JP3079404B2 - One-component magnetic developer and 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 electrostatic image developing developer for visualizing an electrostatic image in an image forming method such as electrophotography and electrostatic printing, and an image forming method.

[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 a configuration as shown in FIG. 1, for example. In FIG. 1, reference numeral 100 denotes a photosensitive drum (hereinafter, referred to as an electrostatic latent image carrier), around which a primary charging roller 1 is attached.
17, developing device 140, transfer charger 114, cleaner 11
6, a register roller 124 and the like are provided. Then, the electrostatic latent image carrier 100 is charged by the primary charging roller 117.

Then, the laser beam 123 is irradiated 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 nonmagnetic 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.

[0007] Further, in copiers, higher speed and more stable direction are always desired. In particular, the two-component developing system is mainly used for medium to high speed machines. This is because, with such a relatively large machine, the stability of the copied image for long-term use at high speed becomes important due to the size and weight of the developing device. Generally, the toner of the two-component developing system is colored with carbon black or the like, and the other components are mostly made of a binder resin.

[0008] Therefore, the toner particles are light and have no force to adhere to the carrier particles other than the electrostatic force, so that the toner is scattered particularly in development at a high speed, and the dirt on the optical lens, the original glass, the conveyance unit and the like in a long-term use. And the stability of the copied image may be impaired. Therefore, a developing method has been put to practical use in which a magnetic substance is contained in the toner to make the toner heavier and to adhere to the magnetic carrier particles by magnetic force in addition to electrostatic force, thereby preventing toner scattering. As described above, an image forming method using a one-component magnetic developer is becoming more and more important.

As for the printer device, LED and LBP printers have become the mainstream in the recent market, and the direction of technology has been increased to higher resolution, that is, the conventional 240,300 dpi has become 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 toners having a small particle diameter.

However, when the weight-average particle diameter of the toner becomes fine particles (generally 9 μm or less), the charged toner or fine powder adheres firmly to the electrostatic latent image carrier due to a force such as a mirroring force, and an electric field and With the force of the magnetic field, it is difficult to return the toner attached to the non-image portion on the electrostatic latent image carrier to the developer carrier. These toners are transferred onto a transfer material and become so-called fog, which degrades image quality.

In addition, recently, from the viewpoint of environmental protection, the primary charging and transfer process using a charging roller has been becoming mainstream from the primary charging and transfer process using corona discharge which has been conventionally used.

More specifically, a voltage is applied to a conductive roller serving as a charging member, and the roller is brought into contact with a photosensitive member serving as a member to be charged to charge the surface of the photosensitive member to a predetermined potential. For example, in Japanese Patent Publication No. 50-13661, a low voltage can be applied when charging a photosensitive member by using a roller having a core covered with a dielectric material made of nylon or polyurethane rubber.

Japanese Patent Application Laid-Open No. Sho 59-46664 uses an electrostatic image carrier that runs endless, such as a rotating cylinder or an endless belt, and presses a transfer device to which a bias is applied to press it. An arrangement has been proposed in which a transfer material is passed between the two to transfer the developer image on the electrostatic image holding member side onto the transfer material.

However, in such a transfer system that does not use corona discharge, the transfer member is brought into contact with the photoconductor at the time of transfer, so that the developer image formed on the photoconductor is transferred to the transfer material. There is a problem of so-called "missing transfer" in which a developer image is pressed against and a partial transfer failure occurs.

These problems are problems that need to be improved in order to obtain the above-described high-resolution and high-definition images.

[0016]

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 high-quality image which is faithful to a document and faithful to a signal, that is, faithful to a latent image and substantially free from fogging and scattering. To provide a developer and an image forming method with high resolution and high definition reproducibility, even in a copying process that does not use corona charging, there is no phenomenon of omission during transfer or a developer in which these developments are suppressed And an image forming method.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic latent image carrier formed on an electrostatic latent image carrier by opposing an electrostatic latent image carrier and a developer carrier carrying a developer layer. An image forming method for developing an image, comprising: a first peak voltage for urging a developer in a direction from a developer carrier toward a visible portion of an electrostatic latent image; A first peak voltage that is a level between the potential of the visible portion and the potential of the electrostatic latent image background portion, and a second biasing the developer in the direction from the visible portion of the electrostatic latent image toward the developer carrier. A developing bias voltage having a peak voltage and 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. In a developer for developing an electrostatic image used in an image forming method applied to a carrier, the developer At least a one-component magnetic developer comprising a binder resin and a magnetic powder, wherein the absolute value of the two-component tribo for the iron powder of the developer is | Qd |, 100 ≧ | Qd | ≧ 40 μc / g Is achieved by using a one-component magnetic developer.

