Kao Corporation

Norihiro Hayashi

Kuniyasu Kawabe

Shinichiro Yasuda

Masayoshi Nawa

Hiroyoshi Hiramatsu

Eiji Morimoto

The present invention is directed to a toner composition containing a polyester resin having an OHV/AV value of 1.2 or more as a major component of a binder resin wherein AV is an acid value of said polyester and OHV is a hydroxyl value thereof and hydrophobic silica having a degree of hydrophobic property of 80 or more or having a pH value of 5.5 to 8 in water-methanol solution. A toner composition of the present invention exhibits no decrease in electric charge retainability and fluidity of a toner and a visible image with good quality for a long period with no black spots occurring.

Toner composition

The present invention is directed to a toner composition containing a polyester resin as a major component of a binder resin and 0.01 to 1.5 parts by weight of hydrophobic silica having a degree of hydrophobic property of not less than 80, and/or having a pH value of 5.5 to 8 when 4% by weight of hydrophobic silica is dispersed in water-methanol solution (1:1) to 100 parts by weight of the toner.

Hydrophobic polyester toner composition

A novel resin is produced by the step of polymerizing (a) styrene and/or a derivative thereof, (b) a monomer component selected, alone or in combination of two or more, from the group consisting of methacrylic acid, acrylic acid, a methacrylic ester and an acrylic ester, and (c) 0.05 to 10 percent by weight, based on the total weight of the monomers, of a polybasic acid having 7 to 40 carbon atoms, an anhydride thereof or a lower (C1 to C6) alkyl ester thereof, the monomer component (b) containing at least one acrylic or methacrylic ester having hydroxyl or epoxy group in at least equimolar amount to the component (c) and has a softening point of 100.degree. to 160.degree. C. and a glass transition temperature of 50.degree. C. or higher. It is useful as a binder resin for a toner composition.

Resin binder for toner composition

An electrophotographic developer composition comprises a binder resin, which comprises a polyester as the major component, said polyester obtained by co-condensation polymerization of

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Wakayama, Japan

Norihiro Hayashi