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Resin coated carriers for electrostatic image development and the method of preparing the same
| Details |
Inventors: Koizumi, Yoshiaki; Tsujita, Kenji; Kouno, Shigenori; Ohmura, Ken;
Assignee: Konica Corporation (Tokyo, JP)
Primary Examiner: Martin; Roland
Assistant Examiner:
Attorney, Agent or Firm: Bierman; Jordan B.
The invention relates to a carrier and method of making a carrier in which elementary resin particles of volume average particle size not more than 0.5 m are fused on their surfaces to form secondary particles of BET surface areas of 5 to 150 m/g and volume average particle size of 1.5 to 5.0 m, which secondary particles are coated by a dry method on core particles to form carrier particles. |
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DETAILED DESCRIPTION OF THE INVENTION BET specific surface area is measured with, for example, a micromeritics flow sorb (Type II2300; manufactured by Shimazu Corporation).
Volume average particle size is measured by means of, for example, a laser diffraction type size distribution measuring machine (HEROS; sold by Japan Electronics Corporation).
Dispersion of secondary resin particles is performed over a period of two minutes by means of a ultrasonic homogenizer with an output power of 150 W after resin particles, a surfactant and water (disperse system) are put in a beaker of 50 cc capacity.
The BET specific surface areas of the secondary resin particles are satisfactory when it is in the range of 5 to 150 m.
sup.
2 /g.
Since impacting power to be applied on the secondary resin particles during dry coating depends on the particle sizes of core particles, larger BET specific surface areas of the secondary particles are preferable when the sizes of core particles are small.
If the BET specific surface areas of the secondary resin particles are large, sufficient spreadability to core particles can be obtained with minimum impacting power, and as a result, a film of excellent property can be obtained.
Meanwhile, a simple, elementary resin particle with a particle size of about 2 .
mu.
m has a BET specific surface area of smaller than 5 m.
sup.
2 /g.
If the BET specific surface area of a secondary resin particle is smaller than 5 m.
sup.
2 /g, its spreadability to the surface of a core carrier particle is poor, making it difficult to obtain a coating layer of uniform thickness.
In this case, secondary resin particles tend to agglomerate to form white powder, and such white powder may stick to the surface of a resin-coated carrier electrostatically, causing insufficient development.
In addition, since a considerable amount of secondary resin particles are present in a free state without forming a layer on the surface of a core particle, there may be a substantial lowering of resin coating efficiency
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Optical Systems 
