JPH10288857A - Magnetic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magnetic toner superior in stability against environment, reproduction performance of a highly precise image and fixability by incorporating a binder resin and a black magnetite obtained by an ion electrolytic separation method. SOLUTION: The magnetic toner contains the binder resin and the black magnetite obtained by the ion electrolytic separation method. It is preferable that the magnetite has a specific surface area of 20-40 m<2> /g. Since the magnetite obtained by this method has a grain diameter of 20-60 μm, the distance between each grain when dispersed into the binder resin is widened to enhance its electric resistance. Since the corners of the magnetite grains are round, the grains are lowered in tendency to scratch the surface of the photoreceptor. The binder resin to be used is embodied by a polystyrene, a styrene-ethyl or n-butyl acrylate copolymer, a styrene methyl methacrylate copolymer, and the like, each alone or mixed with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used in an electrostatic recording method, an electrophotographic method and the like, and more particularly to a magnetic toner containing a magnetic powder.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoconductor by various means, and the latent image is formed. The image is visualized with toner, and then the toner image is transferred to a transfer material such as paper, and then fixed by heating, pressure, or the like to obtain a copy. Many methods for visualizing an electric latent image using toner are also known, such as a magnetic brush method, a cascade developing method, a powder cloud developing method, and a fur brush developing method. Of these development methods,
In particular, a magnetic brush developing method using a so-called two-component developer mainly composed of a toner and a carrier has been widely put to practical use. Although this method is an excellent method that can obtain a good image relatively stably, on the other hand, due to the instability of the image quality due to the deterioration of the carrier and the fluctuation of the toner amount in the developer composed of the carrier and the toner, the toner There are problems that the inside of the apparatus is liable to be scattered due to scattering, and a complicated and expensive apparatus is required to control the toner concentration with high accuracy.

In order to solve the above problems, various developing methods using a magnetic one-component developer containing a magnetic powder in a toner have been proposed. As the magnetic one-component developing method, a method using a conductive magnetic toner and a method using an insulating magnetic toner have been proposed.

A developing method using a conductive magnetic toner is a method that solves the problems of the conventional two-component developing method. On the other hand, since the toner is conductive, a developed image can be transferred from a recording medium to plain paper or the like. However, there is a disadvantage that the image is disturbed when the image is electrostatically transferred to the transfer material.

A developing method using an insulating magnetic toner enables electrostatic transfer, as described in, for example,
JP-A-43036 proposes a method in which a magnetic toner is applied very thinly on a sleeve, which is frictionally charged by a regulating blade and a sleeve, and developed by applying an alternating electric field in a non-contact state with a photosensitive member. In this method, a high-resistance magnetic toner is applied very thinly on a sleeve to impart a charge to the toner, but the high-resistance magnetic toner used in the developing method generally includes a binder resin in 100 parts by weight. Since the magnetic powder is dispersed at a high concentration of about 50 to 150 parts by weight, a part of the magnetic particles is easily exposed on the surface of the toner particles. The sharp corners of the magnetic powder exposed when the layer is thinned may damage the sleeve, destabilize the triboelectrification, or cause the magnetic particles to be sharp when the transfer residual toner is cleaned with a cleaning blade. Because of the corners, the corners of the exposed magnetic particles easily damage the photoreceptor surface,
This may shorten the life of the photoconductor or cause image deterioration.

[0006] The degree of dispersion of the magnetic powder in the magnetic toner affects the triboelectric charging performance of the magnetic toner, and has a great effect on developability, transferability, environmental stability, durability of the sleeve and the photoreceptor, and paper. Or the like, to weaken the fixing strength between the transfer material and the magnetic toner. In JP-A-59-64852, a rounded magnetite powder is disclosed in Japanese Patent Publication No. 1-40976.
In Japanese Patent Application Laid-Open Publication No. H11-157, a magnetite powder having a controlled FeO content constituting magnetite is proposed, but it is not satisfactory in terms of reliability such as dispersibility in a binder resin, environmental stability, and fixability.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic toner which is excellent in environmental stability, reproducibility of a high-definition image, and fixing property, and which does not easily damage a photoreceptor deeply. is there.

[0008]

Means for Solving the Problems The first invention is a binder resin,
And a black magnetic iron oxide obtained by an ion electrolytic separation method.

According to a second aspect of the present invention, the particle diameter of the black magnetic iron oxide is 2
The magnetic toner according to the first invention, which has a thickness of 0 to 60 nm.

