JP2701909B2 - Electrophotographic copying machine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine (including an electrostatic copying machine), and more particularly, to a photoconductor (including an electrostatic recording body) after transferring a toner image onto plain paper or the like. The present invention relates to an electrophotographic copying machine in which a magnetic brush cleaning device is provided in a cleaning unit for removing residual toner on the surface.

(Prior art)

As shown in FIG. 1, the electrophotographic copying apparatus roughly includes an organic or inorganic photoreceptor 1 (which may be a belt-shaped member instead of a drum-shaped member) and a charger 2 and an optical system 3 around the photosensitive member. , A developing unit 4, a transfer charger 5, a separation charger 6, and a cleaning unit 7. The transfer charger 5 is used to transfer the toner image on the photoconductor 1 to transfer paper 8 such as plain paper, and the separation charger 6 transfers the transfer paper 8 having the toner image to the photoconductor 1.
It is provided to separate from the surface. In the drawing, reference numeral 9 denotes a separating claw.

Either a dry developing method or a wet developing method (including a semi-dry developing method) is used for visualizing an electrostatic charge image. The former is advantageous in that a copy is obtained in a dry state. Therefore, the dry development method is now mainstream.

Dry development systems are broadly classified into those using a one-component type developer (composed of only a toner) and those using a two-component type developer (composed of a carrier and a toner). In any case, it is desirable that all the toner images visualized by such a developer are ideally transferred to transfer paper. However, since toner that cannot be completely transferred remains on the photoreceptor, this toner is used. Residual toner must be removed with a cleaning device.

Methods for cleaning residual toner (untransferred toner) include (1) fur brush, (2) blade, and (3)
It is common to use a magnetic brush or the like. But
The fur brush method requires a large cleaning device,
There is a dislike that filming easily occurs on the photoconductor. In addition, the blade method has a defect that the photosensitive member is easily damaged. On the other hand, cleaning by a magnetic brush method has been studied in, for example, Japanese Patent Application Laid-Open No. 58-102273. However, although the defects of the above (1) and (2) are eliminated, a conventional magnetic brush cleaning apparatus is used. If copying is continued for a long time, filming tends to occur on the photoreceptor, especially in the cleaning carrier housed in the developing unit. As a result, the residual potential of the photoconductor (at the background)
, The background of the copy image becomes dirty, and the copy quality is significantly reduced. Further, since non-uniform filming tends to occur on the photoreceptor, the image tends to be uneven due to the filming. Further, since the filming material is not photoconductive, the image quality deteriorates as the filming proceeds. If such filming is uneven, the unevenness is particularly conspicuous particularly when a color image is copied.

〔Purpose〕

The present invention uses a two-component dry-type developer and includes a magnetic brush cleaning unit, which removes residual toner satisfactorily and, even if filming occurs on the photoreceptor, quickly removes it. It is another object of the present invention to provide an electrophotographic copying apparatus capable of stably obtaining a large number of high quality copies.

〔Constitution〕

The present invention forms an electrostatic charge image on a photoreceptor, visualizes it with a two-component developer, transfers this toner image to transfer paper, and then removes the toner remaining on the photoreceptor surface with a magnetic brush cleaning unit. The cleaning carrier housed in the magnetic brush cleaning section is provided with a coat layer in which abrasive particles are dispersed.

By the way, the present inventors provide a coating layer in which abrasive particles are dispersed on a cleaning carrier in a cleaning section when a two-component developer is used, so that the abrasive particles can improve the filming material on the surface of the photoreceptor. As a result, it was confirmed that long-term cleaning could be performed. In addition, it has been confirmed that there is an advantage that the coat layer is hardly scraped. The present invention has been made based on such a thing.

In the following, the device according to the invention will be explained in more detail in connection with the copying process with reference to the accompanying drawing (FIG. 1).

