JPH0651621A - Image forming method - Google Patents

Abstract

PURPOSE:To surely stir and mix developer, to stably electrostatically charge toner, to perform developing in a state where carrier attraction is prevented, to prevent a faulty image from occurring, to form an excellent image over a long term and to eliminate the need of exchanging the developer for a long time. CONSTITUTION:Two-component developer containing magnetic resin carrier, magnetic powder carrier, and abrasive toner having surface to which abrasive material particulates are stuck and an a-Si photosensitive body 21 are used. The image is formed by an electrophotographic method by performing development supposing that a developing gap G2 is 0.25-2mm, a blade gap G1 is 0.25-2mm, a potential difference between a white part image potential and developing bias potential is 50-300V, and a potential difference between a black part image potential and the developing bias potential is 100-500V.

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 electrophotographic devices, electrostatic recording devices, electrostatic printing devices and the like.

[0002]

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

The two-component developer is composed of a two-component system of toner and carrier. The carrier charges the toner and conveys it to the developing zone, and 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 a charge to the toner and a role of carrying the charged toner to the developing area.

Typical carrier (non-coated carrier)
Is composed of magnetic particles such as iron, magnetite and ferrite. This magnetic powder carrier has a simple structure and good durability, but since the electric resistance is relatively small, toner charging failure is likely to occur, and toner scattering and fog are likely to occur. Further, since the weight is large and the surface of the magnetic material is active, there is a problem that the toner component tends to adhere to the carrier and generate a spent due to an impact due to stirring in the developing device.

When the spent occurs, the charging ability of the carrier is lowered, which causes adverse effects on the image quality such as fog and image density. Therefore, the life of the developer is shortened, and regular replacement of the developer is unavoidable.

On the other hand, a magnetic powder carrier (coated carrier) in which the surface of magnetic particles is coated with resin is
Since the resistance becomes high, the chargeability of the toner becomes good, and it is possible to prevent the toner from scattering in the machine and fogging. In addition, spent can be prevented by selecting a resin with low activity. However, it is unavoidable that the coating peels off with repeated use, and in that case, scattering in the machine, fog, and spent occur. In particular, in a small-sized machine having a compact developing unit, a large shearing force is applied at the time of mixing and stirring with the toner, so that the coating is easily peeled off and the durability is easily deteriorated.

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. 47-47).
No. 13954, No. 49-51950, No. 5
No. 0-2543), the resin has a high resistance, and therefore the property of imparting charge to the toner is excellent. Further, since the resin carrier has a small specific gravity, the impact on the carrier during stirring and mixing is small, and toner spent is less likely to occur.

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.

On the other hand, on the other hand, since the specific gravity is low, the fluidity is poor and stirring and mixing are difficult, and the carrier and toner tend to be distributed in a sea-island shape without being uniformly mixed with the toner by ordinary stirring. Since the toner is charged by coming into contact with the carrier, if both are distributed in a sea-island shape, the toner cannot be sufficiently charged, which causes image fog and contamination inside the machine.

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

By combining a magnetic resin carrier obtained by dispersing magnetic fine powder in a binder resin, a magnetic powder carrier made of ferromagnetic particles, and an insulating toner into a developer, a soft developer is obtained. It has been reported that the magnetic brush of the ears is formed and the aggregation of the magnetic powder carrier is prevented (JP-A-59-192262). However, there is no detailed description of development conditions,
Further, since the usual insulating toner is used as the toner, the continuous printing causes the generation of the spent and the image deterioration due to the spent.

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

On the other hand, on the other hand, the a-Si type photoconductor tends to cause so-called "image deletion" due to the long-term use of ion products, paper dust, etc., which tend to cause the leakage of electric charges. There is.

It has long been known to use an abrasive as a measure against such image deletion. For example, addition of strontium titanate fine particles to a developer (Japanese Patent Laid-Open No. 61-61).
No. 278861), using a cleaning member having a Mohs hardness of 2.5 to 7.0 (Japanese Patent Laid-Open No. 59-88776), and a method of using an abrasive and fine particles to the same extent as the a-Si drum surface layer (special JP-A-63-29759) and the like, and it has been reported that alkaline earth metals, carbonates and the like are effective for image deletion of an a-Si based photoreceptor (JP-A-61-61). No. 231564).

