Electromagnetic wave reflecting member

Abstract

Disclosed is a selectively reflective member which can uniformly reflect only a desired wavelength with high efficiency even in a large area and, at the same time, is highly cost effective. Specifically, there is provided an electromagnetic wave reflecting member that reflects electromagnetic waves with a specific wavelength, the electromagnetic wave reflecting member comprising a first selectively reflective layer that reflects only a clockwise or counterclockwise circularly polarized light component with wavelength λ in incident electromagnetic waves, a phase difference layer, and a second selectively reflective layer that reflects only a clockwise or counterclockwise circularly polarized light component with wavelength λ, provided in that order, the phase difference layer having a retardation satisfying the following equation: Re ={(2 n +1)/2±0.2}×λ wherein Re represents average retardation; λ represents wavelength; and n is an integer of 1 or more.

1 . An electromagnetic wave reflecting member that reflects electromagnetic waves with a specific wavelength,
 the electromagnetic wave reflecting member comprising a first selectively reflective layer that reflects only a clockwise or counterclockwise circularly polarized light component with wavelength λ in incident electromagnetic waves, a phase difference layer, and a second selectively reflective layer that reflects only a clockwise or counterclockwise circularly polarized light component with wavelength λ, provided in that order,   the phase difference layer having an average retardation satisfying the following equation:
     Re ={(2 n+ 1)/2±0.2}×λ 
   
       wherein Re represents retardation; λ represents wavelength; and n is an integer of 1 or more. 
     
     
         2 . The electromagnetic wave reflecting member according to  claim 1 , wherein the reflection wavelength λ is in the range of 400 nm to 20 μm. 
     
     
         3 . The electromagnetic wave reflecting member according to  claim 1 , wherein the phase difference layer is formed of a stretched polymer film. 
     
     
         4 . The electromagnetic wave reflecting member according to  claim 3 , wherein the in-plane distribution of the retardation of the polymer film is ±25 nm or more. 
     
     
         5 . The electromagnetic wave reflecting member according to  claim 3 , wherein the in-plane distribution of the retardation of the polymer film is ±10% or less of the average retardation. 
     
     
         6 . The electromagnetic wave reflecting member according to  claim 3 , wherein the polymer film is a polyethylene terephthalate film. 
     
     
         7 . The electromagnetic wave reflecting member according to  claim 1 , wherein the selectively reflective layer comprises a rod-like compound having a cholesteric structure. 
     
     
         8 . The electromagnetic wave reflecting member according to  claim 7 , wherein the selectively reflective layer comprises an immobilized chiral nematic liquid crystal. 
     
     
         9 . The electromagnetic wave reflecting member according to  claim 1 , wherein the reflection wavelength λ is not less than 750 nm. 
     
     
         10 . A heat reflecting glass comprising an electromagnetic wave reflecting member according to  claim 1 .