When the developer carrying member is coated with a resin layer containing conductive fine particles and the absolute value of the triboelectricity by the suction method on the developer carrying member is | Qm |, preferably 1
5 ≧ | Qd | / | Qm | ≧ 2.5, more preferably 14
≧ | Qd | / | Qm | ≧ 3.5.

According to the present invention, the relationship between the developing bias applied to the developer carrier and the potential on the electrostatic latent image carrier is determined. The developing bias is applied so that the developer in the image portion and the non-image portion of the electrostatic latent image carrier is pulled back in the developing bias return period of the developing bias, and the developer is applied on the electrostatic latent image carrier. And a developing contrast sufficient to adhere to the image portion of the magnetic developer, and the absolute value | Qd | of the two-component tribo of the magnetic developer is 100 ≧ | Qd | ≧ 40.
By using a magnetic developer and an image forming method in which μc / g and 15 ≧ | Qd | / | Qm | ≧ 2.5, an image faithful to the electrostatic latent image formed on the electrostatic latent image carrier is obtained. Transfer of developer particles from the developer carrier without any shortage, well-balanced electrostatic adhesion between the three at the transfer site where transfer member / magnetic developer / electrostatic latent image carrier is present The fogging is achieved, and the background fogging and reversal fogging when using a fine particle size developer, which has been a problem in the past, are substantially prevented, and there is no scattering, and transfer is performed even in a copying process that does not use corona charging. An object of the present invention is to provide a high-resolution and high-definition image in which there is no hollow phenomenon or this phenomenon is suppressed.

In the present invention, | Qd | is 100 μc / g
If it exceeds 2,000, the image density tends to decrease in continuous copying / printing, and | Qd |
When | Qd | / | Qm | is greater than 15 or less than 2.5,
Since the relationship described above was broken, the developing rate was lowered, and further, the omission during transfer was liable to occur.

The electric field between the developer carrier and the image portion of the electrostatic latent image carrier is preferably at least 2.0 V / μm.
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.

The above-mentioned effects of the use of the magnetic developer of the present invention are as follows: an electrostatic latent image carrier having a radius of curvature of 50 mm or less, a developer carrier having a radius of curvature of 20 mm or less, and a transfer member having a radius of curvature of 30 mm or less. The combination is particularly good. This is considered to be due to the fact that the effects of the physical properties of the developer on development and transfer are increased by narrowing both the development region and the transfer region.

As the magnetic fine particles contained in the developer of the present invention, a substance which is magnetized when placed in a magnetic field is used, and powder of a ferromagnetic metal such as iron, cobalt, nickel or the like, or a magnet, γ- Alloys and compounds such as Fe ₂ O ₃ and ferrite can be used. The saturation magnetization s of the magnetic particles is 1K
50-100 emu / g under Oersted, especially 60-8
0 emu / g is preferred. These magnetic particles preferably have a BET specific surface area of 1 to ²⁰ m ² / g by a nitrogen adsorption method,
In particular, magnetic powders having a hardness of 2.5 to 12 m ² / g and a Mohs hardness of 5 to 7 are preferred.

The amount of the magnetic substance is preferably 5 to 60 parts by weight, particularly preferably 15 to 40 parts by weight, based on 100 parts by weight of the binder resin. If the amount is less than 5 parts by weight, the transportability is insufficient, and the developer layer on the developer carrier tends to be uneven, resulting in image unevenness. On the other hand, when the amount exceeds 60 parts by weight, omission during transfer tends to occur.

