Optical element with high scratch resistance

Abstract

An optical element is provided that includes a substrate that is transparent in the visible spectral region and a multilayer anti-reflection coating on the substrate. The coating has alternating layers of layers having a first refractive index and of layers having a second, higher refractive index. The layers having the higher refractive index contain nitride or oxynitride and the layers having the first refractive index contain oxide of silicon and of at least one other element. The molar fraction of silicon in the layers having the first refractive index is predominant when compared to the molar fraction(s) of the other element or elements. The uppermost layer of the coating is a layer having the first refractive index. A layer of chain-form organofluoro molecules is disposed on the coating, wherein the molecules are bonded at the ends to the surface of the optical element.

What is claimed is: 
     
         1 . An optical element with high scratch resistance, comprising:
 a substrate that is transparent in the visible spectral region;   a multilayer anti-reflection coating on the substrate, the multilayer anti-reflection coating having alternating layers of a first layer type having a first refractive index and layers of a second layer type having a second, higher refractive index, the layers of the second layer type comprising nitride or oxynitride, the layers of the first layer type comprising oxide of silicon and at least one other element, the first layer type having a molar fraction of silicon that is predominant when compared to a molar fraction of the at least one other element, wherein the multilayer anti-reflection coating has an uppermost layer that comprises the first layer type; and   a layer of chain-form organofluoro molecules on the multilayer anti-reflection coating, the layer having molecules that are bonded at their ends to the uppermost layer of the multilayer anti-reflection coating.   
     
     
         2 . The optical element according to  claim 1 , wherein the layer of chain-form organofluoro molecules is a monomolecular layer. 
     
     
         3 . The optical element according to  claim 1 , wherein the layer of chain-form organofluoro molecules comprise molecules with perfluorinated carbon chains. 
     
     
         4 . The optical element according to  claim 1 , wherein the at least one other element of the first layer type is an element selected from the group consisting of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, barium, strontium, niobium, and boron. 
     
     
         5 . The optical element according to  claim 1 , wherein the substrate comprises a sapphire substrate. 
     
     
         6 . The optical element according to  claim 1 , wherein the substrate comprises a chemically prestressed glass substrate. 
     
     
         7 . The optical element according to  claim 1 , wherein the multilayer anti-reflection coating comprises a stack of four successive layers having a lowermost layer that comprises a layer of the second layer type, the uppermost layer having a second-greatest layer thickness among the stack, and wherein the multilayer anti-reflection coating has a lowermost layer that comprises the second layer type, the lowermost layer having a layer thickness that is thinner than the layer thickness of the uppermost layer. 
     
     
         8 . The optical element according to  claim 7 , wherein the at least one other element of the layers of the first layer type comprises aluminum. 
     
     
         9 . The optical element according to  claim 1 , wherein the uppermost layer has a greatest layer thickness of the multilayer anti-reflection coating and has a layer thickness in the range of 100 nm to 700 nm. 
     
     
         10 . The optical element according to  claim 9 , wherein the layer thickness is in the range of 400 nm to 500 nm. 
     
     
         11 . The optical element according to  claim 1 , wherein the first layer type has a ratio of silicon to the at least one other element of at least 5:1. 
     
     
         12 . The optical element according to  claim 1 , wherein the first layer type has a ratio of silicon to the at least one other element of at least 8:1. 
     
     
         13 . The optical element according to  claim 1 , further comprising a Knoop hardness of at least 600 kilograms per square millimeter. 
     
     
         14 . The optical element according to  claim 1 , wherein the substrate has a modulus of elasticity of at least 50 GPa. 
     
     
         15 . The optical element according to  claim 1 , wherein the multilayer anti-reflection coating comprises a stack of four successive layers comprising two of the layers of the first layer type and two of the layers of the second layer type, an upper of the two layers of the second layer having a layer thickness that amounts to at least 40% of a thickness of the multilayer anti-reflection coating. 
     
     
         16 . The optical element according to  claim 15 , wherein the upper of the two layers of the second layer has a layer thickness that amounts to at least 70% of the thickness. 
     
     
         17 . A method for producing an optical element, comprising:
 preparing a substrate that is transparent in the visible spectral region;   vacuum depositing a multilayer anti-reflection coating onto the substrate by alternating layers of a first layer type having a first refractive index and layers of a second layer type having a second, higher refractive index, wherein the layers of the second layer type comprise nitride or oxynitride and the layers of the first layer type comprise oxide of silicon and at least one other element, wherein the layers of the first type have a molar fraction of silicon that is predominant when compared to molar fraction(s) of the at least one other element, and wherein the multilayer anti-reflection coating has an uppermost layer that comprises the layer of the first layer type; and   applying a coating with a layer of chain-form organofluoro molecules on the multilayer anti-reflection coating so that molecules of the layer are bonded at their ends to the uppermost layer.   
     
     
         18 . The method according to  claim 17 , wherein the step of vacuum depositing comprises reactive magnetron sputtering. 
     
     
         19 . The method according to  claim 17 , wherein the step of applying the coating comprises liquid coating. 
     
     
         20 . The method according to  claim 17 , wherein the step of applying the coating comprises vaporizing in a vacuum deposition method.