JPH0777827A - Magnetic developer - Google Patents

Abstract

PURPOSE:To obtain an image excellent in reproducibility for fine lines and resolution for printing of characters by using a surface-treated magnetic material, incorporating the magnetic material in a specified range of pts.wt. to polymerizable monomers, and incorporating a release agent in a specified range of pts.wt. to the monomer. CONSTITUTION:This magnetic developer is directly obtd. by suspension polymn. of a monomer compsn. containing at least polymerizable monomers, magnetic material and release agent in a water-base medium. The magnetic material is incorporated by 20-70 pts.wt. calculated as untreated magnetic material to 100 pts.wt. of polymerizable monomers. Namely, if the amt. of the magnetic material is lower than 20 pts.wt., electrification characteristics decrease. If it exceeds 70 pts.wt., the amt. of the magnetic material is so large to decrease electricification property. The amt. of the release agent is 10-40 pts.wt. to 100 pts.wt. of polymerizable monomers. If the amt. of the release agent is lower than 10 pts.wt., the releasing effect of the toner decreases. If it exceeds 40 pts.wt., granulating property of the toner during production decreases and the obtd. toner shows deterioration of blocking property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic developer used in electrophotography, electrostatic printing, electrostatic recording, etc., and more particularly to magnetic ink symbol identification (Magnetic Ink C).
The present invention relates to a magnetic developer suitable for printing characters having magnetism used in a character recognition system.

[0002]

2. Description of the Related Art In an electrophotographic system, a method of exposing a document image and exposing its reflected light to a latent image carrier to obtain a latent image is generally performed. In this method, since the reflected light of the original is directly used as an image signal, the potential of the electrical latent image continuously changes (hereinafter referred to as an analog latent image).

On the other hand, a method has been commercialized in which the reflected light of the original is converted into an electric signal, the signal is processed, and then exposure is performed based on the signal. Compared with the analog latent image method, this method can easily perform high-magnification enlargement and reduction, and can capture the image signal in a computer and output it together with other information.

While it has various uses as described above, if the image signal is handled as analog, the signal amount becomes huge, so the image is divided into pixel units (hereinafter referred to as dots) and the exposure amount is determined for each pixel. Processing is required.

When the latent image is digitized, each dot needs to be developed more accurately as compared with the analog latent image, and thus a developer that can faithfully develop pixels with a high development rate is required. Become.

In an image in which an image and a non-image are repeated dot by dot, the developability of the developer is particularly important. Therefore, when a developer developed as a developer for an analog latent image is diverted to a digital latent image system, development for each dot is insufficient especially in a print pattern in which the image / non-image is repeated every dot. There is a tendency that the dots become small, or the image is not developed at all, and the image density as a whole becomes light or the characters are faint. This phenomenon becomes remarkable in a developer (hereinafter referred to as a magnetic developer) having a magnetic toner containing a magnetic material whose developer charge amount tends to be small.

This is considered to be because the magnetic developer has a portion where the magnetic substance is exposed on the surface of the magnetic toner particle, and the surface that can contribute to charging is reduced. Since the surface exposure amount of the magnetic material changes depending on the amount of the magnetic material contained in one magnetic toner, the distribution of the developer charge amount becomes wider than that of other developers. Therefore, when a magnetic developer is used in a digital latent image system, fading of characters easily occurs due to accumulation of magnetic toner particles having a low triboelectric charge amount in a developing device, and improvement thereof is desired.

Further, in recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their applications have expanded to a wide variety, and under such a background, magnetic ink symbol identification (Magnetic Ink) has been applied as an application field of electrophotographic printers.
k Character Recognition (hereinafter, simply referred to as MICR) A character printer used for a system has been devised.

The MICR system mainly prints information such as issuing bank, amount and account number on checks and bills with magnetic ink, and efficiently sorts and sorts at a clearing house using a magnetic reader. It is a system devised for the purpose. Conventionally, offset printing using magnetic ink has been the mainstream, but business transactions such as personal checks and bills have become more active, and demand for small MICR character printing machines (hereinafter simply referred to as MICR encoders) has increased. is doing.

Conventional small MICR encoders are
The mainstream was the impact printer that applied the thermal transfer method, but in this case most single-function machines that print only MICR characters cannot be used for the production of general documents, and improvements are required. There is.

