JP3256821B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a magnetic developer used in electrophotography, electrostatic recording, magnetic recording and the like.

[0002]

2. Description of the Related Art Conventionally, many methods are known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The latent image is developed with a developer to form 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, pressure, etc. and copied. Get things.

In recent years, devices using electrophotography have been increasing in number, such as printers and facsimile machines, in addition to conventional copying machines. Particularly, in a printer or a facsimile, a developing device using a one-component developer is often used because it is necessary to reduce the size of a copying device.

A conventional image forming apparatus using a one-component developer has, for example, a configuration as shown in FIG. In FIG.
100 is a photosensitive drum (hereinafter, referred to as an electrostatic latent image carrier)
The primary charging roller 117 and the developing device 14
0, a transfer charger 114, a cleaner 116, a register roller 124, and the like. Then, the electrostatic latent image carrier 100 is charged by the primary charging roller 117.

The electrostatic latent image carrier 100 is exposed by irradiating the electrostatic latent image carrier 100 with a laser beam 123 by a laser generator 121. The electrostatic latent image on the electrostatic latent image carrier 100 is developed with a one-component magnetic developer by a developing device 140, and is transferred onto a transfer material by a transfer charger 114. The transfer material having the developer image thereon is conveyed to a fixing device 126 by a conveyor belt 125 or the like and is fixed on the transfer material.

As shown in FIG. 2, a developing device 140 is a cylindrical developing sleeve (hereinafter referred to as a developer carrying member) made of a non-magnetic metal such as aluminum or stainless steel in the vicinity of the electrostatic latent image carrier 100. 102, the electrostatic latent image carrier 1
The distance between the photoconductor 00 and the developer carrier 102 is set to about 30 by a developer carrier / electrostatic latent image carrier spacing member (not shown).
It is maintained at 0 μm. A magnet roller 104 is fixed and disposed concentrically with the developer carrier 102 in the developer carrier. However, the developer carrier 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure, S1 affects development, N1 regulates the amount of developer, S2 influences taking-in / conveyance of the developer, and N2 influences prevention of the blowing of the developer. An elastic blade 103 is provided as a member for regulating the amount of the magnetic developer adhered to and conveyed to the developer carrier 102.
The amount of the developer conveyed to the development area is controlled by the contact pressure of the third developer carrier 102. In the developing area, between the electrostatic latent image carrier 100 and the developer carrier 102, FIG.
Is applied, and the developer on the developer carrier flies onto the electrostatic latent image carrier 100 in accordance with the electrostatic latent image to become a visible image.

The one-component developing system does not require carrier particles such as glass beads and iron powder as in the two-component developing system, so that the developing device itself can be reduced in size and weight. Further, in the two-component developing method, since it is necessary to keep the toner concentration in the carrier constant, a device for detecting the toner concentration and supplying a necessary amount of toner is required. Therefore, the developing device also becomes large and heavy here. In the one-component developing system, such an apparatus is not required, so that the apparatus can be made small and light, which is preferable.

[0008] In recent years, LED and LBP printers have become the mainstream of printer devices in the market, and the direction of technology has been increased to higher resolution, ie, 240, 300 dpi has been changed to 400, 600, 800 dpi. I have. Accordingly, the development method is also required to have higher definition. Also, the functions of the copier have been advanced, and the digitalization has been proceeding. In this direction, the method of forming an electrostatic charge image with a laser is the main method, so it is also proceeding in the direction of high resolution, and here, as in the case of printers, high resolution and high definition development methods are required. JP-A-1-112253 and JP-A-2-284158 propose a developer having a small particle size.

By the way, in the one-component magnetic developing system, the developer is developed in a chain form (generally called "spikes") at the time of development, so that the resolution in the horizontal direction of the image is smaller than that in the vertical direction. Easy to get worse. For example, a trailing phenomenon due to the protrusion of ears tends to occur in a non-image portion in the latter half of the developed image, and a rough image tends to occur more easily than in the two-component developing system. Therefore, as a method of further improving image reproducibility, it is conceivable to make the developer ears shorter and denser, and as a means of reducing the amount of the magnetic substance in the developer, or using a developer layer thickness regulating member as a developer, Means such as strong contact with the carrier have been considered.

However, for example, when the amount of the magnetic substance is reduced, the charge amount of the developer generally becomes excessive and a so-called charge-up phenomenon occurs, resulting in a decrease in image quality such as a decrease in image density and an increase in fog. The relationship between the magnetization intensity of the magnetic developer and the shape of the ears is 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 large, the ears formed by the magnetic developer are long, the density of the ears on the developer carrier is coarse, and the individual ears are thin. Conversely, if the magnetization strength of the magnetic developer is small,
This time, the ears are short, and the density of the ears on the developer carrier becomes dense, but since the bonds between the magnetic developer particles are not released, the individual ears are thick and short, and are in an aggregated state. In this case, the magnetic developer particles existing inside the ears have less chance of contact with the surface of the developer carrier, resulting in poor charging. Such poorly charged developer particles become fogged on the image and deteriorate the image quality. Further, when the developer becomes fine particles (generally 9 μm or less), the charge-up phenomenon of the developer due to the reduction in the amount of the magnetic material is likely to occur, and the charged developer or fine powder is deposited on the developer carrier by a force such as a mirror force. , And causes a decrease in image density. Further, when the developer layer thickness regulating member is brought into strong contact with the developer carrying member, there are problems such as abrasion of the developer layer thickness regulating member and an increase in driving load, which is not preferable.