First, the surface of a photoconductor (inorganic photoconductor, organic photoconductor) 1 is uniformly charged positively or negatively by a charger 2. Positive charging or negative charging is selected depending on the type (property) of the photoreceptor 1. For example, if the photoreceptor is of a Se type, positive charging is performed. The image is exposed to the light by the optical system 3 to form an electrostatic image, and the electrostatic image is visualized by the developing unit 4.

The developing unit 4 contains a two-component developer composed of a carrier (magnetic carrier) and a toner. Developer is a magnet
The electrostatic image of the photoconductor 1 is developed by being held on a developing sleeve 41 having a built-in 411. Since only the developing toner is consumed each time the development is performed, the sensor 42 detects the toner density of the developer, and new developing toner is supplied so as to always have a constant oner density. Reference numeral 43 denotes a paddle wheel for stirring the developer. Note that a bias may be applied to the developing sleeve 41 as needed.

The visible image (toner image) is transferred to the transfer paper 8 by the transfer charger 5, and the transfer paper 8 is separated from the photoreceptor 1 by the separation charger 6 and the separation claw 9 and sent to the fixing process.

As mentioned above, all of the toner that forms a visible image on the photoconductor 1 at the time of transfer is not transferred to the transfer paper 8, and part of the toner remains on the photoconductor 1. The residual toner is removed by the cleaning unit 7.

The cleaning unit 7 in the apparatus of the present invention employs a magnetic brush cleaning method, in which a magnetic carrier provided with a coating layer in which abrasive particles are dispersed, that is, a cleaning carrier is accommodated. A positive or negative bias of about 100 to 500 V is applied to a cleaning roller 71 containing a magnet (not shown), and a cleaning carrier is held on the cleaning roller 71 by the magnet. Here, the polarity of the bias applied to the cleaning roller 71 is opposite to the polarity of the toner in the two-component developer.

The residual toner is electrostatically attracted to the cleaning carrier and is transferred to the pumping rollers 72 to 73 together with the cleaning carrier. A residual toner collecting roller 74 to which a bias having the same polarity as that of the cleaning roller 71 is applied is disposed behind the pumping roller 73.
, Only the residual toner is transferred. Preferably, the bias applied to the collection roller 74 is relatively higher than the bias applied to the cleaning roller, 200 to 800 V
Is appropriate.

Immediately after the residual toner is transferred from the pickup roller 73 to the collection roller 74, the cleaning carrier
The cleaning scraper 75 is scraped off by the cleaning scraper 75 and is returned to the surface of the cleaning roller 71 again. on the other hand,
The residual toner transferred to the collection roller 74 is scraped by a collection blade 76 in contact with the collection roller 74, taken out of the cleaning unit 7 by a discharge screw 77, and, if necessary, used as a two-component developer toner. used. The collecting roller 74 cleaned by the collecting blade 76 is used for collecting the next remaining toner. The cleaning carrier which falls on the cleaning roller 71 and is circulated again to contribute to the recovery of the residual toner must contain a small amount of the residual toner. % By weight.

In the apparatus of the present invention, such a cycle of a series of copying and cleaning steps is repeated, but when the photoconductor 1 is uniformly charged by the charging charger 2, residual toner is present on the surface of the photoconductor. Therefore, uniform charging of the photoconductor 1 is assured.

The type of abrasive used in the present invention is nitride,
Examples thereof include silicates, calcareous substances, carbides and oxides, which may be used alone or in combination of two or more. Specific abrasives are as follows.

Nitride: Silicon nitride.

Silicates: aluminum silicate, talc (magnesium silicate), mica, calcium silicate, etc.
Among them, aluminum silicate is preferable.

Calcareous substances: calcium carbonate, gypsum, etc.

Carbide: silicon carbide, aluminum carbide, tantalum carbide, titanium carbide, aluminum carbide, zirconium carbide and the like, among which silicon carbide and boron carbide are preferable.

Oxide: cerium oxide, chromium oxide, titanium oxide, aluminum oxide, etc., among which cerium oxide is preferable.