There is a demand for an electrophotographic printer capable of printing general documents and / or graphics, printing MICR characters, and exhibiting a good MICR recognition rate.

When the electrophotographic printer is applied to the MICR encoder, if the conventionally known magnetic developer is used as it is, the accuracy rate (recognition rate) of the magnetic reading by the MICR reader / sorter is the MICR using the offset printing or the impact printer. Compared with the case of letters, it is extremely low and not practical.

The number of securities printed with MICR characters is M
On average, ICR leaders and sorters pass about 10 times. It is rubbed against the magnetic head at high speed every time the paper is passed for magnetic reading. Therefore, it is necessary that the magnetic developer for printing MICR characters does not fade or fall off due to rubbing.

MICR characters are, for example, ANS (Amer
ican National Standard) x
9.27-198x or JIS C6251-19
There is a standard called E-13B defined in 80. E
The -13B standard consists of numbers from 0 to 9 and four types of symbols, and by combining these, bank codes, branch codes, account numbers, amounts, etc. are printed on securities.

In order to improve the recognition rate by the MICR reader / sorter, it is required that the shape and dimensions of the printed MICR characters are reproduced with high accuracy, and the characters are fine and faithful without being crushed or broken. It is necessary to reproduce it.

In order to achieve a high recognition rate in printing MICR characters by an electrophotographic printer, a magnetic material containing a specific magnetic material having magnetic characteristics different from those of magnetic materials used in conventional magnetic developers. It is necessary to use a developer.

As a measure to solve this, by defining the physical properties of the magnetic substance and the wax, the high developability in a digital machine, the blurring of characters due to rubbing by a leader sorter, etc. are reduced, and the recognition rate is improved. There is a report that makes it possible to obtain quite good results.

However, since all of the above are pulverized toners, the high recognition rate is maintained due to the fact that only a small amount of wax can be added, and the charging due to the magnetic substance coming out on the surface of the toner particles. There are some problems with quantity stability.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic developer which solves the above problems.

That is, the object of the present invention is general and MI.
It is an object of the present invention to provide a magnetic developer which has good triboelectric charging property and excellent reproducibility of fine lines and high developability in CR character printing.

Another object of the present invention is to provide a magnetic developer exhibiting an excellent recognition rate when used for MICR printing using an electrophotographic printer. That is, it is an object of the present invention to provide a magnetic developer having a markedly high magnetic reading recognition rate without causing MICR characters to be dropped or blurred due to rubbing even when passing through a MICR reader / sorter.

[0022]

The present invention can be directly obtained by suspension polymerization of a monomer composition containing at least a polymerizable monomer, a magnetic material and a releasing agent in an aqueous medium. In the magnetic developer, the magnetic substance is a surface-treated magnetic substance,
20 to 70 parts by mass based on 100 parts by mass of the polymerizable monomer, and 10 to 40 parts by mass of the release agent based on 100 parts by mass of the polymerizable monomer. Is.

The developer of the present invention is obtained by a suspension polymerization method. In this suspension polymerization method, droplets of the monomer composition are formed in a dispersion medium having a large polarity of water. The component having a polar group contained in the monomer composition easily exists in the surface layer portion which is the interface with the aqueous phase, and the non-polar component does not exist in the surface layer portion, which is a so-called core / shell structure. By utilizing this characteristic of the manufacturing method, it is possible to add a large amount of a low-melting wax that cannot be used by other pulverization methods.

Furthermore, by surface-treating a magnetic material having high magnetic characteristics, it is possible to have stable charging characteristics without exposing the magnetic material to the surface of the toner particles.

As described above, when the polymerized toner which can encapsulate a large amount of wax and the magnetic substance is not exposed on the surface of the toner particles is used, the wax present in the outermost surface layer of the fixed image is more than the case of the pulverized toner. Since it is also thickly covered, even if the MICR reader / sorter repeatedly passes through the paper, the characters are not scratched or fallen off, and the magnetic head is not contaminated. As a result, a high recognition rate can be maintained. Furthermore, by using a magnetic material that is hydrophobically surface-treated, the magnetic material does not appear on the toner particle surface,
A stable charge amount can be maintained and high developability can be maintained.

The constituent materials of the developer of the present invention will be described in detail below.

