JPH07271089A - Magnetic developer and image forming method - Google Patents

Abstract

PURPOSE:To obtain a magnetic developer improving consumption, having satisfactory preservability even in an environment at high temp. and humidity and capable of giving an image maintaining sufficiently high image density, free from fog and tailing and having high blackness with high resolution and high definition reproducibility. CONSTITUTION:In this magnetic developer with magnetic toner particles contg. at least a bonding resin and a magnetic substance, the magnetic substance contains 2-20 mass % trivalent metal other than iron, has 20-50Am<2>/kg saturation magnetization sigmas in 79.58kA/m magnetic field and has been made hydrophobic by treatment with an org. compd. having a hydrophobic group.

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 recording, magnetic recording and the like, and an image forming method using the magnetic developer.

[0002]

2. Description of the Related Art Conventionally, a number of electrophotographic methods are known, but generally, a photoconductive material is used to form an electric latent image on a photoconductor by various means, and then the electrophotographic image is formed. The latent image is developed with a developer to make it a visible image, and if necessary, the developer image is transferred to a transfer material such as paper, and then the developer image is fixed on the transfer material by heat or pressure to make a copy. You get what you get.

In recent years, in addition to conventional copying machines, there have been many printers, facsimile machines, and the like using electrophotographic methods. Particularly in printers and facsimiles, a developing device using a one-component developer is often used because it is necessary to reduce the size of the copying device.

Unlike the two-component system, the one-component developing system does not require carrier particles such as glass beads and iron powder, so that the developing device itself can be made compact and lightweight. Furthermore, in the two-component development method, it is necessary to keep the toner concentration in the developer constant,
There is a need for a device that detects the developer concentration and replenishes the required amount of toner. Therefore, also in this case, the developing device becomes large and heavy. Such a device is not necessary in the one-component developing system, and it is preferable because it can be made small and light.

In addition, LED and LBP printers have become the mainstream of the market in recent years as the printer apparatus, and the direction of technology is higher resolution, that is, 400, 600, 800 dpi instead of 240, 300 dpi in the past. ing. Therefore, the developing system is also required to have higher definition. Further, the functions of copiers are also becoming more sophisticated, and as a result, they are moving toward digitalization. In this direction, the method of forming an electrostatic charge image with a laser is the main method, so it is also advancing toward high resolution, and here too, as with printers, high resolution and high definition development methods are required. , JP-A-1-112253, JP-A-2
A developer having a small particle size is proposed in, for example, -284158.

Further, in the copying machine, higher speed and stable downward direction are always desired. Especially for medium speed machines and high speed machines, the two-component developing method is the mainstream. This is because, with such a relatively large machine, the stability for long-term use at high speed becomes more important than the problem of the size and weight of the developing device. In general, the toner of the two-component developer is colored with carbon black or the like, and the rest is composed of a polymer. For this reason, the toner particles are light and have no force other than electrostatic force to adhere to the carrier particles, so that the toner is scattered especially at high-speed development, and the lens, the original glass, the transport part, etc. are contaminated over a long period of time, resulting in image deterioration. May impair stability. Therefore, a two-component developer has been put into practical use in which a magnetic substance is contained in the toner to make the developer heavy, and at the same time, magnetic particles are attached to the magnetic carrier particles in addition to electrostatic force to prevent scattering.

As described above, the developer containing the magnetic material is becoming more and more important.

By the way, in the one-component magnetic development system, since the developer is developed into a chain (generally called "brush") at the time of development, the resolution in the horizontal direction of the image is higher than that in the vertical direction. It is easy to get worse. For example, the tailing phenomenon due to the protrusion of the ears is likely to occur in the non-image portion in the latter half of the developed image, and a rough image tends to be produced as compared with the two-component developing method. Therefore, as a method of further improving the image reproducibility, it is conceivable to make the ears of the magnetic developer shorter and denser. As a means therefor, it is considered to reduce the amount of magnetic material in the developer or to bring the developer layer thickness controlling agent into strong contact with the developer carrier. However, for example, when the amount of the magnetic material is reduced, the charge amount of the developer is generally excessive, which causes a so-called charge-up phenomenon, which results in deterioration of image quality such as reduction in image density and increase in fog. The relationship between the magnetic strength of the magnetic developer and the shape of the spikes is also qualitatively understood as follows. That is, when the magnetization intensity of the magnetic developer is large, a strong attractive force along the magnetic field direction and a strong repulsive force in the direction perpendicular to the magnetic field are generated between the magnetic developer particles. Therefore, when the intensity of magnetization is high, the ears formed by the magnetic developer are long and the ears on the developer carrier have a low density, and the individual ears are thin. On the contrary, when the magnetic developer has a low magnetization strength, the ears are short and the ears on the developer carrier become denser, but the bonds between the magnetic developer particles cannot be released. The panicles become thick and short, and become aggregated. In this case, the magnetic developer particles present inside the ears are less likely to come into contact with the surface of the developer carrier, resulting in poor charging. Such developer particles that are not properly charged cause fog on the image and deteriorate the image quality.
Further, when the developer becomes fine particles (generally 9 μm or less),
The developer charge-up phenomenon due to the reduction of the magnetic substance is likely to occur, and the charged developer or the fine powder developer is strongly adhered to the developer carrier by the force such as the mirroring force, which causes a decrease in the image density. . Further, when the developer layer thickness regulating member is strongly brought into contact with the developer carrier, there are problems such as wear of the developer layer thickness regulating member and an increase in driving load, which is not preferable.

Further, as a means for making the spikes of the magnetic developer shorter and denser, a method of lowering the saturation magnetization s of the developer can be considered. As a method for reducing the saturation magnetization σs of the developer, JP-A-3-197697, 4-184354.
JP-A No. 4-223487 and JP-A No. 4-223487 propose a method in which the divalent iron of magnetite is replaced with a divalent metal such as zinc or copper to contain a partially ferritic magnetic material or a needle-like magnetic material. Has been done. However, the method of making ferrite has the drawback that the divalent iron of magnetite is reduced, and as the saturation magnetization is lowered, the magnetic substance becomes reddish and the blackness is lowered. Further, in the method using a needle-shaped magnetic material, it is difficult to obtain sufficient image density because it obstructs the charging property of the developer and the coercive force becomes too high. In addition, since magnetic developer is generally used by dispersing fine powder of magnetic material in a binder resin, problems such as decrease in image density due to long-term use in high temperature and high humidity environment and storage tend to occur. Met.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic developer and an image forming method which solve the above-mentioned problems of the prior art.

That is, the object of the present invention is to adhere to the original,
It is an object of the present invention to provide a high-resolution, high-definition reproducible magnetic developer that is faithful to signals, that is, substantially free from fog, which is true to latent images, and developer tailing, and an image forming method.

Further, an object of the present invention is to provide a magnetic developer and an image forming method which have good blackness and can obtain a high quality image.

Further, an object of the present invention is to provide a magnetic developer and an image forming method which consume less developer as compared with the conventional one.

Further, an object of the present invention is to provide a magnetic developer and an image forming method which are excellent in environmental stability and can obtain a good image especially when stored and used in a high humidity environment. is there.

[0015]

The present invention achieves the above object by the following constitutions.

