JP2665230B2 - Electrophotographic copying method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic copying method for removing toner remaining on the surface of a photoreceptor by a magnetic brush cleaning method.

(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 be separated from the surface. In the drawings, reference numeral 9 denotes a separation 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 toner) and those using two-component type developer (composed of carrier and 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. However, there is an inconvenience that good cleaning over a long period cannot be guaranteed.

〔Purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic copying method capable of exhibiting a good cleaning effect even when used for a long time in a magnetic brush cleaning method.

〔Constitution〕

The present invention forms an electrostatic charge image on a photoreceptor, visualizes this with a charged toner such as a two-component developer, transfers the toner image to transfer paper, and removes the toner remaining on the photoreceptor surface. In the electrophotographic copying method in which the toner is removed by a magnetic brush cleaning unit, the toner concentration of a cleaning agent used for magnetic brush cleaning is 0.2 to 3.0 wt.
%, Preferably 1-2 wt%.

If there is no toner in the cleaning agent (toner concentration TC = 0
%) The fluidity of the cleaning agent in the developing unit is poor, and the cleaning agent cannot be supplied uniformly in the roller axis direction on the sleeve of the cleaning roller 71. In particular, when the carrier shape is an irregular type, the fluidity is extremely poor because the surface is uneven. TC0% is the saturation magnetization σ
Since s is large, the driving torque of the developing unit is increased, and as a result, the torque of the entire machine is increased, which is not preferable.

When toner is contained in the cleaning agent, the fluidity becomes good even with an irregular type carrier. This is considered that the toner plays the role of a lubricant. On the other hand, TC
Is 3% or more, it is difficult for the toner to transfer to the collection roller 74. In this case, the bias effect of the collection roller 74 cannot be sufficiently reduced. Therefore, when the bias is increased, not only the toner but also the carrier is transferred to the collection roller 74, the cleaning agent becomes insufficient, and the supply of the cleaning agent to the cleaning roller 71 becomes insufficient, and the cleaning failure gradually occurs.

In the following, 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. An electrostatic image subjected to image exposure by the optical system 3 is formed thereon, 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 (developed toner). The developer is held on a developing sleeve having a built-in magnet 411 and develops an electrostatic charge image on the photoconductor 1. Since only the developing toner is consumed each time the developing is performed, the sensor 42 detects the toner density of the developer and new developing toner is supplied so that the toner density always becomes constant. 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 of the present invention employs a magnetic brush cleaning method, in which a magnetic carrier (cleaning carrier) as a cleaning agent is stored. A positive or negative bias of about 100 to 500 V is applied to the cleaning roller 71 having a magnet (not shown) built therein, and a cleaning agent 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 a cleaning agent (cleaning carrier) and is transferred to the pumping rollers 72 to 73 together with the cleaning agent. 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, and only the residual toner is transferred to the collecting roller 74. The bias applied to the collection roller 74 is desirably relatively higher than the bias applied to the cleaning roller, and is suitably about 200 to 800 V.

Immediately after the residual toner is transferred from the pickup roller 73 to the collection roller 74, the cleaning agent (cleaning carrier) is scraped off by the cleaning scraper 75 in contact with the pickup roller 73, and is returned to the surface of the cleaning roller 71 again. On the other hand, the residual toner transferred to the collecting roller 74 is scraped off by a collecting blade 76 in contact with the collecting roller 74, taken out of the cleaning unit 7 by a discharge screw 77, and, if necessary, a two-component developer. Used as toner. The collecting roller 74 cleaned by the collecting blade 76 is used for collecting the next remaining toner. The cleaning agent (cleaning carrier) which falls on the cleaning roller 71 and is circulated again to contribute to the recovery of the residual toner has a function of maintaining the toner concentration at an appropriate value by entering the residual toner.

In the present invention, such a cycle of a series of copying and cleaning steps is repeated.
Is charged uniformly by the charger 2, there is no residual toner on the surface of the photoreceptor, and therefore, uniform charging of the photoreceptor 1 is guaranteed.

