Patent ID: 7129293

Claim:
Polymer fine particles derived from a crosslinked polymer having main chains formed of ethylenically unsaturated polymerizable groups and crosslinkages between said main chains, which are characterized in that said main chain comprises (i) side chains each of N, N-di-C 1-6 alkyl-substituted amino group covalently bonded to said main chain via a linker formed of 1–10 atoms, and (ii) side chains each of a hydrophilic group having a poly(ethylene glycol) segment which is covalently bonded to said main chain, independently of each other; the polymer fine particles thus forming core-shell type fine particles when solubilized or dispersed in an aqueous medium, said side chains (i) and the main chains chiefly forming the core parts and the side chains (ii) chiefly forming the shell parts.