JPH01925A - Spacer for liquid crystal element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spacer used in a display element using liquid crystal such as a liquid crystal television. More specifically, the present invention relates to a spacer using carbon fiber-based fibers.

[Prior Art] Recently, liquid crystal displays have replaced displays such as cathode ray tubes (CRTs) in pocket TVs, wall-mounted TVs, personal computer terminals, word processor displays, IC card displays, dimming glasses, sunglasses, etc. It began to be used for eyeglasses, etc.

A liquid crystal electro-optical element is constructed by arranging two substrates facing each other at a regular interval, each consisting of a transparent electrode film for driving and an alignment film for aligning liquid crystal molecules formed on the surface of a glass plate, and filling the gap with liquid crystal. has been done.

As the gap control material (spacer), glass fibers, ceramic particles such as alumina, inorganic particles such as silica, and polymer particles such as crosslinked polystyrene and crosslinked epoxy resin are used.

However, since ceramic particles such as glass fiber and alumina are made of inorganic materials, they have high hardness, and conductive films (mainly indium oxide-tin oxide vapor deposited films, hereinafter referred to as ITO films) formed on glass substrates during cell assembly, This method has disadvantages of damaging functional films such as alignment films and whitening of images. Further, fine polymer particles such as cross-linked polystyrene also have the disadvantage of whitening of images because it is difficult to color them, particularly to darkly color them. Furthermore, even if fine particles are classified, it is difficult to obtain particles with a uniform diameter.

A fundamental problem is that if the particle diameter is not accurate, the alignment of the liquid crystal is disturbed and the image quality is degraded.

Further, in the above, there is a problem that when the image becomes white, the contrast ratio decreases and the sharpness decreases.

As a known example similar to the present invention, an example in which plastic particles are colored has been proposed (Japanese Unexamined Patent Publication No. 57-1891
No. 17), but lacks specificity, and there is no one that has been put into practical use yet.

[Problems to be Solved by the Invention] In order to improve the above-mentioned problems of the prior art, the present invention provides a spacer with a uniform particle size by using carbon fibers cut into short lengths, and at the same time provides a spacer with a dark color. To provide a technology that improves the clarity of a display image by chromatography, does not damage a functional film in contact with a spacer, and makes the spacer at low cost.

[Means for solving problems] In order to achieve the above object, the present invention consists of the following configuration.

[A spacer used in a liquid crystal element in which a constant distance is maintained between opposing substrates and a liquid crystal is sealed inside, the spacer is a fiber made of carbon fiber, and the cross-sectional shape of the fiber is substantially round, A spacer for liquid crystal elements that is cut short in the length direction. In the present invention, the use of carbon-based fibers is firstly advantageous in that the fiber diameters are uniform, so that the spacing can be very precisely determined.

Second, when assembling a liquid crystal cell, the periphery of the two substrates is sealed with an epoxy sealant, but at this time, heat and pressure bonding (cure) is applied at temperatures of 100°C or higher, sometimes around 200°C. ) process. Therefore, it is necessary that the fibers do not undergo thermal deformation during this heating and pressure treatment, and the carbon fibers of the present invention can sufficiently withstand such conditions.

Thirdly, the carbon fiber used in the present invention has a black color inherent to carbon, and is not dyed or colored with pigments.
It is stable in that the color does not elute into liquid crystals, etc.

Fourth, when assembling a cell, if the two substrates are pressurized to a certain extent to keep the cell gap at a constant distance, the carbon fibers used in the present invention do not damage the ITOv or alignment film formed on the substrates. There are advantages.

Other features include low water absorption and excellent dimensional stability.
Advantages include excellent heat resistance and chemical resistance, stability even when in contact with liquid crystals, excellent durability, and relatively low cost.

Next, the thickness of the spacer of the present invention is preferably selected from the range of 1 to 30 μm. The reason for this is that the thickness of g & miscellaneous determines the cell gap.