Further, as a means for making the magnetic developer shorter and denser, a method of reducing the saturation magnetization s of the developer can be considered. As a method for lowering the saturation magnetization s of the developer, Japanese Patent Application Laid-Open Nos.
No. 354, Japanese Unexamined Patent Publication No. Hei 4-223487, and the like, a method in which divalent iron of magnetite is replaced with a divalent metal such as zinc or copper to contain a ferrite-formed magnetic material or a needle-like magnetic material. A method has been proposed. However, the ferrite conversion method has a disadvantage that the magnetic material becomes reddish and blackness decreases as the saturation magnetization is reduced in order to reduce ferrous iron of magnetite. Further, in the method using a needle-shaped magnetic material, it is difficult to obtain a sufficient image density because the chargeability of the developer is inhibited and the holding power is too high.

Further, when the conventional developing method is applied to such a low magnetic force developer, the so-called fogging phenomenon is liable to occur, particularly because the balance between the developing bias and the magnetic binding force is lost.

These problems must be improved in order to obtain a high-resolution and high-definition image having a good blackness as described above.

[0014]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a method which is faithful to a document and faithful to a signal, that is, substantially fog-free and tailless to a latent image. Another object of the present invention is to provide an image forming method capable of obtaining an image having high resolution and high definition reproducibility.

It is a further object of the present invention to provide an image forming method capable of obtaining a high-quality image having a high image density and good blackness.

[0016]

More specifically, the present invention relates to a method for forming an electrostatic latent image carrier on an electrostatic latent image carrier by opposing a developer carrier carrying a developer layer. In an image forming method in which the developed electrostatic latent image is developed by reversal development.
The agent carrier has a surface roughness of JIS center line average roughness (Ra)
Is a first peak voltage for urging the developer from the developer carrier toward the visible portion of the electrostatic latent image, and the voltage level is the first peak voltage. And a second peak that urges the developer in a direction from the visible portion of the electrostatic latent image toward the developer carrier. And a second peak voltage having a voltage level opposite to the voltage level of the first peak voltage with respect to the potential of the visible portion of the electrostatic latent image. Applied to the body, as a developer, a black magnetic developer containing at least a binder resin and a magnetic powder, the black magnetic developer,
The magnetic material has a weight average particle size of 4 to 10 μm, the magnetic material contains 2 to 20% by weight of a trivalent metal other than iron, and a saturation magnetization σs in a magnetic field of 1 kOe is 20 to 50 emu /
g and the chromaticity of the magnetic developer is represented by the following formula: −1.0 ≦ a ^* ≦ 0.8, −3.0 ≦ b ^* ≦ 0 , 13 ≦ L ^* ≦ 23 (where a ^* is Development that satisfies (L ^* , a ^* , b ^* ) chromaticity in the red-green direction in the uniform perceived color space, b ^* indicates chromaticity in the yellow-blue direction, and L ^* indicates lightness. The present invention relates to an image forming method characterized by using an agent.

According to the present invention, the relationship between the developing bias applied to the developing sleeve and the potential on the electrostatic latent image carrier is determined in such a manner that only the image portion on the electrostatic latent image carrier is developed in the development acceleration cycle of the developing bias. Further, in the development pull-back cycle of the developing bias, a developing bias is applied so as to pull back the developer in the image portion on the electrostatic latent image carrier and the non-image portion, and the developer is applied to the image portion on the electrostatic latent image carrier. A magnetic developer containing at least a binder resin and a magnetic powder, wherein the magnetic material contains a trivalent metal other than iron in an amount of 2% by weight to 20%. containing by weight%, 1 saturation magnetization σs at a magnetic field of kilo oersted is 20~50emu / g, and chromaticity is represented by the following formula -1.0 ≦ a ^* ≦ 0.8 of the magnetic developer, -3.0 to satisfy a ≦ b ^* ≦ 0, by, the current With the proper electrostatic cohesion of the developer particles on the developer carrier and the appropriate magnetic binding force on the developer carrier, the developer particles are separated from the ears into individual developer particles in the development area space. It has a similar form, and achieves true flight of the developer particles to the electrostatic latent image, substantially preventing background fog and reversal fog when using a fine particle size developer, which is a conventional problem, and suppressing tailing. It is intended to provide a high-resolution, high-definition image with excellent blackness.

The chromaticity of the magnetic developer of the present invention preferably satisfies the following conditions: −1.0 ≦ a ^* ≦ 0.8, −3.0 ≦ b ^* ≦ 0, and more preferably the following conditions: ≦ L ^* ≦ 23, −0.8 ≦ a ^* ≦ 0.6, −3.0 ≦ b ^* ≦ 0.

When a ^* or b ^* is not in the above range,
The color becomes reddish or bluish, which is not preferable as a black developer. When L ^* is larger than 23, the coloring power of the developer becomes insufficient, and a sufficient image density cannot be obtained particularly in a solid portion. Alternatively, more developer is required to obtain a sufficient image density. Conversely, L ^* is 13
If it is smaller than this, the coloring power of the developer is excessive and fog becomes conspicuous.

Conventionally, as a means for reducing σs 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 ferrite magnetite, inevitably reduces the amount of ferrous iron in the magnetite, the particles become reddish black, and the blackness of the image is not sufficient. .

The magnetic material used in the magnetic developer of the present invention is obtained by adding a part or all of trivalent iron in magnetite to the magnetic material.
Since it is substituted with a different-valent metal and does not reduce FeO, an image with high blackness can be obtained without impairing blackness.

