JPH09142970A - Formation of glass coating layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a glass coating layer uniformly with high accuracy at a low cost by forming an Al film on the surface of an insulating substrate to be formed with the glass coating layer, then immersing and arranging this substrate together with a counter electrode into a dispersion of the fine powder of glass, impressing a DC voltage between the electrode and the Al film to form an electrodeposited layer of the fine powder of the glass on the Al film, then firing the layer. SOLUTION: The Al film is formed by a sputtering method and its thickness is specified to 5 to 100nm. The dispersion of the fine powder of the glass is formed by dispersing the glass having 1.0 to 4.0μm average grain size at a ratio of 0.075 to 0.25wt.% into a dispersion medium. The dispersion medium prepd. by adding water at 2.0 to 5.0vol.% to an org. solvent, such as isopropyl alcohol, is used. The DC voltage is specified to 400 to 600V. Firing is executed by holding for the prescribed time at a temp. lower than the m.p. of the Al in an oxidizing atmosphere, then heating up to a temp. above the softening point of the glass. For example, the temp. is held at 580 to 650 deg.C for 3 to 5 hours in a first firing stage and is heated up to 1100 to 1250 deg.C and is then lowered down to room temp. in a second firing stage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a glass coating layer, and more particularly to a method for easily and uniformly forming a glass coating layer for imparting desired functionality to the surface of an insulating substrate.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a glass coating layer on an insulating substrate such as an alumina substrate in a plane or in a predetermined pattern, a screen printing method or a spraying method using a spray is generally used.

[0003]

Among the above-mentioned conventional methods, the screen printing method requires a large number of printings for highly accurate patterning or formation of a thick coating layer,
This has led to a decrease in manufacturing efficiency and a rise in production costs.

On the other hand, the spraying method using a spray has a poor recovery rate of the glass powder after spraying, and requires a masking step and a step of removing the glass powder adhering to an unnecessary portion. Similarly, there is a problem that the manufacturing efficiency is poor and the cost is high.

The present invention solves the above-mentioned conventional problems and provides a method for forming a glass coating layer on an insulating substrate, which allows a desired glass coating layer to be formed easily and at low cost, uniformly and with high precision. The purpose is to do.

[0006]

The method for forming a glass coating layer of the present invention is a method for forming a glass coating layer by depositing glass fine powder on an insulating substrate and then firing the powder. After forming an aluminum film on the surface of the insulating substrate that forms the glass substrate, the glass substrate is immersed in a dispersion of fine glass powder together with a counter electrode, and a DC voltage is applied between the counter electrode and the aluminum film to form a film on the aluminum film. It is characterized in that an electrodeposition layer of fine glass powder is formed on and then fired.

By adhering the fine glass powder by the electrodeposition method, the process can be simplified and the cost can be reduced, the thickness can be easily controlled, and the glass coating layer having a uniform thickness can be accurately formed.

Particularly, firing after forming the electrodeposition layer of fine glass powder is carried out by holding the temperature below the melting point of aluminum for a predetermined time in an oxidizing atmosphere, and then raising the temperature to the softening point of the glass or higher. Thereby, a flat and uniform glass coating layer can be formed on the insulating substrate with good adhesiveness.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the present invention, first, an aluminum film is formed on the glass coating layer forming portion on the surface of the insulating substrate. An alumina substrate is generally used as the insulating substrate, but the insulating substrate is not limited to this and may be a substrate made of an insulating material other than alumina.

The thickness of the aluminum film formed is
In the baking after forming the electrodeposition layer of fine glass powder, aluminum is oxidized to alumina (Al ₂ O ₃ ), which is required to be not excessively thick in order to be sufficiently absorbed in the glass coating layer. . Further, if the thickness of this aluminum film is too thin, it is difficult to form an aluminum film having a uniform thickness. Therefore, the thickness of the aluminum film is preferably 5 to 100 nm.

As a method for forming the aluminum film on the insulating substrate, the sputtering method is suitable.

After the aluminum film is formed on the insulating substrate, the aluminum film is immersed in a dispersion liquid of fine glass powder together with the metal plate to be the counter electrode, and the aluminum film is formed between the counter electrode and the aluminum film on the insulating substrate. A DC voltage is applied to the electrode to form an electrodeposition layer of glass fine powder on the aluminum film.

Here, as the dispersion liquid of glass fine powder,
It has a desired glass composition and an average particle size of 1.0 to 4.0 μm.
Glass fine powder of about 0.075-0.25 in the dispersion medium
What is dispersed at a ratio of about wt% is used. As the dispersion medium, it is preferable to add about 2.0 to 5.0% by volume of water to an organic solvent such as isopropyl alcohol.

Further, the magnitude of the DC voltage is preferably in the range of 400 to 600 V from the viewpoint of electrodeposition efficiency and equipment.

The thickness of the electrodeposition layer of fine glass powder formed can be easily controlled by adjusting the magnitude and time of the DC voltage applied between the aluminum film and the counter electrode. According to the deposition method, an electrodeposition layer having a uniform thickness can be formed. The state of adhesion of the fine glass powder can be easily confirmed by observing the turbidity of the dispersion liquid.

After the electrodeposition layer of glass fine powder is formed on the aluminum film on the surface of the insulating substrate, the insulating substrate is pulled out from the dispersion liquid, dried, and then baked.

