Radiation detector and method for manufacturing the same

1. A radiation detector comprising:

a plurality of photoelectric conversion elements;

a scintillation layer which converts radioactive rays to fluorescence, the scintillation layer being formed on the photoelectric conversion elements; and

a reflective film formed on the scintillation layer, the reflective film containing light-scattering particles for reflecting the fluorescence from the scintillation layer and a binder material binding the light-scattering particles, and having depletion portions without being filled with the binder material, the depletion portions being formed in a periphery of the light-scattering particles,

wherein the reflective film satisfies a relationship of a volume filling ratio of the light-scattering particles to the binder material (a volume of the light-scattering particles/a volume of the binder material)≧4/6.

2. The radiation detector according to claim 1 , wherein

the scintillation layer has a pillar structure, and

some of the light-scattering particles in the reflective film are positioned on the scintillation layer, and penetrate into the pillar structure of the scintillation layer.

3. The radiation detector according to claim 1 , wherein

a main component of the binder material is butyral resin.

4. The radiation detector according to claim 1 , wherein

a volume occupying rate of the light-scattering particles in the reflective film is larger on a side close to the scintillation layer than on a side close to a surface layer of the reflective film.

5. The radiation detector according to claim 1 , wherein

the reflective film satisfies a relationship of an average size of the light-scattering particles/a volume filling factor of the light-scattering particles≦1/10×a film thickness.

6. The radiation detector according to claim 1 , wherein

the scintillation layer has a pillar structure, and

an average size of the light-scattering particles of the reflective film is one fourth or less of an inter-column average pitch of the pillar structure of the scintillation layer.

7. The radiation detector according to claim 1 , wherein

an average size of the light-scattering particles of the reflective film is within a range of one tenth to ten times of a maximum light-emitting wavelength of the scintillation layer.

8. The radiation detector according to claim 1 , wherein

the photoelectric conversion elements are arranged at a certain pitch, and

the reflective film has a thickness less than or equal to the pitch of the photoelectric conversion elements.

9. The radiation detector according to claim 1 , wherein

the reflective film contains an optical absorptive filler material for absorbing at least part of a fluorescent spectral component emitted by the scintillation layer.

10. The radiation detector according to claim 1 , wherein

the reflective film covers a surface of the scintillation layer with a certain thickness when covering a top surface and a thinner (or zero) thickness when covering a side or near-edge surface of the scintillation layer.

11. A method of manufacturing a radiation detector comprising:

forming a plurality of photoelectric conversion elements on a substrate;

forming a scintillation layer on the photoelectric conversion elements; and

applying a coating paste to the scintillation layer and thereafter drying the coating paste, the coating paste being obtained by stirring and mixing light-scattering particles, a binder material binding the light-scattering particles, and a solvent having a boiling point of 100° C. or more for dissolving the binder material, to form a reflective film having a depletion portion without being filled with the binder material, the depletion portion being formed in a periphery of the light-scattering particles.