However, all of the above-mentioned polishing methods have a weak polishing power, and the effect of preventing image deletion of the a-Si type photoreceptor is insufficient. In addition, when the polishing power is increased, the image forming apparatus becomes large and cannot be used in a small machine.

[0016]

DISCLOSURE OF THE INVENTION The present invention provides an image forming method capable of improving the fluidity of a developer using a resin carrier and preventing the carrier from pulling, thereby enabling good image formation. The present invention also provides an image forming method capable of preventing the spent of carriers and stably forming an image.

[0017]

The image forming method of the present invention is an image forming method for developing an electrostatic latent image formed on a photoconductor using a developer comprising a carrier and a toner, , (A) a magnetic resin carrier in which magnetic fine particles are dispersed in a binder resin, and (b) a magnetic powder carrier substantially composed of magnetic particles themselves,
(C) An a-Si-based photoconductor having an amorphous silicon (a-Si) -based photosensitive layer as a photoconductor, using a composite carrier type two-component developer containing an abrasive toner having abrasive fine particles adhered to the surface thereof. Body, the gap between the photoconductor and the developing roller is set to 0.25 to 2 mm, and the developing roller is
The gap between the developing roller and the regulating blade that regulates the layer thickness of the developer is set to 0.25 to 2 mm, and the photosensitive member surface potential of the electrostatic latent image corresponding to the white background portion formed on the photosensitive member and the developing bias. The potential difference from the potential is set to 50 to 300 V, and the potential difference between the developing bias potential and the photoconductor surface potential of the electrostatic latent image corresponding to the black background portion formed on the photoconductor is set to 100 to 50 V.
It is characterized in that it is set to 0V.

[0018]

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

The magnetic resin carrier (a) is prepared by dispersing magnetic fine particles in a binder resin. Positive or negative chargeable fine particles may be fixed to the carrier surface, or a surface coating layer may be provided. it can. (A)
The charging characteristics such as 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.

The binder resin used in the magnetic resin carrier is a thermoplastic resin such as vinyl resin represented by polystyrene resin, polyester resin, nylon resin, polyolefin resin, or curable resin such as phenol resin. It is illustrated.

The magnetic fine particles include spinel ferrite such as magnetite and gamma iron oxide, and metals other than iron (M
(n, Ni, Mg, Cu, etc.), magnetoplumbite type ferrite such as spinel ferrite, barium ferrite, etc. containing one or more kinds thereof, and particles of iron or alloy having an oxide layer on the surface can be used. The shape may be granular, spherical, or acicular. Especially when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. Further, in consideration of chemical stability, it is preferable to use ferromagnetic particles of magnetoplumbite-type ferrite such as spinel ferrite or barium ferrite containing magnetite or gamma iron oxide. A magnetic resin carrier having a desired magnetization can be obtained by appropriately selecting the type and content of the ferromagnetic fine particles. It is suitable to add the magnetic fine particles 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 melt-mixed, then cooled and finely pulverized.

(2) A melt spray dry method in which a molten mixture of magnetic fine particles and an insulating binder resin is sprayed. (3) A method for producing a magnetic resin carrier in which magnetic fine particles are dispersed in a condensation type binder by reacting and curing a monomer or a prepolymer in an aqueous medium in the presence of magnetic fine particles.

Further, it is also possible to fix positively or negatively chargeable fine particles or conductive fine particles on the surface of the obtained carrier particles to modify the surface, or to coat the resin to control the chargeability of the magnetic resin carrier. 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 them to form a coating layer, the charge imparting ability can be improved.

To fix the charged fine particles or the conductive fine particles to the surface of the magnetic resin carrier, for example, the magnetic resin carrier and the fine particles are uniformly mixed, and the fine particles are adhered to the surface of the magnetic resin carrier, and then mechanically. -It is carried out by applying a thermal impact force and fixing the fine particles so that they are driven into the magnetic resin carrier. 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 fixing method of the abrasive fine particles to the toner described later.

As the chargeable fine particles, an organic or inorganic insulating material is used. Specifically, organic insulating particles such as polystyrene, styrene-based copolymers, acrylic resins, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesins and cross-linked products thereof can be used as the organic type. Regarding the charge level and polarity, a desired level of charge and polarity can be obtained depending on the material, polymerization catalyst, surface treatment, and the like. As the inorganic type, 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 (titanium oxide coated with a conductive material), silicon carbide, etc. are used, and the conductivity is lost by oxidation by oxygen in the air. What you don't touch is desirable. The average particle size of the magnetic resin carrier is 1
0 to 100 μm is preferable, and 20 to 80 μm is preferable.
m, and more preferably 30 to 70 μm.

