UV-Curing Anti-Fingerprinting Coatings

Abstract

Process for the production on metal or plastic surfaces of thin, hydrolysis-resistant, scratch-resistant and stain-resistant coatings, wherein the coating material can be applied directly to the cleaned metal surface and subsequently cross-linked by high-energy radiation, in particular UV radiation. The substrates can be coated in the form of strip and only subsequently brought into the required external shape. Coated substrates such as these are no longer susceptible to staining by food, cleaning agents or fingerprints and can also be rendered antibacterial. Objects coated in this manner are thus suitable for use in architecture, for interior fittings of buildings, in furniture-making as well as for ornamental applications, and in particular in households, in sanitary applications, in hospitals and in the food-processing and pharmaceutical industries.

1 . A process for applying a fingerprint resistant coating on a metal surface, said process comprising: 
 applying to a metal surface a layer of coating material, comprising: 
 a. 40 to 90 wt. % of at least one oligomeric substance selected from the group consisting of epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and polyurethane (meth)acrylates, wherein said oligomeric substance is linear or branched and contains at least two unsaturated double bonds;  
 b. 5 to 60 wt. % of at least one low molecular weight (meth)acrylate selected from the group consisting of monofunctional, difunctional, trifunctional and polyfunctional (meth)acrylate compounds;  
 c. 0.1 to 20 wt. % of at least one (meth)acrylate compound containing one or more acidic groups; and  
 d. 0.1 to 20 wt. % of at least one auxiliary substance selected from the group consisting of adhesion promoters different from c, flow-control agents, defoaming agents, light stabilizers, dyes, pigments, biocides, fillers and photoinitiators;  
   wherein the coating material has a viscosity of less than 1000 mPas within a temperature range of 0 to 90° C.; and    crosslinking the layer of coating material by means of high-energy radiation such that a fingerprint resistant coating is formed.    
   
   
       2 . The process according to  claim 1  wherein cross-linking of said layer is by means of high-energy radiation selected from UV radiation, electron radiation or gamma-radiation.  
   
   
       3 . The process according to  claim 2  wherein the high-energy radiation used is UV radiation.  
   
   
       4 . The process according to  claim 2  wherein said layer of coating material is from 0.5 to 20 μm in thickness.  
   
   
       5 . The process according to  claim 2  wherein said layer of coating material is from 1 to 10 μm in thickness.  
   
   
       6 . The process according to  claim 2  wherein no pretreatment or primer is applied to the metal surface prior to said layer of coating material.  
   
   
       7 . The process according to  claim 2  wherein the high-energy radiation used has a wavelength of 200 to 450 nm.  
   
   
       8 . The process according to  claim 2  wherein the coating material after cross-linking is transparent.  
   
   
       9 . The process according to  claim 2  wherein said metal surface is in the form of a strip and is coated by roller application.  
   
   
       10 . The process according to  claim 2  wherein during the cross-linking step the metal surface having the layer applied thereon is in a low-oxygen or oxygen-free atmosphere.  
   
   
       11 . The process according to  claim 2  wherein after applying said layer of coating material and before cross-linking said layer a high-energy radiation permeable film is applied to said layer.  
   
   
       12 . The process according to  claim 11  wherein the film is comprised of at least one polymer selected from the group consisting of polyethylene, polypropylene, and PET and is separable from the layer after cross-linking.  
   
   
       13 . The process according to  claim 2  additionally comprising the step of forming the metal surface having the cross-linked layer thereon.  
   
   
       14 . The process according to  claim 2  wherein said metal surface is cleaned prior to applying said layer of coating material but does not have a primer or pretreatment layer applied to the metal surface.  
   
   
       15 . A process for applying a fingerprint resistant coating on a metal surface, said process comprising: 
 optionally cleaning and drying a metal surface;    applying to the metal surface a layer of coating material, comprising: 
 a. 45 to 85 wt. % of at least one oligomeric substance having at least two unsaturated double bonds selected from the group consisting of aromatic epoxy (meth)acrylates, and optionally, polyester (meth)acrylates, polyether (meth)acrylates, and polyurethane (meth)acrylates, wherein said oligomeric substance is linear or branched;  
 b. 10 to 60 wt. % of at least one (meth)acrylate selected from the group consisting of monofunctional, difunctional, trifunctional and polyfunctional (meth)acrylate compounds;  
 c. 0.5 to 10 wt. % of at least one (meth)acrylate compound containing one or more phosphoric or carboxyl acidic functional groups;  
 d. 0.5 to 15 wt. % of at least one radical photoinitiator; and  
 e. up to 20 wt. % of at least one silane selected from the group consisting of dialkoxysilanes and trialkoxysilanes wherein said at least one silane contains an amine functional group;  
   wherein components a. through e. are selected and homogenized together such that the coating material has a viscosity of less than 300 mPas within a temperature range of 0 to 90° C. in the absence of solvent; and    crosslinking the layer of coating material by means of high-energy radiation such that a fingerprint resistant coating is formed.    
   
   
       16 . An object comprising a metal substrate having a metal surface and a layer of a cross-linked coating material deposited on the metal surface by the process of  claim 1 , wherein said metal substrate is a sheet or strip.  
   
   
       17 . An object having a metal surface and a layer of a cross-linked coating material up to 5 μm in thickness deposited on the metal surface by the process of  claim 1 .  
   
   
       18 . The object according to  claim 17  wherein said metal surface is comprised of a material selected from the group consisting of ferrous materials, steel, alloyed steel, light metals, non-ferrous metals and precious metals.  
   
   
       19 . The object according to  claim 18  additionally comprising a film comprising at least one polymer selected from the group consisting of polyethylene, polypropylene, and PET on said layer of cross-linked coating material.  
   
   
       20 . A process for applying a fingerprint resistant coating on a metal surface, said process comprising: 
 optionally cleaning and drying a metal surface;    applying to the metal surface a layer of coating material, comprising: 
 a. 45 to 85 wt. % of at least one oligomeric substance having at least two unsaturated double bonds selected from the group consisting of epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and polyurethane (meth)acrylates, wherein said oligomeric substance is linear or branched;  
 b. 10 to 60 wt. % of at least one (meth)acrylate selected from the group consisting of monofunctional, difunctional, trifunctional and polyfunctional (meth)acrylate compounds;  
 c. 0.5 to 10 wt. % of at least one (meth)acrylate compound containing one or more phosphoric or carboxyl acidic functional groups;  
 d. 0.5 to 15 wt. % of at least one radical photoinitiator; and  
 e. up to 20 wt. % of at least one silane selected from the group consisting of dialkoxysilanes and trialkoxysilanes wherein said at least one silane contains at least one functional group other than alkoxy groups;  
   wherein 2.0 to 20 wt. %, based upon total coating material, of the monofunctional, difunctional, trifunctional and polyfunctional (meth)acrylate compounds are linear or branched; and    crosslinking the layer of coating material by means of UV radiation such that a formable, fingerprint resistant coating is formed.