Coating processes – Particles – flakes – or granules coated or encapsulated – Solid encapsulation process utilizing an emulsion or...
Patent
1992-07-20
1993-03-23
Cooper, Jack
Coating processes
Particles, flakes, or granules coated or encapsulated
Solid encapsulation process utilizing an emulsion or...
2523015, 2523016F, 427 67, 427215, C09K 1159
Patent
active
051962349
ABSTRACT:
A method for preparing a specific zinc orthosilicate phosphor particle having a nonparticulate, conformal aluminum oxide coating wherein all of a manganese activator is present as manganese (II) and occupies zinc (II) sites includes the steps of blending a zinc source, a manganese (II) source, a silicon source, and a tungsten source in amounts in accordance with said formula with an amount of up to about 2 weight percent NH.sub.4 Cl and up to about 0.2 weight percent NH.sub.4 F to form a relatively uniform admixture, firing the mixture in a closed container under an inert non-oxidizing atmosphere to promote retention of manganese in the plus two valance state whereby oxidation of manganese to a higher valence state is avoided and conditions promote larger particle size formation; milling and washing the phosphor in an aqueous citric acid solution to remove unreacted manganese; rinsing, drying and sieving the dried phosphor; and depositing a continuous, nonparticulate, conformal aluminum oxide coating on the dried phosphor particle.
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Chenot Charles F.
Minnier Henry B.
Sigai A. Gary
Taubner Fred R.
Cooper Jack
GTE Products Corporation
Walter Robert E.
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