JPH03197966A - Magnetic toner - Google Patents

Abstract

PURPOSE:To prevent the formation of nonmagnetic particles or weakly magnetic particles even in the case of a reduced particle size and reduced magnetic force of a magnetic toner and to obtain a high-quality image by incorporating a specified amt. of powder of an iron oxide type magnetic material having a specified average particles size. CONSTITUTION:When a magnetic toner contg. a binding resin and powder of a magnetic material is produced, one or more kinds of iron oxide type magnetic materials such as Fe3O4 and Fe2O3 are used as the magnetic material. Fe3O4 is desirably used from the viewpoint of magnetic characteristics and hue. The average particle size of the powder is regulated to 0.03-0.1mum and the content to 10-45wt.%. Even in the case where the magnetic force and particle size of the magnetic toner are reduced, the formation of nonmagnetic particles or weakly magnetic particles is prevented and a high-quality image free from ground fog can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic toner used for developing electrostatic latent images in electrophotography, electrostatic recording, etc. or magnetic latent images in magnetic recording.

(Prior art) In image forming methods using electrophotography and electrostatic recording,
The electrostatic latent image formed on the surface of a photoconductor or dielectric material is developed with magnetic toner and then directly fixed, or the toner image is transferred onto a transfer sheet such as plain paper and then fixed to form the final image. It has gained. Magnetic toners are also used to develop magnetic latent images formed on magnetic recording media.

Various methods have been proposed as developing methods using magnetic toner. For example, Japanese Patent Publication No. 56-2705,
Conductive magnetic toner is held on a sleeve that has a magnet roll inside and is made of a conductive material, and charges of opposite polarity to the electrostatic latent image induced on the sleeve by the charge of the electrostatic latent image are transferred to the toner brush. It is disclosed that magnetic toner is collected at the tip and attached to the electrostatic latent image surface. However, when a conductive magnetic toner is used, the transferred image becomes unclear if it is used in a so-called ppc method that includes a transfer process because the magnetic toner has a low electrical resistance.

Therefore, a developing method using an insulating magnetic toner with increased resistance of the Mi-based toner has been proposed. This patent discloses a method of using insulating magnetic toner to which conductive particles are attached, repeatedly bringing the magnetic toner into contact with an electrode by rotating a sleeve at high speed, and injecting charge from the electrode into the magnetic toner. However, such non-charged magnetic toner has a drawback in that the magnetic toner is generally not charged even if a developing method is devised.

Therefore, JP-A-55-48754 and JP-A-57-4555
A method of triboelectrically charging a 1Mi toner by contacting it with a sleeve, a doctor blade, etc., using a charged magnetic toner prepared by adding a charge control agent to the magnetic toner disclosed in Publication No. 5, etc., has been proposed and put into practical use. ing. This charged type magnetic toner is used not only in the magnetic brush development method but also in the jumping development method (see, for example, Japanese Patent Publication No. 5832375).

As described above, there are various kinds of magnetic toners, but they all have one thing in common: a binder resin and magnetic particles are essential components. As magnetic particles, which are one of the essential components, 2
For example, as described in JP-A No. 50-45639, ferromagnetic materials with an average particle size of about 0.1 to 1 μm, i.e. iron oxides such as Fe30a+ r -F+403, Mn-Zn ferrite Ni- Ferrite powder such as Zn ferrite + ferromagnetic metal such as N+ and Co or alloy powder thereof are used.

However, 1. Among these magnetic fine particles, Fe3O4 with an average particle size of 0.2 to 0.6 μm is usually used in order to facilitate dispersion in the magnetic toner and from the viewpoint of magnetic properties and hue. There is. Examples of these include average particle size 0.0
5-0.2. Containing 50 to 85% by weight of c+m iron oxide (FeJaFez03) (Japanese Patent Publication No. 53-2165
6), those containing 100 to 1000 metal fine powders as magnetic powder (see JP-A-58-83858), and those containing magnetite coated with a surfactant with an average particle size of 300 Å or less. (Unexamined Japanese Patent Publication No. 1-26
(see Publication No. 9946).

[Problem to be solved by the invention]

In the above-mentioned magnetic toner, in order to obtain an image with high two-image density and less blurring, the particle size distribution is generally adjusted to have an average particle size of 9 to 13 μm. However, recently, the demand for higher image quality has increased.
In order to meet this demand, there is a trend toward smaller particle sizes of magnetic toners.