The present invention provides a magnetic developer having magnetic toner particles containing at least a binder resin and a magnetic substance, wherein the magnetic substance contains 2% by mass to 2% by weight of a trivalent metal other than iron.
Contains 0 mass% and 79.58 kA / m (1 kOe)
The saturation magnetization σs in the magnetic field of 20 to 50 Am ² / k
g (emu / g) and the magnetic material is subjected to a hydrophobic treatment with an organic compound having a hydrophobic group, and relates to a magnetic developer.

Further, according to the present invention, the electrostatic latent image carrier and the developer carrier are arranged in the developing section with a certain gap, and the magnetic developer is disposed on the developer carrier. In an image forming method in which the latent image on the electrostatic latent image bearing member is developed by transporting to a developing unit with a further reduced thickness and applying an alternating electric field in the developing unit, the magnetic developer is A magnetic developer having magnetic toner particles containing at least a binder resin and a magnetic substance, the magnetic substance containing 2 to 20% by mass of a trivalent metal other than iron, and 79.58 kA / m (1 kO
e) the saturation magnetization σs in the magnetic field is 20 to 50 Am ²
/ Kg (emu / g) and the magnetic material is subjected to a hydrophobic treatment.

The chromaticity of the magnetic developer having the magnetic toner particles containing the above-mentioned specific magnetic material of the present invention preferably satisfies the following conditions: -1.0≤a ^* ≤0.8, -3.0≤b. ^It is better to satisfy ^* ≦ 0, and more preferably the following condition 13 ≦ L ^* ≦ 23, −0.8 ≦ a ^* ≦ 0.6, −0.3 ≦
It is better to satisfy b ^* ≦ 0. (Where a ^* is the chromaticity in the red-green direction in the (L ^* a ^* b ^* ) uniform perceptual color space, and b ^* is yellow-
Chromaticity in the blue direction is shown, and L ^* is lightness. )

When a ^* or b ^* is not within the above range,
The color becomes reddish or bluish, which is not preferable as a black developer. Further, when L ^* is larger than 23, the coloring power of the developer is insufficient, and a sufficient image density cannot be obtained particularly in a solid portion, or more development is required to obtain a sufficient image density. Agents are needed. Conversely, L
^{When *} is less than 13, the coloring power of the developer is excessive and slight scattering and fogging become noticeable.

Conventionally, as a means for reducing the amount of magnetization of a magnetic material, a material doped with a divalent metal such as Zn or Mn has been used. However, this method is a method of making magnetite into a ferrite, and inevitably reduces the divalent iron in the magnetite, resulting in particles having a reddish black color and insufficient blackness of the image.

The magnetic developer of the present invention is one in which part or all of the trivalent iron in magnetite is replaced with a trivalent different metal, and since FeO is not reduced, blackness is not impaired and is high. A black developer image is obtained.

As an example of using a magnetic substance containing a trivalent metal other than iron, Japanese Patent Laid-Open Nos. 58-91463 and 4-190242 disclose magnetic substances containing aluminum. However, in these, aluminum exists on or near the surface of the magnetic body, and the saturation magnetization σs of the magnetic body is 79.
60 to 65 A in a magnetic field of 58 kA / m (1 kOe)
Since it is m ² / kg (emu / g), the effect of improving tailing as in the present invention cannot be obtained.

The saturation magnetization σs of the magnetic material contained in the magnetic developer of the present invention in a magnetic field of 79.58 kA / m (1 kOe) is 20 to 50 Am ² / kg (emu / g), preferably 25 to 45 Am ² / kg (emu / g)
Good to be.

If σs is less than ²⁰ Am ² / kg (emu / g), defects such as missing images due to insufficient supply of the developer are likely to occur due to insufficient magnetic transportability of the developer.
The means for preventing this involves an increase in cost and inevitably complicates the configuration. If it is attempted to supplement the magnetic transportability by increasing the amount of magnetic material with respect to the binder resin, the charging property and fixing property will be deteriorated. Conversely, 50 Am ² / kg (em
If it exceeds u / g), it is necessary to reduce the amount of the magnetic material relative to the binder resin in order to reduce the amount of developer consumed, and the charge amount becomes too high and the density tends to decrease.

Further, the magnetic substance used in the present invention is F
The eO content is preferably 18% by mass or more, and more preferably 19% by mass or more.

If the FeO content is less than 18% by mass, the blackness of the low σs magnetic material is not sufficient.

Further, the divalent iron element (F
The content of e ²⁺ ) is preferably 12% by mass to 23% by mass, and the ratio of the contents of divalent iron element and trivalent iron element (Fe
^{2 +} / Fe3 ⁺ ) is preferably 0.256 to 0.543.

The amount of the different metal which is a trivalent metal other than iron contained in the magnetic substance is 2% by mass to 20% by mass,
It is preferably 3% by mass to 15% by mass. The foreign metal (trivalent) contained in the magnetic substance may exist in the form of hydroxide or hydrous oxide on or near the surface of the magnetic substance, but 2% by mass in the crystal lattice of the magnetic substance. It is preferable that a different metal (trivalent) is contained in an amount of 10 to 10% by mass, and more preferably 3 to 6% by mass.

If the amount of the trivalent foreign metal other than iron contained in the magnetic material is less than 2% by mass, it is difficult to balance the blackness and σs.

The magnetic substance contained in the magnetic developer of the present invention is an unprecedented low σs high blackness magnetic substance in which part or all of the trivalent iron of magnetite is replaced with a trivalent different metal. Although various metals can be used as the trivalent metal, aluminum is preferable among them. In addition, divalent iron is added to manganese, zinc, as long as blackness is not deteriorated.
Substitution with a divalent metal such as cobalt or copper is also a preferable form for controlling the magnetic properties. Moreover, you may contain the other metal element in the range which does not affect.

The shape of the magnetic material is octahedron, hexahedron,
There are spheres, needles, flakes, etc., but those having little anisotropy such as octahedron, hexahedron, and sphere are preferable. The average particle diameter of the magnetic material is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.6 μm, and further 0.1 to 0.
4 μm is preferable. Further, these magnetic particles are preferably magnetic powder having a Mohs hardness of 5 to 7.

The amount of magnetic material is 5 with respect to 100 parts by mass of the binder resin.
0 to 200 parts by mass, particularly 60 to 150 parts by mass are preferred. If the amount is less than 50 parts by mass, the transportability is insufficient and the developer layer on the developer carrying member tends to be uneven, resulting in image unevenness.
Further, the image density tends to decrease due to the increase in developer tribo.

On the other hand, if the amount exceeds 200 parts by mass, the fixing property tends to be problematic.

The weight average particle diameter of the magnetic developer having the magnetic toner particles of the present invention is preferably 4 to 10 μm in order to obtain good image quality. When the weight average particle diameter is less than 4 μm, the developer is remarkably aggregated, which causes problems in developer productivity (eg, filling step) and handling. If it exceeds 10 μm, the dot latent image or fine line of 100 μm or less is not sufficiently reproduced.

The weight average particle diameter of the magnetic developer of the present invention is D
(Μm), 79.58 kA / m (1 kO of magnetic developer)
e) the saturation magnetization in the magnetic field is M (Am ² / kg (e
mu / g)), and the density of the magnetic developer particles is γ (g / c)
m ³ ), the value S of each product (D × M × γ)
Is preferably 120 to 340.

When the value of S is less than 120, the image is easily fogged, and the magnetic transport force in the developing device is insufficient. The phenomenon that parts come out white occurs. If it exceeds 340, the reduction in consumption is not sufficient.