As the magnetic material used in the present invention, a substance that is magnetized by being placed in a magnetic field is used. There are powders of ferromagnetic metals such as iron, cobalt and nickel, and compounds such as magnetite and ferrite. . In particular, in the present invention, since the toner is obtained by using the polymerization method, it is necessary to pay attention to the polymerization inhibiting property and the water phase transfer property of the magnetic material.

The magnetic substance in the present invention is 20 to 70 per 100 parts by weight of the polymerizable monomer in terms of an untreated magnetic substance.
Parts by mass, preferably 30 to 60 parts by mass. When the amount is less than 20 parts by mass, the charging property is low, the developability is poor, and the image density is low. If it exceeds 70 parts by mass,
It can be seen that the charging property is deteriorated due to the magnetic substance appearing on the surface of the toner particles due to the excessive amount of the magnetic substance.

In the magnetic material according to the present invention, the residual magnetization σ
r is 12 ≦ σ in a magnetic field of 10,000 Oersted
The case of r ≦ 30 emu / g is preferable, and the case of 14 ≦ σr ≦ 28 emu / g is more preferable.

When the residual magnetization σr is less than 12 emu / g, the MIC when MICR characters are printed.
The recognition rate of the R reader / sorter is lowered, and when general printing is performed, a magnetic developer excellent in fine line reproducibility cannot be obtained.

When the residual magnetization σr exceeds 30 emu / g, the image density is low and the fog is large.
When MICR characters are printed, the recognition rate is remarkably reduced, and even when general printing is performed, the image quality is remarkably low.

In the magnetic material according to the present invention, the coercive force Hc
Is 10,000 ≦ in a magnetic field of 10,000 Oersted.
It is preferable that Hc ≦ 300 oersted,
More preferably, it is in the range of 140 ≦ Hc ≦ 280 oersted.

When the coercive force Hc is less than 130 Oersted, the image density is high, but on the other hand, the fine line reproducibility is poor and the recognition rate is lowered when MICR characters are printed, which is not preferable. . Also, the coercive force Hc is 3
When it exceeds 00, it becomes difficult to uniformly apply the magnetic developer onto the developing sleeve, which is not preferable because the image density is lowered or the density becomes uneven.

According to the study of the present inventor, when the remanent magnetization σr possessed by the magnetic material according to the present invention is shown, the magnetic permeability μ and the electrophotographic characteristics of the magnetic developer correspond well. .

Further, it was also found that the magnetic permeability μ corresponds well to the accuracy rate of reading by the MICR reader / sorter when MICR characters are printed.

In the magnetic material according to the present invention, the magnetic permeability μ is preferably in the range of 2.0 ≦ μ ≦ 4.0, and more preferably 2.5 ≦ μ ≦ 3.8.

When the magnetic permeability μ exceeds 4.0, it is possible to apply the magnetic developer uniformly on the developing sleeve, but the interaction with the permanent magnet in the developing sleeve is weak and the magnetic developing is It becomes difficult to properly control the triboelectric charge amount of the agent, and the toner scattering in the image area increases, resulting in MICR.
When characters are printed, it is not preferable because it causes a reduction in recognition rate.

When the magnetic permeability μ is less than 2.0, the interaction with the permanent magnet in the developing sleeve becomes too strong, and as a result, the triboelectric charge amount of the magnetic developer must be properly controlled. However, the image density is low, the recognition rate when MICR characters are printed is low, and the object of the present invention cannot be achieved.

The surface-treated magnetic material used in the present invention may be any one as long as it is subjected to a hydrophobic treatment with a surface modifier which is a substance that does not inhibit polymerization. Examples of such surface modifiers include silane coupling agents and titanium coupling agents.

In the magnetic developer according to the present invention, the magnetic material contains a silicon element and an aluminum element in order to improve the triboelectric chargeability. Silicon element is S for magnetic material
It is preferable that 0.1 to 1.0 mass% in terms of iO ₂ and 0.1 to 1.0 mass% of aluminum element in terms of Al ₂ O ₃ be contained, and more preferable to be converted to SiO _2. 0.15 to 0.9 mass% of elemental silicon and Al ₂ O ₃
In the case of containing 0.15 to 0.9 mass% of aluminum element. The silicon element and the aluminum element can be added in the step of synthesizing the magnetic material according to the present invention by a wet method and / or after the synthesis, and in the case where a heat oxidation treatment and a heat reduction treatment are further performed after the wet synthesis, It can also be added in stages.

