JP2807475B2 - Powder dispersing method, substrate with powder and liquid crystal cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for uniformly dispersing a powder on a substrate. The present invention also relates to a powdered substrate in which powder is dispersed at a uniform density per unit area on a substrate by the above method, and particularly to a transparent electrode substrate in which powder is dispersed at a uniform density per unit area. Furthermore, the present invention relates to a liquid crystal display cell having a uniform liquid crystal phase obtained by using a transparent electrode substrate in which the powder is dispersed at a uniform density per unit area.

2. Technical Background of the Invention and Problems Thereof A liquid crystal display device (hereinafter sometimes referred to as “LCD”) is widely used as a display device of a clock, a computer, a television, or the like. This LCD is a display device that uses a liquid crystal in which the orientation of molecules changes and the polarization direction changes only by applying a slight potential, and usually has a structure in which a liquid crystal layer is sandwiched between two electrode substrates. I have.

In such an LCD, it is desirable that the thickness of the liquid crystal phase be as small as possible, and that the thickness of the liquid crystal phase be uniform. In other words, if the thickness of the liquid crystal phase varies, the intensity of the electric field applied to the liquid crystal phase becomes partially non-uniform, so that the contrast ratio of the image changes depending on the location and the image becomes uneven. Furthermore, since the response speed of the liquid crystal to an input signal changes according to the thickness of the liquid crystal layer and the electric field strength, if the thickness of the liquid crystal layer has a large variation as described above, a difference occurs in the response speed and a clear image is obtained. Can not be obtained. For this reason, in an LCD, a gap having a desired thickness is formed by interposing a spacer made of an insulator between two electrode substrates, and the gap is filled with a liquid crystal material, so that the gap between the two electrode substrates is thin. A method of forming a uniform liquid crystal layer is used.

As described above, since the thickness of the liquid crystal layer is determined by the size of the spacer interposed between the electrode substrates, the thickness of the liquid crystal layer varies depending on the spacer density per unit area on the electrode substrate. Therefore, in order to make the thickness of the liquid crystal layer uniform, use spacers of uniform size,
Such spacers must be distributed on the electrode substrate at a uniform density per unit area.

Conventionally, spacers have been dispersed on a substrate by spraying a slurry in which spacer particles are dispersed in a liquid from a nozzle.However, in this method, it is difficult to disperse the spacer particles at a uniform density. There has been a strong demand for the development of a method capable of uniformly dispersing powder such as spacer particles on a substrate.

An object of the present invention is to solve the problems associated with the prior art as described above, and to provide a method of spraying powder such as spacer particles on a substrate at a uniform density. The purpose is. Further, another object of the present invention is to provide a method capable of spraying powder such as particles for spacers at once with a uniform density on a substrate.

Another object of the present invention is to provide a powder-coated base material in which powder is dispersed at a uniform density per unit area on the base material by the above-described method. It is intended to provide a dispersed transparent electrode substrate.

Another object of the present invention is to provide a liquid crystal display cell having a uniform thickness of a liquid crystal layer obtained by using a transparent electrode substrate in which the powder is dispersed at a uniform density per unit area.

SUMMARY OF THE INVENTION A spraying method according to the present invention is directed to a method of spraying a powder dispersion slurry on a substrate while relatively moving a substrate or a nozzle, in a moving direction and in a direction perpendicular to the moving direction. The powder-dispersed slurry is sprayed from two or more nozzles displaced from each other so that the spray area of the powder sprayed by the respective nozzles overlaps the base material surface when viewed from the moving direction. It is characterized by doing.

Further, the substrate with powder according to the present invention is a substrate in which powder is dispersed on the substrate, the powder density per unit area of the powder at any point on the substrate, It is characterized in that it is within a range of ± 50% with respect to the average powder density on the substrate.

Further, the liquid crystal display cell according to the present invention, the powder density per unit area of the powder at any point on the transparent electrode substrate,
It is characterized by being formed from a transparent electrode substrate within a range of ± 50% with respect to the average density of the powder on the substrate.

Next, the method for dispersing powder, the substrate with powder and the liquid crystal display cell according to the present invention will be described in detail.

First, the method for dispersing powder according to the present invention will be described.

FIG. 1 shows an example of a spray amount distribution curve when powder is sprayed using one nozzle. In the present invention,
This spray amount distribution curve may be simply described as “pattern”.