The present inventors have paid attention to the “line image” which occupies most of the general image. Generally, more developer is developed in the line image area than in the solid image area, and if an attempt is made to maintain a sufficient image density in the solid image area, excess developer is developed in the line image area, It is a shackle for reducing developer consumption. As a result of studying to prevent excessive development of the developer on the line image area while keeping the image density of the solid image area sufficiently, as a result of containing trivalent metal other than iron, 79.58 kA / m (1 kOe ), The saturation magnetization σs in the magnetic field is 20 to 50 Am ² / kg (em
u / g), the amount of the developer developed in the line image area is small when the product of the weight average particle diameter of the magnetic developer, the saturation magnetization amount and the density is within the above range. It was found that the developer consumption can be reduced. The decrease in the amount of developer developed in the line image area is not due to the line image becoming thinner than the conventional magnetic developer, but the conventional developer is the lowest in forming a line image in the line image area. This is because the amount of the developer placed in the vertical direction of the line was more than the required amount, but the developer of the present invention had an appropriate amount and the height of the line was lowered.

The value of S is preferably in the range of 140 to 320, more preferably 180 to 300.

The reason why a larger amount of developer is generally developed in the line image area than in the solid image area is considered as follows. In the electrostatic latent image of the line image portion on the photoconductor, unlike the solid image portion, the lines of electric force are closely wrapped around the line latent image from the outside of the line latent image. A large amount of the developer is easily developed on the line latent image surface because the developer is strongly attracted and pressed against the latent image surface of the photoconductor.

The reason why the magnetic developer of the present invention has a smaller amount of developer on the line image portion than the conventional developer and the developer consumption can be reduced is considered as follows.

In the one-component developing method using a magnetic developer, the developer is developed on the surface of the photoconductor in a state of being aggregated to some extent. The magnetic developer of the present invention has a value of S smaller than that of the conventional magnetic developer, and the magnetic cohesive force acting between the magnetic toner particles contained in the developer is larger than that of the conventional magnetic developer. Considered small. Therefore, in the developer particles once developed in the line image portion on the photoconductor, unnecessary particles have a small agglomeration between the developer particles, and therefore resist the force due to the wraparound of the latent image electric force lines, We believe that only the proper amount of developer can remain on the line image area after returning to the sleeve.

Specific examples of the hydrophobic treatment of the magnetic material used in the present invention include silane coupling agents, titanium coupling agents or animal oils, vegetable oils, general-purpose surfactants, petroleum lubricating oils, synthetic lubricating oils, etc. Dissolve the hydrophobic liquid in an organic solvent such as toluene or xylene, mix and stir while gradually adding the magnetic substance into it, and then remove the solvent by filtration or the like to form a hydrophobic treatment agent layer on the magnetic substance surface. How to form. Alternatively, a method of adsorbing the treatment agent on the surface of the magnetic material by mixing with a dry mixer may be used. Among them, animal oils, vegetable oils, general-purpose surfactants, petroleum-based lubricating oils, synthetic lubricating oils and other hydrophobic liquids are stirred, compressed,
A preferable method is a method of directly supporting on a magnetic body by a shearing action or a spatula action.

A wheel-type kneading machine or a ladle machine is used as a specific method for supporting the hydrophobic liquid on the surface of the magnetic material. When a wheel type kneader or a raider is used, the hydrophobic liquid present between the magnetic particles is pressed against the surface of the magnetic particles by a compression action, and the particles are spread by passing through the gaps between the magnetic particles. Increases the adhesion to the surface and stretches the hydrophobic liquid by shearing action, while changing the position with respect to the magnetic particle group by shearing force to loosen and disaggregate the aggregates. By spreading the existing hydrophobic liquid uniformly, by repeating the above three actions, the agglomeration between the magnetic particles is sometimes loosened, and the surface of each magnetic particle is evenly distributed. It is particularly preferable because it is highly hydrophobicized. As the wheel type kneading machine, Simpson Mix Mahler, Marutimaru, Stotsmill, Eyrich Mill, and countercurrent kneading machine can be preferably used.

Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane and vinyltris (β-methoxyethoxy).
Silane and the like, as the titanium-based coupling agent,
Examples include isopropritriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyl tris (dioctylpyrophosphate) titanate, bis (dioctylpyrophosphate) oxyacetate titanate, bis (dioctylpyrophosphate) ethylene titanate, and the like.

Animal oil, vegetable oil, general-purpose surfactant,
As the hydrophobic liquid such as petroleum-based lubricating oil and synthetic lubricating oil, synthetic lubricating oil is preferably used from the viewpoint of environmental stability of the developer.

Examples of synthetic lubricating oils include silicones such as dimethyl silicone, methylphenyl silicone, and various modified silicones. Polyol esters such as pentaerythritol ester and trimethylolpropane ester. Polyolefins such as polyethylene, polypropylene, polybutene and poly α-olefins. Polyglycols such as polyethylene glycol and polypropylene glycol. Silicate esters such as tetradecyl silicate and tetraoctyl silicate. Di-2-ethylhexyl sebacate,
Diesters such as di-2-ethylhexyl adipate. Phosphoric acid esters such as trikeresyl phosphate and propylphenyl phosphate. Examples thereof include fluorohydrocarbon compounds such as polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinylidene fluoride, and polyfluoroethylene, polyphenyl ethers, alkyl naphthenes, and alkyl aromatics. Among them, silicone and fluorohydrocarbon are preferable from the viewpoint of thermal stability and oxidation stability. As silicone, amino-modified, epoxy-modified, carboxyl-modified, carbinol-modified, methacryl-modified, mercapto-modified, phenol-modified, different functional group-modified reactive silicone, polyether-modified, methylstyryl-modified, alkyl-modified, fatty acid-modified , Non-reactive silicones such as alicoxy modified and fluorine modified, straight silicones such as dimethyl silicone, methylphenyl silicone and methyl hydrogen silicone are used. The hydrophobic liquid used in the present invention has a viscosity at 25 ° C. of 10 to 200.
It is preferably 000 cSt, more preferably 20.
~ 100,000 cSt, especially 50-70000 cSt
Is good. If it is less than 10 cSt, the amount of low-molecular-weight components increases, and problems with developability and storability tend to occur. On the other hand, when it exceeds 200,000 cSt, problems tend to occur in the uniformity of the hydrophobic treatment and the like.

The viscosity of the hydrophobic liquid in the present invention is measured by
This is performed using a Bisco Tester VT500 (manufactured by Haake). One of several viscosity sensors for VT500 is arbitrarily selected, and the measurement material is put in the cell for the sensor for measurement. Viscosity (pas) displayed on the device is cSt
Convert to.

The addition amount of the hydrophobizing agent in the present invention is not uniquely determined by the particle shape of the magnetic powder to be treated, the particle size, the physical properties of the hydrophobizing agent, etc. 0.01 to 20 parts by weight per 100 parts by weight,
It is preferable to use 0.02 to 10 parts by mass, particularly 0.1 to 5 parts by mass.

Examples of the binder resin used in the present invention include homopolymers of styrene and its substitution products such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers and styrene-vinyltoluene. Copolymers, styrene-vinyl naphthalene copolymers, styrene-acrylic acid ester copolymers, styrene-methacrylic acid ester copolymers, styrene-α-chloromethyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene- Styrene such as vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer System Combined; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin , Polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin and the like can be used. A crosslinked styrene resin is also a preferable binder resin.

