JPH01123250A - Carrier - Google Patents

Abstract

PURPOSE:To obtain a dispersion type carrier which has less dependency of electrostatic chargeability on environment by incorporating magnetic power which is subjected to a surface treatment by a positive chargeable inorg. material into the magnetic powder dispersion type carrier essentially consisting of a resin and the magnetic powder. CONSTITUTION:The charge control of the carrier for a developer of a magnetic powder dispersion type is executed by using the magnetic powder which is subjected to the surface treatment by the positive chargeable inorg. material. Since the charge control is executed by using the magnetic powder which is the main component of the dispersion type carrier, the control is easier than with the conventional carrier which controls the charge characteristic from the binder resin side by adding additives, etc., to the carrier. In addition, the environmental characteristic of the chargeability is low and the carrier is usable as a long-life carrier. The inorg. materials to impart the positive chargeability to the carrier by the surface treatment are exemplified by magnesium oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium carbide, zirconium hydroxide, calcium tungstate, cobalt carbonate, zirconium hydroxide, magnesium carbide, magnesium hydroxide, etc.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a two-component developer for developing electrostatic latent images or magnetic latent images in electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to a carrier as a constituent component, and more specifically to a magnetically dispersed carrier.

[Prior Art] In electrophotography, a photoconductive substance such as selenium is used as a photoreceptor, an electrical latent image is formed by various means, and this latent image is developed using a magnetic brush development method or the like. A method of attaching toner and visualizing it is generally adopted.

In this development process, carrier particles called carriers are used to impart an appropriate amount of positive or negative electricity to the toner. Various types of carriers have been developed and put into practical use.

[Problems to be solved by the invention] There are various properties required of the carrier, but particularly important properties include appropriate charging properties, impact resistance, abrasion resistance, developability, and developer life. be able to.

Considering the above-mentioned required characteristics, carriers that have been used in the past still have problems to be improved, and no carrier that fully satisfies them is known.

For example, conductive carriers such as iron oxide powder have excellent solid developability, but are poor in fine line reproducibility, and also require the toner to contain a special charge control agent to extend its life. On the other hand, coat-based insulating carriers have the disadvantage of poor solid reproducibility, although they are excellent in longevity and fine wire reproducibility.

In order to improve these drawbacks, a small particle carrier in which magnetic fine particles are dispersed in a binder resin, a so-called carrier for microtoning, has been proposed and put into practical use, but due to the small particle size, the carrier is photosensitive. It has the disadvantage of adhering to the body. This phenomenon can be prevented by increasing the particle size of the carrier, but increasing the particle size of the carrier lowers the charging property, resulting in problems such as fogging and contamination inside the machine.

Charge control of the dispersed carrier is usually done by adding an acid value to the binder resin, copolymerizing it with a nitrogen-containing polymer, or adding nigrosine, a quaternary ammonium salt, which is usually used in toners, when mixing it with magnetic powder. Generally, this is carried out by using a charge control agent such as chromium dye or chromium dye, and charge control using magnetic powder, which accounts for the majority of the quantity fraction, is not necessarily carried out actively.

Therefore, an object of the present invention is to provide a novel magnetic powder-dispersed carrier whose charging is controlled by the polarity of the magnetic powder.

Another object of the present invention is to provide a dispersed carrier that exhibits stable positive chargeability and has a long life.

Furthermore, another object of the present invention is to provide a dispersed Kireliya whose chargeability is less dependent on the environment.

[Means for Solving the Problems] The present invention is a magnetic powder-dispersed carrier containing a resin and magnetic powder as essential components, which is characterized in that it contains magnetic powder whose surface has been treated with a positively charged inorganic substance. be.

As the binder resin in the carrier of the present invention, in addition to polyolefin compounds such as ethylene, propylene, butylene, and isobutylene, resins such as those described below, either singly or copolymerized, can be used.

Namely, styrenes such as styrene, chlorostyrene, and vinylstyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, and acrylic acid. Esters of α-methylene aliphatic monocarboxylic acids such as ethyl, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate;
Examples include vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl butyl ether; homopolymers and copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone; As the adhesive resin,
Mention may be made of polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, polypropylene. can.

Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and waxes.

The magnetic powder used after surface treatment with a positively charged inorganic substance in Kireliya of the present invention is a normal ferromagnetic fine powder, and specifically, triiron tetroxide, γ-iron sesquioxide, various ferrite powders, chromium oxide, Also, various metal fine powders such as iron, nickel, and stainless steel are used.

