JPH05311109A - Carbon coating for black matrix - Google Patents

Abstract

PURPOSE:To obtain an aqueous carbon coating capable of providing a coating film sharply outlined in forming a black matrix by selectively removing a carbon coating film. CONSTITUTION:The carbon coating for black matrix is characterized in that a binder is an emulsion of silica-modified acrylic resin and carbon particles are graphite and/or crystallized carbon black in a coating suspending carbon particles in a colloidal state in water containing a dispersing agent and the binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon paint suitable for a black matrix of a color cathode ray tube, an optical filter for liquid crystal or plasma display, etc., which selectively removes a carbon film to form a film having a complicated pattern. is there.

[0002]

2. Description of the Related Art A black matrix for improving the brightness and contrast of pixels of a color cathode ray tube will be described below as an example. The carbon coating material for the black matrix contains about 10% by weight of graphite fine powder in water and about 1% by weight of water glass as a binder, or a dispersant such as carboxymethyl cellulose. A suspension is known, and such a graphite paint is disclosed in Japanese Examined Patent Publication No.
No. 1-5856. In addition, there is one in which crystallized carbon black is used instead of graphite, which is described in JP-A-62-157647.

By the way, in forming the black matrix, first, polyvinyl alcohol (PVA) is formed on the glass surface.
And a photosensitive resin (resist) such as ammonium dichromate are applied to form a thin film, and then the film is exposed to UV light through a mesh shadow mask and then washed with water. Only remains on the glass surface.
In the second step, a carbon coating is applied and dried on this to form a uniform carbon coating. Next, in the third step, the resist is softened and swelled by immersing it in hydrogen peroxide water, and when hot water is sprayed onto it, the resist is removed together with the carbon coating on its surface, and is selectively removed. A carbon film (black matrix) having a large number of pores is formed.

The carbon paint is such that carbon particles do not easily settle down, a thin coating film can be formed, it adheres to the glass surface with sufficient strength and is not corroded or peeled off by spraying hot water, etc. Is required to be clear.

[0005]

According to the conventional carbon paint, the outline of the hole through which the carbon coating has fallen is not as clear as desired. That is, the hole removal property (breakage of the selective removal wall surface) was poor. It is an object of the present invention to provide a coating material which provides a carbon coating film having a uniform coating film, good adhesion, and good hole removal properties.

[0006]

In order to solve the above-mentioned problems, the present invention provides a coating composition in which carbon particles are colloidally suspended in water containing a dispersant and a binder, and the binder is a silica-modified acrylic resin. The present invention provides a carbon coating material for a black matrix, which is an emulsion and has carbon particles of graphite and / or crystallized carbon black.

In the present invention, a silica-modified acrylic resin having a silica content of about 40 wt% is preferably used. Graphite is natural graphite in the form of flakes with an apparent particle size of 1 μm or less, which is used in conventional colloidal graphite paint, and crystallized carbon black has an average structure particle size of 80.
Those having a thickness of up to 160 nm are preferably used.

The composition of the carbon coating composition cannot be specified because there is a composition of the undiluted solution in consideration of storage and a composition of which the viscosity is adjusted to an appropriate value at the time of application, but it cannot be specified.
0 wt%, dispersant 1-4 wt%, binder 0.5-1 wt
%, The balance is water. Ammonia water may be added if necessary. In applications other than the black matrix, a metal oxide or silicon carbide may be contained in order to adjust the conductive properties of the coating.

[0009]

Function: The binder functions as an adhesive. Since water glass, which is a conventional binder, is poor in water resistance, it dissolves in the hot water used when removing holes, making it difficult to cut holes, and
Since it is alkaline, when an aqueous phosphor slurry such as a CRT (cathode ray tube) is applied to the hole, it may melt at the contact surface to deteriorate the phosphor. In the present invention, since a resin binder having good water resistance is used, silica-modified acrylic resin among many resins is excellent in water resistance, chemical resistance, and adhesiveness. It is contained in the form of.

Silica-modified acrylic resin decomposes when it is baked after forming a matrix as in the case of CRT. Carbon becomes a coating film to absorb light or become a conductor. The colloidal carbon in the paint is graphite, crystallized carbon black, or a mixture thereof.

[0012] Graphite has a good physical adhesiveness because a thin coating film can be obtained, but on the other hand, since the particles are relatively large, the shelf life of the paint and the hole removal property are slightly inferior. On the other hand, compared to graphite, carbon black has a property of easily aggregating in a liquid, it is difficult to obtain a thin coating film, and the adhesiveness is slightly inferior, but the particles are small and it does not take time to grind. The advantages are that it is hard to settle in the suspension, the holes are easily removed, and the surface of the coating film has an appropriate roughness, so that the adhesion of the phosphor is good. When the two are mixed, a coating material having the properties of the respective drawbacks compensated for can be obtained.