Examples of the comonomer for the styrene monomer of the styrene type copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
Didecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc. A monocarboxylic acid having a heavy bond or a substituted product thereof;
For example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, and the like; and substituted compounds thereof; for example, vinyl chloride,
Vinyl esters such as vinyl acetate, vinyl benzoate, etc., ethylene-based olefins such as ethylene, propylene, butylene, etc .; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc .;
For example, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and the like; and vinyl monomers such as are used alone or in combination.

As the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used. For example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate. , Ethylene glycol dimethacrylate,
Carboxylic acid ester having two double bonds such as 1,3-butanediol dimethacrylate; Divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and compound having 3 or more vinyl groups Can be used alone or as a mixture.

In the bulk polymerization method, it is possible to obtain a low molecular weight polymer by increasing the termination reaction rate by polymerizing at a high temperature, but there is a problem that the reaction is difficult to control. In the solution polymerization method, a low molecular weight polymer can be easily obtained under mild conditions by utilizing the difference in radical chain transfer depending on the solvent and by adjusting the amount of the initiator and the reaction temperature. It is preferable when a low molecular weight product is obtained in the composition.

As the solvent used in the solution polymerization, xylene, toluene, cumene, cellosolve acetate, isopropyl alcohol, benzene and the like can be used. In the case of a styrene monomer mixture, xylene, toluene or cumene are preferred. It is appropriately selected depending on the polymer to be polymerized.

As the binder resin for the developer used for pressure fixing, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, higher fatty acid, Polyamide resin and polyester resin can be used. These are preferably used alone or in combination.

Further, from the viewpoint of improving the releasability from the fixing member at the time of fixing and the fixing property, it is also preferable to include the following waxes in the developer. Paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, carnauba wax and its derivatives, etc., which are block copolymers with oxides and vinyl monomers. And graft modified products.

In addition, alcohols, fatty acids, acid amides,
Esters, ketones, hydrogenated castor oil and its derivatives, plant waxes, animal waxes, mineral waxes, petrolactam and the like can also be used.

In the magnetic developer of the present invention, a charge control agent is blended with developer particles (internal addition) or mixed with developer particles (external addition).
It is preferable because it can be used. The charge control agent makes it possible to control the optimum charge amount according to the developing system, and particularly in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge amount. Examples of materials that control the developer to be negatively charged include the following substances.

Organic metal complexes and chelate compounds are effective, for example, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol. Further, the following substances are exemplified as those which are controlled to be positively charged.

Modified products of nigrosine and fatty acid metal salts and the like; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and phosphonium salts which are analogs thereof. Onium salts such as and lake pigments thereof, triphenylmethane dyes and lake pigments thereof (as a laker, phosphotungstic acid, phosphomolybdic acid, phosphotungstic molybdic acid, tannic acid, lauric acid, gallic acid, ferricia Metal compounds of higher fatty acids; dibutyltin oxide, dioctyltin oxide, dicyclotintin oxide and other diorganotin oxides; dibutyltin borate, dioctyltin borate, dicyclohexyl Diorgano tin borate such as Suzuboreto; can be used in combination singly or two or more kinds.

The charge control agents described above are preferably used in the form of fine particles, and in this case, the number average particle diameter of these charge control agents is preferably 4 μm or less, more preferably 3 μm or less.

When these charge control agents are internally added to the developer, it is preferably used in an amount of 0.1 to 20 parts by mass, particularly 0.2 to 10 parts by mass, relative to 100 parts by mass of the binder resin.

As the coloring material which can be further added to the developer of the present invention, conventionally known carbon black, copper-phthalocyanine, etc. can be used.

The magnetic developer of the present invention has environmental stability,
In order to improve the charging stability, developability, fluidity and storage stability, the magnetic developer characterized by the present invention is obtained by stirring and mixing an inorganic fine powder which has been organically treated with magnetic toner particles with a mixer such as a Henschel mixer. Is obtained.

As the inorganic fine powder used in the present invention,
Inorganic fine powders such as silicic acid fine powder, titanium oxide, and aluminum oxide are preferable, and silicic acid fine powder is particularly preferable.
For example, as the silicic acid fine powder, both a so-called dry method produced by vapor phase oxidation of a silicon halide or a dry silica called fumed silica and a so-called wet silica produced from water glass or the like can be used. But
Dry silica having less silanol groups on the surface and inside the silica fine powder and less production residues such as Na ₂ O and SO ₃ ^2- is preferable.

Further, in the case of dry silica, a composite fine powder of silica and another metal oxide is obtained by using another metal halogen compound such as aluminum chloride or titanium chloride together with the silicon halogen compound in the manufacturing process. Things are possible and they are included.

The present invention is characterized by using organically treated inorganic fine powder. As such an organic treatment method, a method of treating with an organometallic compound such as a silane coupling agent or a titanium coupling agent which reacts or physically adsorbs with the inorganic fine powder, or after treatment with a silane coupling agent, or silane A method of treating with a coupling agent and at the same time treating with an organic silicon compound such as silicone oil can be mentioned.

Examples of the silane coupling agent used in the organic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane and allylphenyldisilane. Chlorsilane, benzyldimethylchlorosilane, brommethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxy Silane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1. 3-divinyltetramethyldisiloxane, 1.3-diphenyltetramethyldisiloxane and 2 to 12 siloxane units per molecule and each terminal unit contains a hydroxyl group bound to one silicon atom. Dimethyl polysiloxane and the like.

Also, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, mono having a nitrogen atom. Butylaminopropyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane,
A silane coupling agent such as dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine and trimethoxysilyl-γ-propylbenzylamine may be used alone or in combination. A preferred silane coupling agent is hexamethyldisilazane (H
MDS).

As the organic silicon compound, silicone oil can be used. As a preferred silicone oil, one having a viscosity of 50 to 100 centistokes at 25 ° C. is used, and for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil, etc. Is particularly preferable.

As a method for treating silicone oil, for example, silica fine powder treated with a silane coupling agent and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silica fine powder to be a base. A method of spraying silicone oil on the body may be used.
Alternatively, a method may be used in which silicone oil is dissolved or dispersed in a suitable solvent, and then silica fine powder is added and mixed to remove the solvent.

The organically treated inorganic fine powder used in the present invention has a specific surface area of 3 as measured by the BET method by nitrogen adsorption.
In the range of 0 m ² / g or more, especially 50 to 400 m ² / g give good results, also hydrophobized inorganic fine powder used in the present invention with respect to 100 parts by magnetic toner particles 0.01 -8 mass parts is preferably used, preferably 0.1-5 mass parts, particularly preferably 0.2-3 mass parts. If it is less than 0.01 parts by mass, the effect of improving the aggregation of the magnetic toner will be poor, and if it exceeds 8 parts by mass, problems such as toner scattering between fine lines, contamination inside the machine, and damage and abrasion of the photoconductor tend to occur. Is.

The magnetic developer of the present invention may further contain other additives within a range that does not have a substantial adverse effect, for example, Teflon powder, zinc stearate powder, lubricant powder such as polyvinylidene fluoride powder, or cerium oxide powder. , Silicon carbide powder, abrasives such as strontium titanate powder, or flowability-imparting agents such as titanium oxide powder and aluminum oxide powder, anti-caking agent, or conductive such as carbon black powder, zinc oxide powder, tin oxide powder, etc. It is also possible to use a small amount of a property imparting agent, organic fine particles of opposite polarity, and inorganic fine particles as a developing property improver.