In a third aspect, the black magnetic iron oxide comprises 20 to 4 magnetic iron oxides.
The magnetic toner according to the first or second invention, having a specific surface area of 0 m ² / g.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic powder used in the present invention is black iron oxide (Fe ₃ O ₄ , which is generally called magnetite) conventionally used in this field. is there. A conventional method for producing magnetite is produced, for example, as follows. That is, ferrous sulfate heptahydrate is dissolved in distilled water, the solution is heated, and an aqueous solution of sodium hydroxide is added to neutralize the solution. After obtaining a hydroxide of iron by a neutralization reaction, the precipitate formed is oxidized while introducing air into the precipitate and stirred to obtain a precipitate of Fe ₃ O ₄ . The precipitate is washed, filtered, dried, and crushed to obtain a magnetite powder used for a magnetic toner. The magnetite obtained from this production method is mainly cubic, and the primary particles have a particle size of about 0.2 to 1 μm.

On the other hand, the black iron oxide used in the present invention is:
It is manufactured by the ion electric field separation method. The ion electric field separation method is a method in which an iron sulfate solution is subjected to ion electric field separation through an ion exchange membrane to collect SO ₃ ^- ions in an anode chamber and Fe ⁺⁺ ions in a cathode chamber. Fe ^{++ in the} cathode compartment
The ions are dissolved in a solution of alkali-soluble Fe-
(—O—OH) ₂₋ , which was directly subjected to a dehydration reaction to obtain a precipitate of Fe ₃ O ₄ , which was then washed with water, filtered, dried and then crushed to obtain primary particles of 20 to A rounded magnetite powder of 60 nm is obtained.

The specific surface area of the black iron oxide used in the present invention is preferably ²⁰ to 40 m ² / g. If the specific surface area is less than 20 m ² / g, aggregates increase and the toner is susceptible to the environment. Particularly, the image is easily deteriorated under high temperature and high humidity, and coarse particles are easily mixed and the photoreceptor is damaged. It will be easier. On the other hand, the specific surface area is 40 m ² /
If the value is larger than g, the black iron oxide becomes reddish black, and the resulting image becomes reddish.

The toner using the magnetite powder obtained by the ion electric field separation method has higher electric resistance than the toner using the magnetite powder according to the conventional manufacturing method, and has good charging performance even under various environments. The magnetite obtained by the ion electric field separation method has a finer size of 20 to 60 nm than the particles of about 0.2 to 1 μm obtained by the conventional manufacturing method.
Therefore, it is considered that when dispersed in the binder resin, the distance between the magnetite particles was increased and the toner was able to have high resistance. Also, magnetite obtained by the ion field separation method is considered to be unlikely to damage the photoreceptor surface because the corners of the magnetite particles are rounded, unlike the cubic crystal shape with sharp corners of the conventional method. Can be

As the binder resin used in the present invention, for example, polystyrene, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-
N-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-butadiene copolymer,
Polyester, epoxy resin, polyethylene, polypropylene, carnauba wax, paraffin wax and the like can be used alone or in combination.

Further, in the magnetic toner of the present invention, a charge controlling agent, a coloring agent, and a fluidity improving agent can be used, if necessary. Examples of the charge control agent include metal-containing dyes, nigrosine, and quaternary ammonium salts, and conventionally known dyes, pigments, and carbon can be used as appropriate as colorants. Colloidal silica can be used as a fluidity improver. There is titanium oxide and the like.

[0017]

The present invention will be described in detail with reference to the following examples.

Example 1 An iron sulfate solution was passed through an ion exchange membrane
Electrolyzed and obtained Fe in the cathode chamber ⁺⁺Ion, case
While neutralizing with a soda solution, a dehydration reaction is performed and FeO.F
e_TwoO_ThreeWas precipitated. After thoroughly washing this with water,
Filtration, drying, crushing with a jet mill crusher,
I got A. Electron microscope
Observation using a camera as shown in the attached photo (Fig. 1)
It has a rounded shape with sharp corners and a particle size of about 10
100 nm, specific surface area 33 m^Two/ G.

Styrene / butyl acrylate (MW = 370,000, MW / Mn = 33) 71% by weight Magnetite A 25% by weight Nigrosine base EX (Orient Chemical Industry) 2% by weight Low molecular weight polypropylene wax Using the above material of 2% by weight, After sufficiently stirring and mixing with a super mixer, the mixture was hot melt kneaded with a twin screw extruder. The obtained kneaded material was coarsely crushed to 2 mm or less by a hammer mill, then finely crushed by a jet mill, and further obtained by a gas flow classifier to obtain magnetic toner base particles (1) having an average particle diameter of 7 μm.

0.8 g of the magnetic toner base particles (1) are taken and left in a 23 ° C., 50% RH environment for 24 hours. afterwards,
A pressure of 400 kg / cm ² was applied by a tableting machine to apply a diameter of 2
A tablet sample of 0 mm and a thickness of about 1 mm is used. The resistivity and the dielectric loss angle of this sample were measured with a 4194 impedance / gain phase analyzer (Yokogawa / Hewlett-Packard). It is generally known that, for the same material and composition, the higher the resistance and the smaller the dielectric loss angle, the better the homogeneity of the individual particles of the toner. These values are shown in Table 1.