For example, by reducing the amount of the magnetic material, it is possible to weaken the magnetism per developer and to shorten the length of the developer on the developer carrier developing electrode, thereby making it possible to tail around the character, Scattering can be reduced and the development rate can be improved. However, when the magnetism is weakened, the force of pulling the developer back onto the developer carrier is weakened, so that the developer tends to adhere to the non-image area and so-called fogging tends to occur. Therefore, it is necessary to control the movement of the developer between the developer carrier and the electrostatic latent image carrier (SD interval) by the SD interval and bias conditions (wave type, duty, etc.). Particularly, a developer having a small particle size (a weight average particle size of about 4 to 9).
In the case of (μm), the developer tends to fly to the electrostatic latent image carrier as a group of particles, and it is important to set the developing bias to suppress the flight of the developer to the non-image area. The developing conditions used in the present invention are necessary from the viewpoint that the developer does not exert a flying force on the non-image portion of the electrostatic latent image carrier and a sufficient flying force on the image portion with respect to the developer. Is preferably set so that a slight pullback from the image portion is applied by the alternating electric field for the purpose of further clearing the edge of.

The weight average particle size of the developer of the present invention is as follows:
Good results were obtained at 4 to 10 μm, especially at 4.5 to 9 μm. When the weight average particle size is less than 4 μm, the aggregation of the developer becomes remarkable, and there is a problem in handling. Also,
If it exceeds 10 μm, the reproduction of a dot latent image or fine line of 100 μm or less is not sufficient.

Further, the surface roughness of the developer carrier used in the present invention is 0.2 to 0.2 JIS center line average roughness (Ra).
It is preferably in the range of 1.5 μm. Ra is 0.2
If it is less than μm, the charge amount Qm on the developer carrier increases,
Developability becomes insufficient. When Ra exceeds 1.5 μm,
The developer coat layer of the developer carrier becomes uneven, resulting in uneven density on an image.

As the conductive fine particles contained in the resin layer covering the surface of the developer carrier, conductive metal oxides such as carbon black, graphite, and conductive zinc oxide and metal double oxides may be used alone or in combination. Two or more are preferably used. Further, as the resin in which the conductive fine particles are dispersed, a phenolic 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. In particular, a thermosetting or photocurable resin is preferable.

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

The method of measuring Qd in the present invention will be described with reference to the apparatus for measuring the amount of triboelectric charge shown in FIG. 23 ° C, relative humidity 6
In a 0% environment, EFV200 / 300 (Powdertech) was used as a carrier, and a mixture of 9.5 g of a carrier and 0.5 g of a developer was placed in a polyethylene bottle having a volume of 50 to 100 ml and shaken by hand 50 times. I do.

Next, the mixture 1.0 to 1.0 was placed in a metal measuring container 22 having a 500-mesh screen 23 at the bottom.
1.2 g is put, and the metal lid 24 is closed. At this time, the weight of the entire measurement container 22 is weighed and set as W1 (g). next,
In the suction device 21 (at least a portion in contact with the measurement container 22 is an insulator), the pressure of the vacuum gauge 25 is adjusted to 250 mmAq by adjusting the air volume control valve 26 by suctioning from the suction port 27. In this state, suction is performed for one minute to remove the developer by suction. The potential of the electrometer 29 at this time is set to V (volt). Here, 28 is a capacitor whose capacity is C (μF). Further, the weight of the whole measurement container after suction is weighed to be W2 (g). The triboelectric charge amount Qd (μc / g) of this developer is calculated as in the following equation.

Qd = (CV) / (W1-W2) For the measurement of Qm in the present invention, a measuring container having a cylindrical filter paper is used instead of the 500 mesh screen, and the developer carrying agent is used instead of the metal lid 24. Attach a metal suction port that conforms to the shape of the body surface, and apply suction pressure so that the developer layer on the surface of the developer carrier immediately after image formation (preferably within 5 minutes) can be uniformly suctioned without excess or shortage. Adjust and aspirate developer. The weight of the developer sucked at this time is expressed as M
As (g), it is calculated by Qm = CV / M.

