Coating processes – Electrical product produced – Transparent base
Patent
1982-11-03
1984-10-09
Lusignan, Michael R.
Coating processes
Electrical product produced
Transparent base
427166, 427167, 427255, 4272552, 4272553, 118315, B05D 506, B05D 512
Patent
active
044761589
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a National Phase application corresponding to PCT/CH No. 82/00032 filed Mar. 4, 1982 under the Patent Cooperation Treaty and based, in turn, upon a Swiss National application No. 1520/81 filed Mar. 6, 1981 under the International Convention and the priority of which is claimed.
FIELD OF THE INVENTION
The present invention relates to a method of coating at least part of a substrate with a layer of a mineral substance; it likewise relates to a device for performing this method.
BACKGROUND OF THE INVENTION
The present method is based on the so-called CVD (chemical vapor deposition) technique which consists of directing gaseous blasts of one or more reagents onto a substrate which has been brought to a high temperature, these gaseous blasts uniting on the substrate or in the immediate vicinity thereof and depositing thereon a solid product, in the form of a coating which is uniform to a greater or lesser extent and results from a decomposition or chemical reaction of the said reagents. In usual practice, the reactive gases are guided onto the substrate by means of blast pipes arranged such that at the point where they meet the reactive gases are mixed in non-turbulent conditions, vortex motions likely to cause a premature reaction of the reactive gases and the deposition of part of the solid product on the ends of the said blast pipes and the other parts of the coating device being avoided as far as possible. Parasitic depositions of this type foul the device and rapidly alter the operational characteristics which is extremely undesirable.
Thus, for example, the patent FR-A- No. 2.348.165 (BFG GLASS GROUP) discloses a coating device (see page 10, lines 8-31; FIG. 2) comprising two blast pipes directed at 35.degree. maximum with respect to one another, in order that the gaseous flows emerging from these pipes mix progressively with a minimum of turbulence. In addition, for the same purpose, the gaseous blast resulting from the mixing of the above flows is directed onto the substrate to be coated at an angle which does not exceed 60.degree.. Other details on the previous CVD coating methods and devices may be found, for example, in the following references: FR No. 2 083 818; BE No. 877 465; U.S. Pat. No. 3,850,679; FR No. 2 314 152; CH No. 7 033/79.
SUMMARY OF THE INVENTION
It has now been discovered that, on the contrary, it is advantageous in a method for forming a metal oxide coating by CVD to cause at the point of contact a mixing which is as instantaneous as possible of the reagents in the vapor stage, by causing a maximum amount of turbulence and vortical effect of the gaseous flows. It has been noted that deposits formed under such conditions are very uniform and homogeneous, the grains of the deposits are very fine and, in every case, have smaller dimensions than the wave lengths of visible light which eliminates errors due to diffraction. This may be most simply achieved either by causing the said gaseous flows to meet at an angle very different from zero degrees, or by moving them at very different speeds, or by combining these two effects.
What is to be understood by the angle at which the gaseous flows meet is the angle which the displacement vectors of the reagent currents in the vapor phase form with respect to one another at the point of impact. In the invention, this angle is to be at least 35.degree. and preferably between 60.degree. and 180.degree.. What is understood by very different speeds is that one of the gaseous flows moves at least 1.5 to 2 times faster than the other, it being possible for the difference between the two to be much greater, for example 10:1 or even 20:1. Of course, these considerations are equally valid if there are more than two gaseous flows, i.e., for example, if the reaction requires three (or more) independent gaseous reagents or if, in the case of two reagents, these are conveyed to the point of contact by more than two pipes. In a case of this type it is sufficient (but this is not compulsory) f
REFERENCES:
patent: 3511703 (1970-05-01), Peterson
patent: 3524590 (1970-08-01), Myskowski
Baumberger Otto
Kalbskopf Reinhard
Battelle (Memorial Institute)
Dubno Herbert
Lusignan Michael R.
Ross Karl F.
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