JP2569495B2 - Carrier for electrophotographic developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a two-component developer for developing an electrostatic latent image or a magnetic latent image in electrophotography, electrostatic recording, electrostatic printing, and the like. The present invention relates to a carrier which is a constituent component, and more specifically, to a magnetic material dispersed type carrier.

[Conventional technology]

In electrophotography, a photoconductive substance such as selenium is used as a photoreceptor, an electric latent image is formed by various means, and toner is attached to the latent image using a magnetic brush development method or the like. A method of visualizing is generally adopted.

In this development step, 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 characteristics required for the carrier, but particularly important characteristics are appropriate chargeability, impact resistance, abrasion resistance,
Developability, developer life, and the like can be given.

In view of the above-mentioned required characteristics, the conventionally used carriers still have problems to be improved, and no satisfactory carrier has been known. For example, conductive carriers such as iron oxide powder are excellent in solid developability, but inferior in fine line developability, and require a special charge control agent to be included in the toner to extend the life. On the other hand, the coated insulating carrier is excellent in life and reproducibility of fine wires, but is inferior in solid reproducibility. For the purpose of remedying these drawbacks, a small particle size carrier in which magnetic fine particles are dispersed in a binder resin, a so-called microtoning carrier, has been proposed and put to practical use. There are inconveniences such as a change in the charge amount at high humidity and low humidity caused by the released magnetic particles, and the inability to drastically extend the life due to the difficulty in surface treatment.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a novel magnetic brush developing carrier used for developing an electrostatic latent image in electrophotography and electrostatic recording.

Another object of the present invention is to provide a magnetic brush which provides a toner with a high charge amount, has good surface contamination resistance, does not cause a decrease in charge amount during running, and has excellent developer life and high-speed developability. An object is to provide a carrier for development.

[Means for solving the problem]

The present inventors have conducted various studies and studies to improve the drawbacks of the conventional carrier, and as a result, it has been found that the use of a magnetic fine particle-dispersed carrier using a specific binder resin material has resulted in various required characteristics of the carrier. The inventors have found that the present invention is effective in improvement, and have completed the present invention.

That is, the present invention comprises polypropylene, polyethylene or a derivative thereof and polyvinylidene fluoride as essential components, and the blending ratio of polyvinylidene fluoride is 0.
An object of the present invention is to provide a carrier for an electrophotographic developer, wherein a magnetic powder is dispersed in a binder resin of 1 to 20% by weight.

Derivatives of polypropylene or polyethylene used in the binder resin of the present invention include polypropylene oxide and polyethylene oxide.

Further, as the polyvinylidene fluoride used in the carrier of the present invention, a homopolymer of vinylidene fluoride or vinylidene fluoride and ethylene, propylene, butylene, vinyl chloride, vinylidene chloride, trifluoroethylene, or other copolymerizable unsaturated A copolymer with a bond-containing monomer can be used.

For the binder resin for a carrier of the present invention, a thermoplastic resin generally used as a binder resin may be used within a range not to impair the object of the present invention (0 to 50% by weight in the binder resin). it can. Examples of such a resin include 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, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate,
Esters of α-methylene aliphatic monocarboxylic acids such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether;
Vinyl ethers such as vinyl ethyl ether and vinyl butyl ether; homopolymers and copolymers such as vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone; and particularly typical binder resins are Polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and styrene-maleic anhydride copolymer.

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

In the carrier of the present invention, as the magnetic fine particles to be dispersed in the binder resin, all commonly used ferromagnetic fine particles can be used. Specifically, triiron tetroxide, γ-iron sesquioxide , Various ferrite powders, chromium oxide,
Various metal powders and the like can be mentioned.

The proportion of each component constituting the carrier of the present invention is such that the content of polyvinylidene fluoride is 0.1 to 20% by weight in the binder resin.
And the content of magnetic particles is usually relative to the carrier.
About 30-95% by weight, desirably 45-90% by weight gives good results.

To the carrier of the present invention, a resin, a charge controlling agent, a coupling agent, a filler, other fine powder, and the like are added to the carrier of the present invention for the purpose of controlling charge, improving dispersion, reinforcing strength, improving fluidity, and other purposes. You can also.

The carrier particles of the present invention can be used as carrier particles as they are, but the surface can be subjected to surface treatment or coating treatment with a resin, a coupling agent, a surfactant, a charge control agent, a fine powder or the like.

