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

1. A method for sealing microcups filled with an electrophoretic display fluid, which method comprises overcoating said electrophoretic display fluid with a sealing composition comprising:

a) a solvent or solvent mixture which is immiscible with the electrophoretic display fluid contained within the microcups and exhibits a specific gravity less than that of the electrophoretic display fluid, and

b) a thermoplastic elastomer.

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

3. The method of claim 2 wherein said solvent or solvent mixture has a surface tension of lower than 30 dyne/cm.

4. 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.

5. The method of claim 4 wherein said solvent or solvent mixture is selected from the group consisting of heptane, octane, nonane, cyclohexane, decalin, toluene, xylene, their isomers and mixtures thereof.

6. 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 norbornene,

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 method of claim 6 wherein n is 1–10.

8. 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.

9. 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.

10. The method of claim 8 wherein said sealing composition further comprises a thermoplastic material that is compatible with one of the blocks of the thermoplastic elastomer.

11. The method of claim 10 wherein the thermoplastic material is selected from the group consisting of polystyrene and poly (α-methylstyrene).

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

13. The method of claim 12 wherein said wetting agent is selected from the 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 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.

15. The method of claim 14 wherein said crosslinking agent is a bisazide.

16. The method of claim 15 wherein said bisazide is 4,4′-diazidodiphenylmethane or 2,6-di-(4′-azidobenzal)-4-methylcyclohexanone).

17. The method of claim 14 wherein said vulcanizer is a disulfide.

18. The method of claim 17 wherein said disulfide is 2-benzothiazolyl disulfide or tetramethylthiuram disulfide.

19. The method of claim 1 further comprising drying said sealing composition to form a sealing layer.

20. The method of claim 19 further comprising exposing said sealing layer to UV radiation or thermal baking.

21. The method of claim 6 wherein said ABA or (AB)n block copolymer further comprises a third comonomer.