Patent GB-1018474-A (GB)
Title: Method of preparing electroluminescent phosphors and electroluminescent devices
IPC: H05B33/14
Filed: 1962-08-30
Abstract: In the two-step process of preparing zinc sulphide electroluminescent phosphors, in which an activated ordered non-electroluminescent phosphor is produced by a first firing step, followed by a second firing step which introduces sufficient disorder to produce electroluminescence, the second firing step is combined with the process of embedding the phosphor in its dielectric carrier material, e.g. the so-called ceramic dielectric formed from glass frit.  A two-step process is stated to be known in which the activator is contained in the frit, so that the first fired product is not activated.  If the first ordered phase is the cubic one, the first firing is below 1020 DEG  C., preferably 500-1000 DEG  C., and the second firing is above 1020 DEG  C., preferably 1050-1300 DEG  C., to produce hexagonal disorder; if the first ordered phase is hexagonal, these ranges are reversed. The activators are usually copper, manganese, silver, arsenic or bismuth, but lead, calcium, aluminium, lithium, gallium, indium, boron, lanthanum, cerium, praseodymium or neodymium may be used; the percentage is 0.001-5.0, preferably 1.0. Fluxes (at 3-12%) may be potassium, sodium, magnesium or barium chloride.  The frits may have the percentage compositions (a) 19.4 SiO2, 26.6 B2O3, 4.7 Al2O3, 2.0 TiO2, 9.6Na2O, 0.6 K2O, 0.5 Li2O, 3.6 CaO, 4.2 BaO, 26.8 ZnO, 2.0 F2, (b) 22.7 SiO2, 23.3 B2O3, 4.1 Al2O3, 2.3 TiO2, 8.3 Na2O, 0.4 Li2O, 4.8 CaO, 3.5 BaO, 25.2 ZnO, 3.4 F2, 2.0 As2O3, or (c) 25.8 SiO2, 26.6 B2O3, 9.4 Na2O, 5.5 CaO, 4.0 BaO, 28.7 ZnO.  The mixture for second firing may contain 5-95%, preferably 30%, of phosphor and is coated in a liquid vehicle on a base of metal or electrically-conducting glass or on another previously-fired dielectric layer of fused frit.  The firing time is 1-10 minutes. A tin chloride coating is then sprayed on to the electroluminescent layer.ALSO:In the two-step process of preparing zinc sulphide electroluminescent phosphors, in which an activated ordered non-electroluminescent phosphor is produced by a first firing step, followed by a second firing step which introduces sufficient disorder to produce electroluminescence, the second firing step is combined with the process of embedding the phosphor in its dielectric carrier material, e.g. the so-called ceramic dielectric formed from glass frit.  A two-step process is stated to be known in which the activator is contained in the frit, so that the first fired product is not activated.  If the first ordered phase is the cubic one, the first firing is below 1020 DEG  C., preferably 500-1000 DEG  C., and the second firing is above 1020 DEG  C., preferably 1050-1300 DEG C., to produce hexagonal disorder; if the first ordered phase is hexagonal, these ranges are reversed. The activators are usually copper, manganese, silver, arsenic or bismuth, but lead, calcium, aluminium, lithium, gallium, indium, boron, lanthanum, cerium, praseodymium or neodymium may be used; the percentage is 0.001-5.0, preferably 1.0. Fluxes (at 3-12%) may be potassium, sodium, magnesium or barium chloride.  The frits may have the percentage compositions (a) 19.4 SiO2, 26.6 B2O3, 4.7 Al2O3, 2.0 TiO2, 9.6 Na2O, 0.6 K2O, 0.5 Li2O, 3.6 CaO, 4.2 BaO, 26.8 ZnO, 2.0 F2; (b) 22.7 SiO2, 23.3 B2O3, 4.1 Al2O3, 2.3 TiO2, 8.3 Na2O, 0.4 Li2O, 4.8 CaO, 3.5 BaO, 25.2 ZnO, 3.4 F2, 2.0 As2O3, or (c) 25.8 SiO2, 26.6 B2O3, 9.4 Na2O, 5.5 CaO, 4.0 BaO, 28.7 ZnO.  The mixture for second firing may contain 5-95%, preferably 30%, of phosphor and is coated in a liquid vehicle on a base of metal or electrically-conducting glass or on another previously-fired dielectric layer of fused frit. The firing time is 1-10 minutes.  A tin chloride coating is then sprayed on to the electroluminescent layer.