JP3417250B2 - Magnetic toner - Google Patents

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 electrostatic recording, electrophotography and the like, and more particularly to a magnetic toner containing magnetic powder.

[0002]

2. Description of the Related Art Conventionally, many electrophotographic methods are known, but generally, 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 are known for visualizing an electric latent image using toner, and examples thereof include 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 development method using a so-called two-component developer mainly composed of toner and carrier has been widely put into practical use. This method is an excellent method in which a good image can be obtained relatively stably, but on the other hand, due to the instability of the image quality due to deterioration of the carrier and the variation of the toner amount in the developer composed of the carrier and the toner, There are problems that the inside of the machine is likely to be scattered due to scattering, and that a complicated and expensive device is required to accurately control the toner concentration.

In order to solve the above problems, various developing methods using a magnetic one-component developer containing magnetic powder in the 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.

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

In the developing method using the insulating magnetic toner, electrostatic transfer is possible.
JP-A-43036 proposes a method in which a magnetic toner is applied very thinly on a sleeve, the toner is triboelectrically charged by a regulating blade and a sleeve, and an alternating electric field is applied to the photoconductor in a non-contact state to develop the toner. In this method, the high-resistance magnetic toner is applied to the sleeve very thinly to give the toner charge. However, the high-resistance magnetic toner used in the developing method generally contains 100 parts by weight of the binder resin. Since the magnetic powder is dispersed in a high concentration of about 50 to 150 parts by weight, some of the magnetic particles are easily exposed on the surface of the toner particles, and since the magnetic particles have sharp edges, the toner on the sleeve is When the layer is thinned, the sharp corners of the exposed magnetic powder damage the sleeve, destabilize the triboelectrification property, and when the untransferred toner is cleaned with a cleaning blade, the magnetic particles are sharp. The corners of the exposed magnetic particles tend to damage the surface of the photoconductor because they have corners,
It also shortens the life of the photoconductor and causes image deterioration.

The degree of dispersion of the magnetic powder in the magnetic toner influences the triboelectrification performance of the magnetic toner and has a great influence on the developability, transferability, environmental stability, durability of the sleeve and the photoconductor, and the paper. It weakens the fixing strength between the material to be transferred and the magnetic toner. In JP-A-59-64852, rounded magnetite powder is disclosed in Japanese Patent Publication No. 1-40976.
Japanese Patent Laid-Open Publication proposes a magnetite powder in which the FeO content of the magnetite is controlled, 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 An object of the present invention is to provide a magnetic toner which is excellent in environmental stability, reproducibility of high-definition images, and fixability, and which is hard to damage a photoreceptor deeply. is there.

[0008]

The first invention is a binder resin,
And ferrous sulfate solution through the ion exchange membrane to generate divalent iron ions
A magnetic toner containing black magnetic iron oxide obtained by an ion electrolytic separation method for separating and collecting .

The second invention is that the particle size of black magnetic iron oxide is 2
The magnetic toner according to the first invention is characterized in that it has a thickness of 0 to 60 nm.

In a third aspect of the invention, black magnetic iron oxide is contained in an amount of 20-4.
The magnetic toner according to the first invention or the second invention, which has 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 generally called magnetite) which has been conventionally used in this field. is there. A conventional magnetite manufacturing method is manufactured as follows, for example. That is, ferrous sulfate heptahydrate is dissolved in distilled water, the solution is heated, and caustic soda aqueous solution is added to neutralize the solution. After the iron hydroxide is obtained by the neutralization reaction, air is added to the formed precipitate to oxidize it while stirring to obtain a Fe ₃ O ₄ precipitate. The precipitate is washed, filtered, dried, and crushed to obtain magnetite powder used for magnetic toner. The magnetite obtained from this manufacturing method is mainly cubic crystal, and the particle size of primary particles is 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 electrolytic separation method . Ionic electrolysis
The separation method is a method in which an iron sulfate solution is subjected to ion electrolytic separation through an ion exchange membrane to collect SO ₃ − ions in the anode chamber and Fe ⁺⁺ ions in the cathode chamber. Fe ^{+ + in the} cathode chamber
Ions are dissolved in an alkaline atmosphere in a solution of soluble Fe-
_{(-O-OH) 2-} and was, by performing direct dehydration reaction which, to obtain a precipitate of Fe ₃ O _4, then washed with water the precipitate was filtered, dried disintegration to primary particles 20 60 nm
A round and rounded magnetite powder 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, agglomerates increase, the toner is apt to be affected by the environment, the image is apt to be deteriorated especially under high temperature and high humidity, and coarse particles are apt to be mixed, so that the photoreceptor is damaged. It will be easier. On the other hand, the specific surface area is 40 m ² /
When it is larger than g, the black iron oxide becomes reddish black, the obtained image is reddish, which is not preferable, and the holding power is low, and the toner is easily scattered.

The toner using the magnetite powder obtained by the ion electrolytic separation method has a higher electric resistance than the toner using the magnetite powder of the conventional manufacturing method, and has good charging performance even under various environments. The magnetite obtained by the ionic electrolytic separation method has a particle size of 20 to 60 nm, which is finer than the particles of about 0.2 to 1 μm obtained by the conventional method.
Therefore, it is considered that when dispersed in the binder resin, the distance between the magnetite particles was increased and the toner could have a high resistance. In addition, magnetite obtained from the ionic electrolytic separation method is considered to be hard to damage the surface of the photoconductor because the magnetite particles have rounded corners unlike the cubic shape with sharp corners in the conventional method. To be

Examples of the binder resin used in the present invention include 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 Polymer, styrene-butadiene copolymer,
Polyester, epoxy resin, polyethylene, polypropylene, carnauba wax, paraffin wax, etc. can be used alone or in combination.

