JP2943932B2 - Electrophotographic carrier and method of manufacturing the same - Google Patents

Description

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 magnetic material-dispersed carrier as a constituent component and a method for producing the same.

(Prior Art) In electrophotography, a photoconductive material such as selenium is used as a photoreceptor, an electric latent image is formed by various methods, and toner is applied to the latent image by a magnetic brush developing method or the like. A method of attaching and visualizing the image 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.

By the way, conventionally used carriers include a conductive carrier and an insulating carrier.

Although the conductive carrier is generally excellent in solid developability, it is inferior in fine line reproducibility, and it is necessary to incorporate a special charge control agent into the toner in order to extend the life.

Further, the coat-based insulating carrier is excellent in life, reproducibility of fine lines, etc., but has a drawback that it is inferior in solid reproducibility. For the purpose of solving these disadvantages, a carrier having a small particle diameter in which magnetic fine particles are dispersed in a binder resin, that is, a carrier for microtoning has been used.

However, the inconvenience that the carrier adheres to the photosensitive material due to the carrier having a small particle diameter, the inconvenience that the charge amount greatly changes between high humidity and low humidity due to the magnetic particles liberated on the surface, In addition, there is an inconvenience that the service life cannot be drastically extended due to the difficulty in treating the carrier surface.

The present inventors have proposed a carrier in which a coating layer containing titanium dioxide powder is provided on the surface of a magnetic material-dispersed carrier core in order to solve these disadvantages. (Japanese Patent Laid-Open No. 2
-43566) This magnetic substance-dispersed carrier has a high-quality image excellent in reproducibility of fine line portions and solid portions by appropriately reducing the electrical resistance of the carrier by including titanium dioxide powder in the coating layer. It was intended to obtain.

(Problems to be Solved by the Invention) However, in the above-mentioned magnetic substance-dispersed carrier, it is difficult to uniformly disperse the titanium dioxide powder in the coating layer.
In addition, the dispersing operation required a long time. When the dispersion state of the titanium dioxide powder becomes non-uniform, the electric resistance and the charge amount fluctuate. As a result, environmental stability and stability over time are lacking, and the life cannot be sufficiently extended.

Therefore, the present invention solves the above problems and improves the dispersibility of the titanium dioxide powder in the coating layer, thereby stabilizing the electric resistance and the charge amount and forming a high-quality image. An object of the present invention is to provide a magnetic material-dispersed carrier and a method of manufacturing the same.

(Means for Solving the Problems) The present invention comprises (1) forming a resin coating layer containing titanium dioxide powder on the surface of dispersed carrier core particles in which magnetic powder is dispersed in a binder resin. In the electrophotographic carrier, an electrophotographic carrier characterized by including a coupling agent in the resin coating layer, and
(2) A magnetic powder is dispersed in a binder resin to form dispersed carrier core particles. On the other hand, a coating solution is prepared by adding a titanium dioxide powder and a coupling agent to a coating resin solution. The method for producing an electrophotographic carrier according to the above (1), wherein the coating liquid is applied to the surface of the core particles to form a coating layer.

(Function) The present invention relates to a method of forming a coating layer on a surface of a carrier core in which a magnetic powder is dispersed in a binder resin by applying a coating solution containing a titanium dioxide powder to a coating solution. Is added to allow uniform dispersion of the titanium dioxide powder in the coating layer.

Examples of the binder resin used in the magnetic material-dispersed carrier core of the present invention include styrenes such as styrene, chlorostyrene and vinylstyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate;
Vinyl esters such as vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, methacrylic acid Esters of α-methylene aliphatic monocarboxylic acids such as butyl and dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether;
Homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone can be exemplified. Particularly typical binder resins include polystyrene and styrene-alkyl acrylate. Copolymers, styrene-alkyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-maleic anhydride copolymers, polyethylene, and polypropylene can be exemplified. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and wax can be used.

The magnetic fine particles used in the carrier core of the present invention dispersed in a binder resin may be all commonly used fine particles of a ferromagnetic substance. Specifically, triiron tetroxide, γ-III Iron dioxide, various ferrite powders, chromium oxide,
Various metal fine powders can be exemplified.

The content of the magnetic particles is usually about 30 to 95% by weight, preferably 45 to 90% by weight, based on the total amount of the binder resin, and gives good results.

