Nano-structured surface coating process, nano-structured coatings and articles comprising the coating

Abstract

The invention relates to a new process for the preparation of nano-structured and/or nano-porous surfaces, coatings having a nano-structured and/or nano-porous surface and articles comprising said coatings. The invention also relates to the use of coatings according to the invention, in particular as anti-reflective coatings. The process for the preparation of the surface nano-structured and/or nano-porous coatings is a process comprising the steps of: a) applying a mixture to a substrate which mixture comprises: i) reactive nano-particles; ii) at least one solvent; iii) optionally a compound having at least one polymerisable group, in an amount that results in an increase in the transmission of at least 0.5%, for at least part of the electromagnetic spectrum between 400 and 800 nm, after the mixture has been applied and cured on a transparent substrate, in comparison with the same substrate without a coating; b) inducing crosslinking and/or polymerisation in the mixture applied to the substrate.

1 . A process for the preparation of a surface nano-structured and/or nano-porous coating or film comprising the steps of 
 a) applying a mixture to a substrate which mixture comprises 
 i) reactive nano-particles, having reactive organic groups on their surface,  
 ii) at least one solvent  
 iii) optionally a compound having at least one polymerisable group in an amount small enough to allow the formation of a nano-structures and/of nano-porous surface after polymerisation of the mixture  
   b) polymerising the mixture on the substrate.    
     
     
         2 . Process according to  claim 1 , wherein a mixture is used comprising a compound having at least one polymerisable group, in an amount that results in an increase in the transmission of at least 0.5%, for at least one wave length in the spectrum between 400 and 800 nm, after the mixture has been applied as a coating, in a thickness between 100 and 200nm, at one side of a transparent substrate, in comparison with the same substrate without a coating  
     
     
         3 . A process according to  claim 1 , wherein the reactive nano-particles are oxide particles.  
     
     
         4 . A process according to  claim 1  wherein the particles are silicon oxide or zirconium oxide particles.  
     
     
         5 . A process according to  claim 1 , wherein the reactive nano-particles are elongated.  
     
     
         6 . A process according to any one of  claim 5 , wherein the reactive nano-particles have an aspect ratio greater than 5.  
     
     
         7 . A process according to  claim 1 , wherein the reactive nano-particles have a length of less than 350 nm.  
     
     
         8 . A process according to  claim 1 , wherein the compound having at least one polymerisable group is an acrylate.  
     
     
         9 . A mixture according to  claim 1 , wherein the compound having at least one polymerisable group has two or more polymerisable groups.  
     
     
         10 . A process according to  claim 1 , wherein the poymerisation is achieved by applying UV-radiation.  
     
     
         11 . A mixture as defined in  claim 1 .  
     
     
         12 . A coating having a nano-structured and/or nano-porous surface obtainable by the process according to  claim 1 .  
     
     
         13 . A coating according to  claim 12  containing an amount of reactive nano-particles between 70-100 wt %, relative to the weight of the coating.  
     
     
         14 . A coating according to  claim 12 , having a thickness of between 50-200 nm.  
     
     
         15 . A coating according to  claim 12 , which coating increases the transmission by at least 0.5% for at least part of the electromagnetic spectrum between 400 and 800 nm if the coating is present on a transparent substrate in comparison with the same substrate without a coating.  
     
     
         16 . A coating according to  claim 15 , which coating increases the transmission by at least 1%, preferably by at least 2%.  
     
     
         17 . A coating according to  claim 12 , showing a static water contact angle of less than 60°, more preferably, less than 40°.  
     
     
         18 . A coating according to  claim 12 , showing a static water contact angle of more than 90°, more preferably, more than 120°.  
     
     
         19 . A coating according to  claim 18 , showing a contact angle of more than 90°, more preferably, more than 120° and most preferably, more than 140°.  
     
     
         20 . A coating prepared from a mixture comprising reactive nano-particles, a solvent and a compound having at least one polymerizable group, wherein the volume fraction of the compound having at least one polymerizable group is less than 1-the random close packing volume fraction of the reactive nano- particles.  
     
     
         21 . Use of a coating according to  claim 12  as an antireflective coating.  
     
     
         22 . Use of a coating obtainable by the process according to  claim 1  as a membrane.  
     
     
         23 . Use of the coating according to  claim 12  in a process of reverse sorption of at least one non-cross-linkable species.  
     
     
         24 . An article comprising a coating obtainable by the process according to  claim 1 .  
     
     
         25 . An article according to  claim 24 , which article is a display.  
     
     
         26 . An article according to  claim 25 , which article is an organic light emitting diode (OLED) display.  
     
     
         27 . An article according to  claim 24 , which article is a polarizer for a liquid crystal display (LCD).  
     
     
         28 . An article according to  claim 24 , which article is a polyethyleneterphtalate (PET) film or cellulosetriacetate (TAC) film.  
     
     
         29 . A display comprising the article according to  claim 28.