| 摘要 |
<p>A method of preparing D.C. electroluminescent phosphor crystals comprises applying stress to photofluorescent, substantially non-D.C. electroluminescent, triboluminescent phosphor crystals, the stress being insufficient to break the crystals but sufficient to extinguish the photofluorescent and triboluminescent properties of the crystals and to make them D.C. electroluminescent. The crystals can be embedded in a viscous film before being stressed and the film can be of a resin which is cured after the crystals have been stressed. The viscous film can contain an epoxy resin, a phenolic resin intermediate, and polyvinyl methyl ether in a weight ratio of about 56 : 32 : 12. The crystals can be sprayed into the film, the later-arriving crystals striking the embedded crystals and stressing them. Alternatively, the embedded crystals can be stressed by spraying them with hard particles which are of a material different from the crystals and which do not react with them, e.g. other phosphors, silicon dioxide, clays, nitrides, carbides and metal particles. In a further example the phosphor crystals, embedded in a resin film, are stressed by an electrical discharge apparatus, such as a Tesla coil. Other methods referred to are the use of ultrasonic waves, overlaying the film containing the crystals with a polymer film and passing a roller over its surface, placing a glass plate over the embedded crystals and applying an angular force, and incorporating the crystals in a vehicle to form a printing medium, the crystals being stressed while the medium is being printed on a substrate. Phosphors referred to are ZnS(Mn), ZnS(Mn, Cl), ZnS(Cu, Mn), ZnS(Pb, Mn), ZnCdS(Mn), ZnCdS(Cu, Mn) and ZnCdS(Pb, Mn). Some of these phosphors also contain KCl, ZnO and a trace of Si.</p> |