The carbon black used in the present invention needs to be crystallized. Normal carbon black has a temperature of 550 to 620 ° C. at which weight is rapidly reduced when heated in air using a thermobalance. Compared with graphite powder, it is about 100 ° C lower and has inferior heat resistance. However, what was heated at a temperature of 2000 to 3500 ° C. for about one day has a temperature of 680 to 720 ° C., and the heat resistance is improved. Figure 2
Is a schematic view of ordinary carbon black and heat-treated carbon black observed with a transmission electron microscope at a magnification of 900,000 times. Normal carbon black (a) does not show crystals, but heat-treated one (b) is Polygonal crystals are observed.

Further, in the crystallized carbon black, several particles are combined to form one particle. FIG. 3 is an example of the transmission cross section, and the diameter 3 of the circle shown by the dotted line is the structure grain size. If it is too small, the heat resistance becomes poor and the amount of gas released increases, which is not preferable. On the other hand, if it is too large, the hole-removing property is deteriorated and a coating film having a sharp contour cannot be obtained. Therefore, 80 to 160 nm is preferable. The circle diameter 2 shown by the solid line is the primary particle diameter. If it is too small, the heat resistance will be poor, while if it is too large, the color tone will be poor.

The dispersant has a function of uniformly suspending carbon particles in water containing a binder, preventing the particles from aggregating, and maintaining a colloidal state. As the dispersant, when the carbon particles are graphite, carboxymethyl cellulose is the most preferable combination. On the other hand, in the case of crystallized carbon black, since the particle size is small, the property of easily aggregating in water is relatively large, and an interfacial lubricant having strong permeability is selected. Examples of such substances include anionic β-naphthalene / sodium sulfonate.

[0015]

EXAMPLES The present invention will be described below with reference to examples. The conventional paint for comparison is 10% by weight of natural graphite powder having an apparent particle size of 1 μm or less, 0.8% by weight of water glass as a binder, 1% by weight of carboxymethylcellulose as a dispersant, and a concentration of 2
It is a paint consisting of 1% by weight of 8% by weight ammonia water and the balance water.

The carbon coating material of the example was a coating material (sample 1) containing 1% by weight of silica-modified acrylic resin (Chuo Rika, trade name ES-J805) in place of water glass among the components of the conventional coating material. 10% by weight of crystallized carbon black having an average primary particle size of 14 nm and an average structure particle size of 100 nm, 1% by weight of silica-modified acrylic resin (manufactured by Chuo Rika, trade name ES-J805) as a binder, and a dispersant. As β-naphthalene sodium sulfonate (made by Kao,
Product name: Demol N) 3% by weight, 1% by weight of ammonia water with a concentration of 28% by weight, the remaining water (sample 2), and the above sample 1 and sample 2 mixed at a ratio of 1: 1 (weight ratio) (Sample 3) was prepared.

First, a PVA resist was applied to a clean glass plate, dried, and irradiated with ultraviolet rays through a shadow mask having circular holes, followed by washing with water to form a disc-shaped resist. Then, the coating material is applied and dried to form a coating film,
After immersing in a mixed solution of hydrogen peroxide water and sulfuric acid at a temperature of 50 ° C., hot water having a pressure of 7 kgf / cm ² was sprayed on the coating surface to remove the resist and obtain a carbon coating film having circular holes.

FIG. 1 is an explanatory view showing the hole removal property as a result of observing the hole portion of the coating film using a scanning electron microscope for each of the comparative sample using the conventional paint and each sample of the example.
1A and 1B are a perspective view and a vertical cross-sectional view, respectively, of the comparative sample, and (C) and (D) of the sample 2 having the best hole removal property among the example samples. The comparative sample has a jagged circle and is tapered, and has a hole protruding slightly above the glass surface. On the other hand, the sample 2 of the example shows a round shape with good sharpness, and the side faces are also vertically standing from the glass plate. Sample 1 using graphite is slightly inferior to Sample 2 and shows an intermediate pattern between (a) and (c). Further, the hole removal property of the sample 3 which is the mixed paint is about the intermediate level between the sample 1 and the sample 2.

This is because water glass as a binder has poor water resistance and the edges of holes are easily eroded by water, whereas silica-modified acrylic resin has high strength and adhesion of coating film and is water resistant. It is shown that. Further, the finely crystallized carbon black shows a better hole escape property than the flake graphite particles.

[0020]

EFFECTS OF THE INVENTION According to the carbon paint of the present invention which uses a silica-modified acrylic resin as a binder, a coating film is selectively removed using a resist to form a complicated fine pattern such as a mesh pattern or a striped pattern. When used for a black matrix of a color cathode ray tube requiring a light-absorbing coating, a filter of liquid crystal, etc., it has a good hole-removing property, so that a clear image can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a hole missing property.

FIG. 2 is a schematic diagram illustrating the internal structure of carbon black.

FIG. 3 is an explanatory diagram of a particle size of carbon black.

[Explanation of symbols]

 1 crystal 2 primary particle size 3 structure particle size 4 glass plate 5 carbon coating 6 selective removal part

Claims (1)

[Claims] 1. A paint comprising carbon particles colloidally suspended in water containing a dispersant and a binder, wherein the binder is an emulsion of a silica-modified acrylic resin, and the carbon particles are graphite and / or crystallized carbon black. A carbon coating material for a black matrix, characterized in that