In the magnetic material according to the present invention, when the silicon element converted to SiO ₂ is less than 0.1% by mass, a magnetic developer having a large triboelectric charge amount can be obtained. Since the distribution is wide and the performance changes greatly with long-term use and environmental changes, the object of the present invention cannot be achieved. Similarly, when the silicon element converted to SiO ₂ exceeds 1.0 mass%, the distribution of the triboelectric charge amount becomes narrow, but a magnetic developer having a large triboelectric charge amount cannot be obtained.

If the aluminum element converted to Al ₂ O ₃ is less than 0.1% by mass, a magnetic developer having a large triboelectric charge cannot be obtained. Similarly, A
When the aluminum element calculated as l ₂ O ₃ exceeds 0.1% by mass, a magnetic developer having a large triboelectric charge amount can be obtained, but the toner is developed even in the non-image area on the photoreceptor. As a result, an image with a lot of fog is formed, and the magnetic developer excellent in fine line reproducibility, which is the object of the present invention, cannot be obtained.

In the magnetic material according to the present invention, SiO ₂
The silicon element converted to and the aluminum element converted to Al ₂ O ₃ are preferably contained in a mass ratio of 20/1 to 1/20, and more preferably 10/1 to 1/10. , And more preferably 4/1 to 1 /
4 is contained.

When the mass ratio of the silicon element and the aluminum element is less than 20/1, the effect of increasing the image density due to the inclusion of the aluminum element cannot be obtained. When the content of the element is large, the magnetic material obtained by the wet method during the production of the magnetic material may be heated and may be sintered during the oxidation and reduction, which is not preferable.

Further, the magnetic material according to the present invention has a mean particle size of 0.1 to 0.6 μm. In the present invention, the average particle size of the magnetic substance is determined by taking a sample in a magnified photograph at a magnification of 20,000 using a scanning electron microscope.
It can be determined by randomly measuring the major axis values of 100 to 200 particles and calculating the average value.

The waxes used as the release agent according to the present invention include paraffin / polyolefin waxes and modified products thereof such as oxides and graft-treated products, higher fatty acids, and metal salts thereof; amide waxes. Or ester waxes such as tertiary and / or 4
A polyfunctional polyester compound having a secondary carbon and obtained from a difunctional or higher functional alcohol compound or a carboxylic acid compound, a polyfunctional polyester compound having a primary or / and secondary carbon and obtained from a bifunctional or higher functional alcohol compound or carboxylic acid compound Examples thereof include a monofunctional ester compound having a functional polyester compound and tertiary or / and quaternary carbon.

The content of the releasing agent is 10 to 40 parts by mass, preferably 15 to 30 parts by mass based on 100 parts by mass of the polymerizable monomer.
Parts by mass. When the content of the release agent is less than 10 parts by mass, not only the release effect of the toner deteriorates and the offset resistance also deteriorates, but also the characters may be scratched or come off due to rubbing by a leader / sorter. , The recognition rate will decrease. On the other hand, when the content of the release agent exceeds 40 parts by mass,
The granulation property during production deteriorates, and the blocking property of the obtained toner also deteriorates, which adversely affects the developability.

The melting point of the release agent of the present invention is 30 to 1
It is preferably 50 ° C., more preferably 50 to 10
It is 0 ° C. When the melting point is lower than 30 ° C., the blocking resistance and shape retention of the toner are not sufficient,
When the temperature is higher than ℃, the effect of releasability is not sufficient. The melting point was the temperature of the maximum endothermic peak by DSC.

The polymerizable monomer usable in the polymerized toner according to the present invention includes styrene.o-methylstyrene.m.
-Styrene-based monomers such as methyl styrene, p-methyl styrene, p-methoxy styrene, p-ethyl styrene,
Methyl acrylate / ethyl acrylate / acrylic acid n-
Butyl / isobutyl acrylate / n-propyl acrylate / n-octyl acrylate / dodecyl acrylate / 2-ethylhexyl acrylate / stearyl acrylate /
Acrylic esters such as 2-chloroethyl acrylate and phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n methacrylate
-Octyl / dodecyl methacrylate / methacrylic acid 2-
Examples thereof include methacrylic acid esters such as ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and other monomers such as acrylonitrile, methacrylonitrile, and acrylamide. These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other monomers, from the viewpoint of developing characteristics and durability of the toner.

