JP2000250269A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress the rubbing flaws of a transporting belt and intermediate transfer belt by the magnetic carrier in a two-component developer by using the resin magnetic carrier having a binder resin and cores consisting of a magnetic metal oxide and nonmagnetic metal oxide as the magnetic carrier. SOLUTION: The resin magnetic carrier which has the binder resin and the cores consisting of the magnetic metal oxide and nonmagnetic metal oxide and is formed by a method including or not including a polymerization method is used as the magnetic carrier. This resin magnetic carrier is formed to a spherical shape in its shape has the less friction to the transporting belt 130. Since the surface is soft, the magnetic carrier is transported by the transporting belt 130 and the flawing of the surface of the transporting belt 130 by the contact with photosensitive drums 3a to 3d or the rubbing with the cleaner 22 of the transporting belt 130 is substantially obviated. Then, the rear staining of the image or transfer defect by the cleaning defect of the transporting belt 130 is prevented and the image having good quality may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus for forming a toner image on an image carrier and transferring the toner image to a recording material to obtain an image. .

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units have been provided, toner images of different colors are formed in each image forming unit, and the toner images are sequentially superimposed on the same recording material and transferred.
Various image forming apparatuses for forming a color image have been proposed.

Under such circumstances, an electrophotographic color copying machine using an endless recording material carrying member is used for high-speed recording.

An example of a color electrophotographic recording apparatus will be described with reference to FIG. 2. First, second, third, and fourth color electrophotographic recording apparatuses are provided in the apparatus.
The image forming units Pa, Pb, Pc, and Pd are arranged in parallel, and toner images of different colors are formed in the respective image forming units Pa to Pd through processes of forming a latent image, developing, and transferring.

The image forming units Pa, Pb, Pc, and Pd are each a dedicated image carrier, in this example, an electrophotographic photosensitive drum 3
a, 3b, 3c, 3d.
A toner image of each color is formed on b, 3c and 3d. A conveyance belt (transfer belt) 130 of a recording material carrier is provided adjacent to each of the photosensitive drums 3a, 3b, 3c, and 3d, and a toner image of each color formed on the photosensitive drums 3a, 3b, 3c, and 3d is formed. The image is superimposed and transferred onto the recording material P carried and conveyed on the conveyance belt 130.

The recording material P on which the toner images of each color are transferred is
After the toner image is fixed by heat and pressure in the fixing device 9, the toner image is discharged out of the device as a color recorded image.

A heater (not shown) is disposed inside each of the photosensitive drums 3a, 3b, 3c and 3d.
In order to prevent the surface of the photosensitive drum from becoming wet and reducing the surface resistance, the surface of the photosensitive drum is heated from the inside so that the surface temperature is always maintained at 40 ° C. These photosensitive drums 3a, 3b, 3
Exposure lamps 111a, 1
11b, 111c, 111d, drum chargers 2a, 2
b, 2c, 2d, potential sensors 113a, 113b, 1
13c, 113d, developing devices 1a, 1b, 1c, 1d, contact-type transfer chargers 24a, 24b, 24c, 24d, and cleaners 4a, 4b, 4c, 4d, and a light source (not shown) above the apparatus A device and a polygon mirror 117 are provided.

The laser light emitted from the light source device is rotated and scanned by the polygon mirror 117, the light beam of the scanning light is deflected by the reflection mirror, and the bus direction of each of the photosensitive drums 3a, 3b, 3c, and 3d by the fθ lens. The photosensitive drums 3a, 3b, 3c, 3
An electrostatic latent image corresponding to the image signal is formed on d.

The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners, respectively, by a supply device (not shown). The developing devices 1a, 1b, 1c, and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualize the latent images as cyan, magenta, yellow, and black toner images.

The recording material P is stored in a recording material cassette 10. The recording material P is supplied from there to a conveyor belt 130 via a plurality of conveyor rollers and registration rollers 12, and is conveyed by the conveyor belt 130 so that the photosensitive drums 3a, 3a
These are sequentially sent to the transfer sections facing b, 3c and 3d.

The transport belt 130 is made of polyethylene terephthalate resin (PET), polyvinylidene fluoride resin,
It is made of a sheet of a dielectric resin such as a polyurethane resin, and its both ends are overlapped and joined to form an endless shape, or a seamless (seamless) belt is used.

