JPH056185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner used in electrophotography, electrostatic recording, etc., and particularly relates to an insulating magnetic color toner.

Conventional electrophotographic methods include US Pat.
A number of methods are known, as described in Japanese Patent Publication No. 3666363) and Japanese Patent Publication No. 43-24748 (U.S. Pat. No. 4071361), but generally they utilize a photoconductive substance, An electrical latent image is formed on a photoreceptor by various means, and if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, etc. to obtain a copy.

Various developing methods are also known in which an electrostatic latent image is visualized using toner. For example, U.S. Patent No.
The magnetic brush method described in specification No. 2874063,
The cascade development method described in Specification No. 2618552, the powder cloud method and fur brush development method described in Specification No. 2221776,
Many development methods are known, such as liquid development. Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method, etc., which use a developer mainly consisting of toner and carrier, are in particular widely put into practical use. All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such drawbacks, various development methods using a one-component developer made only of toner have been proposed, but among them, many methods using a developer made of magnetic toner particles are superior. .

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. In this method, conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism inside, and is brought into contact with an electrostatic image to be developed. At this time, in the developing section, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and charges are guided from the sleeve to the toner particles through this conductivity, thereby creating a connection between the electrostatic image and the image area. Toner particles adhere to the image area due to Coulomb force and are developed. This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method. It has the disadvantage that it is difficult to electrostatically transfer it to a permanent support member.

As a developing method using high-resistance magnetic toner that can be electrostatically transferred, Japanese Patent Application Laid-Open No. 52-94140
The publication discloses a developing method that utilizes dielectric polarization of toner particles. However, such a method inherently has drawbacks such as slow development speed and insufficient density of the developed image, and is difficult in practice.

Another developing method using high-resistance magnetic toner is a method in which the toner particles are triboelectrified by friction between the toner particles or friction between the toner particles and a sleeve, etc., and the toner particles are brought into contact with an electrostatic image holding member for development. It has been known. However, these methods have drawbacks such as the number of times the toner particles come into contact with the friction member is small and frictional charging tends to be insufficient, and the Coulomb force between the charged toner particles and the sleeve increases and they tend to aggregate on the sleeve. This made it difficult to implement in practice.

However, in JP-A-55-18656, etc.
A new development method has been proposed which eliminates the above-mentioned drawbacks. This involves applying a very thin layer of magnetic toner onto the sleeve, triboelectrically charging it, and then developing it in close proximity to the electrostatic image. This method increases the chances of contact between the sleeve and toner by applying an extremely thin layer of magnetic toner onto the sleeve, which enables sufficient frictional electrification, supports the toner by magnetic force, and connects the magnet and toner. By moving the toner particles relative to each other, mutual agglomeration is eliminated and sufficient friction with the sleeve is achieved, and the toner is supported by magnetic force and developed by facing the electrostatic image without coming into contact with it. Excellent images can be obtained by preventing background fog.

Ferromagnetic elements and alloys and compounds containing these elements (for example, compounds containing iron, cobalt, nickel, manganese, zinc, etc., such as magnetite, maghemite, and ferrite) have been known as magnetic materials for magnetic toner. . The various properties required of such magnetic materials include, for example, (1)
Maximum magnetizing force σm of about 40emu/g or more, (2) 150 ~
Coercive force Hc of about 500 Oe, (3) specific electrical resistivity of 10 ² to 10 ⁷ Ω-cm, (4) blackness sufficient for practical use, (5) good moisture resistance, (6) good bonding with resin. Mixability etc. are known. Usually, magnetite, which is called iron black and is commonly used as a pigment, is often used in magnetic toners, and there are many examples described in various patent documents. This magnetite generally satisfies the above requirements, but for use in insulating magnetic toner, its properties must be carefully examined in terms of miscibility with resin, toner cohesiveness, triboelectric charging properties, and durability. It is said that

