrode substrates, if an inorganic material such as glass frit or an organic material with a high curing temperature is used as a sealing material to bond a pair of electrode substrates, the heating temperature during sealing may , there is also a drawback that orientation destruction occurs.

[Means for solving problems]

As a result of research into improving the various drawbacks described above, the present inventors found that by providing an oriented polyimide polymer coating on the electrode-containing surface of the electrode substrate, a highly durable, heat-resistant, and extremely We have found that it is possible to obtain excellent initial alignment uniformity of liquid crystals.

However, in a configuration in which the electrode is covered with a single layer of polyimide polymer film, the
High durability that can withstand long-term continuous electric field application at RH) cannot be achieved.

An attempt was made to increase the charge blocking effect by increasing the thickness of the polyimide polymer coating, prevent charge injection into the liquid crystal, and thereby increase cell life, but the thickness of the polyimide polymer coating As the thickness increases, it becomes more difficult to apply uniformly, resulting in non-uniform display and a decrease in electrical response, making it difficult to obtain desirable results.

Furthermore, as a result of extensive research, we found that by forming a polyorganosilane film on the glass substrate before forming the polyimide polymer film, and then providing a polyimide polymer film on top of that, the reduction in electrical response and non-uniform display could be reduced. It was discovered that the life of the cell can be increased to the extent that it can withstand continuous electric field application for a long time under high humidity without causing any damage, and the present invention was completed based on this knowledge.

That is, the present invention provides an electro-optical electrode substrate constituting an electro-optic cell for a liquid crystal display, which has a polyorganosilane coating on the surface of the substrate provided with the electrode coating, and further has a polyorganosilane coating on the polyorganosilane coating. This is an electro-optical electrode substrate characterized by having an oriented polyimide polymer coating.

Next, the above invention will be explained in detail.

First, the electro-optical electrode substrate of the present invention will be explained using the drawings. The drawing is a cross-sectional view schematically showing the electro-optical electrode substrate of the present invention, in which an electrode coating 2 is provided on a substrate 1 that can be used as an electro-optic electrode substrate, and the substrate surface including the electrode coating 2 is A polyorganosilane coating 3 and an oriented polyimide polymer coating 4 are provided thereon.

The above-mentioned substrate is made of an insulating and transparent material such as glass or plastic, and a transparent electrode film is provided on this substrate by a conventional method. For example, a transparent conductive film containing tin oxide, indium oxide, etc. as a main component can be provided by a spraying method, a vacuum evaporation method, etc., and these electrode films can be formed into a predetermined pattern, for example one or more, by means such as photo etching. It is used by processing it into individual numbers, letters, or graphic patterns.

Next, to form a polyorganosilane coating on the substrate surface containing the electrode coating, an organosilane monomer or prepolymer is dissolved in a solvent such as n-hexane, benzene, toluene, or xylene.
A solution having a concentration of 0.1 to 20% is prepared, this solution is applied to the surface of the electrode substrate, and heated or heated by infrared ray irradiation to polymerize the organosilane and evaporate the solvent to dryness. This polyorganosilane coating is used in a thickness of 0.01 to 100μ, particularly preferably 0.1 to 20μ. If the film thickness is less than 0.1μ, the effect of providing the film will be weak and will not increase the life of the electro-optic cell, and if it is thicker than 100μ, it will be difficult to apply uniformly, and the contrast and response of the cell will be poor, which is undesirable. .

Here, organosilane has the general formula RnSiX4-n
It is one type or a mixture of two or more types of organosilanes represented by (n=1, 2, 3). In the formula, X
is, for example, a halogen group such as chlorine, or an alkoxy group such as a methoxy group or an ethoxy group, or also an acyloxy group such as an acetoxy group, or other hydrolyzable functional groups. In the formula, R is a saturated aliphatic hydrocarbon group such as a methyl group or an ethyl group, or an unsaturated aliphatic hydrocarbon group such as a vinyl group or an alkenyl group, or an aromatic hydrocarbon group such as a phenyl group; The hydrogen group may be substituted with an unsaturated group such as a vinyl group or an alkenyl group, or a hydroxyl group, a carbonyl group, or a halogen group such as chlorine, bromine, or fluorine, or other functional organic group. Examples include chloromethyl group, 8,8,8-trifluoropropyl group, and 8-aminopropyl group.
In the above, (4-n) X's and n R's may be the same type or different types.