As examples using a magnetic material containing a trivalent metal other than iron, JP-A-58-91463 and JP-A-4-190242 disclose magnetic materials containing aluminum. However, in these, aluminum is present at or near the surface of the magnetic material, and the saturation magnetization amount s of the magnetic material is 60 to 65 emu / g at a magnetic field of 1 kOe, similarly to the conventionally used magnetic material. No effect of improving tailing can be obtained.

The saturation magnetization σs of the magnetic material contained in the magnetic developer of the present invention at a magnetic field of 1 kOe is
It is preferably 20 to 50 emu / g, more preferably 25 to 45 emu / g, and the FeO content is 1
It is preferably at least 8% by weight, more preferably at least 19% by weight.

When the σs of the magnetic material is less than 20 emu / g, defects such as image omission due to insufficient supply of the developer are likely to occur due to insufficient magnetic transport of the developer. The structure of the developing unit is required to be complicated, and the cost is increased. Further, if the magnetic transportability is to be supplemented by increasing the amount of the magnetic substance with respect to the binder resin, the fixability of the developer is deteriorated. On the other hand, if it exceeds 50 emu / g, the spike length of the magnetic developer on the developer carrier becomes longer, and the developer spike comes into contact with the surface of the electrostatic latent image carrier, resulting in an image with much fog. When the amount of the magnetic substance is reduced with respect to the binder resin to prevent this, the charge amount of the developer becomes too high, and the image density tends to decrease.

Further, the low-σs magnetic material having an FeO content of less than 18% does not have sufficient blackness.

Further, the ferrous element (F) contained in the magnetic material
e ²⁺ ) is preferably from 12% by weight to 23% by weight, and the ratio (F
e ²⁺ / Fe ³⁺ ) is preferably from 0.256 to 0.543.

Further, the amount of the foreign metal, which is a trivalent metal other than iron, contained in the magnetic material is 2% by weight to 20% by weight;
Preferably, the content is 3 to 15% by weight. The foreign metal (trivalent) contained in the magnetic material may exist in the form of a hydroxide or a hydrated oxide on the surface of the magnetic material or in the vicinity thereof, but 2% by weight is contained in the crystal lattice of the magnetic material. It is preferable that a foreign metal (trivalent) is contained by 10 to 10% by weight,
More preferably, it is 3% by weight to 6% by weight.

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

The magnetic material contained in the developer according to the present invention is a low magnetic material having a high blackness, which has not been obtained conventionally, in which a part or all of trivalent iron of magnetite is replaced by a trivalent foreign metal. It is a magnetic material of σs, and various metals can be used as the trivalent metal, and among them, aluminum is particularly preferable. In addition, as long as the blackness is not reduced, 2
Replacing valent iron with a divalent metal such as manganese, zinc, cobalt, or copper is also a preferred embodiment for controlling magnetic properties. Further, other metal elements may be contained within a range that does not affect the above.

As the shape of the magnetic material, octahedron, hexahedron,
There are spherical, irregular, needle-like, plate-like, scaly, etc., but those with little anisotropy such as octahedron, hexahedron, and sphere are preferable. The average particle size of the magnetic material is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.6 μm, and further preferably 0.1 to 0.4 μm. The magnetic material is preferably a magnetic powder having a Mohs hardness of 5 to 7.

The amount of the magnetic material is based on 100 parts by weight of the binder resin.
The amount is preferably 50 to 200 parts by weight, particularly preferably 60 to 150 parts by weight. If the amount is less than 50 parts by weight, the toner layer on the developer carrier tends to be uneven due to insufficient transportability, resulting in image unevenness, and further, the image density is reduced due to an excessive increase in the developer charge amount. It tended to be easy. On the other hand, if it exceeds 200 parts by weight, there is a tendency that a problem occurs in the fixing property.

The electric field between the developer carrying member and the image portion of the electrostatic latent image carrying member is 2.0
V / μm or more is preferable. If it is less than 2.0 V / μm, the force for flying the toner becomes weak, and a sufficient image density cannot be obtained. In addition, the above-mentioned effect of the present invention has a curvature radius of 50 mm.
This is particularly good when the following electrostatic latent image carrier is used in combination with a developer carrier having a radius of curvature of 20 mm or less. This is considered to be due to the fact that the development area and the surface area of the effective electrostatic latent image carrier become narrower, and the influence of the physical properties of the developer on the development becomes larger.

The weight average particle diameter of the developer of the present invention is as follows:
The thickness 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 aggregation of the developer becomes remarkable, and problems are likely to occur in the productivity (for example, the filling step) and the handling of the developer. On the other hand, if it exceeds 10 μm, the reproduction of a dot latent image or a fine line of 100 μm or less is not sufficient.

The kind of the binder resin used in the present invention includes, for example, polystyrene, poly-p-chlorostyrene, homopolymer of styrene such as polyvinyltoluene and a substituted product thereof; styrene-p-chlorostyrene copolymer. Copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene- Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrene copolymers such as indene copolymers Coalescence; polyvinyl chloride, phenolic resin, natural modified phenolic 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, cumarone indene resin, petroleum resin and the like can be used. Further, a crosslinked styrene resin is also a preferable binder resin.

