Composition and process for the sealing of microcups in roll-to-roll display manufacturing

Abstract

The invention relates to a novel sealing composition for the manufacture of an electrophoretic or liquid crystal display, and a sealing process using the composition. The composition allows electrophoretic or liquid crystal cells to be seamlessly sealed and the sealing layer free of any defects.

What is claimed is:  
     
         1 . A composition suitable for sealing electrophoretic cells, which composition comprises: 
 a) a solvent or solvent mixture which is immiscible with the display fluid contained within the cells and exhibits a specific gravity less than that of the display fluid, and    b) a thermoplastic elastomer.    
     
     
         2 . The composition of  claim 1  wherein said solvent or solvent mixture has a surface tension of lower than 35 dyne/cm.  
     
     
         3 . The composition of  claim 2  wherein said solvent or solvent mixture has a surface tension of lower than 30 dyne/cm.  
     
     
         4 . The composition of claim I wherein said solvent or solvent mixture is selected from a group consisting of alkanes, cyclic alkanes, alkylbenzenes, alkyl esters and C 3-5  alkyl alcohols.  
     
     
         5 . The composition of  claim 4  wherein said solvent is heptane, octane, nonane, cyclohexane, decalin, toluene, xylene, and their isomers, and mixtures thereof.  
     
     
         6 . The composition of  claim 1  wherein said thermoplastic elastomer is selected from a group consisting of ABA and (AB)n types of di -block, tri-block and multi-block copolymers, in which: 
 A is styrene, α-methylstyrene, ethylene, propylene or norbonen e,  
 B is butadiene, isoprene, ethylene, propylene, butylene, dimethylsiloxane or propylene sulfide, and A and B are not the same, and  
 n is≧1.  
 
     
     
         7 . The composition of  claim 6  wherein n is 1-10.  
     
     
         8 . The composition of  claim 6  wherein said thermoplastic elastomer is poly(styrene-b-butadiene), (poly(styrene-b-butadiene-b-styrene), poly(styrene-b-isoprene-b-styrene), poly(styrene-b-ethylene/butylenes-b-styrene), poly(styrene-b-dimethylsiloxane-b-styrene), poly((α-methylstyrene-b-isoprene), poly(α-methylstyrene-b-isoprene-b-α-methylstyrene), poly(α-methylstyrene-b-propylene sulfide-b-α-methylstyrene), poly((α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene), and their grafted co-polymers and derivatives thereof.  
     
     
         9 . The composition of  claim 1  wherein the thermoplastic elastomer is poly(ethylene-co-propylene-co-5-methylene-2-norbomene), (ethylene-propylene-diene terpolymer), and their grafted co-polymers and derivatives thereof.  
     
     
         10 . The composition of  claim 1 , further comprising a thermoplastic material that is compatible with one of the blocks of the thermoplastic elastomer.  
     
     
         11 . The composition of  claim 10  wherein the thermoplastic material is selected from the group consisting of polystyrene and poly ((α-methylstyrene).  
     
     
         12 . The composition of  claim 1 , further comprising a wetting agent.  
     
     
         13 . The composition of  claim 12  wherein said wetting agent is selected from a group consisting of surfactants, ZONYL fluorosurfactants, fluoroacrylates, fluoromethacrylates, fluoro-substituted long chain alcohols, perfluoro-substituted long chain carboxylic acids, SILWET silicone surfactants and their derivatives.  
     
     
         14 . The composition of  claim 1 , further comprising one or more of the following agents: a crosslinking agent, a vulcanizer, a multifunctional monomer or oligomer, a thermal initiator or a photoinitiator.  
     
     
         15 . The composition of  claim 14  wherein said crosslinking agent is a bisazide such as 4,4′-diazidodiphenylmethane, or 2,6-di-(4′-azidobenzal)-4-methylcyclohexanone), and said vulcanizer is a disulfide such as 2-benzothiazolyl disulfide, or tetramethylthiuram disulfide.  
     
