JPS6342779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner for electrostatic transfer type copying machines, and more specifically to a type of copying machine in which a toner image formed on a photoreceptor is transferred onto plain paper by electrostatic means. The present invention relates to magnetic toner used in .

An electrostatic transfer copying machine uses, for example, an electrophotographic method to form information such as characters or images to be copied as an electrostatic latent image on a photosensitive drum, and then goes through a development process to visualize this latent image. I try to transfer it onto paper. Magnetic toner is used in such electrostatic transfer copying machines (hereinafter referred to as copying machines).
The properties of this magnetic toner greatly influence the quality of copying (hereinafter referred to as image quality).

The magnetic toner used in the above-mentioned copying machines is conventionally made of uniform resin powder containing a magnetic material, and the resistivity of the resin powder is 10 ⁵
It is known that the resistance is set to an arbitrary value in the range of ~10 ¹² Ω·cm. That is, this conventional magnetic toner utilizes the electrically conductive surface of a uniform resin powder in the development process and the insulating surface in the transfer process.

However, such conventional magnetic toners lack stability because they utilize the contradictory properties of uniform resin powder, electrical conductivity and insulation, and may vary depending on the type of paper and atmospheric humidity. The drawback was that the image quality changed significantly. for example,
Even if exactly the same type of plain paper is used, as atmospheric humidity increases, the conductivity of the paper increases due to moisture absorption, so the contrast will decrease under the same transfer conditions.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of conventional magnetic toners and to provide a magnetic toner for copying machines that has less influence on image quality even when the type of paper or atmospheric humidity changes.

In order to achieve the above object, the present invention consists of a resin powder containing a magnetic material and having a resistivity of 10 ¹¹ Ωcm or more, and this resin powder is composed of two hemispherical parts, one of which is a hemispherical part. Magnetism for an electrostatic transfer copying machine, characterized in that the hemispherical part has stronger magnetism than the other hemispherical part, and the one hemispherical part and the other hemispherical part are charged with opposite polarities. Toner is provided.

To explain one embodiment of the present invention, in FIG. 1, 1 contains a magnetic material and has a resistivity of 10 ¹¹ Ω·cm.
The above is the resin powder. This resin powder 1 is
It consists of two hemispherical parts 2 and 3 of approximately the same size, and one hemispherical part 2 has stronger magnetism than the other hemispherical part 3 so that this hemispherical part faces the magnetic sleeve side. have. One hemispherical portion 2 is charged with a polarity opposite to that of the other hemispherical portion 3 due to friction with the other hemispherical portion of the other resin powder.

The magnetic material acts to attract the resin powder onto the magnetic sleeve during the development process, and is preferably a ferromagnetic material. For example, metals such as manganese, iron, cobalt, nickel, and chromium, metal oxides such as chromium dioxide, iron sesquioxide, and triiron tetroxide, MFe ₃ O ₄ (where M is Mn, Co,
It consists of ferrites (Ni, Mg, Zn, Cd), aluminum alloys and tin alloys whose main components are manganese and copper, and exists in powder form on the surface or inside of the resin powder described below. There is. In addition, the type of magnetic material in the resin powder may be the same in one part and the other part,
It may be different.

Since the resin powder ultimately represents the copied information as a visible image on plain paper, it needs to be able to be fixed by heat or pressure in the fixing step following the transfer step. Substances constituting such resin powders include natural resins such as pulsam resin, rosin, Sierra resin, and Kobal resin, modified resins of these resins, vinyl resins, acrylic resins, olefin resins, polyamide resins, polyester resins, alkyd resins, and phenols. Synthetic resins such as formaldehyde resin, ketone resin, coumaron-indene resin, amino resin, epoxy resin,
Such as natural rubber and various synthetic rubbers. Mixtures of at least two of the above substances, or mixtures of the above substances or mixtures with low-melting substances such as aliphatic waxes, metal salts of fatty acids, and low-molecular compounds of synthetic resins, can also be used. can.

A charge control agent, a conductivity control agent, a coloring agent, a fluidity imparting agent, etc. may be contained inside or on the surface of the resin powder made of such a substance. In addition, the type of resin may be the same in one hemispherical part of the powder and the other hemispherical part,
It may be different.

The resin powder as described above contains a magnetic substance as described above. The content of this magnetic material in the resin powder is arbitrarily determined depending on the magnetic force required in the developing step and the type of magnetic material. The size of these resin powders containing magnetic material is usually 5 to 50 (μ ) is selected as an appropriate value within the range.

The resistivity of such resin powder needs to be 10 ¹¹ Ω·cm or more in order to perform stable transfer. The value of this resistivity is controlled by the type and amount of the resin powder and magnetic material. If necessary, a conductivity modifier can also be used.

The magnetic toner of the present invention is manufactured, for example, as follows.

