JP2869685B2 - 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 used in an electrophotographic apparatus, an electrostatic recording apparatus, an electrostatic printing apparatus, and the like.

[0002]

2. Description of the Related Art F. Since the invention of electrophotography by Carlson (U.S. Pat. No. 2,297,691),
Various two-component developers have been proposed (U.S. Pat. Nos. 2,618,551 and 2,618,52).
No. 2, No. 2,573,881 and No. 2,638,416) and after the invention of the magnetic brush developing method (U.S. Pat. No. 2,786,439). Attempts have been made to apply a resin coat to the carrier of a two-component developer to improve charging characteristics, toner scattering and moisture resistance.

A two-component developer is composed of a two-component system of a toner and a carrier. The carrier charges the toner and transports the toner to a developing zone. Only the toner adheres to the electrostatic latent image and is developed to form a visible image. Is formed. That is, the toner is a powder ink for forming an image, and the carrier has a function of imparting charge to the toner and a role of carrying the charged toner to the developing area.

Typical carrier (non-coated carrier)
Consists of magnetic particles such as iron, magnetite, and ferrite. Although this magnetic powder carrier has a simple structure and good durability, it has a relatively small electric resistance, so that the toner tends to be poorly charged, and the toner is liable to be scattered or fogged. Further, since the magnetic material is heavy and the surface of the magnetic material is active, the toner component adheres to the carrier due to the impact due to the stirring in the developing device, so that there is a problem that the spent is easily generated.

[0005] When the spent occurs, the charging ability of the carrier is reduced, which has an adverse effect on the image quality such as generation of fog and reduction in image density. For this reason, the life of the developer is shortened, and periodic replacement of the developer is inevitable.

On the other hand, a magnetic powder carrier (coated carrier) in which the surface of magnetic particles is coated with a resin or the like,
Since the resistance is increased, the chargeability of the toner is improved, and it is possible to prevent the toner from scattering in the apparatus and fogging. Spent can be prevented by selecting a resin having low activity. However, it is inevitable that the coating will be peeled off as it is used repeatedly, and in that case, scattering in the machine, fogging, and spent occur. In particular, in a small machine in which the developing unit is made compact, a large shearing force is applied during mixing and stirring with the toner, so that the coating is peeled off and the durability is likely to deteriorate.

[0007] A small-diameter magnetic resin carrier in which magnetic fine particles are dispersed in a binder resin is also known (Japanese Patent Laid-Open No. Sho 47/47).
Nos. 13954, 49-51950, 5
However, since the resistance is increased by the resin, the charging property to the toner is excellent. Further, since the resin carrier has a small specific gravity, the impact applied to the carrier during stirring and mixing is small, and toner spent is hardly generated.

In the two-component developing method, the life of the developing system is determined by the life of the carrier, and the magnetic resin carrier is preferable from the viewpoint of extending the life of the developing system.

However, on the other hand, since the specific gravity is low, the fluidity is poor and stirring and mixing are difficult, and the carrier and the toner tend not to be uniformly mixed with the toner by ordinary stirring but to be distributed in a sea-island manner. Since the toner is charged when it comes into contact with the carrier, if both are distributed in a sea-island manner, the toner cannot be charged sufficiently, causing image fog and contamination in the machine.

Further, since the magnetic resin carrier has poor magnetic responsiveness as compared with a normal ferrite resin carrier, a phenomenon in which the carrier is developed together with the toner on the surface of the photoreceptor at the time of development (hereinafter referred to as carrier pulling). There was a drawback that it was easy to wake up.

[0011] By combining a magnetic resin carrier obtained by dispersing magnetic fine powder in a binder resin, a magnetic powder carrier consisting of ferromagnetic particles, and an insulating toner into a developer, a soft developer is obtained. It has been reported that a magnetic brush of ears is formed and that aggregation of a magnetic powder carrier is prevented (Japanese Patent Laid-Open No. Sho 59-192262). However, there is no detailed description of the development conditions,
Further, since ordinary insulating toner is used as the toner, spent printing occurs and image deterioration due to continuous printing occurs.

On the other hand, in recent years, a photoconductor using an amorphous silicon (a-Si) photoconductor layer has been receiving attention in addition to the conventional Se photoconductor and organic optical semiconductor. The a-Si-based photoconductor has no problem in terms of safety as compared with the Se-based photoconductor,
Further, it has excellent durability and has a longer life than the device unit.

