Electrophotography – Image formation – Development
Reexamination Certificate
2007-09-18
2007-09-18
Gray, David M. (Department: 2852)
Electrophotography
Image formation
Development
C430S111350
Reexamination Certificate
active
11528609
ABSTRACT:
A carrier including a magnetic core material and a layer located on a surface of the magnetic core material, wherein the carrier satisfies the following relationships (1) to (3): 0.90≦(σa/σb)<1.00 (1); 200≦(σb·ρc)≦400 (2); 10≦(σb/ρc)≦20 (3), wherein σb represents a magnetization of the carrier at 1,000 Oe, σa represents a magnetization of the carrier after frictionized with a cylindrical sleeve under a specific condition and ρc represents a true specific gravity of the carrier, wherein the carrier has a weight-average particle diameter of about 25 to about 65 μm and includes carrier particles having a weight-average particle diameter not greater than about 12 μm in an amount of not greater than about 0.3% by weight, wherein a ratio between the weight-average particle diameter and a number-average particle diameter of the carrier is about 1 to about 1.3, and wherein an electric resistance is from about 1.0×109to about 1.0×1011Ω·cm when an AC voltage represented by the following formula (4) is applied at a frequency of 1,000 Hz to a magnetic brush of the carrier is formed between parallel plate electrodes having a gap of d mm such that magnetic brush has a space occupancy of 40%: E(V)=250×d (4), wherein d is 0.40±0.05 mm and E is a peak voltage.
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Kondou Tomio
Mochizuki Satoshi
Suzuki Kohsuke
Yamashita Masahide
Gray David M.
Ready Bryan
Ricoh & Company, Ltd.
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