JPS62164052A - Manufacture of electrophotographic developing carrier - Google Patents

Abstract

PURPOSE:To obtain a sharp color image without peeling and dropping out of a magnetic material during use by kneading a resin and the magnetic material, pulverizing them, and then, heating them to the glass transition point of the resin or above it to swell and fix the mixture of the resin and the magnetic material to each other. CONSTITUTION:The developer is prepared by kneading 20-40pts.wt. of the resin and 80-60pts.wt. of the magnetic material, pulverizing them, then, heating them to the glass transition point of the resin or above it so as to swell the resin and to fix the magnetic material present on the surface of each mixture particle surrounded with the swollen resin, thus permitting the magnetic material to be strongly fixed and prevented from peeling and dropping off, and sharp color reproduction to be ensured even in the case of using color tuners such as red, blue, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a carrier for electrophotographic development used in electrophotographic copying machines, facsimile machines, laser beam printers, and the like.

BACKGROUND ART Conventionally, carriers for electrophotographic development (hereinafter simply referred to as carriers) containing resins and magnetic materials have been obtained by mixing and kneading materials and then pulverizing the product.

Specifically, 1) Materials such as resin, magnetic material, and charge control agent are dry mixed using a mixer such as a V-type mixer.

11) Knead the mixed materials using a kneader such as a Banbury mixer.

111) The kneaded product is cooled and coarsely pulverized, and then finely pulverized using a pulverizer such as a jet mill.

iv) Next, use a classifier to classify the particles as necessary to obtain the desired particle size distribution.

He had made a career through the process.

Problems to be Solved by the Invention However, since the carrier obtained as described above exists with part of the fine magnetic material exposed on the surface of the carrier, a dry two-component developer in which the carrier and toner are mixed is used. When used as a developer (hereinafter simply referred to as a developer), a part of the magnetic material exposed on the carrier surface may peel off or be lost due to collisions between carriers or carriers and toner due to stirring or mixing, friction, etc. It will be mixed in. Normally, this magnetic material has a black color, so if black toner is used, there is no problem with the color itself even if it is mixed, but since the finished copy is developed and transferred, it has the disadvantage that the image surface becomes rough. . In addition, when using color toners such as red and blue, missing magnetic substances may adhere to the toner surface or be developed and transferred together with the toner, making it difficult to reproduce clear colors and resulting in muddy colors. It had the disadvantage that only images could be obtained.

In view of the above-mentioned problems, the present invention provides a method for producing a carrier for electrophotographic development, which prevents the magnetic material contained therein from being lost and enables clear color reproduction even when using color toners such as red and blue. It is something to do.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for producing an electrophotographic developing carrier of the present invention comprises at least a resin and a magnetic material, the resin being 20 to 40% by weight, the magnetic material being 20 to 40% by weight. 60～
After kneading and pulverizing the resin by weight, the resin is heated to a temperature higher than the glass transition point of the resin to swell the resin and fix the magnetic material present on the surface.

Effects According to the present invention, the magnetic material present on the surface is enveloped by the swelling of the resin by the above-described manufacturing method, so that the magnetic material is firmly fixed and can be prevented from peeling or chipping.

EXAMPLES A method for producing a carrier for electrophotographic development according to the present invention will be described below.

In the present invention, the resin and the magnetic material are kneaded using a lamixer or the like, then pulverized, and finally classified into the required particle size using a classifier.

Thereafter, the carrier is further heated to a temperature higher than the glass transition temperature of the resin, and the magnetic material adhering to the surface of the carrier in a protruding state is wrapped in the swollen resin and firmly fixed.

Several examples will be described below.

(Example 1) 26 parts by weight of styrene-acrylic copolymer resin, 75 parts by weight of ferrite, and 1 part by weight of chargeability modifier nigrosine are mixed in a Henschel mixer and kneaded in a Banbury mixer. After that, it is coarsely ground and then finely ground using a jet mill. Furthermore, the particles were classified to a desired average particle size of 6oμ using an air classifier.

The product thus obtained was heated in a heating furnace at 120°C to 140°C.
The magnetic material present on the surface is wrapped in a swollen resin by heat treatment with C. A carrier was obtained through this process.

When 96 parts by weight of this carrier and 5 parts by weight of red toner were mixed and used in a Matsushita electrophotographic copying machine [FP-1300J, a clear red image without turbidity was obtained.

(Example 2) 16 parts by weight of polyester resin, 6-type amine resin mold, and 80 parts by weight of ferrite are mixed in a Henschel mixer and kneaded in a Banbury mixer. After that, it is coarsely ground and then finely ground using a jet mill. Furthermore, the particles were classified to a desired average particle size of 60 μm using an air classifier. The product thus obtained is heat-treated in a heating furnace at 80° C. to ioo° C., and the magnetic material present on the surface is fixed in a state where it is surrounded by the swollen resin. A carrier was obtained through such process treatment.

When 96 parts by weight of this carrier and 6 parts by weight of red toner were mixed and used in a Matsushita electrophotographic copying machine "FP-13oo J," a clear red image without turbidity was obtained.

(Example 3) 26 parts by weight of styrene resin, 16 parts by weight of butyl acrylate resin
60 parts by weight, Ferrai) and 1 part by weight of nigrosine were mixed in a Henschel mixer and kneaded in a Banbury mixer. After that, it is coarsely ground and then finely ground using a jet mill.

Furthermore, the particles were classified to a desired average particle size of 50 μm using an air classifier.

The product thus obtained was heated in a heating oven at 120"C to 14"C.
Heat treatment is performed at 0°C, and the magnetic material present on the surface is fixed in a state where the swollen resin is wrapped. A carrier was obtained through such process treatment.

When 96 parts by weight of this carrier and 6 parts by weight of red toner were mixed and used in an electrophotographic copying machine manufactured by Matsushita rFP-1300, a clear red image with no turbidity was obtained.

Effects of the Invention As detailed above, according to the present invention, since the magnetic material present on the surface is fixed in a state where the resin swells and wraps it, there is no possibility that the magnetic material will peel off or fall off during use. Even when color toner e is used, clear color images without turbidity can be obtained. Also, development of magnetic materials,
Since transfer can be prevented, the image surface of the completed copy will be improved.

Claims (1)

[Claims] It consists of at least a resin and a magnetic material, and the resin is
After kneading and pulverizing 40% by weight and 60 to 80% by weight of the magnetic material, the resin is heated to a temperature higher than the glass transition temperature of the resin to swell the resin and fix the magnetic material present on the surface. A method for producing a carrier for electrophotographic development, characterized in that: