JPH0222671A - Carrier for developer - Google Patents

Abstract

PURPOSE:To give a large amount of electric charge to a toner and to obtain a carrier for magnetic brush development superior in the life of a developer and high speed developability by incorporating a polyamide resin in a binder resin in an amount 1-70wt.%, preferably, 2-50wt.% in a positively chargeable carrier composed essentially of a binder resin and a magnetic powder dispersed into the resin. CONSTITUTION:The polyamide resin is contained in an amount of 1-70wt.% in the binder resin in the magnetic powder dispersed type carrier composed essentially of the binder resin and the magnetic powder, and the polyamide resin is less than 1wt.%, a sufficient amount of charge cannot be given to the carrier, and an effect of extending the life of the developer becomes poor. If it is >70wt.%, pulverizability at the time of producing the carrier is deteriorated, and melt viscosity at the time of spraying rises remarkably in the case of using a spray cooling type, and granulation becomes difficult, thus permitting the carrier to be increased in the charge amount, enhanced in this line reproducibility, and freed of deterioration in chargeability, solid density, resistance to background stains, thin line reproducibility at the time of repeated uses.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a component of a two-component developer for developing an electrostatic latent image or a magnetic latent image in electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to a magnetic carrier, and more specifically relates to a magnetic material-dispersed carrier.

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 process, a two-component developer is most often used in combination with carrier particles called a carrier in order to impart an appropriate amount of positive or negative electricity to the toner. Various types of developer carriers have been developed and put into practical use.

There are various properties required for carriers, but particularly important properties include appropriate charging properties, impact resistance, abrasion resistance,
This can impair developability, developer life, etc.

Considering the above-mentioned required characteristics, the carriers used in the past still have problems to be improved, and the reality is that no perfect carrier is known. For example, although conductive carriers such as iron oxide powder have excellent solid imaging properties, they have poor fine line reproducibility, and to extend the life of the toner, special charge control agents must be added to the toner. On the other hand, coated insulating carriers have excellent lifespan, fine line reproducibility, etc.
It has the disadvantage of poor solid reproducibility.

In order to improve these drawbacks, a small particle size carrier for magnetic brush development, a so-called carrier for microtoning, in which fine magnetic particles are dispersed in a binder resin, has been proposed and put into practical use. (Refer to Japanese Unexamined Patent Publication No. 54-66134.) Problems to be Solved by the Invention Conventional carriers for microtoning have problems such as adhesion of the carrier to the photoreceptor due to the small particle size and high temperatures caused by magnetic particles liberated on the surface. Also, there are disadvantages such as changes in chargeability at low humidity and difficulty in surface treatment, which makes it impossible to extend the service life in terms of pumping water by coating.

Therefore, an object of the present invention is to solve the above-mentioned problems in carriers containing magnetic fine particles, and to provide a novel magnetic brush developer used for developing electrostatic latent images in electrophotography and electrostatic recording. We are here to provide you with a career.

Another object of the present invention is to provide a carrier for magnetic brush development that imparts a high charge amount to toner and has excellent developer life and high-speed development performance.

Means for Solving the Problems The inventors of the present invention have conducted various studies to improve the drawbacks of the conventional carriers described above, and have found that if a magnetic fine particle dispersed carrier containing a polyamide resin is used, the carrier described above can be improved. The present inventors have discovered that the present invention is effective in improving various required characteristics of the invention, and have completed the present invention.

That is, the present invention provides a positively charged magnetic material-dispersed carrier containing a binder resin and magnetic powder as essential components, in which the binder resin contains 1 to 70% by weight, preferably 2 to 50% by weight of polyamide resin. It is characterized by

Examples of the polyamide resin used in the carrier of the present invention include the following.

Nylon 3, Nylon 4,6, Nylon 5,6, Nylon 6, Nylon 6.6, Nylon 6.7, Nylon 6.
8, nylon 6.9, nylon e, io, nylon 6
．． 6, nylon 6.12, nylon 7, nylon 7.6
, nylon 7.7, nylon 8, nylon 8,6, nylon 8101 nylon 8.12, nylon 8,22, nylon 9, nylon 9,6, nylon 10, nylon 1
0,6, nylon 10,10, nylon 10,12
, nylon 11, nylon 12, nylon 12.18
, nylon 13, nylon 14.18, nylon 18.
Polycondensates and copolymers such as No. 18.

The polyamide resin used in the present invention has a molecular weight of 1iooo or more.

In the present invention, the polyamide resin needs to be in an amount of 1 to 70% by weight, preferably in a range of 2 to 50% by weight, based on the total amount of binder resin in the carrier. When the amount of polyamide resin is less than 1% by weight, it is not possible to impart a sufficient amount of charge to the carrier, and the effect of extending the life of the developer is poor. In addition, if it exceeds 70% by weight, the crushability during carrier production will deteriorate, and in the case of a spray cooling type,
Melt viscosity increases significantly during spraying, making granulation difficult.

In the carrier of the present invention, as the other binder resin component mixed with the polyamide resin, a conventionally commonly used thermoplastic resin is used.

Specifically, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid α- such as dodecyl
Esters of methylene aliphatic monocarboxylic acids; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, and styrene-butadiene copolymer. , styrene-maleic anhydride copolymer.

Furthermore, polyesters, polyurethanes, epoxy resins, modified rosins, paraffins, and waxes can be avoided.

