Electroluminescent phosphors

A review of the properties of electroluminescent phosphors of the zinc sulfide family is presented. In the past, these phosphors found few device applications because of material limitations that resulted in inadequate brightness and poor life as well as drive problems. The properties of two particular configurations are discussed in detail: ac-excited evaporated films of Zns:Mn and dc-excited powder layers of ZnS:Mn, Cu. These configurations exhibit such properties as high efficiency, low-duty-cycle operation, high contrast, high discrimination ratio, and acceptable operating lifetimes. In addition, the basic technology can result in inexpensive and rugged devices, which may be fabricated in unlimited symbol configurations and in a wide range of sizes. It is concluded that such technology offers potential advantages to display systems and should be considered viable candidates to satisfy future display requirements, especially in cases where cost effectiveness and ruggedness are overriding restrictions.