PROBLEM TO BE SOLVED: To provide a nanoparticle that neither causes flocculation nor deposition, is re-dispersable in water, and is excellent in water dispersibility even if it is dried from a water dispersion liquid.SOLUTION: A nanoparticle that is not melt in coating condition and whose gel-liquid crystal phase transition temperature is higher than room temperature and is lower than the boiling temperature of water is used as an amphiphilic compound used for water dispersion coating agent of nanoparticle, and a film composed of a stable crystalline amphiphilic compound can be formed on the surface of the nanoparticle by stirring and mixing the liquid while heating the same liquid at a temperature of the phase transition temperature or higher after the amphiphilic compound and water are added to the nanoparticle.COPYRIGHT: (C)2011,JPO&INPIT【課題】水分散液から乾燥しても、凝集、溶着を起こさず、水に再分散が可能で、水分散性の良好なナノ微粒子を提供する。【解決手段】ナノ粒子の水分散コーティング剤に用いる両親媒性化合物として、コーティング状態で溶解せず、ゲル-液晶相転移温度が室温より高く、水の沸点より低いものを用い、ナノ粒子に、該両親媒性物質及び水を加えた後、前記相転移温度以上に加熱しながら攪拌混合することにより、ナノ粒子表面に安定な結晶性の両親媒性化合物からなる皮膜を形成することができる。【選択図】図1
