JPH03249173A - Crucible for evaporating aluminum - Google Patents

Abstract

PURPOSE:To obtain a crucible for evaporating Al with long time maintainability, capable of prohibiting the penetration of molten Al thereto and of forming to larger sizes by forming a vitreous carbon layer contg. TiC or ZrC on the surface of the graphite crucible. CONSTITUTION:The vitreous carbon layer contg. the TiC or ZrC is formed on the surface of the graphite crucible. The above-mentioned carbon layer is obtd. by applying a slurry obtd. by adding about 3vol.% Ti, Zr powder or TiC, ZrC powder to an org. material liquid, such as phenolic resin, furan resin, or tar pitch, having a high residual content of carbon, onto the surface of the crucible, subjecting the coating to a heating treatment in a nonoxidation furnace to carbonize and vitrify the org. materials and to carbize the Ti and Zr. The penetration of the Al is prohibited by the vitreous layer which has no pores and gaps, is dense and contains the carbide hardly eroded by molten Al. The life of the graphite crucible for evaporating Al is thus prolonged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crucible for aluminum evaporation, and more specifically to a crucible for evaporating aluminum thin films onto the surfaces of plastic films for food packaging, building materials, thin steel sheets for home appliances, etc. This invention relates to a long-life graphite crucible that accommodates and melts and evaporates the necessary aluminum.

[Conventional technology]

Conventionally, vacuum evaporation of aluminum has generally used a graphite crucible to house aluminum in a vacuum degree of 10-'~
The process is carried out at a temperature of 10-' Torr and an evaporation temperature of 1,400 to 1,500°C. Under these conditions, molten aluminum has extremely high fluidity and penetrates into the countless minute pores and gaps that exist in the graphite crucible. Graphite crucibles cannot be used practically because of the phenomenon that destroys the crucible.

Therefore, in order to extend the life of graphite crucibles, an improved graphite crucible has been proposed in which the countless pores and gaps in graphite are impregnated with alumina and carbon (Japanese Patent Laid-Open No. 6
1-76663). In addition, crucibles are commercially available that heat-treat phenolic resins, furan resins, tar pitch, etc., which have a large amount of carbonized residue, to make pyrolytic graphite glassy.

[Problem to be solved by the invention]

However, although the graphite crucible impregnated with alumina and carbon has less breakage and has a considerably longer lifespan than an untreated graphite crucible, the impregnated layer of alumina and carbon is shallow and the sealing of pores and gaps is insufficient. However, it breaks down in a relatively short period of time, making it unsuitable and unsuitable for large-scale vacuum evaporation equipment that operates continuously for long periods of time.

On the other hand, graphite glass crucibles do not cause the above-mentioned destruction, but because liquid organic materials such as resin and tar pitch are heat-treated and solidified, they can currently only produce thin-walled small items, and aluminum If it is solidified after melting, it will break due to the heat shrinkage of the aluminum, and its thin wall will cause strength problems, making it impossible to manufacture large crucibles for large-scale vacuum evaporation equipment.

In view of the above circumstances, the present invention aims to provide a crucible for aluminum evaporation, in which the life of the graphite crucible can be extended and the size of the crucible can be increased.

[Means to solve the problem]

The present invention is an aluminum evaporation crucible characterized by forming a glass card-shaped carbon layer containing TiC or ZrC on the surface of a graphite crucible.

The crucible for aluminum evaporation of the present invention is made by coating or impregnating the surface of a graphite crucible with Ti, Zr powder or TiC, 2rC powder added to an organic material liquid such as phenol resin, furan resin, or tar pitch with a large residual carbon content. and further heat-treated at 2000°C to 3000°C in an acid-free furnace to form a dense glassy layer of the coated and impregnated material,
It can be obtained by repeating these steps and increasing the thickness of the layer.

[Effect]

The vitreous layer of the present invention is dense with no pores or gaps, and prevents penetration of molten aluminum.

During heat treatment, Ti and Zr powders combine with organic materials to form carbides like TiC and ZrC, and these carbides are difficult to be eroded by molten aluminum.

In addition, when TiC powder or ZrC powder is added, no further progress of carbonization occurs during heat treatment, but it has the effect of preventing corrosion of molten aluminum as described above. As for the structure of the crucible, the thickness of the graphite part is increased to provide strength, and the above-mentioned vitreous substance is formed on the surface of the crucible, so that it is possible to prevent the neck from being damaged due to strength, and it is possible to achieve a large-sized crucible.

〔Example〕

In order to evaluate the crucible of the present invention, the following method was carried out.

2X 10-'T containing aluminum in a graphite crucible
The crucible was heated and held at 1450° C. in a vacuum of 1,450° C. to evaporate aluminum for 30 minutes, and then cooled to room temperature and taken out into the atmosphere to observe any abnormality in the crucible. For crucibles in which no abnormality was observed, aluminum was newly added in an amount equivalent to the amount of aluminum in the evaporation range, and the above operation was repeated until an abnormality was observed.

For comparison, a commercially available graphite crucible impregnated with alumina and carbon, and a commercially available crucible made of glassy graphite were also evaluated in the same way, and these are also shown in Table 1.

The graphite crucible of the present invention contains 3% by volume of furan resin.
A slurry resin to which Ti, Zr powder or TiC, ZrC powder was added at a ratio of 200 was applied to the surface of the crucible.
Gradually heat to 0°C in a non-oxidizing furnace to carbonize and vitrify the furan resin, and in the case of Ti and Zr powders, make these carbides. After holding for about 5 hours, cool to form a vitreous layer with a thickness of 0.3+ nm. A material formed on the surface of a graphite crucible was used.

As shown in Table 1, the life cycles of the examples of the present invention are significantly longer than those of the comparative examples. This is an effect of the dense glassy graphite and the inclusion of TiC and ZrC, which are difficult to corrode in molten aluminum. Comparative Example 1 was destroyed due to cracking caused by penetration of molten aluminum. In Comparative Example 2, the tension due to heat shrinkage that occurs after solidification of aluminum is 3111ff.
Thin cracks had occurred in the thick crucible.

〔Effect of the invention〕

The present invention provides a graphite crucible for aluminum evaporation that has a longer service life.

Claims (1)

[Claims] A crucible for aluminum evaporation, characterized in that a glassy carbon layer containing TiC or ZrC is formed on the surface of a graphite crucible.