Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Reexamination Certificate
1999-07-01
2001-03-13
Parker, Fred J. (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
C427S474000, C427S476000
Reexamination Certificate
active
06200643
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of coating a non-conductive substrate.
Coating a substrate with a metal or a metal compound is widely conducted for corrosion protection, decoration, reinforcement and the like. The representative examples of prior art methods for coating a substrate include electroplating, vacuum deposition, and spraying.
Electroplating is a method of depositing a metal ion by an electrochemical reaction on an electrode dipped in a plating solution. This technique has disadvantages such as the types of coating materials being limited. In addition, only a coating in the order of a few microns is formed because a thick coating is difficult to form. In addition, electroplating is not an economical method because it requires a complicated large-scale system and a large amount of electric power so that production cost is high. When a plating solution containing cyanogen, sodium hydroxide, or ammonia is used, plating efficiency and recovery rate of a coating material are low and waste disposal of the plating solution causes serious problems on preservation of environment. In the case of melt plating, a melted coating material tends to react with a substrate to be coated because the coating treatment is conducted at a high temperature.
On the other hand, vacuum deposition is a method of vacuum coating either by heating a target material placed on a filament or kept in a crucible by a heating resistor, electron beam or laser light, or by ion-sputtering of a target material. Although laser-heating and ion-sputtering can be conducted at a relatively low temperature compared with other vacuum deposition techniques, they can not eliminate such disadvantages as a crucible causing contamination and coating materials reacting with each other or with a substrate so that an alloy is formed because the laser-heating and ion-sputtering are classified as high-temperature coating methods using thermal melting. In addition, since particles vacuum-evaporated or sputtered from a target are so active as to react with residual gas to provide impurities, a coating having high purity can not be obtained. Moreover, coating efficiency and recovery rate of a coating material are low. The coating obtained by this method has low adhesion to a substrate and hence is not highly durable. Furthermore, when a substrate having a large area is coated, a coating having uniform thickness can not be obtained.
Spray coating is a method of coating a substrate by spraying a coating solution from a nozzle onto a substrate. This method is simpler than the above two methods. However, spraying has the disadvantage that a coating has low adhesion to a substrate and low density. In addition, this method is not economical because it requires special steps such as pre-washing of the substrate surface, pre-treatments for providing the substrate with adherability to a coating, a drying step and the like.
If the substrate to be coated has a complicated shape, for example, if the inner surface of a hollow cylinder is to be coated, a uniform coating can not be obtained by using any of the above methods.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a method of coating a substrate which overcomes the afore-mentioned disadvantages of the prior art.
Namely, the object of the present invention is to provide a method of coating a substrate which makes it possible to efficiently form a coating having high adhesion to the substrate, uniform thickness, and high purity at ambient temperature.
Another object of the present invention is to provide a method of coating a substrate which is useful in forming a coating having large thickness.
A further object of the present invention is to provide a method of coating a substrate, which makes it possible to form a coating at low electric power using a simple system.
Moreover, the object of the present invention is to provide a method of coating a substrate, which is economical and suitable to preservation of environment because a left unused coating material can be recovered easily at high recovery rate.
In addition, the object of the present invention is to provide a method of coating a substrate which is useful in forming a uniform coating on a substrate having a complicated shape.
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patent: 4780331 (1988-10-01), Cobbs, Jr. et al.
patent: 5279863 (1994-01-01), Escallon
patent: 5445852 (1995-08-01), Sugai
patent: 2 253 164 (1992-02-01), None
Kusubiki Atsuo
Sugai Isao
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Parker Fred J.
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