The TC of the cleaning agent used in the cleaning unit 7 is
It is 0.2-3.0 wt%. This facilitates the transfer of the residual toner to the cleaning agent (cleaning carrier) side and allows the toner to smoothly transfer to the collection roller 74. Therefore, the cleaning of the photoconductor 1 is favorably performed. Since the toner is smoothly removed by the collection roller 74, the toner concentration of the cleaning agent does not increase and is always constant. On the other hand, TC is 0.2wt%
In the following cases, the flow of the cleaning agent is not good, and the cleaning agent cannot be uniformly supplied in the roller axis direction on the sleeve of the cleaning roller 71. As a result, one cleaning failure occurs. When the TC becomes 3 wt% or more, it becomes difficult for the toner to transfer to the collection roller 74. At this time, if the bias of the collecting roller 74 is increased, not only the toner but also the carrier is transferred to the collecting roller 74, and the cleaning agent disappears from the cleaning portion, resulting in a cleaning failure.

FIG. 2 shows another embodiment of the present invention. The constitution of the cleaning agent of the present invention is as follows.

The residual toner on the photoreceptor 1 moves onto the biased cleaning roller 71 and then to the rear (biased) collection roller 74, where the toner on 74 is scraped off by the blade 76. Then, the toner moves to the discharge screw 77.

As the carrier core material, sand, cobalt, iron, copper, nickel having an average particle size of 20 to 1000 μm, preferably 50 to 500 μm,
Non-metals and metals such as zinc, aluminum, brass, glass,
Conventionally used materials such as metal alloys are widely used.
As the coating method, a resin may be dissolved in a solvent and applied to the surface of the core material by a conventionally known means such as a spraying method.

Next, as a release resin for coating, a polyolefin resin, for example, polyethylene, polypropylene,
Chlorinated polyethylene and chlorosulfonated polyethylene; polyvinyl and polyvinylidene-based resins such as polystyrene, acrylic resin (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, and polyvinyl ether And polyvinyl ketones; vinyl chloride-vinyl acetate copolymers; styrene-acrylic acid copolymers; silicone resins such as straight silicone resins comprising organosiloxane bonds, or modified products thereof (for example, alkyd resins, polyesters, epoxy resins, polyurethanes, etc.) A fluororesin, for example, polytetrafluoroethylene,
Polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyamide; polyester, for example, polyethylene terephthalate; polyurethane; polycarbonate; amino resin, for example, urea-formaldehyde resin; epoxy resin. Among them, acrylic resin, silicone resin, or a modified product thereof, and fluorine resin, particularly, silicone resin or a modified product thereof are preferable from the viewpoint of preventing the spent toner from adhering to the carrier. Commercially available silicone resin (straight silicone resin) includes KR271, KR255, KR251 manufactured by Shin-Etsu Chemical Co., Ltd., and SR24 manufactured by Tray Silicon.
And modified silicone resins such as KR206 (modified alkyd resin) and KR3093 manufactured by Shin-Etsu Chemical Co., Ltd.
(Modified acrylic resin), ES1001N (modified epoxy resin), Toray Silicon SR2115 (modified epoxy resin), SR2110 (modified alkyd resin), and the like. The thickness of the coating layer may be about 0.1 to 2.5 μ. If necessary, a pigment such as phthalocyanine, a quaternary ammonium salt, silica or a dye, a resin, or the like may be added as a conductive substance or a charge imparting material.

As the conductive carbon, any carbon black having conductivity can be used. For example, furnace black (as commercial products, Black Pearls2000 manufactured by Cabot Corporation, Ca
rbolacl; Lion Akzo Ketchen Black EC-DJ
500, Ketjen Black EC-DJ600, etc.), acetylene black (as commercial products, Denka Black granules and Denka Black powder manufactured by Denki Kagaku Kogyo Co., Ltd .; Postman An)
acarbon etc. ) And the like. Particle size is 0.5-500m
μ, preferably about 100 mμ, is appropriate.

On the other hand, examples of the white conductive agent include TiO ₂ , SnO ₂ , ZnO, and the like, and a mixture thereof. The particle size is suitably 0.01 to 3 μm, preferably about 0.05 to 2.0 μm.

Commercially available white conductive agents as described above include the following. All percentages are by weight.