On the other hand, on the other hand, the a-Si-based photoreceptor tends to cause so-called "image deletion" due to long-term use of the ion product, paper powder, and the like, which easily adhere to the surface of the photoreceptor and leak electric charges. There is.

The use of abrasives as a measure against such image deletion has been known for a long time. For example, the addition of strontium titanate fine particles to a developer (Japanese Unexamined Patent Publication No.
No. 2,788,861), use of a cleaning member having a Mohs' hardness of 2.5 to 7.0 (Japanese Patent Application Laid-Open No. 59-88776), and a method of using abrasives and fine particles of the same level as the surface layer of an a-Si drum (particularly, US Pat. And the like, and it has been reported that alkaline earth metals, carbonates, and the like are effective for image flow of an a-Si photoreceptor (Japanese Patent Application Laid-Open No. SHO 61-61). 231564).

However, each of the above-mentioned polishing methods has a weak polishing force, and the effect of preventing the image flow of the a-Si photosensitive member is insufficient. In addition, if an attempt is made to increase the polishing force, the size of the image forming apparatus becomes large and cannot be adopted for a small machine.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method capable of improving the fluidity of a developer using a resin carrier, preventing carrier pulling, and forming a good image. Another object of the present invention is to provide an image forming method capable of preventing the occurrence of spent of a carrier and stably forming an image.

[0017]

According to the image forming method of the present invention, after uniformly charging a photosensitive member, the charged surface is exposed to light.
Forming an electrostatic latent image, and applying a DC voltage developing bias from a developing roller using a developer comprising a carrier and toner.
An image forming method for developing the photosensitive electrostatic latent image formed on the body while pressurizing, as the developer, a magnetic resin carrier obtained by dispersing (a) magnetic particles in a binder resin, (b) substantially a magnetic powder carrier having upper magnetic particles themselves, (c) abrasive particles containing the abrasive toner is fixed using a composite carrier type two-component developer on the surface, as the <br/> photoreceptor , using an a-Si based photosensitive member having an amorphous silicon (a-Si) photosensitive layer, the gap between the developing roller and the photosensitive member and 0.75～1.50Mm,
Wherein the developing roller, the gap between the regulating blade for regulating the layer thickness of the developer on the developing roller 0.50~1.25m
and m, the photosensitive member surface potential of the electrostatic latent image corresponding to the white background portion to be formed on the photosensitive member, wherein the 50~300V a potential difference between the developing bias potential, black portion formed on said photosensitive member The potential difference between the photoconductor surface potential of the electrostatic latent image corresponding to the above and the developing bias potential is 100 to 500V.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the image forming method of the present invention, a composite carrier comprising a combination of (a) a magnetic resin carrier and (b) a magnetic powder carrier is used.

(A) The magnetic resin carrier is obtained by dispersing magnetic fine particles in a binder resin. Positive or negative chargeable fine particles may be fixed on the surface of the carrier, or a surface coating layer may be provided. it can. (A)
The charging characteristics such as the polarity of the magnetic resin carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer.

Examples of the binder resin used for the magnetic resin carrier include vinyl resins represented by polystyrene resins, thermoplastic resins such as polyester resins, nylon resins and polyolefin resins, and curable resins such as phenol resins. Is exemplified.

Examples of the magnetic fine particles include magnetite, spinel ferrite such as gamma iron oxide, and metals other than iron (M
n, Ni, Mg, Cu, etc.), and magnetoplumbite-type ferrites such as spinel ferrite and barium ferrite, and iron and alloy particles having an oxide layer on the surface. The shape may be any of a granular shape, a spherical shape, and a needle shape. In particular, when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. In consideration of chemical stability, it is preferable to use ferromagnetic fine particles of magnetite, spinel ferrite containing gamma iron oxide, and magnetoplumbite ferrite such as barium ferrite. By appropriately selecting the type and content of the ferromagnetic fine particles, a magnetic resin carrier having a desired magnetization can be obtained. The magnetic fine particles are suitably added to the magnetic resin carrier in an amount of 50 to 90% by weight.

Such a magnetic resin carrier can be manufactured, for example, by the following method. (1) The magnetic fine particles and the insulating binder resin are melted and mixed, and then cooled and finely pulverized.

(2) A melt spray drying method in which a molten mixture of magnetic fine particles and an insulating binder resin is sprayed. (3) A method in which a monomer or a prepolymer is reacted and cured in an aqueous medium in the presence of magnetic fine particles to produce a magnetic resin carrier in which magnetic fine particles are dispersed in a condensation type binder.