That is, first, a predetermined melted resin and a predetermined magnetic powder are mixed, cooled, and pulverized.
A resin powder that will become one hemispherical portion is obtained. Then, the outer surface of this resin powder is coated with a mixture of a predetermined molten resin and a predetermined magnetic powder, which will become the other hemispherical part 2, as shown in FIG. A resin powder 4 is obtained whose portion is completely covered with the portion that will become the other hemispherical portion 3.

Next, the resin powder 4 is pulverized into about half as shown by line A--A, heat treated, and then classified to obtain the magnetic toner of the present invention as shown in FIG.

In the above manufacturing process, a charge control agent, a conductivity control agent, etc. may be added to the molten resin as necessary. Further, a fluidizing agent may be added after classification.

Example 1 Epoxy resin “Epicoat” manufactured by Ciel Epoxy Co., Ltd.
1004...50 parts by weight Triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...50 parts by weight was taken, melted at 150°C, kneaded, cooled, and finely pulverized with a hammer mill to obtain a so-called core resin powder, which forms one hemispherical part.

On the other hand, styrene resin “Picoresin” D125 manufactured by Hercules Co., Ltd. in the United States... 15 parts by weight triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...10 parts by weight Orient Chemical Co., Ltd. charge control agent S-34
...2 parts by weight were added to 200 parts by weight of chloroform, and mixed and dispersed in a ball mill for 24 hours.

Next, the core resin powder was added to the dispersion liquid, and while being dispersed with an ultrasonic disperser, it was sprayed and dried with a spray dryer, so that the core resin powder of the former composition was covered with the resin of the latter composition, as shown in FIG. A so-called coated resin powder was obtained.

Next, the coated resin powder was pulverized to about half its size using a jet mill, and further heat-treated at 150°C to obtain a resin powder as shown in FIG. The average particle size of this resin powder is 15μ, and the resistivity is 10 ¹³
It was Ω・cm.

Next, 0.2% by weight of hydrophobized silica R972 manufactured by Nippon Aerosil Co., Ltd. was added as a fluidizing agent to the resin powder, and this and a copying machine SC manufactured by Copia Co., Ltd.
-120 was used to conduct printing tests on plain paper at a temperature of 20°C and various relative humidity. In addition,
In the resin powder, the portion of the former composition is positively charged, and the portion of the latter composition is negatively charged.

As a result of the test, the print density was 1.2 when the humidity was 30%. Even when the humidity was increased to 50%, the print density was still 1.2, and this value did not change even when the humidity was increased to 70%. When the humidity was increased to 85%, the print density decreased slightly to 1.1.

Example 2 When a printing test was performed in the same manner as in Example 1 by changing the paper to insulating plain paper, the printing density was found to be at a relative humidity of 30~30.
There was no change at all in the 85% range, which was 1.2.

Comparative example 1 Triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...70% by weight Styrene resin "Picoresin" D125 manufactured by Hercules, USA ...27% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely pulverized with a hammer mill, and further pulverized with a jet mill to obtain toner particles with an average particle size of 8μ (hereinafter referred to as toner particles A). ) was obtained.

On the other hand, triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...30% by weight Styrene resin "Picoresin" D125 manufactured by Hercules, USA ...67% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely pulverized with a hammer mill, and further pulverized with a jet mill to obtain toner particles with an average particle size of 20μ (hereinafter referred to as toner particles B). ) was obtained.

Next, these toner particles A and toner particles B were mixed so that the toner particles A accounted for 40% by weight, and hydrophobized silica R972 manufactured by Nippon Aerosil Co., Ltd. was added as a fluidizing agent so that the amount became 0.2% by weight. ,
Hereinafter, a printing test was conducted in the same manner as in Example 1.

As a result of the test, the print density was 1.2 when the humidity was 30%, which was the same as in the example. humidity
Even when the humidity was increased to 50%, the print density was still 1.2, but when the humidity reached 70%, it dropped significantly to 0.8, and the print density was 85%.
%, it dropped further to 0.6, indicating that humidity had a large effect on image quality.

Comparative example 2 Triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...50% by weight Styrene resin "Picoresin" D125 manufactured by Hercules, USA ...43% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely ground in a hammer mill, and further ground in a jet mill to obtain magnetic powder containing triiron tetroxide,
A resin powder with an average particle size of 15 μm was obtained, which was made of magnetic powder that did not contain triiron tetroxide.

Next, 0.2% by weight of hydrophobized silica R972 manufactured by Nippon Aerosil Co., Ltd. was added as a fluidizing agent to this resin powder, and a printing test was conducted in the same manner as in Example 1.

As a result of the test, the print density was 1.2 when the humidity was 30%, which was the same as in the example. humidity
Even when the humidity was increased to 50%, the print density was still 1.2, but when the humidity reached 70%, it dropped significantly to 0.8, and the print density was 85%.
%, it dropped further to 0.6, indicating that humidity had a large effect on image quality.

