Radiant energy – Invisible radiation responsive nonelectric signalling – Luminescent device
Reexamination Certificate
2000-09-21
2002-05-28
Sugarman, Scott J. (Department: 2873)
Radiant energy
Invisible radiation responsive nonelectric signalling
Luminescent device
C250S580000
Reexamination Certificate
active
06396066
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to radiographic articles used in radiographic imaging. More particularly, it relates to coated radiographic phosphors and radiographic image storage phosphor panels useful in radiographic imaging.
BACKGROUND OF THE INVENTION
Radiographic phosphor panels generally contain a phosphor layer on a suitable support. Phosphors are crystalline materials that respond to X-radiation (X-rays) on an imagewise basis. Like many other crystalline materials, radiation phosphors have a crystal matrix that allows for the replacement of some atoms by other similar atoms, but does not accept other atoms or moieties. Radiographic phosphor panels can be classified based upon their phosphors, as prompt emission panels (or intensifying or conversion panels) and image storage panels. Both types of panels are also known in the art as “screens”.
Image storage panels comprise storage phosphors that have the capability of storing latent X-rays for later release, apparently by locally trapping electron-hole pairs created by incident X-rays. Storage phosphors are distinguishable from the phosphors used in intensifying or conversion panels. In the intensifying or conversion panels, a latent image is not stored but X-rays cause an immediate release of visible light from irradiated phosphor crystals.
Radiation storage panels are used in computed radiography. The panel is first exposed to X-rays to create a latent image. The panel is then stimulated with longer wavelength radiation, resulting in the emission of radiation at a third wavelength. Typically a laser having a red or infrared beam is scanned over the panel, resulting in the emission of green or blue radiation. The emitted radiation is then collected and the resulting signal is processed electronically to produce a final image.
Radiographic panels or screens comprise a support, a luminescent layer that includes the radiographic phosphor, and optionally an overcoat layer to protect the phosphor layer from mechanical damage due to scratches and abrasion. An overcoat layer is desirably, substantially clear and transparent to the radiation emitted by the radiation phosphor.
The radiographic panel support is typically a flexible material such as a polymeric film such as a poly(ethylene terephthalate) or cellulose acetate film, or a cellulosic material such as paper or cardboard. The support provides the required stiffness for the radiographic panel so it can stand any physical abuse during use. In these cases, a relatively thick support provides the desired stiffness. While such support materials can be manufactured, the manufacturing process is difficult and unpredictable in yielding the desired properties such as optical clarity. That is, they are usually too hazy. Such supports are not ideal for radiographic panels because the haze can scatter impacting laser radiation causing a sufficient loss in image resolution.
This problem can be remedied by coating a layer on the support that will absorb the laser radiation under the phosphorescent layer, but this adds additional coating steps and can create adhesion problems. One might also coat the absorbing layer on the back of the support, but in the case of a light-scattering support, this location is also ineffective.
Thus, there is a need to provide radiographic storage panels that have optically clear flexible supports that can be easily fabricated to have the desired thickness.
SUMMARY OF THE INVENTION
This invention provides a radiographic storage panel comprising a support having thereon a storage phosphor layer, the support comprising two or more flexible substrates adhered to each other.
Another embodiment of this invention is a radiographic storage panel having an overcoat layer over a storage phosphor layer, which storage phosphor layer is disposed on a support comprising two or more flexible substrates adhered to each other.
Further, this invention provides a radiographic assembly comprising a light-tight container having therein the radiographic storage panel described above.
The radiographic panels of this invention exhibit a number of advantages. They comprise a support that is optically clear and suitably flexible for the intended properties. Supports of various materials can be prepared to have varying thickness by varying the number of laminated or adhered flexible substrates and their individual thickness. The choice of substrate materials, adhesive and laminating parameters also allow considerable flexibility to control curl while providing the desired optical clarity, thickness and durability. It may also be advantageous to use a colored adhesive or laminated substrates to adjust image quality.
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AGFA Technical Bulletin, “ADC Imaging Plate”, Jun., 1997.
Chen Wen-Li A.
Chipouras Arthur P.
Heath Terry A.
Mruk William A.
Steklenski David J.
Hasan Mohammed
Sugarman Scott J.
Tucker J. Lanny
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