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AssigneeImex Co., Ltd.
InventorsShigetoshi Asano, Shuzo Nakayama, Masashi Ueda, Katsutoshi Saito, Kazuma Okamura
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A toner for developing electrostatic images which is obtained by melt mixing at least a binder resin and a coloring agent, forming a powder material by pulverizing the obtained mixture after cooling and removing rough particles and fine particles from the formed powder material by classification, wherein inorganic fine particles having a roundness of 1.00 to 1.30, an average of the diameter of primary particles of 0.05 to 0.45 μm and a ratio of a standard deviation to the average of the diameter of primary particles of 0.25 or smaller are added as an external additive, and a process for producing a toner for developing electrostatic images which comprises melt mixing at least a binder resin and a coloring agent, forming a powder material by pulverizing the obtained mixture after cooling, rounding the powder material by a heat treatment and adding the above inorganic fine particles to the rounded powder material. By using the toner, printed images of a high quality can be formed with an excellent transfer rate, suppressed contamination of the charge roller, minimal background and small consumption of the toner.
A toner for developing electrostatic images which is obtained by melt mixing a binder resin and a coloring agent to obtain a mixture, pulverizing the mixture after cooling to obtain a powder material, treating the powder material by heating under a floating condition to obtain rounded particles and removing rough particles and fine particles from the rounded particles by classification to obtain mother particles of the toner having an average circularity of 0.930 to 0.980, wherein inorganic fine particles having a roundness of 1.00 to 1.30, an average of diameter of primary particles of 0.05 to 0.45 μm and a ratio of a standard deviation to the average of diameter of primary particles of 0.25 or smaller are added to the mother particles of the toner as an external additive, wherein said inorganic fine particles are particles of barium titanate produced in accordance with an alkoxide process, and wherein an average circularity of the mother particles is determined with respect to particles having a diameter corresponding to the diameter of a circle of 3 μm or greater by using a flow type analyzer of particle images in accordance with the following equation:
A process for producing a toner for developing electrostatic images which comprises melt mixing a binder resin and a coloring agent to obtain a mixture, pulverizing the mixture after cooling to obtain a powder material, treating the obtained powder material by heating under a floating condition to obtain rounded particles and removing rough particles and fine particles from the obtained rounded particles by classification to obtain mother particles of the toner having an average circularity of 0.930 to 0.980, and adding to the mother particles of the toner inorganic fine particles having a roundness of 1.00 to 1.30, an average of diameter of primary particles of 0.05 to 0.45 μm and a ratio of a standard deviation to the average of diameter of primary particles of 0.25 or smaller, wherein said inorganic fine particles are particles of barium titanate produced in accordance with an alkoxide process, and wherein an average circularity of the mother particles is determined with respect to particles having a diameter corresponding to the diameter of a circle of 3 μm or greater by using a flow type analyzer of particle images in accordance with the following equation:
Dependencies are inferred from the claim text.