PROBLEM TO BE SOLVED: To provide a filler having a narrow particle size distribution in the filler having an average particle size of a primary particle of 0.01-1 &mum and having a small particle size (an average particle size of an aggregated particle is 3-18 &mum) in an organic-inorganic composite filler.SOLUTION: The organic-inorganic composite filler having a coefficient of variation of particle size of &le70% is obtained by a method wherein 100 pts.mass of inorganic aggregated particles formed by the aggregation of inorganic particle whose average particles size is 0.01-1 &mum and having an average particle size of 3-18 &mum and a coefficient of variation CV of particle size of &le70% is allowed to make contact with 10-30 pts.mass of a liquid polymerizable monomer under vacuum, then the pressure is recovered, then the polymerizable monomer is allowed to infiltrate into the aggregation gap of the primary particles, then the polymerizable monomer is polymerized and cured.COPYRIGHT: (C)2011,JPO&INPIT【課題】 有機無機複合フィラーにおいて、一次粒子の平均粒子径が0.01~1μmで、粒度の小さい(凝集粒子の平均粒子径3~18μm)ものにおいて、粒度分布幅が狭いものを提供する。【解決手段】 平均粒子径が0.01~1μmである無機粒子が凝集されてなる、平均粒子径が3~18μmで、粒度の変動係数CVが70%以下である無機凝集粒子の100質量部を、減圧下で、液状の重合性単量体の10~30質量部に接触させた後に復圧して、該重合性単量体を無機凝集粒子の一次粒子の凝集間隙に浸入させ、次いで、この重合性単量体を重合硬化させる方法により、粒度の変動係数が70%以下である、目的の有機無機複合フィラーを得る。【選択図】 なし