     
         16 . A sealing process for the preparation of electrophoretic display, which process comprises: 
 a) filling an array of microcups with an electrophoretic fluid;    b) overcoating the electrophoretic fluid with a sealing composition comprising: 
 a solvent or solvent mixture which is immiscible with the display fluid contained within the cells and exhibits a specific gravity less than that of the display fluid,  
 thermoplastic elastomer; and  
   c) allowing the sealing composition to dry to form a sealing layer.    
     
     
         17 . The process of  claim 16 , further comprising exposing the sealing layer to UV radiation or thermal baking.  
     
     
         18 . The process of  claim 16  wherein said solvent or solvent mixture has a surface tension of lower than 35 dyne/cm.  
     
     
         19 . The process of  claim 18  wherein said solvent or solvent mixture has a surface tension of lower than 30 dyne/cm.  
     
     
         20 . The process of  claim 16  wherein said solvent or solvent mixture is selected from a group consisting of alkanes, cyclic alkanes, alkylbenzenes, alkyl esters and C 3-5  alkyl alcohols.  
     
     
         21 . The process of  claim 20  wherein said solvent is heptane, octane, nonane, cyclohexane, decalin, toluene, xylene, and their isomers, and mixtures thereof.  
     
     
         22 . The process of  claim 16  wherein said thermoplastic elastomer is selected from a group consisting of ABA and (AB)n types of di-block, tri-block and multi-block copolymers, in which: 
 A is styrene, α-methylstyrene, ethylene, propylene or norbonene,  
 B is butadiene, isoprene, ethylene, propylene, butylene, dimethylsiloxane or propylene sulfide, and A and B are not the same, and  
 n is≧1.  
 
     
     
         23 . The process of  claim 22  wherein n is 1-10.  
     
     
         24 . The process of  claim 16  wherein said thermoplastic elastomer is poly(styrene-b-butadiene), (poly(styrene-b-butadiene-b-styrene), poly(styrene-b-isoprene-b-styrene), poly(styrene-b-ethylene/butylenes-b-styrene), poly(styrene-b-dimethylsiloxane-b-styrene), poly(α-methylstyrene-b-isoprene), poly(α-mthylstyrene-b-isoprene-b-α-methylstyrene), poly(α-methylstyrene-b-propylene sulfide-b-α-methylstyrene), poly(α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene), and their grafted co-polymers and derivatives thereof.  
     
     
         25 . The process of  claim 16  wherein the thermoplastic elastomer is poly(ethylene-co-propylene-co-5-methylene-2-norbornene), (ethylene-propylene-diene terpolymer), and their grafted co-polymers and derivatives thereof.  
     
     
         26 . The process of  claim 16 , further comprising a thermoplastic material that is compatible with one of the blocks of the thermoplastic elastomer.  
     
     
         27 . The process of  claim 26  wherein the thermoplastic material is selected from the group consisting of polystyrene and poly ((α-methylstyrene).  
     
     
         28 . The process of  claim 16 , further comprising a wetting agent.  
     
     
         29 . The process of  claim 28  wherein said wetting agent is selected from a group consisting of surfactants, ZONYL fluorosurfactants, fluoroacrylates, fluoromethacrylates, fluoro-substituted long chain alcohols, perfluoro-substituted long chain carboxylic acids, SILWET silicone surfactants and their derivatives.  
     
     
         30 . The process of  claim 16 , further comprising one or more of the following agents: a crosslinking agent, a vulcanizer, a multifunctional monomer or oligomer, a thermal initiator or a photoinitiator.  
     
     
         31 . The process of claim  30  wherein said crosslinking agent is a bisazide such as 4,4′-diazidodiphenylmethane, or 2,6-di-(4′-azidobenzal)-4-methylcyclohexanone), and said vulcanizer is a disulfide such as 2-benzothiazolyl disulfide, or tetramethylthiuram disulfide.