Examples of comonomers for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and the like.
Such as dodecyl 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 vinyl chloride;
Vinyl esters such as vinyl acetate, vinyl benzoate and the like, for example, ethylene olefins such as ethylene, propylene, butylene and the like; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone;
For example, vinyl monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; and the like, or a vinyl monomer such as vinyl monomers, may be used alone or in combination. Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene or the like; for example, ethylene glycol diacrylate, ethylene glycol Dimethacrylate,
Carboxylic esters having two double bonds such as 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinylether, divinylsulfide, divinylsulfone; and compounds having three or more vinyl groups; Can be used alone or as a mixture.

The binder resin for the developer used for pressure fixing includes low-molecular-weight polyethylene, low-molecular-weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, higher fatty acid, and the like. Polyamide resin and polyester resin are mentioned. These are preferably used alone or as a mixture.

It is also preferable to include the following waxes in the developer from the viewpoint of improving the releasability from the fixing member at the time of fixing and improving the fixing property. 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., with derivatives including oxides and block copolymers with vinyl monomers , Graft-modified products.

In addition, alcohols, fatty acids, acid amides,
Esters, ketones, hydrogenated castor oil and derivatives thereof, vegetable 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 toner particles (internal addition) or mixed with developer particles (external addition).
It is preferable to use them. The charge control agent makes it possible to control the amount of charge optimally according to the development system. In particular, in the present invention, the balance between the particle size distribution and the amount of charge can be further stabilized. The following substances control the developer to be negatively charged.

For example, organic metal complexes and chelate compounds are effective, and examples thereof include monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid-based 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.

The following substances are controlled to be positively charged.

Modified products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and phosphonium salts which are analogs thereof Onium salts such as, for example, these lake pigments, triphenylmethane dyes and these lake pigments (as the lacking agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanic acid) , Ferrocyanide, etc.), metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; 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. In this case, the number average particle size of these charge control agents is particularly preferably 4 μm or less, more preferably 3 μm or less. When these charge control agents are internally added to the toner, it is preferable to use 0.1 to 20 parts by weight, particularly 0.2 to 10 parts by weight, based on 100 parts by weight of the binder resin.

As a coloring agent which can be further added to the magnetic developer of the present invention, conventionally known carbon black, copper-phthalocyanine and the like can be used.

The magnetic developer of the present invention contains fine silica powder to improve charging stability, developability, fluidity and storage stability.
It is preferable to add an inorganic fine powder such as titanium oxide or aluminum oxide. For example, as the fine silica 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. However, there are few silanol groups on the surface and inside the silica fine powder, and Na ₂ O,
Towards less dry silica of manufacture residues of SO ₃ ^2-like. In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride and titanium chloride together with a silicon halide in the manufacturing process. Is also included.

The silica fine powder used in the present invention is BET
Good results are obtained when the specific surface area measured by nitrogen adsorption is at least 30 m ² / g, especially 50 to 400 m ² / g, and 0.01 to ⁸ parts by weight of silica fine powder with respect to 100 parts by weight of the developer. It is preferable to use parts by weight, preferably 0.1 to 5 parts by weight. The silica fine powder used in the present invention may contain a silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, a silane coupling agent, a functional group for the purpose of hydrophobization, charge control, etc., if necessary. It is possible and preferable to use a silane coupling agent or other treating agent such as an organosilicon compound or a combination of various treating agents.

In the magnetic developer of the present invention, other additives such as lubricant powders such as Teflon powder, zinc stearate powder, and polyvinylidene fluoride powder; Abrasives such as powder, silicon carbide powder and strontium titanate powder; or fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; or such as carbon black powder, zinc oxide powder and tin oxide powder Conductivity imparting agent; organic and inorganic fine particles of opposite polarity may be used in a small amount as a developing property improver.

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 or dye as a colorant, a magnetic substance, a charge control agent, if necessary, other additives such as a Henschel mixer, After sufficiently mixing with a mixer such as a ball mill, melt kneading is performed using a hot kneader such as a heating roll, kneader, extruder to make the resins compatible with each other, and then a metal compound, a pigment, a dye, and a magnetic material are mixed. Can be dispersed or dissolved, and after cooling and solidification, pulverization and classification can be performed to obtain the magnetic developer according to the present invention.

Next, a method for measuring the characteristic value of the toner of the present invention will be described.

The weight average particle size (D ₄ ) of the developer can be measured by various methods, but in the present invention, the measurement was performed using a Coulter counter. That is, a Coulter counter TA-II type (manufactured by Coulter) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a PC 9801 personal computer (manufactured by NEC) were connected. A 1% NaCl aqueous solution is prepared using graded sodium chloride. As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and the measurement sample is further added to 2 to 20 m.
Add g. The electrolyte in which the sample is suspended is approximately 1
Dispersing process for ~ 3 minutes and the above Coulter Counter T
The particle size distribution of particles of 2 to 40 μm is measured based on the number by using a 100 μm aperture as an aperture by the A-II type, and the volume distribution and the number distribution of the particles of 2 to 40 μm are calculated, and the weight obtained from the volume distribution is calculated. The standard weight average particle size (D ₄ : the median value of each channel is a representative value of the channel) was determined.

In the present invention, the magnetic properties of the magnetic developer were measured using VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.).
It was determined from the result of measurement at room temperature with an external magnetic field of 1 kOe.