For example, in the case of a display using ferroelectric liquid crystal (SMC), the spacing between the substrates is approximately 2 μm, so the spacing between the substrates is preferably about 2±0.1 μm.

In the case of TPT (thin film 1 helangister) type display bodies and SBE (super brief fringe effect, new TN liquid crystal) type displays, it varies depending on the type of liquid crystal used, but the thickness is approximately 2 to 20 μm. It's the thickness. In this case as well, the range of variation in fiber thickness is ±
The thickness is preferably about 0.1 μm.

Control of the thickness of these fibers is determined by the diameter of the spinneret hole and the take-up speed during spinning. It is necessary to determine the thickness by taking into account the amount of weight loss due to subsequent steps of stretching, flame resistance, and firing. As a multifilament, unevenness in thickness tends to occur between filaments, so it is preferable to take as few filaments as possible or to spin monofilaments.

Any material may be used as the raw material for the carbon fiber. For example, polyacrylonitrile (PAN), rayon, polyvinyl alcohol, polyacetylene, lignin,
These include pitches such as poval, 'niyno l°' (trade name), aramid, polyamide, polyimide, petroleum and coal, and benzene.

The carbon-based m-fiber in the present invention refers to flame-resistant fiber, carbon fiber, graphitized fiber, and the like. Here, the flame-resistant fiber is, for example, PAN oxidized at about 150 to 300°C, and is also referred to as stabilized fiber or infusible fiber. Carbon fiber is obtained by firing the above-mentioned flame-resistant fiber in an inert air stream at, for example, about 900 to 1500°C. Graphitized fiber is obtained by firing the above-mentioned carbon fiber at about 2000 to 3000°C.

A detailed explanation of the carbon-based fiber itself is given in, for example, "Carbon Fiber" by Sugibe Otani et al. (Kinda Editorial Co., Ltd., published on July 1, 1980), so I will leave it to you here.

The length of the synthetic 9aM is preferably selected from a range of 1 to 100 μm. This is because if the length is too long, the quality of the image will deteriorate. Preferably it is about 20 to 40 μm.

In order to obtain fibers of these lengths, a large number of carbon fibers are arranged, embedded in resin, and cut together with the resin using a microtome (fine section cutting machine), NC precision lathe, etc.
There is a method of removing the embedded resin after that. Another means is freeze-grinding. Freeze pulverization involves pulverizing in a mill or the like using a refrigerant such as liquid nitrogen.

A particularly preferred method is to embed it in resin and cut it. This is because, in addition to being able to obtain a product with a uniform length, the cut end surface is also uniform compared to the pulverization method. If this method is used, there is no need for classification treatment in subsequent steps. Removal of the embedded resin can be easily done by simply soaking it in a solvent if the relationship between the resin and the solvent is selected appropriately, and at this time, it is also possible to remove debris with high specific gravity, such as metal.

In the pulverization method, it is preferable to classify in order to collect particles of uniform length. Classification may be carried out using any known means such as wind sieve or water sieve.

In the present invention, the surface of the spacer may be coated with a resin. In this way, the ITO film, surface alignment film, etc. can be made less likely to be damaged. Further, it is more preferable if this resin has an adhesive function, since an adhesive to be described in detail is not necessary.

The spacer made of carbon fiber of the present invention is disclosed in Japanese Patent Application No. 61
-219273 and patent application 1986-1219274@
It may also be used in combination with the epoxy adhesive particles proposed in . In this case, it is preferable that the adhesive particles are also colored.

The method of using the spacer of the present invention is as follows:
．． Preferably, it is present in a range of 0.01 to 50 mg.

Roughly preferably about 10 pieces per 1 mm.

As described above, the spacer of the present invention is SMO, SBE, T
In addition to PT, it is effective for any liquid crystal display using normal TN liquid crystal, guest-host type liquid crystal, etc. The display may be of any type, including a pocket television, a wall-mounted television, a personal computer terminal, a word processor display, a liquid crystal shutter, and a display for vehicles such as automobiles.

