A phosphor panel favorably employable for medical diagnosis of chest has a phosphor layer formed on a substrate by a gas phase-accumulation method, in which the phosphor layer is composed of a large number of phosphor columns standing parallel to each other, in which the phosphor columns have a mean diameter of 0.1 to 50 μm at a top surface thereof, and there are no phosphor columns having a diameter larger than 200 μm at the top surface.
1. A process for preparation of the phosphor panel formed on a substrate by a gas phase-accumulation method, wherein the phosphor layer comprises a large number of phosphor columns standing parallel to each other, in which the phosphor columns have a mean diameter in the range of 0.1 to 50 μm at a top surface thereof, and there are no phosphor columns having a diameter larger than 200 μm at the top surface,
comprising the steps of:
placing, in a vacuum evaporation-deposition apparatus, a container containing an evaporation source containing phosphor or a constitutional materials thereof,
evacuating the evaporation-deposition apparatus to set an inner atmosphere thereof at a pressure in the range of 0.1 to 10 Pa,
preheating the container to melt whole evaporation source at the above-mentioned pressure range, and
vaporizing the evaporation source to deposit on a substrate a phosphor layer having predetermined thickness.
2. The process of claim 1 wherein at least two evaporation sources are used, in which one of the sources contains compounds for forming matrix of the phosphor and the other contains an activator of the phosphor, comprising the steps of:
preheating at least one evaporation source for forming matrix to melt completely the evaporation source, and
vaporizing both of the evaporation source for forming matrix and evaporation source containing an activator to deposit on the substrate a phosphor layer having predetermined thickness.
3. The process of claim 1 , wherein the step of preheating the container to melt whole evaporation source is performed under such condition that a temperature of the evaporation source at a center area differs from a temperature of the evaporation source at a peripheral area by not larger than 30° C.
4. The process of claim 1 , wherein the step of vaporizing the evaporation source is performed by means of a resistance-heater.
5. The process of claim 1 , wherein particles of the vaporized evaporation source come into collision with an atmospheric gas molecule in the evaporation-deposition apparatus at 1 to 1,000 times before the particles are deposited on the substrate.