The non-uniform density per unit area of the powder in the conventional method is due to the slurry in which the powder is dispersed in the liquid (hereinafter, referred to as a slurry).
Slurry) is sprayed in the direction of relative movement, and when passing through an orthogonal line segment on the substrate, the pattern sprayed on the line segment does not become flat, and as shown in FIG. This is because it becomes semicircular. That is, for example, as shown in FIG. 1, the slurry sprayed from the nozzle 11 is relatively indicated by a pattern 14 in a section formed by the nozzle 11 and a line segment 13 perpendicular to the arrow 12 indicating the moving direction. Is spread on the substrate 15 in such an amount as to be applied.

Therefore, the amount of powder sprayed just below the nozzle 14a is relatively large, but the amount of powder sprayed at the foot 14b of the pattern is relatively small. For this reason, the density of the powder sprayed on the base material is highest near the nozzle 14a immediately below the nozzle and lowest near the skirt 14b, and the powder density is uniform even when spraying is repeated under such conditions. It is difficult to manufacture a substrate with a coating.

The present invention provides the above spray amount distribution curve, that is, by arranging a plurality of nozzles so that the pattern has a flat portion and spraying the slurry, the powder per unit area of the powder sprayed on the substrate The knowledge that the density becomes uniform was obtained.

In order for the above pattern to have a flat part,
In the present invention, two or more nozzles are used. The two or more nozzles are provided so as to be displaced from each other in the relative movement direction of the nozzle or the base material and in a direction perpendicular to the movement direction. Further, the respective nozzles are arranged at positions where the spraying area of the powder formed by spraying the powder dispersion slurry from the two or more nozzles overlaps when viewed from the nozzle or the moving direction of the base material. I do.

Thus, the whole pattern obtained by arranging the nozzles and synthesizing the patterns of the respective nozzles has a flat portion.

As described above, in the present invention, the nozzles adjacent to one nozzle may be arranged so as to be displaced substantially in the horizontal direction with respect to the moving direction of the nozzle or the base material. When the spray areas formed by the respective nozzles are directly overlapped with each other, the flow of the powder in the overlapped spray area is disturbed, and it is difficult to control the spray amount of the powder in this area. Therefore, the synthesized pattern is not flat.

For this reason, in the present invention, two or more nozzles are arranged obliquely shifted with respect to the movement direction, so that the scatter areas formed by the respective nozzles do not directly overlap but overlap on the line segment. Is particularly preferred.

FIG. 2 schematically shows an example in which the nozzles are arranged obliquely shifted.

In the embodiment shown in FIG. 2, the moving direction of the substrate 25 is indicated by an arrow A.

In FIG. 2, a nozzle 21a is provided for spraying powder in a region on the left side L of the center line C of the base material, and a nozzle 21b for spraying powder is provided in a region on the right side R. I have.

When a plurality of nozzles are arranged one behind the other as shown in FIG. 2, the vertical distance Y between the centers of the nozzles is
a and the spray area 26 of the powder formed by the nozzle 21b
It is preferable that the a and 26b do not directly contact each other, and more usually, the powder dispersion slurry is sprayed by the nozzle 21a before the solvent forming the powder dispersion slurry sprayed by the preceding nozzle 21b evaporates. Arrange each nozzle at a distance as possible.

The horizontal distance X between the centers of the nozzles 21a and 21b is equal to the distribution areas 26a, 26 formed by the nozzles.
The distance b is set so that the powder-dispersed slurry can be superimposed and sprayed near the center line C of the base material 25 by both of them. This distance can be determined in consideration of the shape of the nozzle, spraying conditions, and the like. Note that, in FIG. 2, the hatched portion is a scattered area that overlaps when viewed from the moving direction.

By dispersing the slurry by disposing the nozzles at the positions as described above, the entire pattern obtained by synthesizing the pattern (spray amount distribution curve) of each nozzle has a flat portion between adjacent nozzles. Thus, it is possible to obtain a powdered substrate in which the powder is very uniformly dispersed, corresponding to the entire pattern.

In the present invention, the slurry is sprayed such that the spray area extends over both ends of the substrate parallel to the relative movement direction of the substrate or the nozzle, so that the powder is evenly distributed over the entire substrate. can do.

When three or more nozzles are used, the relationship between adjacent nozzles may be set as described above.

FIG. 9 shows an example of nozzle arrangement when three nozzles are used.

