JPH07187704A - Thermally decomposable carbon-coated carbon member having excellent releasability from glass - Google Patents

Abstract

PURPOSE:To inexpensively obtain a thermally decomposable carbon-coated carbon member having excellent releasability by coating the surface of a substrate of a carbonaceous material with a thermally decomposable carbon and specifying the concentration of boron in the thermally decomposable carbon- coated carbon member. CONSTITUTION:In a carbon member which is brought into contact with glass and used, requires releasability from glass and is obtained by coating the surface of a carbonaceous material as a substrate with a thermally decomposable carbon, the concentration of boron in a thermally decomposable carbon-coated carbon member is <=2ppm to give the objective thermally decomposable carbon- coated carbon member. In order to improve releasability from glass and to prevent separation of fine particles and attachment to glass, a denser coating film is preferable. Therefor, a carbonaceous material having <=40ppm ash content is preferably used as the substrate to increase density and releasability. Furthermore, by using the substrate having <=40ppm ash content, the whole impurities in the substrate are thermally diffused to prevent contamination of glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyrolytic carbon-coated carbon member having excellent releasability from glass. More specifically, glass pre-firing trays used for glass sealing, electrode support rods for CRT electron guns, adhesion of alumina and Kovar alloy, glass sealing jigs such as hermetic seals, bottles, etc. Molding molds for glass containers and glass lenses, lower plates for heat treatment of crystallized glass, suction pads for transporting glass lenses, etc. that are used in contact with glass and require mold release properties The present invention relates to a pyrolytic carbon-coated carbon member which can be preferably used as

[0002]

2. Description of the Related Art Generally, glass is heated to be molded and softened. A calcination tray used at that time,
It is an essential property that the members such as the molding die, the jig, the lower plate, and the absorbent pad that are in direct contact with the glass do not get wet with the glass.

Materials having wettability with glass, such as metals, have been used by applying a release agent on the surface thereof.
For example, in the case of a glass calcination tray, calcination is performed in an oxygen atmosphere such as air in order to thermally decompose the binder in the green compact of the powdered glass, but the tray used during the calcination is It was made of metal such as stainless steel, iron and nickel. In this case, since the glass adheres to the metal tray, it is necessary to apply a release agent such as boron nitride to the surface of the metal tray. In addition, after the calcination, the release agent adhered to the surface of the tray had to be removed with a keren knife, then washed with water, and the tray had to be dried, which required about 4 days for the entire calcination step. As described above, the conventional technique is not efficient because it requires a complicated process that requires a lot of labor and time.

Therefore, in recent years, although not as a tray for pre-firing of glass, the excellent heat resistance of carbonaceous materials and the excellent glass releasability and oxidation resistance of pyrolytic carbon have been utilized to obtain carbonaceous materials. A member in which a material is used as a substrate and a surface thereof is coated with pyrolytic carbon (hereinafter referred to as a pyrolytic carbon-coated carbon member) is used (Japanese Patent Laid-Open No. 63-30342, Japanese Patent Laid-Open No. 4342/1988).
-108619, JP-A-4-108624, and JP-A-4-193735).

However, the pyrolytic carbon-coated carbon member used in this manner is quality-controlled by focusing only on the total ash value, and for example, a member whose ash content is suppressed to 10 ppm or less is also partially used. However, even if such a member is used, the mold releasability from the glass is sometimes poor or insufficient, so that it is not possible to use the member with sufficient peace of mind. Further, in order to reduce the total ash content of the member to 10 ppm or less, it is of course necessary to use a carbonaceous material having a very high ash content of 10 ppm or less as a base material. Was expensive to.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention investigates the cause of the poor releasability from glass and provides an inexpensive pyrolytic carbon-coated carbon member excellent in releasability.