The kind of the binder resin used in the present invention is, for example, polystyrene, poly-p-chlorostyrene,
Styrene such as polyvinyltoluene and its substituted homopolymer; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene -Methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone Styrene-based copolymers such as copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally-modified phenolic resins, and natural-resin-modified malees Acid resin, acrylic tree , Methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethane, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resin, coumarone-indene resin, petroleum resin, or the like can be used. Also,
Crosslinked styrenic resins are also preferred binder resins.

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, dicarboxylic acids having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like, and substituted products thereof; for example, vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate and the like For example, ethylene-based olefins such as ethylene, propylene, butylene and the like; vinyl ketones such as vinyl methyl ketone and vinylhexyl 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 acid esters having two double bonds such as 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinylether, divinylsulfide and divinylsulfone; and compounds having three or more vinyl groups Can be used alone or as a mixture.

In the developer of the present invention, it is preferable to use a charge control agent in the developer particles by mixing (internal addition) or mixing with the developer particles (external addition). 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 charge can be further stabilized.

The following substances control the toner 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 control the toner to be positively charged.

For example, denatured products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonic acid, tetrabutylammonium tetrafluoroborate, and phosphonium analogs thereof Onium salts such as salts and their lake pigments, triphenylmethane dyes and these lake pigments,
Metal salts of higher fatty acids; dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide and the like; Organotin oxide; diorganotin borates such as dibutyl tin borate, dioctyl tin borate, dicyclohexyl tin borate; and the like, or a combination of two or more thereof. Among these, charge control agents such as nigrosine, quaternary ammonium salts, and triphenylmethane pigments are particularly preferably used.

The general formula

[0041]

Embedded image

[R ₁ : H, CH ₃ R ₂ , R ₃ : a substituted or unsubstituted alkyl group (preferably C ₁ -C ₄ )] monomer homopolymer: styrene or acrylate as described above And a copolymer with a polymerizable monomer such as methacrylic acid ester can be used as a positive charge control agent. In this case, these charge control agents also function as (all or part of) the binder resin.

The above-described charge control agent (having no action as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is
Specifically, it is preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge controlling agent is preferably used in an amount of 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) based on 100 parts by weight of the binder resin.

Further, as a coloring material which can be further added to the toner according to the present invention, conventionally known carbon black,
Copper phthalocyanine and the like can be used.

Further, it is more preferable to use a fine silica powder added to the developer of the present invention. Such a fine silica powder is a so-called dry process or fume generated by the vapor phase oxidation of a silicon halide. Both dry silica called do silica and so-called wet silica produced from water glass or the like can be used, but there are few silanol groups on the surface and inside the silica fine powder, and Na ₂ O, S
Towards O ₃ dry silica without producing residues ² and the like are preferable.

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 production process. And also includes them. The particle diameter is preferably in the range of 0.001 to 2 μm as an average primary particle diameter, and particularly preferably 0.002 to 2 μm.
It is preferable to use a silica fine powder within a range of 0.2 μm. For the hydrophobizing treatment, conventionally known hydrophobizing agents and methods such as a silane coupling agent and silicone oil are used.

The developer of the present invention may be added at the time of further addition, for example, as a fixing aid (for example, low molecular weight polyethylene) or a metal such as tin oxide as a conductivity-imparting agent, as long as it does not substantially adversely affect the developer. An oxide or the like may be added.

The weight average particle diameter (D ₄ ) of the toner can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

That is, a Coulter Counter TA-II type (manufactured by Coulter Inc.) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number distribution and a volume distribution and a PC-9801 personal computer (NE) were used.
C) and a 1% NaCl aqueous solution is prepared as the electrolytic solution using primary sodium chloride. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, is used as a dispersant in 100 to 150 ml of the electrolytic aqueous solution.
５5 ml, and 2-20 mg of the measurement sample (about 30,000 to about 300,000 particles) are added. The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm based on the number was measured using the Coulter Counter TAII, using a 100 μ aperture as an aperture. Measure 2 to 40μ
The volume distribution and the number distribution of the m particles were calculated, and the weight-average weight-average diameter (D ₄ ) (the median value of each channel was taken as the representative value of the channel) determined from the volume distribution.