It is also possible to modify the surface by fixing positively or negatively chargeable fine particles or conductive fine particles to the surface of the obtained carrier particles, or to control the chargeability of the magnetic resin carrier by coating with a resin. it can.

As the surface coating material, silicone resin,
An acrylic resin, an epoxy resin, a fluorine-based resin, or the like is used. By coating these resins on the surface and curing the resin to form a coat layer, the charge-imparting ability can be improved.

The chargeable fine particles or the conductive fine particles are fixed to the surface of the magnetic resin carrier by, for example, uniformly mixing the magnetic resin carrier and the fine particles, attaching the fine particles to the surface of the magnetic resin carrier, and then mechanically mixing the fine particles. -It is performed by applying a thermal impact force and driving the fine particles into the magnetic resin carrier and fixing them. In this case, the fine particles are not completely embedded in the magnetic resin carrier, but are fixed so that a part thereof protrudes from the surface of the magnetic resin carrier. This fixing method is the same as the method of fixing the abrasive fine particles to the toner described later.

As the chargeable fine particles, organic and inorganic insulating materials are used. Specifically, as the organic material, it is possible to use organic insulating fine particles such as polystyrene, a styrene-based copolymer, an acrylic resin, various acrylic copolymers, nylon, polyethylene, polypropylene, a fluororesin, and a crosslinked product thereof. As for the charging level and polarity, a desired level of charging and polarity can be obtained depending on the material, polymerization catalyst, surface treatment and the like. Further, as the inorganic material, negatively chargeable inorganic fine particles such as silica and titanium dioxide, and positively chargeable inorganic fine particles such as alumina are used.

As the conductive fine particles, carbon black, tin oxide, conductive titanium oxide (a titanium oxide coated with a conductive material), silicon carbide and the like are used, and the conductivity is lost due to oxidation by oxygen in the air. Those that do not match are desirable. The average particle size of the magnetic resin carrier is 1
0-100 μm is suitable, preferably 20-80 μm
m, more preferably 30 to 70 μm.

(B) As the magnetic powder carrier, a magnetic powder such as iron, magnetite, or ferrite is used as in the case of the magnetic fine particles described above. In particular, the ferrite-based carrier has an extremely hard surface and is not polished by the abrasive toner itself. As the magnetic powder carrier, a non-coated carrier using the magnetic powder as it is is preferable from the viewpoint of durability stability, but a coated carrier obtained by coating the magnetic powder with a resin can also be used. The average particle size of the magnetic powder carrier is preferably 10 to 100 μm,
Preferably 20 to 80 μm, more preferably 30 to 7 μm
0 μm.

In the present invention, a magnetic resin carrier and a magnetic powder carrier are used in combination, but the functions are separated from each other.
That is, the magnetic resin carrier mainly performs a charge imparting (charging) action to the toner particles. Further, the magnetic powder carrier imparts fluidity to the developer, has a function of transporting and mixing the developer, and improves the magnetic responsiveness of the developer.

Since the magnetic resin carrier has both a lower specific gravity and an apparent specific gravity than the magnetic powder carrier, the magnetic resin carrier has a large surface area per unit weight, and has a large ability to impart charge to toner particles even in a small amount. Further, even in a developing device of a small printer in which a large shearing force is applied at the time of mixing and stirring, the generation of spent is reduced, and the impact during stirring of the magnetic powder carrier can be reduced. Further, even if the magnetic resin carrier has been subjected to surface treatment such as surface coating, since the stress at the time of stirring is relatively small, the surface coating material (surface treatment material) is hardly polished and peeled off by the abrasive toner. Therefore, in addition to controlling the surface state by adding a charge control agent to the resin carrier, a constant charge can be stably applied to the toner by performing a surface coating and a surface treatment.

On the other hand, by adding a magnetic powder carrier having a large specific gravity as a third component to a developer containing a magnetic resin carrier and a toner, the fluidity is improved. The true specific gravity of the magnetic resin carrier is preferably 2.0 to 3.5, while the true specific gravity of the magnetic powder carrier is preferably 4.5 to 8.0.

The magnetic powder carrier functions as a kind of auxiliary magnetic holding member in the developer, improves the magnetic responsiveness of the developer as a whole, holds the resin carrier, and prevents the carrier from being pulled out.

