GB1525303A - Phosphor devices - Google Patents

Abstract

1525303 Luminescence and electroluminescence DEFENCE SECRETARY OF STATE FOR 5 March 1976 [7 March 1975] 9664/75 Heading C4S A device includes a visible light emitting phosphor formed of a pentaphosphate compound XP 5 O 14 , where X is a trivalent metal ion, and luminescent sites in the matrix. The luminescent sites may be the sites of the ions X for X ions of Eu or Tb, or X may be non-luminescent in the visible region, and the sites provided by dopant ions, in which case X ions may be Y, Yb, or Pr, and the dopant ions may be Tm, Er, Eu, Tb, or a mixture of Mn and Sb. The matrix may be single crystal, polycrystalline or glass form, and the luminescent ion sites may be in high e.g. stoichiometric, concentrations. Preparation is detailed utilizing heating of oxide(s) with orthophosphoric acid. The phosphor may be a coating 11 on epoxy encapsulant 9 around an infra-red emitting PN device. The coating comprises a solid solution of about 80 to 99% by wt. of, for example, ytterbium pentaphosphate which absorbs the infra-red energy which is transferred by one or more transfer mechanisms to a second visible light emitting pentaphosphate. Coating 11 may be applied as a paste of pentaphosphate powder and a solvent such as nitrocellulose in butyl acetate. The phosphor may be used as a c.r.t. screen layer (13b) (Fig. 2, not shown) deposited as above and covered by alumina layer (13c), or a phosphor (15a) (Fig. 3, not shown) such as TbP 5 O 14 or EuP 5 O 14 may be used in an inert gas discharge tube, low or high vacuum. Phosphor (15a) may be a mixture to produce white emission. The phosphor may be used in a dot matrix display panel having Ne filling for example. An electroluminescent device (Fig. 4, not shown) includes EL layer (22) of a pentaphosphate phosphor in a binder such as p.v.c., between tin oxide and Al electrodes, to which a 500 to 1000 Hz voltage is applied. The phosphor may alternatively contain conducting particles such as Cu, without a binder, and be formed to produce a narrow light emitting region energizable by unidirectional voltages. In an infra-red image converter using several stages of photocathodes and phosphors, the final screen may be the pentaphosphate phosphor. In an X-ray image intensifier using a photocathode both phosphor screens may be a pentaphosphate. In an infrared quantum counter, the pentaphosphate is simultaneously exposed to a D.C. laser output and the infra-red beam to be detected. The infra-red beam may be modulated and the output phase detected. Internal excitation mechanisms in the pentaphosphate are discussed.