In the present invention, it is more preferable to add a polymer / copolymer having a polar group as an additive to the monomer system for polymerization. Since the polar polymer / copolymer gathers on the surface layer of the toner particles, it forms a kind of shell-like form and imparts excellent properties such as blocking resistance to the toner particles, while By polymerizing so as to contribute to the improvement of the fixing property with a relatively low molecular weight, a toner satisfying the contradictory requirements of the fixing property and the blocking resistance can be obtained. The polar polymers / copolymers that can be used in the present invention are exemplified below.

Polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate or copolymers with styrene / unsaturated carboxylic acid esters, nitrile monomers such as acrylonitrile, vinyl chloride, etc. Halogen-containing monomers, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and other unsaturated dibasic acids
Unsaturated dibasic acid anhydrides, polymers such as nitro monomers or copolymers with styrene monomers, polyesters,
Epoxy resin etc. are mentioned. In particular, it is preferable to contain a polyester resin, and the core / shell formation is further maintained.

The addition amount of these polar polymers / copolymers is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass.

In the present invention, it is desirable to add a charge control agent to the toner material in order to control the chargeability of the toner. As these charge control agents, among known ones, those having almost no polymerization inhibitory property / water phase transfer property are used. For example, as positive charge control agents, nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, guanidines are used. Derivatives, imidazole derivatives, amine-based and polyamine-based compounds, and the like. As a negative charge control agent, metal-containing salicylic acid-based compounds, metal-containing monoazo-based dye compounds, urea derivatives, styrene-acrylic acid copolymers, styrene-methacrylic Examples thereof include acid copolymers.

The addition amount of these charge control agents is 0.
1 to 10 parts by mass is preferable.

As the polymerization initiator, any suitable polymerization initiator, for example, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1, 1'-azobis (cyclohexane-1-
Carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobis or diazo polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide,
Examples thereof include peroxide-based polymerization initiators such as diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide. These polymerization initiators are preferably added in an amount of 0.5 to 20 parts by weight of the polymerizable monomer, and may be used alone or in combination.

In the present invention, in order to control the molecular weight, known crosslinking agents and chain transfer agents may be added, and the preferable addition amount is 0.001 to 15 parts by mass.

As the additive for imparting various toner characteristics, from the viewpoint of durability in the toner or when added to the toner, the particle diameter is not more than ⅕ of the volume average diameter of the toner particles. Is preferred. The particle size of the additive means the average particle size thereof obtained by observing the surface of the toner particles with an electron microscope. As the additives for imparting these characteristics, for example, the following ones are used.

1) Flowability-imparting agent: metal oxides (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Those subjected to a hydrophobic treatment are more preferable.

2) Abrasives: metal oxides (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitrides (silicon nitride, etc.), carbides (silicon carbide, etc.), metal salts (calcium sulfate, etc.) , Barium sulfate, calcium carbonate, etc.).

3) Lubricants: Fluorine-based resin powders (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), etc.

4) Charge control particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.), carbon black, etc.

These additives are used in an amount of 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the toner particles. These additives are
They may be used alone or in combination.

Any suitable stabilizer is used in the dispersion medium used in the present invention. For example, as an inorganic compound, tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate. , Bentonite, silica, alumina and the like. As an organic compound, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and its salt, starch and the like can be dispersed in an aqueous phase and used.
It is preferable to use 0.2 to 20 parts by mass of these stabilizers with respect to 100 parts by mass of the polymerizable monomer.

When an inorganic compound is used among these stabilizers, a commercially available one may be used as it is, but the inorganic compound may be produced in a dispersion medium in order to obtain fine particles. For example, in the case of tricalcium phosphate, it is advisable to mix the sodium phosphate aqueous solution and the calcium chloride aqueous solution under high stirring.

For fine dispersion of these stabilizers, 0.001 to 0.1 parts by mass of surfactant may be used. This is to promote the desired action of the above dispersion stabilizer, and specific examples thereof include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, and sodium octyl sulfate.
Examples thereof include sodium oleate, sodium laurate, potassium stearate, calcium oleate and the like.