The mixing ratio between the magnetic resin carrier and the magnetic powder carrier is determined according to the charge level of the toner, the degree of carrier pulling, and the required fluidity of the developer. That is, when the charge level of the toner is low, the Q / M of the entire developer can be controlled by increasing the ratio of the magnetic resin carrier having the opposite charge to the toner. Also, by increasing the ratio of the magnetic powder having a large specific gravity, the fluidity of the developer is improved, and carrier pulling is prevented. The mixing ratio of the (a) magnetic resin carrier and the (b) magnetic powder carrier is preferably in a range of (a) / (b) = 5 to 75/95 to 25, more preferably 5 to 50/50 by weight ratio. 95 to 50.

FIG. 1 is a model diagram of the toner of the present invention.
Toner 11 has abrasive fine particles 1 on the surface of toner base particles 13.
5 are fixedly formed. The fixing of the abrasive particles 15 to the surface of the toner base particles 13 is performed, for example, by uniformly mixing the toner base particles 13 and the abrasive particles 15 and attaching the abrasive particles 15 to the surface of the toner base particles 13. This is performed by applying a mechanical / thermal impact force and fixing the abrasive fine particles 15 so as to be driven into the toner base particles 13. The abrasive fine particles 15 are not completely embedded in the toner base particles 13, but a part thereof is
3 so as to stick out.

Such a fixing device for the abrasive fine particles 15 is commercially available as a surface modifying device or system, and an example thereof is as follows. (1) Dry mechanochemical method: Mechanochemical (Okada Seiko Co., Ltd.) Mechanofusion system (Hosokawa Micron Co., Ltd.)

(2) High-speed airflow impact method: Hybridization system (Nara Machinery Co., Ltd.) Kryptron system (Kawasaki Heavy Industries, Ltd.) (3) Wet method: Dispercoat (Nissin Flour Milling Co., Ltd.) Coat Myser (Freund Sangyo Co., Ltd.)

(4) Heat treatment method: Surfusing (Nippon Pneumatic Industries, Ltd.) (5) Other: spray drying (Okawara Kakoki Co., Ltd.)

As the abrasive fine particles 15, fine particles having high hardness, for example, fine particles of a metal oxide such as alumina and zirconia are used. Also, as the surface protection layer 21, Si
Considering the application to an a-Si photoconductor provided with C,
Since the Mohs hardness of the C layer is about 8, the Mohs hardness is 8
As described above, preferably 8 to 9 fine particles are preferable.

The size of the abrasive particles 15 is preferably D / d = 10 to 50, more preferably 10 to 50, where D is the average particle size of the toner base particles 33 and d is the average particle size of the abrasive particles. It is in the range of 40. Thereby, the abrasive particles 15 are firmly fixed to the surface of the toner base particles 13,
Further, the polishing effect by the abrasive fine particles 15 increases.
The abrasive fine particles 15 may be subjected to a surface treatment for the purpose of charge adjustment and hydrophobicity. Further, for the purpose of adjusting the fluidity or the like, other fine particles may be used in combination.

As the toner base particles 13, those having the same constitution as the conventional toner itself are used, and for example, a binder resin, a colorant, a charge control agent, an offset preventing agent and the like can be blended. Further, a magnetic material may be added to obtain a magnetic toner. As the binder resin, a vinyl resin represented by a polystyrene resin such as a styrene-acryl copolymer, a polyester resin, or the like is used.

Examples of the colorant include various pigments and dyes including carbon black; examples of the charge control agent include quaternary ammonium compounds, nigrosine, nigrosine base, crystal violet, and triphenylmethane compounds; Olefin wax such as low molecular weight polypropylene, low molecular weight polyethylene or a modified product thereof can be used as an auxiliary agent; magnetite, ferrite and the like can be used as a magnetic substance.

The toner base particles of the present invention can be obtained by a conventional method, for example, by melt-kneading the components with a twin-screw extruder, a kneader, or the like, followed by pulverization with a jet mill or the like, and classification. Generally, the average particle size of the toner is preferably 20 μm or less, and more preferably 15 μm or less.

When such a toner 11 is used, the toner 11 polishes the surface of the magnetic powder carrier when stirring and mixing the developer, and removes the spent material fused to the powder carrier surface. Therefore, the spent does not deposit or grow more than a certain amount, and stable image quality can be obtained over a long period of time.

