| 摘要 |
PROBLEM TO BE SOLVED: To suppress corrosion in a heat resistance film by using an insulating damp-proof layer that at least includes insulating damp-proof material and particles comprising insulating bodies of a specified particle size or greater, and in which the amount of these particles included is a specified percentage of the volume of the insulating damp-proof layer. SOLUTION: A heat resistance film 2 is formed on the back face of a mirror base plate 1. On the back face of the heat resistance film 2, at least one pair of opposing electrodes 3a, 3b are provided in order to pass current through this heat resistance film 2. Above the heat resistance film 2, an insulating damp- proof layer 4 is formed in order to prevent any short circuit between the heat resistance film 2 and external objects, and also to prevent corrosion of the heat resistance film 2 and the electrodes 3a, 3b. This insulating damp-proof layer 4 is formed by applying a coat of insulating damp-proof material on top of the heat resistance film 2 and drying it. It includes at least insulating damp-proof material and particles made up of insulating bodies with a particle size of 10μm or greater, with a percentage by volume of these particles of 20 to 70% within the insulating damp-proof layer.
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