Method of preparing an anisotropic polymer film on a substrate with a structured surface

Abstract

An anisotropic polymer film with improved alignmentis prepared by coating onto a substrate with a structured surface. The polymer films thereby obtained are useful in optical and electrooptical devices for decorative and security applications.

1 . A method of preparing an anisotropic polymer film comprising a polymerized liquid crystal material with planar orientation, said process comprising: 
 coating a polymerizable liquid crystalline or mesogenic material onto a substrate with a structured surface,    aligning the polymerizable liquid crystalline or mesogenic material,    polymerizing the polymerizable liquid crystalline or mesogenic material, and    optionally removing the polymerized film from the substrate.    
     
     
         2 . A method according to  claim 1 , wherein the substrate surface comprises an area of fine grooves or grating, by which the molecules of said polymerizable liquid crystal material are homogeneously aligned with their molecular long axes substantially parallel to the substrate surface and substantially parallel to the direction of said fine grooves or grating.  
     
     
         3 . A method according to  claim 2 , wherein the direction of the fine grooves or grating is substantially the same over the entire substrate.  
     
     
         4 . A method according to  claim 2 , wherein the substrate comprises at least two areas having different direction of the fine grooves or grating.  
     
     
         5 . A method according to  claim 2 , wherein said grooves or grating have a width of 0.2 to 2.0 μm and a depth of 0.05 to 0.6 μm.  
     
     
         6 . A method according to  claim 3 , wherein said grooves or grating have a width of 0.2 to 2.0 μm and a depth of 0.05 to 0.6 μm.  
     
     
         7 . A method according to  claim 4 , wherein said grooves or grating have a width of 0.2 to 2.0 μm and a depth of 0.05 to 0.6 μm.  
     
     
         8 . A method according to  claim 2 , wherein said grooves or grating have a symmetrical profile.  
     
     
         9 . A method according to  claim 2 , wherein said grooves or grating have an asymmetrical profile.  
     
     
         10 . A method according to  claim 2 , wherein said grooves or grating have a profile that is rectangular, square, saw tooth, triangular, trapezoidal, sine wave or an approximation to these profiles.  
     
     
         11 . A method according to  claim 1 , wherein the substrate comprises a carrier layer.  
     
     
         12 . A method according to  claim 11 , wherein the substrate comprises one or more additional layers on the carrier layer.  
     
     
         13 . A method according to  claim 1 , wherein the structured surface of said substrate is formed by applying heat and pressure in combination with micro-engraved shims to the substrate.  
     
     
         14 . A method according to  claim 1 , wherein the structured surface of said substrate is formed by interferography, photolithography, embossing, ion beam etching, electron beam etching, ruling or cast curing.  
     
     
         15 . An anisotropic polymer film with planar alignment obtained by a method according to caim  1 .  
     
     
         16 . In an optical or electrooptical devices, for decorative or security applications, comprising an anisotropic polymer film, the improvement wherein said film is according to  claim 15 .  
     
     
         17 . In an optical retardation or compensation film, quarter wave foil, or polariser comprising an anisotropic polymer film, the improvement wherein said film is according to  claim 15 .  
     
     
         18 . In a liquid crystal display comprising an anisotropic polymer film, the improvement wherein said film is according to  claim 15 .  
     
     
         19 . In a liquid crystal display comprising a retardation or compensation film, quarter wave foil or polariser, the improvement wherein said retardation or compensation film, quarter wave foil or polariser is according to  claim 17 .  
     
     
         20 . In a security marking or device comprising an anisotropic polymer film, the improvement wherein said film is according to  claim 15 .  
     
     
         21 . In a hot stamping foil, laminate, label, data carrier, document of value, ID or credit card, banknote, security thread, cheque or CD comprising a security marking or device, the improvement wherein said security marking or device is according to  claim 20 .  
     
     
         22 . A method of aligning a liquid crystalline or mesogenic material in a continuous coating process on a conveying substrate comprising orienting the molecular long axes of the molecules of the liquid crystalline or mesogenic material to be substantially parallel to the plane of the substrate and at any desired angle to the substrate moving direction by using a substrate with a structured surface.