Titanium Industry Co. Product: ECT52 (anatase-type titanium oxide TiO ₂ content 56~58%) KV400 (anatase-type titanium oxide TiO ₂ content 58~62%) ECR72 (TiO ₂ content from 80 to 85% rutile Titanium oxide) Ishihara Sangyo Co., Ltd. product: 500W (titanium oxide-tin oxide mixed system) 300W (titanium oxide-tin oxide mixed system) S-1 (titanium oxide) Mitsubishi Metals product: W-1 (titanium oxide-antimony oxide doped) Hakusui Chemicals' product: 23K (zinc oxide) Honjo Chemical's product: conductive zinc white No. 1 (zinc oxide content 99%) conductive zinc white No. 2 (zinc oxide content 99%) As a specific example of controlling the toner density, generally, a developer is flown while a coil is wound around a cylinder, a change in the frequency is captured, and toner is supplied when the frequency becomes lower than a preset frequency. The frequency is set in advance A control method to stop toner supply when the value becomes higher than the specified value, a control method to develop the reference pattern, determine whether the image density of the pattern is higher or lower than the reference, and turn OFF and ON the toner supply, or a developer A method in which the reflection density of the toner is compared with a reference value to turn on / off toner supply can be used.

FIG. 3 shows the cleaning unit 7 with a toner density sensor.
This is an example in which 42 is provided.

As shown in FIG. 3, a sensor 42 is provided to constantly control the toner density. More desirable toner concentration is 1-2%
Is good. When the toner concentration is 0.2% or less, the probability of contact between the carrier and the carrier in the cleaning agent increases. Particularly, when a coat layer is provided on the carrier core material, the film is scraped off very quickly, and the spent toner adheres to the carrier. As a result, the charging ability of the carrier is completely lost. Furthermore, the charging characteristics are hindered by the shaved material, and no charging is generated.

Each time the cleaning is performed as described above, toner is added to the cleaning unit 7 and the toner collection roller 74 is removed.
Causes the toner to be pulled off. At this time, the amount of toner to be added and the amount to be removed (balance) are not always constant. Therefore, as shown in FIG. 3, a cleaning agent is supplied to the frequency detecting sensor 42 to detect that the frequency is lower than the set value. Then, toner is supplied from a toner supply unit (not shown), and when the frequency becomes higher than the set frequency, the toner supply is stopped, so that the toner concentration of the cleaning unit 7 is always controlled to be constant and the toner concentration is reduced. Therefore, it is possible to prevent a problem caused by carrier shaving accompanying the above-mentioned problem, and to prevent the bias effect of the cleaning unit from being lost due to an increase in toner concentration.

Example 1 An average particle diameter of about 100 μm as a carrier for a two-component developer
m steel beads (Micro Shot SF manufactured by SHINTO BRATOR)
-100) was prepared.

On the other hand, 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 developer toner having a particle size of 5 to 20 μm.

Polystyrene (D-125 manufactured by Esso) 100 parts Metallic dye (Spilon Black BH manufactured by Hodogaya Chemical) 5 parts Carbon black (# 44 manufactured by Mitsubishi Kasei) 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 was coated according to the following formulation.

Silicone resin solution (KR250 manufactured by Shin-Etsu Chemical Co., Ltd.) A mixture of 150 parts of toluene and 1500 parts of toluene was dispersed with a homomixer for 30 minutes to prepare a coating layer forming solution, which was then formed into an amorphous iron powder having a particle size distribution of 46 to 76 μm ( A coating layer was formed on 5000 parts of a surface of TEFV 200/300) to a thickness of about 0.9 μm using a fluidized bed type coating apparatus to obtain a cleaning carrier.

To 1000 parts of these carriers, the toner amount was changed and mixed to prepare a starting cleaning agent. This agent is set in the cleaning unit shown in FIG.
A running test was carried out under the following conditions while controlling each toner concentration.

The copying machine shown in FIG. 3 (using a selenium-based photoreceptor,
The photosensitive member 1 is uniformly charged so that the surface potential thereof becomes +800 V, a bias of +250 V is applied to the cleaning roller 71, and a collecting roller.
74, a bias of +300 V was applied), and 30 copies per minute were obtained, and the toner consumed in the developing unit 4 was supplied. Table 1 shows the results of this running test.

Table 1 shows that good results can be obtained when the TC is 0.2 to 3.0 Wt%. On the other hand, when the TC is out of the above range, the cleaning property is poor and the image density is low.

Example 2 As a carrier for a two-component developer, the average particle diameter was about 100 μm.
m steel beads (Micro Shot SF manufactured by SHINTO BRATOR)
-100) was prepared.

On the other hand, 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 developer toner having a particle size of 5 to 20 μm.

Polystyrene (D-125 manufactured by Esso) 100 parts Metallic dye (Spilon Black BH manufactured by Hodogaya Chemical) 5 parts Carbon black (# 44 manufactured by Mitsubishi Kasei) 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 was coated according to the following formulation.

