JPH0141983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner, particularly a magnetic color toner, used in electrophotography, electronic printing, electrostatic recording, magnetic recording, and the like.

Electrophotography uses the properties of photoconductors such as cadmium sulfide, polyvinyl carbazole, selenium, and zinc oxide to form electrostatic latent images. and imagewise exposure is performed to form an electrostatic latent image, and then developed with toner powder charged with a polarity opposite to that of the electrostatic latent image,
Furthermore, if necessary, the image is transferred to a transfer sheet and fixed.

The electronic printing law is Special Publication No. 42-14342 and No. 40-771.
As proposed in Japanese Patent No. 38-20166, No. 41-8024, etc., this is a method of guiding and fixing a charged powder toner onto a recording material using an electric field for printing.

Electrostatic recording is a method in which an electric charge is applied to an image on a dielectric material, and charged toner powder is attached to the image to fix it. Similarly, magnetic printing is a method in which a magnetic latent image is formed on a recording material. This is then developed with toner powder containing a magnetic material, transferred to a transfer sheet, and fixed.

In the method of using a one-component magnetic toner without using carrier particles in the development system of the above process, the toner is transported by a magnet roll to form a magnetic brush, and the magnetic brush is made of a photoconductor such as cadmium sulfide or an insulating material. When the toner comes into contact with an electrostatic charge holder, the charge on the holder and the induced static electricity or triboelectric static electricity held by the toner are attracted, and the toner adheres to the electrostatic charge holder, thereby performing development. This developing method using one-component magnetic toner does not require a device to maintain a constant toner concentration in the developer, which is required in two-component developing methods using carrier particles, and the developing device is simplified. , it is advantageous in terms of low cost or miniaturization.

On the other hand, recently, the purposes of use have become more diverse, and there is a desire for a compact and inexpensive multi-color copying machine that can produce images in desired colors as needed. The color tone of the magnetic material cannot be hidden simply by adding a coloring agent to the binder resin. For example, JP-A No. 51-42539 describes coating magnetic powder with white pigment by chemical treatment, but the amount of magnetic powder and dye/pigment must be within the range that does not adversely affect the development characteristics. However, simply applying a chemical treatment to cover the magnetic material was not effective enough to hide the color tone of the magnetic material. In order to obtain a toner with the desired color tone using the above method, it is possible to reduce the amount of magnetic material more than necessary or increase the amount of coloring pigment, but if the amount of magnetic material is reduced too much, the developability will deteriorate. If the amount of color pigment was increased too much, problems such as a decrease in developability and a decrease in fixability occurred. It has been difficult to produce magnetic toners that satisfy all characteristics such as developability, color tone, and fixability.

An object of the present invention is to provide a richly colored magnetic color toner.

A further object of the present invention is to provide a magnetic color toner that can provide images with high density, clarity, and less fog.

A further object of the present invention is to provide a magnetic color toner with excellent fixing properties.

Specifically, the present invention uses a magnetic powder having a specific surface area of 0.5 to 3.0 m ² /g through a sintering process, a binder resin, and a red, blue, green, yellow, or violet colorant. An object of the present invention is to provide a magnetic color toner characterized by containing:

In a preferred embodiment of the present invention, the binder resin 100
It is preferable to contain 30 to 80 parts by weight of magnetic powder that has undergone a sintering process, and further preferably to contain 10 to 15 parts by weight of a coloring agent, as described in the Examples below. .

The magnetic powder produced through the sintering process used in the present invention may be well-known materials such as iron, nickel, Fe ₃ O ₄ , Fe ₂ O _{3 ,} etc., but it can be surface treated such as titanium coupling treatment. It is also possible to apply It may be used in combination with other magnetic powders, but in that case, the amount of other magnetic powders needs to be 40% by weight or less (preferably 20% by weight or less) of the total magnetic content. In particular, when used as a magnetic color toner, particles with an average particle diameter of 0.5 to 3.5 (preferably 1.0 to 2.5)μ when observed using an electron microscope, and a specific surface area of 0.5 to 3.5μ by BET nitrogen adsorption are preferred.
3.0 (preferably 1.0 to 2.5) m ² /g is good.
Further, a coloring treatment such as a dye may be applied.

Taking Fe ₃ O ₄ as an example, the method for producing magnetic powder obtained through the sintering process is to evaporate raw material α-Fe ₂ O ₃ with a specific surface area of 0.5 m ² /g or more by BET nitrogen adsorption method into air. heating at a temperature of preferably 700°C to 1300°C (particularly preferably 900°C to 1200°C) for 30 minutes or more;
After sintering, there is a method of obtaining sintered type Fe ₃ O ₄ by cooling and pulverizing steps and then heating and reducing in a hydrogen or hydrocarbon atmosphere, preferably propane. .

A wide variety of binder resins can be used as the binder resin used in the present invention, including known ones, such as polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, and styrene-propylene copolymer. Combined, styrene-
Butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-acrylic ethyl acid copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylate copolymer, etc.) ethyl acid copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic ester copolymer, etc. Styrenic resin (unipolymer or copolymer containing styrene or styrene substitutes), vinyl chloride resin, ethylene-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, low molecular weight polystyrene , low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, etc. The above resins are not limited to being used alone, but two or more types can be used in combination. You can also do that.

