Polyimide capacitive humidity sensing element
First Claim
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1. A capacitive humidity sensing element comprising:
- a corrosion resistant metal substrate;
a humidity sensitive polyimide film coated on the corrosion resistant metal substrate; and
a moisture permeable thin gold electrode on top of the humidity sensitive polyimide film, the humidity sensitive polyimide film being produced by reacting;
a dianhydride selected from the group consisting of pyromellitic dianhydride and 3,3'"'"'-4,4'"'"'-benzophenon tetracarboxylic acid dianhydride, witha diamine selected from the group consisting of p-phenylene diamine, m-phenylene diamine, 4,4'"'"'-diamino-diphenyl methane, 4,4'"'"'-diamino-diphenyl ether, 3,4'"'"'-diamino-diphenyl ether and 4,4'"'"'-diamino-diphenyl sulfide.
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Abstract
The present invention relates to a humidity sensing element having a polyimide moisture sensing film. It is of a capacitive structure containing, without the use of adhesives, a polyimide film which is either sandwiched between a corrosion resisting metal substrate and a thin moisture permeable gold layer, or vapor deposited on both sides thereof with a moisture permeable thin gold layer.
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Citations
11 Claims
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1. A capacitive humidity sensing element comprising:
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a corrosion resistant metal substrate; a humidity sensitive polyimide film coated on the corrosion resistant metal substrate; and a moisture permeable thin gold electrode on top of the humidity sensitive polyimide film, the humidity sensitive polyimide film being produced by reacting; a dianhydride selected from the group consisting of pyromellitic dianhydride and 3,3'"'"'-4,4'"'"'-benzophenon tetracarboxylic acid dianhydride, with a diamine selected from the group consisting of p-phenylene diamine, m-phenylene diamine, 4,4'"'"'-diamino-diphenyl methane, 4,4'"'"'-diamino-diphenyl ether, 3,4'"'"'-diamino-diphenyl ether and 4,4'"'"'-diamino-diphenyl sulfide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A process for producing a capacitive humidity sensing element comprising the steps of:
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(i) coating a solution of a dianhydride selected from the group consisting of pyromellitic dianhydride and 3,3'"'"'-4,4'"'"'-benzophenon tetracarboxylic acid dianhydride, and a diamine selected from the group consisting of p-phenylene diamine, m-phenylene diamine, 4,4'"'"'-diamino-diphenyl methane, 4,4'"'"'-diamino-phenylene diamine, 4,4'"'"'-diamino-diphenyl methane, 4,4'"'"'-diamino-diphenyl ether, 3,4'"'"'-diamino-diphenyl ether and 4,4'"'"'-diamino-diphenyl sulfide in a polar solvent onto a corrosion resistant metal substrate; (ii) heating the coated substrate in stages to a temperature between 200° and
300 °
C. until a humidity sensitive polyimide film is formed on the substrate; and(iii) coating a thin gold layer onto the humidity sensitive polyimide film. - View Dependent Claims (11)
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Specification