Glass, ceramic and metal substrates with a self-cleaning surface, method of making them and their use

Abstract

The invention relates to glass, ceramic and metal substrates with at least one self-cleaning surface, comprising a layer with a micro-rough surface structure that is arranged on the substrate and made at least partly hydrophobic. The layer contains a glass flux and structure-forming particles with a mean particle diameter within the 0.1 to 50 μm range; the glass flux and structure-forming particles are present in a volume ratio within the 0.1 to 5 range, and the micro-rough surface structure has a ratio of mean profile height to mean distance between adjacent profile tips within the 0.3 to 10 range. To produce the subject of the invention the substrate is coated with a composition containing a glass flux and structure-forming particles, and the layer is burnt in and made hydrophobic.

1 . A method of making a substrate with a self-cleaning surface having a hydrophobic, micro-rough layer comprising the steps of: 
 (a) coating the substrate with a composition containing a glass frit which forms a glass flux and structure-forming particles with a mean particle diameter within the range of from 0.1 to 50 μm, the composition containing glass frit and structure-forming particles in a volume ratio within the range of 0.1 to 5;    (b) burning in the substrate at a temperature above the deformation temperature of the glass frit thereby forming a burnt-in layer; and    (c) making the burnt-in layer at least partially hydrophobic by applying an agent to make it hydrophobic.    
     
     
         2 . The method according to  claim 1  wherein the composition containing the glass frit which forms a glass flux and structure-forming particles is applied to the substrate in the form of a printable paste by a direct or indirect printing process.  
     
     
         3 . The method according to  claim 1 , wherein the composition containing the glass frit which forms a glass flux and structure-forming particles is applied to the substrate electrostatically in the form of a mixture of powders.  
     
     
         4 . The method according to  claim 1 , wherein the burnt-in layer has a micro-rough surface structure having a ratio of mean profile height to mean distance between adjacent profile tips within the 0.3 to 10 range.  
     
     
         5 . The method according to  claim 4 , wherein the substrate is selected from the group consisting of glass, porcelain, vitrified clay, stoneware, clinker and brick substrates.  
     
     
         6 . The method according to  claim 4 , wherein the volume ratio of glass flux to structure-forming particles is within the range of from 0.2 to 2.  
     
     
         7 . The method according to  claim 4 , wherein the micro-rough surface structure has an aspect ratio within the range of from 1 to 5.  
     
     
         8 . The method according to  claim 4 , wherein the structure-forming particles have a mean diameter within the range of from 0.5 to 15 μm.  
     
     
         9 . The method according to  claim 4 , wherein the structure-forming particles are idiomorphic.  
     
     
         10 . The method according to  claim 4 , wherein the layer that makes the burnt-in layer hydrophobic is based on a fluoroalkyl alkoxysilane or a fluoroalkyl alkoxysiloxane.  
     
     
         11 . A method of making a substrate with at least one self-cleaning surface that is at least partially hydrophobic, comprising the steps of: 
 (a) coating the substrate with a composition containing a glass frit which forms a glass flux and structure-forming particles having a bimodal size distribution, wherein a first portion of the structure-forming particles has a mean particle diameter within the range of from 0.2 to 3 μm and a second portion of the structure-forming particles has a mean particle diameter within the range of from 3 to 15 μm, and the glass frit and structure-forming particles are present in a volume ratio within the range of 0.1 to 5;    (b) burning in the substrate at a temperature above the deformation temperature of the glass frit thereby forming a burnt-in layer having a micro-rough surface structure having a ratio of mean profile height to mean distance between adjacent profile tips within the 0.3 to 10 range; and    (c) making the burnt-in layer at least partially hydrophobic by applying an agent to make it hydrophobic.    
     
     
         12 . The method according to  claim 11 , wherein the second portion of the structure-forming particles has a mean diameter of 5 to 10 μm.  
     
     
         13 . The method according to  claim 11 , wherein the glass flux and structure-forming particles are present in a volume ratio within the 0.2 to 2 range.  
     
     
         14 . The method according to  claim 11 , wherein the micro-rough surface structure has a ratio of mean profile height to mean distance between adjacent profile tips within the 1 to 5 range.  
     
     
         15 . The method according to  claim 11 , wherein the burnt-in layer is made at least partially hydrophobic by application of a substance selected from the group consisting of fluroalkyl alkoxysilane, fluoroalkyl alkoxysiloxane, and partly fluorinated vinyl polymer.  
     
     
         16 . The method according to  claim 11 , wherein the substrate is selected from the group consisting of metal, glass, porcelain, vitrified clay, stoneware, clinker and brick substrates.  
     
     
         17 . The method according to  claim 11 , wherein the volume ratio of glass flux to structure-forming particles is within the range of from 0.3 to 1.  
     
     
         18 . The method according to  claim 11 , wherein the micro-rough surface structure has an aspect ratio within the range of from 1 to 2.  
     
     
         19 . The method according to  claim 11 , wherein the structure-forming particles have a mean diameter within the range of from 1 to 2 μm.  
     
     
         20 . The method according to  claim 11 , wherein the structure-forming particles are idiomorphic.  
     
     
         21 . A method of making a glass, ceramic or metal substrate with at least one self-cleaning surface that is at least partially hydrophobic, comprising the steps of: 
 (a) coating the substrate with a composition containing a glass frit which forms a glass flux and structure-forming particles having a bimodal size distribution, wherein a first portion of the structure-forming particles has a mean particle diameter within the range of from 0.2 to 3 μm and a second portion of the structure-forming particles has a mean particle diameter within the range of from 5 to 10 μm, and the glass frit and structure-forming particles are present in a volume ratio within the range of 0.2 to 2;    (b) burning in the substrate at a temperature above the deformation temperature of the glass frit thereby forming a burnt-in layer having a micro-rough surface structure having a ratio of mean profile height to mean distance between adjacent profile tips within the 0.3 to 10 range; and    (c) making the burnt-in layer at least partially hydrophobic by applying an agent to make it hydrophobic.    
     
     
         22 . The method according to  claim 21 , wherein the structure-forming particles are selected from the group consisting of SiO 2 , TiO 2 , ZrO 2 , SnO 2 , Al 2 O 3 , zirconium silicates and zeolites.