定電流電気泳動被覆法によるブラウン管ヒーター用アルミナ多孔質膜の形成

概要

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Electrophoretic coating by a constant current deposition method (CCDM) was conducted to form alumina insulation layers on the tungsten double helical filaments of a CRT heater. Alumina particles (average diameter of about 4 μm) were dispersed in an ethanol water suspension containing dehydrated Al (N0_3)_3 + Mg (N0_3)_2-6H_20. Positively charged alumina particles in the suspension (43 mass% solid ) were deposited on tungsten double helical filaments by passing a direct current from 0.015 to 0.32 A. The thickness and packing ratio of Al_20_3 film formed within the spaces between the coils of the double helical filaments were measured after deposition under various CCDM conditions. A gel like substance with a uniform thickness was deposited on the overall surface of the electrode of the tungsten helical heater by passing the constant cur rent. Better current conditions of the CCDM for achieving Al_20_3 packing ratio above 55% were 0.05 A<I < 0.12 A. The thickness of the Al_20_3 film did not reach 75 μm because a long range deposition time for the CCDM caused surface roughness above 20 μm. Use of a double step CCDM for a practical process was examined to give an Al_20_3 film thickness over 100 μm and Al_20_3 packing ratio of over 55%. A typical condition for double step CCDM was I= 0.08A for 10 s as the first step and I=0.5 A for 3.0 s as the second step.
社団法人日本セラミックス協会の論文
1995-01-01