Abstract: An electrostatic image developer includes a toner containing an external additive having a volume-average particle size of about 80 to 400 nm and an average circularity of about 0.7 to 0.85. The developer is used in an image forming apparatus including an image-carrying member having a top surface layer containing fluorocarbon resin particles, and a developer-carrying member that faces the image-carrying member and carries an electrostatic image developer, in which a value obtained by dividing the amount of developer on the developer-carrying member [g/m2] by a shortest distance between the image-carrying member and the developer-carrying member [?m] is about 0.8 to 1.8, and a peripheral velocity ratio of the developer-carrying member to the image-carrying member is about 1.5 to 5.0 or the developer-carrying member moves in a direction opposite to the image-carrying member in a facing portion.

Abstract: An image forming apparatus having: an image forming body for forming a latent image and a toner image; a developing device for developing with a toner the latent image formed on the image forming body to form the toner image; a primary transfer device for transferring the toner image on the image forming body onto an intermediate transfer body; and a secondary transfer device for transferring the toner image on the intermediate transfer body onto an image support. The primary transfer device has conductive body or semi-conductive body, and is provided with a power supply unit for applying a bias voltage. It is characterized in that the variation coefficient of the shape factor of the toner is 16% or less, and the number variation coefficient of the number particle size distribution of the toner is 27% or less.

Abstract: Solid and highlight developed image patches are formed, and their densities are measured with a development density sensor and stored into a control case memory as data constituting a control case. Two additional control cases are similarly stored into the control case memory while a scorotron set value and a laser set value are varied. Receiving these control cases through a status quantity comparator and a cluster memory, a control rule calculation unit determines a control rule. By properly combining the control rules, new operation quantities, i.e., a scorotron set value and a laser set value, are determined.