Phosphor screen
AssigneeCiba-Geigy Corporation
InventorsAlan Hugh Waller, Peter Charles Sangway
Life of this patent
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Abstract
This invention relates to phosphor screens for converting X-rays into visible or near visible radiation. The screens comprise in a fluorescent layer a phosphor mixture which consists of a fluorohalide corresponding to the formula [Ba.sub.(1.sub.-x.sub.-y.sub.-p) Sr.sub.x Ca.sub.y Eu.sub.p ] F [Cl.sub.(1.sub.-a.sub.-b) Br.sub.a I.sub.b ] (1) wherein y .ltoreq. 0.2 x + y + p .ltoreq. 1 a + b .ltoreq. 1 0.001 .ltoreq. p .ltoreq.0.2 Together with calcium tungstate or an oxychalcogenide of the formula [M.sub.(1.sub.-x) A.sub.x ].sub.2 O.sub.2 Ch (2) wherein M is a rare earth host element, A is a rare earth element different from M and which has an atomic number from 55 to 71, Ch is sulphur, selenium or tellurium and 0.001 .ltoreq. x .ltoreq. 0.2.
Claims10
An X-ray intensifying screen which comprises in a fluorescent layer a phosphor mixture which consists of an alkaline earth fluorohalide activated with divalent europium having the empirical formula
- [Ba.sub.(l.sub.-x.sub.-y.sub.-p) Sr.sub.x Ca.sub.y Eu.sub.p ] F [Cl.sub.(l.sub.-a.sub.-b) Br.sub.a I.sub.b ]
- where
- y .ltoreq. 0.20
- x + y + p .ltoreq. l
- a + b .ltoreq. l
- 0.001 .ltoreq. p .ltoreq. 0.20
- together with at least one phosphor which is either calcium tungstate or which is a rare earth oxychalcogenide having the formula
- [M.sub.(l.sub.-x) A.sub.x ].sub.2 O.sub.2 Ch
- wherein M is at least one rare earth host element, A is an activator which is a rare earth element different from M and which has an atomic number from 59 to 71, Ch is sulphur, selenium or tellurium and 0.001 .ltoreq. x .ltoreq. 0.2.
Dependencies are inferred from the claim text.