GB1252787A - - Google Patents

Abstract

1,252,787. Luminecsent screens. INTERNATIONAL BUSINESS MACHINES CORP. 22 Oct., 1969 [22 Nov., 1968], No. 51787/69. Heading C4S. [Also in Division H1] A c.r.t. screen comprises glass substrate 10, thin transparent conductive coatings 12 and 16 and cataphoretically deposited phosphor layers 14 and 18 (e.g. green ZnCdS:Ag and blue ZnS: Ag). Further layers 20 and 22 may be included. A 5000 Š thick 30 to 40 # surface resistant tin oxide antimony doped conductive coating is preferably applied by chemical deposition by spraying on to a 425‹ C. heated screen (e.g. softlead glass) a tin chloride and antimony trichloride solution in a methanol base and in a water vapour atmosphere, then a four (Œ one) micron thick phosphor layre followed by a 400 to 500 Š thick indium oxide conductive layer formed by evaporating indium in water vapour and oxygen on to a 350‹ C. heated screen and a two (Œ one half) micron thick second phosphor layer. The screen is initially washed in detergent, soaked in chromic acid, water washed, soaked in ammonium bifluoride and re-washed. The cataphoretic phosphor deposition, may be from a two micron diameter particle suspension in ethyl alcohol or methyl-isobutyl ketone with 5% water and 10<SP>-4</SP> moles/litre of thorium nitrate or nitric or acetic acid, the vehicle dielectric constant being 30. The third conductive and phosphor layer may be 400 to 500 Š thick indium oxide and two (Œ one half) micron thick europium activated yttrium vanadate phosphor respectively, and may be surmounted by an ion burn resistant Al layer. Overall phosphor thickness of ten microns or less are disclosed as necessary for electron voltages of 18 kV or less. The first conductive layer may alternatively be indium oxide (surface resistance 150 to 200 #/ square), titanium oxide and Ag or Al may be vacuum evaporated for example and subsequently rendered transparent by glow discharge in air. A 1000 Š thick vacuum evaporated Al layer is rendered transparent after subsequent phosphor deposition by oxidation in air or in aqueous ammonium persulphate or anodization by citric acid. Tin, indium or titanium may be applied by vacuum deposition for the second and third coatings.