For the spent, the amount of spent for both carriers is determined from the resistance value and the total carbonaceous material. If the resin used in the resin carrier is insoluble in the solvent, see "Study of Magnetic Brush Developing Machine", Takafumi Arimura, Journal of the Society of Electrophotography, Vol. 9,
No. 2 (1981). Further, the measurement accuracy can be improved by quantifying a specific element in the carrier.

On the other hand, on the other hand, conventional organic photosensitive drums and photosensitive drums mainly made of selenium are damaged or polished when the abrasive toner of the present invention is used, resulting in poor durability. There's a problem. Therefore, in the present invention, by using an a-Si-based photoconductor drum having a high surface hardness as the photoconductor, good results were obtained as a system.
At the same time, the abrasive toner cleans the surface of the Si-based photosensitive layer without damaging the Si-based photosensitive layer.
A countermeasure against image deletion of the i-type photoconductor can also be realized.

FIG. 2 is a sectional view showing the layer structure of the photosensitive layer of the a-Si photosensitive member 21. On the conductive substrate 23,
Light absorbing layer 25 made of Si: Ge: H or the like, Si: H:
A carrier injection blocking layer 27 made of B: O or the like, a carrier excitation / transport layer 29 (photoconductive layer) made of Si: H or the like, and a surface protection layer 31 are sequentially laminated.

The surface protection layer 31 is typically formed of SiC. This SiC layer (surface protective layer 31) is not smooth, has many fine protrusions (cones), has strong hydrophilicity, and adheres ion products generated by corona discharge. Therefore, when continuous printing is repeated or printing is started under high humidity conditions, toner adheres to the photosensitive drum and toner filming occurs.
Adhesion of a hydrophilic compound such as ammonium nitrate as an ion product occurs, and the charge of the photoconductor leaks, so-called "image deletion" occurs. Moreover, these products have a strong tendency to accumulate between the minute projections of the SiC layer, which is the surface protective layer 31, so that "image deletion" cannot be prevented by ordinary cleaning.

On the other hand, the abrasive toner of the present invention is
The fine abrasive particles 15 polish the tip of the minute projections to smooth the surface of the photoreceptor, and at the same time, remove ion products deposited between the minute projections to prevent image flow. As a result, development stability is also ensured. Moreover, the toner of the present invention having such an effect can be used even when polished with a cleaning blade, a rubbing roller, or the like.
The surface of the a-Si photosensitive member is not greatly damaged.

Next, the image forming process of the present invention will be specifically described with reference to FIG. FIG. 3 is the same as the conventional general image forming apparatus except that a rubbing roller (pressing member) 47 is provided.

As a surface protective layer, S of about 0.3 to 1 μm
A corona charger 41, an LED head 43 (exposure device), a developing device 51, a transfer device 45, a rubbing roller 47, and a cleaning blade 49 are arranged around the drum-shaped a-Si photosensitive member 21 having the iC layer. Has been established. After uniform charging of the surface of the photoconductor 21 by the corona charger 41 and formation of an electrostatic latent image by selective image exposure by the LED head 43, the developer 91 is transferred to the photoconductor 2 by the developing roller 55 of the developing device 51.
1, and a visible image composed of the toner 11 is formed by development. At this time, the toner 1 in the developer 91
1, the surface of the photoconductor 21 is rubbed, and the surface Si
The C layer is polished. Further, since the abrasive fine particles 15 are firmly fixed to the toner base particles 13, they do not fall off and do not cause poor development, image defects or the like.

The developing device 51 mainly includes a developing tank 53,
Developing roller 5 for transporting developer 91 to the surface of photoconductor 21
5, a stirring member 57, and a doctor blade 59 (a regulating blade) for regulating the layer thickness of the developer 91.

In the present invention, by using a composite carrier system in which a resin carrier having a low specific gravity is mixed with a powder carrier having a high specific gravity, a composite material comprising a carrier and a toner can be obtained.
The fluidity of the component developer is improved, and the toner is evenly mixed,
In addition, the toner can be stably and uniformly charged to a predetermined value, and spent and prevented from being spent by mixing and stirring with the abrasive toner. Therefore, it is possible to form a good image without image fogging over a long period of time and to prevent toner from scattering in the apparatus.

FIG. 4 is an explanatory view showing the relationship between the drum-shaped photosensitive member 21 and the developing roller 55, and the developer is not shown. The developing roller 55 includes a magnet roller 61 inside a developing sleeve 63, and the developer is transported in the direction of arrow M by rotating the magnet roller 61 and / or the developing sleeve 63.