As the magnetic powder carrier (b), magnetic powder of iron, magnetite, ferrite or the like is used as in the above-mentioned magnetic fine particles. In particular, the surface of the ferrite carrier is extremely hard, and the carrier itself is not polished by the abrasive toner. Further, as the magnetic powder carrier, a non-coated carrier which uses the magnetic powder as it is is preferable in terms of durability and 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
It is 0 μm.

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

The magnetic resin carrier has both a true specific gravity and an apparent specific gravity smaller than those of the magnetic powder carrier, and therefore has a large surface area per unit weight and has a large charge imparting ability to toner particles even in a small amount. Further, even in a developing device of a small-sized printer which is subjected to a large shearing force during mixing and stirring, the occurrence of spent is small, and the impact during stirring of the magnetic powder carrier can be mitigated. Further, even if the magnetic resin carrier is subjected to surface treatment such as surface coating, the stress at the time of stirring is relatively small, and therefore the surface coating material (surface treated material) is hard to be abraded and peeled 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 not only by performing surface coating and surface treatment.

On the other hand, the fluidity is improved by adding a magnetic powder carrier having a large specific gravity as the third component to the developer containing the magnetic resin carrier and the toner. 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 pulling.

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

FIG. 1 is a model diagram of the toner of the present invention.
Toner 11 has abrasive mother particles 1 on the surface of toner mother particles 13.
5 is fixed and formed. To adhere the abrasive fine particles 15 to the surface of the toner mother particles 13, for example, after uniformly mixing the toner mother particles 13 and the abrasive fine particles 15, and adhering the abrasive fine particles 15 to the surface of the toner mother particles 13, It is carried out by applying mechanical and thermal impact force to fix the abrasive fine particles 15 into the toner mother particles 13 so as to be fixed therein. The abrasive fine particles 15 are not completely embedded in the toner base particles 13, but a part thereof is not embedded in the toner base particles 1.
It is fixed so that it projects from 3.

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 air impact method: Hybridization system (Nara Machinery Co., Ltd.) Cryptron system (Kawasaki Heavy Industries, Ltd.) (3) Wet method: Dispercoat (Nisshin Flour Milling Co., Ltd.) Coat Mizer (Freund Industry Co., Ltd.)

(4) Heat treatment method: surfing (Nippon Pneumatic Mfg. Co., Ltd.) (5) Others: Spray dry (Okawara Kakoki Co., Ltd.)

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

The size of the abrasive fine particles 15 is preferably D / d = 10 to 50, more preferably 10 where D is the average particle diameter of the toner mother particles 33 and d is the average particle diameter of the abrasive fine particles. The range is 40. As a result, the abrasive fine particles 15 are firmly fixed to the surface of the toner mother particles 13,
Further, the polishing effect of the abrasive fine particles 15 is increased.
The surface of the abrasive fine particles 15 may be subjected to a surface treatment for the purpose of charge adjustment and hydrophobization. Further, other fine particles may be used together for the purpose of adjusting fluidity and the like.

As the toner mother particles 13, those having the same constitution as that of the conventional toner itself are used, and for example, a binder resin, a colorant, a charge control agent, an offset preventive 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-based resin represented by polystyrene-based resin such as styrene-acrylic copolymer, a polyester-based resin, or the like is used.

Various pigments and dyes such as carbon black are used as colorants; quaternary ammonium compounds, nigrosine, nigrosine bases, crystal violet, triphenylmethane compounds and the like are used as charge control agents; anti-offset agents and fixation-improving agents. An olefin wax such as low molecular weight polypropylene, low molecular weight polyethylene or a modified product thereof can be used as an auxiliary agent, and magnetite or ferrite can be used as a magnetic material.

The toner mother particles of the present invention can be obtained by a conventional method, for example, by melt-kneading the respective components with a twin-screw extruder, a kneader or the like, pulverizing with a jet mill or the like, and classifying. Generally, the average particle diameter of the toner is preferably 20 μm or less, 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 the developer is stirred and mixed, and the spent matter fused on the surface of the powder carrier is removed by polishing. Therefore, a certain amount or more of the spent is not accumulated or grown, and stable image quality can be obtained for a long period of time.