In the present invention, the content of the trivalent metal other than iron contained in the magnetic material is measured by the following method. 0.2 g of a magnetic substance is collected in a beaker, 15 ml of a 12 N hydrochloric acid aqueous solution is added, and the mixture is heated and stirred, and the reaction is continued until all are dissolved and become transparent. Water is added to the obtained liquid to make 100 ml, and the amount of the dissolved trivalent metal element other than iron is measured by plasma emission spectroscopy (ICP) using the sample liquid. The abundance of the trivalent metal element other than iron with respect to the weight of the magnetic substance is calculated using a calibration curve similarly measured using a standard solution of a trivalent metal element other than iron. Further, in order to determine the content of the trivalent metal element other than iron in the crystal lattice of the magnetic material, the magnetic material on the surface of the magnetic material is washed and removed in an aqueous sodium hydroxide solution having a pH of about 10, and then the content is determined as described above. 3 other than iron by plasma emission spectroscopy
What is necessary is just to measure the content of a valent metal element.

When analyzing the magnetic substance contained in the magnetic developer, 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, and a magnetic substance remaining on the filter is collected. The collected magnetic material is treated in an atmosphere at 600 ° C. to remove organic components, and the obtained magnetic material is analyzed by the above-described method to measure the abundance of trivalent metal elements other than iron. Is done.

In the present invention, the blackness of the magnetic developer is measured by the following method. An organic solvent such as xylene that dissolves the resin component of the magnetic developer was added to the magnetic developer, and the magnetic developer was dissolved such that the resin component of the magnetic developer was 20 parts by weight with respect to 80 parts by weight of the organic solvent. Prepare solution. The solution obtained by dissolving the resin component of the magnetic developer was coated on a PET OHP with a bar coater to a thickness of 10 μm.
It is quickly coated to a thickness of about μm, and this is used as a test piece for measurement. Place a sufficient number of blank papers on the back side of the OHP test piece and apply the high-speed color analyzer C
Measure color using A-35 (Murakami Color Research Laboratory)
The L ^* value, a ^* value, and b ^* value are respectively measured by the Lab space of ter, and the International Commission on Illumination (Commission)
Internationale del'Eclair
age, CIE) 1976 (L ^* , a ^* , b ^* ) is displayed in accordance with the uniform perceived color space.

On the other hand, the developer carrier of the image forming apparatus to which the magnetic developer of the present invention is applied is preferably covered with a resin layer containing conductive fine particles.

The surface roughness of the developer carrier is J
The IS center line average roughness (Ra) is preferably in the range of 0.2 to 3.5 μm. Ra is the current is less than 0.2μm
The charge amount on the image agent carrier increases, and the developability becomes insufficient. If Ra exceeds 3.5 μm, the current on the developer carrying member
There is a tendency for unevenness in the coating layer of the image agent to cause unevenness in density on the image.

As the conductive fine particles contained in the resin layer covering the surface of the developer carrying member, conductive metal oxides such as carbon black, graphite, conductive zinc oxide and the like and metal double oxides alone or in combination may be used. These are preferably used. Examples of the resin in which the conductive fine particles are dispersed include phenolic resins, epoxy resins, polyamide resins, polyester resins, polycarbonate resins,
Known resins such as polyolefin resin, silicone resin, fluorine resin, styrene resin, and acrylic resin are used. Particularly, a thermosetting or photocurable resin is preferable.

In the magnetic developer of the present invention, the member for regulating the magnetic developer on the developer carrier is regulated by an elastic member such as urethane or silicon which is in contact with the developer carrier via the developer. Is particularly preferable from the viewpoint of uniformly charging the magnetic developer.

Next, an example of the image forming method of the present invention will be specifically described with reference to the drawings.

FIG. 4 is a schematic diagram of an image forming apparatus used in the present invention. In FIG. 4, the image forming apparatus includes a developer carrier 5 disposed opposite to the electrostatic latent image carrier 1 and a developer regulating member 3 disposed such that a front end thereof is pressed against the developer carrier 5. These are disposed in a developing device 2 that contains a magnetic developer. An AC high-voltage power supply 6 and a DC high-voltage power supply 7 for applying a developing bias voltage are connected to the developer carrier 5. The developer carrier 5 has a plurality of magnetic poles (N1, S1, N2, S2) having different polarities and magnetic forces magnetized, and a fixed and supported magnet roll 4, and a cylindrical shape rotating around the magnet roll 4. With the rotation of the developing sleeve, the magnetic developer 8 is attracted and conveyed, the developer layer is formed, and the fog toner is pulled back. A charging bias is applied by a charging roller 11, a DC high-voltage power supply 12, and an AC high-voltage power supply 13 that are in contact with the outer periphery of the electrostatic latent image carrier 1, and the electrostatic latent image carrier 1 is charged. Then, the electrostatic latent image 9 is formed by exposing with a laser beam 14 and is reversely developed with a magnetic developer 8.

The developed visible image 10 on the electrostatic latent image carrier
Is transferred onto a transfer material 16 by a transfer roller 15 and fixed by a fixing device (not shown) to form a fixed image. Further, the developer partially left on the electrostatic latent image carrier is cleaned by a cleaning unit (not shown).

[0062]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Production Examples and Examples, but this does not limit the present invention in any way.

All parts in the following formulations are parts by weight.

(Magnetic Material Production Example 1) In a 4 liter three-necked flask, 0.35 mol /
1 liter of an aqueous solution of aluminum sulfate was mixed, and 1 liter of a 0.8 mol / l aqueous solution of ferrous sulfate was added thereto. The mixture was oxidized at about 80 ° C. while blowing an oxygen-containing gas while maintaining the pH at 10 to 12. After adjusting the pH of the reaction solution containing the obtained magnetic particles to 6 to 8, the magnetic particles were filtered, washed with water, dried and crushed to obtain a magnetic substance a.