Silicone resin solution (KR250 manufactured by Shin-Etsu Chemical Co., Ltd.) 150 parts Ketchen Black EC DJ600 5 parts Toluene 1500 parts A mixture consisting of 1500 parts was dispersed with a homomixer for 30 minutes to prepare a coating layer forming liquid, and the particle size distribution was 46 to A coating layer was formed on a surface of 5000 parts of a 76 μm amorphous iron powder (TEFV 200/300) to a thickness of about 0.9 μm using a fluidized bed type coating apparatus to obtain a cleaning carrier.

When this carrier was evaluated in the same manner as in Example 1, the same results as in Table 1 were obtained.

Example 3 The carrier of Example 1 (steel beads having an average particle diameter of about 100 μm) was prepared as a carrier for a two-component developer. On the other hand, a mixture having the following formulation was kneaded under heating on two roll mills, cooled and then pulverized and classified to prepare a toner for a two-component developer having a particle size of 5 to 20 μm.

Polystyrene (D-125 manufactured by Esso) 100 parts Dye (Special Black SB manufactured by Orient Chemical) 5 parts Carbon black (Mitsubishi Kasei # 44) 100 parts 100 parts of these carriers and 3.0 parts of toner are mixed to form a two-component system. A developer was prepared. Q / M in this developer is 20
It was measured as μc / g.

On the other hand, the cleaning carrier was coated according to the following formulation.

Silicone resin solution (KR250 manufactured by Shin-Etsu Chemical Co., Ltd.) A mixture of 150 parts of toluene and 1500 parts of toluene was dispersed with a homomixer for 30 minutes to prepare a coating layer forming solution, which was then formed into an amorphous iron powder having a particle size distribution of 46 to 76 μm ( A coating layer was formed on 5000 parts of a surface of TEFV 200/300) to a thickness of about 0.9 μm using a fluidized bed type coating apparatus to obtain a cleaning carrier.

When a test similar to that of Example 1 was performed using this carrier, the same evaluation as that of Example 1 was obtained.

Example 4 The carrier of Example 1 (steel beads having an average particle diameter of about 100 μm) was prepared as a carrier for a two-component developer. On the other hand, a mixture having the following formulation was kneaded under heating on two roll mills, cooled and then pulverized and classified to prepare a toner for a two-component developer having a particle size of 5 to 20 μm.

Polystyrene (D-125 manufactured by Esso) 100 parts Metallic dye (Spilon Black BH manufactured by Hodogaya Chemical) 5 parts Carbon black (Mitsubishi Kasei # 44) 10 parts 100 parts of these carriers and 3.0 parts of toner are mixed. A two-component developer was prepared. Q / M in this developer is -24
It was measured as μc / g.

On the other hand, the cleaning carrier was coated as follows.

Silicone resin solution (KR250 manufactured by Shin-Etsu Chemical Co., Ltd.) 150 parts Ketchen Black EC DJ600 5 parts Toluene 1500 parts A mixture consisting of 1500 parts was dispersed with a homomixer for 30 minutes to prepare a coating layer forming liquid, and the particle size distribution was 46 to A coating layer was formed on a surface of 5000 parts of a 76 μm amorphous iron powder (TEFV 200/300) to a thickness of about 0.9 μm using a fluidized bed type coating apparatus to obtain a cleaning carrier.

When the same evaluation as in Example 1 was performed using this carrier, the same evaluation as in Example 1 was obtained.

〔effect〕

As is clear from the description of the embodiment, according to the copying method of the present invention, a high-quality copy can be obtained without image contamination even after copying 100,000 sheets. 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 used in the present invention, FIG. 2 is a modification of the cleaning unit 7 in FIG. 1, and FIG. 3 is an example in which a toner density sensor is provided in the cleaning unit. 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 Development sleeve 411 Magnet 42 Sensor 43 Paddle wheel 71 Cleaning roller 72, 73 Pumping roller 74 Collection roller 75 Cleaning scraper 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 Co., Ltd. (56) References JP-A-58-105275 (JP, A) JP-A-63-98685 (JP, A)

Claims (1)

(57) [Claims] An electrostatic charge image is formed on a photoreceptor, visualized with a charged toner, and the toner image is transferred to transfer paper. The toner remaining on the photoreceptor surface is removed by a magnetic brush cleaning unit. In the electrophotographic copying method to remove,
An electrophotographic copying method comprising controlling the toner concentration of a cleaning agent used for magnetic brush cleaning to be 0.2 to 3.0 wt%.