JPS5918953A - Pressure fixable magnetic toner particle - Google Patents

Abstract

PURPOSE:To obtain a magnetic toner supeior in fixability and improved in resistance to blocking, by mixing a wax having functional groups and a vinyl type copolymer each having a specified mol.wt. range, and a softening point not below a specified temp., in a specified proportion and using the resulting mixture as a binder. CONSTITUTION:The present magnetic toner uses a binder consisting of a wax having 300-2,000mol.wt., and >=70 deg.C softening point, and functional groups, such as COOH or CONH2 and of a vinyl type copolymer, such as ethylene-vinyl acetate copolymer, having 1,000-8,000mol.wt. and >=90 deg.C softening point, mixed in a 3:7-7:3 mixing ratio. As a result, the obtained toner is good in dispersiblity of magnetic particles, superior in pressure fixability, and improved in blocking resistance, and it can form a sharp image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes magnetic toner particles with excellent pressure fixability for use in magnetic brush development of electrostatically charged latent images.

Conventionally, two-component developers have been widely used as developers for magnetic brush development of electrostatic $# latent images formed on the surface of photoreceptors in electrophotographic copying machines. This consists of a magnetic powder called a carrier and a colored resin powder called a toner. By mixing the two together, they are triboelectrically charged, and only the toner is electrostatically deposited on the photoconductor. In this method, toner particles are transferred to a transfer material such as paper and then fixed.

However, this two-component developer requires a mixing mechanism to mix the carrier and toner and a supply mechanism to periodically replenish the toner, making the structure complicated as a magnetic brush developing unit. Inevitably, we had to make it bigger. Furthermore, it has been pointed out that there is a maintenance problem in that a spent phenomenon occurs in which toner adheres to the surface of the carrier during copying, and the carrier must be replaced periodically.

On the other hand, magnetic toner, which has been put into practical use in recent years and is rapidly becoming popular, contains magnetic powder in its toner particles and therefore does not require a carrier, and thus has no drawbacks of the two-component toner described above.

In addition, the conventional method for fixing toner images has been to melt the toner in a heating bath using a heater or heat roll and fix it on the support, but this method consumes a lot of power and takes a long lead time to reach a certain temperature. It has disadvantages such as long length and fire danger.

On the other hand, in recent years, the pressure byssus method, in which the toner-supported image is fixed by passing it through a pressurized roller, has been attracting attention as a method that compensates for the drawbacks of heat-melting standard books.

However, the mechanism of this fixing method using pressure fixing is largely dependent on the mechanical adhesion between the toner particles and the support, and its fixing performance varies greatly depending on the surface properties of the support, and moreover, it is less effective than heat fixing methods. The adhesion force is weak, and toner particles easily peel off from the support even after fixing.
It has been pointed out that the so-called retention is poor.

In view of these circumstances, the present inventors have conducted intensive studies and have discovered that by selecting a plum fat component, it is possible to obtain a magnetic toner with extremely excellent pressure byssus properties. It is something that

That is, the present invention provides magnetic toner particles consisting of at least a resin and a magnetic powder, in which the resin component is a wax containing a functional group having a molecular weight of 300 to 2,000 and a softening point of 70 or more, and a wax having a molecular weight of 1,000 to 8,000. Softening point is 9
The present invention provides magnetic toner particles which are made of a vinyl copolymer having a temperature of 0° C. or higher and have excellent pressure fixability, characterized in that the ratio of both resin components is from 3 to 7:3.

Polyolefin resins have traditionally been used as resins for pressure fixing toners, but generally those with a molecular weight of 2
000 to 5000 were used. This is because when the molecular weight is less than 2,000, the fixing properties are good, but the softening point is low and the cohesiveness is strong, and when used as a toner, blocking occurs and significant defects occur on the image. Also,
If the molecular weight exceeds 5,000, sticking properties are improved, but the resin becomes hard and elastically deforms, which has a significant negative effect on fixing properties. For this purpose, a method of blending various thermoplastic resins as modifiers has been proposed, but the image quality (developability)
At present, no product has been obtained that is fully satisfactory in terms of overall properties including storage stability.

The cause of this is not clear, but polyolefin resins
Compatibility with other resins is not very good ~ Even when blended with other resins, microscopically, on the surface of toner particles,
A part with a large amount of polyolefin resin and a part with a large amount of other resins are mixed, and the physical properties of the toner tend to be unbalanced, such as the bad aspects of each resin tend to come out, and when the fixing property is good, the sticking property is bad. The reality is that it has not been much improved.

In contrast, according to the present invention, by using a mixed resin system that is a blend of a wax having a functional group and a vinyl copolymer as a conventional polyolefin resin, it has excellent fixing properties and magnetic properties with good blocking properties. Toner particles could be obtained.

Typical examples of waxes with functional groups include those based on saturated linear fatty acids such as montanic acid and stearic acid, saturated fatty acid amide yarns (7) such as palmitic acid amide, and bis fatty acid amide yarns. can give. The molecular weight of wax having these functional groups is 30
0 to 2000 is preferred. If the molecular weight is less than 300, the cohesiveness cannot be improved even if a vinyl copolymer is blended, and if the molecular weight is more than 2000, the fixing property,
Dispersibility with other resins deteriorates, making it impossible to obtain good toner properties.

The softening point is preferably 70C or higher in order to ensure storage stability.