As the coloring agent used in the magnetic color toner of the present invention, the following red type, blue type, green type,
Examples include yellow or violet colorants. Examples of dyes include CI Direct Red 1, CI Direct Red 4, CI Assisted Red 1, CI Basic Red 1, CI Modern Red 30, CI Direct Blue 1, CI Direct Blue 2, CI Acid Blue 9, CI Acid Blue 15, and CI Basic. Blue 3, CI
Basic Blue 5, CI Modern Blue 7,
There are CI Direct Green 6, CI Basic Green 4, CI Basic Green 6, etc. Pigments include yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow G, permanent yellow NCG, tartrazine lake, red yellow lead, molybdenum orange, and permanent orange.
GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red
4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Dark Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene blue BC, chrome green, chromium oxide,
Pigment Green B, Malachite Green Lake, Final Yellow Green G, etc.

Additives may be mixed into the toner of the present invention as necessary, and examples of such additives include lubricants,
Fixing aids such as polyethylene, flow agents, anti-caking agents such as colloidal silica, and oil lubricants such as fatty acid metal salts,
Polytetrafluoroethylene, polyvinylidene fluoride, etc., and cerium oxide as an abrasive.

To develop a latent image using the toner of the present invention, a method using a conductive magnetic toner described in U.S. Pat.
JP-A-53-83630, JP-A No. 53-83630, JP-A No. 53-83630, JP-A-53-83630, JP-A No. 53-83630, JP-A No. 53-83630, JP-A No. 53-83630, JP-A-53-83630, JP-A No. 53-83630, JP-A No. 53-83630, JP-A-53-83630, JP-A No. 53-83630, JP-A-53-83630, JP-A No. 53-83630,
The magnetic toner described in JP-A No. 24632 can be used in known development methods such as the so-called microtoning development method using non-magnetic toner, but the magnetic toner described in JP-A-54-42141 and JP-A-55-18656 is Particularly preferred is a method using an insulating toner that is

That is, an electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic developer on its surface are arranged with a certain gap between them, and the insulating magnetic developer is In this method, the insulating magnetic developer is deposited on a carrier to a thickness thinner than the gap, and the insulating magnetic developer is transferred to the electrostatic image carrier under the action of a magnetic field, thereby performing development.

A method for manufacturing a magnetic material obtained through a sintering process in a manufacturing example will be described below.

Production example 1 α-Fe ₂ O ₃ with an average particle size of 0.5μ is heated in air at 1000°C for 5 hours, cooled, and crushed with an atomizer to produce α-Fe ₂ O ₃ with an average particle size of 1.3μ. Obtained. this
Reduced in a hydrogen atmosphere at 250℃, crushed after cooling,
Approximately 1.3μ magnetite was obtained. The specific surface area measured by BET method was 1.9 m ² /g.

Production Example 2 After heating α-Fe ₂ O ₃ with an average particle size of 0.4 μ in air at 1100°C for 5 hours, it was cooled and crushed with an atomizer to produce α-Fe ₂ O ₃ with an average particle size of 1.8 μ. Obtained. this
It was reduced in a propane atmosphere at 450°C, cooled, and then crushed to obtain magnetite of approximately 1.8μ. The specific surface area measured by BET method was 1.3 m ² /g.

Production Example 3 By oxidizing the 1.3μ magnetite obtained in Production Example 1 in air at 250°C, a part of the 1.3μ γ-
Brown Fe ₃ O ₄ converted into Fe ₂ O ₃ was obtained.

The specific surface area measured by BET method was 2.0 m ² /g.

The method for producing the toner of the present invention will be described in detail in Examples below.

Example 1 Styrene-butadiene copolymer (70:30)
100 parts by weight 3-5 Chromium complex salt of ditertiary butylsalicylic acid 2 〃 Magnetite (Production Example 1) 60 〃 CI Direct Blue 2 10 〃 Polyethylene 3 〃 The above mixture was kneaded with a roll mill at 150°C, and after cooling, it was coarsened with a speed mill. Smash. Thereafter, it was finely pulverized using a jet mill, and a blue magnetic toner having a size of 5 to 20 μm was obtained using an air classifier.

Apply this blue magnetic toner to a commercially available copier (product name).
As a result of image printing with NP-201 (manufactured by Canon),
A clear image with good blue color and little fogging was obtained. Furthermore, the fixing properties were also good.

Example 2 Styrene-methyl methacrylate copolymer (60:
40) 100 parts by weight 3-5 Chromium complex salt of ditertiary butylsalicylic acid 2 〃 Magnetite (Production Example 2) 50 〃 CI Direct Green 6 15 〃 Polyethylene 3 〃 The above mixture was made into a toner in the same manner as in Example 1 and imaged. As a result, a green image with good image quality and color tone was obtained.

Example 3 The same procedure as in Example 1 was performed except that the magnetite in Production Example 1 was changed to the magnetic material in Production Example 3, and CI Direct Blue 2 was changed to CI Direct Red 4. As a result, line breakage, A very bright red image with good fixability was obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that instead of using the magnetite obtained in Production Example 1, magnetite with an average particle size of 1.3μ that was produced by a wet method and had not undergone a sintering process was used. As a result, a blue image with a dark and cloudy tone was obtained, and the fixability was poor.

Claims (1)

[Scope of Claims] 1. Magnetic powder having a specific surface area of 0.5 to 3.0 m ² /g after undergoing a sintering process, a binder resin, a red type, a blue type,
A magnetic color toner characterized by containing a green, yellow or violet colorant. 2. The magnetic color toner according to claim 1, which contains 30 to 80 parts by weight of the magnetic powder that has undergone a sintering process and 10 to 15 parts by weight of a colorant per 100 parts by weight of the binder resin.