When the transport belt 130 is rotated by the driving roller 13 and is confirmed to be at a predetermined position, the recording material P is transferred from the registration roller 12 to the transport belt 13.
0 and is conveyed to the transfer section of the first image forming section Pa. At the same time, the image writing signal is turned on, and an image is formed on the photosensitive drum 3a of the first image forming unit Pa at a certain timing based on the signal.

Then, at the lower transfer section of the photosensitive drum 3a,
The transfer charger 24a in contact with the rear surface of the conveyor belt 130 applies an electric field or electric charge to the photosensitive drum 3a.
The first color toner image formed thereon is transferred onto the recording material P. By this transfer, the recording material P is firmly held on the conveyor belt 130 by electrostatic attraction, and the second image forming unit P
It is conveyed after b.

Image formation and transfer in the second to fourth image forming units Pb to Pd are performed in the same manner as in the first image forming unit Pa.
Next, the recording material P on which the four color toner images have been transferred is separated from the end of the transport belt 130 by removing the charge by the separation charger 32 at the downstream portion of the transport belt 130 in the transport direction and attenuating the electrostatic attraction force. . The recording material P detached from the transport belt 130 is transported to the fixing device 9 by the transport unit 62.

The fixing device 9 includes a fixing roller 51, a pressure roller 52, heat-resistant cleaning members 54 and 55 for cleaning each of them, heaters 56 and 57 installed in the rollers 51 and 52, and a fixing roller. An application roller 59 that applies a release agent oil such as dimethyl silicone oil to the surface 51, an oil reservoir 53, and a thermistor 58 that detects the temperature of the surface of the pressure roller 52 and controls the fixing temperature.
It is composed of

The recording material P to which the four color toner images have been transferred is
By the fixing, the color mixture of the toner image and the fixation to the recording material P are performed to form a full-color copy image, and the image is discharged to the paper discharge tray 63.

The photosensitive drum 3a, 3b, 3c, 3d after transfer (using a Vickers hardness of 220 N / mm ² )
Are cleaned and removed by the cleaners 4a, 4b, 4c and 4d, respectively, and are prepared for the formation of the next latent image. The cleaning web (nonwoven fabric) 19 is brought into contact with the surface of the conveyor belt 130 by the cleaner 22 to wipe off toner and other foreign matters remaining on the conveyor belt 130.

The developer used in the developing devices 1a to 1d will be described.

The developing device carries a dry type developer on a developing sleeve which is a developer carrying member, and conveys the developer to the vicinity of the surface of the photosensitive drum by rotation of the developing sleeve. A method of visualizing an electrostatic latent image on a photosensitive drum with a conveyed developer while an alternating electric field is applied to the photosensitive drum is well known.

As a developing method, for example, a magnetic brush of a two-component developer composed of carrier particles and toner particles is formed on the surface of a developing sleeve in which a magnet is arranged inside by a magnetic force, and this magnetic brush is minutely combined with the developing sleeve. By rubbing or approaching the photosensitive drum opposed to the photosensitive drum at an appropriate distance, and applying an alternating electric field between the developing sleeve and the photosensitive drum (SD gap), the toner is transferred from the magnetic brush on the developing sleeve to the photosensitive drum. A so-called magnetic brush developing method in which development in which transition and reverse transition are repeated is known (for example, Japanese Patent Application Laid-Open No. 55-320608).
2, see JP-A-59-165082).

A non-contact alternating electric field developing method using a two-component developer for the purpose of simple color development or multiple development is also known (for example, JP-A-56-14268,
JP-A-58-68051, JP-A-56-144452
JP-A-59-181362, JP-A-60-176
No. 069).

[0022]

The magnetic carrier particles used in the above-mentioned two-component developer have conventionally used magnetic metal oxides in many cases. Ideally, these carrier particles should be mixed with the toner particles to form a magnetic brush on the developing sleeve, and only the toner particles should be transferred onto the photosensitive drum by the action of the developing electric field,
In practice, even a very small amount of carrier particles are transferred onto the photosensitive drum.

This phenomenon may occur over the entire width where the developer (magnetic carrier) is present. That is, since the effective development width is usually designed to be sufficiently larger than the image width, the width of the transport belt 130 is reduced. Occurs almost all over the area.

The magnetic carrier transferred to the photosensitive drum contacts a transfer material such as paper at a transfer portion, and a part of the magnetic carrier adheres to the transfer material and is transported together with the transfer material.

Since the carrier conveyed by the conveyor belt 130 is a powder mainly composed of metal oxide, the carrier is brought into contact with the photosensitive drums 3a to 3d or rubbed with the cleaner 22 of the conveyor belt. As a result, the transfer belt 130 made of a resin sheet may be scratched.

