JPH01239565A - Toner for developing electrostatic image - Google Patents

Abstract

PURPOSE:To prevent decrease of a picture image density by incorporating fine pulverous Fe single crystal having 0.1-10mum mean particle size into a toner. CONSTITUTION:The title toner contains fine pulverous Fe single crystal having 0.1-10, pref. 0.2-5mum mean particle size. The pulverous single crystal of Fe has high dispersibility and stable crystal faces, so oxide is formed scarcely on the surface of the pulverous body and the surface is prevented from rust generation. The Fe powder has an appropriate magnetic characteristic when the content of Fe is 15-40wt.% since the magnetic flux density is high (120-150emu/g saturation magnetic moment). A distinct picture image is obtd. by this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a toner for developing electrostatic images, and more particularly to a magnetic toner that is effective not only for black but also for color applications.

[Prior art]

Development methods used in electrophotography and electrostatic recording methods include (
a) A method using a type of wet developer in which a toner made of a mixture of a colorant and a resin is dispersed in a carrier liquid, and (b)
) A system using a one-component dry developer containing only toner and no solid carrier, or a two-component dry developer comprising toner and a solid carrier is known. These (a)
Both methods (b) have advantages and disadvantages.

In order to obtain a copy in a dry state, (
b) Dry developer is better.

By the way, in a -component type dry developer (hereinafter sometimes referred to as a "-component type developer").

Some are non-magnetic, but most are magnetite,
A magnetic toner is used in which magnetic powder such as ferrite or iron powder 1 alloy powder is mixed into the toner. Furthermore, in two-component dry developers (hereinafter sometimes referred to as "two-component developers"), a magnetic brush method using carrier iron powder is often employed. Recently, the latter two-component developer has become mainstream.

The reason for this is generally explained as follows. That is, roughly speaking, this is because two-component developers are superior in terms of image characteristics. -The image characteristics of component developers are said to be inferior to those of two-component developers because (i) Toners of two-component developers usually have a binder resin of 80% by weight. %, and in a -component developer, the binder resin is usually 30 to 50% by weight, and the remainder is magnetic powder. Therefore, the -component developer (-component toner) has a larger heat capacity and melt viscosity than the toner of the two-component developer, and this -component toner is transferred to a transfer medium (such as paper) by heat or pressure. It tends to be incomplete when it is fixed.

(n) Magnetic oxides such as magnetite and ferrite have poor moisture resistance, and one-component toners containing them tend to electrically leak in humid environments.

However, even with two-component developers, the toner concentration in the developer tends to change, making it difficult to always obtain a constant image quality, and the developer deteriorates after long-term use, so the developer needs to be replaced. There are also drawbacks such as the development mechanism becomes complicated due to the circulation of the developer, and the device becomes large in size.

Under these current circumstances, the development method using one-component toner (-component developer) has a simple development mechanism and is easy to adjust, and the development unit is simple, requiring only additional toner supply. Therefore, maintenance can be greatly reduced, the equipment can be simplified, the weight of the equipment can be reduced, and costs can be reduced. A dramatic development of developers is expected.

By the way, it is preferable for the magnetic powder for -component toner to have a large magnetic flux density with respect to the magnetic field of the magnetic roll of a copying machine, but this is because it increases the height of the ears as a magnetic brush or increases the density of the ears. It is.

Magnetite is currently commonly used as magnetic powder for one-component toner, but in this case, in order to obtain the required magnetic flux density, it is necessary to mix 50 to 70% by weight into the magnetic toner, which is not satisfactory. It's not possible.

In addition, conventional magnetic powders for toner-based toners have poor affinity with resins, and when crushed, they are exposed on the surface and contaminate the toner carrier, resulting in decreased fluidity of the toner, fog, and decreased image density. It is the cause that causes it.

Furthermore, conventional magnetic materials such as magnetite are colored black, brown, etc., and are therefore unsuitable for coloring magnetic toners.

〔the purpose〕

A first object of the present invention is to provide a magnetic toner (-component magnetic toner) containing high-performance magnetic powder. A second object of the present invention is to provide a magnetic toner that exhibits high magnetic properties even when a small amount of magnetic powder is added, and is therefore useful as a color toner. A third object of the present invention is to provide a magnetic toner that has excellent affinity with a binder resin, contains magnetic powder, and has good fixing properties.

〔composition〕

The magnetic toner for developing electrostatic images of the present invention has an average particle diameter of 0.
．． It is characterized by containing single crystal fine powder of iron in the range of 1 to 10 μm, preferably 0.2 to 5 μm.

Incidentally, the present inventors have investigated the magnetic substance (
As a result of intensive study on magnetic powder), we found that the average particle size was 0.1
It has been confirmed that the drawbacks of conventional magnetic toners can be overcome by incorporating iron single crystal fine powder of ~10 μm in diameter. The present invention has been made based on this.

The single crystal fine powder iron powder used in the toner of the present invention has fluidity,
Because it has good dispersibility and stable crystal planes, it is difficult to form oxides on the powder surface and is resistant to rust.