The nozzle used in the present invention may be any type of nozzle as long as the synthesized pattern has a flat portion. Preferably, a two-fluid fine spray nozzle is used. More preferably, it is preferable to use a nozzle having two or more axes of symmetry in the shape of the cross section of the nozzle hole, such as a rectangle or an ellipse. Examples of preferred nozzle configurations for use in the present invention are shown in FIGS. In the present invention, the nozzles may be arranged such that the nozzles having two or more symmetry axes and the nozzles not having two symmetry axes are alternately arranged. It is particularly preferable to arrange a nozzle having the same. The nozzles may be a combination of the same nozzle or a combination of different nozzles.

By arranging the nozzles so that the patterns do not match, and spraying the slurry from the nozzles onto the substrate,
Variations in powder density per unit area can be reduced.

In the present invention, if the powder concentration in the slurry and the supply of the slurry, the moving speed of the substrate or nozzle, and the distance between the substrate and the nozzle are appropriately adjusted, the number of powders can be arbitrarily changed at a uniform density per unit area. be able to.

Substrates that can be used in the present invention include glass, plastic sheets and plastic films. Further, a base material having a film having various functions formed on the surface thereof is used. For example, when manufacturing a transparent electrode substrate for forming a liquid crystal display cell, glass having ITO formed on its surface as a substrate (hereinafter referred to as ITO)
Etc.).

Further, as the powder to be sprayed on such a substrate, silica fine powder, glass fiber, α-alumina fine powder,
Resin fine powder or the like can be used. For example, when manufacturing a liquid crystal display cell, silica fine powder having an average particle diameter of 0.1 to 20 μm is used. In the present invention, such a powder is used as a slurry dispersed in an organic solvent having a relatively low boiling point.

In the present invention, the density per unit area of the powder was determined by, for example, providing a virtual horizontal line and a virtual vertical line on a substrate with powder as shown in FIG. 5 and obtaining the powder density at the intersection of both. The average value of the density per unit area of the powder can be determined based on the value.

Then, based on the average value of the density per unit area of the powder calculated as described above, the variation in the density per unit area of the powder on the base material is obtained. The variation in the substrate is usually within ± 50% of the average value of the powder density of the entire substrate. The variation can be controlled within ± 35% by changing the spraying conditions and the like.

That is, the density of the powder on the substrate with the powder obtained by employing the spraying method of the present invention is schematically shown based on the value at each intersection measured as shown in FIG. When,
As shown in FIG. FIG. 6 is a diagram produced based on actually measured values of the base material with powder manufactured in Example 4. On the other hand, FIG. 7 is a diagram produced based on the actually measured values of the base material with powder manufactured in Comparative Example 1.

Comparing FIG. 6 with FIG. 7, it can be seen that by employing the method according to the present invention, the resulting powdered substrate has a very high powder density uniformity. .

By using the substrate with powder obtained by the method of the present invention as a transparent electrode substrate, a liquid crystal display cell with less variation in the thickness (cell gap) of the liquid crystal layer can be manufactured.

That is, since the liquid crystal display cell using the transparent electrode substrate has a small variation in the powder density of the spacer particles formed on the transparent electrode substrate, the cell gap variation is ± 10% of the average value of the cell gap. Within 0.1 μm, and further within ± 0.05 μm. Therefore, by using such a liquid crystal display cell, the intensity of the electric field applied to the liquid crystal layer is less likely to be partially non-uniform. Disappears. Furthermore, since the variation in the cell gap is small and the difference in the partial response speed is small, a clear image can be obtained by using the liquid crystal display cell of the present invention.

In addition, such a liquid crystal display cell is applied in accordance with a conventional method, for example, by applying a sealing resin to a peripheral portion of a transparent electrode substrate made of ITO glass using a method such as screen printing, and then applying the above-described method. Can be manufactured by sticking the transparent electrode substrate of the present invention obtained in the above.

Effect of the Invention In the method of the present invention, in the method of spraying the powder-dispersed slurry onto the substrate while relatively moving the substrate or the nozzle, two powders provided at different positions in the direction perpendicular to the moving direction are provided. The powder spray slurry is sprayed from the above nozzles onto the base material surface such that the spray areas of the powder sprayed by the respective nozzles overlap in the moving direction. Therefore, the powder-dispersed slurry can be evenly sprayed on the substrate, and the dispersion of the powder density per unit area of the powder sprayed on the substrate is reduced.

Moreover, by adopting the method of the present invention and adjusting the number of nozzles in accordance with the spraying area, a substrate with a powder having a large area can be manufactured by a single spraying of the powder dispersion slurry. Become. Therefore, the method of the present invention is particularly effective when manufacturing a large-area and large-sized LCD.

The variation of the powder density in the powder-coated substrate thus obtained is within ± 50% with respect to the average value of the powder density.

