JPH0287158A - Binary developer - Google Patents

Abstract

PURPOSE:To prevent deterioration of acceptance potential at the time of running by coating a negatively chargeable carrier with a coating material containing a specified copolymer as an essential component. CONSTITUTION:The binary developer comprises a positively chargeable toner containing fine magnetic particles and the negatively chargeable carrier obtained by coating core particles with the coating material containing the copolymer of vinylidene fluoride and trifluorocthylene or hexafluoropropylene as an essential component, thus permitting potential rising speed to be high and surface staining resistance to be good, accordingly, deterioration of acceptance potential at the time of running to be avoided, and early occurrence of fog and staining in the machine to be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developer used for developing electrostatic latent images in electrophotography and electrostatic recording. More specifically, a negatively chargeable carrier consisting of a magnetic core agent and a coating resin layer, which has excellent chargeability, surface contamination resistance, mechanical strength, adhesion between the core and the coating layer, etc., and a positively chargeable carrier. The present invention relates to a two-component developer for magnetic brushes comprising a magnetic toner and a magnetic brush.

Conventional technology In electrophotography, a photoconductive substance such as selenium is used as a photoreceptor, an electrical latent image is formed using various means, and this latent image is developed using a magnetic brush development method or the like. Generally, a method is adopted in which toner is attached to the image and visualized.

In this development step, carrier particles called carriers are used to impart an appropriate amount of positive or negative electricity to the toner and transport it to the development area.

Carriers are generally divided into coated carriers and uncoated carriers, but when considering developer life, etc.
Since the former is superior, various types of coated carriers have been developed, and coated carriers using, for example, vinyl fluoride polymers, have been developed and are in practical use.

(For example, Japanese Unexamined Patent Publication No. 56-113146) Problems to be Solved by the Invention] - There are various properties required for carriers, but particularly important properties include appropriate charging properties, impact resistance, Abrasion resistance, good adhesion between the core material and coating material, uniformity of charge distribution, etc. can be improved.

Considering the above-mentioned required characteristics, the coated carriers that have been used in the past still have problems to be improved, and no perfect one is known to date.For example, vinyl fluoride polymers Although acrylic polymers are satisfactory in terms of mechanical strength and adhesion with the core material, they have poor surface stain resistance. It is said that there is a problem in chargeability. In any case, the current situation is that we are forced to use coating materials that have advantages and disadvantages.

In view of the current situation, the inventors of the present invention have conducted various studies and examinations to improve the various drawbacks of the conventional methods, and have found that the use of a specific coating material is effective in improving the required characteristics of the coated carrier. It was found that Furthermore, the present inventors have discovered that a developer consisting of a toner in which fine magnetic particles are dispersed and the carrier gives extremely good results in terms of images, lifespan, internal contamination, etc., and has completed the present invention. I ended up doing it.

Therefore, an object of the present invention is to provide a novel developer used for developing electrostatic latent images in electrophotography and electrostatic recording.

Another object of the present invention is that the charging speed is high and the surface contamination resistance is good, so that the charge amount does not decrease during running, and since the toner contains magnetic fine particles, it is possible to avoid contamination inside the machine. The object of the present invention is to provide a developer that does not cause

Means for Solving the Problems The object of the present invention is to provide a negative electrode formed by coating a core material with a coating material containing as an essential component a copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene. This is achieved by a two-component developer for magnetic brush development consisting of a charged carrier and a positively charged toner containing fine magnetic particles dispersed in a binder resin.

The present invention will be described in detail below.

In the present invention, the coating agent for coating the core material is
It is necessary to contain a copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene as an essential component. Even if the coating material is composed only of a copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene, it will have sufficient chargeability and film-forming properties for practical use, but the charge cannot be adjusted freely. In order to improve the strength and adhesion between the coating material and the core, it is preferable to use an acrylic acid ester polymer or copolymer, or a trifluoromonochloroethylene-vinyl chloride copolymer. The mixing ratio of the copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene and the acrylic acid ester polymer or trifluoromonochloroethylene-vinyl chloride copolymer is usually 99; 1 to 20 by weight.
:80 is appropriate, and is adjusted according to the charge increase rate and charge decay rate of the toner used.

The copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene used in the present invention is produced by emulsion polymerization or suspension polymerization. The copolymerization ratio of vinylidene fluoride and trifluoroethylene or hexafluoropropylene is suitably in the range of 90:10 to 50:50. In addition, the solution viscosity is 0.7 to 1.5, the melting point (
It is preferable that the monocarbonate p) is in the range of 130 to 160'C.

On the other hand, examples of the acrylic ester polymer or acrylic ester that is a constituent component of the copolymer that can be used with the above copolymer include esters of acrylic acid or methacrylic acid and various alcohols. Such alcohols include, for example, alkanols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, and hexadecyl alcohol; Halogenated alkanols in which a part of these alkanols is halogenated; alkoxyalkanols such as methoxyethyl alcohol, ethoxyethyl alcohol, methoxypropyl alcohol, and ethoxypropyl alcohol; benzyl alcohol,
Examples include aralkyl alcohols such as phenethyl alcohol and phenylpropyl alcohol; alkenyl alcohols such as allyl alcohol and tarotonyl alcohol.

