Electromagnetic wave absorber and electromagnetic wave absorber-attached molded article
An electromagnetic wave absorber ( 1 ) includes a dielectric layer ( 10 ), a resistive layer ( 20 ), and an electrically conductive layer ( 30 ). The resistive layer ( 20 ) is disposed on one principal surface of the dielectric layer ( 10 ). The electrically conductive layer ( 30 ) is disposed on the other principal surface of the dielectric layer ( 10 ) and has a sheet resistance lower than a sheet resistance of the resistive layer ( 20 ). The resistive layer ( 20 ) is a layer that includes tin oxide or titanium oxide as a main component or a layer that is made of indium tin oxide including 40 weight % or more of tin oxide.
1. An electromagnetic wave absorber, comprising:
a dielectric layer;
a resistive layer that is disposed on one principal surface of the dielectric layer; and
an electrically conductive layer that is disposed on the other principal surface of the dielectric layer and has a sheet resistance lower than a sheet resistance of the resistive layer, wherein
the resistive layer is a layer that comprises tin oxide or titanium oxide as a main component or a layer that is made of indium tin oxide comprising 40 weight % or more of tin oxide, and
the resistive layer has a polycrystalline structure when the resistive layer comprises tin oxide or titanium oxide as a main component.
2. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer has a specific resistance of 5×10 −4 Ω·cm or more.
3. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer further comprises a dopant that is at least one element other than tin and titanium.
4. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer is made of antimony-doped tin oxide, fluorine-doped tin oxide, or niobium-doped titanium oxide.
5. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer has a sheet resistance of 200 to 600 Ω/□.
6. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer has a thickness of 5 to 500 nm.
7. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer is laminated on a polymer film at an opposite surface to a surface at which the resistive layer is in contact with the dielectric layer.
8. The electromagnetic wave absorber according to claim 1 , wherein the dielectric layer has a relative permittivity of 1 to 10.
9. The electromagnetic wave absorber according to claim 1 , wherein the dielectric layer is made of a polymeric material.
10. The electromagnetic wave absorber according to claim 1 , wherein the electrically conductive layer has a sheet resistance of 0.001 to 30 Ω/□.
11. The electromagnetic wave absorber according to claim 1 , wherein the electrically conductive layer comprises at least one of aluminum, an aluminum alloy, aluminum nitride, copper, a copper alloy, copper nitride, and indium tin oxide.
12. An electromagnetic wave absorber-attached molded article, comprising:
a molded article; and
the electromagnetic wave absorber according to claim 1 attached to the molded article.
13. The electromagnetic wave absorber according to claim 1 , wherein the electromagnetic wave absorber has a return loss of 20 dB or more for an electromagnetic wave to be absorbed when the resistive layer is immersed in a 5 weight % aqueous solution of NaOH for 5 minutes, and
the electromagnetic wave absorber has a return loss of 20 dB or more for the electromagnetic wave to be absorbed when the resistive layer refrains from being immersed in a 5 weight % aqueous solution of NaOH for 5 minutes.