The thickness of the developer is regulated by the gap G ₁ (blade gap) between the surface of the doctor blade 59 and the surface of the developing roller 55, and is supplied to the surface of the photoreceptor 21. The photoconductor 21 and the developing roller 55 are opposed to each other while maintaining a gap G ₂ (developing gap) between the surfaces thereof.
The electrostatic latent image on the surface is developed. Development bias power supply 6
5, the developing bias voltage is applied to the developing roller 55 (developing sleeve 63), and the potential of the surface of the developing roller 55 (developing bias potential) and the potential of the electrostatic latent image formed on the surface of the photoconductor 21 are adjusted. The difference from the photoconductor surface potential acts as a driving force for transferring (developing) the toner to the photoconductor 21 surface.

According to the present invention, the blade gap G _{1 is set} to 0.
50 to 1.25 mm . Blade gap G ₁ is
If it is less than 0.50 mm, a stable developer layer cannot be formed. On the other hand, if it exceeds 1.25 mm , a good image cannot be obtained due to the relationship with the developing gap described below.

The developing gap G ₂ is set to 0.75 to 1.
50 mm. When the development gap G ₂ is less than 0.75 mm, not satisfactory image is obtained, whereas, 1.50 mm
If it exceeds, carrier pulling or the like occurs. Further, the difference between the photoconductor surface potential of the electrostatic latent image portion corresponding to the white background portion of the formed image and the developing bias potential is set to 50 to 300V. If the potential difference is less than 50 V, fogging tends to occur, while if it exceeds 300 V, carrier pulling tends to occur.

The difference between the photosensitive member surface potential and the developing bias potential of the electrostatic latent image portion corresponding to the black background portion of the formed image is 100 to 500 V, preferably 200 to 400 V. If this potential difference is less than 100 V, a good image cannot be obtained, while if it exceeds 500 V, carrier pulling occurs at the image edge.

Since the surface potential of the photoconductor in the electrostatic image portion is determined by the charging characteristics, charging conditions and exposure conditions of the photoconductor,
The above potential difference can be controlled by controlling the voltage applied by the developing bias power supply 65.

In the present invention, the gaps G ₁ , G
By defining ₂ and the potential difference, carrier pulling can be prevented and a good image can be developed. The toner 11 developed on the surface of the photoreceptor 21 is transferred to paper 93 (transfer material) by the transfer unit 45, and then fixed on the paper 93 by a fixing unit (not shown).

In the transfer step, not all the toner 11 on the surface of the photoreceptor 21 is transferred to the paper 93, but
Part of the toner 11 (residual toner) remains on the photoconductor 21. The remaining toner 11 is pressed against the surface of the photoreceptor 21 by the rubbing roller 47 to polish the SiC layer, and the polishing effect of the abrasive particles 15 of the toner 11 is increased.

Next, the remaining toner 11 on the photoreceptor 21 is
Is removed from the surface of the photoconductor 21 by the cleaning blade 49.
Due to the mechanical force applied between the photoconductor 9 and the photoconductor 21,
The surface SiC layer of the photoconductor 21 is polished by the abrasive fine particles 15 of the toner 11.

An elastic roller is used as the rubbing roller 47. The rubbing roller 47 is pressed against the surface of the photoreceptor 21, and is rotated so as to apply a shear stress to the photoreceptor 21. Is polished and cleaned. Further, by attaching a heater to the inner surface of the photoreceptor 21 and heating it, the effect of preventing image flow can be further improved.

[0064]

According to the present invention, a magnetic resin carrier and a magnetic powder carrier are used in combination, an abrasive toner is mixed with the carrier, a developer is used, an a-Si photosensitive member is used, and a blade gap is used. By defining the developing gap and the developing bias conditions, the developer is surely stirred and mixed, the necessary and sufficient charge amount is arbitrarily set, the toner is stably applied, and the carrier is prevented from being pulled. It can be developed. In addition, the generation of spent is prevented, and as a result, the occurrence of fogging and image defects is prevented, a good image can be formed for a long time, and the replacement of the developer is not required for a long time.

The process is excellent in that the developer is not deteriorated due to agitation and the durability stability is good, and a high-quality image can be stably obtained over a long period of time.