When a one-component magnetic toner is supported by magnetic force, is faced to an electrostatic charge image without contacting it, and is developed by applying an alternating electric field and a bias electric field during development, individual developer particles are , Coulomb force with the electrostatic charge image, magnetic force with the magnetic brush forming magnet, force due to an alternating electric field, etc. act. Particles on which a large Coulomb force acts are attracted to the electrostatic charge image, while particles on which a large magnetic force acts are attracted toward the developing sleeve, and development according to the electrostatic charge image is achieved. Furthermore, when transferring the magnetic toner developed on the photoreceptor onto transfer paper, a corona discharge with the opposite polarity to the charge polarity of the magnetic toner, that is, the same polarity as the electrostatic latent image, is performed from the back of the transfer paper. Then, the toner image is attracted to the surface of the transfer paper. At this time, if the charge on the toner particles easily escapes and disappears, the transferred image will be blurred or the transfer efficiency will be reduced. That is,
Since magnetic toner contains a relatively large amount of magnetic powder as its constituent component, it is strongly required that the magnetic powder has the property of stably retaining an electric charge.

Further, since conventional one-component toners contain 20 to 80% by weight of magnetic material, they have the disadvantage that it is difficult to fix the toner on copy paper by heat fixing or pressure fixing.

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, in JP-A-51-42539, it is recorded that magnetic powder is coated with a 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. When the amount of the color pigment decreased or 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 colorful magnetic toner.

A further object of the present invention is to provide a magnetic toner that provides high density, clear images with less fog.

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

Specifically, the present invention provides a magnetic color toner containing a binder resin, a colorant exhibiting red, blue, yellow, orange, or violet color tone, and a magnetic material, in which the magnetic material has an average particle size of
The present invention relates to a magnetic color toner characterized in that it contains only 0.001 to 2 wt% of ultrafine magnetic particles produced from Fe--Co metal or Fe--Ni metal, with a coercive force of 0.02 to 0.05 μ and a coercive force of 1000 oersted or more.

The method for manufacturing these ultrafine magnetic particles is as follows:
Broadly speaking, there are chemical methods and physical methods. The former method includes a method that utilizes a thermal decomposition reaction of a metal salt, a method that adds a precipitant to an aqueous solution of a metal salt to form a precipitate of salt or metal hydroxide, and then roasts this to produce ultrafine metal oxide powder. There is.

In particular, as a method for obtaining ultrafine magnetic particles suitable for the present invention, there is a method in which an aqueous solution of metal ethoxide and metal acetonate is used as a starting material, hydrolyzed at pH 10 to 11, and the precipitate is calcined at around 800°C. . Specific examples of ultrafine magnetic particles obtained by this method include barium hexaferrite of 5,000 to 7,000 oersted and strontium hexaferrite.

Further, physical methods include mechanical crushing of lumpy materials and atomization method of atomizing molten metal. In particular, as a method for obtaining ultrafine magnetic particles suitable for the present invention, a method of evaporating metal in an inert gas is preferable.

The ultrafine magnetic particles are preferably contained in the toner in an amount of 0.001 to 2% by weight, preferably 0.001 to 0.5% by weight.

If the amount of magnetic material is less than the above range (0.001 to 2% by weight), the magnetic properties of the toner will be insufficient;
Sleeve transportability deteriorates and development characteristics deteriorate.
If the amount exceeds this range, the electrical properties and fixing properties will deteriorate, and when used as a color toner, the color will become cloudy and vivid colors will not be obtained.

As the binder resin for the toner, homopolymers of styrene and its substituted products, such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer, and copolymers thereof are used. Coalescence: Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid n-
Copolymers of styrene and acrylic esters such as butyl copolymers; styrene and methacrylates such as styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, and styrene-n-butyl methacrylate copolymers Copolymers with esters; multi-component copolymers of styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, styrene vinyl methyl ether copolymers, styrene butadiene copolymers, styrene vinyl methyl ketone copolymers Polymers, styrenic copolymers of styrene and other vinyl monomers such as styrene acrylonitrile indene copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate polyesters, polyamides , epoxy resin, polyvinyl butyral,
Polyacrylic acid phenolic resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin,
etc. can be used alone or in combination.

Furthermore, as binder resins for toners used in pressure fixing systems, low molecular weight polyethylene, low molecular weight polypropylene, ethylene vinyl acetate copolymers, ethylene acrylate copolymers, higher fatty acids, polyamide resins, polyester resins, etc. are used. Can be used alone or in combination.

