Transparent substrate comprising a stack of thin layers for electromagnetic armour

Abstract

A transparent substrate, especially made of glass, provided with a thin-film multilayer ( 20 ) that includes three silver layers (Ag1, Ag2, Ag3) and comprises, alternately on the substrate, a titanium dioxide layer ( 21 ), a metal oxide layer ( 22 ), one of the silver layers (Ag1, Ag2, Ag3) and a covering layer ( 23 ), characterized in that: the metal oxide is zinc oxide; the covering layer ( 23 ) is a sacrificial metal; and an antireflection layer ( 24 ) comprising at least one metal oxide is deposited on the covering layer ( 23 ) for the silver layer (Ag 3 ) furthest away from the substrate.

1 . A transparent substrate, especially made of glass, provided with a thin-film multilayer ( 20 ) that includes three silver layers (Ag 1 , Ag 2 , Ag 3 ) and comprises, alternately on the substrate, a titanium dioxide layer ( 21 ), a metal oxide layer ( 22 ), one of the silver layers (Ag 1 , Ag 2 , Ag 3 ) and a covering layer ( 23 ), characterized in that:
 the metal oxide is zinc oxide;   the covering layer ( 23 ) is a sacrificial metal; and   an antireflection layer ( 24 ) comprising at least one metal oxide is deposited on the covering layer ( 23 ) for the silver layer (Ag 3 ) furthest away from the substrate.   
     
     
         2 . The substrate as claimed in  claim 1 , characterized in that the thickness of each of the silver layers (Ag 1 , Ag 2 , Ag 3 ) is between 13 nm and 19 nm. 
     
     
         3 . The substrate as claimed in  claim 2 , characterized in that the thicknesses (e Ag1 , e Ag2 , e Ag3 ) of the respective layers (Ag 1 , Ag 2 , Ag 3 ) are identical, or else they vary in a ratio of between 0.8 and 1.2 and are such that e Ag1 ≦e Ag3 ≦e Ag2 . 
     
     
         4 . The substrate as claimed in one of  claims 1  to  3 , characterized in that the titanium dioxide layer ( 21 ) as sublayer for the silver layer (Ag 1 ) closest to the substrate has a thickness of between 10 and 20 nm, preferably between 10 and 15 nm, and the titanium oxide layers ( 21 ) as sublayers for the other two silver layers (Ag 2 , Ag 3 ) have a thickness of between 35 and 55 nm, preferably between 40 and 50 nm. 
     
     
         5 . The substrate as claimed in any one of the preceding claims, characterized in that the zinc oxide layer ( 22 ) has a thickness of greater than 15 nm. 
     
     
         6 . The substrate as claimed in any one of the preceding claims, characterized in that the sacrificial metal layer ( 23 ) is of niobium (Nb), titanium (Ti) or zirconium (Zr). 
     
     
         7 . The substrate as claimed in any one of the preceding claims, characterized in that the sacrificial metal layer ( 23 ) has a thickness not exceeding 2 nm. 
     
     
         8 . The substrate as claimed in any one of the preceding claims, characterized in that the antireflection layer ( 24 ) has a thickness of between 25 and 50 nm, preferably between 25 and 35 nm. 
     
     
         9 . The substrate as claimed in  claim 8 , characterized in that the antireflection layer ( 24 ) includes at least one titanium dioxide layer having a thickness of between 15 and 35 nm, preferably between 20 and 30 nm. 
     
     
         10 . The substrate as claimed in either of  claims 8  or  9 , characterized in that the antireflection layer ( 24 ) includes a titanium dioxide layer and another layer of a metal oxide that is deposited on said titanium dioxide layer and has a thickness of between 5 and 15 nm, preferably between 6 and 10 nm. 
     
     
         11 . The substrate as claimed in  claim 10 , characterized in that the metal oxide layer of the antireflection layer ( 24 ) is tin oxide (SnO 2 ) or silica nitride (Si 3 N 4 ). 
     
     
         12 . The substrate as claimed in any one of the preceding claims, characterized in that it has a surface resistance not exceeding 1Ω/□, preferably between 0.7 and 0.9 Ω/□. 
     
     
         13 . The substrate as claimed in any one of the preceding claims, characterized in that it is made of toughened or untoughened glass, or made of plastic. 
     
     
         14 . An electromagnetic shielding filter comprising a substrate as claimed in any one of the preceding claims, characterized in that it has the following optical properties:
 a light transmission factor T L  of between 45 and 55%;   a purity of less than 10% in transmission;   a light reflection R L  of less than 5%, preferably less than 4%;   a predominantly violet-blue color in reflection with a purity of less than 20%;   a predominantly blue color in transmission.   
     
     
         15 . A display screen of the plasma display type incorporating, on its front face, at least one substrate or filter as claimed in any one of  claims 1  to  14 .