The Study And Application Of Luminescent Character And Mechanism Of Blue Phosphor ZnS:Zn,Pb Used For FED

The demand for portable, full color display is critically dependent on the development of light weight, low power, flat panel screens. Field emission displays (FED) promise significant advantages for these applications because they have the potential to combine the best properties of cathode ray tube (CRT) and flat panel displays. The field-emitter material and anode phosphors et al are the key elements of a FED. The recent work on field emission cathode has resulted in very efficient electron excitation sources. It should operate between 1 and 10 KV for peak current densities of 10-300 mA/cm². The anode/cathode electron excited efficiency must be over 90%. The operating conditions of a FED places a number of critical requirements on a phosphor: good chromaticity, higher luminance efficiency, low saturation, good aging properties at the low voltages and high current densities et al.To satisfy the luminance and power requirements demands for portable applications, it is urgently demand on very efficient low voltage phosphors. Of particular importance is the need for a good blue phosphor. In this thesis, we reported a new kind of high efficiency blue phosphor ZnS:Zn,Pb for FED application. The followings are some of creative aspects:1. It is showed that the luminescence properties of ZnS:Zn,Pb are strongly dependent on the preparation conditions. The divalent of lead emits green luminescence when heated between 1100℃and 1200℃, which is signed as ZnS:Zn,Pb(green). It sent out blue luminescence when heated between 800℃and 950℃, which was shown as ZnS:Zn,Pb (blue).2. The photoluminescence of ZnS:Zn,Pb, the thermoluminescence of ZnS:Zn,Pb and the lifetime of ZnS:Zn,Pb are investigated in this report. There are some different characters between ZnS:Zn,Pb(green) and ZnS:Zn,Pb (blue). We conclude that these two kinds of phosphors belong to different mechanisms. Different luminescence models are established respectively.3. The cathodeluminescent (CL) properties at low voltages and high current densities for ZnS:Zn,Pb(blue) and ZnS:Ag,Cl are showed contrastively . It was found that ZnS:Zn,Pb is more excellent one. The significant high resistance (>10⁹Ωcm) of ZnS-type phosphors are attributed to its wide band gap. The conductivity need to be improved used for FEDs. The surface coating on ZnS:Zn,Pb is an important technique to improve low-voltage cathodeluminescence(CL) and chemical stability and to reduce outgassing.4 A kind of new blue phosphor ZnS:Pb.Tm is also reported too. It originated from 5d-4f allowed transition of electronic level. The luminescent results approved that it display better properties. On the basis of above research, we try to attempt other blue phosphor such as Sr₅(PO₄)₃Cl:Eu²⁺ and develop a new FED.