Modification of uv absorption profile of polymer film reflectors to increase solar-weighted reflectance

Abstract

Provided are reflective thin film constructions including a reduced number of layers, which provides for increased solar-weighted hemispherical reflectance and durability. Reflective films include those comprising an ultraviolet absorbing abrasion resistant coating over a metal layer. Also provided are ultraviolet absorbing abrasion resistant coatings and methods for optimizing the ultraviolet absorption of an abrasion resistant coating. Reflective films disclosed herein are useful for solar reflecting, solar collecting, and solar concentrating applications, such as for the generation of electrical power.

1 . A multilayer reflective film comprising:
 a metal layer;   a polymeric layer; and   an abrasion resistant layer above the polymeric layer;   wherein the abrasion resistant layer has a cut-off wavelength less than 385 nm, the cut-off wavelength being an ultraviolet wavelength of the terrestrial solar spectrum at which a transmittance value of the abrasion resistant layer is equal to fifty percent of a maximum transmittance value of the abrasion resistant layer in the visible region of the terrestrial solar spectrum.   
     
     
         2 - 59 . (canceled) 
     
     
         60 . The multilayer reflective film of  claim 1 , further comprising an adhesive layer, wherein:
 the metal layer is above an adhesive layer; and   the polymeric layer is above the metal layer.   
     
     
         61 . The multilayer reflective film of  claim 1 , wherein:
 the metal layer is above the polymeric layer; and   the abrasion resistant layer is above the metal layer.   
     
     
         62 . The multilayer reflective film of  claim 61 , further comprising an adhesive layer beneath the polymeric layer. 
     
     
         63 . The multilayer reflective film of  claim 1 , further comprising a backside metal protective layer below the metal layer. 
     
     
         64 . The multilayer reflective film of  claim 1 , further comprising an adhesion-promoting layer below the abrasion resistant layer. 
     
     
         65 . The multilayer reflective film of  claim 1 , wherein the abrasion resistant layer has a cut-off wavelength selected from the range of 345 nm to 385 nm. 
     
     
         66 . The multilayer reflective film of  claim 1 , wherein the abrasion resistant layer has a thickness selected from the range of 2 μm to 10 μm. 
     
     
         67 . The multilayer reflective film of  claim 1 , wherein the abrasion resistant layer comprises one or more ultraviolet absorbing compounds having a cut-off wavelength less than 385 nm, wherein the ultraviolet absorbing compound is selected from the group consisting of oxanilide, benzophenone, HP triazine, benzotriazole, formamidine and any derivatives of these. 
     
     
         68 . The multilayer reflective film of  claim 1 , wherein the metal layer comprises a silver layer or a multilayer including a copper backside protective layer and a silver layer. 
     
     
         69 . A method of making a multilayer reflective film, the method comprising the steps of:
 providing a polymer film;   providing a metal layer; and   providing an abrasion resistant layer above the polymer film;   wherein abrasion resistant layer has a cut-off wavelength less than 385 nm, the cut-off wavelength being an ultraviolet wavelength of the terrestrial solar spectrum at which a transmittance value of the abrasion resistant layer is equal to fifty percent of a maximum transmittance value of the abrasion resistant layer in the visible region of the terrestrial solar spectrum.   
     
     
         70 . The method of  claim 69 , wherein
 the metal layer is provided onto a first side of the polymer film;   an adhesive layer is provided onto the metal layer; and   the abrasion resistant layer is provided onto a second side of the polymer film.   
     
     
         71 . The method of  claim 69 , wherein
 the metal layer is provided onto a first side of the polymer film; and   the abrasion resistant layer is provided onto the metal layer.   
     
     
         72 . The method of  claim 71 , further comprising the step of providing an adhesive layer onto a second side of the polymer film. 
     
     
         73 . The method of  claim 69 , wherein the reflective film is constructed using a roll-to-roll processing method. 
     
     
         74 . A multilayer reflective film comprising:
 an adhesive layer;   a metal layer above the adhesive layer;   a polymeric layer; and   an abrasion resistant layer above the polymeric layer;   wherein:
 the abrasion resistant layer has a cut-off wavelength less than 400 nm, and 
 the abrasion resistant layer has a transmittance of greater than or equal to 50% for electromagnetic radiation having wavelength ranging from the cut-off wavelength to 2.5 μm. 
   
     
     
         75 . The multilayer reflective film of  claim 74 , wherein the abrasion resistant layer has a cut-off wavelength less than 385 nm. 
     
     
         76 . The multilayer reflective film of  claim 75 , wherein:
 the metal layer is above an adhesive layer; and   the polymeric layer is above the metal layer.   
     
     
         77 . The multilayer reflective film of  claim 75 , wherein:
 the metal layer is above the polymeric layer; and   the abrasion resistant layer is above the metal layer.