Further, as a method for applying the above-mentioned organosilane solution to the electrode substrate, a conventional application method such as a spin coating method, a dipping method, or a spraying method can be used.

The polyorganosilane coating described above is recognized to have a property of aligning an electro-optic substance having positive dielectric anisotropy, such as liquid crystal molecules, perpendicularly to the electrode substrate.
When a pair of electrode substrates on which the film is rubbed with cloth, cotton, etc. are sandwiched between the two electrode substrates so that their orientation treatment directions intersect,
The electro-optic material has a left-handed helical structure and a right-handed helical structure, and both types coexist. Moreover, economically, the horizontal alignment is destroyed, and finally the vertical alignment occurs. Therefore, in order to regulate the direction of helical rotation and obtain economically stable horizontal orientation, in the present invention, an oriented polyimide polymer film is further provided on the organosilane film.

Next, in the present invention, a polyimide polymer coating is provided on the polyorganosilane coating. As the polyimide polymer, polyimide composed of imide bonds, polyamideimide composed of amide bonds and imide bonds, polyesterimide composed of ester bonds and imide bonds, etc. are used.

The polyimide polymer has an imide bond,
Generally, it is insoluble in solvents, so in order to provide a polyimide polymer film on a substrate in the present invention, polyamic acid is dissolved in the solvent described below and applied on the substrate, and then heat treatment is performed to dehydrate and ring-close it to form an imide bond. It is preferable to have

Polyamic acid, which is a precursor of the polyamideimide, is synthesized by condensation of polygodiamine obtained from excess diamine and dicarboxylic acid anhydride.

Polyamic acid, which is a precursor of the polyesterimide, is synthesized by condensation of a dicarboxylic anhydride having an ester group and a diamine.

The above dicarboxylic acid anhydride having an ester group can be obtained, for example, from trimellitic acid and various diols.

Further, polyamic acid, which is a precursor of the polyimide, is synthesized by condensation of dicarboxylic acid and diamine. These condensation reactions are carried out under conventional conditions, ie, under anhydrous conditions and at temperatures of 50°C or lower.

Examples of diamines mentioned above include m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and m-phenylenediamine.
xylene diamine, p-xylene diamine, 4,
4'-Diamine diphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,
4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'diaminodiphenylmethane, 3,3',
5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 2,2'-bis(4-aminophenyl)propane-4,4'-methylene dianiline, benzidine, 4,4'-diaminodiphenyl Nyl sulfide, 4,4'-diaminodiphenylsulfone, 1,
5-diaminonaphthalene, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,4
-bis(β-amino-tert-butyl)toluene,
Bis(4-β-amino-tert-butylphenyl)
Ether, 1,4-bis(2-methyl-4-aminobentyl)benzene, etc. are used.

In the above, the diols include hydroquinone, bisphenol A, dichlorobisphenol A, tetrachlorbisphenol A, tetraprombisphenol A, bisphenol F, and bisphenol.
ACP, bisphenol L, bisphenol V,
Bisphenol S, 4,4'-dihydrophenyl ether, etc. are used.

In addition, the dicarboxylic anhydride mentioned above includes pyromellitic anhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 3,3',4,4'-diphenyltetracarboxylic anhydride, 1, 2, 5, 6
-Naphthalenetetracarboxylic anhydride, 2,2',
3,3'-diphenyltetracarboxylic anhydride, thiophene-2,3,4,5-tetracarboxylic anhydride, 2,2-bis(3,4-biscarboxyphenyl)propane anhydride, 3, 4-dicarboxyphenylsulfone anhydride, perylene-3,4,
9,10-tetracarboxylic anhydride, bis(3,4
-dicarboxyphenyl)ether anhydride, 3,
3′4,4′-benzophenonetetracarboxylic acid anhydride and the like are used.

The above diamines, diols and dicarboxylic acid anhydrides are all preferably aromatic compounds from the viewpoint of heat resistance.