Therefore, by using the substrate with powder according to the present invention as an LCD electrode substrate, a liquid crystal display cell having a uniform liquid crystal layer thickness can be obtained, and an LCD displaying a clear image can be obtained.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Two-fluid fine spray nozzle (manufactured by Spraying Systems. Co., 1/4)
J, SU13A) were arranged as shown in FIG. 2, and silica fine particles (Shinito Ball SW, manufactured by Catalyst Chemical Industry Co., Ltd., average particle size 6.8 μm)
m) was dispersed in a mixed solution of ethanol / CFC (manufactured by Daikin Industries, Ltd., trade name: DIFRON S3, volume ratio: 1/1) so as to be 0.4% by weight to obtain a slurry. This slurry is
Air pressure 2kg / cm ² on 154mm × 300mm ITO glass under the conditions of Table 1
Spraying was performed at an air flow rate of 20 ml / min.

Thereafter, the mixture was heated at 90 ° C. for 30 minutes to dry the ethanol / fluorocarbon.

Examples 2 to 5 and Comparative Example 1 Example 1 except that spraying conditions were performed according to Table 1.
The same conditions were used.

Evaluation of Spray Density Spray density was measured at the measurement points (intersections of straight lines) in FIG.

 Table 1 shows the measurement results.

Examples 6 to 10 and Comparative Example 2 Resin for sealing (Epoxy resin manufactured by Mitsui Toatsu Co., Ltd.) 10
0 g of silica fine particles (Catalyst Chemical Industries, Ltd.
An average particle size of 6.8 μm) was dispersed to prepare a sealing composition.

The obtained sealing composition was coated with an alignment film having a thickness of 150 m.
The periphery of the ITO glass of mx 300 mm was printed by a screen printing machine.

Next, this ITO glass and the ITO glass substrates obtained in Examples 1 to 5 and Comparative Example 1 were bonded together, and were pressed under a pressure of 3 kg / cm ^2.
The resin was cured by heating at 150 ° C. for 1 hour to obtain a liquid crystal display cell.

Cell Gap Evaluation Method The cell gap was measured at the measurement points (intersections of the straight lines) in FIG.

 The results are shown in Table 2.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a spray amount distribution curve (pattern) of powder sprayed from one nozzle. 11: Nozzle hole, 14: Spray amount distribution curve (pattern) 14a: Immediately below the nozzle, 14b: Bottom portion FIG. 2 shows an example of the arrangement of two nozzles and the moving direction of the base material. It is. 21a, 21b ... nozzle holes, 26a, 26b ... spraying area, 25 ... base material Figs. 3 and 4 show the shapes of the nozzle holes. FIG. 5 is a diagram showing measurement points of the application density and the cell gap. FIG. 6 is a diagram schematically showing the distribution of powder scatter on the substrate manufactured in Example 4. FIG. 7 is a diagram schematically showing the distribution of powder scatter on the substrate manufactured in Comparative Example 1. FIG. 8 is a diagram showing a nozzle arrangement in the second or third embodiment.

Continuation of front page (56) References JP-A-58-176621 (JP, A) JP-A-60-19063 (JP, A) JP-A-1-224724 (JP, A) JP-A-63-96634 (JP) , A) JP-A-62-251721 (JP, A) JP-A-63-187121 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1339 500 B05B 7/00

Claims (5)

(57) [Claims] 1. A method for spraying a powder-dispersed slurry on a substrate while relatively moving a substrate or a nozzle, wherein the positions are shifted from each other in a moving direction and in a direction perpendicular to the moving direction. From two or more arranged nozzles, on the surface of the base material, so that the spraying area of the powder sprayed by each nozzle overlaps when viewed from the moving direction,
A powder dispersing method, which comprises dispersing a powder dispersion slurry. 2. A powder-coated substrate obtained by the method for dispersing powder according to claim 1, wherein a powder density per unit area of the powder at an arbitrary point on the substrate. Is within ± 50% of the average powder density on the substrate. 3. The powder density per unit area of the powder at any point on the substrate is within ± 35% of the average powder density on the substrate. The substrate with powder according to claim 2, wherein 4. The substrate with powder according to claim 2 or 3, wherein the substrate with powder is a transparent electrode substrate having electrodes formed on at least one surface. . 5. A liquid crystal display cell in which two transparent electrode substrates on which transparent electrodes are formed are arranged via a spacer so that the transparent electrodes face each other, wherein the transparent electrode substrate is provided. A liquid crystal display cell comprising the transparent electrode substrate according to claim 4.