Comparative example 3 Triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...50% by weight Styrene resin “Picoresin” D125 manufactured by Hercules, USA ...43% by weight Carbon Black MA-100 manufactured by Mitsubishi Chemical Industries, Ltd.
...4% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely pulverized with a hammer mill, and further pulverized with a jet mill to obtain toner particles with an average particle size of 8μ (hereinafter referred to as toner particles A). ) was obtained. The resistivity of this toner particle A was 1×10 ¹² Ω·cm.

On the other hand, triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...50% by weight Styrene resin "Picoresin" D125 manufactured by Hercules, USA ...45% by weight Carbon Black MA-100 manufactured by Mitsubishi Chemical Industries, Ltd.
...2% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely pulverized with a hammer mill, and further pulverized with a jet mill to obtain toner particles with an average particle size of 15μ (hereinafter referred to as toner particles B). ) was obtained. The resistivity of this toner particle B was 3×10 ¹³ Ω·cm.

In addition, triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...50% by weight Styrene resin "Picoresin" D125 manufactured by Hercules, USA ...47% by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
...3% by weight, melted and kneaded at 150°C, coarsely pulverized with a hammer mill, and further pulverized with a jet mill to obtain toner particles with an average particle size of 22μ (hereinafter, toner particles C). ) was obtained. The resistivity of this toner particle C was 3×10 ¹³ Ω·cm.

Next, these toner particles A and toner particles B
and toner particles C in the same ratio, and further added hydrophobized silica manufactured by Nippon Aerosil Co., Ltd. as a fluidizing agent.
R972 was added at a concentration of 0.2% by weight, and a printing test was conducted in the same manner as in Example 1.

As a result of the test, the print density was 1.2 when the humidity was 30%, which was the same as in the example. humidity
Even when the humidity was increased to 50%, the print density was still 1.2, but when the humidity reached 70%, it dropped significantly to 0.8, and the print density was 85%.
%, it dropped further to 0.6, indicating that humidity had a large effect on image quality.

Comparative Example 4 Epoxy resin “Epicoat” manufactured by Ciel Epoxy Co., Ltd.
1002...45 parts by weight Triiron tetroxide EPT-1000 manufactured by Toda Kogyo Co., Ltd.
...45 parts by weight Carbon Black MA-100 manufactured by Mitsubishi Chemical Industries, Ltd.
...3 parts by weight of zinc stearate ...2 parts by weight were melted and kneaded at 150°C, and after cooling,
It was finely pulverized with a hammer mill to obtain a resin powder.

On the other hand, styrene acrylic resin "HIMER" SBM manufactured by Sanyo Chemical Industries, Ltd. ...15 parts by weight Glass powder ...10 parts by weight Charge control agent S-34 manufactured by Orient Chemical Co., Ltd.
... Take 2 parts by weight and add this to 200 parts by weight of ligroin,
The mixture was mixed and dispersed in a ball mill for 24 hours.

Next, the resin powder is added to the dispersion liquid, and while being dispersed with an ultrasonic disperser, it is sprayed and dried with a spray dryer to obtain a toner in which the resin powder having the former composition is coated with the resin having the latter composition. Ta.
The average particle size of this toner was 15μ.

Next, 0.2% by weight of hydrophobized silica R972 manufactured by Nippon Aerosil Co., Ltd. was added as a fluidizing agent to the above toner, and a printing test was conducted in the same manner as in Example 1.

As a result of the test, the print density was 1.2 when the humidity was 30%, which was the same as in the example. humidity
Even when the humidity was increased to 50%, the print density was still 1.2, but it decreased to 1.0 when the humidity reached 70%, and significantly decreased to 0.8 when the humidity reached 85%, indicating that humidity had a large effect on image quality.

As explained above, the magnetic toner of the present invention is
It consists of a resin powder that contains a magnetic material and has a resistivity of 10 ¹¹ Ω・cm or more, and this resin powder consists of two hemispherical parts, one hemispherical part having stronger magnetism than the other hemispherical part. , and since these one hemispherical part and the other hemispherical part are charged with opposite polarities, during development, one part with strong magnetism faces the magnetic sleeve and the other part faces the electrostatic latent image surface. Transfer is performed by attracting the charges of the latent image, while the transfer is carried out efficiently by utilizing the high insulating properties of the resin powder, which has a resistivity of 10 ¹¹ Ω·cm or more. Therefore, it is possible to make copies with stable image quality that is less affected by the type of paper and the humidity in the atmosphere.

[Brief explanation of drawings]

FIG. 1 is a model diagram showing one resin powder of the magnetic toner of the present invention, and FIG. 2 is a model diagram for explaining the method of manufacturing the magnetic toner of the present invention. 1: resin powder, 2: one hemispherical part, 3: other hemispherical part.

Claims (1)

[Claims] 1 Consists of resin powder that contains a magnetic material and has a resistivity of 10 ¹¹ Ω・cm or more, and this resin powder consists of two hemispherical parts, one hemispherical part being more magnetic than the other hemispherical part. A magnetic toner for an electrostatic transfer copying machine, characterized in that one hemispherical portion and the other hemispherical portion are strongly charged with opposite polarities.