Coating processes – Electrical product produced – Welding electrode
Patent
1984-11-21
1986-10-21
Pianalto, Bernard D.
Coating processes
Electrical product produced
Welding electrode
427123, 4271263, 427422, 427427, B05D 312
Patent
active
046185089
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process and apparatus for producing composite layers. It more particularly applies to producing electrodes for liquid medium display cells and transparent heating members, e.g. making it possible to deice panes of glass.
Process are known which make it possible to produce composite layers, e.g. constituted by a first tin-doped indium oxide layer, deposited on an e.g. glass substrate, and by a second fluorine-doped or antimony-doped tin oxide layer deposited on the first layer.
A first process consists of depositing the first layer by radio-frequency cathodic sputtering, then performing a vacuum annealing of said first layer, followed by the deposition of the second layer, also by radio-frequency cathodic sputtering.
This first process suffers from the disadvantage of requiring a heat treatment (vacuum annealing) following the deposition of the first layer, which reduces the resistivity of the said layer to values compatible with the envisaged applications for the composite layers in question. The object of this vacuum thermal annealing is to increase the stoichiometry difference, the main element of the conductivity of these oxides.
A second process consists of depositing the first layer by the reactive chemical spraying of aerosols obtained ultrasonically or pneumatically on to the substrate in a known apparatus provided for this purpose, and at a temperature exceeding ambient temperature, which is roughly 20.degree. C. From the said apparatus is then removed the assembly constituted by the substrate and the first layer and said assembly is then brought into the open air, where it is cooled to ambient temperature. The assembly is then placed in the apparatus again and the second layer deposited by reactive chemical spraying of aerosols obtained ultrasonically or pneumatically, after previously reheating the substrate and the first layer.
Due to the known apparatus used in the performance thereof, the second process suffers from the disadvantage of requiring separate depositions of two layers, with a return to air (at ambient temperature) after depositing the first layer. Thus, it does not make it possible to obtain tin-doped indium oxide layers with a low electrical resistivity, i.e. an electrical resistivity at the most equal to 2.5.multidot.10.sup.-4 .OMEGA..multidot.cm. As a matter of fact the electrical properties of the first layer are affected by the reduction in the stroichiometry difference of the indium oxide, resulting from the air oxidization of the first layer during its cooling or its reheating prior to the deposition of the second layer.
The object of the present invention is to obviate the aforementioned disadvantages by proposing a process and an apparatus making it possible to produce conductive composite layers with a low electrical resistivity and without heat treatment. More generally, the present invention aims at obviating the disadvantages of the known process for producing composite layers, in which certain physical properties, such as the electrical resistivity are modified during the production of said layers, e.g. by oxidation.
More specifically, the present invention relates to a process for producing composite layers, constituted by a first layer and at least one further layer, produced from chemical compounds, the layers being superimposed, said process consisting of successively depositing the layers on top of one another, the first layer being deposited on a substrate, characterized in that each layer is deposited immediately following the preceding layer and in that the depositions of the layers are performed by reactive chemical spraying and at temperatures determined by the compounds to be deposited, a chemically inert atmosphere being maintained between each deposition.
Any modification to the physical properties of the thus deposited layers is prevented by maintaining a chemically inert medium between each layer deposition. The term "chemically inert medium or atmosphere" is understood to mean e.g. a nitrogen or a rare gas atmosphere.
REFERENCES:
Patents Abstracts of Japan, vol. 1, No. 126, 10/20/77, p. 5480E77, & JP, A, 5259888 (Denki).
Thin Solid Films, vol. 77, No. 1-3, Elsevier Sequoia (NL) G. Blandenet et al., "Thin Layers Deposited by the Pyrosol Process", pp. 81-90.
Blandenet Gerard
Chazee Jean-Jacques
Court Michel
Commissariat a l''Energie Atomique
Pianalto Bernard D.
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