The sliding abrasion of the transport belt, depending on its size and depth, may cause back contamination of the image and transfer failure due to poor cleaning of the transport belt.

Such a problem of abrasion of the belt by the magnetic carrier of the two-component developer similarly occurs in the intermediate transfer belt in the intermediate transfer type image forming apparatus.

In some cases, a peripheral speed difference is intentionally provided between the photoreceptor and the conveyance belt or between the photoreceptor and the intermediate transfer member in order to improve the transferability of the toner. In such a case, the above-mentioned rubbing scratches are more likely to occur, and even the photoconductor may be damaged.

An object of the present invention is to suppress the abrasion of a transfer belt or an intermediate transfer belt caused by a magnetic carrier in a two-component developer, thereby to prevent back contamination of an image or transfer failure due to cleaning failure of these belts. An object of the present invention is to provide an image forming apparatus capable of obtaining a good quality image.

[0030]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier, developing means for developing the electrostatic latent image formed on the image carrier using a two-component developer containing a non-magnetic toner and a magnetic carrier, and visualizing the image as a toner image; And a belt-like transfer material transporting unit that rotates in contact with the image carrier and transports the toner image on the image carrier in the transfer unit. An image forming apparatus provided with a transfer unit for transferring to the transfer material, wherein the magnetic carrier has a binder resin and a core made of a magnetic metal oxide and a non-magnetic metal oxide, with or without a polymerization method. An image forming apparatus, wherein the resin magnetic carrier is formed.

According to the present invention, preferably, the magnetic carrier is a resin magnetic carrier formed by a method including a polymerization method, and has a shape factor SF-1 of 100 to 140;
F-2 is 100 to 120. Further, a plurality of the image bearing members, the developing unit, and the transfer unit are provided along a rotation direction of the transfer material conveying unit. The transfer unit is a contact type transfer unit in which the transfer unit comes into contact with the transfer material conveying unit from the back surface side opposite to the transfer material conveying side. The contact pressure of the transfer unit with the transfer material conveying unit is 10 to 15 gf / cm.

In another aspect of the present invention, an image carrier and an electrostatic latent image formed on the image carrier are developed using a two-component developer containing a non-magnetic toner and a magnetic carrier. Developing means for visualizing the toner image as a toner image, a belt-shaped intermediate transfer member rotating in contact with the image carrier, and the image carrier at a primary transfer portion where the image carrier and the intermediate transfer member face each other. Primary transfer means for transferring the upper toner image onto the intermediate transfer member, and secondary transfer means for transferring the toner image on the intermediate transfer member to a transfer material in a secondary transfer portion facing the intermediate transfer member. Wherein the magnetic carrier is a resin magnetic carrier formed by a method including or not including a polymerization method, having a core made of a binder resin and a magnetic metal oxide and a non-magnetic metal oxide. An image forming apparatus characterized in that .

According to the present invention, preferably, the magnetic carrier is a resin magnetic carrier formed by a method including a polymerization method, and has a shape factor SF-1 of 100 to 140, S
F-2 is 100 to 120. The image carrier, the developing means, and the developing device may be arranged along a rotation direction of the intermediate transfer body.
A plurality of next transfer units are provided. The primary transfer means includes:
This is a contact type transfer unit that comes into contact with the intermediate transfer body from the back side opposite to the toner image transfer side. The contact pressure of the primary transfer means with the intermediate transfer member is 10 to 15 gf / c
m. The secondary transfer unit is a contact-type transfer unit that comes into contact with the intermediate transfer body from the back surface side of the transfer material opposite to the toner image transfer side via the transfer material. 2 above
The contact pressure of the next transfer unit with the intermediate transfer member is 20 to 30 g.
f / cm.

[0034]

Embodiments of the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a configuration diagram showing an image forming apparatus to which the present invention can be applied.

According to the present invention, in an image forming apparatus having a belt means such as a transfer material conveying belt or an intermediate transfer belt, a specific magnetic carrier is defined as a magnetic carrier in a two-component developer used in a developing means. Another object of the present invention is to prevent the belt from being rubbed and scratched by the magnetic carrier, thereby preventing the image from being stained on the back side of the image and the transfer failure due to the belt cleaning failure.

This embodiment was applied to an image forming apparatus having a transfer belt 130 as a transfer material carrier as shown in FIG. The description of each part of the image forming apparatus has been already described in the related art, and thus will not be described. Hereinafter, FIG. 1 will be referred to as needed in the description of the present invention.