To apply polyamic acid onto a substrate, polyamic acid is dissolved in a solvent such as dimethyl formamide, dimethyl acetamide, dimethyl threfoxide, or N-methylpyrrolidone at a concentration of 0.01 to 40%.
The solution can be applied by brush coating, dipping, spin coating, spraying, or the like. After application, 100℃~350℃, preferably 200℃~
Heat treatment is performed at 300°C and dried to form a polyimide polymer film on the polyorganosilane film.

This polyimide polymer coating is used in a thickness of 0.01 to 50μ, particularly preferably 0.1 to 5μ. If the film thickness is less than 0.01 μm, the effect of providing the film will be weak, and sufficient liquid crystal alignment power or heat resistance will not be obtained. If it is thicker than 50 μm, it will be difficult to apply uniformly, and the contrast of the cell and The response is poor and undesirable.

To orient the polyimide polymer coating, a method of rubbing in a certain direction with a cloth, brush, etc. is used.

In the above, the polyorganosilane and polyimide polymer coatings are provided at least on the portions that come into contact with the liquid crystal, excluding the electrode terminal extraction portions.

[Effect]

The polyorganosilane coating previously provided before the polyimide polymer coating prevents charge from being injected into the liquid crystal from the electrode portions, reducing power consumption and increasing cell life.

In the present invention, there is no decrease in electrical response or non-uniform display because the polyorganosilane coating adheres sufficiently to both the polyimide, the glass, and the electrodes, and the polyorganosilane coating and polyimide polymer coating are bonded together. This is thought to be because it can be formed to have a uniform thickness.

Next, the polyimide-based polymer coating subjected to alignment treatment serves the function of aligning the liquid crystal.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 A glass plate for an electrode substrate on which indium oxide was vapor-deposited was immersed in a 1-10% toluene solution of diethoxydimethylsilane, heated at 80° C. for 30 minutes to polymerize, and then dried.

Next, in a 2% dimethylacetamide solution of polyamic acid, which is a precursor of polyesterimide obtained by condensing an aromatic dicarboxylic anhydride obtained from trimetic acid and hydroquinone, and 4,4'-diaminodiphenyl ether, The above electrode substrate was immersed. After dipping, heat treatment was performed at 200° C. for 1 hour to cause dehydration and ring closure, and a polyesterimide polymer coating was provided on the polyorganosilane coating.

Next, the surface of the polymer coating was rubbed in one direction with a cloth for orientation treatment to produce an electrode substrate of the present invention.

An electro-optic cell and a display device were manufactured using the pair of electrode substrates described above as follows. A hot melt type nylon film with a thickness of 30 μm was interposed in the sealing part of the electrode substrate, and the pair of electrode substrates facing each other was adhesively fixed using a heat-press bonding method so that the direction of orientation treatment was 90 degrees. After that, 50 parts of p-methoxybenzylidene-p'-n-butylaniline and 50 parts of p-ethoxybenzylidene-p'-n-butylaniline were added through the previously provided sealing port.
A mixed nematic liquid crystal having positive dielectric anisotropy consisting of 5 parts of p-m-propylbenzylidene-p'-cyanoaniline was sealed, and the holes were sealed with epoxy resin to produce an electro-optic cell. Furthermore, a display device was manufactured by pasting linearly polarizing plates on both sides of the outside of the cell so that the polarization directions of the light plates were parallel to the rubbing direction of the adjacent substrates.The display device has excellent durability. Moreover, no destruction of orientation was observed even after being left at 80°C for 4 weeks, indicating excellent heat resistance.
Furthermore, the uniformity of orientation was also good. It also showed a significant increase in durability, being able to withstand continuous application for long periods of time under high humidity conditions (30°C, 90% RH).
That is, when a 6V (effective value), 32Hz sine wave was applied for 1000 hours, the increase in the alternating current value was less than double in this example.

On the other hand, when an electrode substrate manufactured in the same manner as in this example without providing a polyorganosilane coating was used, the above increase was 2 to 4.
It was twice as hot.

Example 2 A 1-10% toluene solution of dimethyldichlorosilane was applied by spraying to a glass plate for an electrode substrate on which tin oxide had been vapor-deposited, and then heated at 80°C for 30 minutes to polymerize and further dried. .

