JPH0833684B2 - Carrier for developer - 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 carrier which is a constituent component, and more particularly, to a carrier in which a magnetic substance is dispersed.

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

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

[Problems to be Solved by the Invention] Although there are various characteristics required for the carrier, appropriate charging characteristics, impact resistance, abrasion resistance,
Developability, developer life, etc. can be mentioned.

In view of the above-mentioned required characteristics, 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 reproducibility, 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, reproducibility of fine wires, etc., but is inferior in solid reproducibility. For the purpose of remedying these drawbacks, small particle size carriers in which magnetic fine particles are dispersed in a binder resin, so-called microtoning carriers, have been proposed and put into practical use. It has the disadvantage of adhering to the body.
This phenomenon can be prevented by increasing the particle size of the carrier. However, the increase in the particle size of the carrier lowers the chargeability. As a result, problems such as generation of fog and contamination in the machine occur.

Accordingly, a main object of the present invention is 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 carrier for magnetic brush development, which prevents a decrease in charge amount, as a result, does not cause fog early generation and in-machine contamination, and has excellent developer life and high-speed developability. Especially.

[Means for Solving the Problems] The present invention has the above and other objects by spray cooling a binder resin containing a polyolefin having a functional group and a carrier material melt containing magnetic powder as essential components. This is achieved by a carrier for a developer, which is characterized in that the obtained average particle size is 20 to 400 μm.

The functional group introduced into the polyolefin in the present invention, for example, a hydroxyl group, a carboxylic acid group, an ester group, a carbonyl group, an oxygen-containing functional group such as an ether group, a nitrogen-containing functional group such as amino, amide, imide, nitrile, chlorine , Fluorine, halogen-containing functional groups such as perfluoroalkyl groups, aromatic groups such as phenyl and naphthyl, silicon atom-containing groups, and the like. Of these, preferred are carboxylic acid groups, hydroxyl groups, amino groups, and phenyl groups. Is. These functional groups can be used alone or in combination of two or more.

Various methods can be used to introduce a functional group of a polyolefin, depending on the functional group, such as direct chemical treatment of the polyolefin such as oxidation, reduction and halogenation, copolymerization of an olefin monomer and a functional group-containing monomer, polyolefin and a functional group. Examples of the method include co-polymerization with a group-containing monomer and co-polymerization with a functional group-containing polymer and an olefin monomer.

Examples of the olefin compound used in the present invention include ethylene, propylene, butylene, isobutylene and the like.

As the binder resin for the carrier used in the present invention, all of the general thermoplastic resin group can be used, but specifically, styrenes such as styrene, chlorostyrene, vinyl styrene: ethylene, propylene, butylene. , Monobutyl olefin such as isobutylene: vinyl acetate, vinyl propionate, vinyl benzoate, vinyl ester such as vinyl butyrate: methyl acrylate, ethyl acrylate,
Ester of α-methylene aliphatic monocarboxylic acid such as butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate: vinyl methyl ether, vinyl ethyl ether,
Vinyl ethers such as vinyl butyl ether: homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone and the like can be exemplified, and particularly typical binder resins are polystyrene and styrene. Examples thereof include an alkyl acrylate copolymer, a styrene-alkyl methacrylate copolymer, a styrene-acrylonitrile copolymer, a styrene-butadiene copolymer, a styrene-maleic anhydride copolymer, polyethylene and polypropylene.

Furthermore, polyester, polyurethane, epoxy resin,
Silicone resin, polyamide, modified rosin, paraffin,
Waxes can be mentioned.

In the present invention, the amount of the functional group-containing polyolefin contained in the binder resin is 1 to 70% by weight based on the total amount of carrier components.

The magnetic fine particles used in the present invention may be all fine particles of a ferromagnetic material that are usually used, but specifically, ferric tetroxide, γ-iron sesquioxide, various ferrite powders,
Examples include chromium oxide and various fine metal powders.

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, to give good results.

Next, in the carrier production method, the binder resin, the functional group-containing polyolefin and the magnetic fine particles are essential components, and these components and other components are heated and melt mixed, and the mixture is solidified by cooling with an air stream at a relatively low temperature without solidifying the mixture. Is manufactured by

More specifically, the manufacturing apparatus includes a heating and melting mixer as a pretreatment facility and a kneaded material viscosity adjusting tank, and further includes a pump for conveying the kneaded material to a spraying device and a cooling tower for cooling and solidifying the sprayed kneaded material. What is used is used.

As a heating and melting and mixing device, a kneader, a roll mill,
It is possible to use a Banbury, a sand mill, an attritor, a Henschel mixer, etc., and as a spraying device, a nozzle type or a disc type is relatively suitable for obtaining a carrier having a small particle size, but is not limited to these. Not something.

In addition to binder resin, functional group-containing polyolefin and magnetic fine particles, resin, charge control agent, coupling agent, filler, other fine powder, etc. inside the carrier for charge control, dispersion improvement, strength reinforcement, fluidity improvement and other purposes. Can also be added to.