Next, the obtained magnetic toner base particles (1)
0.5% by weight of silica RA200HS (manufactured by Nippon Aerosil Co., Ltd.) was added to 100% by weight, and mixed with a super mixer to obtain a magnetic toner (2). A commercially available copying machine using an organic photoreceptor (Canon Inc.) NP2120)
An actual image test was performed on each of 3000 sheets in both an environment of 15 ° C. and 20% RH and an environment of 30 ° C. and 85% RH, and the density of the obtained image was determined by Macbeth RD918 (Macbeth Densitometer). The concentration was 1.3. For the non-image area fog, see Photobolt Model 577
(Fogging tester manufactured by Photobolt Co., Ltd.), it was always stable at 0.7% or less under each environment. In addition, a uniform image was obtained without any damage on the photoreceptor.

[0021]

Comparative Example 1 In place of magnetite A of Example 1, the particle size was 0.4 μm and the specific surface area was 6.2 m ² obtained by a conventional method.
/ G of cubic magnetite was used, and toner mother particles (3) were obtained in the same manner as in Example 1 except for the above. The resistivity and dielectric loss angle of the obtained magnetic toner base particles (3) were determined in Example 1.
Was determined in the same manner as in. Table 1 shows the results. When a copying test similar to that in Example 1 was performed, the temperature was 15 ° C., 20%
An image density of 1.3 was obtained under the RH environment, but the density of the non-image area was 1.3.
On the other hand, under the environment of 30 ° C. and 85% RH, fog was as good as 0.5% but the image density was 1.05 and only a poor image could be obtained.

[0022]

Example 2 Polyester resin (MW = 50000, MW / Mn = 12.5) 58% by weight Magnetite A 38% by weight Bontron S-34 (Orient Chemical Industries) 2% by weight Low molecular weight polypropylene wax 2% by weight The above materials were used. Average particle size 7 μm in the same manner as in Example 1.
And the resistivity and dielectric loss angle of the obtained magnetic toner base particles (4) were determined in the same manner as in Example 1. The results are shown in Table 1.

Next, 0.7% by weight of hydrophobic silica HDK-H3004 (manufactured by Hoechst) is added to 100% by weight of the magnetic toner base particles (4) and mixed with a super mixer to obtain a magnetic toner (5). Using a commercially available copier (GP55, manufactured by Canon Inc.), the temperature was adjusted to 30 ° C. and 15% C.
A real-photo test was performed on each of 5,000 sheets under both environments of 85 ° C. and 85% RH. A stable image was obtained under each environment, the image density was 1.3 or more, and the fog was 0.5% or less. In addition, a smooth image was obtained without any damage to the photoreceptor.

[0024]

Comparative Example 2 Instead of magnetite A of Example 2, the average particle size obtained by a conventional method was 0.7 μm, and the specific surface area was 2.8.
Magnetic toner mother particles (6) were obtained in the same manner as in Example 1 except that m ² / g of magnetite was used. The resistivity and dielectric loss angle of the obtained magnetic toner base particles (6) were determined in Example 1.
And the results are shown in Table 1. When a copying test similar to that in Example 2 was performed, an image density of 1.35 was obtained in a 15 ° C. and 20% RH environment. On the other hand, the fog was conversely as good as 0.7%, but the image density was 0.93, and only a poor image could be obtained. Also, 30 ° C 85%
During the actual shooting test under the RH environment, white spots increased in the solid black portion of the image as the number of images increased. Observation of the photoreceptor confirmed that the toner was fused to the white spots of the image. When the fused material was removed, a small hole was formed on the surface of the photoreceptor. This phenomenon is presumed to be due to the fact that the poorly dispersed magnetic powder dropped from the toner was pressed against the photoreceptor by the cleaning blade to cause damage, and then the remaining transfer toner entered the hole and fused by frictional heat with the cleaning blade. You.

[0025]

[Table 1]

[0026]

By using the black magnetic iron oxide obtained by the ion electrolytic separation method, a high-resistance magnetic toner in which magnetic powder is well dispersed can be obtained, and a stable image can be formed even in various environments. Thus, it is possible to provide a magnetic toner which has excellent fixability and does not damage the photoreceptor.

[0027]

[Brief description of the drawings]

FIG. 1 is a transmission electron micrograph of magnetite A obtained in Example 1.

Claims (3)

[Claims] 1. A magnetic toner comprising a binder resin and a black magnetic iron oxide obtained by an ion electrolytic separation method. 2. The black magnetic iron oxide has a particle size of 20 to 60 nm.
The magnetic toner according to claim 1, wherein 3. The magnetic toner according to claim 1, wherein the black magnetic iron oxide has a specific surface area of ²⁰ to 40 m ² / g.