JPH05100492A - Carrier for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To provide a carrier for developing an electrostatic charge image capable of giving stable image quality by preventing the exfoliation and chipping of the surface layer of a carrier for developing an electrostatic charge image, improving property of maintaining a stuck and electrostatically charged toner, suppressing a change in electrostatic chargeability due to an environmental change, improving image retentivity and preventing the sticking and consumption of the carrier. CONSTITUTION:In a carrier for developing an electrostatic charge image produced by mixing magnetic core particles with coating resin in a dry state and carrying out heating, melting and cooling, a ferrite magnetic body having 100-1,000cm<2>/g specific surface area is used as the magnetic core particles and the rate of surface coating of the magnetic body with the resin is regulated to >=90%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic charge image developing carrier used for developing an electrostatic charge image formed by an electrophotographic method, an electrostatic recording method or the like with a two-component developer.

[0002]

2. Description of the Related Art A method of visualizing image information through an electrostatic charge image such as an electrophotographic method is currently used in various fields. In the electrophotographic method, an electrostatic latent image formed on a photoreceptor by a charging and exposing process is developed with a toner-containing developer, and then visualized through a transferring and fixing process. As a developer used for development, a two-component developer in which a toner and a carrier are mixed and a toner alone such as a magnetic toner are used.
There is a component developer, but the two-component developer is provided with functions such as stirring, carrying, and charging of the developer by the carrier, and the functions are separated as the developer, so that it has the characteristic of good controllability. Yes, it is widely used today. In particular, a developer using a carrier coated with a resin has excellent charge controllability, and it is relatively easy to improve environmental dependency and stability over time. Further, as a developing method, a cascade method or the like has been used in the old days, but at present, a magnetic brush method using a magnetic roll as a developer transporting unit is mainly used.

[0003]

In the magnetic brush method using a two-component developer, the image density is lowered due to the charge deterioration of the developer, the background is markedly stained, and the image is roughened due to the carrier being attached to the image. There are problems such as the consumption of carriers and the occurrence of uneven image density. The cause of charge deterioration of the developer is mostly due to peeling or chipping of the carrier charge control layer, or contamination of the carrier surface by the toner component. The carrier adhesion mechanism to the image is due to the decrease of the carrier resistance, the induction charge injection and adhesion to the image area and the insufficient upper limit control of the carrier charge amount. It is considered to adhere to the part.

Therefore, the present invention solves the above problems, prevents peeling or chipping of the surface layer of a carrier for an electrostatic image developer, improves the toner component adhesion charge maintaining property, and reduces environmental fluctuations. It is an object of the present invention to provide a carrier for developing an electrostatic charge image, which suppresses a change in chargeability due to the above, improves image quality maintenance, prevents carrier adhesion and carrier consumption, and obtains stable image quality.

[0005]

The present invention provides a carrier for developing an electrostatic charge image produced by mixing magnetic core particles and a coating resin in a dry state, heating, melting and cooling, and having a specific surface area of 100. The carrier for developing an electrostatic charge image is characterized by using a ferrite magnetic substance of up to 1000 cm ² / g and having a resin surface coverage of 90% or more.

[0006]

[Function] Conventionally, when resin coating is applied to magnetic core particles,
It is important to improve the adhesiveness at the interface between the resin and the core particles and improve the uniformity of coating. If the adhesion is poor,
The resin coating is easily peeled off due to the mechanical stress, and the exposed portion is easily contaminated with the toner. Further, if the uniformity of the coating is impaired, an exposed portion is formed on the surface of the core particle from the beginning, and not only toner contamination but also charge-injection carrier adhesion due to a decrease in electric resistance occurs, which causes a change in temperature and humidity. Environmental fluctuations in charging properties also tend to increase.
In particular, when manufacturing with a resin coating method that does not use a solvent,
There is a strong tendency for the resin and the core particles to become incompatible with each other, and there has been a demand for improvement.