Examples of vinyl copolymers include ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, propylene-vinyl acetate copolymer, pentene-vinyl acetate copolymer, ethylene-propylene-acid-resistant vinyl copolymer, and ethylene-vinyl acetate copolymer. Vinyl acetate-vinyl methyl ether copolymer etc. are used.b The molecular weight of these vinyl copolymers is 10.
00-8000, preferably 2000-5000. If the molecular weight is less than 1000, blending with a wax having a functional group will not improve cohesiveness;
If it exceeds 8,000, the compatibility and fixing properties will not be adversely affected. As for the softening point, it is preferable to blend materials with a softening point of 90C or higher in order to ensure storage stability.

The proportion of the vinyl monomer in the copolymer is preferably 5 to 40% (car rat) in consideration of the balance between fixing properties and cohesive properties.

Further, the mixing ratio of the wax having a functional group and the vinyl copolymer is preferably from 3 to 7:3. This was decided based on the balance between the waxes having functional groups, which mainly contribute to regularity, and the vinyl copolymer, which mainly contributes to improving fluidity.

The magnetic toner of the present invention requires magnetic fine particles, but any magnetic substance may be used, for example, metals such as iron, cobalt, nickel, alloy powders, and metals such as magnetite. Oxide magnetic powder or the like is used.

The average particle size of these magnetic fine particles is about 0.01 to 5 μm, more preferably tJ, o, or 2 to 2 μm. The amount of magnetic fine particles contained in the toner is 25~
It is determined by the conditions of the magnetic brush development system within a range of 70% by weight.

Furthermore, various substances can be added to the magnetic toner used in the present invention for the purpose of coloring, electrical resistance, and charge control. That is, they include nigrosine or metal-containing dyes, carbon black, fine metal powder, and the like.

Furthermore, it is also possible to use finely powdered silica or the like as a fluidity improver.

This will be explained in detail below using examples.

Example 1 Methylene bisstearamide (Nippon Kasei Bisamide Tsuta Molecule [i:580
, softening point 1aOc), ethylene vinyl acetate copolymer (AC40 manufactured by Allied Chemical, molecular weight 3500, softening point 95C) as the vinyl copolymer, Mitsubishi Kasei Su50 as the carbon black, KBOI manufactured by Kanto Denka as the magnetic powder.
Using OQ, seven samples of magnetic toner particles having the above composition were obtained. The toner was prepared by sufficiently dry mixing the raw materials, then sufficiently kneading the raw materials with each other using a well-known heating kneader, cooling and solidifying the powder, and forming particles with a diameter of 50 μm or less using a well-known pulverizer.

Next, the pulverized powder was atomized in a hot air stream of 200C and subjected to a spheroidizing treatment, followed by adding 3.0% of carbon black of the same size to each spheroidized powder and thoroughly drying it. The mixture was mixed and passed through a hot air stream of 180C again in atomized form to fix the carbon black on the surface of the toner particles.Finally, the particles were classified into particles having a diameter of 10 to 44μ to obtain magnetic toner particles.

The magnetic toner particles obtained in this way were
Image evaluation was performed using an o-type copying machine M215.

As a result, the A1 toner, which does not contain a vinyl copolymer, had extremely strong cohesiveness, causing toner blocking in the developing machine and white streaks on the image. Also A
In the toner samples 2 to 7, good images without white streaks could be obtained, but in the toner images of A6 and size 7, a problem occurred in terms of fixability that was considered practical.

In addition, when we conducted a storage test of these toners, we found that
Blocking occurred in the Am and A2 toners when the toners were left for 48 hours under 6op, go%xHfM conditions, but no blocking was observed in the other toners.

A5) The residual rate of the toner was measured by peeling the toner onto zinc oxide paper using cellophane tape and was found to be 83%. This is about 2 times higher than the fixing performance of a prototype toner with A5 composition using polyethylene wax without functional groups (Hechist Wax PE520) instead of wax with functional groups.
It was double that.

Example 2 0.5% by weight of carbon black was added to the A5 spheroidized powder in Example 1, mixed well, and passed through a hot air stream of 150 C to fix the carbon black on the toner particle surface. Furthermore, for the purpose of improving fluidity, 0.3% of finely powdered silica (R200 manufactured by Nippon Aerosil Co., Ltd.) was added, and finally magnetic toner particles having a diameter of 10 to 25 μm were obtained.

When the image of this magnetic toner particle was evaluated using a PRI type photoreceptor (5F730 manufactured by Sharp Corporation) using a ZnO photoreceptor, a very clear image was obtained.

Further, the residual rate of the toner on the paper was 55% when evaluated for peeling with cellophane tape. This value was approximately twice the fixing property of a toner produced experimentally using polyethylene wax (Hethyst Wax PIn520) having no functional group instead of wax having a functional group in A5 introduction.

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Claims (1)

[Claims] 1. In magnetic toner particles for pressure fixing consisting of at least a resin and a magnetic powder, the resin component has a molecular weight of 300-2000. Wax having a functional group with a softening point of 70C or higher and a molecular weight of 1000 to 8000 and a softening point of 9
Magnetic toner particles for pressure fixing, comprising a vinyl copolymer having a carbon content of 0 C or more, wherein the ratio of wax to vinyl copolymer is from 3 to 7:3 by weight.