As for the spent, the amount of spent for both carriers is quantified from the resistance value and the total carbonaceous matter. When the resin used in the resin carrier is insoluble in solvent, "Study of Magnetic Brush Developing Machine", Takafumi Arimura, The Electrophotographic Society of Japan, Volume 9,
It can also be measured by the method described in No. 2 (1981). Furthermore, the measurement accuracy can be improved by quantifying a specific element in the carrier.

On the other hand, on the other hand, in the case of the conventional organic photosensitive drum or the photosensitive drum mainly composed of selenium, when the abrasive toner of the present invention is used, it is scratched or abraded, resulting in poor durability. There's a problem. Therefore, in the present invention, a good result is obtained as a system by using an a-Si based photosensitive drum having a high surface hardness as a photosensitive member.
At the same time, the abrasive toner cleans the surface of the Si-based photosensitive layer without damaging the Si-based photosensitive layer.
It is also possible to implement measures against image deletion on the i-type photoconductor.

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,
The light absorption 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 protective layer 31 is typically made of SiC. This SiC layer (surface protection layer 31) is not smooth, has a large number of minute projections (cones), is highly hydrophilic, and has ion products generated by corona discharge attached thereto. 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 occurs as an ion product, the charge of the photoconductor leaks, and so-called "image deletion" occurs. In addition, these products have a strong tendency to accumulate between the minute protrusions of the SiC layer, which is the surface protection layer 31, and thus "image deletion" cannot be prevented by normal cleaning.

On the other hand, the abrasive toner of the present invention is
The fine abrasive particles 15 polish the tip of the fine protrusions to smooth the surface of the photoreceptor, and at the same time remove the ion products accumulated between the fine protrusions to prevent image deletion. As a result, development stability is also secured. Moreover, the toner of the present invention having such an effect can be obtained by polishing with a cleaning blade, a rubbing roller, or the like,
No major scratches on the surface of the a-Si photoconductor.

Next, the image forming process of the present invention will be specifically described with reference to 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 having a thickness of about 0.3 to 1 μm is used.
Around the drum-shaped a-Si photosensitive member 21 having the iC layer, 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. It is set up. After the surface of the photoconductor 21 is uniformly charged by the corona charger 41 and the electrostatic latent image is formed by the selective image exposure by the LED head 43, the developer 91 is applied to the photoconductor 2 by the developing roller 55 of the developing device 51.
The toner is supplied to the surface of No. 1 and developed to form a visible image of toner 11. At this time, the toner 1 in the developer 91
1, the surface of the photoconductor 21 is rubbed and the Si
The C layer is polished. Further, since the abrasive fine particles 15 are firmly fixed to the toner mother particles 13, they do not fall off and do not cause development defects, image defects or the like.

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

In the present invention, by using a composite carrier system in which a powder carrier having a large specific gravity is mixed with a resin carrier having a small specific gravity, a composite carrier system comprising a carrier and a toner is used.
The fluidity of the component developer is improved and the toner is mixed uniformly,
Further, the toner can be stably and uniformly charged up to a predetermined value, and the spent is prevented by mixing and stirring with the abrasive toner. Therefore, it is possible to form a good image without image fog over a long period of time and 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. When the magnet roller 61 and / or the developing sleeve 63 rotates, the developer is conveyed in the arrow M direction.

The layer thickness of the developer is regulated by the gap G ₁ (blade gap) between the doctor blade 59 and the surface of the developing roller 55, and the developer is supplied to the surface of the photoconductor 21. The photoconductor 21 and the developing roller 55 are opposed to each other with a gap G ₂ (development gap) between the surfaces thereof being maintained, and the photoconductor 21 is made to oppose by the developer around this facing portion.
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 electrostatic latent image portion formed on the surface of the photoconductor 21. The difference from the surface potential of the photoconductor acts as a driving force for transferring (developing) the toner to the surface of the photoconductor 21.

In the present invention, the blade gap G _{1 is set} to 0.
It is set to 25 to 2 mm, preferably 0.5 to 1.5 mm.
If the blade gap G ₁ is less than 0.25 mm, a stable developer layer cannot be formed. On the other hand, if it exceeds 2 mm, a good image cannot be obtained due to the relationship with the development gap shown below.

