Toner for electrophotography, image forming apparatus, and toner manufacturing method

An image forming apparatus comprising:

• an image carrier on which a latent image is formed;
• a developing unit that forms a toner image by supplying a toner to the latent image formed on the image carrier;
• and
• a transfer unit including an intermediate transfer member unit on which of the toner image is transferred from the image carrier, wherein
• the toner is a toner for electrophotography satisfying
• Ft/Dt≦3.0 [nN/μm]
• where Ft is an inter-toner non-electrostatic adhesion force after a compressive stress within 0.7×10−2 N/m2 to 1.5×10−2 N/m2 is applied, and Dt is a toner particle diameter, and
• the inter-toner non-electrostatic adhesion force is obtained by filling a two-dividable cell for an Agrobot manufactured by Hosokawa Micron Corporation having a diameter of 15 millimeters, measuring a tension rupture stress required for dividing the cell after a compressive stress is applied, and substituting the tension rupture stress into Rumpf's equation, Ft=St×Dt2×ε/(1−ε), where St (nN/μm) is the tension rupture stress measured by applying a predetermined compressive stress to the toner, and ε is a toner-layer gap ratio.

A method of manufacturing a toner for electrophotography that is used in an image formation in which a toner image is formed by supplying a toner to a latent image formed on an image carrier, and the toner image is transferred onto a recording medium by using a transfer unit including an intermediate transfer member that on which the toner image is transferred from the image carrier, wherein

• the toner for electrophotography satisfies
• Ft/Dt≦3.0 [nN/μm]
• where Ft is an inter-toner non-electrostatic adhesion force after a compressive stress within 0.7×10−2 [N/m2] to 1.5×10−2 [N/m2] is applied, and Dt is a toner particle diameter,
• the inter-toner non-electrostatic adhesion force is obtained by filling a two-dividable cell for an Agrobot manufactured by Hosokawa Micron Corporation having a diameter of 15 millimeters, measuring a tension rupture stress required for dividing the cell after a compressive stress is applied, and substituting the tension rupture stress into Rumpf's equation, Ft=St×Dt2×ε/(1−ε), where St [nN/μm] is the tension rupture stress measured by applying a predetermined compressive stress to the toner, and ε is a toner-layer gap ratio,
• the toner for electrophotography comprises
• a first toner manufactured so that an average value of the circularity is larger than a predetermined value, and
• a second toner manufactured so that an average value of the circularity is smaller than the predetermined value, and
• the toner for electrophotography is manufactured by mixing the first toner and the second toner in a container at a time of shipping.