The absolute value of the charge amount of the magnetic developer in the present invention is preferably in the range of 5-40 mC / kg. When the absolute value of the charge amount of the magnetic developer is less than 5 mC / kg, the developability is insufficient, and when the absolute value of the charge amount of the magnetic developer exceeds 40 mC / kg, the static particles of the developer are The electric cohesive force and the electrostatic adhesion force to the surface of the electrostatic latent image carrier were increased, and cleaning failure or developer fusion was likely to occur.

A method for measuring the charge amount of the magnetic developer having magnetic toner particles according to the present invention will be described below with reference to FIG.

Using EFV200 / 300 (manufactured by Powdertech Co., Ltd.) as a carrier in an environment of 23 ° C. and 60% relative humidity, a mixture of 9.5 g of the carrier and 0.5 g of the magnetic developing agent was made of polyethylene having a volume of 50 to 100 ml. Shake by hand 50 times. Then, 1.0 to 1.2 g of the mixture is put into a metal measuring container 2 having a 500 mesh screen 3 on the bottom, and a metal lid 4 is placed on the container. At this time, the total mass of the measurement container 2 is weighed and set to W1g. Next, in the suction device (at least the portion in contact with the measurement container 2 is an insulator), suction is performed from the suction port 7 and the air volume control valve 6 is adjusted to set the pressure of the vacuum gauge 5 to 2451 hPa (250 mmAq). In this state, suction is performed for 1 minute to remove the developer by suction. The potential of the electrometer 9 at this time is V (volt). Here, 8 is a capacitor, and the capacitance is C (μF).
Further, the mass of the entire measuring machine after suction is weighed and designated as W (g).
The triboelectric charge amount (mC / kg) of this developer is calculated by the following formula.

Triboelectric charge amount (mC / kg) = CV / W1-W2

To prepare the magnetic developer according to the present invention,
Known methods are used. For example, a binder resin, a wax, a metal salt or a metal complex, a pigment as a coloring agent, or a dye, a magnetic material, a charge control agent, and other additives as necessary are added to a Henschel mixer. , A ball mill, etc., and then thoroughly kneaded with a heat kneader such as a heating roll, kneader, or extruder to melt and knead the resins with each other. Metal compounds, pigments, dyes, magnetic materials The solid particles are dispersed or dissolved, cooled and solidified, and then pulverized and classified to obtain magnetic toner particles. Then, if necessary, additives such as organically treated inorganic fine powder are mixed and dispersed to obtain the magnetic property of the present invention. You can get the developer.

The weight average particle diameter (D4) of the magnetic developer having the magnetic toner particles in the present invention can be measured by various methods. In the present invention, Coulter Multisizer II type (manufactured by Coulter Co.) is used. It was performed using.

The electrolyte is 1% sodium chloride.
Adjust the aqueous NaCl solution. For example, ISOTON-II
(Manufactured by Coulter Scientific Japan) can be used. As the measuring method, the electrolytic aqueous solution 100 to 1 is used.
To 50 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of the developer are measured by using a 100 μm aperture as an aperture with the above-described measuring device to obtain a volume distribution and a number distribution. Was calculated. Then, the weight-based weight average particle diameter (D4:
(The median value of each channel is the representative value for each channel)
I asked.

In the present invention, the magnetic properties of the magnetic developer having magnetic toner particles are determined by using VSMP-1-10 (manufactured by Toei Industry Co., Ltd.) at room temperature in an external magnetic field of 79.58 kA /
It was determined from the result of measurement at m (1 kOe).

In the present invention, the specific surface area of the magnetic developer having the magnetic toner particles is determined according to the BET method by using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics Co., Ltd.) to adsorb nitrogen gas on the surface of the sample so that the BET is increased. The specific surface area was calculated using the point method.

In the present invention, the content of trivalent metal other than iron contained in the magnetic material is measured by the following method.

0.2 g of the magnetic substance was collected in a beaker, and 12
Add 15 ml of normal hydrochloric acid aqueous solution and continue the reaction with heating and stirring until everything is dissolved and transparent. Water is added to the obtained solution to make 100 ml, and the sample solution is used to measure the dissolved amount of a trivalent metal element other than iron by plasma emission spectroscopy (ICP). The abundance of the trivalent metal element other than iron with respect to the mass of the magnetic substance is calculated using a calibration curve obtained by similarly measuring a standard solution of the trivalent metal element other than iron.

Further, in order to determine the content of trivalent metal elements other than iron in the crystal lattice of the magnetic substance, the deposits and the like on the magnetic substance surface were washed with an aqueous sodium hydroxide solution having a pH of about 10.
After the removal, the content of the trivalent metal element other than iron may be measured by plasma emission spectroscopy as described above.

When the magnetic substance contained in the magnetic developer is analyzed, an organic solvent such as xylene that dissolves the resin component of the magnetic developer is mixed with the developer, and the resin component of the magnetic developer is mixed. The solution in which is dissolved is filtered through a membrane filter having a pore size of 0.1 μm to collect the magnetic substance remaining on the filter. The presence of trivalent metal elements other than iron was measured by treating the collected magnetic material in an atmosphere of 600 ° C to remove organic components, and then analyzing the obtained magnetic material by the method described above. To be done.

In the present invention, the blackness of the magnetic developer is measured by the following method.

An organic solvent such as xylene, which dissolves the resin component of the magnetic developer, is added to the magnetic developer to form an organic solvent 80
A solution in which the magnetic developer is dissolved is prepared so that the resin component of the magnetic developer is 20 parts by mass with respect to parts by mass. A solution in which the resin component of the magnetic developer is dissolved is quickly coated on the OHP made of PET with a bar coater so that the film thickness is about 10 μm, and this is used as a measurement sample piece. OH
A sufficient number of blank sheets are placed on the back side of the P sample piece, and the coating film on the sample piece is color-measured by using a high-speed color analyzer CA-35 (manufactured by Murakami Color Research Laboratory), and L ^* value, a ^* is measured by Lab space of Hunter ^. Value and b ^* value are measured respectively, and the International Commission on Illumination (Commission International
ale de l'Eclairage, CIE) 19
76 (L ^* , a ^* , b ^* ) is displayed according to the uniform perceptual color space.

The developer carrier carrying the magnetic developer of the present invention is preferably covered with a resin layer containing conductive fine particles.

The surface roughness of the developer carrier used in the present invention is from 0.2 to JIS center line average roughness (Ra).
It is preferably in the range of 3.5 μm.

If Ra is less than 0.2 μm, the amount of charge on the developer carrying member will be high and the developability will be insufficient. When Ra exceeds 3.5 μm, unevenness occurs in the developer coating layer on the developer carrying member, resulting in uneven density on the image.

As the conductive fine particles contained in the resin layer for coating the surface of the developer carrying member, carbon black, graphite, conductive metal oxides such as conductive zinc oxide and metal complex oxides, etc. may be used alone or in combination. One or more are preferably used. Further, as the resin in which the conductive fine particles are dispersed, a phenol resin, an epoxy resin, a polyamide resin, a polyester resin, a polycarbonate resin,
Known resins such as polyolefin resins, silicone resins, fluorine resins, styrene resins, and acrylic resins are used.

A thermosetting or photocurable resin is particularly preferable.

