Milliwave band radio wave absorption sheet and milliwave radio wave absorption method

Abstract

Provided is a light weight and remarkably flexible sheet-shaped radio wave absorber having excellent radio wave absorbing capacity in milliwave band frequencies. The invention is a milliwave band radio wave absorption sheet comprising a radio wave reflection layer (A), a radio wave absorption layer (B) disposed above the layer (A) so as to be parallel thereto, and a protective layer (C) disposed above the layer (B) so as to be parallel thereto. The layer (B) has, at a frequency of 79 GHz, a dielectric constant, wherein the real part is 10 to 20 and the absolute value of the imaginary part is 4 to 10. The layer (B) has a film thickness of 200 to 400 μm. The absolute value of the imaginary part/real part from the dielectric constant is within a range of 0.30 to 0.60. The layer (C) has, at a frequency of 79 GHz, a dielectric constant, wherein the real part is 1.5 to 8.0 and the absolute value of the imaginary part is less than 1.0, and has a film thickness of 50 to 200 μm. In the milliwave band radio wave absorption sheet, the optical reflectance at an incident angle of 60° is 50% or greater, and the optical reflectance at an incident angle of 20° is 25% or greater. In addition, the invention provides a milliwave band radio wave absorption method using the radio wave absorption sheet, and a radio wave damage prevention method involving the installation of the radio wave absorption sheet.