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AssigneeMita Industrial Co., Ltd.
InventorsToshihiro Kouchi, Hiroshi Takayama, Tatsuo Aizawa
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In a one-component type developer for electrophotography consisting essentially of a dry blend of fixing magneto-sensitive particles and flowability- and electric resistance-controlling fine particles, when an aromatic vinyl resin and/or an acrylic resin is used as a binder resin for the magneto-sensitive particles in combination with a low molecular weight olefin resin, the magneto-sensitive particles are much improved in the property of holding the flowability- and electric resistance-controlling fine particles on the surfaces thereof. Accordingly, these fine particles cannot be substantially separated from the magneto-sensitive particles under agitation conditions, development conditions and fixing conditions. As a result, contamination of the interior of a copying machine, especially an optical system, can be completely prevented, and also contamination of the background can be completely prevented. Further, the resulting fixed images have a very high resistance to friction and abrasion, and troubles such as blurring and flow of the image are not caused at all.
A developer for electrophotography consisting essentially of a dry blend of fixing magneto-sensitive particles having a particle size of 5 to 50.mu. and flowability and electric resistance-controlling fine particles having particle size of up to 1 micron in an amount of 0.001 to 2 parts by weight per 100 parts by weight of said fixing magneto-sensitive particles, wherein said fixing magneto-sensitive particles are obtained by kneading a composition comprising (A) Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3, (B) carbon black, (C) a binder resin composed mainly of at least one resin selected from the group consisting of aromatic vinyl resins and acrylic resins and (D) a low-molecular-weight olefin resin at an (A):(B):(C):(D) mixing weight ratio of (20-80):(0.5-20):(18-40):(0.5-30), cooling the kneaded composition and pulverizing the cooled composition and said flowability-and electric resistance-controlling fine particles are adhering to and held on the surfaces of said fixing magneto-sensitive particles substantially inseparably therefrom wherein said binder resin (C) is present in the fixing magneto-sensitive particles in the form of a continuous phase and said low-molecular-weight olefin resin (D) is present in the fixing magneto-sensitive particles in the form of a dispersed phase together with Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3 (A) and carbon black (B).
A developer for electrophotography consisting essentially of a dry blend of fixing magneto-sensitive particles having a particle size of 5 to 50.mu. and fine carbon black particles having a particle size of up to 1.mu. in an amount of 0.001 to 2 parts by weight per 100 parts by weight of said fixing magneto-sensitive particles, wherein said fixing magneto-sensitive particles are obtained by kneading a composition comprising (A) Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3, (B) carbon black, (C) a binder resin composed mainly of at least one resin selected from the group consisting of aromatic vinyl resins and acrylic resins and (D) an olefin resin having a weight average molecular weight of 1,000 to 10,000 and a softening point of 80.degree. to 160.degree. C. at an (A):(B):(C):(D) mixing weight ratio of (20-80):(0.5-20):(18-40):(0.5-30), cooling the kneaded composition and pulverizing the cooled composition and said fine particles are adhering to and held on the surfaces of said fixing magneto-sensitive particles substantially inseparably therefrom wherein said binder resin (C) is present in the fixing magneto-sensitive particles in the form of a continuous phase and said low-molecular-weight olefin resin (D) is present in the fixing magneto-sensitive particles in the form of a dispersed phase together with Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3 (A) and carbon black (B).
A carrierless developer for electrophotography consisting essentially of a dry blend of fixing magneto-sensitive particles having a particle size of 5 to 50 microns and flowability-and electric resistance-controlling fine particles having a particle size of up to 1 micron adhered to and held on the surface of said fixing magneto-sensitive particles substantially inseparably therefrom, but without being embedded in said fixing magneto-sensitive particles, the amount of said fine particles being from about 0.001 to 2 parts by weight per 100 parts by weight of said fixing magneto-sensitive particles, said fixing magneto-sensitive particles comprising (A) Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3, (B) carbon black, (C) a binder resin composed mainly of at least one resin selected from the group consisting of aromatic vinyl resins and acrylic resin and (D) a low-molecular-weight olefin resin at an (A):(B):(C):(D) mixing weight ratio of (20-80):(0.5-20):(18-40):(0.5-30), wherein said binder resin (C) is present in the fixing magneto-sensitive particles in the form of a continuous phase and said low-molecular-weight olefin resin (D) is present in the fixing magneto-sensitive particles in the form of a dispersed phase together with Fe.sub.3 O.sub.4 or .gamma.-Fe.sub.2 O.sub.3 (A) and carbon black (B).
Dependencies are inferred from the claim text.