In the present invention, the firing is carried out by holding the temperature in the oxidizing atmosphere, for example, in the air at a temperature lower than the melting point of aluminum for a predetermined time, and then raising the temperature to the softening point of the glass or higher. preferable.

That is, by keeping the temperature lower than the melting point of aluminum for a predetermined time in the oxidizing atmosphere (hereinafter, this step is referred to as "first firing step"), the electrodeposition layer of the fine glass powder becomes uniform. At the same time as forming the coating layer, the aluminum film is oxidized to become alumina, which is taken into the glass coating layer, and the insulating substrate and the glass coating layer are firmly bonded and integrated. As mentioned above, the thickness of the aluminum film is 100
When it is thicker than nm, the oxidation during firing becomes insufficient and a part of the surface layer of aluminum is taken in the glass, but most of it remains as an oxide of aluminum metal in the glass layer, which is not preferable.

After being kept at a temperature lower than the melting point of aluminum in the oxidizing atmosphere for a predetermined time in this way, the temperature is raised to a temperature equal to or higher than the softening point of the glass and fired (hereinafter, this step is referred to as "second firing step"). The surface of the glass coating layer is flattened, and the surface of the glass coating layer can be made smooth and uniform.

The first firing step is, specifically, 20
It is carried out by raising the temperature to a temperature lower than the melting point of aluminum by 10 to 80 ° C., for example, 580 to 650 ° C. at a temperature rising rate of ˜50 ° C./min, and holding this temperature for 3 to 5 hours. In addition, the second firing step is performed after the first firing step by 2
2 from the softening point of glass at a heating rate of 5 to 50 ° C / min
50 to 400 ° C higher temperature, for example 1100 to 1250 ° C
The temperature is raised to room temperature, and then to room temperature.

[0022]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 A glass coating layer was formed on a 96% alumina substrate having a thickness of 0.5 mm, a width of 50 mm and a length of 75 mm according to the method of the present invention.

First, after washing this alumina substrate with water,
An aluminum film having a thickness of about 40 nm was formed on the surface by sputtering. Separately, isopropyl alcohol 5
In a dispersion medium to which 3% by volume of water was added to 00 ml,
A dispersion liquid was prepared in which 0.3 g of glass fine powder having the following composition (average particle diameter 3.0 μm, softening point 850 ° C.) was dispersed.

Glass composition (% by weight) Al ₂ O ₃ : 11.8 SiO ₂ : 61.0 CaO: 9.8 BaO: 7.2 This dispersion was placed in a beaker, together with a metal plate serving as a counter electrode. The alumina substrate having the aluminum film formed thereon was immersed and placed so that the alumina substrate on which the aluminum film was formed was positioned at the center of the metal plate, and a DC voltage of 600 V was applied between the metal plate and the aluminum film of the alumina substrate. The adhered state of the glass fine powder was confirmed by visually confirming the turbidity of the dispersion liquid, and the glass fine powder in the dispersion liquid was sufficiently adhered.

After that, the alumina substrate was taken out, dried with hot air, and then fired using Kanthal Super (box furnace) under the following firing conditions.

Firing conditions First firing step: 600 ° C. at 25 ° C./min in air
And hold at 600 ° C. for 3 hours Second firing process: After the first firing process, further 30 ° C./min
After that, the temperature was raised to 1210 ° C. and the temperature was lowered to the atmospheric temperature at 50 ° C./min. As a result, a flat and uniform glass coating layer having a thickness of 25 μm could be formed with good adhesion.

The thickness of the aluminum film is 150 nm.
When a glass coating layer was formed in the same manner as described above except for the above, the oxidation of aluminum due to firing was insufficient, and sufficient non-adhesiveness could not be obtained. Also,
When an attempt was made to form the aluminum film to have a thickness of 2 to 3 nm, a uniform aluminum film could not be formed, which made it difficult to form a desired glass coating layer.

Comparative Example 1 A glass coating layer was formed on the same alumina substrate as that used in Example 1 by the screen printing method using the same fine glass powder as that used in Example 1. 1
In order to form a glass coating layer having the same thickness as the glass coating layer formed in step 3, it was necessary to repeat screen printing three times, and the number of steps was large, so that the glass coating layer could not be formed efficiently. .

[0030]

As described in detail above, according to the method for forming a glass coating layer of the present invention, a desired glass coating layer can be formed on an insulating substrate easily and at low cost, uniformly and with high precision. it can.

Claims (3)

[Claims] 1. A method for forming a glass coating layer by depositing fine glass powder on an insulating substrate and then firing the glass substrate, comprising forming an aluminum film on the surface of the insulating substrate on which the glass coating layer is formed, and then forming a glass. Immersed in a dispersion liquid of fine powder together with a counter electrode, a DC voltage is applied between the counter electrode and the aluminum film to form an electrodeposition layer of glass fine powder on the aluminum film, and then firing. A method for forming a glass coating layer, comprising: 2. The method according to claim 1, wherein the firing is performed by holding the temperature at a temperature lower than the melting point of aluminum for a predetermined time in an oxidizing atmosphere, and then raising the temperature to a temperature equal to or higher than the softening point of the glass. And a method for forming a glass coating layer. 3. The method for forming a glass coating layer according to claim 1, wherein the aluminum film has a thickness of 5 to 100 nm.