The polymerized toner used in the present invention is obtained by the following method. That is, the release agent in the polymerizable monomer
A magnetic system, charge control agent, polymerization initiator and other additives are added, and the monomer system that has been uniformly dissolved or dispersed by a homogenizer, ultrasonic disperser, etc. is stirred normally in an aqueous phase containing a dispersion stabilizer. Disperse using a machine or homomixer / homogenizer. Granulation is preferably carried out by adjusting the stirring speed and time so that the monomer droplets have a desired toner particle size, generally 30 μm or less. After that, stirring may be performed to the extent that the particle state is maintained and the particles are prevented from settling due to the action of the dispersion stabilizer. The polymerization temperature is set to 40 ° C. or higher, generally 50 to 90 ° C. to carry out the polymerization. Further, the temperature may be raised in the latter half of the polymerization reaction, and further in the latter half of the reaction in order to remove unreacted polymerizable monomer, by-product, etc. which may cause odor during toner fixing,
Alternatively, the aqueous medium may be partially distilled off after completion of the reaction. After the reaction is completed, the produced toner particles are collected by washing and filtration and dried. In the suspension polymerization method, usually monomer system 1
It is preferable to use 300 to 3000 parts by mass of water as a dispersion medium with respect to 00 parts by mass.

[0067]

EXAMPLES The present invention will be described in more detail based on the following examples.

First, an example of producing a magnetic material will be described, then an example of surface treatment of the magnetic material will be described, and then an example will be described.

<Production Example of Magnetic Material> Ferrous sulfate was used as a raw material, and a magnetic material synthesized by a wet synthesis method in which an oxidation reaction was performed in an aqueous solution was used as a raw material. First, air was aerated at 750 ° C. for 2 hours. To produce α-Fe ₂ O ₃ .
Next, after the temperature was set to 350 ° C., a gas obtained by mixing hydrogen gas and nitrogen gas was passed through for 3 hours to obtain a magnetic material according to the present invention.

The physical properties of this magnetic material are 10,000.
Remanent magnetization σr in the Oersted magnetic field is 17.9e
mu / g, coercive force Hc is 203 oersted, magnetic permeability μ
Was 3.5, the average particle size was 0.26 μm, the silicon element was 0.26 mass% in terms of SiO ₂ , and the aluminum element was 0.74 mass% in terms of Al ₂ O ₃ .

<Production Example 1 of surface-treated magnetic material> 2 g of isopropyl tris (dioctyl pyrophosphate) titanate as a titanium compound was dissolved in 300 g of toluene and immersed in 200 g of the above magnetic material particles, and then stirred at 80 ° C. It was heated and the solvent was distilled off. The obtained surface-treated magnetic material was further heat-treated at 80 ° C. or higher for 2 hours to remove the solvent and reaction by-products, and dried to obtain 199 g of treated magnetic particles.

<Production Example 2 of surface-treated magnetic material> 250 g of the above-mentioned magnetic material particles and 40 g of vinyltrimethoxysilane were put in separate containers, and 320 mmH in the same desiccator.
It was left under reduced pressure at 75 ° C. for 3 hours. Then, the magnetic particles were left in a vacuum drier under reduced pressure at 50 ° C. for 2 hours and dried to obtain 250 g of treated magnetic particles.

The present invention will be specifically described below based on Examples and Comparative Examples.

Example 1 To 720 g of ion-exchanged water, 445 g of 0.1 M Na ₃ PO ₄ aqueous solution was added, and after heating to 60 ° C., 1.0 M-
67.0 g of CaCl ₂ aqueous solution was gradually added to Ca ₃
An aqueous medium containing (PO ₄ ) ₂ was obtained.