The magnetic carrier of the two-component developer used in the present invention will be described in detail. In the present invention, a resin magnetic carrier produced by a polymerization method and having a core made of a binder resin, a magnetic metal oxide and a non-magnetic metal oxide is used as the magnetic carrier.

[0039] In the present invention, as a metal oxide, magnetite represented by the general formula MO · Fe ₂ O ₃ exhibiting magnetism (or MFe ₂ O _4), it can be preferably used such as ferrite. Here, M is a divalent or monovalent metal ion Mn, Fe, Ni, Co, Cu, Mg, Zn,
Cd, Li and the like correspond, and M can be used alone or as a plurality of metals. For example, magnetite, γ
Examples include iron oxides such as iron oxide, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, and Cu-Zn ferrite.

The above-mentioned metal oxide can be used by dispersing the metal oxide alone in the resin.
At least two or more metal oxides can be used in a mixed state. In this case, in addition to the above magnetic metal oxide, Mg, Al, Si, Ca, Sc, Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Z
Non-magnetic metal oxides using a single metal or a plurality of metals such as r, Nb, Mo, Cd, Sn, Ba, and Pb, and metal oxides exhibiting the above magnetism can be used. For example, non-magnetic metal oxides such as Al ₂ O ₃ , SiO ₂ , CaO,
_{TiO 2, V 2 O 5,} CrO 2, Fe 2 O 3, CoO, Ni
O, CuO, ZnO, SrO, Y ₂ O ₃ , ZrO _{3 and the} like can be used.

In the above case, it is more preferable to use particles having similar specific gravities and shapes, since the adhesion to the binder resin and the carrier strength are increased. For example magnetite and hematite, magnetite and SiO _2, magnetite and Al ₂ O _3, magnetite and TiO _2, magnetite and Ca-Mn-based ferrite, and magnetite Ca-
Mg-based ferrite or the like can be preferably used.
Among them, a combination of magnetite and hematite is preferable from the viewpoint of cost and carrier strength.

When the above-mentioned metal oxide is dispersed in a resin to form a core, the number-average particle diameter of the metal oxide exhibiting magnetism varies depending on the carrier particle diameter, but is preferably from 0.02 to 2 μm. Can be used. When two or more metal oxides are used in a dispersed state, a metal oxide having a number average particle diameter of 0.05 to 5 μm can be used. In this case, the particle diameter ra of the metal oxide particles exhibiting magnetism
Ratio rb / r of the particle diameter rb of the other metal oxide particle to the other
a is preferably 1.0 to 5.0 times. If the particle diameter ratio rb / ra is 1.0 or less, metal oxide particles having low specific resistance are likely to appear on the carrier surface, and the resistance of the carrier core cannot be sufficiently increased. On the other hand, if the particle size ratio rb / ra exceeds 5.0 times, the incorporation of metal oxide particles into the resin will not be successful, and the strength of the carrier will decrease.

The metal oxide contained in the metal oxide-dispersed resin core of the resin magnetic carrier used in the present invention is:
It is preferable that the lipophilic treatment has been performed. When the lipophilic metal oxide is dispersed in a binder resin to form core particles, the metal oxide can be uniformly and densely incorporated into the binder resin. In particular, when the core particles are formed by a polymerization method, it is important that the particles are subjected to lipophilic treatment in order to obtain spherical particles having a smooth surface and to sharpen the particle size distribution.

In the lipophilic treatment, the metal oxide is treated with a coupling agent such as a silane coupling agent or a titanate coupling agent, or the metal oxide is dispersed in an aqueous solvent containing a surfactant. To make the surface lipophilic.

As the silane coupling agent mentioned herein, those having a hydrophobic group, an amino group or an epoxy group can be used. Examples of the silane coupling agent having a hydrophobic group include vinyl trichlorosilane,
Vinyl tris (β-methoxy) silane and the like can be mentioned. Examples of silane coupling agents having an amino group include γ-aminopropylethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane. , N-phenyl-γ-aminopropyltrimethoxysilane and the like. Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like. .

As the titanate coupling agent, for example, isopropyl triisostearoyl titanate,
Examples thereof include isopropyl tridodecylbenzenesulfonyl titanate and isopropertris (dioctyl pyrophosphate) titanate.

As the surfactant, a commercially available product can be used as it is.