In the magnetic developer of the present invention, the member for regulating the magnetic developer on the developer carrier is regulated by the elastic member which is in contact with the developer carrier via the developer. It is particularly preferable from the viewpoint of uniformly charging the developer.

[0094]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples, but the present invention is not limited thereto. In the following formulation, all parts are parts by mass.

In FIG. 1, reference numeral 100 is a photosensitive drum around which a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, etc. are provided. And the photosensitive drum 100
Is charged to -700V by the primary charging roller 117. (Applied voltage is AC voltage −2.0 kVpp, DC voltage −700 Vdc) Then, laser light 123 is applied to the photosensitive drum 100 by the laser generator 121 to perform exposure. The electrostatic latent image on the photosensitive drum 100 is developed with a one-component magnetic developer by the developing device 140 and transferred onto a transfer material by the transfer roller 114. The transfer material bearing the developer image is conveyed to the fixing device 126 by the conveyor belt 125 or the like and fixed on the transfer material. Further, the developer partially left on the electrostatic latent image carrier is cleaning means 11
It is cleaned by 6. As shown in FIG. 2, the developing device 140 is provided with a cylindrical developer carrier 102 (hereinafter referred to as a developing sleeve) made of a non-magnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive drum 100. The gap between the drum 100 and the developing sleeve 102 is about 300 μm due to a sleeve / drum gap holding member (not shown).
Has been maintained. Further, a stirring member 141 is provided in the developing device, and the magnet roller 10 is provided in the developing sleeve.
4 is fixed and disposed concentrically with the developing sleeve 102. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the drawing, S1 is development, N1 is developer coat amount regulation, and S1 is S.
2 influences the developer intake / conveyance, and N 2 influences the developer blowout prevention. An elastic blade 103 is provided as a member for regulating the amount of the magnetic developer attached to the developing sleeve 102 and conveyed, and the amount of the developer conveyed to the developing area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. To be done. In the developing area, the photosensitive drum 100
A DC and AC developing bias is applied between the developing sleeve 102 and the developing sleeve 102, and the developer on the developing sleeve flies on the photosensitive drum 100 in accordance with the electrostatic latent image and becomes a visible image.

The content of the trivalent metal other than iron used in the present invention is 2 to 15% by weight and 79.58 kA / m (1 k
Saturation magnetization σs in the magnetic field of Oe) is 20 to 50 Am ²
An example of the production of the hydrophobized magnetic substance of 1 kg / kg (emu / g) is shown below.

[Magnetic Material Production Example 1] 0.35 mol / sodium hydroxide aqueous solution in a 4-liter three-necked flask.
1 liter of aluminum sulfate aqueous solution was mixed, and 1 mol of 0.8 mol / l ferrous sulfate aqueous solution was added thereto, and the mixture was oxidized at about 80 ° C. while blowing an oxygen-containing gas while keeping the pH at 10-12. Then, the pH of the reaction solution is adjusted to 6
After adjusting to ~ 8, the magnetic particles were filtered, washed with water, dried and crushed to obtain hydrophobized magnetic powder.

Then, 1 part of dimethyl silicone oil (1000 cSt) was added to Simpson Mix Mahler (MPVU-2 manufactured by Matsumoto Foundry Co., Ltd.) with respect to 100 parts by mass of the magnetic powder, and after operating at room temperature for 30 minutes, it was further hammered. A hydrophobized magnetic substance a was obtained by loosening with a mill. Table 1 shows the physical property values of the hydrophobized magnetic substance a thus obtained.

[Magnetic Material Production Examples 2 to 7] Magnetic Material Production Examples except that the concentrations of the aluminum sulfate and sodium hydroxide aqueous solutions were adjusted, and the hydrophobizing agent and amount were changed as shown in Table 1. In the same manner as in 1, the hydrophobized magnetic substance b to
g was obtained. Table 1 shows the physical property values of the obtained hydrophobized magnetic materials b to g.

[Magnetic Material Production Example 8] A solution of 1 part of isopropyltriisostearoyl titanate in 100 parts by mass of toluene was added to 100 parts by mass of the hydrophobized magnetic powder of Magnetic Material Preparation Example 1, and the mixture was stirred for 3 hours. The resultant was subjected to a hydrophobic treatment, filtered, and dried to obtain a magnetic substance h. Table 1 shows the physical properties of the obtained magnetic material h.

[Magnetic Material Production Examples 9 to 10] Magnetic Material Production Example 8
In the above, except that the hydrophobizing agent and the amount were changed as shown in Table 1, hydrophobizing magnetic materials i to j were obtained in the same manner as in Magnetic Material Production Example 8. Table 1 shows the physical property values of the obtained hydrophobized magnetic materials i to j.

[Magnetic Material Comparative Production Example 1] 0.8 mol of an aqueous sodium hydroxide solution was placed in a 4-liter three-necked flask.
/ L ferrous sulfate aqueous solution 1 liter mixed system (pH
8 to 10), it is oxidized at about 80 ° C. while blowing steam and oxygen. The obtained black magnetic powder was filtered, washed with water, dried, and crushed, and then hydrophobized in the same manner as in Magnetic Material Production Example 1 to obtain a magnetic material k. Table 1 shows the physical property values of the obtained magnetic material k.

[Magnetic Material Comparative Production Example 2] 0.8 mol was added to an aqueous solution of sodium hydroxide in a 4-liter three-necked flask.
/ L ferrous sulfate aqueous solution 1 liter mixed system (pH
9 to 11) is oxidized by blowing steam and oxygen at about 80 ° C. 0.04 mol / l at the end of oxidation
1 liter of aluminum sulfate aqueous solution of
Is adjusted to 6 to 8 and then further reacted. The obtained black powder was filtered, washed with water, dried, and crushed, and then hydrophobized in the same manner as in Magnetic Material Production Example 1 to obtain a magnetic material 1. Table 1 shows the physical property values of the magnetic material 1 thus obtained.

[Magnetic Material Comparative Production Example 3] 0.2 mol of an aqueous sodium hydroxide solution was placed in a 4-liter three-necked flask.
1 liter of an aqueous solution of zinc sulphate of 0.1 liter / liter was added to this,
1 liter of an 8 mol / l ferrous sulfate aqueous solution is added, and the pH of the reaction solution is maintained at 6 to 8 while the oxygen-containing gas is being blown thereinto to oxidize at about 80 ° C. The obtained black powder was filtered, washed with water, dried, and crushed, and then hydrophobized in the same manner as in Magnetic Material Production Example 1 to obtain a magnetic material m containing about 10% by mass of elemental zinc. Table 1 shows the physical property values of the magnetic material m thus obtained.

[Magnetic Material Comparative Production Example 4] Magnetic Material Production Example 1 except that the hydrophobizing treatment is not performed in Magnetic Material Production Example 1.
A magnetic substance n was obtained in the same manner as in. Table 1 shows the physical property values of the obtained magnetic material n.

[Magnetic Material Comparative Production Example 5] An untreated magnetic material o was obtained in the same manner as in Magnetic Material Comparative Production Example 1 except that the hydrophobizing treatment was not performed. . Table 1 shows the physical property values of the obtained untreated magnetic material o.

[Magnetic Material Comparative Production Example 6] An untreated magnetic material p was obtained in the same manner as in the magnetic material comparative production example 2 except that the hydrophobic treatment was not performed. . Table 1 shows the physical properties of the obtained untreated magnetic material p.