Inorganic substances that impart positive chargeability through surface treatment of magnetic powder include magnesium oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium carbonate, calcium oxide, calcium tungstate, cobalt carbonate, zirconium hydroxide, calcium tungstate, and carbonate. Examples include cobalt, zirconium hydroxide, magnesium carbonate, magnesium hydroxide, etc., as long as it is an inorganic salt that exhibits a precipitate formation reaction, an inorganic substance that can be made into finer particles than magnetic powder, and that exhibits positive chargeability by itself. Can be used as surface treatment material and binding.

Inorganic treatment of magnetic powder can be carried out by causing a precipitation reaction of inorganic substances in the presence of magnetic powder dispersed in a medium such as water, depositing the inorganic substance on the surface of the magnetic powder, drying, and then firing. There is a method in which a tri-blend of magnetic powder and inorganic fine powder is adhered to the surface.

Surface-treated magnetic powder can be contained in a carrier in a larger amount than untreated magnetic powder, and charging can be controlled more advantageously than control from the binder resin side.

The appropriate content of the magnetic powder is about 30 to 95 parts by weight, preferably 45 to 90 parts by weight, and more preferably 65 to 85 parts by weight, based on the entire carrier. The method for producing the dispersed carrier of the present invention includes a kneading and pulverizing method in which treated magnetic powder and resin are melt-kneaded and then pulverized, or a granulation method in which a heated molten slurry of the mixture is sprayed and cooled using a spray-drying type atomizer. used.

The average particle size of the carrier is 20-400μ, preferably 30μ
~200μ is appropriate.

Furthermore, the treated magnetic powder can be reprocessed with various coupling agents to improve its dispersibility, a charge control agent can be added to the resin, and the treated magnetic powder can be mixed with untreated magnetic powder. It is also effective to use it in order to control charging properties.

[Example] Tomojin magnetic powder (manufactured by Toda Kogyo Co., Ltd., EPTioooo) was dispersed in water, the pH was adjusted to 2.0 with sulfuric acid while heating to 60°C, and a sodium aluminate aqueous solution was gradually added while stirring. In addition, after the addition was completed, it was filtered and heated and fired to obtain alumina surface-treated magnetic powder.

This magnetic powder and the magnetic powder without surface treatment were kneaded in a Banbury mixer in the composition shown in the table below, and then finely pulverized to obtain carriers A and B with an average particle size of 70 microns.

The carriers A, B and a toner made by adding 5% by weight of carbon black (Cabot L BPL) to polyester and kneading and pulverizing to an average of 11 μm were mixed in a V-type blender to form a developer. A', B'
shall be. ).

The initial charge amount of the toner of sample A' is -20 μC/g,
That of toner B' was 12 μC/g. Continuous copying tests were conducted using these developers using a modified FX5990 machine.
The image quality decreased to μC/g, and a decrease in mW and fogging occurred after 20,000 sheets were printed, but the image quality of sample A' toner remained clear even after 100,000 sheets, and no fogging occurred. The amount of charge is -1
It was maintained at 7μc/li.

X Nagi PJ 2 Magnetic powder (manufactured by Titan Kogyo Co., Ltd., BLSP) is mixed with titanium oxide fine powder (average particle size 30 mμ) at a ratio of 20:1 by weight, and dispersed with a Henschel mixer to coat the titanium oxide fine particles on the surface of the magnetic powder. It was attached to.

This magnetic powder and the magnetic powder without surface treatment were heated and melted to form a slurry in the composition shown in the table below, and the slurry was granulated and cooled in a spray dryer to obtain a carrier C1D having an average particle diameter of 100 μm.

This carrier and the toner of Example 1 were mixed to form a developer C'.
, D' was created and a continuous copy test was conducted using a modified FX5990 machine. The initial charge amount of the toner was -25 μG/9 for developer C' and -17 μC/g for developer D'.

The toner of developer a' has a charge amount of 14 μC/g at 40,000 sheets.
A decrease in the degree of development and fogging were observed. However, even after 150,000 sheets were printed, the toner of developer C' maintained a charge amount of -20 μC/g, and no problem in image quality occurred.

[Effects of the Invention] The present invention controls the charge of a magnetic powder-dispersed developer carrier by using magnetic powder whose surface is treated with a positively chargeable inorganic substance. Since charging is controlled using a certain magnetic powder, it is easier to control than conventional carriers that control charging characteristics from the binder resin side by adding additives, etc., has less environmental impact on charging, and has a long life. Can be used as a carrier.

Patent applicant: Fuji Xerox Co., Ltd. Agent Patent Attorney Hisashi Oya

Claims (1)

[Claims] A magnetic powder-dispersed carrier comprising resin and magnetic powder as essential components, characterized in that it contains magnetic powder whose surface has been treated with a positively charged inorganic substance.