[Example] Example 1 PAN-based carbon fiber III (“Trading Card” manufactured by Toshi Co., Ltd. (registered trademark > T-300, single fiber thickness 7 μm) was used at 10.0 μm.
00 pieces were aligned in one direction, placed in a mold, n-butyl methacrylate (containing 1.5% benzoyl peroxide) was injected into the mold, and cast polymerization was performed at 50°C for 24 hours. . Remove the appropriate welding mold, and carbon l! Only the part where the fibers were embedded in resin was cut out using a hacksaw. Next, this resin-embedded body was force-tested using a microtome (manufactured by Nippon Microtome Kenkyushin).That is, the resin-embedded body was held in a holder and moved up and down, and the fixed yttrium
20 using a zirconia ceramic knife (leather blade)
It was cut to a μm diameter.

After cutting, the resin was dissolved with acetone, and the target carbon fiber cut (spacer) was taken out.

The obtained spacer had no miscut parts, was substantially cylindrical, and had a uniform fiber diameter, making it ideal.

Next, a glass substrate (10
cm x 10 cm), apply an epoxy resin adhesive liquid to a thickness of about 9 μm to form a sealing part, and apply the above spacer to a thickness of 1 mm2 on the inside part (image display part).
Approximately 10 pieces were distributed and distributed. The dispersion was uniformly cast together with the dispersion solution using Freon. Next, heat press to 18
A cell was formed by heating and pressurizing at 0° C. for 1 hour. The thickness of the obtained cell was 7 μm and was almost uniform.

SEE liquid crystal was sealed in this cell gap to form a panel. No whitening points were visible in the resulting panel image, and the contrast ratio was excellent.

Example 2 Flame-resistant synthetic fiber If which is a precursor of carbon fiber used in Example 1
f (fiber diameter 8.5 μm), approximately 500,000 fibers were
The length and width of approximately 5QCIII are aligned, and an acetone solution of poly(n-butyl methacrylate) is sprayed onto this to form a prepreg.
wrapped around a metal rod. Next, this cylindrical object with a diameter of 10CIII was placed in a cylindrical mold, and n-butyl methacrylate (containing 1.5% benzoyl peroxide) was injected into the mold and heated at 50°C for 24 hours. Cast polymerization was carried out. After that, the mold was removed, the resin embedding body was taken out, and the embedding body was cut into a length of 20 μm from the circumferential direction using an NC precision lathe.
It was cut with a thickness of 1 mm. The tool bit was made of diamond. The rotation speed of the cylinder is 5 orpm,
Cutting was performed at a feed rate of the cutter of 1 mm/min.

The resin was dissolved in acetone, and the desired flame-resistant fiber cuts (spacers) were taken out.

The obtained spacer had no miscuts, had a substantially cylindrical shape, and had a uniform fiber diameter, and was as excellent as Example 1.

[Effects of the Invention] As explained above, according to the present invention, by using a carbon fiber cut short as a spacer in the intended gap between two substrates, a good contrast ratio can be obtained. We were able to provide a technology to produce spacers that look good, do not damage the functional membranes they come into contact with, and have uniform particle sizes at a low cost.

Claims (6)

[Claims] (1) In a spacer used in a liquid crystal element that maintains a constant distance between opposing substrates and encapsulates a liquid crystal inside, the spacer is a fiber made of carbon fiber, and the fiber cross-sectional shape is substantially A spacer for liquid crystal elements characterized by a round shape cut short in the length direction. (2) A spacer for a liquid crystal element according to claim (1), wherein the fiber thickness is selected from a range of 1 to 30 μm. (3) A spacer for a liquid crystal element according to claim (1), wherein the fiber length is selected from a range of 1 to 100 μm. (4) A spacer for a liquid crystal element according to claim (1), wherein the fibers are cut by cutting with a knife or by pulverization. (5) A spacer for a liquid crystal element according to claim (1), wherein the surface of the fiber is coated with a resin component. (6) A spacer for a liquid crystal element according to claim (5), wherein the resin component on the surface is an adhesive.