In addition, in a charged magnetic toner, when the amount of magnetic powder increases, the charge retention ability of the toner decreases, or the magnetic adsorption force to the magnetic conveying means increases, resulting in a decrease in developability. Therefore, in order to provide sufficient unidirectional charge retention ability, it is necessary to reduce the amount of magnetic powder in the toner.

However, most of the magnetite currently used as magnetic powder has an average particle size of 0.2 to 0.6 μm, and usually also contains secondary agglomerated particles. Therefore, when a magnetic toner with a small particle size is produced using such magnetite, non-magnetic particles called so-called empty beads that do not contain magnetite or weakly magnetic particles with an extremely small magnetite content are used. The rate at which is formed increases.

Furthermore, when producing magnetic toner, the raw materials are usually heated, kneaded, cooled, and then pulverized, but if the amount of magnetic powder is small, the magnetite may not be uniformly dispersed. This is the cause of the appearance of non-magnetic particles or weakly magnetic particles as described above when the magnetic toner has a small particle size.

When developing with magnetic toner containing non-magnetic particles or weakly magnetic particles as described above, toner scattering causes contamination of the developing device and the environment, and the image quality is significantly reduced, resulting in images with a lot of ground blur, dust, black spots, etc. There is a problem.

The present invention solves the problems existing in the above-mentioned prior art, and provides magnetic properties that allow high-quality images to be obtained without forming non-magnetic particles and/or weakly magnetic particles even when the particle size is reduced and magnetic force is reduced. The purpose is to provide toner.

[Means to solve the problem]

In order to achieve the above object, two aspects of the present invention include a magnetic toner containing a binder resin and a magnetic material powder, in which the magnetic material powder is made of an iron oxide-based magnetic material with an average particle size of 0.03.
~0.1 μm, and the content is 10 to 45% by weight. A technical method was adopted.

The iron oxide magnetic material powder in the present invention is F
ezOn+ Fe2O3+ r −Fe2O3+ n
Mo-FezO3 (However.

M is one or more of Ba, Sr, pb, n
One or more types of iron oxide-based magnetic material powders of =5 to 6) can be used. Note that among the above materials, FI3304 is preferable in terms of magnetic properties and one hue.

In the present invention, the average particle size of the magnetic material powder is 0.03 μm
If it is less than this, it is disadvantageous because it causes aggregation and the state of dispersion in the binder resin becomes non-uniform. On the other hand, the average particle size is 0.1
If it exceeds .mu.m, non-magnetic particles or weakly magnetic particles will appear in the case of a small-sized magnetic toner, which is not preferable.

Next, the content of the iron oxide magnetic material powder as described above is 1
If it is less than 0% by weight, the fixing properties will be improved, but the magnetic force of the magnetic toner will be reduced.

This is inconvenient because it separates from the surface of the developing roll in the developing area, smearing the image due to ground force blur, and also causing toner scattering. On the other hand, if the above content exceeds 45% by weight,
This is not preferable because the adsorption force to the surface of the developing roll becomes large, which prevents smooth transfer to the image carrier side in the developing area, lowers the developing performance, and impairs the fixing performance in the subsequent stage.

As the binder resin in the present invention, a known resin for toner can be used, but basically it is determined according to the fixing method. For example, when the fixing method is a heating constant tr method,
Styrenes, vinyl esters, esters of α-methylene aliphatic monocarboxylic acids, acrylonitrile, methacrylate trile.

A homopolymer obtained by polymerizing monomers such as acrylamide, vinyl ethers, and N-vinyl compounds, a copolymer obtained by copolymerizing a combination of two or more of these monomers, or a mixture thereof may be used.

It is also possible to use non-vinyl resins such as non-vinyl thermoplastic resins such as polyester resin, rosin-modified phenol-formalin resin, oil-modified epoxy resin, cellulose resin, and polyether resin, or mixtures thereof with the above-mentioned vinyl resins.

Particularly, in the case of a non-contact heat fixing method based on an order, a bisphenol type epoxy resin is preferable, and in the case of a contact heat fixing method using a hot roll, a styrene resin or a polyester resin is preferable. The greater the styrene component in the styrene-based resin, the better the releasability from hot rolls. In order to further improve the mold releasability against hot rolls, it is effective to add fatty acid metal salts, low molecular weight polyolefins, and natural or synthetic paraffins.

In addition, in the case of the pressure fixing method, waxes, rosin derivatives, alkyds, epoxy-modified phenolic resins, silicone resins, acrylic acid or methacrylic acid, and long-chain alkyl methacrylates.