[0066]

【Example】

(1) Production of a resin carrier According to the method described in JP-A-2-220068, phenol and formalin are condensed in an aqueous medium in the presence of magnetite, and from 85% by weight of magnetite and 15% by weight of phenol resin. Core particles were obtained. The core particles were coated with 3% by weight of a silicone resin, and dried and cured to form a surface resin coat layer, thereby producing a magnetic resin carrier. This resin carrier had an average particle size of 60 μm and a specific gravity of 3.0.

(2) Production of Powder Carrier Using Fe ₂ O ₃ .CuO.ZnO ferrite, average particle diameter 60 μm, saturation magnetization 68 emu / g, resistance 10 ⁸ Ω · c
m of non-coated magnetic powder carriers were produced.

(3) Production of Abrasive Toner Styrene / n-butyl acrylate copolymer (copolymerization ratio 80/20) 90 parts by weight Carbon black (MA-100, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 5 parts by weight Polypropylene wax (Viscol 550P, Sanyo Chemical Industries, Ltd.) 3 parts by weight Charge control agent (Copy Blue PR, Hoechst) 2 parts by weight

The toner materials having the above mixing ratios were sufficiently kneaded by a high-speed mixer, pulverized and classified to obtain toner base particles having an average particle diameter of 10 μm. 5% by weight based on the toner base particles
Alumina (abrasive) fine particles (average particle size 0.4 μm) are added and mixed, and then treated with a surface modifying device (Hybritizer, manufactured by Nara Machinery Co., Ltd.) to fix the alumina fine particles on the surface. The obtained abrasive toner was obtained. The alumina fine particles have a Mohs hardness of 9 and a surface having abrasiveness. On the other hand, a comparative toner (toner without an abrasive) was produced without fixing the alumina fine particles and using the toner base particles as they were.

(4) Preparation of Developer The above carrier and toner are mixed at the following ratio,
The following developers were prepared. Example 1: Magnetic resin carrier 20 wt% + magnetic powder carrier 75 wt% + abrasive toner 5 wt% Comparative Example 1: magnetic resin carrier 20 wt% + magnetic powder carrier 75 wt% + abrasive-free toner 5 wt%

(5) Evaluation of Image Flow and Spent Using the developer of Example 1 and Comparative Example 1, 300,000 sheets were continuously printed using the apparatus shown in FIG. Then, the image flow was evaluated, and the thickness of the surface SiC layer after printing 300,000 sheets was measured by XPS. The results are shown in Table 1. Similarly, 3
The spent amount of the developer at the time of continuous printing of 100,000 sheets was calculated by measuring with a total carbon meter and is shown in FIG.

(I) Black spots ：: Black spots are not seen at all △: Black spots are seen a little ×: Many black spots

(Ii) Image flow ：: No image flow is generated Δ: Slight image flow is generated ×: Image flow is generated over the entire surface

[0074]

[Table 1]

As the photoreceptor, a light absorbing layer (Si: Ge: H, 0.2 to 5 μm) and a carrier injection blocking layer (Si: H: B: O, 0.2 to 4 μm) are formed on a conductive substrate. ), Carrier excitation / transport layer (Si: H, 15 to 30 μm), S
The thickness of the SiC surface protective layer was unified to 5,000 ° using an a-Si based photoreceptor in which an iC surface protective layer was sequentially laminated.
In both the initial stage and after printing 300,000 sheets, the surface of the a-Si photoreceptor is scanned using a scanning electron microscope (SEM) for 500 times.
Observation at 0 magnification revealed that after printing 300,000 sheets, the number of cones was reduced and the surface was smoothed.

The developing conditions were as follows. Blade gap: 1.2 mm Development gap: 1.2 mm Development bias potential: 320 V (potential difference between white background and development bias potential: 100 V) (Potential difference between black background and development bias potential: 300 V)

(6) Potential Difference Example 1 was carried out in the same manner as described above, except that the voltage applied by the developing bias power supply was controlled and the potential difference between the potentials of the white and black portions of the image and the developing bias potential was variously changed. The developer was used for continuous printing, and image evaluation and the presence or absence of carrier pull were observed. The results are shown in Table 2.