The developing gap G ₂ is 0.25 to ₂ m.
m, preferably 0.5 to 1.5 mm. If the development gap G ₂ is less than 0.25 mm, a good image cannot be obtained, while if it exceeds 2 mm, carrier pulling or the like occurs. Furthermore, the difference between the surface potential of the photosensitive member and the developing bias potential of the electrostatic latent image portion corresponding to the white background portion of the formed image is 5
It is set to 0 to 300V. If this potential difference is less than 50V, fog is likely to occur, while if it exceeds 300V, carrier pulling is likely to occur.

Further, the difference between the photosensitive member surface potential of the electrostatic latent image portion corresponding to the black background portion of the image to be formed and the developing bias potential 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 portion.

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

In the present invention, as described above, 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 photoconductor 21 is transferred to the paper 93 (transferred material) by the transfer device 45, and then fixed on the paper 93 by the fixing device (not shown).

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

Then, the residual toner 11 on the photoconductor 21
Are removed from the surface of the photoconductor 21 by the cleaning blade 49.
By the mechanical force applied between 9 and the photoconductor 21,
The surface SiC layer of the photoconductor 21 is polished by the fine abrasive particles 15 of the toner 11.

An elastic roller is used as the rubbing roller 47, and the rubbing roller 47 is brought into pressure contact with the surface of the photoconductor 21 and rotated so as to apply a displacement stress to the photoconductor 21. The surface is polished and cleaned. Further, by attaching a heater to the inner surface of the photoconductor 21 to heat it, the effect of preventing image deletion can be further improved.

[0064]

According to the present invention, a magnetic resin carrier and a magnetic powder carrier are used in combination, and an abrasive toner is mixed into the carrier to form a developer, an a-Si type photoreceptor is used, and a blade gap is used. By developing, developing gap and developing bias conditions, the developer can be surely agitated and mixed, and the necessary and sufficient amount of charge can be arbitrarily set to stably impart the toner to the toner and prevent carrier pulling. Can be developed. In addition, the generation of spent is prevented, and as a result, fogging and image defects are prevented from occurring, good image formation can be performed for a long period of time, and replacement of the developer is not required for a long period of time.

Further, it is excellent in the process such that the developer is less deteriorated by stirring and the durability stability is good, and a high quality image can be stably obtained for a long period of time.

[0066]

【Example】

(1) Production of 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 to prepare 85 wt% of magnetite and 15 wt% of phenol resin. Core particles were obtained. The core particles were coated with 3% by weight of a silicone resin, dried and cured to form a surface resin coat layer, and a magnetic resin carrier was manufactured. 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 type ferrite, average particle size 60 μm, saturation magnetization 68 emu / g, resistance 10 ⁸ Ω · c
m non-coated magnetic powder carrier was produced.

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

The toner material having the above mixing ratio was sufficiently kneaded by a high speed mixer, pulverized and classified to obtain toner mother 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 reformer (Hybridizer, Nara Machinery Co., Ltd.) to fix the fine alumina particles on the surface. The obtained abrasive toner was obtained. The alumina fine particles have a Mohs hardness of 9, and have a surface that is abrasive. On the other hand, a toner for comparison (toner without abrasive) was manufactured by fixing the alumina fine particles to the toner mother particles as they were.

(4) Preparation of developer The above carrier and toner are mixed in the following proportions,
The following developers were created. 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 deletion and spent Using the developers of Example 1 and Comparative Example 1, continuous printing of 300,000 sheets was performed using the apparatus shown in FIG. The image deletion was evaluated, and the film thickness of the surface SiC layer after printing 300,000 sheets was also measured by XPS. The results are shown in Table 1. Similarly, 3
The amount of spent of the developer after continuous printing of 0,000 sheets was measured by a total carbon measuring device and calculated, and is shown in FIG.

(I) Black spots ◯: No black spots are seen Δ: Some black spots are seen ×: Many black spots

(Ii) Image deletion ○: No image deletion occurs Δ: Image deletion occurs a little ×: Image deletion occurs on the entire surface

[0074]

[Table 1]

As the photoconductor, a light absorption layer (Si: Ge: H, 0.2 to 5 μm) and a carrier injection blocking layer (Si: H: B: O, 0.2 to 4 μm) were formed on a conductive substrate. ), Carrier excitation / transport layer (Si: H, 15 to 30 μm), S
The film thickness of the SiC surface protection layer was unified to 5000Å by using an a-Si-based photoreceptor in which the iC surface protection layer was sequentially laminated.
The surface of the a-Si-based photoconductor was subjected to 500 using a scanning electron microscope (SEM) both in the initial stage and after printing 300,000 sheets.
When observed at 0 times, the number of cones was reduced and the surface was smoothed after printing 300,000 sheets compared to the initial stage.