The carrier particles of the present invention can be used as they are as carrier particles, but since they have high surface smoothness and are spherical, the surface is treated with a resin, coupling agent, surfactant, charge control agent, fine powder or the like. Treatment or coating treatment can be applied.

The carrier particles of the present invention have an average particle size of 20 to 40 in view of the balance between the developer life and the adhesion of the photoreceptor carrier and the image quality.
It is suitable that the thickness is 0 μm, more preferably 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 in which a colorant is dispersed in a binder resin and which is used in a usual electrophotographic method can be used and is not particularly limited.

[Advantages of the Invention] The magnetic brush developing carrier of the present invention is obtained by spray cooling a carrier resin melt containing a binder resin containing a polyolefin having a functional group and magnetic powder as essential components. The following effects are achieved.

First, the chargeability of the carrier can be freely controlled by adjusting the type and amount of the functional group in the polyolefin.

Further, when a low surface energy group such as a fluorine-based functional group or a silicon-based functional group is introduced, the surface energy of the carrier is lowered, the toner impaction on the carrier is reduced, and the life can be extended.

Furthermore, when the carrier particles are subjected to the coating treatment, the functional layer having a good affinity for the coating material is introduced into the polyolefin, whereby the peeling of the coating layer can be prevented.

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

Example 1 Magnetic fine particles (EPT-1000, manufactured by Toda Kogyo Co., Ltd.) 80 parts Polyethylene (Mitsui High Wax 400P, manufactured by Mitsui Petrochemical Co., Ltd.) 10 parts Polyethylene introduced with a carboxyl group (acid value: 20 KOH m
g) 10 parts were heat-melted and kneaded with a pressure kneader.

Then, the mixture was spray-cooled using a disk-type spraying device to solidify and then classified to obtain a spherical magnetic particle-dispersed carrier according to the present invention having an average particle diameter of 100 μm.

Comparative Example 1 Magnetic fine particles (EPT1000, manufactured by Toda Kogyo Co., Ltd.) 80 parts Polyethylene (Mitsui High Wax 400P, manufactured by Mitsui Petrochemical Co., Ltd.) 20 parts were kneaded, granulated, classified and averaged in the same manner as in Example 1. A spherical magnetic particle dispersion type carrier having a diameter of 100 μm was obtained.

Example 2 Magnetic fine particles (EPT1000, manufactured by Toda Kogyo Co., Ltd.) 80 parts Polyethylene (Mitsui High Wax 400P, manufactured by Mitsui Petrochemical Co., Ltd.) 15 parts Polyethylene-styrene (8: 2) copolymer 5 parts Heat melting with a pressure kneader Kneaded

Then, after spraying, cooling and solidifying using a disk type spraying device, classification was carried out to obtain a spherical magnetic particle dispersed carrier according to the present invention having an average particle size of 100 μm.

Example 3 To 100 parts of the carrier particles obtained in Example 2, a 10% acetone solution of 0.5 part of a styrene-methyl methacrylate-acrylic acid (80: 15: 5) copolymer was added using a fluidized bed coating apparatus. The coated spherical magnetic particle-dispersed carrier according to the present invention was obtained by coating.

Comparative Example 2 100 parts of the carrier particles obtained in Comparative Example 1 were coated with 0.5 part of a styrene-methyl methacrylate-acrylic acid (80: 15: 5) copolymer in the same manner as in Example 3 to coat the particles. A spherical magnetic particle dispersed carrier was obtained.

The carriers obtained in Examples 1, 2, 3 and Comparative Examples 1, 2 were evaluated as developers. The toner has an average particle size of 11μ composed of styrene-acrylic resin and carbon black.
A toner for FX-7770 copying machine (manufactured by Fuji Xerox Co., Ltd.) was mixed with a carrier at a concentration of 3% by weight to prepare a developer.

For these developers, the photoconductor speed was 350 mm / sec and the developing magnetic roll (sleeve) speed was 550 mm / sec, and the initial charge amount, solid image density, background stain, fine line reproducibility, and fine line reproducibility on the bench machine for evaluation. The carrier adhesion, the charge amount during running 100,000 sheets, the solid image density, the background stain, the fine line reproducibility, etc. were evaluated, and the high humidity (30 ° C, 80% RH) and low humidity (10 ° C, 30% RH) Tested under environmental conditions. The results are shown in the following table, and the superiority of the carrier according to the present invention was clarified.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Yasuo Matsumura 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Takayoshi Aoki 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Business In-house (56) References JP-A 61-32860 (JP, A) JP-A 61-15157 (JP, A) JP-A 61-9665 (JP, A) JP-A 61-5255 (JP, A) JP 61-9658 (JP, A) JP 59-174857 (JP, A) JP 57-201247 (JP, A)

Claims (1)

[Claims] 1. An average particle size of 20 to 400 obtained by spray-cooling a binder resin containing a polyolefin having a functional group and a melt of a carrier material containing magnetic powder as essential components.
A carrier for a developer, which has a thickness of μm.