| 摘要 |
PROBLEM TO BE SOLVED: To obtain an infrared-excitable fluorescent material fully improved in humidity resistance. SOLUTION: By surface-treating an infrared-excitable phosphor represented by the formula: R<1> x R<2> (1-x) Baz Cl3+2z (wherein R<1> is a rare earth element; 0.01<x<=1; R<2> is a rare earth element except R<1> ; and 1<z<4) which a gaseous sulfonating agent or the like, an infrared-excitable fluorescent material having a sulfate layer on the surface and sufficiently improved in humidity resistance can be obtained. The gaseous sulfonating agent is exemplified by gaseous sulfur trioxide or a gaseous sulfur dioxide. It is desirable that the sulfate layer formed on the surface of the infrared-excitable phosphor by surface treatment has a thickness of 1-100μm, and that in the formula: R<1> x R<2> (1-x) Ba2 Cl3+2z , R<1> is at least one member selected among Er, Tm, Ho, Nd, Pr and Dy; and R<2> is at least one member selected among Yb, Gd, Y, Lu, Eu, Ce and La. |