[0007]

As a result of investigating the cause of the poor releasability with glass, the present inventors have found that the concentration of boron contained in the pyrolytic carbon-coated carbon member contributes to the releasability. I found out that

That is, the present invention relates to a pyrolytic carbon-coated carbon member which is used in contact with glass and requires releasability from the glass, and whose surface is coated with pyrolytic carbon to provide a carbonaceous material. It has been found that by setting the boron concentration of the pyrolytic carbon-coated carbon member to 2 ppm or less, a member having excellent releasability from glass can be obtained.

Furthermore, the present invention has also found that by setting the ash content of the carbonaceous material to be the base to 40 ppm or less, a member having a better releasability from glass can be obtained.

[0010]

The boron concentration of the pyrolytic carbon coating film is set to 2 pp regardless of the boron concentration of the carbonaceous material as the substrate.
Even if it is suppressed to m or less, it has releasability. However, the releasability may gradually deteriorate while using such a member. This is because boron is the only element that forms a solid solution in the carbon material as a substitutional type and an interstitial type, so it is more likely to thermally diffuse than other impurity elements, and the boron in the substrate thermally diffuses into the coating film, causing This is probably because the concentration of boron in the covering film was high. Therefore, the boron concentration of the entire pyrolytic carbon-coated carbon member is specified to be 2 ppm or less.

There is no particular limitation on the ash content of the carbonaceous material which is the base of the member, and the purity of ordinary carbonaceous materials, for example,
Any carbonaceous material having an ash content of about 400 ppm may be used. That is, regardless of the ash content of the substrate, the boron concentration of the member is 2 pp even when the surface of the substrate is coated with pyrolytic carbon.
If it is m or less, it has releasability.

However, in order to further improve the releasability and to prevent the fine particles from desorbing from the surface of the film and adhering to the glass, a denser coating film is desirable.
Therefore, by using a carbonaceous material having an ash content of 40 ppm or less as a substrate, the denseness is increased and the releasability is further improved. Furthermore, the ash content is 40 ppm
By using the following substrate, it is possible to prevent all impurity elements in the substrate from being thermally diffused and contaminating the glass.
As a matter of course, at this time, the boron concentration of the member is 2
It is a characteristic that the content is required to be ppm or less.

The boron concentration of the carbon member coated with pyrolytic carbon is set to 2
In order to reduce the concentration to ppm or less, it is sufficient to use a carbonaceous material having a low boron concentration as a base and coat the pyrolytic carbon with a high-purity gas, but even in this case, the number of production batches increases. Then, boron was accumulated in the chamber, and the concentration of boron in the member unexpectedly increased to 2ppm.
Therefore, it is preferable to appropriately measure the boron concentration of the coated member by a means such as the curcumin method.

The carbonaceous material to be the substrate can be widely applied to general carbonaceous materials, but in particular, a so-called isotropic graphite material having an anisotropic ratio of the average thermal expansion coefficient of 293 to 1273 of 1.2 or less. , Or carbon fiber woven or non-woven fabric as aggregate and carbon as matrix
Carbon composite materials and the like are exemplified, but in any case, the average thermal expansion coefficient in the surface direction of the coating is 1.5 × 10 ⁻⁶ to
5.5 × 10 ⁻⁶ / K (293 to 1273K) is more preferable. If the coefficient of thermal expansion deviates from this range, peeling or cracking may occur due to the difference in coefficient of thermal expansion between the substrate and the coating film.

The method of forming pyrolytic carbon is based on chemical vapor deposition (CV).
A known method such as method D) may be used, and an example thereof is a hydrocarbon gas such as methane or propane, and hydrogen gas is allowed to coexist as necessary to adjust the concentration of these hydrocarbon gases. However, it is desirable to avoid coexistence of O ₂ and H ₂ O because they have a bad effect. Temperature range during vapor deposition is 800-25
Wide range up to 00 ° C, preferably 1000 ° C
To 2000 ° C. Further, the pressure in the reaction chamber is operated as a total pressure (hydrocarbon partial pressure + hydrogen partial pressure). A lower hydrocarbon partial pressure gives a better quality coating film, but if it is too low, the vapor deposition rate becomes slow. Total pressure is 300 Torr or less,
It is desirable to operate under conditions of 100 Torr or less.