The carrier of the present invention can be obtained by various methods, for example, a method of pulverizing and classifying a binder resin, a fluorine-containing compound, and magnetic fine particles kneaded by a heating and melting mixer such as a kneader or a Banbury, or spraying, cooling, and solidifying the kneaded material It is manufactured by a method such as

The average particle size of the carrier particles of the present invention is determined from the above-mentioned balance between the developer life, the photoconductor carrier adhesion and the image quality.
The thickness is suitably from 10 to 400 μm, more preferably from 30 to 200 μm.

The carrier of the present invention thus obtained is mixed with a toner and used as a magnetic brush developer for developing an electrostatic latent image.

As the toner, any chargeable toner commonly used in electrophotography, in which a colorant is dispersed in a binder resin, can be used, and is not particularly limited.

〔The invention's effect〕

The carrier for an electrophotographic developer of the present invention has a specific binder resin component, i.e., polypropylene, polyethylene or a derivative thereof and polyvinylidene fluoride as essential components, and the blending ratio of polyvinylidene fluoride is 0.1 to 20.
A magnetic powder is dispersed in a binder resin, which is a weight percent, and the chargeability of the carrier can be controlled by adjusting the blending amount of polyvinylidene fluoride, and the surface energy of the carrier is low. Therefore, the contamination of the carrier surface by the toner is suppressed, and the life of the carrier and thus the life of the developer can be extended.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited by these examples. In the following examples, parts represent parts by weight.

Example 1 Magnetite (EPT / 1000, manufactured by Toda Kogyo) 70 parts Polypropylene (Viscol 330P, manufactured by Sanyo Chemical) 27 parts Polyvinylidene fluoride (KYNAR, manufactured by PennWalt, USA) 3 parts are melt-kneaded with a pressure kneader, and furthermore, a turbo mill The mixture was pulverized and classified using a classifier to obtain a carrier having an average particle size of 60 μm.

Comparative Example Magnetite (EPT1000, manufactured by Toda Kogyo) 70 parts Polyester (hydrogenated bisphenol A, butanediol, fumaric acid polycondensate) 30 parts Kneaded folic acid in the same manner as in Example 1, classified and average particle size A carrier of 60μ was obtained.

Example 2 Using magnetite (EPT1000, manufactured by Toda Kogyo) 140 parts Polyethylene (400P, manufactured by Mitsui Petrochemical Co., Ltd.) 57 parts Polyvinylidene fluoride (KYNER, manufactured by PenWalt, USA) 3 parts, kneading and grinding in the same manner as in Example 1. Then, a carrier having an average particle size of 40 μm was obtained.

The carriers obtained in Examples 1 and 2 and Comparative Example were evaluated as developers (Developers 1, 2 and 3, respectively).
As a toner, a toner for FX-7770 copying machine (manufactured by Fuji Xerox Co., Ltd.) having an average particle size of 11 μm, made of styrene-acrylic resin and carbon black, was mixed with a carrier at a concentration of 3% by weight and mixed with a developer. did. For these developers, a life test was performed on a bench machine for evaluation at a photosensitive member speed of 350 mm / sec and a developing magnetic roll (sleeve) speed of 550 mm / sec. Initial charge amount is developer 1
Is 25 μc / g, 2 is 20 μc / g, and 3 is 18 μc / g, and the charge amounts after 100,000 copies are 23 μc / g, 16 μc / g, and 9 μc / g, respectively.
g

In addition, stains can be seen on the copy background portion of the developer 3.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasuo Matsumura 1600 Takematsu, Minami Ashigara-shi, Fuji Xerox Co., Ltd. JP-A-58-220146 (JP, A) JP-A-61-9661 (JP, A) JP-A-61-9609 (JP, A) JP-A-61-32860 (JP, A) JP-A-61-28959 (JP, A) JP-A-61-5255 (JP, A) JP-A-54-68246 (JP, A) JP-A-57-190957 (JP, A)

Claims (1)

(57) [Claims] 1. A magnetic powder is dispersed in a binder resin comprising polypropylene, polyethylene or a derivative thereof and polyvinylidene fluoride as essential components and a blending ratio of polyvinylidene fluoride of 0.1 to 20% by weight. A carrier for an electrophotographic developer, comprising: