Abstract: A carrier for use in development of an electrostatic latent image and an image forming apparatus using the carrier, with which a stable charging ability is maintained for a long period of time, and a high density image free from fog can be formed. The carrier has magnetic material particles coated with a coating resin. The coating resin is a thermoplastic resin, with a hardness of rank F to B in the terms of the pencil scratch test, and is present in an amount of 0.5 to 5 parts by weight to 100 parts by weight of the magnetic material particles.

Abstract: A method and an apparatus for measuring the toner concentration and the amount of electric charge, capable of simultaneously measuring the toner concentration and the amount of electric charge easily and maintaining high precision using a simple device.

Abstract: A magnetic carrier for electrophotographic developing agent wherein the surfaces of the magnetic core particles are partly coated with a thermosetting resin and a small amount of a low-melting or low-softening thermoplastic resin or wax, and at least recessed portions of the core particles are filled with these coating materials. The magnetic carrier has an electric resistance that is maintained within a range that is suited for forming the image, and suppresses the occurrence of spent toner.

Abstract: An electrophotographic developer includes a toner and a carrier, in which the carrier is provided on the surface of a core material thereof with a resin coating layer. The coating layer is made of cured body of a methyl silicone resin containing not less than 70% by weight of T-units and a methylated melamine resin having a molecular weight of not less than 700. This developer is not lowered in flowability, generates no spent particles and presents stable electric charging characteristics. Accordingly, the developer of the present invention is suitably used where a toner is used containing no electric charge controlling agent.

Abstract: In accordance with the present invention, the electrophotographic toner is produced by dispersing and mixing toner components containing a fixing resin, a coloring agent and an electric charge controlling dye, and by melting and kneading the resulting mixture, which is then subjected to pulverizing and classifying. According to the present invention, fine powder generated at the pulverizing and classifying steps is reused as added to a mixture of toner components as already dispersed and mixed at the dispersing and mixing step, and the surface dye density of the electric charge controlling dye is in the range from 1.0.times.10.sup.-3 to 1.7.times.10.sup.-3 g/g, or the rate of the amount of an electric charge controlling dye present on the surfaces of toner particles to the total amount of the electric charge controlling dye, is in the range from 10 to 27% by weight.

Abstract: A magnetic carrier for a two-component type developing agent used for the electrophotography, comprising resin-magnetic spherical particles which are formed by the polymerization of a monomer in which a magnetic powder is dispersed and which have a glass transition temperature of higher than 100.degree. C., the surfaces of said resin-magnetic spherical particles being coated with a surface-treated coating layer. Therefore, the surface-treated coating layer on the surfaces of the carriers can be heat-treated at 100.degree. C. or higher. The carrier therefore is light in weight, flowable, and exhibits excellent durability, resistance against the heat and stable electric characteristics irrespective of the passage of time.

Abstract: A specific silicone oil having a vicinal epoxy group is coated on a carrier for a developing or incorporated in a coating resin layer of a carrier for a developer. In this carrier, the spending phenomenon is prevented, the moisture resistance and flowability are improved, and a stable friction chargeability can be maintained for a long time and the durability is highly improved.

Abstract: A resin-coated magnetic carrier for two-component developers which comprises magnetic particles and a resin coating formed on the individual magentic particles is described. The resin coating is made of a cured resin composition comprised of an alkylated melamine resin whose moelcular weight satisfies the followin inequalityM.gtoreq.1100C-400wherein M represents a weight average molecular weight of the resin and C represents the number of carbon atoms in the alkyl moiety, and an acryl-modified silicone resin. The use of the composition is effective in preventing the coated particles from melt adhesion and in forming a smooth and uniform coating layer on individual particles. The resin-coated carrier is significantly reduced in amount of spend carrier and has good durability, moisture resistance, chargeability.