1. Field of the Invention
The present invention relates to a radiation detector to be used in a clinical X-ray photography device or the like.
2. Description of the Related Art
The following radiation detectors are known: indirect conversion-type radiation detectors that first convert radiation such as X-rays or the like to light and then further convert the converted light to electronic signals by opto-electronic conversion; and direct conversion-type radiation detectors in which incident radiation is directly converted to electronic signals by a charge conversion layer.
As a direct conversion-type radiation detector, radiation detectors disclosed in Japanese Patent Application Laid-Open (JP-A) Nos. 2005-86059 and 2005-286183 are widely known. In a radiation detector of JP-A No. 2005-86059 or JP-A No. 2005-286183, a high voltage line is connected to an upper electrode portion on a charge conversion layer, which is amorphous selenium. Consequently, depending on conditions at a time of connection during manufacture and at subsequent times of usage and the like, the high voltage line compresses the amorphous selenium. Crystallization of the amorphous selenium is induced by this pressure and the amorphous selenium degrades, and radiation detection accuracy falls.
Alternatively, in a structure in which a connection between the high voltage line and the upper electrode portion is formed not on the charge conversion layer but at a region in which there is no charge conversion layer on a glass substrate, the glass substrate and the upper electrode portion are joined together. Therefore, high adhesion between the glass substrate and the upper electrode portion is required, and thus materials to be used for the upper electrode portion are limited.
In contrast, as illustrated in JP-A No. 2000-241556, a structure is known in which the upper electrode portion is formed on the charge conversion layer and is led along a side face of the charge conversion layer down to the glass substrate, and the high voltage line, which is introduced from a panel exterior portion, is connected with the upper electrode portion at a connection pad which is formed on the glass substrate using a conductive material, such as an ITO film.
However, with the structure illustrated in JP-A No. 2000-241556, it is necessary to form an ITO film or the like on the glass substrate beforehand. In such a case, a structure is formed in which a portion of the conductive connection pad is under the charge conversion layer. As a result, there is a possibility that creeping discharges to pixel electrodes, which are a lower electrode portion provided under the charge conversion layer, may occur.