Radiation detector and method for manufacturing the same

1. A radiation detector comprising:

an array substrate comprising a photoelectric conversion element;

a scintillator layer formed on the photoelectric conversion element and converting radiation to fluorescence; and

a composite layer comprising a surface-smoothing layer and a moisture-proof layer, the surface-smoothing layer being a continuous film formed to cover the scintillator layer and comprising an organic resin material and, dispersed therein, light scattering particles, the moisture-proof layer being a continuous film formed on a surface of the surface-smoothing layer by direct film formation and consisting of inorganic material,

wherein the surface-smoothing layer has:

a higher volume fraction of the light scattering particles on a side nearer to the scintillator layer and a lower volume fraction of the light scattering particles on a side nearer to the moisture-proof layer, and

a thickness that is not less than an unevenness of the scintillator layer.

2. The radiation detector according to claim 1 , wherein the composite layer comprises an alternating stack of plural surface-smoothing layers and plural moisture-proof layers.

3. The radiation detector according to claim 1 , further comprising: wirings from external circuits and connected to bonding pads of lead-wirings on the array substrate in a periphery of a region where the scintillator layer is formed, the moisture-proof layer being formed on at least a portion of the wirings as well.

4. The radiation detector according to claim 1 , wherein the light scattering particles have an average particle diameter of 1/10 to 10 times of a main fluorescence wavelength of the scintillator, and consist of one or more kinds of ceramics or metals.

5. The radiation detector according to claim 1 , wherein the surface-smoothing layer has no particles on the side nearer to the moisture-proof layer.

6. The radiation detector according to claim 1 , wherein the volume fraction of the light scattering particles satisfies the following equation on the side nearer to the scintillator layer:

volume of light scattering particles/volume of organic resin material≧1.0.

7. The radiation detector according to claim 1 , wherein the volume fraction of the light scattering particles satisfies the following equation on the side nearer to the moisture-proof layer:

volume of light scattering particles/volume of organic resin material<1.0.

8. The radiation detector according to claim 1 , wherein the light scattering particles are made from titanium oxide.

9. A method for manufacturing a radiation detector, comprising:

forming a scintillator layer on a surface of an array substrate comprising a photoelectric conversion element, the scintillator layer converting radiation to fluorescence;

forming a first surface-smoothing layer to cover the scintillator layer, the surface-smoothing layer being formed by coating of a first organic resin liquid comprising light scattering particles on the scintillator layer and drying the first organic resin liquid;

forming a second surface-smoothing layer to cover the first surface-smoothing layer, the second surface-smoothing layer being formed by coating of a second organic resin liquid comprising the light scattering particles on the first surface-smoothing layer and drying the second organic resin liquid, a volume fraction of the light scattering particles of the second organic resin liquid being lower than a volume fraction of the light scattering particles of the first organic resin liquid, a total thickness of the first and second surface-smoothing layers being not less than an unevenness of the scintillator layer; and

forming a moisture-proof layer which is a continuous film formed on a surface of the second surface-smoothing layer by direct film formation of inorganic material.

10. The method for manufacturing the radiation detector according to claim 9 , wherein in the forming the surface-smoothing layer, an outermost surface of the surface-smoothing layer is smoothed by applying a coating liquid on the scintillator layer and drying the liquid, the coating liquid including an organic resin and solvent having a boiling point of 100° C. or more.

11. The method for manufacturing the radiation detector according to claim 9 , wherein in the forming the moisture-proof layer, the moisture-proof layer is formed by a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method), and the moisture-proof layer includes at least one selected from the group of a metal film, a oxide film, a nitride film, an oxynitride film, and a composite film of the metal film, the oxide film, the nitride film and the oxynitride film.

12. The method for manufacturing the radiation detector according to claim 9 , wherein before forming the moisture-proof layer, the surface-smoothing layer is heated up to a preferred high temperature and held to promote outgassing from the surface-smoothing layer, then cooled down to a lower temperature, and thereafter the moisture-proof layer is formed on the surface-smoothing layer.

13. The method for manufacturing the radiation detector according to claim 9 , further comprising:

before forming the moisture-proof layer, connecting wirings from external circuits to bonding pads of lead-wirings provided on the array substrate in a periphery of a region where the scintillator layer is formed.

14. A method for manufacturing a radiation detector, comprising:

forming a scintillator layer on a surface of an array substrate comprising a photoelectric conversion element, the scintillator layer converting radiation to fluorescence;

forming a first surface-smoothing layer to cover the scintillator layer, the surface-smoothing layer being formed by coating of a first organic resin liquid comprising light scattering particles on the scintillator layer and drying the first organic resin liquid;

forming a second surface-smoothing layer to cover the first surface-smoothing layer, the second surface-smoothing layer being formed by coating of a second organic resin liquid comprising no light scattering particles on the first surface-smoothing layer and drying the second organic resin liquid, a total thickness of the first and second surface-smoothing layers being not less than an unevenness of the scintillator layer; and

forming a moisture-proof layer which is a continuous film formed on a surface of the second surface-smoothing layer by direct film formation of inorganic material.