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 repeated in the same manner as described above except that the applied voltage from the developing bias power source was controlled to change the potential difference between the potentials of the white and black portions of the image and the developing bias potential. The developer was continuously printed, and the image evaluation and the presence or absence of carrier pulling were observed. The results are shown in Table 2.

Image (fogging) evaluation method ◯: Fogging does not occur at all Δ: Fogging that causes no practical problem occurs ×: Fogging occurs on the entire surface

Image density ○: Sufficiently dark △: Slightly light ×: Light

Evaluation of carrier pulling ◯: Carrier pulling does not occur Δ: Carrier pulling occurs at the image edge portion ×: Carrier pulling occurs on 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 area 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 ○ ○ ○ ○ ○ ○ ○ ○ ○ × △ △ ○ ○ Career pulling: Initial ○ ○ ○ ○ ○ ○ △ △ × × ○ ○ ○ ○ ○ After 200,000 sheets ○ ○ ○ ○ ○ ○ △ △ × ○ ○ ○ ○ ○

(7) Gap Regarding the blade gap G ₁ and the developing gap G ₂ , the experiment No. of Table 2 was changed except that the gap width was changed variously by the assembly adjustment. Each of them was continuously printed under the same conditions as in No. 4, and their images and carrier pulling were evaluated. The results are shown in Table 3.

[0084]

[Table 3] Experiment No. 15 16 17 18 19 20 21 22 23 Gap (mm): Blade Gap 1.00 1.00 1.00 1.00 1.00 0.50 0.75 1.25 1.50 Development gap 0.50 0.75 1.00 1.25 1.50 1.00 1.00 1.00 1.00 Image (fog) evaluation: Initial ○ ○ ○ ○ △ △ ○ ○ ○ After 200,000 sheets ○ ○ ○ ○ △ △ ○ ○ ○ Image density: Initial ○ ○ ○ ○ △ △ ○ ○ ○ After 200,000 sheets ○ ○ ○ ○ △ △ ○ ○ ○ Career pulling: Initial ○ ○ ○ ○ △ △ ○ ○ ○ After 200,000 sheets ○ ○ ○ ○ △ △ ○ ○ ○ Developing device torque × △ ○ ○ ○ ○ ○ △ ×

[Brief description of drawings]

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

FIG. 2 is an explanatory cross-sectional view showing an example of the layer structure of an a-Si based photosensitive member.

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

FIG. 4 is an explanatory diagram showing 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.

[Description of Reference Signs] 11 Toner 13 Toner Base Particles 15 Abrasive Fine Particles 21 Photoconductor 23 Conductive Substrate 25 Light Absorption Layer 27 Carrier Injection Blocking Layer 29 Carrier Excitation / Transport Layer 31 Surface Protecting Layer 41 Corona Charger 43 LED Head 45 Transfer Device 47 rubbing 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

Claims (1)

[Claims] 1. An image forming method for developing an electrostatic latent image formed on a photoconductor using a developer comprising a carrier and a toner, wherein (a) magnetic fine particles are contained in a binder resin as a developer. Composite carrier type two-component developer containing dispersed magnetic resin carrier, (b) magnetic powder carrier substantially composed of magnetic particles themselves, and (c) abrasive toner having abrasive fine particles adhered to the surface. As a photoconductor, an a-Si type photoconductor having an amorphous silicon (a-Si) type photoconductive layer is used, a gap between the photoconductor and the developing roller is set to 0.25 to 2 mm, and a developing roller and a developing roller are used. The gap between the upper developer and the regulating blade that regulates the layer thickness is set to 0.25 to 2 mm, and the photosensitive member surface potential of the electrostatic latent image corresponding to the white background portion formed on the photosensitive member and the developing bias. The potential difference between the positions 50-3
00 V, and the potential difference between the developing bias potential and the photosensitive member surface potential of the electrostatic latent image corresponding to the black background portion formed on the photosensitive member is 100 to
An image forming method, wherein the voltage is 500V.