The particle size of these abrasives is 0.05mμ ~ 100μ, preferably 0.1m
About 50 μm is appropriate.

The amount of the abrasive particles added to the cleaning carrier coat layer is 0.5 to 50% by weight, preferably 1.0 to 30% by weight based on the solid content of the coating resin of the cleaning carrier.
It is. The thickness of the coating layer (cleaning carrier corso layer) is 0.3 to 2.5 µ, preferably 0.5 to 2.0 µ.

An example of the cleaning carrier of the present invention is as follows. That is, the cleaning carrier in the present invention is in a form in which the surface of a carrier core material is coated with a low surface energy substance in which, for example, abrasive particles are dispersed.
As the core material here, conventionally known iron, magnetite, ferrite and the like can be used. The particle size of the core material is suitably from 10 to 100 μm, preferably from about 30 to 500 μm.

Further, as the low surface energy substance covering the surface of the core material, a thermoplastic resin containing polyolefin such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polyvinyl and polyvinylidene such as polystyrene and polymethyl methacrylate; Polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral,
Polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer; silicone resin; fluorocarbon, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, poly Chlorotrifluoroethylene; polyamide resin; polyester (for example, polyethylene terephthalate); polyurethane; polycarbonate, amino resin (for example, urea-formaldehyde resin);
Particularly preferred are silicone resins and fluorine-based resins.

The silicone resin here may be any conventionally known silicone resin, such as straight silicone consisting only of an organosiloxane bond, and a silicone resin modified with alkyd, polyester, epoxy, urethane, or the like.

(Wherein R ¹ is a hydrogen atom, an alkyl group or phenyl group having 1 to 4 carbon atoms, R ² and R ³ are a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, Phenyl group, phenoxy group, alkenyl group having 2 to 4 carbon atoms, alkenyloxy group having 2 to 4 carbon atoms, hydroxyl group, carboxyl group, ethylene oxide group, glycidyl group or R ⁴ and R ⁵ are a hydroxyl group, a carboxyl group,
An alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a phenyl group, and a phenoxy group. k, l, 4m, n, o, and p represent an integer of 1 or more. Each of the above substituents may be unsubstituted, for example, amino group, hydroxyl group, carboxyl group, mercapto group,
It may have a substituent such as an alkyl group, a phenyl group, an ethylene oxide group, a glycidyl group and a halogen atom.

For example, straight silicone resins as commercially available products include KR271, KR255, KR251 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2406 manufactured by Toray Silicon Co., Ltd. Acrylic modified), ES1001N (epoxy modified), SR2115 (epoxy modified), SR2110 (alkyd modified) manufactured by Toray Silicon Co., Ltd.

The fluororesin used here is polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and tetrafluoroethylene. Examples include an ethylene-perfluoroalkyl vinyl ether copolymer (PFA),
In addition to these, those in which a filler is dispersed in a fluororesin can also be used.

Among the low surface energy materials, conductive materials (TiO ₂ , SnO ₂ ,
Carbon black), a triboelectric charge imparting substance (eg, a nigrosine dye, a compound having an amino group, a metal complex dye, a metal salt of salicylic acid, a metal salt of a salicylic acid derivative, etc.) may be added.

Although the description so far has been directed to an apparatus using an electrophotographic photosensitive member, it is a matter of course that an electrostatic recording member may be used instead of the photosensitive member.

Next, examples and comparative examples will be described. Parts here are by weight.

Example 1 An average particle diameter of about 100 μm as a carrier for a two-component developer
Steel beads (Micro Shot SF-
100) was prepared.

Further, a mixture having the following formulation was kneaded under heating on a two-roll mill, cooled, and then pulverized and classified to prepare a two-component developing toner having a particle size of 5 to 20 μm.

