High refractive index pressure-sensitive adhesives

Abstract

The present invention provides pressure-sensitive adhesives having a refractive index of at least 1.48. The pressure-sensitive adhesives comprise at least one monomer containing a substituted or an unsubstituted aromatic moiety.

1 . A pressure-sensitive adhesive comprising an aromatic monomer in an amount of at least 20 parts per 100 parts of total monomer, the aromatic monomer having the following formula:  
     
       
         
         
             
             
         
       
       wherein: 
 Ar is an aromatic group which is substituted with a substituent selected from the group consisting of Br y  and (R 3 ) z  
 wherein y represents the number of bromine substituents attached to the aromatic group and is an integer from 0 to 3;  
 R 3  is a straight or branched alkyl of 2 to 12 carbons; and  
 z represents the number of R 3  substituents attached to the aromatic ring and is an integer from 0 to 1, 
 provided that both y and z are not zero when Ar is substituted;  
 
 
 X is oxygen or sulfur;  
 n is 1 to 3;  
 R 1  is an unsubstituted straight or branched alkyl linking group of 6 to 12 carbons; and  
 R 2  is either H or CH 3 .  
 
     
   
   
       2 . The pressure-sensitive adhesive according to  claim 1 , wherein z is 1 and R 3  is a straight or branched alkyl of 2 to 8 carbons.  
   
   
       3 . The pressure-sensitive adhesive according to  claim 1 , wherein Ar is a naphthyl group.  
   
   
       4 . The pressure-sensitive adhesive according to  claim 1 , wherein n is 1.  
   
   
       5 . The pressure-sensitive adhesive according to  claim 1 , wherein X is oxygen.  
   
   
       6 . The pressure-sensitive adhesive according to  claim 1 , wherein the refractive index is at least 1.48.  
   
   
       7 . The pressure-sensitive adhesive according to  claim 1 , wherein the refractive index is at least 1.50.  
   
   
       8 . The pressure-sensitive adhesive according to  claim 1 , further comprising:  
     at least one acrylic monomer selected from the group consisting of monomeric acrylic or methacrylic acid ester of a non-tertiary alkyl alcohol of about 1 to about 12 carbons.  
   
   
       9 . The pressure-sensitive adhesive according to  claim 8 , wherein the acrylic monomer is selected from the group consisting of 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 1-methyl-1-butanol, 1-methyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 2-ethyl-1-hexanol, 3,5,5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, 1-dodecanol, and mixtures thereof.  
   
   
       10 . The pressure-sensitive adhesive according to  claim 1 , further comprising at least one polar monomer copolymerizable with the aromatic monomer(s).  
   
   
       12 . The pressure-sensitive adhesive according to  claim 10 , wherein the polar monomer(s) are selected from the group consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphoric acids, acrylamides, N,N-dialkyl substituted acrylamides, N-vinyl lactams, and N,N-dialkylaminoalkyl acrylates, ethylenically unsaturated nitriles, and mixtures thereof.  
   
   
       13 . The pressure-sensitive adhesive according to  claim 10 , wherein the polar monomer(s) are selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, and mixtures thereof.  
   
   
       14 . The pressure-sensitive adhesive according to  claim 1 , further comprising: 
 at least one acrylic monomer selected from the group consisting of monomeric acrylic or methacrylic acid ester of a non-tertiary alkyl alcohol of about 1 to about 12 carbons, and    at least one polar monomer copolymerizable with the aromatic monomer(s) and acrylic monomer(s).    
   
   
       15 . The pressure-sensitive adhesive according to  claim 1 , wherein the aromatic monomer is selected from the group consisting of 6-(4,6-dibromo-2-isopropyl phenoxy)-1-hexyl acrylate and 6-(4,6-dibromo-2-sec-butyl phenoxy)-1-hexyl acrylate.  
   
   
       16 . The pressure-sensitive adhesive according to  claim 1 , further comprising a crosslinker.  
   
   
       17 . The pressure-sensitive adhesive according to  claim 1 , further comprising one or more monomers selected from the group consisting of vinyl esters, vinyl acetate, 2-hydroxyethyl acrylate, styrene, and mixtures thereof.  
   
   
       18 . The pressure-sensitive adhesive according to  claim 1 , further comprising a tackifier.  
   
   
       19 . The pressure-sensitive adhesive according to  claim 1 , further comprising a plasticizer.  
   
   
       20 . A pressure-sensitive adhesive having an index of refraction of at least 1.50 and comprising an aromatic monomer having the following formula:  
     
       
         
         
             
             
         
       
       wherein: 
 Ar is napthyl which is unsubstituted or substituted with a substituent selected from the group consisting of Br y  and (R 3 ) z  
 wherein y represents the number of bromine substituents attached to the aromatic group and is an integer from 0 to 3;  
 R 3  is a straight or branched alkyl of 2 to 12 carbons; and  
 z represents the number of R 3  substituents attached to the aromatic ring and is an integer from 0 to 1, 
 provided that both y and z are not zero when Ar is substituted;  
 
 
 X is oxygen or sulfur;  
 n is 1 to 3;  
 R 1  is an unsubstituted straight or branched alkyl linking group of 2 to 12 carbons; and  
 R 2  is either H or CH 3 ;  
 
       copolymerized with at least one acrylic monomer selected from the group consisting of monomeric acrylic or methacrylic acid ester of a non-tertiary alkyl alcohol of about 4 to about 12 carbons and at least one polar monomer copolymerizable with the aromatic monomer(s) and acrylic monomer(s).