Method of electrophotographically manufacturing a luminescent screen for a color CRT having a conductive contact patch

In a method of electrophotographically manufacturing a luminescent screen on a substrate of a color CRT comprising the steps of:

• a) forming a photoreceptor by coating a surface of said substrate with a first solution to form a volatilizable conductive layer and overcoating said conductive layer with a second solution to form a volatilizable photoconductive layer;
• b) establishing a substantially uniform electrostatic charge on said photoconductive layer;
• c) exposing selected areas of said photoconductive layer to visible light to affect the charge thereon;
• d) developing selected areas of said photoconductive layer with a triboelectrically charged, dry-powdered, first color-emitting phosphor material;
• and
• e) sequentially repeating steps b, c and d for triboelectrically charged, dry-powdered, second and third color-emitting phosphor materials to form a luminescent screen comprising picture elements of triads of color-emitting phosphor materials:
• wherein the improvement comprises providing at least one wear-resistant conductive contact patch on a peripheral portion of said surface of said substrate, said contact patch having a first portion underlying at least one of said layers of said photoreceptor and in electrical contact therewith and a second portion extending therefrom;
• grounding said contact patch during step b) to facilitate the establishing of said charge on said photoconductive layer;
• and
• contacting said contact patch during step d) with suitable measuring means to monitor the deposition of said triboelectrically charged phosphor materials on said photoconductive layer.

In a method of electrophotographically manufacturing a luminescent screen assembly on an interior surface of a faceplate panel for a color CRT having a viewing area and a peripheral sidewall with mask mounting means on said sidewall, the method comprising the steps of:

• a) coating said interior surface of said panel with a first solution to form a volatilizable conductive layer;
• b) overcoating said conductive layer with a second solution to form a volatilizable photoconductive layer;
• c) establishing a substantially uniform electrostatic charge on said photoconductive layer;
• d) exposing, through a mask secured to said mask mounting means, selected areas of said photoconductive layer to visible light from a lamp to affect the charge on said photoconductive layer;
• e) directly developing the unexposed areas of the photoconductive layer with a triboelectrically charged, dry-powdered, surface-treated, light-absorptive screen structure material, the charge on said screen structure material being of opposite polarity to the charge on the unexposed areas of the photoconductive layer;
• f) reestablishing a substantially uniform electrostatic charge on said photoconductive layer and on said screen structure material;
• g) exposing, through said mask secured to said mask mounting means, first portions of said selected areas of said photoconductive layer to visible light from said lamp to affect the charge on said photoconductive layer;
• h) reversal developing of the first portions of said selected areas of said photoconductive layer with a triboelectrically charged, dry-powdered, first color-emitting phosphor screen structure material having a charge of the same polarity as that on the unexposed areas of said photoconductive layer and on said light-absorptive screen structure material to repel said first color-emitting phosphor therefrom;
• i) sequentially repeating steps f, g and h for second and third portions of said selected areas of said photoconductive layer using triboelectrically charged, dry-powdered, second and third color-emitting phosphor screen structure materials, thereby forming a luminescent screen comprising picture elements of triads of color-emitting phosphors;
• wherein the improvement comprises providing at least one wear-resistant conductive contact patch on said peripheral sidewall adjacent to said viewing area prior to coating said interior surface of said panel with said first solution forming said volatilizable conductive layer, said contact patch having a first portion underlying a portion of said conductive layer and in electrical contact therewith and a second portion extending beyond said conductive layer, said contact patch being insoluble in said first solution;
• grounding said contact patch during step c) to facilitate establishing said charge on said photoconductive layer;
• and
• contacting said patch during steps e) and h) with suitable measuring means to monitor the deposition of said triboelectrically charged materials on said photoconductive layer.

In a method of electrophotographically manufacturing a luminescent screen assembly on an interior surface of a faceplate panel for a color CRT having a viewing area and a peripheral sidewall with mask mounting means on said sidewall, the method comprising the steps of:

• a) coating said interior surface of said panel with a first solution to form a volatilizable conductive layer;
• b) overcoating said conductive layer with a second solution to form a volatilizable photoconductive layer;
• c) establishing a substantially uniform electrostatic charge on said photoconductive layer;
• d) exposing, through a mask secured to said mask mounting means, selected areas of said photoconductive layer to visible light from a lamp to affect the charge on said photoconductive layer;
• e) directly developing the unexposed areas of the photoconductive layer with a triboelectrically charged, dry-powdered, surface-treated, light absorptive screen structure material, the charge on said screen structure material being of opposite polarity to the charge on the unexposed areas of the photoconductive layer;
• f) reestablishing a substantially uniform electrostatic charge on said photoconductive layer and on said screen structure material;
• g) exposing, through said mask secured to said mask mounting means, first portions of said selected areas of said photoconductive layer to visible light from said lamp to affect the charge on said photoconductive layer;
• h) reversal developing of the first portions of said selected areas of said photoconductive layer with a triboelectrically charged, dry-powdered, first color-emitting phosphor screen structure material having a charge of the same polarity as that on the unexposed areas of said photoconductive layer and on said light-absorptive screen structure material to repel said first color-emitting phosphor therefrom;
• i) sequentially repeating steps f, g and h for second and third portions of said selected areas of said photoconductive layer using triboelectrically charged, dry-powdered, second and third color-emitting phosphor screen structure materials, thereby forming a luminescent screen comprising picture elements of triads of color-emitting phosphors;
• wherein the improvement comprises providing at least one wear-resistant conductive contact patch on said peripheral sidewall adjacent to said viewing area subsequent to coating said interior surface of said panel with said first solution forming said volatilizable conductive layer, said contact patch having a first portion overlying a portion of said conductive layer and in electrical contact therewith and a second portion extending beyond said conductive layer;
• grounding said contact patch during step c) to facilitate establishing said charge on said photoconductive layer;
• and
• contacting said patch during steps e) and h) with suitable measuring means to monitor the deposition of said triboelectrically charged materials on said photoconductive layer.