[0108]

[Table 1]

(Developer Production Example 1) 100 parts of magnetic substance a 100 parts of styrene-n-butyl acrylate copolymer (copolymerization ratio 8: 2 Mw = 260,000) Iron complex of monoazo dye (negative charging property) Control agent) 2 parts ・ Low molecular weight polyolefin (release agent) 2 parts

The above materials were mixed in a blender to obtain 140
Melted and kneaded with a twin-screw extruder heated to ℃, the cooled kneaded material is roughly crushed with a hammer mill, the coarsely crushed material is finely crushed with a jet mill, and the obtained finely pulverized material is classified with an air classifier. A black fine powder was obtained. 1.2% by weight of hydrophobic silica fine powder (hexamethyldisilazane-treated BET specific surface area 200 m ² / g) was added to the obtained black fine powder,
After stirring and mixing with a Henschel mixer, the coarse particles were removed with a 150-mesh sieve to obtain a magnetic developer A. The weight average particle diameter of the obtained magnetic developer A was 6.7 μm.

When the blackness of this magnetic developer was measured, L ^* = 20.68, a ^* = 0.02, b ^* =-
The value was 2.11, showing good blackness.

Table 2 shows the physical properties of the above magnetic developer A.

(Developer Manufacturing Example 2) 150 parts of magnetic material b of Magnetic Material Manufacturing Example 1 100 parts of styrene-2 ethylhexyl acrylate-n-butyl maleic acid half ester copolymer (copolymerization ratio 7: 2: 1, Mw = 220,000) -Negative charge control agent (monoazo dye-based chromium complex) 0.8 part-Ethylene-propylene copolymer (Mw = 6000) 4 parts

A black fine powder was obtained in the same manner as in Production Example 1 using the above components. 2.0 mass% of hydrophobic silica fine powder (the same as in Production Example 1) was added to 100 parts by weight of this black fine powder, and Magnetic Developer B was obtained in the same manner as in Production Example 1. The weight average particle diameter of this developer was 5.2 μm.
Also, when the blackness of this magnetic developer B was measured,
^* = 20.04, a ^* = 0.13, b ^* =-0.58, indicating good blackness.

Table 2 shows the physical properties of the above magnetic developer B.

(Developer Manufacturing Example 3) A developer was manufactured except that the magnetic material c obtained in Magnetic Material Manufacturing Example 3 was used as a magnetic material in an amount of 60 parts by weight and the amount of hydrophobic silica added was 0.6% by mass. In the same manner as in Example 1, a magnetic developer C having a weight average particle size of 9.9 μm was obtained. Table 2 shows the physical properties of Developer C thus obtained.

(Developer Production Example 4) -Magnetic substance d 120 parts-Polyester resin 100 parts-Monoazo dye iron complex (negative charge control agent) 2 parts-Low molecular weight polyolefin (release agent) 2 parts

In the developer manufacturing example 1, 1.2% by weight of hydrophobic silica was used as 0.9% by weight of hydrophobic titanium oxide fine powder (isobutylsilane-treated BET specific surface area 50 m ² / g), and the above materials were used. A magnetic developer D having a weight average particle diameter of 6.0 μm was obtained in the same manner as in Developer Production Example 1 except for the above. Table 2 shows the physical properties of the obtained magnetic developer D.

(Developer Production Example 5) As a magnetic material, 140 parts by mass of the magnetic material e obtained in Magnetic Material Production Example 5 was used, and hydrophobic silica fine powder (hexamethyldisilazane treated BET specific surface area 380 m ² / g) was used. Was obtained in the same manner as in Developer Production Example 1 to obtain a magnetic developer E having a weight average particle size of 8.6 μm. Table 2 shows the physical properties of the obtained magnetic developer E.

(Developer Production Example 6) A developer was produced except that the magnetic material f obtained in Magnetic Material Production Example 6 was used as a magnetic material in an amount of 120 parts by mass and the amount of hydrophobic silica added was 1.8% by mass. A magnetic developer F having a weight average particle diameter of 4.8 μm was obtained in the same manner as in Example 1. Table 2 shows the physical properties of the obtained magnetic developer F.

(Developer Production Example 7) Developer production except that the magnetic substance g obtained in Magnetic Substance Production Example 7 was 100 parts by mass as the magnetic substance, and the amount of hydrophobic silica added was 1.4% by mass. A magnetic developer G having a weight average particle size of 6.5 μm was obtained in the same manner as in Example 1. Table 2 shows the physical properties of the obtained magnetic developer G.

(Developer Production Examples 8 to 10) As magnetic materials, 100 parts by mass of the magnetic materials h to j obtained in Magnetic Material Production Examples 8 to 10 were used, and the amount of hydrophobic silica added was 1.4% by mass. Except for the above, the weight average particle size is 6.
5 μm of magnetic developers H to J were obtained. Table 2 shows the physical properties of the obtained magnetic developers H to J.

(Developer Comparative Production Example 1) A mass average particle diameter of 6. was obtained in the same manner as in Developer Production Example 1 except that 100 parts by mass of the magnetic material k obtained in Magnetic Material Comparative Production Example 1 was used as the magnetic material. 7 μm of magnetic developer K was obtained. Table 2 shows the physical properties of the obtained magnetic developer K.

(Developer Comparative Production Example 2) A weight average particle diameter of 6. was obtained in the same manner as in Developer Production Example 1 except that 100 parts by mass of the magnetic material 1 obtained in Magnetic Material Comparative Production Example 2 was used as the magnetic material. A magnetic developer L of 7 μm was obtained. Table 2 shows the physical properties of the obtained magnetic developer L.

(Developer Comparative Production Example 3) A weight average particle diameter of 6. was obtained in the same manner as in Developer Production Example 1 except that 100 parts by mass of the magnetic material m obtained in Magnetic Material Comparative Production Example 3 was used as the magnetic material. A magnetic developer M of 7 μm was obtained. Further, when the blackness of this magnetic developer M was measured, L ^* = 20.96, a ^*
= 0.87, b ^* = -0.48, and a reddish black color was exhibited. Table 2 shows the physical properties of the obtained magnetic developer M.

(Developer Comparative Production Examples 4 to 6) As magnetic substances, the magnetic substances n to p obtained in Magnetic Substance Comparative Production Examples 4 to 6 were used.
Magnetic Developers N to P having a weight average particle size of 6.7 μm were obtained in the same manner as in Developer Production Example 1 except that 0 part by mass was used. Table 2 shows the physical properties of the obtained magnetic developers N to P.

[0127]

[Table 2]

Example 1 A rubber roller (diameter 12 mm, contact pressure 50 g / cm) in which conductive carbon coated with nylon resin is dispersed is used as a primary charging roller, and a diameter is used as an electrostatic latent image carrier. Dark part potential VD = -700V by laser exposure using a 30 mm OPC drum,
The light portion potential VL was set to -150V. As a developer carrying member, the layer thickness of the following constitution is about 7 μm, and the JIS center line average roughness (R
a) A resin layer of 2.0 μm with a diameter of 16
A developing sleeve formed on a φ stainless cylinder was created.・ Phenolic resin 100 parts by mass ・ Graphite (particle size: about 7 μm) 90 parts by mass ・ Carbon black 10 parts by mass

Then, the gap between the photosensitive drum and the developing sleeve was set to 300 μm, a developing magnetic pole of 850 gauss, a urethane regulating blade having a thickness of 1.0 mm and a free length of 10 mm as a developer regulating member were brought into contact with each other at a linear pressure of 15 g / cm. It was DC bias component Vdc = -450 as developing bias
V, superposed AC bias component Vp-p = 1400V,
f = 2000 Hz was used.

