JPH08179549A - Toner for developing magnetic latent image - Google Patents

Abstract

PURPOSE: To provide a toner having satisfactory image properties, sufficiently high fixability even in the case of high-speed printing and satisfactory preservability and preventing the soiling of a head by adding an additive and/or a positive charge controlling agent to a specified toner for developing a magnetic latent image so that the quantity of triboelectric charges is regulated to a specified range. CONSTITUTION: An additive and/or a positive charge controlling agent is added to a toner for developing a magnetic latent image contg. 30-50 pts.wt. binder resin contg. polyester resin having a mol.wt. of 4,000-12,000 and 50-70 pts.wt. magnetic powder contg. tri-iron tetroxide so that the quantity of triboelectric charges is maintained in the range from -5 to +5μC/g. The additive is, e.g. hydrophobic silica or aluminum oxide. The positive charge controlling agent is, e.g. nigrosine, a quat. ammonium compd. or a triphenylmethane dye. The objective toner not soiling a head, stably giving a satisfactory image and not increasing the blurring of characters or fog even after repeated copying is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in electrophotography, electrostatic recording, electrostatic printing, magnetic recording, etc., and more particularly to a magnetic latent image developing toner used in magnetic recording.

[0002]

2. Description of the Related Art As described in JP-A-54-32328, a magnetic recording method uses a magnetic head to write a magnetic latent image on a magnetic drum, which is a recording medium. It is a method of developing with a component toner, transferring, and fixing. In this method, a large number of copies can be obtained by forming a magnetic latent image once, and there is no fatigue of the photoconductor unlike the electrophotographic method, and there is no need to replace the photoconductor for every tens of thousands of copies. It also has the advantage that maintenance is easy.

Recently, a printer that generates less ozone has been desired due to the problem of environmental damage. However, this method produces almost no ozone, and is a method that has recently received special attention. The toner for developing a magnetic latent image used in this method contains a fixing resin to be fixed on the final recording paper and the like, and a magnetic powder satisfying the magnetic characteristics enabling the development of the magnetic latent image and the transportability to the developing site. .

However, in the magnetic recording method, since the magnetic head floats slightly above the surface of the magnetic recording medium for recording, toner adheres to the magnetic head and the floating becomes unstable, and the magnetic recording medium and the magnetic head are separated from each other. The intervals were non-uniform, and the image was likely to deteriorate. Further, in recent years, there has been a growing demand for energy saving and high speed, and there has been a demand for a toner which can be sufficiently fixed even at a low temperature and has a good image property.

[0005]

The problem to be solved by the present invention is that it has a good image quality, has sufficient fixability even in high-speed printing, has good storability, and does not cause head contamination. The present invention relates to providing a latent image developing toner.

[0006]

In order to solve the above problems, the present invention comprises (1) 30 to 50 parts by weight of a binder resin containing a polyester resin having a molecular weight of 4000 to 12000 and (2) iron (III) tetraoxide. A magnetic latent image developing toner containing 50 to 70 parts by weight of a magnetic powder containing the magnetic powder, wherein an external additive and / or a positive charge control agent is added to the magnetic latent image developing toner to reduce the triboelectric charge amount. The present invention relates to a toner for developing a magnetic latent image, which is maintained in a range of 5 to 5 μC / g.

The toner for developing a magnetic latent image according to the present invention will be described in more detail. The binder resin used in the present invention must have sufficient fixing strength even in high-speed printing. Polyester resins are preferred because they have a low softening point and a high cohesive energy density. Further, the polyester resin used in the present invention is particularly preferably a polyester resin having a molecular weight of 4000 to 12000. When the molecular weight is 4000 or less, the storage stability becomes poor and the blocking phenomenon is likely to occur, and when the molecular weight is 12000 or more, the fixability becomes poor and there is a drawback that it cannot be used for a short time fixing as a high speed printer. .

The binder resin used in the present invention may contain a styrene acrylic resin or the like in order to improve image quality, storability and fixability. The proportion of the polyester resin in the binder resin used in the present invention is preferably 70 to 100% by weight. These resins are used in the range of 30 to 50 parts by weight. By using a binder resin containing a polyester resin, not only sufficient fixability is imparted, but also the phenomenon of migrating to a polyvinyl chloride film and contaminating the film unlike styrene acrylic resin does not occur. Also, unlike epoxy resins, it does not contain carcinogens and is environmentally superior.

