Patent Number: 047330899
Section: summary

This invention relates to a radiographic intensifying screen and a process for the preparation of the same. More particularly, this invention relates to a radiographic intensifying screen comprising a support and at least one phosphor layer comprising a binder and a phosphor dispersed therein, and a process for the preparation of the same. The radiographic intensifying screen is generally employed in close contact with one or both surfaces of an X-ray film for enhancing the photographic sensitivity of the film in a variety of radiographys such as medical radiography and industrial radiography. The radiographic intensifying screen consisits essentially of a support and a phosphor layer provided thereonto. Further, a transparent film is generally provided onto the free surface of the phosphor layer to keep the phosphor layer from chemical and physical deterioration. The phosphor layer comprises a binder and a phosphor dispersed therein. The phosphor is in the form of small particles, and emits light of high luminance when excited by radiation such as X-rays. The light of high luminance emitted by the phosphor is in proportion to the dose of radiation energy transmitted through an object. The X-ray film positioned in close contact with the intensifying screen is exposed to the light emitted by the phosphor layer, as well as being exposed directly to the radiation energy transmitted through the object. Accordingly, the X-ray film receives radiation energy enough for formation of the radiation image of the object, even if the radiation is applied to the object at a relatively small dose. In view of the above-described characteristics of the radiographic intensifying screen, it is desired that the screen shows a high radiographic speed, as well as provides excellent image characteristics such as sharpness and graininess. For the reason, various proposals have been previously given for the improvement of radiographic speed and image characteristics of the radiographic intensifying screen. For instance, U.S. Pat. No. 4,207,125 describes an X-ray intensifying screen including an anti-reflecting surface at the back side of the luminous layer in which a plurality of randomly positioned leaflets extend from the surface, in which the layer is typically formed of a microstructured layer of boehmite, a hydrated aluminum oxide. U. S. Pat. No. 4,236,061 describes an image intensifying screen comprising an antireflecting surface formed by subjecting a substantially planner aluminum surface on a support layer to a steam treatment to convert the aluminum surface to a microstructured surface of boehmite, a hydrated aluminum oxide, having a plurality of randomly positioned leaflets extending from the surface. The radiographic intensifying screen also is ought to be so mechanically strong enough to keep itself from separation between the support and the phosphor layer when receives mechanical shocks such as bending in the course of radiographic procedures. The intensifying screen is chemically and physically resistant to radiographic rays, whereby the screen is employable for a long period even under the conditions of repeated uses. For this reason, the screen ought to be resistant to mechanical shocks given in the procedure for changing an X-ray film or other procedures so that it is free from separation between the support and the phosphor layer. Accordingly, a primary object of the present invention is to provide a radiographic intensifying screen improved in the sharpness, and a process for the preparation of the same. Another object of the invention is to provide a radiographic intensifying screen improved in the mechanical strength, particularly, strength in the adhesion between the support and the phosphor layer, and a process for the preparation of the same. There is provided by the invention a radiographic intensifying screen comprising a support and at least one phosphor layer comprising a binder and a phosphor dispersed therein, in which the support is provided on the surface facing the phosphor layer with a great number of pits having a mean depth of at least a maximum depth of more than 1 .mu.m to 100 .mu.m and a mean diameter at the opening of at least 1 .mu.m. The radiographic intensifying screen of the invention can be prepared by a process comprising applying hard solid particles onto the surface of the support at high speed to form the pits.