Infrared radiation element

1. An infrared radiation element comprising:

a first insulating layer having heat insulating properties and electrically insulating properties;

a heating element layer provided on the first insulating layer and configured to radiate infrared radiation when energized; and

a second insulating layer provided on an opposite side of the heating element layer from the first insulating layer and having heat insulating properties and electrically insulating properties,

the second insulating layer transmitting the infrared radiation radiated from the heating element layer, and

the heating element layer having such a sheet resistance that impedance of the heating element layer matches impedance of space which is in contact with the second insulating layer.

2. The infrared radiation element as set forth in claim 1 , wherein

the sheet resistance of the heating element layer is selected so that an infrared emissivity of the heating element layer is not less than a predetermined value.

3. The infrared radiation element as set forth in claim 2 , wherein

the sheet resistance of the heating element layer falls within a range of 73Ω/□ to 493Ω/□.

4. The infrared radiation element as set forth in claim 1 , further comprising a substrate,

the first insulating layer being provided on a surface of the substrate.

5. The infrared radiation element as set forth in claim 4 , wherein

the substrate has an opening to expose the first insulating layer.

6. The infrared radiation element as set forth in claim 5 , wherein

the heating element layer is positioned in a region in which the first insulating layer is in contact with the opening in a plan view.

7. The infrared radiation element as set forth in claim 5 , further comprising

a pair of electrodes provided respectively on both ends of an opposite surface of the heating element layer from the first insulating layer.

8. The infrared radiation element as set forth in claim 7 , further comprising:

a pair of pads positioned in a region in which the opening is not provided in a plan view; and

a pair of electrical connectors electrically connecting the pair of pads to the pair of electrodes, individually,

the pair of pads being arranged to extend parallel to a predetermined direction, and

the pair of electrical connectors being arranged symmetrical about a center line passing through a center of gravity of the heating element layer and extending in the predetermined direction.

9. The infrared radiation element as set forth in claim 8 , wherein

each of the pair of electrical connectors is composed of two or more wires.

10. The infrared radiation element as set forth in claim 8 , wherein

the pair of electrical connectors are made of tantalum.

11. The infrared radiation element as set forth in claim 1 , wherein

the heating element layer is made of tantalum nitride or electrically conductive polysilicon.