Further, the above acrylic acid ester may be copolymerized alone or with two or more types, and may be copolymerized with one or more types of other copolymerizable monomers, if necessary. In that case, it is preferred that the acrylic esters account for 25% by weight or more, preferably 50% by weight or more of the total monomers.

Examples of the core material used in the present invention include powders such as iron powder, iron oxide powder, carbonyl iron powder, magnetite, nickel, and ferrite, and usually as a carrier, particles of a size of 10 to 500 μm are used. The one that is the same is used.

The carrier particles in the present invention can be obtained by surface-treating the core material as described above using the coating agent as described above, and forming a coating layer on the surface of the core material by chemical bonding or adsorption.

For surface treatment of the core material, for example, the core material is immersed in a solution obtained by dissolving one or more of the above-mentioned polymers in a suitable solvent, followed by desolvation, drying, A method such as baking at a high temperature can be used.

In these methods, high temperature baking treatment is not necessarily required.

The coating amount of the polymer is usually 0.05% of the core material.
It is preferably 3.0% by weight.

On the other hand, the positively charged toner mixed with the above negatively charged carrier contains magnetic fine particles in the binder resin, and the magnetic fine particles include triiron tetroxide, HnZn ferrite, Mien ferrite, etc. Any commonly used magnetic powder can be used. It is usually preferable that the toner contains 5 to 20% by weight of these magnetic particles.

In addition, as the binder resin, styrene resin, styrene-acrylic copolymer, polyolefin, polyester resin,
Epoxy resin and any other materials commonly used in toners can be used.

The positively charged toner of the present invention can contain various dyes and pigments, such as carbon black, as colorants.

In the present invention, fine particles smaller than the average particle size of the toner, such as silicon dioxide, aluminum oxide, titanium oxide, zinc stearate, and fine resin powder, can be attached to the surface of the toner particles by external addition.

The two-component developer for magnetic brush development of the present invention comprises the above-mentioned negatively charged carrier and positively charged carrier. It is obtained by mixing with 4F electric toner.

Example Hereinafter, the present invention will be explained in more detail with reference to Examples.

However, the present invention is not equally limited by these examples.

Example 1 16 parts by weight of a copolymer of vinylidene fluoride and trifluoroethylene (copolymerization ratio 85:15) and 4 parts by weight of polymethyl methacrylate were dissolved in 100 parts by weight of dimethylformamide, and the resulting solution was dissolved into average particles. In addition to 2000 parts by weight of spherical iron oxide powder having a diameter of 100 fields, a coating treatment was performed using a vacuum kneader coater to obtain a negatively charged carrier.

On the other hand, 80 parts by weight of styrene and 2 parts by weight of butyl acrylate
75 parts by weight of copolymer consisting of 0% by weight (molecular weight 200%
,000), 10 parts by weight of carbon black, 12 parts by weight of magnetic fine particles (magnetite), and 3 parts by weight of charge control agent.
After kneading the parts by weight using a pressure kneader and cooling,
The powder was pulverized using a hammer mill, then a jet mill, and further classified to obtain a toner having an average particle size of 10a.

Three parts by weight of the obtained toner were mixed with 100 parts by weight of the carrier to obtain a two-component developer for magnetic brush development.

Example 2 20 parts by weight of a copolymer of vinylidene fluoride and hexafluoropropylene (copolymerization ratio 80:20) was dissolved in 100 parts by weight of dimethylformamide, and the resulting solution was mixed into spherical iron oxide powder with an average particle size of 100ρ. In addition to 2000 parts by weight, coating was performed using a vacuum kneader coater to obtain a negatively charged carrier.

Next, the same procedure as in Example 1 was carried out to obtain a two-component developer for magnetic brush development.

Comparative Example 1 Two-component development for magnetic brush development was carried out in the same manner as in Example 1, except that the copolymer of vinylidene fluoride and trifluoroethylene in Example 1 was changed to vinylidene fluoride homopolymer. obtained the drug.

Comparative Example 2 A two-component developer for magnetic brush development was obtained in the same manner as in Example 1, except that the magnetic fine particles in the toner were replaced with styrene-butyl acrylate copolymer.

Using the two-component developer for magnetic brush development in Examples 1 and 2 and Comparative Examples 1 and 2 above, an electrophotographic copying machine (Xerox 1065 (using an organic photoconductive belt type photoreceptor))
A continuous copying test was carried out using the following method.

The results were as shown in the table below.

Note) ■The amount of charge is measured using a blow-off measuring device.

■ Peeling of the coating was observed using a scanning electron microscope.

■The lifespan is determined when the original density 1.0 part is 0.7 or less and the white part is 0.03 or more.

Effects of the Invention Since the two-component developer for magnetic brush development of the present invention has the above-mentioned structure, it has a high charging rate and good surface stain resistance, so it does not cause a decrease in the amount of charging during running. Therefore, there is no possibility of early fogging or internal contamination.

Furthermore, since the magnetic toner is used in combination with the above-mentioned carrier, there is no contamination of the inside of the machine due to the toner, and the service life is long, so that copy images of good quality can be obtained stably for a long period of time.

Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Tsuyoshi Watanabe

Claims (1)

[Claims] (1) Consisting of a negatively charged carrier coated with a coating agent containing a copolymer of vinylidene fluoride and trifluoroethylene or hexafluoropropylene as an essential component, and a positively charged toner containing magnetic fine particles. A two-component developer for magnetic brush development.