The magnetic powder used in the present invention includes Ni,
Zn, Cu, Co, Fe, Mg, ferrite Fe, C
Ferroelectric metal powder such as o and Ni, magnetite, γ-
Examples include metal compounds such as fematite. The ratio of the magnetic powder in the toner for developing a magnetic latent image of the present invention is preferably 50 to 70 parts by weight. If the ratio of the magnetic powder is less than 50 parts by weight, the magnetic force of the toner becomes weak, the toner transportability is deteriorated, and the fog tends to increase, which is not preferable. Again 7
When the amount is more than 0 parts by weight, the fixing property is deteriorated, which is not preferable.

Further, since the magnetic head floats slightly above the surface of the magnetic recording medium for recording, when the frictional charge of the toner is large, the toner adheres to the magnetic head and the floating becomes unstable, and the magnetic recording medium There is a drawback that the gap with the magnetic head becomes non-uniform and the image quality is deteriorated.

Therefore, it is necessary that the triboelectric charge amount of the magnetic latent image developing toner is in the range of -5 to 5 μC / g in order to improve the above-mentioned drawbacks. In order to adjust the triboelectric charge amount, an external additive and / or a positive charge control agent can be added to a specific magnetic latent image developing toner for adjustment.

In the present invention, as the external additive, for example, hydrophobic silica "RA200H" manufactured by Nippon Aerosil Co., Ltd. or "HDKH2050EP", "HD manufactured by Wacker Chemicals East Asia Co., Ltd."
Examples of the aluminum oxide include "RFY-C" manufactured by Nippon Aerosil Co., Ltd., and examples of titanium oxide include "T-805" manufactured by Nippon Aerosil Co., Ltd.

It is also possible to control at -5 to 5 μC / g by using a known positive charge control agent or in combination. In the present application, examples of the positive charge control agent include nigrosine, quaternary ammonium compounds, and triphenylmethane dyes. Examples of commercially available positive charge control agents include "Bontron N-" manufactured by Orient Chemical Co., Ltd.
01 "," Bontron N-04 "," Copy Blue PR "manufactured by Hoechst Japan KK, and the like.

In the present invention, a wax may be contained in order to improve offset and fixability. As the wax that can be used in the present invention, a polyolefin wax such as polyethylene wax or polypropylene wax can be used. As polyethylene wax, "High Wax NL-500" manufactured by Mitsui Petrochemical Industry Co., Ltd.
(Softening point 110 ° C.) and the like can be used, and as the polypropylene wax, “High Wax NP055” (softening point 136 ° C.) manufactured by Mitsui Petrochemical Co., Ltd. and the like can be used. Further, carbon black or other dyes and pigments can be used as the colorant, and can also serve as an electric resistance adjusting agent.

[0015]

EXAMPLES The present invention will be described with reference to the following examples, which are not intended to limit the scope of the present invention. Example 1 MTA-740 250 parts by weight (Toda Kogyo ferrosoferric oxide) FC-051 120 parts by weight (Mitsubishi Rayon polyester resin) (Molecular weight 5600) High wax NL-500 10 parts by weight (Mitsui Petrochemical Polyethylene) Wax) The above components were mixed, melted and kneaded, cooled to room temperature, coarsely crushed and mediumly crushed, then finely crushed by a jet mill and classified to obtain a magnetic toner having an average particle diameter of 9 microns. [R
FY-C] (aluminum oxide manufactured by Nippon Aerosil Co., Ltd.) 0.3 part by weight was externally added and mixed to obtain a toner for developing a magnetic latent image of Example 1. The triboelectric charge amount at this time is -1.6.
It was μC / g.

Comparative Example 1 A magnetic latent image of Comparative Example 1 was prepared in the same manner as in Example 1 except that 0.7% of [R972D] (hydrophobic silica manufactured by Nippon Aerosil Co., Ltd.) was externally added to the external additive. A developing toner was obtained. The triboelectric charge amount at this time was -10.3 μC / g.

Example 2 0.8% of [HDKH2050EP] (hydrophobic silica manufactured by Wacker Chemicals East Asia Co., Ltd.) was used as an external additive.
A toner for developing a magnetic latent image of Example 2 was obtained in the same manner as in Example 1 except that external mixing was performed. The triboelectric charge amount at this time was +0.1 μC / g.

