Display medium and display device

1. A display medium comprising:

a pair of substrates having electrodes and disposed to form a space therebetween, at least one of the substrates transmitting light;

a dispersion medium enclosed between the substrates;

a group of particles that is dispersed in the dispersion medium and that moves in the dispersion medium according to an electric field applied between the substrates; and

a treatment layer provided on at least one of surfaces of the substrates that oppose each other, the treatment layer comprising a polymer compound having a silicone chain as a side chain thereof.

2. The display medium according to claim 1 , wherein the polymer compound having a silicone chain is a reactive silicone polymer compound.

3. The display medium according to claim 2 , wherein the reactive silicone polymer compound is a copolymer of monomers including, at least, a monomer having a silicone chain and a monomer having a reactive group.

4. The display medium according to claim 3 , wherein the copolymerization ratio of the monomer having a silicone chain is 50% by weight or more with respect to the weight of the copolymer.

5. The display medium according to claim 3 , wherein the copolymerization ratio of the monomer having a silicone chain is 80% by weight or more with respect to the weight of the copolymer.

6. The display medium according to claim 3 , wherein the copolymerization of the monomer having a reactive group is in the range of from 0.1% by weight to 10% by weight with respect to the weight of the copolymer.

7. The display medium according to claim 3 , wherein the monomer having a reactive group is glycidyl(meth)acrylate having an epoxy group or an isocyanate monomer having an isocyanate group.

8. The display medium according to claim 2 , wherein the treatment layer has a thickness of about 0.001 μm to 10 μm.

9. The display medium according to claim 1 , wherein the polymer compound having a silicone chain is a non-reactive silicone polymer compound.

10. The display medium according to claim 9 , wherein the non-reactive silicone polymer compound is a copolymer of monomers including at least a monomer having a silicone chain and a monomer having no reactive group.

11. The display medium according to claim 10 , wherein the copolymerization ratio of the monomer having a silicone chain is from 0.01% to 95% by weight with respect to the weight of the copolymer.

12. The display medium according to claim 10 , wherein the copolymerization ratio of the monomer having a silicone chain is from 0.1% to 80% by weight with respect to the weight of the copolymer.

13. The display medium according to claim 9 , wherein the treatment layer has a thickness of about 0.01 μm to 10 μm.

14. The display medium according to claim 1 , wherein the pair of substrates are a display substrate and a rear substrate, and the treatment layer is formed at least on a surface of the display substrate opposing the rear substrate.

15. The display medium according to claim 1 , further comprising a spacing member partitioning the space between the substrates and having the treatment layer on a surface thereof.

16. The display medium according to claim 1 , wherein the dispersion medium is silicone oil.

17. The display medium according to claim 1 , further comprising, in the dispersion medium, another group of particles having a larger volume average particle diameter than the group of particles and having a different optical reflection properties from the group of particles.

18. A display device comprising:

the display medium according to claim 1 ; and

a voltage applying unit that applies a voltage between the substrates.