Multilayer optical adhesives and methods of making same

Abstract

A multilayer optical adhesive including a first viscoelastic or elastomeric adhesive layer and a second viscoelastic or elastomeric adhesive layer. A crosslinked or soluble resin layer may be disposed between the first viscoelastic or elastomeric adhesive layer and the second viscoelastic or elastomeric adhesive layer or the first viscoelastic or elastomeric adhesive layer may be immediately adjacent to the second viscoelastic or elastomeric adhesive layer. An interface between immediately adjacent layers is structured and there is a difference in refractive indices across the interface.

What is claimed is: 
     
         1 . An optical adhesive comprising:
 a viscoelastic or elastomeric adhesive layer having a first major surface and having a first refractive index n 1 ;   a discontinuous layer immediately adjacent the first major surface of the viscoelastic or elastomeric adhesive layer, the discontinuous layer having a second refractive index n 2  different from n 1 ;   an additional layer disposed immediately adjacent the discontinuous layer opposite the viscoelastic or elastomeric adhesive layer, the additional layer having a third refractive index n 3 , the additional layer in contact with the viscoelastic or elastomeric adhesive layer,   wherein a first interface between the viscoelastic or elastomeric adhesive layer and the discontinuous layer, a second interface between the additional layer and the discontinuous layer, and a third interface between the viscoelastic or elastomeric adhesive layer and the additional layer comprise a grating having a peak to valley height h and a pitch and wherein h multiplied by |n 1 -n 2 | is in a range of about 150 nm to about 350 nm and the pitch is in a range of about 2 microns to about 50 microns.   
     
     
         2 . The optical adhesive of  claim 1 , wherein the viscoelastic or elastomeric adhesive layer is a viscoelastic optically clear adhesive. 
     
     
         3 . The optical adhesive of  claim 1 , wherein |n 1 -n 2 | is at least 0.001 and less than 0.5. 
     
     
         4 . The optical adhesive of  claim 1 , wherein the additional layer comprises a viscoelastic or elastomeric adhesive. 
     
     
         5 . The optical adhesive of  claim 1 , wherein the additional layer is a glass layer. 
     
     
         6 . The optical adhesive of  claim 1 , wherein the additional layer is a release liner. 
     
     
         7 . The optical adhesive of  claim 1 , wherein the discontinuous layer comprises a plurality of discrete objects arranged in a pattern. 
     
     
         8 . The optical adhesive of  claim 7 , wherein the plurality of discrete objects comprises dots, cross-hatches, ribs, rectangular parallelepipeds, or a combination thereof. 
     
     
         9 . The optical adhesive of  claim 1 , wherein h multiplied by |n 1 -n 2 | is in a range of about 200 nm to about 300 nm and the pitch is in a range of about 4 microns to about 40 microns. 
     
     
         10 . A method of making an optical adhesive, comprising the steps of:
 providing a first release tool having a structured first release surface;   coating a first material onto the structured first release surface thereby forming a first layer having a first refractive index; and   applying a second material and a second release tool having a second release surface onto the first material, the second material immediately adjacent the first material opposite the first release tool, the second release tool immediately adjacent the second material opposite the first material, the second release surface facing the second material, the second material forming a second layer having a second refractive index;   removing the first release tool thereby exposing a structured major surface of the first layer, and   applying a third material onto the structured major surface, the third material forming a third layer having a third refractive index different from the first refractive index,   wherein the first material is a first coatable resin and the second material is a first viscoelastic or elastomeric adhesive.   
     
     
         11 . The method of  claim 10 , wherein the third material is a second viscoelastic or elastomeric adhesive. 
     
     
         12 . The method of  claim 10 , wherein the third material is a second coatable resin. 
     
     
         13 . The method of  claim 10 , wherein the step of applying the third material includes the steps of:
 coating the third material onto a third release surface of a third release tool thereby forming a coated release tool, and   applying the coated release tool onto the structured major surface, the third material facing the structured major surface.   
     
     
         14 . The method of  claim 13 , wherein the third release surface is structured. 
     
     
         15 . A method of making an optical adhesive, comprising the steps of:
 providing a first release tool having a structured first release surface;   coating a first material onto the structured first release surface thereby forming a first layer having a first refractive index;   applying a second release tool having a second release surface onto the first layer, the second release surface immediately adjacent the first layer opposite the first release tool;   removing the first release tool thereby exposing a first structured surface of the first layer, and   applying a first viscoelastic or elastomeric adhesive onto the first structured surface, the first viscoelastic or elastomeric adhesive forming a second layer having a second refractive index different from the first refractive index.   
     
     
         16 . The method of  claim 15 , wherein the first material is a second viscoelastic or elastomeric adhesive. 
     
     
         17 . The method of  claim 15 , further comprising the step of applying a third release tool having a third release surface to the first viscoelastic or elastomeric adhesive, the third release surface immediately adjacent the first viscoelastic or elastomeric adhesive. 
     
     
         18 . The method of  claim 15 , wherein the step of applying the first viscoelastic or elastomeric resin comprises the steps of:
 coating the first viscoelastic or elastomeric resin onto a third release surface of a third release tool thereby forming a coated release tool, and   applying the coated release tool onto the first structured surface, the first viscoelastic or elastomeric resin facing the first structured surface.   
     
     
         19 . The method of  claim 15 , wherein the second release surface is a structured surface. 
     
     
         20 . The method of  claim 19 , further comprising the steps of:
 removing the second release tool, thereby exposing a second structured surface of the first layer, and   applying a second viscoelastic or elastomeric adhesive onto the second structured surface thereby forming a third layer having a third refractive index.