Comparative Example 2 A magnetic latent image of Comparative Example 2 was prepared in the same manner as in Example 1 except that 0.2% of [R976D] (hydrophobic silica manufactured by Nippon Aerosil Co., Ltd.) was externally added to the external additive. A developing toner was obtained. The triboelectric charge amount at this time was -7.5 μC / g.

Example 3 EPT-500 250 parts by weight (Toda Kogyo ferrosoferric oxide) FC-150 120 parts by weight (Mitsubishi Rayon polyester resin) (Molecular weight 7800) Heimer TB1000F 10 parts by weight (Sanyo Chemical Co., Ltd. styrene acrylic) Resin) High Wax NP051 10 parts by weight (Polypropylene wax manufactured by Mitsui Petrochemical Industry Co., Ltd.) Bontron N-01 4 parts by weight (Positive charge control agent manufactured by Orient Chemical Co., Ltd.) Example 1 was repeated except that the above components were used. No. 3 magnetic latent image developing toner was manufactured. The triboelectric charge amount at this time was +1.4 μC / g.

Comparative Example 3 A magnetic latent image of Comparative Example 3 was prepared in the same manner as in Example 3 except that 0.7% of [R972D] (hydrophobic silica manufactured by Nippon Aerosil Co., Ltd.) was externally added to the external additive. A developing toner was obtained. The triboelectric charge amount at this time was -7.3 μC / g.

Example 4 KBC-100S 200 parts by weight (Kanto Denka Kogyo ferrosoferric oxide) FC-150 120 parts by weight (Mitsubishi Rayon polyester resin) (Molecular weight 7800) FC-344 30 parts by weight (Mitsubishi Rayon polyester) Resin) High wax NP-055 10 parts by weight (Polypropylene wax manufactured by Mitsui Petrochemical Industry) Bontron N-04 8 parts by weight (Positive charge control agent manufactured by Orient Chemical Co., Ltd.) Performed in the same manner as in Example 1 except that the above components were used. The magnetic latent image developing toner of Example 4 was produced. The triboelectric charge amount at this time was +4.2 μC / g.

Comparative Example 4 0.8% of [HDKH2050EP] (hydrophobic silica manufactured by Wacker Chemicals East Asia Co., Ltd.) was used as an external additive.
A magnetic latent image developing toner of Comparative Example 4 was obtained in the same manner as in Example 4 except that external mixing was performed. The triboelectric charge amount at this time was +5.9 μC / g.

Next, MG-800 manufactured by Iwasaki Tsushinki Co., Ltd.
An image output of the toner for magnetic latent image development obtained in each of the above Examples and Comparative Examples was performed using a 0 type printer. The results are shown in Table-1. The evaluation method is as follows. 1) Image Density A Macbeth reflection densitometer RD-918 (manufactured by Sakata Shokai) was used to measure a solid density of 1 cm × 1 cm. 2) Amount of triboelectric charge 100 parts by weight of surface iron oxide powder (TEFV manufactured by Powder Tech Co., Ltd.) having a particle size of 200 to 300 mesh and 3 parts by weight of each toner for developing a magnetic latent image are used in a 100 ml glass container for 10 minutes. The mixture was mixed for a minute and measured with a blow-off charge amount measuring device manufactured by Toshiba Chemical Co. 3) Head dirt 1 with the MG-8000 type printer manufactured by Iwasaki Tsushinki Co., Ltd.
One copy of recording was repeated 5000 times, and the adhesion of the toner to the magnetic head at that time was evaluated. ○ There is no dirt on the head or very little dirt. △ Toner adheres to the head. × Toner adheres to the head, and the image is faded during recording.

[0024]

[Table 1]

As shown in the table, the triboelectric charge amount is -5 to 5 μm.
It can be seen that in the range of C / g, there is no particular head stain and a stable and good image can be obtained. The toner for developing a magnetic latent image obtained in each of the examples does not increase dust of letters and fogging even after repeated copying, and a good image is obtained, and sufficient fixing property is obtained.

[0026]

According to the present invention, it is possible to provide a stable and good image having good imageability, sufficient fixability even at high-speed printing, good storability, and no head stain.

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Claims (1)

[Claims] 1. A toner for developing a magnetic latent image, comprising 30 to 50 parts by weight of a binder resin containing a polyester resin having a molecular weight of 4000 to 12000 and 50 to 70 parts by weight of magnetic powder containing triiron trioxide. By adding an external additive and / or a positive charge control agent to the magnetic latent image developing toner, the triboelectrification amount thereof is in the range of -5 to 5 μC / g. toner.