In the carrier core of the present invention, a resin, a charge control agent, a filler, other fine powder, and the like are added for the purpose of charge control, dispersion improvement, strength reinforcement, fluidity improvement, etc. in addition to the binder resin and the magnetic fine particles. It is also possible.

A method for producing a carrier core is generally a method in which the magnetic powder, the binder resin and other additives are heated and melt-kneaded by a kneader, a roll mill, a Banbury mixer, and the like, and the melt-kneaded material is cooled, and then pulverized and classified. It is. Moreover, it is also possible to spray-cool and solidify the melt-kneaded material with a spraying device such as a nozzle type or a disk type.

The average particle size of the carrier core of the present invention is 20% from the viewpoint of the balance between the life of the developer, the adhesion of the carrier to the photoconductor, and the image quality.
It is appropriate that the thickness is from 400 to 400 μm, more preferably from 30 to 200 μm.

Next, the coating layer that covers the surface of the carrier core will be described.

Materials used for the coating layer in the present invention are all general soluble resin group, specifically, styrene, chlorostyrene,
Stins such as vinyl styrene; 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 acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl methyl ketone, vinyl hexyl Homopolymers or copolymers such as ketones and vinyl ketones such as vinyl isopropenyl ketone can be exemplified. Particularly typical resins for the coating layer include polystyrene, alkyl polyacrylate, and polymethacrylic acid. Le, styrene - alkyl acrylate copolymer, styrene - alkyl methacrylate copolymer, styrene - acrylonitrile copolymer, styrene -
Examples thereof include a butadiene copolymer, a styrene-maleic anhydride copolymer, polyethylene, and polypropylene. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and wax can be used.

Furthermore, mention may be made of halogen-containing polymers, specifically, olefin chlorides, monomers containing fluorine in the main chain, such as tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, monofluoroethylene, and hexafluoropropylene. And the like, and combinations of these monomers with ethylene, propylene, butylene, vinyl chloride, vinylidene chloride, trifluoroethylene, and other copolymerizable unsaturated bond-containing monomers. Is mentioned.

Further, a compound containing fluorine in the side chain is also suitable,
In particular, fluorinated alkyl acrylates and fluorinated alkyl methacrylates are typical compounds.

Further, a fluorinated epoxy resin, a fluorinated polyester resin, a fluorinated silicon resin, or the like can be used.

These coating materials are used alone or in combination of two or more.

The titanium dioxide powder used in the present invention has a particle size of 2 μm or less, preferably 1 μm or less. The resistance value is 10 ¹² Ωcm or less, preferably 10 ¹⁰ Ωcm or less. The amount of titanium dioxide powder added to the coating layer is
1 to 100% by weight, preferably 5 to 70% by weight of the coating layer resin
It is appropriate to use% by weight.

As the coupling agent used in the present invention, a titanium-based or aluminum-based coupling agent is optimal, and specifically, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, bis (dioctylbylphosphate) oxyacetate titanate, Acetoalkoxy aluminum diisopropylate and the like can be used.

The addition amount of the coupling agent is preferably 0.01 to 30% by weight, and more preferably 0.1 to 10% by weight, based on the titanium dioxide powder.

The method of adding the coupling agent, when adjusting the coating solution,
A coupling agent is added and dispersed together with a coating resin, a solvent, titanium dioxide powder, and other additives, or only the titanium dioxide powder and the coupling agent are previously uniformly mixed using a Henschel mixer, a V-type blender, or the like. After that, it may be added to the coating solution.

If necessary, charge control, dispersion improvement, strength reinforcement,
Resins, charge control agents, fillers, other fine powders, and the like can be added to the coating resin for the purpose of improving the fluidity and other purposes.

As a method for forming the coating layer, first, a solution in which the resin for the coating layer, the titanium dioxide powder, the coupling agent, and other additives as necessary are dissolved or dispersed in a solvent that does not dissolve the binder resin for the carrier core. Is prepared, and then the above solution is applied to the surface of a carrier core containing the binder resin for carrier core and magnetic fine particles as essential components, and the solvent is removed to form a coating layer.

For dispersing the titanium dioxide powder in the coating layer solution, an attritor, a disperser, a sand mill, a ball mill or the like is used. Further, as the coating device, a fluidized bed, a spray drier, a knea coater and other coating devices can be used.

The thickness of the coating layer of the carrier of the present invention is 0.01 to 5 μm,
Preferably, the thickness is 0.1 to 1 μm.

