Electro-optic display and materials for use therein

1. A polyurethane formed from an isocyanate, a polyether diol and a polyester diol, the polyester diol having a molecular weight less than about 2000, or comprising two polyester diol segments connected by a steric hindrance group, each of the polyester diol segments having a molecular weight less than about 2000, the molar ratio of polyether diol to polyester diol being in the range of from about 1:9 to about 9:1.

2. A polyurethane according to claim 1 wherein the molar ratio of polyether diol to polyester diol is in the range of from about 1:4 to about 4:1.

3. A polyurethane according to claim 1 wherein the polyester diol is a polycaprolactone diol having a molecular weight less than about 1500.

4. A polyurethane according to claim 1 wherein the polyester diol is a polycaprolactone diol comprising two polycaprolactone segments connected by a bending group, each of the polycaprolactone segments having a molecular weight not greater than about 1500.

5. A polyurethane according to claim 1 wherein the isocyanate is 4,4′-methylenebis(cyclohexyl isocyanate).

6. A polyurethane according to claim 1 wherein the polyether diol is a poly(propylene oxide) diol.

7. A polyurethane according to claim 1 wherein the polyether diol has a molecular weight in the range of from about 1000 to about 3000.

8. A polyurethane according to claim 1 having an isocyanate:hydroxyl ratio of less than about 1.3.

9. A polyurethane according to claim 1 having a crossover temperature in the range of from about 10 to about 90° C. at 1 Hz.

10. A polyurethane according to claim 9 having a crossover temperature in the range of from about 40 to about 80° C. at 1 Hz.

11. A polyurethane according to claim 1 in the form of an aqueous latex.

12. A sub-assembly for use in constructing an electro-optic display, the sub-assembly comprising a layer of a solid electro-optic material and a layer of lamination adhesive adhered to the layer of electro-optic material, the layer of lamination adhesive comprising a polyurethane according to claim 1 .

13. An electro-optic display comprising a sub-assembly according to claim 12 and at least one electrode arranged to apply an electric field to the layer of electro-optic material.

14. An electronic book reader, portable computer, tablet computer, cellular telephone, smart card, sign, watch, shelf label or flash drive comprising a display according to claim 13 .

15. A sub-assembly according to claim 12 further comprising:

a light-transmissive electrically-conductive layer on the opposed side of the layer of electro-optic material from the layer of lamination adhesive; and

a release sheet on the opposed side of the layer of lamination adhesive from the layer of electro-optic material.

16. A sub-assembly according to claim 12 further comprising:

a second adhesive layer on the opposed side of the layer of electro-optic material from the layer of lamination adhesive; and

a release sheet disposed on the opposed side of the second adhesive layer from the layer of electro-optic material.

17. A sub-assembly according to claim 12 further comprising:

on the opposed side of the layer of lamination adhesive from the layer of electro-optic material, at least one of a light-transmissive protective layer and a light-transmissive electrically-conductive layer; and

a release sheet on the opposed side of the layer of electro-optic material from the layer of lamination adhesive.

18. A sub-assembly according to claim 12 further comprising first and second release sheets covering the exposed surfaces of the layer of electro-optic material and the layer of lamination adhesive.