The magnetic properties of the obtained magnetic body a were such that the saturation magnetization σs was 36 emu / s in a magnetic field of 1 kOe.
g, residual magnetization σr is 7.9emu / g, a coercive magnetic force Hc 1
It was 28 Oersted. Further, the content of the trivalent metal other than iron (the aluminum element in the present production example) contained in the magnetic material was 8%, and the FeO content was 24%.
Table 1 shows the results.

(Production Examples 2 to 3 of Magnetic Material) The concentrations of aluminum sulfate and an aqueous solution of sodium hydroxide were adjusted, and σs in a magnetic field of 1 k Oersted was 21 emu / g and 47 emu / g in the same manner as in Production Example 1 of magnetic material. Magnetic materials b and c were obtained.

Table 1 shows the magnetic properties, the content of the trivalent metal other than iron, and the FeO content of the obtained magnetic materials b and c at 1 kOersted.

(Magnetic Material Production Examples 4 to 6) Magnetic Material Production Examples 1 to 6
In the magnetic materials a to c obtained in step 3, after the magnetic particles are formed and washed with water, the magnetic particles are added to an aqueous alkaline solution having a pH of 10 or more to remove the excess iron other than the iron present on the surface of the magnetic particles. After removing the compound of a multivalent metal (which is considered to be a hydroxide or a hydrated oxide), it is again washed with water, separated by filtration, dried and crushed, and the magnetic substances d, e, and
f was obtained. Table 1 shows the magnetic properties, the content of trivalent metals other than iron, and the FeO content of these magnetic materials d to f at a magnetic field of 1 kOe.

(Comparative Production Example 1) 0.8 mol of an aqueous sodium hydroxide solution was added to a 4 liter three-necked flask.
/ L ferrous sulfate aqueous solution 1 liter mixed system (pH
8 to 10), the mixture was oxidized at about 80 ° C. while blowing steam and oxygen. The obtained black powder was filtered, washed with water, dried and crushed to obtain a magnetic substance g. Table 1 shows the magnetic properties, the content of trivalent metals other than iron, and the FeO content of the obtained magnetic material g under a magnetic field of 1 kOe.

(Comparative Production Example 2 of Magnetic Material) 0.8 mol of an aqueous sodium hydroxide solution was added to a 4 liter three-necked flask.
/ L ferrous sulfate aqueous solution 1 liter mixed system (pH
9 to 11) were oxidized at about 80 ° C. while blowing steam and oxygen. 0.04 mol / l at the end of oxidation
1 liter of aluminum sulfate aqueous solution
Was adjusted to 6 to 8 and further reacted. The obtained black powder was filtered, washed with water, dried and crushed to obtain a magnetic substance h. Table 1 shows the magnetic properties, the content of trivalent metals other than iron, and the FeO content of the obtained magnetic body h under a magnetic field of 1 kOe.

(Comparative Production Example 3 of Magnetic Material) In a 4 liter three-necked flask, 0.2 mol of an aqueous sodium hydroxide solution was added.
Per liter of an aqueous solution of zinc sulfate and mixed with 0.1 liter.
One liter of an aqueous 8 mol / l ferrous sulfate solution was added, and the reaction solution was oxidized at about 80 ° C. while blowing the oxygen-containing gas while maintaining the pH at 6 to 8. The obtained black powder was filtered, washed with water, dried and crushed to obtain a magnetic substance i containing about 10% by weight of zinc element. Table 1 shows the magnetic properties, the content of trivalent metals other than iron, and the FeO content of the obtained magnetic material i at 1 kOe.

[0072]

[Table 1]

<Developer Production Example 1> 100 parts of magnetic substance a of magnetic substance production example 1 100 parts of styrene-n-butyl acrylate copolymer (copolymerization ratio 8: 2, Mw = 260,000) Monoazo dye Iron complex (negative charge control agent) 2 parts ・ Low molecular weight polyolefin (release agent) 2 parts

The above materials were mixed in a blender,
Melted and kneaded with a twin-screw extruder heated to ℃, coarsely pulverized the cooled kneaded material with a hammer mill, finely pulverized the coarsely pulverized material with a jet mill, and classified the resulting finely pulverized material 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, coarse particles were removed with a 150-mesh sieve to obtain a magnetic developer A. The weight average particle size of the obtained magnetic developer A was 6.8 μm.

When the blackness of the magnetic developer was measured, L ^* = 20.7, a ^* = 0.00, b ^* = − 2.
The result was 10, showing good blackness. The above magnetic developer A
Table 2 shows the physical properties of the compound.

<Developer Production Example 2> • 150 parts of magnetic substance b of Magnetic Substance Production Example 1 • 100 parts of styrene-2 ethylhexyl acrylate-n-butyl maleate half ester copolymer (copolymerization ratio 7: 2: 1) , Mw = 220,000) ・ Chromium complex of monoazo dye (negative charge control agent) 0.8 part ・ Ethylene-propylene copolymer (Mw = 6000) 4 parts

Using the above components, a fine black powder was obtained in the same manner as in Production Example 1. 2.0% by weight of hydrophobic silica fine powder (same as in Production Example 1) and 0.3% by weight of conductive tin oxide fine powder (oxygen-deficient antimony-free oxidation Tin, average particle size 0.1 μm)
Magnetic developer B was obtained in the same manner as in Production Example 1. The weight average particle size of this developer was 5.1 μm.