The carrier thus obtained is mixed with a toner and used as a magnetic brush developer for developing an electrostatic latent image. As the toner, all chargeable toners used in ordinary electrophotography, in which a colorant is dispersed in a binder resin, can be used.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these embodiments.

Example 1 First, magnetite powder (EPT-1000, manufactured by Toda Kogyo)
70 parts by weight of polyethylene and 30 parts by weight of polyethylene (Mitsui High Wax 400P, manufactured by Mitsui Petrochemicals Co., Ltd.) are sufficiently heated and melted and kneaded with a pressure kneader, cooled and solidified using a disk type spraying device, and classified to average particle diameter of 100 μm. To obtain a dispersion type carrier core of spherical magnetic particles.

Next, 1 part by weight of polymethyl methacrylate, 0.1 part by weight of titanium dioxide powder having an average particle size of 0.5 μm, and 0.001 part by weight of isopropyl triisostearoyl titanate were added to 100 parts by weight of the carrier core in 10 parts by weight of toluene. The mixture was dispersed in a ball mill for 1 hour, the dispersion solution was sprayed on a carrier core fluidized in a fluidized bed coating apparatus, the solvent was removed, and the dispersion was dried to obtain a spherical carrier.

Comparative Example 1 A carrier was obtained under the same conditions as in Example 1 except that in the preparation of the coating solution of Example 1, the addition of isopropyl triisostearoyl titanate was omitted.

Example 2 In the preparation of the coating solution of Example 1, the addition amount of the titanium dioxide powder was increased to 0.5 part by weight, and the titanium dioxide powder was previously mixed with 0.005 part by weight of isopropyl triisostearoyl titanate for 10 minutes using a hexiel mixer. A carrier was obtained under the same conditions as in Example 1 except that the pretreatment was carried out, and then the mixture was added to 10 parts by weight of toluene together with 1 part by weight of polymethyl methacrylate and dispersed by a ball mill for 3 hours.

Comparative Example 2 A carrier was obtained under the same conditions as in Example 2 except that titanium dioxide powder in which the pretreatment step of Example 2 was omitted was directly added.

For the carriers of Examples and Comparative Examples, styrene-
Average particle size 11μ consisting of 100 parts by weight of normal butyl methacrylate copolymer (80/20) and 10 parts by weight of carbon black
m was used as a developer by mixing with the above carrier so that the concentration became 3% by weight.

These developers were developed using an FX4790 copier manufactured by Fuji Xerox Co., Ltd. to obtain the initial charge amount, solid image density, background stain, fine line reproducibility, and the charge amount when running 100,000 sheets, solid image density, background stain. , Fine line reproducibility, etc., and furthermore, high temperature and high humidity (30 ° C, 80% RH) and low temperature and low humidity (10 ° C, 30%
% RH). The results are as shown in the following table, and the superiority of the carrier according to the present invention was clarified.

(Effects of the Invention) According to the present invention, by employing the above configuration, the titanium dioxide powder can be uniformly dispersed in the coating resin by the coupling agent, and as a result, stable control of the charge amount and the electric resistance can be achieved. As a result, a high-quality image can be obtained without being affected by changes in environmental conditions, and the life of the developer can be extended. Further, by adding the coupling agent, the dispersion and mixing time of titanium dioxide can be significantly reduced, and the pot life of the lacquer can be extended to suppress the sedimentation of titanium dioxide.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasuo Matsumura 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside the Fujimatsu Rocks Co., Ltd. In-house (56) References JP-A-58-59457 (JP, A) JP-A-64-29860 (JP, A) JP-A-62-28772 (JP, A) JP-A-55-155363 (JP, A) JP-A-60-52859 (JP, A)

Claims (3)

(57) [Claims] 1. An electrophotographic carrier comprising a resin coating layer containing a titanium dioxide powder formed on the surface of dispersion type carrier core particles in which a magnetic powder is dispersed in a binder resin. An electrophotographic carrier, characterized in that a coupling agent is contained in the carrier. 2. The electrophotographic carrier according to claim 1, wherein at least one of a titanium-based and / or aluminum-based coupling agent is used as said coupling agent. 3. A coating liquid is prepared by dispersing magnetic powder in a binder resin to form dispersed carrier core particles, and adding a titanium dioxide powder and a coupling agent to a coating resin solution. 3. The method for producing an electrophotographic carrier according to claim 1, wherein the coating liquid is applied to the surface of the carrier core particles to form a coating layer.