More desirable results can be obtained if the polymer, copolymer, or polymer blend used contains a vinyl aromatic or acrylic monomer represented by styrene in an amount of 40 wt % or more.

Furthermore, a charge control agent, a colorant, and a fluidity modifier may be added to the toner of the present invention as necessary, and the charge control agent and fluidity modifier may be mixed with the toner particles (external additives). ) may also be used. Examples of the charge control agent include metal-containing dyes and nigrosine, and conventionally known dyes and pigments can be used as the colorant, and examples of the fluidity modifier include colloidal silica and fatty acid metal salts. There is.

Further, for the purpose of increasing the amount, fillers such as calcium carbonate and finely powdered silica can be incorporated into the toner in an amount of 0.5 to 20 wt%. Furthermore, in order to prevent toner particles from coagulating with each other and improve their fluidity, a fluidity improver such as fine Teflon powder may be added to the toner, for the purpose of improving mold release properties during hot roll fixing. Approximately 0.5 to 5 wt% of wax-like substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, and Sasol wax can also be added.

When the toner of the present invention is used as a magnetic color toner, a coloring agent may be added as necessary, and known pigments or dyes can be used as the coloring agent. 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, Nahetol 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.

When producing toner, the constituent materials are thoroughly kneaded using a thermal kneading machine such as a hot roll, kneader, or extruder, and then obtained by mechanical crushing and classification, or in a binder resin solution. Magnetic powder can be obtained by dispersing a material such as magnetic powder in a liquid and then spray-drying it, or by mixing a specified material with a monomer that should constitute a binder resin and then polymerizing this emulsified suspension. Each method can be applied, such as a polymerization method to obtain a toner and a toner manufacturing method.

The point to be noted here is that ultrafine magnetic particles are activated because they have an extremely large specific surface area, and there is a risk of rapid oxidation, combustion, or explosion even at room temperature. It may be necessary to carry out the process in an active gas or nitrogen atmosphere or in a vacuum.

Also, if the toner contains 0.1% by weight or more of ultrafine magnetic particles, development can be performed using a normal ferrite magnet (approximately 800G on the sleeve), but if the magnetic material is 0.001 to 0.1% by weight, is a rare element alloy magnet (7000G on sleeve)
By using the above), developability is ensured.

By creating a magnetic toner containing a small amount of ultrafine magnetic particles in this way, the fixing properties are improved and it becomes possible to produce a color toner with vivid colors.

Example 1 Styrene-acrylic copolymer 100 parts by weight Fe-Co (average particle size 0.02 μ, Hc = 2300 oersted) 1 part by weight Phthalocyanine blue 5 parts by weight Trichlene 5 parts by weight Trichlene was added while heating the above mixture at 70°C. was evaporated. Next, this solid material was passed through a hammer mill, a jet pulverizer, and a classifier to obtain particles of 5 to 20 microns.

Next, 0.5 parts of hydrophobic silica powder was externally added to 100 parts by weight of these particles to obtain a developer, and PC-10
(Canon's personal copier), a clear blue image was reproduced.

Example 2 When the same treatment as in Example 1 was performed using Fe-Ni (average particle size 0.03μ, Hc = 1300 oersted) instead of Fe-Co in Example 1, the same results as in Example 1 were obtained. Obtained.

Example 3 Same composition as Fe-Co in Example 1, average particle size
The same results as in Example 1 were obtained by carrying out the same treatment as in Example 1, except that 2 parts by weight of 0.025μ and Hc = 1600 oersted were used.

Example 4 The same process as in Example 1 was performed except that phthalocyanine blue in Example 1 was replaced with benzidine yellow, and a yellow image was reproduced.

Claims (1)

[Claims] 1. A magnetic color toner containing a binder resin, a coloring agent exhibiting red, blue, yellow, orange, or violet color tone, and a magnetic material, in which the magnetic material has an average particle size of 0.02 to 0.05 μ and a coercive force of 1000 μm. A magnetic color toner characterized by containing only 0.001 to 2 wt% of ultrafine magnetic particles produced from Fe--Co metal or Fe--Ni metal, which have a particle diameter of Oersted or higher.