Furthermore, in the magnetic toner of the present invention, a charge control agent, a colorant and a fluidity improving agent can be used, if necessary. As the charge control agent, there are metal-containing dyes, nigrosine, quaternary ammonium salts and the like. As the colorant, conventionally known dyes, pigments, carbon and the like can be used in a timely manner, and as the fluidity improving agent, colloidal silica, There are 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 to produce ions.
Fe in the cathode chamber obtained by electrolysis ⁺⁺Aeon, Kasei
FeO · F by dehydration reaction while neutralizing with soda solution
e₂O₃Was deposited. After washing this thoroughly with water,
It is filtered and dried, crushed with a jet mill crusher, and magnetized.
Got Ito A. The morphology of this magnetite A
Observed by using, as shown in the attached photo (Fig. 1)
In addition, it has a rounded shape with rounded corners and a particle size of about 10
100 nm, specific surface area 33 m²/ G.

Styrene butyl acrylate (MW = 370000, MW / Mn = 33) 71% by weight Magnetite A 25% by weight Nigrosine base EX (Orient Chemical Industries) 2% by weight Low molecular weight polypropylene wax 2% by weight After thoroughly stirring and mixing with a super mixer, the mixture was hot melt kneaded with a twin-screw extruder. The obtained kneaded product was roughly crushed to 2 mm or less with a hammer mill, then finely pulverized with a jet mill, and magnetic toner mother particles (1) having an average particle size of 7 μm were obtained with an air stream classifier.

0.8 g of the magnetic toner mother particles (1) is taken and left in an environment of 23 ° C. and 50% RH for 24 hours. afterwards,
Apply a pressure of 400 kg / cm ^{2 with} a tablet press and make the diameter 2
A tablet sample having a thickness of 0 mm and a thickness of about 1 mm is used. This sample was measured for resistivity and dielectric loss angle with a 4194 impedance / gain phase analyzer (Yokogawa, Hewlett Packard). It is generally known that in the case of the same material / composition, the higher the resistance and the smaller the dielectric loss angle, the better the homogeneity of the particles of each toner. These values are shown in Table 1.

Next, the obtained magnetic toner mother 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 (Canon Co.) using an organic photoconductor was used. NP2120 manufactured by
An image was obtained by performing a live-action test on 3000 sheets each under 15 ° C., 20% RH environment and 30 ° C. 85% RH environment, and determining the density of the obtained image with Macbeth RD918 (Macbeth Densitometer). The concentration was 1.3. For non-image part fog, Photovolt Model 577
When measured with a (fog measuring device made by Photovoltaic), it was always stable at 0.7% or less in each environment. Further, a uniform image was obtained without any scratch on the photoconductor.

[0021]

COMPARATIVE EXAMPLE 1 Instead of the magnetite A of Example 1, the particle size was 0.4 μm and the specific surface area was 6.2 m ² obtained by the conventional method.
Toner mother particles (3) were obtained in the same manner as in Example 1 except that a cubic magnetite of / g was used. The resistivity and the dielectric loss angle of the obtained magnetic toner mother particles (3) were measured in Example 1
It was obtained by the same method as. The results are shown in Table 1. Further, when a copying test similar to that in Example 1 was conducted, it was 15 ° C., 20%
Image density of 1.3 was obtained under the RH environment, but 1.
In the environment of 30 ° C. and 85% RH, the fog was good at 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 wt% Magnetite A 38 wt% Bontron S-34 (Orient Chemical Industries) 2 wt% Low molecular weight polypropylene wax 2 wt% Implemented using the above materials Average particle size 7 μm in the same manner as in Example 1
The magnetic toner mother particles (4) were obtained, and the resistivity and the dielectric loss angle of the obtained magnetic toner mother particles (4) were obtained 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 mother particles (4) and mixed by a super mixer to obtain a magnetic toner (5). , Using a commercially available copier (GP55, manufactured by Canon Inc.) at 15 ° C. and 20% RH environment and 30
A live-copy test was performed on 5000 sheets each in both environments under the condition of 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. Further, a smooth image was obtained without any scratch on the photoconductor.

[0024]

[Comparative Example 2] Instead of the magnetite A of Example 2, the average particle size obtained by the 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 the dielectric loss angle of the obtained magnetic toner mother particles (6) were measured in Example 1
The results are shown in Table 1. When a copy test was conducted in the same manner as in Example 2, an image density of 1.35 was obtained under the environment of 15 ° C. and 20% RH, but 1.1% fog was generated in the non-image area, and the environment was 30 ° C. and 85% RH. On the contrary, on the contrary, the fog was good at 0.7%, but the image density was 0.93 and only a poor image could be obtained. Also, 30 ° C 85%
During the live-action test under the RH environment, white dots increased in the solid black portion of the image as the number of sheets was piled up. When the photoreceptor was observed, it was confirmed that the toner was fused in correspondence with the white spots on the image. When this fused substance was removed, small holes were opened on the surface of the photoreceptor. It is presumed that this phenomenon is caused by magnetic particles of poor dispersion dispersed from the toner being pressed against the photoconductor by the cleaning blade and scratched, and the residual toner after transfer entered the holes and fused due to frictional heat with the cleaning blade. It

[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 is formed even under various environments. Therefore, it is possible to provide a magnetic toner having excellent fixability and not damaging the photoreceptor.

[0027]

[Brief description of drawings]

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

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Claims (3)

(57) [Claims] 1. A binder resin and an iron sulfate solution are ion-exchanged.
Ion electrolytic component that separates and collects divalent iron ions through the membrane
A magnetic toner containing black magnetic iron oxide obtained by a separation method . 2. The particle size of black magnetic iron oxide is 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.