In producing the developer according to the present invention,
A method in which the constituent materials are thoroughly kneaded with a hot kneader such as a hot roll, kneader, extruder, etc., and then obtained by mechanical pulverization and classification, or a method in which the materials are dispersed in a binder resin solution and then spray-dried. Or
Each method can be applied, such as a polymerization developer manufacturing method in which a predetermined material is mixed with a monomer to form a binder resin to form an emulsified suspension and then polymerized to obtain a developer.

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).

[0054]

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.

Production Example 1 Styrene-n-butyl acrylate copolymer 100 parts (copolymerization weight ratio 8: 2 Mw = 260,000) Magnetic iron oxide 30 parts (BET value 6.5 m ^{2 /} g, σs = 65.6 emu) / G) Negative charge control agent (monoazo dye-based iron complex) 2 parts Ethylene-propylene copolymer (Mw = 6000) 3 parts

The above mixture is melt-kneaded with a twin-screw extruder heated to 140 ° C., and after cooling the kneaded material, coarsely pulverized by a hammer mill, and the coarsely pulverized material is finely pulverized by a jet mill. The material is subjected to air classification and the weight average particle size (D
₄ ) A negatively chargeable magnetic toner of 7.0 μm was obtained.

A hydrophobic silica fine powder (hexamethyldisilazane-treated BET value 200 m
^The mixture to which 0.8 part ( ^{2 /} g) was added was mixed with a Hexchel mixer to obtain a developer (1). | Qd | =
It was 62.5 μc / g.

Production Example 2 Styrene-2-ethylhexyl acrylate-n-butyl maleate half ester copolymer 100 parts (copolymerization weight ratio 7: 2: 1 Mw = 220,000) Magnetic iron oxide 40 parts (BET value 6.5 m) ^{2 /} g, σs = 65.6 emu / g) Negative charge control agent (monoazo dye-based chromium complex) 0.5 part Low molecular weight polypropylene (Mw = 6000) 3 parts

The above components were used in the same manner as in Production Example 1 to obtain a negatively chargeable magnetic toner having a weight average particle size (D ₄ ) of 5.5 μm.

A hydrophobic silica fine powder (polydimethylsiloxane-treated BET value 250 m
^The mixture to which 1.5 parts of ( ^{2 /} g) was added was mixed with a Henschel mixer to obtain a developer (2). | Qd | =
It was 77.5 μc / g.

Production Example 3 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5 Mw = 290,000) Magnetic iron oxide 15 parts (BET value 5.5 m ^{2 /} g, σs = 68.5 emu) / G) Negative charge control agent (monoazo dye-based iron complex) 2 parts Ethylene-propylene copolymer (Mw = 4000) 6 parts Carbon black 5 parts

A negatively chargeable magnetic toner having a weight average particle size (D ₄ ) of 7.5 μm was obtained in the same manner as in Production Example 1 using the above components.

A hydrophobic silica fine powder (hexamethyldisilazane-treated BET value 200 m
^The mixture to which 1.0 part ( ^{2 /} g) was added was mixed with a Henschel mixer to obtain a developer (3). | Qd | =
It was 94.5 μc / g.

Production Example 4 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5 Mw = 290,000) Magnetic iron oxide 60 parts (BET value 6.5 m ^{2 /} g, σs = 65.6 emu) / G) Negative charge control agent (monoazo dye-based iron complex) 1 part Low molecular weight polypropylene (Mw = 6000) 3 parts

A negatively chargeable magnetic toner having a weight average particle diameter (D ₄ ) of 10.5 μm was obtained in the same manner as in Production Example 1 using the above components.

A hydrophobic silica fine powder (hexamethyldisilazane-treated BET value 250 m
^{2 /} g) The mixture to which 0.6 part was added was mixed with a Henschel mixer to obtain a developer (4). | Qd | =
It was 33.5 μc / g.

Production Example 5 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5 Mw = 290,000) Magnetic iron oxide 5 parts (BET value 6.5 m ^{2 /} g, σs = 65.6 emu) / G) Negative charge control agent (monoazo dye-based iron complex) 1 part Low molecular weight polypropylene (Mw = 6000) 4 parts

By using the above components in the same manner as in Production Example 1, a negatively chargeable magnetic toner having a weight average particle size (D ₄ ) of 4.5 μm was obtained.