In the present invention, examples of the binder resin used for the metal oxide-dispersed resin core include all resins obtained by polymerizing vinyl monomers. Examples of the vinyl monomer here include styrene, 0
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene,
2,4-dimethylstyrene, pn-butylstyrene,
p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-di Chlorostyrene,
styrene derivatives such as m-nitrile styrene, 0-nitrostyrene and p-nitrostyrene, and ethylene and unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride , Vinylidene chloride,
Vinyl halides such as vinyl bromide and vinyl fluoride;
Vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate Α-methylene aliphatic monocarboxylic esters such as 2-ethylhexyl methacrylate and phenyl methacrylate; acrylic acid and methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, acryl Acrylic esters such as n-octyl acid, dodecyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; maleic acid, maleic acid half ester; vinyl methyl ether, vinyl ethyl ether Vinyl ethers such as vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone Vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; acroleins; and those obtained by polymerizing one or two or more of these.

In addition to a resin obtained by polymerization from a vinyl monomer, a mixture of a polyester resin, an epoxy resin, a phenol resin, a urea resin, a polyurethane resin, a polyimide resin, and a cellulose resin can be used.

In the present invention, the metal oxide-dispersed resin core is produced by sufficiently stirring a vinyl-based or non-vinyl-based thermoplastic resin, a metal oxide, and other additives such as a curing agent by a mixer, and then heating the mixture. Roll, kneader, melt and knead using a kneader such as extruder, after cooling this,
Pulverization and classification can be performed to obtain a carrier core. At this time, it is preferable that the metal oxide-containing resin particles after classification are spherically formed by heat or mechanically and used as a spherical core.

In the present invention, as a method for producing a metal oxide-dispersed resin core (carrier core), there is a method of mixing and polymerizing the above resin and the above-mentioned metal oxide to obtain a core. As the monomers used for the polymerization, in addition to the above-mentioned vinyl monomers, vinylphenols and epichlorohydrin, which are starting materials for epoxy resins, phenols and aldehydes of phenolic resins, ureas and aldehydes of urea resins, melamine and aldehydes And the like are used. For example, as a method for producing a carrier core using a curable phenol resin, the metal oxide described above, preferably a metal oxide obtained by subjecting phenols and aldehydes to lipophilic treatment in an aqueous medium in the presence of a basic catalyst, And polymerized to obtain a core.

In such a method of manufacturing a carrier core,
Furthermore, the specific resistance of the carrier core can be further improved by putting phenols and aldehydes in the carrier core obtained in the presence of a basic catalyst in an aqueous medium, and further coating the surface with a phenolic resin. .
At this time, the surface of the carrier core can be made more robust by incorporating the metal oxide particles into the resin to be coated.

In the present invention, it is particularly preferable that the method for producing the carrier core includes a method for increasing the strength of the carrier core and for better coating the coating resin.
It is preferable to use the binder resin after crosslinking. For example, a method of adding a crosslinking component at the time of melt-kneading and crosslinking at the time of kneading, or selecting a curable resin at the time of direct polymerization and directly polymerizing to obtain a core, or a method of using a monomer containing a crosslinking component, etc. be able to.

In the present invention, as the coating resin that can be used for the resin magnetic carrier, an insulating resin can be suitably used. The insulating resin may be a thermoplastic resin or a thermosetting resin. Specifically, for example, as the thermoplastic resin, polystyrene,
Polymethyl methacrylate, styrene-acrylic acid copolymer, vinyl chloride, vinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, Cellulose, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose derivatives such as hydroxypropyl cellulose, novolak resin, low molecular weight polyethylene, saturated alkyl polyester resin,
Examples include aromatic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyarylate, polyamide resins, polyacetal resins, polycarbonate resins, polyether sulfone resins, polysulfone resins, polyphenylene sulfide resins, and polyether ketone resins.

As the curing agent for the thermosetting resin, specifically, for example, a phenol resin, a modified phenol resin, a maleic resin, an alkyd resin, an epoxy resin, an acrylic resin, specifically, for example, maleic anhydride, terephthalic acid-polyether Unsaturated polyester obtained by polycondensation of a polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, Polyimide, polyamide imide resin, polyether imide resin,
Polyurethane resins and the like can also be mentioned. These curing agents can be used alone or in combination of two or more. Further, a hardening agent or the like may be mixed with a thermoplastic resin and cured to be used.