The single crystal fine powder iron powder in the present invention can be produced by the following method. By selecting and controlling the temperature, hydrogen gas flow rate, and other factors during the low-temperature hydrogen reduction process of iron chloride, polyhedral, high-purity single-crystal iron fine powder surrounded by stable crystal planes is produced.

A magnetic toner using such a single-crystal fine powder iron powder achieves the above-mentioned objectives and can also provide stable image quality even in a high temperature and high humidity environment. ' In the past, there were two methods for obtaining fine iron powder: evaporation method and gas phase reduction method. However, in both cases, the fine powders produced have irregular shapes and structures, resulting in problems such as poor fluidity and dispersibility, and easy oxidation.

The content of single crystal fine powder iron powder in the toner of the present invention is as follows:
The magnetic flux density of this iron powder is high (saturation magnetic moment 120
~150 emu/g), appropriate magnetic properties can be obtained at 15 to 40% by weight, and it is also possible to weaken the magnetic force of the magnet in the developing sleeve. In addition, the saturation magnetic moment of conventional magnetic powder (Fe, O4) is 80 to 9
0 emu/g < leprosy.

Further, the average particle diameter of the iron single crystal fine powder in the present invention is 0.
It is preferable that it is 1-10 micrometers. If the diameter is smaller than 0.1 μm, the dispersibility of the fine powder in the resin may tend to decrease, whereas if it is larger than 10 μm, particles of the fine powder alone tend to exist in the toner.

Such single-crystal fine powder iron powder can be used together with materials used in conventionally known electrostatic image developing toners.

Magnetic toner is a colored particle containing a coloring agent together with the single crystal fine iron powder in a binder resin, and in order to impart a more effective charge, a charge imparting substance such as a dye, a pigment, or a so-called charge control agent is added. It may also contain an agent. Furthermore, fluidizing agents such as colloidal silica, abrasives such as cerium oxide and silicon carbide, lubricants such as metal stearate,
A conductivity imparting agent such as tin oxide may be contained as necessary.

In the preparation of magnetic toner, the inclusion of magnetic powder that meets certain conditions is disclosed in JP-A-56-137357, JP-A-57-24950, and JP-A-56-19682.
It is also disclosed in official gazettes such as No. However, these publications do not describe the inclusion of single-crystal fine iron powder as the magnetic powder.

Next, examples will be shown. Note that parts here are based on weight.

Example 1 Carbon black (Mitsubishi #44)
5 parts low molecular weight polypropylene 4
A mixture consisting of 25 parts of single-crystal fine iron powder (average particle size of about 0.5 μm) and 1.5 parts of nigrosine dye was melt-kneaded in a heated roll mill.

After cooling, it is coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer. The obtained fine powder was classified to obtain a toner having a particle size of 5 to 15 μm. A magnetic toner was prepared by stirring 0.3% of colloidal silica in 100 parts of this mixture using a speed kneader. This magnetic toner was heated at 10°C.

15%RH 120℃, 60%RH 130℃, 90%RH
Ricoh's electrophotographic copying machine (Mycopy-M)
-10), and a clear image was obtained. Furthermore, after 10,000 continuous copies, the same clear image as the initial image was obtained.

Comparative Example 1 Average particle size of about 0.5 p instead of 25 parts of single crystal fine powder iron powder
m Fe304 (BL-100 manufactured by Titan Kogyo Co., Ltd.) 65
A magnetic toner was prepared in exactly the same manner as in Example 1 except that a magnetic toner was used, and when it was put into an electrophotographic copying machine manufactured by Ricoh Co., Ltd. (Myrico Copy M-10) and an image was produced, a clear image was obtained. . However, when 1000 copies were made continuously, background stains and fogging occurred on the images. Furthermore, the fixing properties were also insufficient.

Comparative Example 2 Fe with an average particle size of 0.5 μm instead of single crystal fine powder iron powder,
A magnetic toner was prepared in exactly the same manner as in Example 1, except that 25 parts of BL-100 (manufactured by Titanium Kogyo Co., Ltd.) was used, and when the image was produced by putting it in a Ricoh Co., Ltd. Mailicopy M-10, the background was smudged. and fogging occurred.

Example 2 A toner was prepared in the same manner as in Example 1 using a mixture consisting of 5 parts of copper phthalocyanine blue pigment, 4 parts of low molecular weight polypropylene, 22 parts of single crystal fine powder iron powder (average particle diameter of approximately 2 μm), and 10 parts of amino group-containing polymer. When the image was produced by putting it in a Ricoh Co., Ltd. Mailicopy M-10, a clear blue image was obtained.

〔effect〕

By using the magnetic toner of the present invention, colorization is possible.
Moreover, a clear image with good fixation can be obtained.

Claims (1)

[Claims] 1. A toner for developing an electrostatic image, characterized by containing fine single crystal iron powder having an average particle size of 0.1 to 10 μm.