Styrene 182 g n-Butyl acrylate 18 g Surface-treated magnetic material of Production Example 1 90 g Styrene-methacrylic acid-methyl methacrylate copolymer 7 g Copolymerization ratio (83: 7: 10), molecular weight (Mw = 53,000) Paraffin wax (mp. 70 ° C) 60 g Di-t-butylsalicylic acid metal compound 4 g

The above formulation was heated to 60 ° C. and 11,000 rpm using a TK type homomixer (made by Tokushu Kika Kogyo).
Was evenly dispersed and dissolved. In addition to this, the polymerization initiator 2,
2'-azobis (2,4-dimethylvaleronitrile)
[T1 / 2 = 140 minutes (under 60 ° C)] 10 g, and dimethyl-2,2'-azobisisobutyrate [t1 / 2 = 1,
270 minutes (under 60 ° C), t1 / 2 = 80 minutes (under 80 ° C)]
1 g was dissolved to prepare a polymerizable monomer system.

The above polymerizable monomer system was charged into the above aqueous medium and stirred at 60 ° C. in a N ₂ atmosphere with a TK homomixer at 10,000 rpm for 20 minutes to form suspension particles of toner particle size. Granulated. Then, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. The polymerization conversion rate at this point was 90%. Then, the reflux of water vapor was stopped, the liquid temperature was raised to 80 ° C., and stirring was continued for 10 hours. After the reaction was completed, the suspension was cooled, hydrochloric acid was added, and Ca
By dissolving ₃ (PO ₄ ) ₂ and filtering and drying,
A polymerized toner was obtained.

BET is added to 100 parts by weight of this toner.
0.6 part by mass of hydrophobic silica having a specific surface area of 205 m ² / g according to the method was externally added. A developer was prepared by mixing 94 parts by mass of a ferrite carrier coated with an acrylic resin with 6 parts by mass of the externally added toner.

When the above developer was imaged using a laser beam printer LBP-8 manufactured by Canon Inc., an image excellent in fine line reproducibility and resolution was obtained. Also, J
MICR as described in ISC 6251-1980
Characters were printed on 1300 sheets. This 1300 sheets of printed material are commercially available MICR reader / sorter (3 manufactured by IBM).
890 type machine), there was no character loss or scratching due to rubbing, and the recognition rate for magnetic reading was 99.9%.

Example 2 Styrene 180 g n-Butyl acrylate 20 g Surface-treated magnetic material of Production Example 105 g Styrene-methacrylic acid-methyl methacrylate copolymer 8 g Copolymerization ratio (85: 5: 10), molecular weight (Mw = 58) , 000) Di-t-butylsalicylic acid metal compound 5 g Ester wax having the following structural formula 60 g

[0081]

[Chemical 1] A polymerized toner was obtained in the same formulation as in Example 1 except that the polymerizable composition consisting of was used, and a developer was further prepared.

When the above developer was imaged using a laser beam printer LBP-8 manufactured by Canon, an image having remarkably excellent fine line reproducibility and resolution was obtained.
1300 sheets of MICR characters were printed according to the description of SC 6251-1980. A commercially available MICR reader / sorter (manufactured by IBM Corp. 38
When using a 90-type machine), there was no character loss or blurring due to rubbing, and the recognition rate for magnetic reading was 99.9%.

Example 3 Styrene 179 g n-Butyl acrylate 21 g Surface-treated magnetic material of Production Example 104 g Styrene-methacrylic acid-methyl methacrylate copolymer 8 g Copolymerization ratio (85: 5: 10), molecular weight (Mw = 58) Microcrystalline wax (mp. 70 ° C) 22 g Di-t-butylsalicylic acid metal compound 4 g A polymerized toner was prepared in the same manner as in Example 1 except that a polymerizable composition was used. Prepared.

When the above developer was imaged using a laser beam printer LBP-8 manufactured by Canon, an image having remarkably excellent fine line reproducibility and resolution was obtained, and MI
When 1000 sheets of CR characters were printed and the 1000 sheets of printed matter were used with a commercially available MICR reader / sorter, the letters were not dropped or scratched by rubbing and the recognition rate was 9
It was 9.1%.

Example 4 Styrene 184 g n-Butyl acrylate 16 g Surface-treated magnetic substance of Production Example 46 g Styrene-methacrylic acid-methyl methacrylate copolymer 9 g Copolymerization ratio (85: 5: 10), molecular weight (Mw = 58) Paraffin wax (mp. 80 ° C.) 40 g Polymerized toner was prepared in the same manner as in Example 1 except that a polymerizable composition consisting of 3 g of metal compound di-t-butylsalicylate was used to prepare a developer. did.

