Mita Industrial Co., Ltd.

Kazuhiko Yamamura

Takashi Teshima

Takatomo Fukumoto

Kyouya Taguchi

Hiroyuki Hazama

Koji Honda

Takeshi Higuchi

Disclosed are a two-component type developer which is supplied to an area where a bias voltage of at least 250 V is applied, and a developing process using this developer. In this developer, by adjusting the particle size distribution of carrier particles within a specific range, occurrence of the so-called carrier dragging phenomenon of the transfer of the carrier together with the toner to a photosensitive material can be prevented. This adjustment of the particle size distribution is such that the content of carrier particles having a size smaller than 250 mesh is less than 8% by weight based on the entire carrier particles, the diameter D.sub.50 of the weight average particle size corresponding to 50% of the weight of the entire carrier particles is in the range of from 80 to 120 .mu.m and the difference between D.sub.25 and D.sub.75 is in the range of from 5 to 20 .mu.m.

Magnetic brush developing process and developer

Disclosed is a two-component type developer comprising a toner and a coated magnetic carrier wherein said toner has an electroconductivity lower than 3.5.times.10.sup.-10 S/cm and the coating of said magnetic carrier consists of a silicone resin having as its component unit a basic nitrogen atom-containing organic group bonded to a silicone atom (N-containing silicone resin). Such developer is capable of forming images having a high image density and a high image quality, particularly as a white developer or a color developer if developing is carried out even under ordinary conditions, since the toner has its charge quantity maintained in an appropriate range in the developing step.

Magnetic carrier for electronic reproduction coated with a nitrogen

Disclosed is a carrier of a developer, which is characterized in that the current value observed when a direct current is applied under a voltage of 200 V is 0.8 to 2.0 .mu.A and the relaxation time is in the range of from 4.0 to 6.0 milliseconds, that is, the characteristic values in the dynamic state, for example, in a developing apparatus, are kept with certain ranges. If this developer carrier is used, an image having a high quality can be obtained without occurrence of troubles often caused in conventional developers, such as carrier dragging (transfer of the carrier to a photosensitive material together with the toner), fogging (transfer of the toner to the background of a copying sheet) and letter thinning.

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Higashiosaka, Japan

Kazuhiko Yamamura