Item comprising an organic-inorganic layer with a low refractive index

Abstract

The invention relates to an article comprising a substrate having at least one main surface coated with a layer L of a material M obtained by vacuum deposition, by co-evaporation, of at least one metallic compound A chosen from alkaline-earth metal fluorides and of at least one organic compound B, the material M having a refractive index at the wavelength of 632.8 nm ranging from 1.38 to 1.47. According to the invention: the organic compound B comprises an organosilicon compound or a mixture of organosilicon compounds; and the deposition of the compound B, in gaseous form, is carried out in the presence of an ion bombardment.

1 . An article comprising a substrate having at least one main surface coated with at least one layer L of at least one material M obtained by vacuum deposition, by co-evaporation, of at least one metallic compound A chosen from alkaline-earth metal fluorides and of at least one organic compound B, the material M having a refractive index at the wavelength of 632.8 nm ranging from 1.38 to 1.47, wherein:
 the organic compound B comprises an organosilicon compound or a mixture of organosilicon compounds; and   the deposition of the compound B, in gaseous form, is carried out in the presence of an ion bombardment.   
     
     
         2 . The article as claimed in  claim 1 , wherein that the organic compound B does not comprise any fluorocarbon. 
     
     
         3 . The article as claimed in  claim 1 , wherein the ion bombardment is carried out using an ion gun. 
     
     
         4 . The article as claimed in  claim 1 , wherein the deposition of the organosilicon compound B under ion bombardment is carried out in the presence of a gas chosen from oxygen, noble gases, nitrogen and a mixture of two or more of these gases. 
     
     
         5 . The article as claimed in  claim 1 , wherein the evaporation of the metallic compound A is carried out using an electron gun. 
     
     
         6 . The article as claimed in  claim 1 , wherein the metallic compound A is MgF 2 . 
     
     
         7 . The article as claimed in  claim 1 , wherein the organosilicon compound B comprises at least one Si—C bond. 
     
     
         8 . The article as claimed in  claim 1 , wherein the organosilicon compound B comprises at least one divalent group of formula: 
       
         
           
           
               
               
           
         
         where R′ 1  to R′ 4  independently denote alkyl, vinyl, aryl or hydroxyl groups or hydrolysable groups, or in that the compound B corresponds to the formula: 
       
       
         
           
           
               
               
           
         
         in which R′ 5 , R′ 6 , R′ 7  and R′ 8  independently denote hydroxyl groups or hydrolysable groups, such as OR groups, in which R is an alkyl group. 
       
     
     
         9 . The article as claimed in  claim 1 , wherein the compound B is chosen from octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, dodecamethylpentasiloxane or hexamethyldisiloxane. 
     
     
         10 . The article as claimed in  claim 1 , wherein the silicon atom or atoms of the organosilicon compound B do not comprise any hydrolysable group or hydroxyl group. 
     
     
         11 . The article as claimed in  claim 1 , wherein the layer L constitutes at least one layer of a multilayer interference coating. 
     
     
         12 . The article as claimed in  claim 11 , wherein the layer L constitutes the layer of the interference coating furthest from the substrate and wherein a thin organic-inorganic layer is deposited on said layer L, said organic-inorganic layer with a thickness of 1 to 20 nm having been obtained by deposition of an organosilicon compound or a mixture of organosilicon compounds in gaseous form, in the presence of an ion bombardment and in the absence of a mineral precursor. 
     
     
         13 . The article as claimed in  claim 11 , wherein the interference coating is an antireflective coating. 
     
     
         14 . The article as claimed in  claim 1 , further defined as an optical lens. 
     
     
         15 . The article as claimed in  claim 1 , wherein it possesses a critical temperature greater than or equal to 70° C. 
     
     
         16 . A process for the manufacture of an article as claimed in  claim 1 , comprising at least the following steps:
 supplying an article comprising a substrate having at least one main surface,   depositing, on said main surface of the substrate, a layer L of a material M having a refractive index ranging from 1.38 to 1.47 at the wavelength of 632.8 nm, and   recovering an article comprising a substrate having a main surface coated with a layer L,   
       said layer L having been obtained by deposition, by co-evaporation, of at least one metallic compound A chosen from alkaline-earth metal fluorides and of at least one organosilicon compound B, the deposition of the organosilicon compound B, in gaseous form, being carried out in the presence of an ion bombardment. 
     
     
         17 . The article as claimed in  claim 14 , wherein the optical lens is an ophthalmic lens.