Radiation detector, radiographic imaging device, and radiation detector manufacturing method

1. A radiation detector comprising:

a flexible substrate;

a plurality of pixels provided on the substrate and each including a photoelectric conversion element;

a scintillator stacked on the substrate and including a plurality of columnar crystals; and

a bending suppression member configured to suppress bending of the substrate;

the bending suppression member having a rigidity that satisfies

R≥L−r /tan Φ+4 r ×{( L−r /tan Φ) 2 −( d/ 2) 2 } 1/2 /d

wherein L is an average height of the columnar crystals, r is an average radius of the columnar crystals, d is an average interval between the columnar crystals, Φ is an average tip angle of the columnar crystals, and R is a radius of curvature of bending occurring in the substrate due to the weight of the scintillator.

2. The radiation detector of claim 1 , wherein:

the scintillator is stacked on a first surface side of the substrate; and

the bending suppression member is stacked on at least one side of a second surface side of the substrate that is on the opposite side to the first surface side, or a side corresponding to a surface of the scintillator on the opposite side to a surface of the scintillator contacting the substrate.

3. The radiation detector of claim 2 , wherein the bending suppression member is stacked on both the second surface side of the substrate and the side corresponding to the surface of the scintillator on the opposite side to the surface of the scintillator contacting the substrate.

4. The radiation detector of claim 1 , wherein the bending suppression member has a higher rigidity than the substrate.

5. The radiation detector of claim 1 , wherein the bending suppression member extends so as to span a wider range than an extension range of the scintillator.

6. The radiation detector of claim 1 , wherein:

the substrate includes a connection region for a flexible wiring connection; and

the bending suppression member is provided in a region covering at least a portion of the connection region and also covering the scintillator.

7. The radiation detector of claim 1 , wherein the bending suppression member has a bending elastic modulus of from 1000 MPa to 3500 MPa.

8. The radiation detector of claim 1 , wherein a ratio of a coefficient of thermal expansion of the bending suppression member against a coefficient of thermal expansion of the scintillator is from 0.5 to 2.

9. The radiation detector of claim 1 , wherein a coefficient of thermal expansion of the bending suppression member is from 30 ppm/K to 80 ppm/K.

10. The radiation detector of claim 1 , wherein the bending suppression member is configured including at least one out of acrylic, polycarbonate, or polyethylene terephthalate.

11. The radiation detector of claim 1 , further comprising a reinforcement member that is provided in a region straddling an end portion of the scintillator so as to reinforce a bending suppression effect of the bending suppression member.

12. The radiation detector of claim 11 , wherein the reinforcement member has a higher rigidity than the substrate.

13. The radiation detector of claim 1 , wherein the substrate is configured including a resin film.

14. The radiation detector of claim 1 , wherein the substrate has a coefficient of thermal expansion not greater than 20 ppm/K in a temperature range from 300° C. to 400° C.

15. The radiation detector of claim 1 , further comprising a buffer layer that is provided between the substrate and the scintillator and that has a coefficient of thermal expansion lying between the coefficient of thermal expansion of the substrate and the coefficient of thermal expansion of the scintillator.

16. The radiation detector of claim 1 , wherein:

the scintillator includes a non-columnar portion on one end side of the columnar crystals; and

the non-columnar portion is in contact with the substrate.

17. A radiographic imaging device comprising:

the radiation detector of claim 1 ;

a reading circuit configured to perform reading of electrical charge accumulated in the pixels; and

a signal processor configured to generate image data based on the electrical charge read from the pixels.

18. The radiographic imaging device of claim 17 , further comprising:

a case that houses the radiation detector and that includes a radiation-incident face to which radiation is incident; and

out of the substrate and the scintillator, the substrate is disposed on a side corresponding to the radiation-incident face.

19. A manufacturing method for a radiation detector comprising:

forming a plurality of pixels on a flexible substrate such that each pixel includes a photoelectric conversion element;

forming a scintillator including a plurality of columnar crystals on the substrate; and

arranging a bending suppression member configured to suppress bending of the substrate;

rigidity of the bending suppression member being adjusted according to a height of the columnar crystals, a radius of the columnar crystals, a tip angle of the columnar crystals, and an interval between the columnar crystals.

20. The manufacturing method of claim 19 , wherein the bending suppression member has a rigidity satisfying

R≥L−r /tan Φ+4 r ×{( L−r /tan Φ) 2 −( d/ 2) 2 } 1/2 /d

wherein L is an average height of the columnar crystals, r is an average radius of the columnar crystals, d is an average interval between the columnar crystals, Φ is an average tip angle of the columnar crystals, and R is a radius of curvature of bending of the substrate due to the weight of the scintillator.