Electro-optic displays, and materials for use therein

Abstract

A first electro-optic display comprises first and second substrates, and an adhesive layer and a layer of electro-optic material disposed between the first and second substrates, the adhesive layer comprising a mixture of a polymeric adhesive material and a hydroxyl containing polymer having a number average molecular weight not greater than about 5000. A second electro-optic display is similar to the first but has an adhesive layer comprising a thermally-activated cross-linking agent to reduce void growth when the display is subjected to temperature changes. A third electro-optic display, intended for writing with a stylus or similar instrument, is produced by forming a layer of an electro-optic material on an electrode; depositing a substantially solvent-free polymerizable liquid material over the electro-optic material; and polymerizing the polymerizable liquid material.

1 . A process for the preparation of an electro-optic display, the process comprising:
 forming a layer of an electro-optic material on an electrode;   depositing a layer of a substantially solvent-free polymerizable liquid material over the layer of electro-optic material;   placing a color filter over the layer of polymerizable liquid material; and   exposing the polymerizable liquid material to conditions effective to cause polymerization of the material, thereby forming a polymeric layer overlying the layer of electro-optic material and securing the color filter to the layer of electro-optic material.   
     
     
         2 . A process according to  claim 1  wherein the polymerizable liquid material is thermally curable and the conditions effective to cause polymerization of the material comprise heating the liquid material to a temperature high enough to cure the material. 
     
     
         3 . A process according to  claim 1  wherein the polymerizable liquid material is radiation curable and the conditions effective to cause polymerization of the material comprise exposing the liquid material to radiation of a wavelength effective to cure the material. 
     
     
         4 . A process according to  claim 1  wherein the polymerizable liquid material comprises an acrylate or a urethane acrylate blend or a silicone. 
     
     
         5 . A process according to  claim 1  further comprising controlling the thickness of the layer of polymerizable liquid material deposited on the layer of electro-optic material. 
     
     
         6 . A process according to  claim 5  wherein the thickness of the layer of polymerizable liquid material is controlled by doctor blade or die coating. 
     
     
         7 . A process according to  claim 5  wherein the thickness of the layer of polymerizable liquid material is controlled by first placing the color filter over the layer of polymerizable liquid material and thereafter passing a nip roller over the color filter prior to polymerizing the liquid material. 
     
     
         8 . A process according to  claim 1  wherein the thickness of the final polymeric layer is from about 6 to about 250 μm. 
     
     
         9 . A process according to  claim 8  wherein the thickness of the final polymeric layer is from about 8 to about 50 μm. 
     
     
         10 . A process according to  claim 1  wherein the electro-optic material comprises a rotating bichromal member or electrochromic material. 
     
     
         11 . A process according to  claim 1  wherein the electro-optic material comprises an electrophoretic material comprising a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field. 
     
     
         12 . A process according to  claim 11  wherein the electrically charged particles and the fluid are confined within a plurality of capsules or microcells. 
     
     
         13 . A process according to  claim 11  wherein the electrically charged particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material. 
     
     
         14 . A process according to  claim 11  wherein the fluid is gaseous. 
     
     
         15 . An electro-optic display comprising:
 an electrode;   a layer of an electro-optic material disposed on the electrode;   a polymeric layer overlying the layer of electro-optic material, the polymeric layer comprising the polymerization product of a substantially solvent-free polymerizable liquid material; and   a color filter secured to the layer of electro-optic material by the polymeric layer.   
     
     
         16 . An electro-optic display according to  claim 15  wherein the thickness of the polymeric layer is from about 6 to about 250 μm. 
     
     
         17 . An electro-optic display according to  claim 16  wherein the thickness of the polymeric layer is from about 8 to about 50 μm. 
     
     
         18 . A process for the preparation of an electro-optic display, the process comprising:
 forming a layer of an electro-optic material on an electrode;   depositing a layer of a substantially solvent-free polymerizable liquid material over the layer of electro-optic material;   placing an electrically-conductive layer over the layer of polymerizable liquid material; and   exposing the polymerizable liquid material to conditions effective to cause polymerization of the material, thereby forming a polymeric layer overlying the layer of electro-optic material and securing the electrically-conductive layer to the layer of electro-optic material.   
     
     
         19 . An electro-optic display comprising:
 an electrode;   a layer of an electro-optic material disposed on the electrode;   a polymeric layer overlying the layer of electro-optic material, the polymeric layer comprising the polymerization product of a substantially solvent-free polymerizable liquid material; and   an electrically-conductive layer secured to the layer of electro-optic material by the polymeric layer.   
     
     
         20 . A process for the preparation of an electro-optic display, the process comprising:
 forming a layer of an electro-optic material on an electrode;   depositing a layer of a substantially solvent-free polymerizable liquid material over the layer of electro-optic material;   placing a release sheet over the layer of polymerizable liquid material;   exposing the polymerizable liquid material to conditions effective to cause polymerization of the material, thereby forming a polymeric layer overlying the layer of electro-optic material; and   removing the release sheet from the polymeric layer.   
     
     
         21 . An electro-optic display comprising:
 a layer of solid electro-optic material capable of changing at least one optical characteristic upon application of an electric field thereto;   a backplane comprising at least one electrode arranged to apply an electric field to the layer of electro-optic material; and   an adhesive layer disposed between the layer of electro-optic material and the backplane and adhesively securing the layer of electro-optic material to the backplane,   the adhesive layer comprising a thermally-activated cross-linking agent capable, upon exposure to an activation temperature, of cross-linking the adhesive layer.