Next, N-N'-bis(3-aminophenyl)
A 1% dimethylacetamide solution of polyamic acid, which is a precursor of polyamideimide obtained by condensing isophthalamide and pyromellitic anhydride, was applied by spin coating, and heat treated at 250°C for 20 minutes to cause dehydration and ring closure. A polyamideimide polymer coating was provided on the polyorganosilane coating.

Next, the surface of the polymer coating was rubbed in one direction with a cloth for orientation treatment to produce an electrode substrate of the present invention.

Using the pair of electrode substrates described above, an electro-optical cell and further a display device were manufactured as follows.

A hot melt type polyester film having a thickness of 20 μm was interposed in the sealing portion of the substrate, and the pair of electrode substrates were bonded and fixed by thermocompression bonding with the electrode substrates facing each other so that their orientation directions were at 90 degrees to each other. After that, 40 parts of p-methoxybenzylidene-p'-n-butylaniline and p-ethoxybenzylidene-
A mixed nematic liquid crystal with positive dielectric anisotropy consisting of 60 parts of p'-n-butylaniline and 10 parts of p-butoxybenzoic acid-p'-cyanophenyl ester was filled in, and the hole was sealed with epoxy resin. , manufactured an electro-optic cell.

Next, a display device was produced in the same manner as in Example 1. The display device had excellent durability, and no destruction of orientation was observed even after being left at 80° C. for 4 weeks, and this orientation effect was not lost even after heat treatment at 300° C., indicating excellent heat resistance. Furthermore, the uniformity of orientation was also good. The durability under high humidity was also excellent as in Example 1.

Example 3 Electrode substrate glass on which tin oxide was vapor-deposited was immersed in a 1-10% toluene solution of diethoxydiphenylsilane, and heated at 80°C for 30 minutes to polymerize it.
It was further dried. Next, the electrode substrate was immersed in a 1% N-methylpyrrolidone solution of polyamic acid, which is a precursor of polyimide obtained by condensing pyromellitic anhydride and 4,4'-diaminodiphenyl ether. After dipping, heat treatment was performed at 200° C. for 30 minutes to cause dehydration and ring closure, and a polyimide polymer coating was provided on the polyorganosilane coating. Next, the surface of the polymer coating was rubbed in one direction with a cloth for orientation treatment to produce an electrode substrate of the present invention.

Using the pair of electrode substrates described above, an electro-optical cell and further a display device were manufactured as follows. A thermosetting acrylic resin was printed on the seal portion of the electrode substrate by screen printing, and the pair of electrode substrates were placed facing each other so that the directions of the alignment process were at 90 degrees to each other, and then bonded together by thermocompression bonding. After that, p-methoxybenzylidene-
30 parts p'-n-butylaniline, 50 parts p-ethoxybenzylidene-p'-n-butylaniline, p-methoxybenzylidene-p'-n-heptylaniline
10 parts, p-propoxybenzylidene-p'-n-heptylaniline 10 parts, p-butoxybenzoic acid-
A mixed nematic liquid crystal with positive dielectric anisotropy consisting of 20 parts of p'-cyanophenyl ether is enclosed,
The holes were sealed with epoxy resin to produce an electro-optic cell. Next, a display device was produced in the same manner as in Example 1. The display device has excellent durability and can withstand temperatures up to 80℃.
Even after being left for 4 weeks, no destruction of orientation was observed, and the film had excellent heat resistance. Furthermore, the uniformity of orientation was also good. The durability under high humidity was also excellent as in Example 1.

Example 4 A 1 to 10% solution of methyltriethoxysilane/dimethyldiethoxysilane (=1/1) in benzene was applied by spraying to a glass plate for an electrode substrate on which indium oxide was vapor-deposited, and then heated at 80°C for 30 minutes. It was heated to polymerize and then dried. Next, in the same manner as in Example 3, a polyimide polymer film was provided on the polyorganosilane film. Next, the surface of the polymer coating was rubbed in one direction with a brush for orientation treatment to produce an electrode substrate of the present invention.