In the present invention, a preferred method for producing a resin magnetic carrier (coated carrier) is to spray a coating resin solution onto the carrier core particles while floating the particles of the carrier core obtained as described above. Examples of the method include a method of forming a coat film on the surface of the particles and a spray drying method. This coating method is particularly applicable to the case where it is necessary to almost completely coat the coating resin on the relatively low-resistance carrier core as described above, or when coating the metal oxide-dispersed resin core using a thermoplastic resin. It is suitable for.

Since the resin magnetic carrier according to the present invention is manufactured as described above and the core is formed by a polymerization method, the resin magnetic carrier coated with the resin thereon is easily formed into a spherical shape.

In the present invention, the resin magnetic carrier has a shape factor SF-1 of 100 to 140 and an SF-2 of 100 to 140.
120 is preferred. This shape factor SF−
1, SF-2 is FE-SEM (S-8 manufactured by Hitachi, Ltd.)
00), the particle image of the resin magnetic carrier is randomly
00 pieces were sampled, and the image information was introduced into an image analyzer (Luzex3) manufactured by Nicole via an interface, analyzed, and defined as a value calculated from the following equation.

SF-1 = ｛(MXLNG) ² / ARE
A｝ × (π / 4) × 100 SF-2 = (PERI / AREA) × (1 / 4π) × 1
00 where AREA: magnetic carrier projected area, MXLN
G: Absolute maximum length, PERI: Perimeter Shape factor SF-1 indicates the degree of sphericity of the magnetic carrier,
It is necessary to have 100 or more, but if it is larger than 140, the shape gradually changes from spherical to irregular. SF-2 indicates the degree of unevenness on the surface of the magnetic carrier, and is required to be 100 or more. When it is larger than 120, the unevenness on the surface of the magnetic carrier becomes remarkable.

The resin magnetic carrier having the core formed by polymerization according to the present invention has a shape factor SF-1 of 100 to 140,
A good spherical shape with SF-2 of 100 to 120 can be easily obtained.

Conventionally, when an image is formed by the image forming apparatus of FIG. 1, the transfer of the magnetic carrier from the magnetic brush of the two-component developer in the developing units 1a to 1d to the photosensitive drums 3a to 3d and the transfer material in the transfer unit. Due to the adhesion of the magnetic carrier or the fall of the magnetic carrier leaked from the end of the developing sleeve of the developing devices 1a to 1d.
, And the transfer belt 130 made of a resin sheet may be scratched by contact with the photosensitive drums 3a to 3d or rubbing of the transfer belt with the cleaner 22.

According to the present invention, the resin magnetic carrier is formed in a spherical shape, has little friction with the conveyor belt 130, and has a soft surface made of resin.
Even if the transfer belt 30 is rubbed, the surface of the conveyor belt 130 is scarcely scratched.
It is possible to obtain a good quality color image.

In this embodiment, the resin magnetic carrier produced as described above was mixed with a non-magnetic toner, and the mixture was used in the developing units 1a to 1d shown in FIG. 2 for development to form an image. The transfer belt 130 as a transfer material transfer unit includes:
A sheet made of polyvinylidene fluoride having a thickness of 150 μm and a Rockwell hardness of R77 to 83 ° was used, and this was used for 11.7.
Rotated at a speed of cm / sec. The contact type transfer chargers 24a to 24d as transfer means are of a blade type, and the conductive blade is transferred to the back surface of the conveyor belt 130 opposite to the transfer material carrying side with a contact pressure of 10 gf / cm to transfer. Used for The contact pressure is preferably 10 to 15 gf / cm.

As a result, the abrasion of the conveyor belt 130 due to the magnetic carrier of the two-component developer is suppressed, and there is no back contamination or transfer failure of the image due to the belt cleaning failure.
A good quality color image could be obtained.

Embodiment 2 FIG. 2 is a schematic configuration diagram schematically showing another example of an image forming apparatus to which the present invention can be applied.

This image forming apparatus is provided with an intermediate transfer belt 30 as a second image carrier with respect to the photosensitive drums 3a, 3b, 3c and 3d as the first image carriers. 3d is arranged along the intermediate transfer belt 30.

Exposure lamps 111a to 111d, drum chargers 2a to 2d, developing devices 1a to 1d, primary transfer chargers 33a to 33d, and cleaners 4a to 4d are provided around the photosensitive drums 3a to 3d. A light source device (not shown) and the like are further installed above the device.

