Method for improving the performance of low pressure fluorescent discharge lamp which utilizes zinc silicate as a phosphor blend constituent

Claim 1

The method of improving the long-term operating appearance of a low-pressure fluorescent discharge lamp of the type which incorporates a phosphor layer on the envelope interior surface which essentially consists of a mixed homogeneous three-component phosphor blend, said phosphor blend having a red-orange-emitting phosphor component, a blue-violet-emitting phosphor component, and a green-emitting phosphor component, wherein said greenemitting phosphor component is manganese-activated zinc silicate, said lamp having an elongated tubular lighttransmitting vitreous envelope with said homogeneous blend carried as a coating on the interior surface thereof, electrodes operatively positioned proximate the enevelope ends, and a discharge-sustaining filling comprising mercury and inert ionizable starting gas enclosed by said envelope, said method comprising: a. treating or conditioning the zinc silicate phosphor prior to blending said zinc silicate phosphor with said blue-violet-emitting phosphor and said red-orange-emitting phosphor, by washing said zinc silicate phosphor in an aqueous organic acid solution, wherein said organic acid consists of at least one of acetic, succinic and terephthalic; b. separating said acid washed zinc silicate phosphor from said acid washing solution; c. drying said separated zinc silicate phosphor without further water washing of same; d. suspending as a part of an aqueous envelope coating paint which includes suitable binder material, said separated zinc silicate phosphor, said red-orange-emitting phosphor, and said blue-violet-emitting phosphor, with the relative proportions of said phosphors being those as desired in the completed lamp; e. applying the coating paint to the envelope interior surface, thereafter volatilizing aqueous vehicle and residual binder material from the applied paint, leaving the phosphor blend as a homogeneous layer on the envelope interior surface, and thereafter completing the lamp fabrication.

Claim 2

The method of improving the long-term operating appearance of a low-pressure fluorescent discharge lamp of the type which incorporates a phosphor layer on the envelope interior surface which essentially consists of a mixed homogeneous three-component phosphor blend, said phosphor blend having a red-orange-emitting phosphor component, a blue-violet-emitting phosphor component, and a green-emitting phosphor component, wherein said greenemitting phosphor component is manganese-activated zinc silicate, said lamp having an elongated tubular lighttransmitting vitreous envelope with said homogeneous blend carried as a coating on the interior surface thereof, electrodes operatively positioned proximate the enevelope ends, and a discharge-sustaining filling comprising mercury and inert ionizable starting gas enclosed by said envelope, said method comprising: a. treating or conditioning the zinc silicate phosphor prior to blending said zinc silicate phosphor with said blue-violet-emitting phosphor and said red-orange-emitting phosphor, by washing said zinc silicate phosphor in an aqueous organic acid solution, wherein said organic acid consists of at least one of acetic, succinic and terephthalic; b. separating said acid washed zinc silicate phosphor from said acid washing solution; c. drying said separated zinc silicate phosphor without further water washing of same; d. suspending as a part of an aqueous envelope coating paint which includes suitable binder material, said separated zinc silicate phosphor, said red-orange-emitting phosphor, and said blue-violet-emitting phosphor, with the relative proportions of said phosphors being those as desired in the completed lamp; e. applying the coating paint to the envelope interior surface, thereafter volatilizing aqueous vehicle and residual binder material from the applied paint, leaving the phosphor blend as a homogeneous layer on the envelope interior surface, and thereafter completing the lamp fabrication.