Patent GB-1317731-A (GB)
Title: Electroluminescent apparatus
IPC: G02F2/02
Filed: 1970-04-16
Abstract: 1317731 Electroluminescence WESTERN ELECTRIC CO Inc 16 April 1970 [16 April 1969] 18161/70 Heading C4S Electroluminescent apparatus producing visible radiation include an infra-red emitting PN diode coated with an oxyhalide and/or fluorohalide phosphor 8 containing Yb<SP>3+</SP>-Er<SP>3+</SP> and with either at least 2 anion sites/unit cell differently populated in at least one per cent of the unit cells, or at least one anion vacancy/unit cell in at least one per cent of the cells. The phosphor contains either <SP>1/</SP>16 to 20 cation per cent Er<SP>3+</SP> and 5 to 50 cation per cent Yb<SP>3+</SP>, or <SP>1/</SP>16 to 20 cation per cent Er<SP>3+</SP> with <SP>1/</SP>50 to 5 cation per cent Ho<SP>3+</SP> and #5 cation per cent Yb<SP>3+</SP>, the infra-red to visible conversion being by at least a two excitation process each producing a different emission wavelength and each process involving a multiphoton process which is at least a two stage excitation, and means, including a rheostat 10 connected to ring cathode 6 for example, to alter the power level of the infra-red radiation to vary the relative amounts of visible radiations. A minimum 10% of Yb<SP>3+</SP> is preferred,  % Er<SP>3+</SP>, <2% Er<SP>3+</SP>, # 2% Ho<SP>3+</SP> also being instanced for example. Diodes of GaP are exemplified with O and/or N dopants emitting red and/or green, the red emission, unlike the green, saturating with input power. Known GaAs devices are also discussed. Fig. 2 (not shown), illustrates excitations and emissions, most closely representative of YOCI and Y 3 OCl 7 , specific wavelengths being instanced, a Si doped GaAs diode also being specified and internal excitation mechanisms in phosphor 8 being discussed. Embodiments include powder or polycrystalline phosphors, oxychlorides (e.g. of rare earths including yttrium) being prepared by dissolving oxides in HCl, evaporating to form hydrated chlorides, dehydrating, (e.g. 100 C. under vacuum), and treating with Cl 2  gas at 900 C. Included trichloride may act as flux to crystallize the oxychlorides and is removed by water washing. Oxybromides and-iodide preparation utilizes hydrobromic acid, gaseous HBr and hydroiodic acid and gaseous HI. Lead or alkaline earth fluorochlorides and fluorobromides may be prepared by melting halides together which may then be melted with oxyhalide phosphors. Many specific phosphors are disclosed, oxychlorides being preferred of oxychlorides, -bromides and-iodides (e.g. of rare earths including Y), and mixtures of oxyhalides with fluorohalides. Oxychlorides include at least two stoichiometrics according to Cl : O ratios, compositions, and lattice spacings being discussed. Cl : O ratios of approximately 1 and >1, e.g. 1À5, are instanced. Diluent cations such as Y, Pb<SP>2+</SP>, Gd<SP>3+</SP> and Lu<SP>3+</SP> may be included, and purity levels should normally be 99À9% or five nines purity. Glass and plastics encapsulants may provide environmental protection, e.g. a 25 mm. junction with 72 mm. dome with a 2 mm. thick phosphor film in collodion as binder. Means promoting adhesion and minimizing scattering are preferably included and communication and computer applications are instanced. Specification 1,317,732 is referred to.