As the primary transfer chargers 33a to 33d, contact chargers using a charging member such as a blade, a roller, a brush, etc., which come into contact with the conveyor belt 130, are used. A charging roller was used. These charging rollers (primary charging rollers) 33a to 33d
Of the most upstream and the most downstream charging rollers 33a, 33
d also serves as a support roller for the intermediate transfer belt 30, and the intermediate transfer belt 30
d and the drive roller 34, and is driven to rotate.
The peripheral speed of the intermediate transfer belt 30 is the same as that of the photosensitive drums 3a to 3d.
Is the same as the peripheral speed.

The intermediate transfer belt 30 is made of a sheet of a dielectric resin such as a polycarbonate resin, a polyethylene terephthalate resin, a polyvinylidene fluoride resin, a polyurethane resin, a polyimide resin, a polyamide resin, and a polyether sulfone resin. Of which the volume resistivity is adjusted by dispersing a conductive filler of the formula (1) is widely used. These resin sheets are formed by joining both ends thereof to each other to form an endless shape, or a seamless (seamless) belt is used.

The formation of toner images on the photosensitive drums 3a to 3d is performed in the same manner as in the first embodiment. Photosensitive drums 3a to
The toner image of each color formed on 3d is
a to 34d, the charging roller 34
The images are superimposedly transferred onto the intermediate transfer belt 30 by the operations a to 34d (primary transfer), and a color image in which yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 30 is formed.

At the drive roller 34, a charging roller (secondary charging roller) 31 as a secondary transfer charger is disposed with the intermediate transfer belt 30 interposed therebetween, and a secondary transfer portion is formed. At the timing when the color image on the intermediate transfer belt 30 reaches the secondary transfer portion, the recording material P
Is supplied. The recording material P is sandwiched by the charging roller 31 and the driving roller 34 grounded together with the intermediate transfer belt 30, and when a voltage or a charge is supplied to the charging roller 31, the four-color toner on the intermediate transfer belt 30 is The images are collectively transferred onto the recording material P (secondary transfer).

The recording material P onto which the four color toner images have been transferred is conveyed to the fixing device 9 where the toner images are fixed, and then discharged outside the image forming apparatus.

Also in this embodiment, the same resin magnetic carrier as that of the first embodiment was used as the two-component developer used in the developing units 1a to 1d. In the case of the intermediate transfer system as in the present embodiment, the toner image is transferred onto the intermediate transfer belt 30 unlike the transport belt system as in the first embodiment.
If a scratch is generated on the surface of the belt 0, an image defect is directly caused, and thus the scratch on the belt is more fatal than in the conveyor belt system. Further, the secondary transfer roller 31 is
Is in contact with the surface of the toner image carrying side, so that there is a high possibility that scratches will occur.

Accordingly, the advantage of using a resin magnetic carrier having a spherical shape and a resin surface and having a soft surface according to the present invention is great. Also in this embodiment, such a resin magnetic carrier is used as a magnetic carrier of a two-component developer. Thereby, the abrasion of the intermediate transfer belt 30 due to the magnetic carrier can be suppressed, and a good quality color image free of image failure and transfer failure due to cleaning failure of the belt 30 can be obtained.

In this embodiment, a resin magnetic carrier similar to that used in Embodiment 1 is mixed with a non-magnetic toner,
The image was formed by using the developing units 1a to 1d in FIG. 2 for development. The intermediate transfer belt 30 as an intermediate transfer member has a thickness of 150 μm and a Rockwell hardness of R77 to 83 °.
Use a sheet made of polyvinylidene fluoride
It turned at a speed of 1.7 cm / sec. The charging rollers 44a to 34d, which are contact-type primary transfer units, are provided with 10 gf / c on the back surface of the intermediate transfer belt 30 opposite to the toner image transfer side.
The contact roller is used for primary transfer by contacting with a contact pressure of 10 m (preferably 10 to 15 gf / cm). From the back side opposite to the transfer side, it was brought into contact with a contact pressure of 20 gf / cm and used for secondary transfer. The contact pressure is preferably 20 to 30 gf / cm.

As a result, it is possible to suppress abrasion of the intermediate transfer belt 30 due to the magnetic carrier of the two-component developer and obtain a good quality color image free from image contamination and transfer failure due to belt cleaning failure. Was.

In each of the above embodiments, an image forming apparatus for forming a four-color image has been described. However, the number of color images is not limited to this, and the present invention can be applied to a single-color image forming apparatus. can do.