As the magnetic powder, which is the other essential component of the carrier core of the present invention, any commonly used ferromagnetic fine particles can be used. Specifically, triiron tetroxide, γ-iron sesquioxide, various types of Ferrite powder, chromium oxide, various metal powders, etc. are destroyed.

Further, regarding the particle size of the magnetic powder, those used are usually 5 μm or less, particularly 2 μm or less.

The content of magnetic powder is usually 30% of the total amount of carrier.
A range of about 95% by weight, preferably 45 to 90% by weight, gives good results.

In addition to the binder resin, magnetic powder, and polyamide resin, the carrier of the present invention includes a charge control/dispersion improver, a strength reinforcing agent,
A charge control agent, a coupling agent, etc. can also be added inside the carrier core.

The magnetic substance dispersed carrier of the present invention can be produced by various methods. For example, the above-mentioned binder resin component, polyamide resin, magnetic fine particles, and other optional components are kneaded using an hO hot melt mixing device such as a kneader or Banbury;
It can be produced by a method of pulverizing and classifying a mixed material, or a method of spraying or wind atomizing the above-mentioned kneaded material in a heat-molten IIQ state, and cooling and solidifying it with a relatively low-temperature air flow.

The particle size of the carrier of the present invention is determined from the viewpoint of balance between developer life, carrier adhesion to the photoreceptor, and image quality, with an average particle size of 10.
It is appropriate that the thickness be 400 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 electrostatic latent images.

As the toner used with the carrier of the present invention, any toner that has a colorant dispersed in a binder resin and is used in conventional electrophotography can be used.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples in any way.

In addition, in the following examples, "part" represents "11 parts".

Example 1 Magnetite (EPT100O1 manufactured by Toda Kogyo qshu) 70 parts Styrene-methyl methacrylate n-butyl methacrylate copolymer (KTR254, manufactured by Fujigasa Kasei ■) 25 parts Nylon 8 (Cho-8 Nylon manufactured by Unitika ■) 5 parts of the above The components were melt-kneaded using a pressure kneader, and further pulverized and classified using a turbo mill and a classifier to obtain a carrier having an average particle size of 100 μm.

Example 2 Magnetite (EP 1000, manufactured by Toda Kogyo 0 Shu) 70 parts Styrene-methyl methacrylate-n-butyl methacrylate copolymer (KTR254, manufactured by Fujiyu Kasei ■) 25 parts Nylon 6/66/610 terpolymer (CM -400
0, manufactured by Higashi Shizai, I) 5 parts The above ingredients were melt-kneaded using a pressure kneader, and further pulverized and classified using a turbo mill and a classifier to obtain a carrier having an average particle size of 100 μm.

Example 3 Magnetite (EP 1000, manufactured by Toda Kogyo 0) 70 parts Polypropylene wax (550p, Sanyo Chemical! Wooden) 28 parts Nylon 8 (T-8 nylon manufactured by Unitika ■) 2 parts Melt the above ingredients with an attritor After kneading, the mixture was kept at 150'C and sprayed and cooled using a spray dryer while still in the molten state.
A carrier having an average particle size of 100 μm was obtained.

Comparative example 1 Magnetite (EPTlooO.

(manufactured by Toda Kogyo) 70 parts styrene
Methyl methacrylate-n-butyl methacrylate copolymer (KTR254, Fujikura Kasei Oki) 30 parts The above ingredients were kneaded and ground in the same manner as in Example 1, and classified to obtain gearia with an average particle size of 1100 JI. .

Comparative Example 2 70 parts of magnetite (EPT100O1 manufactured by Toda Kogyo ILI) 30 parts of polypropylene wax (550p, manufactured by Sanyo Kasei! 1) The above components were cross-wired and spray-cooled in the same manner as in Example 3, and the average particle size was 100 μm. got a career.

Comparative Test The carriers obtained in Examples 1 and 2 and Comparative Example 1 were mixed with toner and their performance was evaluated. l ~ luna ~ then,
F with an average particle size of 11 μm obtained by melt-kneading styrene-ac 1-nor resin and carbon black, cooling and pulverizing the mixture.
A toner for X-7770 [(Fuji Xerox→Wooden) was used and mixed with a carrier at a ratio such that the opening degree was 5% to form a developer. For these developers, the photoreceptor speed was 350 rMt/sec and the developing magnetic roll was 550 rMt/sec.
Using an evaluation bench machine with a speed of evaluated.

The results are shown in Table 1. In the table, ○ indicates that there is no practical problem, and X indicates that there is a practical problem.

Table 1 Effects of the Invention The developer carrier of the present invention contains a polyamide resin in a binder resin and disperses magnetic powder, as is clear from the above comparison. It has a high charge amount and excellent fine line reproducibility, and there is no deterioration in charge amount, solid density, background stain, fine line reproducibility, etc. even with repeated use over a long period of time. Furthermore, by adjusting the type and amount of the polyamide resin, the chargeability of the carrier can be controlled, resulting in effects such as the ability to significantly extend the life of the carrier and, by extension, the life of the developer.

Claims (1)

[Claims] (1) In a magnetic material-dispersed carrier containing a binder resin and magnetic powder as essential components, the binder resin contains polyamide resin from 1 to
A magnetic material-dispersed carrier characterized by containing 70% by weight.