Hydrophilic coating solutions were prepared by reacting a silane coupling agent, GPTMS (3-glycidoxypropyl trimethoxysilane) with colloidal silica. Hydrophilic coating films were also obtained by depositing the hydrophilic coating solutions on polycarbonate substrates by spin-coating and subsequently by thermal curing at 120 °C. During this process, the effect of average particle sizes of colloidal silica was studied on the properties of coating films. As a result, coating film, prepared from colloidal silica with average particle size of 25 nm, showed a low contact angle of 20° and a good pencil hardness of H. On the other hand, coating films, prepared from colloidal silica with average particle sizes of 15 nm and 45 nm, exhibited high contact angles of 27° and 36° and pencil hardness of H and B, respectively.