Image (fog) evaluation method ：: no fog is generated Δ: fog having no practical problem is generated x: fog is generated on the entire surface

Image density ：: sufficiently dark △: slightly lighter ×: lighter

Evaluation of carrier pulling ：: Carrier pulling does not occur △: Carrier pulling occurs at image edge portion ×: Carrier pulling occurs over the entire surface

Developing device torque ：: small Δ: slightly large ×: large

[0082]

[Table 2] Experiment No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Potential difference (V): White background 25 50 75 100 150 200 250 300 350 100 100 100 100 100 Black background 300 300 300 300 300 300 300 300 300 50 125 200 350 400 Image (fog) evaluation: Initial × △ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ After 200,000 sheets × △ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Image density: Initial ○ ○ ○ ○ ○ ○ ○ ○ ○ × △ △ ○ ○ After 200,000 sheets ○ ○ ○ ○ ○ ○ ○ ○ ○ × △ △ ○ ○ Carrier pull: Initial ○ ○ ○ ○ ○ ○ △ △ × ○ ○ ○ ○ ○ After 200,000 sheets ○ ○ ○ ○ ○ ○ △ △ × ○ ○ ○ ○ ○

(7) Regarding the gaps With respect to the blade gap G ₁ and the developing gap G ₂ , except that the gap width was variously changed by assembling adjustment, the experiment Nos. Each image was continuously printed under the same conditions as in Example 4, and the images and carrier pull were evaluated. The results are shown in Table 3.

[0084]

[Table 3] Experiment No. 15 16 17 18 19 20 21 22  Gap (mm): Blade gap 1.00 1.00 1.00 1.00 0.50 0.75 1.25 1.50Development gap 0.50 0.75 1.00 1.25 1.00 1.00 1.00 1.00 Image (fog) evaluation: Initial ○ ○ ○ ○ △ ○ ○ ○After 200,000 sheets ○ ○ ○ ○ △ ○ ○ ○  Image density: Initial ○ ○ ○ ○ △ ○ ○ ○After 200,000 sheets ○ ○ ○ ○ △ ○ ○ ○  Carrier pull: Initial ○ ○ ○ ○ △ ○ ○ ○After 200,000 sheets ○ ○ ○ ○ △ ○ ○ ○ Developer unit torque × △ ○ ○ ○ ○ △ ×

[Brief description of the drawings]

FIG. 1 is a model sectional view showing an embodiment of a toner according to the present invention.

FIG. 2 is an explanatory cross-sectional view illustrating an example of a layer configuration of an a-Si-based photoconductor.

FIG. 3 is an explanatory diagram illustrating an example of an image forming apparatus for carrying out the present invention.

FIG. 4 is an explanatory diagram illustrating a relationship between a photoconductor and a developing roller.

FIG. 5 is a graph showing the relationship between the number of prints and the amount of spent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Toner 13 Toner base particle 15 Fine abrasive particles 21 Photoreceptor 23 Conductive substrate 25 Light absorption layer 27 Carrier injection blocking layer 29 Carrier excitation / transport layer 31 Surface protection layer 41 Corona charger 43 LED head 45 Transfer device 47 Scraping roller 49 Cleaning Blade 51 Developing Device 53 Developing Tank 55 Developing Roller 57 Stirring Member 59 Doctor Blade 61 Magnet Roller 63 Developing Sleeve 65 Developing Bias Power Supply 91 Developer 93 Paper

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-131546 (JP, A) JP-A-2-79863 (JP, A) JP-A-64-61776 (JP, A) JP-A-63 225270 (JP, A) JP-A-63-170661 (JP, A) JP-A-60-229037 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08 G03G 9 /Ten

Claims (1)

(57) [Claims] An image forming method comprising: uniformly charging a photoreceptor;
The surface is exposed to form an electrostatic latent image, and a developing roller of DC voltage is applied from a developing roller using a developer including a carrier and a toner.
In an image forming method for developing an electrostatic latent image formed on the photoreceptor while applying bias, the developer comprises : (a) a magnetic resin carrier in which magnetic fine particles are dispersed in a binder resin; ) using a magnetic powder carrier consisting essentially magnetic particles themselves, the composite carrier type two-component developer containing the abrasive toner is fixed is abrasive particles in (c) surface, as the photoconductor, amorphous Silicon (a-Si)
Using a-Si based photosensitive member having a system photosensitive layer, the gap between the photosensitive member and the developing roller 0.75.
And 50 mm, the developing roller, the gap between the regulating blade for regulating the layer thickness of the developer on the developing roller 0.50~1.25m
and m, the photosensitive member surface potential of the electrostatic latent image corresponding to the white background portion to be formed on the photosensitive member, wherein the 50~300V a potential difference between the developing bias potential, black portion formed on said photosensitive member An image forming method, wherein a potential difference between a photoconductor surface potential of an electrostatic latent image corresponding to (c) and the developing bias potential is 100 to 500 V.