A hydrophobic silica fine powder (hexamethyldisilazane-treated BET value 200 m
^{2 /} g) was mixed with a Henschel mixer to obtain a developer (5). | Qd | =
It was 104.5 μc / g.

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

The electrostatic latent image carrier 1 has a diameter of 30 m.
m OPC drum, dark potential V _D = −700 V,
The light portion potential _{VL was set to} -150V. The distance between the electrostatic latent image carrier and the developer carrier was 150 μm, and the developer carrier 5
Using a developing sleeve in which a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 0.8 μm having the following configuration is formed on a mirror-finished aluminum cylinder having a diameter of 16φ, a developing magnetic pole 850 is used. A Gaussian, urethane rubber blade having a thickness of 1.0 mm and a free length of 10 mm as a developer regulating member 3 was brought into contact with the developer at a linear pressure of 15 g / cm.

Phenol resin 100 parts Graphite (particle size: about 7 μm) 90 parts Carbon black 10 parts

Next, as a developing bias, a DC bias component V _DC = -440 V, an AC bias component V _max = -690 V, V _min = -90 V (Dut) as shown in FIG.
y ratio T1: T2 = 7: 5), f = 1000 Hz, and the transfer roller 15 (ethylene-
Made of propylene rubber, diameter 20mm, contact pressure 50g / c
m), +2 KV is applied as a transfer bias, and the developer (1) of Production Example 1 is used as the developer, and the temperature is 23 ° C. and 65% R
3000 images were output in an H environment. As a result, even after continuous printing of 3000 sheets, a good image was obtained without any omission during transfer and without scattering on the image as shown in FIG. 7A. The fogging amount at this time was measured using a reflection densitometer (TOKYO DENSHOKU CO., LTD. REFLECOMETER MODEL TC-
6DS) (the worst value of the reflection density of the white background after printing is Ds, and the average reflection density of the paper before printing is Dr.
Ds-Dr at the time of was set as the fog amount),
It was as good as 1.5%. (A fogging amount of 2% or less is a good image having substantially no fogging, and a fogging amount of more than 5% is an unclear image with noticeable fogging.)
The dot latent image was also sufficient. Also, | Qd | /
| Qm | = 3.7.

Example 2 An image was formed in the same manner as in Example 1 except that the developer was changed to the developer (2) of Production Example 2 and that f was set to 2500 Hz. A good image was obtained with a fogging amount of 1.0%, no omission during transfer, and no scattering. Also, the resolution of a one-dot latent image of 80 μm was sufficient. At this time, | Qd | / | Qm | = 5.0.

Example 3 An image was formed in the same manner as in Example 1 except that the developer was changed to the developer (3) of Production Example 3. The fog amount was 3.8%. A good image was obtained without any omission during transfer and no scattering. Also, the resolution of a one-dot latent image of 80 μm was sufficient. Also. | Qd at this time
| / | Qm | = 9.7.

Example 4 An image was formed in the same manner as in Example 1 except that the JIS center line average roughness (Ra) of the developing sleeve was set to 2.5 μm. A good image was obtained with a fog amount of 4.6%, no omission during transfer, and no scattering. Also, the resolution of a one-dot latent image of 80 μm was sufficient. At this time, | Qd | / | Qm | was 5.8.

Comparative Example 1 An image was formed in the same manner as in Example 1, except that the developer was changed to the developer (4) of Production Example 4. Although it was as good as 8%, dropout and scattering occurred during transfer as shown in FIG. 7B. Also,
The resolution of a one-dot latent image of 80 μm was also insufficient. At this time, | Qd | / | Qm | = 4.0.

Comparative Example 2 An image was formed in the same manner as in Example 1 except that the developer used in Production Example 5 was changed to the developer (5). Is 7.5% (impractical level)
Met. In addition, a decrease in image density and uneven toner coating on the developing sleeve (density unevenness in a solid portion on the image) were observed, and the resolution of a one-dot latent image of 80 μm was insufficient. At this time, | Qd | / | Qm | = 6.
It was 3.

