Electrophotographing dry-type toner and production method therefor

#The present invention relates to a dry toner for electrophotography, and its production process as well.

#A dry toner is usually produced by dispersing various agents such as releasing, coloring and charge control agents in a binder resin, grinding the resultant dispersion to toner size by fine grinding means, and classifying the powders into toner particles. Depending on the development system used, the dry toner is broken down into a one-component toner and a two-component toner comprising toner particles and carrier particles. A composite type toner is also known, in which the toner is coated thereon with a resin particle layer for the purposes of improving heat resistance, etc.

#In recent years, faster operations and lower-temperature fixation than ever before have been required for electrophotography. To meet such demands, there are interal dispersion type oilless fixing toner particles wherein releasing agent particles are dispersed in a binder resin. However, it is required to prevent offsets such as particle deposition onto a fixing roller because of a decrease in the internal cohesive force upon melting of the binder resin. There is still no choice but to increase the content of the releasing agent. However, the incorporation of more releasing agent than required leads to a drop of the transparency of color toner.

#A single drawing is a photograph illustrative of the particle structure in section of the dry toner for electrophotography prepared in Example 1 of the present invention.

#In the dry toners for electro photography according to the present invention, the color resin particle comprises a binder resin, a releasing agent, a coloring agent, a charge control agent, etc. For the binder resin, it is possible to make use of binder materials which are known so far for toners and capable of fixing toners. Preferably but not exclusively, the hinder resins used herein include styrene resins or homopolymers or copolymers containing styrene or substituted styrene such as polystyrene, poly-amethylstyrene, chloropolystyrene, styrene-chlorostyrene copolymers, styrene-propylene copolymers, styrene-butadiene copolymers, styrene-vinyl chloride copolymers, styrene-vinyl acetate copolymers, styrene-maleic acid copolymers, styrene-acrylate copolymers, styrene-methacrylate copolymers, styrene-acrylate-methacrylate copolymers, styrene-α-methyl chloroacrylate copolymers and styrene-acrylonitrile-acrylate copolymers, polyester resins, epoxy resins, urethane-modified epoxy resins, silicone-modified epoxy resins, vinyl chloride resins, rosin-modified maleic acid resins, phenyl resins, polyethylene, polypropylene, ionomer resins, polyurethane resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins, polyvinyl butyral resins, terpene resins, phenol resins, and aliphatic or alicyclic hydrocarbon resins, which may be used singly or in admixture. For the present invention, it is especially preferable to make use of the styrene-acrylic ester resin, styrene-methacrylic ester resin and polyester resin.

#The binder resin used has a glass transition temperature of 50° C. to 75° C. and a flow softening point of 100° C. to 150° C. To prepare a low-temperature fixable toner, it is preferable to use a binder resin having a glass transition temperature of 50° C. to 65° C. and a flow softening point of 100° C. to 120° C., and to prepare an oilless fixing toner, it is preferable to use a binder resin having a melt viscosity of 1×103 to 1×107 Pa·s at a 50% flow point in view of the agglomeration of the binder resin upon thermal fusion.

#For the coloring agent, various organic or inorganic pigments and dyes of various colors may be used as referred to below. Exemplary black pigments are carbon black, copper oxide, triiron tetraoxide, manganese dioxide, Aniline Black, and activated carbon. Exemplary yellow pigments are chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, Mineral Fast Yellow, nickel titanium yellow, Naval Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Parmanent Yellow NCG and Tartrazine Lake. Exemplary orange pigments are red chrome yellow, molybdenum orange, Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange RK, Benzidine Orange G and Indanthrene Brilliant Orange GKM. Exemplary red pigments are red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, Permanent Red 4R, Lithol Red, Pyrazolone Red, watchung Red, calcium salt, Lake Red D, Brilliant Carmine 6B, eosine lake, Rhodamine Lake B, Alizarine Lake and Brilliant Carmine 3B. Exemplary violet pigments are manganese violet, Fast Violet B and Methyl Violet Lake. Exemplary blue pigments are Prussian blue, cobalt blue, alkali blue lake, Victoria Blue Lake, Phthalocyanine Blue, metal-free Phthalocyanine Blue, a partially chlorinated pigment of Phthalocyanine Blue, Fast Sky Blue and Indanthrene Blue BG. Exemplary green pigments are chrome green, chromium oxide, Pigment Green B, Malachite Green Lake and Final Yellow Green G. Exemplary white pigments are zinc white, titanium oxide, antimony white and zinc sulfide. Exemplary extender pigments are barite powders, barium carbonate, clay, silica, white carbon, talc and alumina white. Various dyes such as basic, acidic, disperse and direct dyes, for instance, include Nigrosine, Methylene Blue, Rose Bengale, Quinoline Yellow and Ultramarine Blue.