Polyethylene (D-125, manufactured by Esso) 100 parts Metal-containing dye (Spilon Black BH, manufactured by Hodogaya Chemical Co., Ltd.) 5 parts Carbon black (# 44 manufactured by Mitsubishi Kasei Co., Ltd.) 10 parts 100 parts of these carriers and 3.0 parts of toner are mixed. Thus, a two-component developer was prepared. The charge amount (Q / M) of the toner in this developer by a blow-off method was −24 μc / g.

On the other hand, the cleaning carrier is a toluene solution of silicone resin (20% solid content) (Toray Silicone SR2406) 100 parts Silicon nitride (SNE-10, manufactured by Ube Industries) 10 parts Ketjen Black EC / DJ500 (manufactured by Lion Akzo) A mixture composed of 5 parts of 1500 parts of toluene was dispersed with a homomixer for 30 minutes, and the resulting mixture was dispersed in an amorphous iron powder (TEFV200 / 300) 5000 having a particle size distribution of 46 to 76 μm.
A coating layer having a thickness of about 0.9 μm was formed on the surface of the portion using a fluidized bed type coating apparatus, and this was used as a cleaning carrier.

These two-component developer and cleaning carrier are the first
Copying device shown in the figure (a selenium-based photoreceptor is used for the photoreceptor, and the surface potential of photoreceptor 1 is uniformly charged so as to be +800 V, a bias of +250 V is applied to cleaning roller 71, and a recovery roller 74 is (A bias of +300 V was applied), and 30 copies per minute were obtained, and the toner consumed by the developing unit 4 was replenished. Table 1 shows the results of the running test.

Example 2 The carrier of Example 1 (steel beads having an average particle diameter of about 100 μ) was prepared as a two-component developing carrier.

Further, a mixture having the following formulation was kneaded under heating on two roll mills, cooled and then pulverized and classified to prepare a two-component developing toner having a particle size of 5 to 20 μm.

100 parts of polystyrene (D-125 manufactured by Esso) 5 parts of dye (Special Black SB manufactured by Orient Chemical Co.) 10 parts of carbon black (# 44 manufactured by Mitsubishi Kasei) 10 parts of these are mixed with 100 parts of carrier and 3.0 parts of toner to form two components. A system developer was prepared. Q / M in this developer is 20
It was measured as μc / g.

On the other hand, the cleaning carrier is made of polytetrafluoroethylene (solid content: 60%:-1, manufactured by Daikin Industries, Ltd.) 250 parts Silicon nitride (SNE-10, manufactured by Ube Industries) 20 parts Ketjen Black EC / DJ500 (Lion Akzo) 5 parts Coating solution consisting of 1500 parts of 1% aqueous solution of fluorine surfactant (FC-134, manufactured by Sumitomo 3M) is prepared and oxidized to an average particle diameter of 60μ in a rotating disk type fluidized bed particle coating device. Iron powder (TE
FV200 / 300) is poured into 5kg of fluid under heating at 80 ° C, and the coated product is taken out of the coating device and placed in a thermostat.
It was produced by heating at 2 ° C. for 2 hours to cure the fluorine film. The thickness of the coating layer is about 1.3μ.

The two-component developer and the cleaning carrier are uniformly charged so that the surface potential of the photoreceptor 1 becomes -600 V by using an organic photoreceptor and a cleaning roller as shown in FIG. (A bias of -250 V was applied to 71 and a bias of -300 V was applied to the collection roller 74). 30 copies were obtained per minute, and the toner consumed in the developing unit 4 was supplied. . Table 2 shows the results of the running test.

Example 3 36 kinds of cleaning carriers were prepared in exactly the same manner as in Examples 1 and 2, except that the abrasives used in Examples 1 and 2 were respectively changed as follows. When a similar running test was performed, the characteristics were almost the same as those of Examples 1 and 2.