[0078]

As described above, according to the present invention,
Since a resin magnetic carrier having a carrier core formed by a polymerization method or the like is used as the magnetic carrier of the two-component developer, it is possible to suppress the occurrence of abrasion on the transfer belt or the intermediate transfer belt due to the magnetic carrier, thereby resulting in poor belt cleaning. , And an image of good quality can be obtained without transfer surface failure and the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of an image forming apparatus to which the present invention can be applied.

FIG. 2 is a configuration diagram schematically illustrating another example of an image forming apparatus to which the present invention can be applied.

[Explanation of symbols]

 1a-1d Developing device 3a-3d Photosensitive drum 22 Belt cleaner 24a-24d Contact transfer charger 30 Intermediate transfer belt 31 Secondary charging roller 33a-33d Primary charging roller 34 Drive roller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 103 G03G 15/08 507L F-term (Reference) 2H005 AA21 BA03 BA11 BA15 CB03 CB04 CB07 CB13 FA01 FC03 2H030 AB02 AD01 BB02 BB42 2H031 AD03 BA09 CA09 FA01 2H032 AA05 AA15 BA05 BA09 BA18 DA03 2H077 AD02 AD06 AD36 EA01 GA13

Claims (12)

[Claims] An image carrier and an electrostatic latent image formed on the image carrier are developed using a two-component developer containing a non-magnetic toner and a magnetic carrier, and are visualized as a toner image. Means, a belt-shaped transfer material conveying means for supporting the transfer material and conveying the transfer material to a transfer unit facing the image carrier, rotating in contact with the image carrier, and the image carrier in the transfer unit An image forming apparatus comprising: a transfer unit configured to transfer the toner image onto the transfer material; wherein the magnetic carrier includes a binder resin and a core made of a magnetic metal oxide and a nonmagnetic metal oxide, and includes a polymerization method. Alternatively, the image forming apparatus is a resin magnetic carrier formed by a method not including the resin magnetic carrier. 2. The method according to claim 1, wherein the magnetic carrier is a resin magnetic carrier formed by a method including a polymerization method, and has a shape factor SF.
2. The image forming apparatus according to claim 1, wherein -1 is 100 to 140 and SF-2 is 100 to 120. 3. The image forming apparatus according to claim 1, wherein a plurality of said image carriers, developing means and transfer means are provided along a rotation direction of said transfer material conveying means. 4. The image according to claim 1, wherein the transfer unit is a contact type transfer unit that comes into contact with the transfer material transport unit from a back surface side opposite to a transfer material transport side. Forming equipment. 5. The image forming apparatus according to claim 4, wherein a contact pressure of said transfer means with said transfer material conveying means is 10 to 15 gf / cm. 6. An image carrier, wherein an electrostatic latent image formed on the image carrier comprises a non-magnetic toner and a magnetic carrier.
A developing unit that develops using a component developer to visualize as a toner image, a belt-shaped intermediate transfer body that rotates in contact with the image carrier, and the image carrier and the intermediate transfer body face each other. A primary transfer unit for transferring the toner image on the image carrier onto the intermediate transfer body at a primary transfer unit; and transferring the toner image on the intermediate transfer body at a secondary transfer unit facing the intermediate transfer body. An image forming apparatus provided with a secondary transfer unit for transferring to a material, wherein the magnetic carrier has a binder resin and a core made of a magnetic metal oxide and a non-magnetic metal oxide, and includes a method including or not including a polymerization method. An image forming apparatus, wherein the resin magnetic carrier is formed. 7. The magnetic carrier is a resin magnetic carrier formed by a method including a polymerization method, and has a shape factor SF.
7. The image forming apparatus according to claim 6, wherein -1 is 100 to 140 and SF-2 is 100 to 120. 8. The image forming apparatus according to claim 6, wherein a plurality of said image bearing members, developing means and primary transfer means are provided along a rotation direction of said intermediate transfer body. 9. The transfer device according to claim 6, wherein the primary transfer device is a contact-type transfer device that contacts the intermediate transfer member from the back surface side opposite to the toner image transfer side. Image forming apparatus. 10. The image forming apparatus according to claim 9, wherein a contact pressure of said primary transfer means with said intermediate transfer member is 10 to 15 gf / cm. 11. A contact-type transfer unit, wherein the secondary transfer unit is in contact with the intermediate transfer member via a transfer material from a back surface of the transfer material opposite to a toner image transfer side. The image forming apparatus according to any one of items 6 to 10. 12. The image forming apparatus according to claim 11, wherein a contact pressure of said secondary transfer means with said intermediate transfer member is 20 to 30 gf / cm.