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

1. A method for sealing microcups filled with a display fluid, which method comprises:

a) forming microcups by microembossing or photolithographing, wherein each of the microcups has a floor, partition walls, and a top opening;

b) filling the microcups with a display fluid through the top openings of the microcups;

c) forming a sealing composition comprising a thermoplastic elastomer in a solvent or solvent mixture;

d) coating the sealing composition on top of the display fluid through the top openings; and

e) drying the sealing composition to form a sealing layer, wherein the sealing layer is on top of the display fluid and seals the top openings of the microcups.

2. The method of claim 1 wherein said solvent or solvent mixture is immiscible with the display fluid.

3. The method of claim 1 wherein said solvent or solvent mixture has a specific gravity equal to or lower than that of the display fluid.

4. The method of claim 3 wherein said solvent or solvent mixture has a specific gravity lower than that of the display fluid.

5. The method of claim 1 wherein said thermoplastic elastomer has a specific gravity lower than that of the display fluid.

6. The method of claim 1 wherein said solvent or solvent mixture has a surface tension of lower than 35 dyne/cm.

7. The method of claim 6 wherein said solvent or solvent mixture has a surface tension of lower than 30 dyne/cm.

8. The method of claim 1 wherein said solvent or solvent mixture is selected from the group consisting of alkanes, cyclic alkanes, alkylbenzenes, alkyl esters and C 3-5 alkyl alcohols.

9. The method of claim 8 wherein said solvent or solvent mixture is selected from the group consisting of heptane, octane, nonane, cyclohexane, decalin, toluene, xylene, and any mixture thereof.

10. The method of claim 1 wherein said thermoplastic elastomer is selected from the 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 norbornene,

B is butadiene, isoprene, ethylene, propylene, butylene, dimethylsiloxane or propylene sulfide, and A and B are not the same, and n is ≧1.

11. The method of claim 10 wherein n is 1-10.

12. The method of claim 10 wherein said sealing composition further comprises a thermoplastic material that is compatible with one of the blocks of the thermoplastic elastomer.

13. The method of claim 1 wherein said thermoplastic elastomer is selected from the group consisting of 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), their grafted co-polymers and derivatives thereof.

14. The method of claim 1 wherein the thermoplastic elastomer is selected from the group consisting of poly(ethylene-co-propylene-co-5-methylene-2-norbornene), ethylene propylene-diene terpolymer, their grafted co-polymers and derivatives thereof.

15. The method of claim 1 wherein said sealing composition further comprises a wetting agent.

16. The method of claim 1 wherein said sealing composition further comprises one or more of the following agents: a crosslinking agent, a vulcanizer, a multifunctional monomer or oligomer, a thermal initiator or a photoinitiator.

17. The method of claim 1 further comprising exposing said sealing layer to UV radiation or thermal baking.

18. The method of claim 1 wherein said display fluid is an electrophoretic fluid.

19. The method of claim 1 wherein said display fluid is a liquid crystal composition.