(3-1) Silicon nitride having a particle size of about 1 μm (SNE-02 Ube Industries, Ltd.) (3-2) Silicon nitride having a particle size of about 0.4 μm (SNE-02 Ube Industries, Ltd.) (3-3) Particle size About 5μ of silicon calcium (PCM Lite-1
(3 Kawaii Lime Industries Co., Ltd.) (3-4) Clay containing 33% of particles having a particle size of about 5 μm or more and 48% of particles having a particle size of 2 μm or less (manufactured by Hardsil Tsuchiya Kaolin Co., Ltd.) 44μ talc (LSM-100 manufactured by Fujitalc Industries, Ltd.) (3-6) Calcium silicon calcium (PCM Lite
(3-7) Gypsum with a particle size of about 15μ (FT-2 manufactured by Nitto Gypsum Co.) (3-8) Calcium carbonate with a particle size of about 0.5μ (Tunex E Shiraishi Industry Co., Ltd.) ( 3-9) Calcium carbonate with a particle size of about 3μ (Tunex PC
(3-10) Gypsum with a particle size of about 10μ (D-200 manufactured by Nitto Gypsum Co.) (3-11) Silicon carbide β-type random with a particle size of about 0.3μ (manufactured by IBIDEN) (3- 12) Boron carbide having a particle size of about 5μ (3-13) Silicon nitride having a particle size of about 0.4μ (3-14) Tantalum carbide having a particle size of about 1.5μ (3-15) Aluminum oxide having a particle size of about 4-5μ (A31 manufactured by Nippon Light Metal Co., Ltd.) (3-16) Aluminum oxide with a particle size of about 0.02 to 1μ (Mechanox UB-10 Uemura Industries) (3-17) Aluminum oxide with a particle size of about 0.02μ (Aerosil Nippon) (3-18) Titanium oxide having a particle size of about 0.02 μm (manufactured by Nippon Aerosil Co., Ltd.) Example 4 Silicon carbide β-type random having a particle size of about 0.3 μm was further added to the coating liquid formulation of the cleaning carrier of Example 1 as abrasive particles. A cleaning carrier was prepared and carried out in exactly the same manner as in Example 1 except that 10 parts (manufactured by IBIDEN) were added. When a running test similar to that of Example 1 was performed, almost the same result as that of Example 1 was obtained.

Comparative Example A cleaning carrier was prepared in the same manner as in Example 1 or 2, except that the abrasive particles were not included in the coating liquid formulation of the cleaning carrier, and a running test similar to that in Examples 1 and 2 was performed. The density of the copy image was 1.28 at the start and 0.5 at the 500th sheet, and the surface potential on the photoconductor was 100 V at the start and 220 V at the 500th sheet.

〔effect〕

As is clear from the description of the examples, according to the imaging apparatus of the present invention, since the abrasive particles are contained in the cleaning carrier coat layer, the filming on the photoreceptor is scraped off, and the background portion is removed. Since the residual potential is not increased, a high quality copy can be obtained without image contamination even on 100,000 copies. Further, it was found that the surface of the photoreceptor after cleaning was very clean visually.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electrophotographic copying apparatus according to the present invention. FIG. 2 is a schematic view of another example of the cleaning unit slightly different from that shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Charger 3 ... Optical system 4, Developing part 5 ... Transfer charger, 6 ... Separation charger 7 ... Cleaning part, 8 ... Transfer paper 9 ... Separation nail, 41 Developing sleeve 41 Magnet 42 Sensor 43 Paddle wheel 71 Cleaning roller 72, 73 Pumping roller 74 Collection roller 75 Cleaning screw lever 76 Collection blade 77 …… Discharge screw

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroyuki Fushimi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Kayo Makita 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company, Ltd. (56) References JP-A-64-35561 (JP, A) JP-A-63-98685 (JP, A) JP-A-2-127686 (JP, A) JP-A-61-4070 ( JP, A)

Claims (1)

(57) [Claims] 1. An electrostatic charge image is formed on a photoreceptor, visualized with a two-component developer, and the toner image is transferred to transfer paper. An electrophotographic copying machine to be removed by a cleaning unit, wherein the cleaning carrier housed in the magnetic brush cleaning unit is provided with a coat layer in which abrasive particles are dispersed.