When the blackness of the magnetic developer B was measured, L ^* = 20.9, a ^* = − 0.08, b ^* = −
2.25, indicating a good blackness. Table 2 shows the physical properties of the magnetic developer B.

<Developer Production Example 3> Developer Production Example 1 except that the magnetic material c obtained in Magnetic Material Production Example 2 was 60 parts and the amount of hydrophobic silica added was 0.6% by weight. In the same manner as in the above, magnetic developer C was obtained. Table 2 shows the physical properties of the obtained developer C.

<Developer Production Example 4>-120 parts of magnetic substance d-100 parts of polyester resin-2 parts of iron complex of monoazo dye (negative charge control agent)-2 parts of low molecular weight polyolefin (release agent)

The amount of hydrophobic silica added was 1.5% by weight,
A magnetic developer D was obtained in the same manner as in Developer Production Example 1 except for using the above materials. Table 2 shows the physical properties of the obtained magnetic developer D.
Shown in

<Developer Preparation Example 5> Developer Preparation Example 1 except that the magnetic material e obtained in Magnetic Material Preparation Example 5 was 140 parts and the amount of hydrophobic silica added was 1.5% by weight. In the same manner as in the above, magnetic developer E was obtained. Table 2 shows the physical properties of the obtained magnetic developer E.

<Developer Production Example 6> Developer Production Example 4 except that the magnetic material f obtained in Magnetic Material Production Example 6 was 120 parts and the amount of hydrophobic silica added was 1.8% by weight. In the same manner as in the above, magnetic developer F was obtained. Table 2 shows the physical properties of the obtained magnetic developer F.

<Developer Comparative Production Example 1> A magnetic developer G was obtained in the same manner as in Developer Production Example 1 except that 100 parts of the magnetic material g obtained in Magnetic Material Comparative Production Example 1 was used as the magnetic material. . Table 2 shows the physical properties of the obtained magnetic developer G.

<Developer Comparative Production Example 2> A magnetic developer H was obtained in the same manner as the developer production example 1 except that 100 parts of the magnetic material h obtained in the magnetic material comparative production example 2 was used as the magnetic material. . Table 2 shows the physical properties of the obtained magnetic developer H.

<Developer Comparative Production Example 3> A magnetic developer I was obtained in the same manner as in the developer production example 1 except that 100 parts of the magnetic material i obtained in the magnetic material comparative production example 3 was used as the magnetic material. . When the blackness of the magnetic developer I was measured, L ^* = 21.0, a ^* = 0.88, b ^* =-0.55
And showed a reddish black color. Table 2 shows the physical properties of the obtained magnetic developer I.

[0087]

[Table 2]

Example 1 The image forming apparatus shown in FIG. 4 was used.

OP having a diameter of 30 mm as an electrostatic latent image carrier
Dark portion potential Vd = -700 V, bright portion potential V using C drum
L = −210V. The gap between the photosensitive drum and the developing sleeve was 150 μm, the layer thickness of the developer was about 7 μm, and the JIS center line average roughness (Ra) was 0.8.
Using a developing sleeve in which a resin layer of μm is formed on an aluminum cylinder having a diameter of 16φ and having a mirror surface, a developing magnetic pole is 950 gauss, and a thickness of 1.0 m is used as a developer regulating member.
m, 15g of urethane rubber blade with free length of 10mm
A / cm linear pressure.

• 100 parts of phenolic resin • 90 parts of graphite (particle size: about 7 μm) • 10 parts of carbon black

Next, as a developing bias, a DC bias component Vdc = -510 V, an AC bias component Vmax = -680 V, Vmin = 0 V (Du) as shown in FIG.
ty ratio Vmax: Vmin = 3: 1), f = 1800H
z, and a transfer roller (made of ethylene-propylene rubber in which conductive carbon is dispersed, diameter 20 mm, contact pressure 5
0 g / cm), +2 kV is applied as a transfer bias,
The peripheral speed of the developing sleeve is set to be 150% of the peripheral speed of the photoreceptor, and the magnetic developer A of Developer Production Example 1 is used as a developer, and an image is formed at 15 ° C. and 10% RH. Done. As a result, as shown in Table 3, a good image having sufficient image density and high resolution was obtained. The resolution of the isolated dot latent image of 80 μm was also at a sufficiently good level.

The fog amount at this time is measured by a reflection densitometer (TOK
YO DENSHOKU CO. , LTD REF
LECTOMETE MODEL TC-6DS) (the worst value of the white background reflection density after printing is Ds,
D when the average reflection density of the paper before printing is Dr
When s-Dr was used as the fog amount, the image was as good as 1.2% (a fog amount of 2% or less was a good image substantially free of fog, and if it exceeded 5%, fog was conspicuous and unclear. Image).

Comparative Examples 1 and 2 Developers G and H of Comparative Production Examples 1 and 3
And image formation was performed using the same apparatus and conditions as in Example 1. As a result, as shown in Table 3, both the magnetic developers G and H had noticeable tails on the image. Also 80μ
The resolution of the m isolated dot latent image was also insufficient, and an image lacking sharpness was obtained. Further, since the developer spikes contacted the photoreceptor surface, the image was fogged.

Comparative Example 3 Using the developer I of the developer comparative production example 4 as the developer,
Image output was performed using the same apparatus and conditions as in Example 1. As a result, the image was conspicuous in red and lacked sharpness.