[0080] At a Comparative Example 3 Example 1, V _max = -840V as shown a developing bias to FIG 6, V _min = -40V (Duty ratio T
1: T2 = 1: 1), and an image was formed in the same manner as in Example 1. As a result, an unclear image with a large amount of fog (a fog amount of 5.9%) was obtained. At this time, | Qd | / | Qm | = 3.4.

[0081]

As described above, according to the present invention, the relationship among the dark portion potential V _D , the bright portion potential _VL , the maximum development promotion voltage V _max , and the maximum development pull-back voltage V _min on the electrostatic latent image carrier. To
| V _D | ≧ | V _max | and | V _L | ≧ | V _min |
During fogging, scattering, and transfer, a single-component magnetic development in which 0 ≧ | Qd | ≧ 40 μc / g and an image forming method using a developer carrier satisfying 15 ≧ | Qd | / | Qm | ≧ 2.5 It has become possible to achieve image formation with high resolution and high definition reproducibility without omission.

[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 3.

FIG. 7 is a schematic diagram showing an image state.

FIG. 8 is an explanatory diagram of a frictional charge amount measuring device.

[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 light 15 Transfer roller 16 Transfer material 21 Suction machine 22 Measuring vessel 23 Screen 24 Lid 25 Vacuum gauge 26 Air flow control valve 27 Suction port 28 Capacitor 29 Electrometer 100 Electrostatic latent image carrier 102 Developer carrying Body 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 Conveyor belt 126 Fixing device 127 Developer V _max Development promotion maximum voltage V _min Development pullback maximum voltage V _pp AC buy Scan peak voltage V _cont development contrast (V _L -V _DC) f AC bias frequency T1 development accelerator period T2 developing retraction cycle V _DC development DC voltage V _D on the drum non-image portion voltage V _L drum on the image portion Voltage

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Yoshida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-4-352170 (JP, A) JP-A-60 −117255 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/083 G03G 13/08 G03G 15/06 101 G03G 15/09 101

Claims (2)

(57) [Claims] 1. An image forming method for developing an electrostatic latent image formed on an electrostatic latent image carrier by causing an electrostatic latent image carrier and a developer carrier carrying a developer layer to face each other. A first peak voltage for urging the developer from the developer carrier toward the visible portion of the electrostatic latent image, the voltage level of which is the potential of the visible portion of the electrostatic latent image and the background of the electrostatic latent image. And a second peak voltage that urges the developer in a direction from the visible portion of the electrostatic latent image toward the developer carrier, and the voltage level is The image forming method of applying an oscillating bias voltage having a second peak voltage located on the side opposite to the voltage level of the first peak voltage with respect to the potential of the visible portion of the electrostatic latent image to the developer carrier. In the developer for developing an electrostatic image, the developer is at least composed of a binder resin and a magnetic powder. Is a one-component magnetic developer, wherein the absolute value of a two-component tribo for iron powder of the developer is | Qd |
Where: 100 ≧ | Qd | ≧ 40 μc / g. 2. An image forming method for developing an electrostatic latent image formed on an electrostatic latent image carrier by causing an electrostatic latent image carrier and a developer carrier carrying a developer layer to face each other. A first peak voltage for urging the developer from the developer carrier toward the visible portion of the electrostatic latent image, the voltage level of which is the potential of the visible portion of the electrostatic latent image and the background of the electrostatic latent image. And a second peak voltage that urges the developer in a direction from the visible portion of the electrostatic latent image toward the developer carrier, and the voltage level is In the image forming method, an oscillating bias voltage having a second peak voltage located on the opposite side of the voltage level of the first peak voltage with respect to the potential of the visible portion of the electrostatic latent image is applied to the developer carrier. The developer is at least a one-component magnetic developer comprising a binder resin and a magnetic powder; When the absolute value of the two-component triboelectric component with respect to the iron powder of the developer is | Qd |, 100 ≧ | Qd | ≧ 40 μc / g, and the developer carrier is covered with a resin layer containing conductive fine particles. Wherein the absolute value of the triboelectric charging method on the developer carrier is | Qm |, where 15 ≧ | Qd | / | Qm | ≧ 2.5.