Ricoh Company, Ltd.

Kohsuke Satoh

Tsuneyasu Nagatomo

Keiji Makabe

Daichi Hisakuni

Kenji Yoneda

Junichi Watanabe

Kousuke Suzuki

Tetsuya Tanaka

Masahiro Kawamoto

Natsuko Matsushita

Shintaro Akiyama

An image forming apparatus is provided that includes: an image bearer; a charger; an irradiator; a developing device containing a toner; and a transfer device. The image bearer has a Martens hardness of from 185 to 250 N/m. The toner satisfies a relation 0.13&#x2264;X/Dn&#x2264;0.16, where X [&#x3bc;m] represents an average value of an amount of deformation of the toner by micro-indentation at when a load reaches 3.00&#xd7;10N at a loading rate of 3.0&#xd7;10N/sec under an environment of 32 degrees C. and 40% RH, and Dn [&#x3bc;m] represents a number average particle diameter of the toner. The toner contains an external additive comprising silica particles and particles composed mainly of strontium titanate. The particles composed mainly of strontium titanate further contain a third element M selected from the group consisting of La, Mg, Ca, Sn, and Si.

Image forming apparatus and image forming method

A toner including toner particles, each toner particle including a toner base particle, and inorganic particles, wherein the inorganic particles include particles of a fluorine-containing aluminium compound, and a liberation ratio of the inorganic particles is 10% or greater but 60% or less.

Toner, toner stored unit, developer, developer stored unit, and image forming apparatus

A toner is provided. The toner includes toner particles each including a mother particle and external additive particles covering the mother particle. In a SEM image of the toner, toner particles having a ratio Sd/St of from 5% to 50% are present at a frequency of 15% or more, where Sd representing an area of a largest recessed portion D of each toner particle and St representing whole area of the toner particle, Sd and St determined from the SEM image magnified and binarized to discriminate recessed portions and projected portions of the toner particle from each other. An external additive coverage rate Ca at the largest recessed portion D is from 30% to 100%.

Toner, developer, toner storage unit, and image forming apparatus

A toner includes a base particle; and an external additive covering the base particle. The toner includes a tetrahydrofuran (THF)-insoluble component having a glass transition temperature determined from a DSC curve when heated for the second time of from &#x2212;50&#xb0; C. to 10&#xb0; C. and an average circularity not greater than 0.98, and satisfies the following relation:&#x2212;0.025&#xd7;&#x2266;1.80

Toner, developer, image forming apparatus, and process cartridge

A toner includes a base particle comprising a crystalline polyester resin; and an external additive which is a group of silica particles having a number-average particle diameter of from 0.01 &#x3bc;m to 0.11 &#x3bc;m on the surface of the toner. A number ratio of the silica particles having a circularity not less than 0.8 is 20% or more in the total number of the silica particles.

Toner, developer, and image forming apparatus

A method of manufacturing toner including mixing mother toner particles containing a binder resin and a coloring agent and first particles having an average primary particle diameter of from 100 nm to 1 &#x3bc;m to using a mixer including a rotary shaft member, multiple stirring members provided to the surface of the shaft member, and a casing to cover the multiple stirring members, wherein the cross section of the inner periphery of the casing relative to a direction perpendicular to the rotation axis of the shaft member is circular around the rotation axis with a substantially constant distance between the inner periphery and the rotation axis. The casing covers the multiple stirring members and a cooling jacket is provided to at least part of the outer periphery of the casing. The weight ratio of the particles to the mother toner particles is from 1.5% to 10%.

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Shizuoka, Japan

Kohsuke Satoh