Comparative Example 4 In Example 1, the developing bias was changed to Vm as shown in FIG.
ax = −950 V, Vmin = −50 V (duty ratio V
max: Vmin = 1: 1), and an image was formed in the same manner as in Example 1. As a result, an unclear image with much fog (6.5% fog) was obtained on the image.

Example 2 In Example 1, the dark portion potential Vd was -500 V, the bright portion potential VL was -90 V, and the gap between the photosensitive drum and the developing sleeve was 100 μm. Next, the DC bias component Vdc = −360 V, the AC bias component Vmax = −480 V, Vmin = 0 V (duty ratio Vmax: Vmin = 3: 1), f = 2000 Hz as the developing bias, and the peripheral speed of the developing sleeve is the photosensitive member peripheral speed. , And image formation was performed in the same manner as in Example 1 except that the developer B of Developer Production Example 2 was used as the developer. As a result, good images as shown in Table 3 were obtained.

[0097] Using the developer magnetic developer C of Preparation 3, 4 and 5, D and E as Examples 3, 4 and 5 developers, as the developing bias f = 250
An image was formed using the same apparatus and conditions as in Example 1 except that the frequency was set to 0 Hz. As a result, good images as shown in Table 3 were obtained.

[0098] Using the developer F of developer Production Example 6 As Example 6 developer addition to setting the developing sleeve peripheral speed so that constant velocity relative to the photosensitive member peripheral speed in the same manner as in Example 1 Image was drawn. As a result, good images as shown in Table 3 were obtained.

Example 7 The procedure of Example 1 was repeated, except that the JIS center line average roughness (Ra) of the developing sleeve was set to 2.5 μm. Image was obtained.

[0100]

[Table 3]

[0101]

By using an image forming method which satisfies the above requirements of the present invention, it is possible to obtain a high-resolution, high-definition reproducible image having good blackness without fog and tailing. Was.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a conventional image forming apparatus using a one-component developer.

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

FIG. 3 is a schematic diagram of a developing bias used in a conventional image forming method.

FIG. 4 is a diagram illustrating an example of an image forming apparatus used in the present invention.

FIG. 5 is a schematic diagram of a developing bias used in the present invention.

FIG. 6 is a schematic diagram of a developing bias used in Comparative Example 4 .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrostatic latent image carrier 2 Developing device 3 Developer regulating member 4 Magnet roll 5 Developer carrier 6 AC high voltage power supply 7 DC high voltage power supply 8 Magnetic developer 9 Electrostatic latent image 10 Visible image 11 Charging roller 12 DC high voltage Power supply 13 AC high-voltage power supply 14 Laser beam 15 Transfer roller 16 Transfer material 100 Electrostatic latent image carrier 102 Developer carrier 103 Elastic blade 104 Magnet roller 114 Transfer charger 116 Cleaner 117 Primary charging roller 121 Laser generator 123 Laser beam 124 Register roller 125 Conveying belt 126 Fixing device 127 Developing device V _max Development promotion maximum voltage V _min Development pullback maximum voltage V _pp AC bias peak voltage V _cont Development contrast (V _L -V _DC ) f AC bias frequency T1 Development promotion period T2 Development pullback cycle _DC development DC voltage V _D on the drum non-image portion voltage V _L drum on the image portion Voltage

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-129655 (JP, A) JP-A-4-143774 (JP, A) JP-A-4-144924 (JP, A) JP-A-4-144 346356 (JP, A) JP-A-4-346357 (JP, A) JP-A-2-191964 (JP, A) JP-A-6-59501 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (5)

(57) [Claims] 1. An image forming apparatus, wherein an electrostatic latent image carrier is opposed to a developer carrier carrying a developer layer, and an electrostatic latent image formed on the electrostatic latent image carrier is developed by reversal development. In the method, the developer carrier has a surface roughness of JIS center line average roughness (R
a) is a first peak voltage that urges the developer from the developer carrier toward the visible portion of the electrostatic latent image, and the voltage level of the first peak voltage is 0.2 to 3.5 μm. A first peak voltage that is a level between the potential of the visible image portion and the potential of the electrostatic latent image background portion, and a second bias voltage that urges the developer in the direction from the electrostatic latent image visible portion toward the developer carrier. Developing an oscillating bias voltage having a second peak voltage whose voltage level is opposite to the voltage level of the first peak voltage with respect to the potential of the electrostatic latent image visible portion. Applied to the developer carrier and contains at least a binder resin and magnetic powder as a developer
A black magnetic developer, wherein the black magnetic developer has a weight average
The magnetic material contains 2 to 20% by weight of a trivalent metal other than iron, and has a saturation magnetization as of 20 to 50 emu / g in a magnetic field of 1 kOe; The chromaticity of the developer is represented by the following formula: −1.0 ≦ a ^* ≦ 0.8, −3.0 ≦ b ^* ≦ 0 , 13 ≦ L ^* ≦ 23 (where a ^* is (L ^* , a ^* , b ^* ) indicates chromaticity in the red-green direction in the uniform perceived color space, b ^* indicates chromaticity in the yellow-blue direction, and L ^* indicates lightness. Image forming method. 2. The image forming method according to claim 1, wherein the trivalent metal is aluminum. 3. The image forming method according to claim 1, wherein the developer carrier is covered with a resin layer containing conductive fine particles. 4. The image forming method according to claim 1, wherein the black magnetic developer contains an inorganic fine powder subjected to a hydrophobic treatment. 5. The image forming method according to claim 1, wherein the black magnetic developer contains a conductive fine powder.