Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
1999-02-10
2001-08-21
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S370090, C250S367000
Reexamination Certificate
active
06278118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation detection device; and, in particular, to a radiation detection device having a light-receiving portion with a large area, which is used for medical x-raying and the like.
2.Related Background Art
While X-ray sensitive films have conventionally been used for medical and industrial X-raying, radiation imaging systems using a radiation detection device are becoming pervasive due to their convenience and the storability of their photographed results. Such a radiation imaging system uses a radiation detection device having a plurality of pixels so as to acquire, as an electric signal, two-dimensional image data formed by a radiation, and processes thus obtained with a signal processing unit, so as to display it on a monitor. A typical radiation detection device is configured such that a scintillator is disposed on one- or two-dimensionally arranged photodetectors so as to convert the incident radiation into light, which is then detected.
Cesium Iodide (CSI), a typical scintillator material, is a hygroscopic material which dissolves by absorbing vapor (moisture) in the air. As a result, characteristics of the scintillator, such as resolution in particular, have disadvantageously deteriorated.
One radiation detection device having a structure for protecting the scintillator against moisture is the technique disclosed in Japanese Patent Application Laid-Open No. 5-196742. In this technique, a water-impermeable moisture-proof barrier is formed on the upper side of the scintillator layer, thereby protecting the scintillator against moisture.
SUMMARY OF THE INVENTION
In the above-mentioned technique, however, it is hard for the moisture-proof barrier in the outer peripheral portion of the scintillator layer to come into close contact with the substrate of the radiation detection device. For example, in a radiation detection device having a large area used for chest X-raying or the like, due to its long outer peripheral portion, there is a fear of peeling off the moisture-proof barrier. Hence, the hermetic sealing of the scintillator layer might become incomplete, moisture penetrates into the scintillator layer, it might cause a problem that deteriorates characteristics of the scintillator layer.
Also, the above-mentioned technique discloses a method of making a moisture seal layer for the moisture-proof barrier in which a silicone potting material or the like is coated on the scintillator layer in a liquid state or coated inside a window member disposed on the light-receiving surface side of the radiation detection device and then the window member is disposed on the scintillator layer before the moisture seal layer is dried, thereby fixing the moisture seal layer. In this method, it is hard to uniformly form the moisture seal layer on a scintillator layer having an irregular surface form, whereby adhesion may deteriorate. This phenomenon tends to occur in radiation detection devices having a large area, in particular.
In view of the foregoing problems, it is an object of the present invention to provide a radiation detection device having a uniform protective film, which is easy to make, for protecting the scintillator against moisture; and a method of making the same.
In order to achieve this object, the radiation detection device of the present invention comprises: (1) a light-receiving device array in which a plurality of light-receiving devices are one- or two-dimensionally arranged on a substrate to form a light-receiving portion, and a plurality of bonding pads electrically connected to the light-receiving devices in respective rows or columns of the light-receiving portion are disposed outside the light-receiving portion; (2) a scintillator layer, deposited on the light-receiving devices, for converting a radiation into detectable light with the light-receiving device; (3) a radiation-transmittable, moisture-resistant protective film covering at least the scintillator layer and exposing at least the bonding pad portion of the light-receiving device array; and (4) a coating resin coated on the moisture-resistant protective film along an edge acting as a boundary portion with respect to an exposed portion of the light-receiving device array so as to bring the edge of the moisture-resistant protective film into close contact with the light-receiving device array.
As a consequence, the incident radiation is converted into detectable light with the light-receiving device by the scintillator layer. As the resulting light image is detected by the one- or two-dimensionally arranged light-receiving devices, an electric signal corresponding to the incident radiation image is obtained. The scintillator layer has a characteristic of deteriorating by absorbing moisture. In the present invention, however, since the scintillator layer is covered with the moisture-resistant protective film, and an edge of the moisture-resistant protective film is coated with the coating resin, the scintillator layer is completely hermetically sealed so as to be isolated from the external atmosphere, thus being protected against vapor in the air. Further, the bonding pad portion for connection with an external circuit is exposed.
On the other hand, the method of making a radiation detection device in accordance with the present invention comprises: (1) forming a light-receiving portion by one- or two-dimensionally arranging a plurality of light-receiving devices and a plurality of bonding pads electrically connected to the light-receiving devices in respective rows or columns of the light-receiving portion are disposed outside the light-receiving portion on a substrate, and depositing a scintillator layer for converting a radiation into detectable light with the light-receiving devices thereon; (2) forming a radiation-transmittable, moisture-resistant protective film such as to envelope the light-receiving device array as a whole; (3) cutting and removing at least the part of the moisture-resistant protective film, outside the scintillator layer, covering the bonding pads so as to expose at least the part of the light-receiving device array in an area including the bonding pads; and (4) coating the moisture-resistant protective film with a resin along an edge portion acting as a boundary with respect to an exposed portion of the light-receiving device array so as to bring the edge of the moisture-resistant protective film into close contact with the light-receiving device array.
As the moisture-resistant protective film is formed such as to envelope the light-receiving device array as a whole, the adhesion between the scintillator layer and the moisture-resistant protective film improves, thereby forming a uniform film. As the uniform moisture-resistant protective film is removed from the bonding pad portion after being formed thereon, the bonding pad portion is securely exposed. Further, as the moisture-resistant protective film is coated with a resin along an edge portion acting as a boundary with respect to the exposed portion, the edge of the moisture-resistant protective film comes into close contact with the light-receiving device array surface thereunder, whereby the scintillator layer under the moisture-resistant protective film is sealed.
The moisture-resistant protective film may be a single layer organic film or a multilayer film made of at least two layers including an organic film laminated thereon.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope
Homme Takuya
Sato Hiroto
Takabayashi Toshio
Gabor Otilia
Hamamatsu Photonics K.K.
Hannaher Constantine
Pillsbury & Winthrop LLP
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