Using the pair of electrode substrates described above, an electro-optical cell and further a display device were manufactured as follows. resin 100
A thermosetting acrylic ink mixed with 200 parts of anhydrous copper sulfate was silk screen printed on the sealing part of the electrode substrate, so that the directions of the orientation treatment of the pair of electrode substrates were (a) 38 degrees and (b) They were placed facing each other at an angle of 45 degrees and (c) 52 degrees, and were fixed by heat bonding. After that, p-methoxybenzylidene-p′-n-butylaniline 20
parts, p-ethoxybenzylidene-p'-n-butylaniline 40 parts, n-hexyloxybenzylidene-
40 parts of p'-n-butylaniline, 15 parts of P-n-butoxyphenyl-p'-cyanobenzoate, p-n
A mixed nematic liquid crystal consisting of 15 parts of -hebutyroxyphenyl-p'-cyanobenzoate was inserted and the holes were sealed to produce three types of electro-optic cells. Next, three types of display devices were manufactured in the same manner as in Example 1. All of these display devices had no uneven orientation and were excellent in high-temperature durability.

Furthermore, in all of these display devices, the hue of the image area is black when an electric field is applied, and the non-image area is transparent with no interference fringes, so the contrast of the image area as a display body is extremely good, and the contrast of the liquid crystal molecules is very high. The response speed of rise and fall was fast, and the light image did not flicker, making it extremely excellent. The durability under high humidity was also excellent as in Example 1.

Comparative Example After cleaning a glass plate for an electrode substrate on which indium oxide was vapor-deposited, a 0.5% aqueous solution of polyoxyethylene nonyl phenyl ether was applied as an alignment treatment agent by immersion, and then dried under vacuum and heat.

Next, the coated surface was rubbed in one direction with a cloth to prepare an electrode substrate.

A display device was produced in the same manner as in Example 1 using the pair of electrode substrates described above. This display device has uneven orientation of brightness and darkness in the display area when an electric field is applied, and
After 100 hours at 60°C, the orientation was destroyed and the durability was poor. Furthermore, after continuous application under high humidity conditions similar to Example 1, the increase in alternating current was about 5 times.

〔Effect of the invention〕

In the electro-optical electrode substrate of the present invention, since the polyorganosilane coating is water repellent and insulating, there is no charge injection from the electrode part, power consumption is reduced, and the liquid crystal and alignment agent do not change in quality. Can withstand continuous voltage application for long periods of time. In addition, since the present invention uses a polyimide polymer as an alignment agent, the initial alignment of electro-optical materials such as liquid crystals is extremely uniform, and the polyimide polymer coating has excellent heat resistance. Inorganic sealing using glass frit is also possible, and even if the temperature of the electrode substrate increases, it does not affect the alignment of electro-optic materials such as liquid crystal.
This has the advantage that the molecules of electro-optical substances such as liquid crystals in the cell remain stable for a long time.

In addition, even though the polyorganosilane coating and polyimide polymer coating are laminated, it shows an appropriate electrical response, and the polyimide polymer coating can be formed uniformly, resulting in excellent display uniformity. It is.

An electro-optic material having a positive dielectric anisotropy as a whole between a pair of electrode substrates according to the present invention with the polyimide polymer coating surface facing each other so that their alignment treatment directions intersect. ,
For example, an electro-optic cell can be produced by sealing a nematic liquid crystal using a known method, and by combining the cell with a polarizer such as a linear polarizing plate or a circular polarizing plate, or a reflecting plate, a display device can be produced. Configure.

Such an electrode substrate can be effectively used in various electro-optical devices, and is used, for example, in display devices such as electronic desktop calculators, wristwatches, table clocks, and count display boards.

[Brief explanation of the drawing]

The drawing is a sectional view schematically showing an electro-optical electrode substrate of the present invention. Explanation of the symbols representing the main parts of the figure: 1...Substrate, 2...Electrode coating, 3...Polyorganosilane coating, 4...Oriented polyimide polymer coating.

Claims (1)

[Claims] 1. In an electro-optical electrode substrate constituting an electro-optic cell for a liquid crystal display, a polyorganosilane coating is provided on the surface of the substrate provided with the electrode coating, and the polyorganosilane coating is further subjected to alignment treatment. An electro-optical electrode substrate characterized by having a polyimide polymer coating.