The thickness of the coating film of pyrolytic carbon should be such that peeling or cracking does not occur, and is usually 1 to 500 μm, but preferably 5 to 100 μm. 5μ
If it is less than m, the releasability from the glass is slightly diminished, and 100μ
If it is thicker than m, the coating film may be cracked and peeled from the substrate, which is not preferable. The coating may be applied to the entire surface of the substrate, but may be applied only to the surface contacting the glass.

[0017]

[Function] Boron reacts with oxygen to form glassy boron oxide (B ₂ O ₃ ), and when the boron concentration exceeds 2 ppm, silicon oxide (SiO ₂ ) and boron oxide, which are the main components of glass, It is thought that the releasability is deteriorated because the amount of adherence of is increased. In particular, this boron oxide
Since it melts at a relatively low temperature of about 450 ° C, it is considered that the contribution of deterioration of releasability is greater than that of oxides of other impurity elements (for example, iron, vanadium, nickel, aluminum, etc.) that adhere to silicon oxide. .

Further, in order to obtain a pyrolytic carbon-coated carbon member having a better releasability, the carbonaceous material as the base material should have an ash content of 40 ppm or less. It can be obtained at an extremely low cost as compared with ash having a content of 10 ppm or less.

[0019]

EXAMPLES The present invention will be described in detail with reference to examples in which a tray for calcination of glass is used. The ash content is based on Japanese Industrial Standard (JIS) R 7223, and the boron concentration in the tray is a value measured by the curcumin method for those manufactured in the same batch.

Examples and Comparative Examples As a substrate, the boron concentration was 1 ppm or less, 2 ppm and 3
ppm isotropic graphite (ash content 400 ppm, average thermal expansion coefficient 4.2 × 10 ^{−6 to} 4.5 × 10 ⁻⁶ / K (293 to
1273K), an anisotropy ratio of average thermal expansion coefficient of 1.1, and a bulk density of 1.73 to 1.75 g / cm ³ ), and a plurality of trays coated with pyrolytic carbon on the entire surface with a thickness of 20 μm in different batches. Manufactured. The boron concentration is measured again from among them, and a tray having a boron concentration of 1 ppm or less, 2 ppm and 3 ppm is selected, and a borosilicate glass compact, which is a glass sealing material, is placed on the tray having various boron concentrations, and in the air. Pre-baking (pre-baking temperature 600 ° C.) was performed. The trays with a boron concentration of 1 ppm or less and 2 ppm had good mold releasability from the glass, whereas the glass preliminarily baked using the tray with a boron concentration of 3 ppm had a partial discoloration and adhered to the tray. Some were also seen. In addition, this calcination step is 1
Finished in days.

Further, the boron concentration is 1 ppm or less and 2 pp
Compared with the tray of m, the tray of 3 ppm increased the degree of color change of glass as the number of times of use increased, and the number of sticking to the tray also increased.

Further, a tray having a boron concentration of 2 ppm or less, in which a substrate having an ash content of 40 ppm or less and coated with pyrolytic carbon, has a particularly good releasability from glass.

[0023]

As described above, the pyrolytic carbon-coated carbon member according to the present invention is inexpensive and has excellent releasability, and in addition to the glass calcination tray of the above-mentioned embodiment, a glass sealing treatment member. The present invention sufficiently exerts the effect of the present invention as a member that needs to be released from glass such as a tool, a molding die, a lower plate for heat treatment, and an absorbent pad for transportation.

Claims (2)

[Claims] 1. A pyrolytic carbon-coated carbon member which is used in contact with glass and requires releasability from glass, and whose surface is coated with pyrolytic carbon to provide a pyrolytic carbon-coated carbon member. Boron concentration of carbon coated carbon member is 2ppm
The following is a pyrolytic carbon-coated carbon member. 2. The ash content of the carbonaceous material as the base is 40 pp.
The pyrolytic carbon-coated carbon member according to claim 1, wherein the carbon member is m or less.