Multiple layer polymer interlayers having a melt fractured surface

Abstract

The present invention provides multiple layer interlayers having a soft inner polymer layer and relatively stiff outer layers that can be laminated without unacceptable optical distortion and used in various multiple layer glass panel type applications. Multiple layer interlayers of the present invention have surface topography that is formed by controlling the melt fracture that occurs at the exposed surface of the interlayer, or individual layers of the multiple layer interlayer, during formation of the interlayer. By precisely controlling the surface topography of the interlayer, lamination of the interlayer with a rigid substrate does not lead to unacceptable optical distortion caused by the transfer of the surface topography through outer, stiffer layers into softer, internal layers of the interlayer.

1 . A polymer interlayer comprising:
 a first polymer layer comprising a plasticized thermoplastic polymer;   a second polymer layer comprising a plasticized thermoplastic polymer; and,   a third polymer layer comprising a plasticized thermoplastic polymer;   wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer;   wherein said first polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer;   wherein said third polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer; and, wherein the surface of said first polymer layer opposite said second polymer layer has an R Z  value of 20-60 that is imparted by melt fracture and an R SM  value of less than 800 that is imparted by melt fracture.   
     
     
         2 . The interlayer of  claim 1 , wherein the surface of said third polymer layer opposite said second polymer layer has an R Z  value of 20-60 that is imparted by melt fracture and an R SM  of less than 800 that is imparted by melt fracture. 
     
     
         3 . The interlayer of  claim 2 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         4 . The interlayer of  claim 2 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture, and wherein said surface of said third polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         5 . The interlayer of  claim 2 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50, and wherein said surface of said third polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         6 . The interlayer of  claim 1 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         7 . The interlayer of  claim 1 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         8 . A polymer interlayer produced by the process, comprising the steps:
 forming a first polymer melt, a second polymer melt, and a third polymer melt; and,   coextruding said first polymer melt, said second polymer melt, and said third polymer melt to form said interlayer;   whereby a surface of said interlayer has an R Z  of 20-50 that is imparted by melt fracture during said coextruding and an R SM  of less than 800 that is imparted by melt fracture during said coextruding;   wherein said first polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer; and,   wherein said third polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer.   
     
     
         9 . The interlayer of  claim 8 , wherein the surface of said third polymer layer opposite said second polymer layer has an R Z  value of 20-60 that is imparted by melt fracture and an R SM  of less than 800 that is imparted by melt fracture. 
     
     
         10 . The interlayer of  claim 9 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         11 . The interlayer of  claim 9 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture, and wherein said surface of said third polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         12 . The interlayer of  claim 9 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture, and wherein said surface of said third polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         13 . The interlayer of  claim 8 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         14 . The interlayer of  claim 8 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         15 . A multiple layer glass panel produced by the process, comprising the steps:
 providing a polymer interlayer comprising:
 a first polymer layer comprising a plasticized thermoplastic polymer; 
 a second polymer layer comprising a plasticized thermoplastic polymer; and, 
 a third polymer layer comprising a plasticized thermoplastic polymer; 
 wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer; 
 wherein said first polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer; 
 wherein said third polymer layer has a tensile break stress that is at least 15 kilograms per square centimeter greater than the tensile break stress of said second polymer layer; and, 
 wherein the surface of said first polymer layer opposite said second polymer layer has an R Z  value of 20-60 that is imparted by melt fracture and an R SM  value of less than 800 that is imparted by melt fracture; and, 
   laminating said polymer interlayer between two glass substrates to form said multiple layer glass panel.   
     
     
         16 . The interlayer of  claim 15 , wherein the surface of said third polymer layer opposite said second polymer layer has an R Z  value of 20-60 that is imparted by melt fracture and an R SM  of less than 800 that is imparted by melt fracture. 
     
     
         17 . The interlayer of  claim 16 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         18 . The interlayer of  claim 16 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture, and wherein said surface of said third polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         19 . The interlayer of  claim 16 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture, and wherein said surface of said third polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         20 . The interlayer of  claim 15 , wherein said surface of said first polymer layer opposite said second polymer layer has an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         21 . The interlayer of  claim 15 , wherein said surface of said first polymer layer opposite said second polymer layer has an R Z  value of 25-50 that is imparted by melt fracture.