MAGNETIC TONER

• Main Authors: HOTTA YOJIRO, NISHIKAWA KOJI, TERAUCHI KAZUO, YAMAZAKI KATSUHISA, TSUDA SHOHEI, SHIOZAWA MOTOHIDE, ITAKURA TAKAYUKI, NAKA TAKESHI
• Format: Patent
• Language: English; Japanese
• Published: 12.03.2015
• Subjects: CINEMATOGRAPHY; ELECTROGRAPHY; ELECTROPHOTOGRAPHY; HOLOGRAPHY; MAGNETOGRAPHY; PHOTOGRAPHY; PHYSICS

PROBLEM TO BE SOLVED: To provide a toner capable of obtaining stable image concentration through durability, hardly causing wave formation to occur, and at the same time exhibiting excellent low-temperature fixability, making the toner easily applicable for speed-up and life extension.SOLUTION: Provided is a magnetic toner having toner particles containing binder resin and magnetic substance and having inorganic fine particles a and organic inorganic composite particles on the surface of the toner particles, the magnetic toner being characterized in that the organic inorganic composite particles i) have such a structure that inorganic fine particle b are buried in resin particles and ii) are included 0.5 mass% to 3.0 mass% inclusive on the basis of a mass of the toner, the inorganic fine particles a contain at least inorganic oxide fine particles selected from the group consisting of silica fine particles, titanium oxide fine particles, and alumina fine particles, in which the number average particle diameter (D1) is 5 nm to 25 nm inclusive, and 85 mass% or more of the inorganic oxide fine particles are silica fine particles. Letting a coverage factor of toner particle surfaces by inorganic fine particles a be a coverage factor A(%) and a coverage factor by inorganic particles a stuck to toner particle surfaces be a coverage factor B(%), then the coverage factor A is 45.0% to 70.0% inclusive, and a ratio (B/A) of the coverage factor B to the coverage factor A is 0.50 to 0.85 inclusive. 【課題】耐久を通じて安定した画像濃度を得られ、掃き寄せが発生しにくく、同時に優れた低温定着性を発揮することで、高速かつ長寿命化に適用しやすいトナーを提供すること。【解決手段】結着樹脂、磁性体を含有するトナー粒子と、該トナー粒子表面に無機微粒子ａ及び有機無機複合粒子を有する磁性トナーであって、該有機無機複合粒子は、ｉ）樹脂粒子に無機微粒子ｂが埋め込まれた構造を有し、ｉｉ）該トナー質量を基準として、０．５質量％以上３．０質量％以下含有されており、該無機微粒子ａは、シリカ微粒子、酸化チタン微粒子及びアルミナ微粒子からなる群より選択される無機酸化物微粒子を少なくとも含有し、個数平均粒径（Ｄ１）が５ｎｍ以上２５ｎｍ以下であり、該無機酸化物微粒子中の８５質量％以上がシリカ微粒子であり、無機微粒子ａによるトナー粒子表面の被覆率を被覆率Ａ（％）とし、トナー粒子表面に固着された無機微粒子ａによる被覆率をＢ（％）とした時に、該被覆率Ａが４５．０％以上７０．０％以下であり、該被覆率Ｂの被覆率Ａに対する比（Ｂ／Ａ）が０．５０以上０．８５以下であることを特徴とする。【選択図】なし