When the above developer was imaged using a Canon laser beam printer LBP-8, an image with excellent fine line reproducibility and resolution was obtained, and 1200 MICR characters were printed. When a commercially available MICR reader / sorter was used for the printed matter, there was no character loss or blurring due to rubbing, and the recognition rate was 99.3%.
Met.

Comparative Example 1 Styrene-butyl acrylate copolymer 100 g Monoazo dye chromium complex 0.5 g Paraffin wax 5 g The magnetic material (untreated) 60 g

The above composition was melted, kneaded, cooled and crushed to obtain a crushed toner, and a developer was prepared in the same manner as in Example 1.

When the above developer was imaged using a Canon laser beam printer LBP-8, an image with excellent fine line reproducibility and resolution was obtained, and 1000 sheets of MICR characters were printed. When a commercially available MICR reader / sorter was used for the printed matter, there was no character loss or scratching due to rubbing, and the recognition rate was 95.4%.
Met.

Comparative Example 2 Styrene 182 g n-Butyl acrylate 18 g Surface-treated magnetic material of Production Example 128 g Styrene-methacrylic acid-methyl methacrylate copolymer 6 g Copolymerization ratio (85: 5: 10), molecular weight (Mw = 58) Paraffin wax (mp. 70 ° C.) 4 g Polymerized toner was prepared in the same manner as in Example 1 except that a polymerizable composition consisting of 5 g of metal compound di-t-butylsalicylate was used to prepare a developer. did.

When the above developer was imaged using a laser beam printer LBP-8 manufactured by Canon, an image with excellent fine line reproducibility and resolution was obtained.
When 100 sheets of characters were printed and a commercially available MICR reader / sorter was used for these 100 sheets of printed matter, the letters were often dropped or scratched by rubbing, and the magnetic head was stained, resulting in a recognition rate of 38.1%. Met.

Comparative Example 3 Styrene 181 g n-Butyl acrylate 19 g Surface-treated magnetic material of Production Example 16 g Styrene-methacrylic acid-methyl methacrylate copolymer 5 g Copolymerization ratio (85: 5: 10), molecular weight (Mw = 58) Microcrystalline wax (mp. 80 ° C.) 26 g Polymerized toner was prepared in the same manner as in Example 1 except that a polymerizable composition consisting of 5 g of metal compound di-t-butylsalicylate was used. Prepared.

When the above developer was imaged using a laser beam printer LBP-8 manufactured by Canon, an image with remarkably poor reproducibility of fine lines and resolution was obtained.
When 500 characters of R characters were printed and a commercially available MICR reader / sorter was used for the printed characters of 500 characters, the characters were dropped or scratched by rubbing, and the recognition rate was 59.7%.
Met.

The above results are shown in Table 1.

[0095]

[Table 1]

[0096]

According to the present invention, not only an image having excellent fine line reproducibility and resolution can be obtained in printing of general characters, but also when the magnetic developer of the present invention is installed in the MICR system, MICR characters In the printing of, an image with excellent fine line reproducibility and resolution can be obtained, and further, there is no problem of character fainting or dropping due to rubbing by a reader / sorter, and a remarkably high recognition rate can be obtained.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G03G 9/08 384 (72) Inventor Takehiko Chiba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kasuya Rare 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Satoshi Matsunaga 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. A developer obtained directly by suspension polymerization of a monomer composition containing at least a polymerizable monomer, a magnetic material and a release agent in an aqueous medium, wherein the magnetic material is surface-treated. It is a magnetic substance and has 100 polymerizable monomers.
20 to 70 parts by mass based on 100 parts by mass of the polymerizable monomer, and 10 to 40 parts by mass of the release agent based on 100 parts by mass of the polymerizable monomer. 2. The magnetic developer is used for printing characters used in a magnetic ink symbol identification system for reading information by magnetic characters using a magnetic reader. 1. The magnetic developer according to 1. 3. The surface-treated magnetic material contains silicon element and aluminum element and has a residual magnetization σr of 12 ≦ σr ≦ 30 emu / g in a magnetic field of 10,000 Oersted.
And the coercive force Hc in a magnetic field of 10,000 Oersted is in the range of 130 ≦ Hc ≦ 300 Oersted, and the magnetic permeability μ is in the range of 2.0 ≦ μ ≦ 4.0. The magnetic developer according to claim 1.