The present inventors have studied various materials and found that the specific surface area of the ferrite magnetic core particles and the resin coverage are important for solving the above problems. That is, the ferrite particles, since the true density is low, the stress received by the particles is also low, which is clearly advantageous as compared with the iron powder particles normally used, but depending on the sintering conditions,
Micro unevenness is likely to occur on the surface, and when manufacturing with a resin coating method that does not use a solvent, not only can uniform coating not be possible, but since there are often voids inside the coated part, the film strength is Noticeably smaller On the other hand, if the surface is too smooth, the anchoring effect between the resin coating and the core particles is insufficient, resulting in poor adhesion and a large amount of free resin generated during production.

Therefore, it is necessary to optimize the surface irregularities of the ferrite particles, but the measurement of the specific surface area is effective for quantifying the irregularities. In addition, due to the recent progress in surface analysis methods, it has become possible to analyze the carrier surface composition and to quantify the coverage. Coverage is 100
% Is most desirable, but fluctuations occur due to variations in carrier composition and manufacturing conditions, so it is necessary to set a lower limit value. The surface irregularities of the ferrite particles, the result of the study, specific surface area measured by BET method by nitrogen adsorption is suitable in the range of 100~1000cm ² / g, in the range of 200~700cm ² / g as more preferable range Turned out to be desirable. As for the coverage, F for all the quantitative elements by X-ray photoelectron spectroscopy (XPS)
When quantified by the ratio of e, it was found that if it was 90% or more, the deterioration of the charging property and the carrier adhesion were improved.

As the coating resin used in the present invention, a resin which has been generally used conventionally can be used. For example, a fluorine-containing resin is mainly used for a negatively charged carrier and a resin for a positively charged carrier is used. Acrylic resins are mainly used. Examples of fluororesins include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethylene, monochloroethylene, homopolymers of vinyl-based fluorine-containing monomers such as trifluoroethylene, or copolymers. As other examples, styrenes such as styrene, chlorostyrene, and methylstyrene, methyl methacrylate, methyl acrylate, propyl acrylate, lauryl acrylate, lauryl methacrylate, methacrylic acid, acrylic acid, butyl methacrylate, butyl acrylate, 2
Α-methylene aliphatic monocarboxylic acids such as ethylhexyl acrylate and ethyl methacrylate; nitriles such as acrylonitrile and methacrylonitrile; vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine, or vinyl ethers and vinyl ketones, It is possible to use olefins such as ethylene, propylene and butadiene, homopolymers such as methylsilicone and silicons such as methylphenylsilicone, or copolymers. It is also possible to use polyesters containing bisphenol, glycol and the like. These resins are used alone or as a mixture.

The coating amount of the coating resin is about 0.3 to 10% by weight based on the total amount of fluororesin / combined resin with respect to the carrier.
A range of 0.5 to 3% by weight is preferable. Ferrite particles are used as the core particles, and those having a shape close to a sphere are selected in view of the regulation of the specific surface area.
The average particle size is usually about 20 to 200 μm. For manufacturing the carrier of the present invention, a heating type kneader,
A heating type Henschel mixer and a heating type UM mixer are used, and a heating type fluidized rolling bed, a heating type kiln and the like can also be used depending on the compounding ratio such as the amount of resin.

The toner constituting the two-component developer used in the present invention is a binder resin in which a toner component such as a colorant is dispersed. Examples of the binder resin used here include styrene and parachlorostyrene. , Styrenes such as α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methacrylic acid Α-Methylene aliphatic monocarboxylic acid esters such as lauryl and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile;
Vinyl pyridines such as vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; ethylene, propylene, isoprene, butadiene and the like. Of unsaturated hydrocarbons and halogenated unsaturated hydrocarbons such as halogenated chloroprene, or a copolymer obtained by combining two or more of these monomers, and These mixtures, further, vinyl condensation resin such as rosin-modified phenol formalin resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin or a mixture of these and the vinyl resin. It can be.