Copolymerized oligomer polyolefin with long-chain alkyl acrylate, ethylene/vinyl acetate copolymer.

Ethylene-vinyl alkyl ether co-M combination! =A water-mamaleic acid copolymer is used.

These resins can be arbitrarily selected and mixed as desired, but in order not to reduce the fluidity when used as a toner, resins with a glass transition point exceeding 40°C or resin mixtures are effective. used.

In the present invention, various materials such as colorants and charge control agents can be used as necessary.

As the coloring agent, for example, pigments or dyes such as carbon fluorine blue, calco oil blue, chrome yellow, quinoline yellow, DuPont oil red, malachite green oxalate, lamp black, rose bengal, and nigrosine dye can be used.

As the charge control agent, for example, fatty acid-modified nigrosine dyes, triphenylmethane dyes, metal-containing azo dyes, etc. can be used.

Furthermore, fine inorganic powders such as hydrophobic silica, alumina, and titanium dioxide, fine resin powders such as polytetrafluoroethylene and polystyrene, etc. may be added to the magnetic toner of the present invention, if necessary.

As mentioned above. The amounts of the various materials other than the iron oxide magnetic material powder and the binder resin may be determined depending on the electrical properties required of the magnetic toner.

Generally, it is desirable that the content be 10% by weight or less.

The magnetic toner of the present invention can be produced by a known method such as a pulverization method, a spray drying method, or a suspension polymerization method. For example, when using the pulverization method, raw materials such as a binder resin and iron oxide magnetic material powder are premixed, heated, kneaded, cooled and solidified, and then pulverized so that the average particle size is 6 to 15 μm. Classify.

The magnetic toner of the present invention can be used as a first-order developer without using carrier particles, or can be mixed with a magnetic carrier such as a 9-ferrite carrier to form a second-order developer (for example, as disclosed in JP-A-59-182464). (see) can also be used.

〔Example〕

Styrene-n-butyl methacrylate copolymer (Mw-
250,000, Mn = 35,000) and magnetite were mixed as shown in the table, and 3 parts by weight of polypropylene (Viscol 550P manufactured by Sanyo Chemical Co., Ltd.) and 2 parts by weight of a charge control agent (Bontron N-03 manufactured by Orient Chemical Co., Ltd.) were added. In addition, dry premix with a super mixer, melt knead with a heated niegu,
After cooling and solidifying, it is pulverized with a jet mill and classified into 2 to obtain an average particle size of 1.
The magnetic toner had a diameter of .mu.m.

The table shows the image evaluation results when the average particle size of magnetite and the content in the magnetic toner were changed.

The developing and fixing conditions are as follows. That is,
Inside a SUS 304 sleeve with an outer diameter of 31 mm.

An electrostatic latent image (surface potential -
600V to -400V). The distance between the photoreceptor and the sleeve is 0.4 mm, the toner regulation thickness is 0.35 mm, and the sleeve is placed 20 mm in the same direction as the photoreceptor in the developing section.
Or, p, m, and the VA stone was rotated at 900 r, p, w in the opposite direction to the sleeve. The developed toner image was corona-transferred onto plain paper and fixed with a hot roll. Fixing is performed using a heating roll whose surface is coated with PFA resin and a pressure roll made of silicone rubber, at a fixing temperature of 1.
The fixing pressure was set at 80°C9 with a linear pressure of 1.0 kg/cm.

Some occurrence of soil buri and sunspots is observed. Furthermore, on floor 9, the image density has significantly decreased. On the other hand, floors 2-4. At Ik7 and Ik8, the image density shows a high value, and no ground blurring or black spots are observed.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
Even when the magnetic toner is made to have a lower magnetic force and a smaller particle size, the formation of non-magnetic particles and/or weakly magnetic particles as experienced in the past is extremely rare, and high-quality images without blurring can be obtained. It has the effect of being able to

(Note) O: Good Δ: Slightly poor ×: Poor As is clear from the table, the average particle size of magnetite in Inhibition 1 is small, so the ability to entrain into the binder resin decreases and the dispersion state deteriorates. This results in non-uniformity and low image density, as well as the occurrence of ground blur and black spots. In stone 5, the image density is good.

Claims (1)

[Claims] In a magnetic toner containing a binder resin and a magnetic material powder, the magnetic material powder is formed from an iron oxide-based magnetic material to have an average particle size of 0.03 to 0.1 μm, and the content thereof is 10 μm.
A magnetic toner characterized in that the content is 45% by weight.