| 摘要 |
1,175,040. Luminescent materials. DAI NIPPON TORYO K.K. 31 Aug., 1966 [12 July, 1966], No. 27877/69. Divided out of 1,168,074. Heading C4S. Rare earth oxyacidate phosphor particles have a surface coating of acidic oxide of B, Al, V, Ga, Ge, As, Nb, Mo, Sn, Sb, Tn or W. The coating may be applied by mixing preferably in a liquid medium the phosphor and the oxide or a compound which on heating forms the oxide, e.g. hydroxides, carbonates, sulphides and NH 4 oxyacidates. The mixture is heated causing the oxide to melt, some of the oxide may diffuse on to the surface of the phosphor particle reacting to form an adhering intermediate layer. The particles may be coated by mixing the oxide suspended in an aqueous or non-aqueous dispersion and the particles and then drying. An hydroxide can first be deposited by adding a solution of the salt to a phosphor suspension and adjusting the pH value then heating to convert the hydroxide to oxide. A further method is to add the oxide to a slurry comprising an aqueous phosphor suspension and PVA. YVO 4 : Eu is coated with GeO 2 by heating a suspension of YVO 4 : Eu in GeS 2 , water and HC1. Slurries containing the coated particles were prepared using PVA and NH 4 bichromate sensitizer for photoprinting colour TV screens. |