Examples of the colorant include carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or a mixture thereof. Examples of the toner component other than the colorant include a charge control agent, an anti-offset agent, a fluidity improver, and the like, and may contain a magnetic powder if necessary.

[0013]

EXAMPLES Various Cu-Zn ferrite particles having a central particle diameter of about 80 μm and a specific surface area shown in Table 1 and Table 1
The listed resins are mixed in a 5 L small heating type kneader for 8 minutes, and then the heating medium temperature is set to 180 ° C.
After stirring for 0 minutes, the heater is turned off and the draft is released under cold air to stir for 30 minutes while accelerating the cooling. When the temperature of the mixture cools to 60 ° C., it is taken out and 250 μm
Sieving was carried out with a sieve of m to obtain a carrier. The specific surface area of the ferrite particles was measured by the BET method using nitrogen adsorption using an area meter manufactured by Strayline. Moreover, the measurement of the resin coverage by XPS uses an X-ray photoelectron spectroscopy analyzer manufactured by JEOL Ltd. to measure carbon, oxygen, iron,
It was determined by subtracting the ratio of copper, zinc, and iron when the total sum of peak intensity of detected elements for silicon, copper, zinc, and fluorine is 100%. The measured values are shown in Table 1.

On the other hand, the toners of Samples 1, 2 and 3 were 84% by weight of a binder resin (styrene-n-butyl methacrylate), carbon black (R330 manufactured by Cabot Co.) 10
% By weight, charge control agent (Bontron N0 manufactured by Orient Co., Ltd.
4) 2 wt% and 4 wt% of polyethylene wax (400P manufactured by Mitsui Petrochemical Co., Ltd.) were kneaded and pulverized to obtain a toner having an average particle diameter of 11 μm. The toners of Samples 4, 5 and 6 were 87% by weight of a binder resin (styrene-n-butylmethacrylate), 8% by weight of carbon black (BPL made by Cabot Co.) and 1% by weight of a charge control agent (TRH made by Hodogaya Chemical Co., Ltd.). %, And 4% by weight of polyethylene wax (400P manufactured by Mitsui Petrochemical Co., Ltd.) were used, and a toner having an average particle diameter of 11 μm was obtained by a kneading and pulverizing method.

The above toner was mixed with the above carrier so as to have a concentration of 4% to obtain a developer. As the developer containing the toner of Samples 1, 2, and 3, a modified FX5017 machine manufactured by Fuji Xerox Co., which uses an organic photoconductor, is used.
In addition, the developer containing the toner of Samples 4, 5 and 6 is FX503 manufactured by Fuji Xerox Co., Ltd. using an inorganic photoconductor.
An image quality maintenance test was performed using a 0 remodeling machine. The results are shown in Table 1.
It was shown to. In the table, ○ indicates no problem, the type of coating resin, VDF is vinylidene fluoride, VDF-4FE is vinylidene fluoride-tetrafluoroethylene copolymer, and VDF-6FP is vinylidene fluoride-propylene propylene copolymer. Polymer, MPS is a methylphenylsilicone copolymer, PMMA is an abbreviation for polymethylmethacrylate, and the number following each abbreviation indicates a monomer ratio.

[0016]

[Table 1]

[0017]

According to the present invention, by adopting the above-mentioned constitution, it is possible to prevent peeling or chipping of the surface layer of the carrier for an electrostatic image developer, and improve the toner component adhesion charge maintaining property. Further, it is possible to suppress the change in charging property due to environmental changes and improve the image maintainability, and further to prevent carrier adhesion and carrier consumption and obtain stable image quality.

Claims (1)

[Claims] 1. A carrier for developing an electrostatic charge image produced by mixing magnetic nucleus particles and a coating resin in a dry state, heating, melting and cooling, and having a specific surface area of 100 to 1000 cm.
^A carrier for developing an electrostatic charge image, characterized by using a ² / g ferrite magnetic material and having a resin surface coverage of 90% or more.