A urethane rubber blade having a thickness of 2.0 mm and a free length of 8 mm was brought into contact with the photosensitive member cleaning blade at a linear pressure of 25 g / cm.

The magnetic developer A of Developer Production Example 1 was used as a developer, and after standing for 24 hours and 10 days in an environment of 30 ° C. and 85% RH, image formation was performed. As a result, as shown in Table 3, good images with sufficient image density and high resolution were obtained. Also, the resolution of a 1-dot latent image of 80 μm was at a sufficiently good level.

Further, when the continuous 500 sheets (A4 size) were printed at a printing ratio of 4% in an environment of 23 ° C. and a relative humidity of 60%, the developer consumption was calculated to be 0.042 g.
It was / sheet.

(Examples 2 to 10) Images were produced in the same manner as in Example 1 except that the developers B to J of Developer Production Examples 2 to 10 were used as the developers. I went to work.
As a result, good results as shown in Table 3 were obtained.

Example 11 The same procedure as in Example 1 was carried out except that the developing sleeve had a JIS center line average roughness (Ra) of 0.8 μm. Good results have been obtained as shown.

(Comparative Examples 1 and 2) Developers K and L of Comparative Developer Examples 1 and 2 were used as developers, and image formation was performed under the same apparatus and conditions as in Example 1. As a result, as shown in Table 3, for both magnetic developers K and L, the trailing was slightly noticeable on the image. Also, the resolution of a 1-dot latent image of 80 μm was slightly inferior.

(Comparative Example 3) Developer As a developer, the developer M of Comparative Production Example 4 was used, and image formation was performed under the same apparatus and conditions as in Example 1. As a result, the image was a reddish conspicuous image and lacked in sharpness.

(Comparative Example 4) Developer As the developer, the developer N of Comparative Production Example 4 was used, and image formation was performed under the same apparatus and conditions as in Example 1. As a result, as shown in Table 3, a good image was obtained after standing for 24 hours, but after 10 days, the image density was lowered and the image was unclear.

(Comparative Example 5) Developer O was used as the developer and the developer O of Comparative Production Example 5 was used, and image formation was performed using the same apparatus and conditions as in Example 1. As a result, as shown in Table 3, a good image density was obtained after standing for 24 hours, but after standing for 10 days, the image density decreased and the image was unclear.

(Comparative Example 6) Developer As a developer, the developer P of Comparative Production Example 6 was used, and image formation was performed using the same apparatus and conditions as in Example 1. As a result, as shown in Table 3, a good image was obtained after standing for 24 hours, but after 10 days, the image density was lowered and the image was unclear.

[0140]

[Table 3]

[0141]

INDUSTRIAL APPLICABILITY The magnetic developer of the present invention and the image forming method using the magnetic developer include a magnetic developer having magnetic toner particles containing at least a binder resin and a magnetic material.
The magnetic substance contains 2 wt% to 20 wt% of a trivalent metal other than iron, and has a saturation magnetization σs of 20 to 50 Am ² / kg (em) in a magnetic field of 79.58 kA / m (1 kOe).
u / g), and since the magnetic material is subjected to a hydrophobic treatment with an organic compound having a hydrophobic group, the developer consumption is improved, and the good storability is maintained even in a hot and humid environment. It is possible to obtain a high-resolution, high-definition reproducibility image that has a high image density, maintains a sufficient image density, is free from fogging and tailing, and has a good blackness.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of an image forming apparatus used in the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an explanatory diagram of a triboelectric charge amount measuring method of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 15/09 101

Claims (15)

[Claims] 1. A magnetic developer having magnetic toner particles containing at least a binder resin and a magnetic substance, wherein the magnetic substance contains 2% by mass to 20% by mass of a trivalent metal other than iron, and 79 Saturation magnetization σs in a magnetic field of 0.58 kA / m (1 kOe) is 20 to 50 Am ² / kg.
(Emu / g), and the magnetic material is subjected to a hydrophobizing treatment with an organic compound having a hydrophobic group. 2. The magnetic developer according to claim 1, wherein the magnetic developer includes the magnetic toner particles and an organically treated inorganic fine powder. 3. The magnetic developer according to claim 1, wherein the magnetic material has a FeO content of 18% by mass or more based on the mass of the magnetic material. 4. The chromaticity of the magnetic developer satisfies the following formula conditions: −1.0 ≦ a ^* ≦ 0.8, −3.0 ≦ b ^* ≦ 0 (where a ^* is (L ^* a ^* b 4. The magnetic developer according to claim 1, wherein ^* ) represents chromaticity in the red-green direction in the uniform perceptual color space, and b ^* represents chromaticity in the yellow-blue direction. 5. The magnetic developer according to claim 1, wherein the trivalent metal contained in the magnetic material is aluminum. 6. The hydrophobic treatment of the magnetic substance is characterized in that a hydrophobic liquid is carried on the magnetic substance by stirring action, compression action, shearing action or spatula action. Item 5. The magnetic developer according to items 1 to 5. 7. The viscosity of the hydrophobic liquid at 25 ° C. is 1.
The magnetic developer according to claim 1, wherein the magnetic developer has a density of 0 to 200,000 cSt. 8. An electrostatic latent image carrier and a developer carrier are arranged in a developing section with a certain gap, and a magnetic developer is further removed from the gap on the developer carrier. An image forming method in which the latent image on the electrostatic latent image carrier is developed by controlling the thickness of the toner to be conveyed to the developing unit and applying an alternating electric field in the developing unit. A magnetic developer having magnetic toner particles containing a resin and a magnetic substance, wherein the magnetic substance contains 2% by mass to 20% by mass of a trivalent metal other than iron.
And the saturation magnetization σs in the magnetic field of 79.58 kA / m (1 kOe) is 20 to 50 Am ² / kg (em
u / g) and the magnetic material is subjected to a hydrophobic treatment. 9. The image forming method according to claim 8, wherein the magnetic developer contains the magnetic toner particles and an organically treated inorganic fine powder. 10. The image forming method according to claim 8, wherein the magnetic substance has a FeO content of 18% by mass or more based on the mass of the magnetic substance. 11. The chromaticity of the magnetic developer satisfies the following formula conditions: −1.0 ≦ a ^* ≦ 0.8, −3.0 ≦ b ^* ≦ 0 (where a ^* is (L ^* a ^* b The image forming method according to claim 8, wherein ^* ) represents a chromaticity in the red-green direction in the uniform perceptual color space, and b ^* represents a chromaticity in the yellow-blue direction. 12. The image forming method according to claim 8, wherein the trivalent metal contained in the magnetic material is aluminum. 13. The hydrophobic treatment of the magnetic substance is characterized in that a hydrophobic liquid is carried on the magnetic substance by stirring action, compression action, shearing action or spatula action. 13. The image forming method according to items 8 to 12. 14. The image forming method according to claim 8, wherein the hydrophobic liquid has a viscosity at 25 ° C. of 10 to 200,000 cSt. 15. The developer carrier is coated with a resin layer containing conductive fine particles.
15. The image forming method according to any one of 14 to 14.