JP3088062B2 - Recycling development method using small diameter developing sleeve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recycle developing method used for an electrophotographic apparatus such as a copying machine or a printer. More specifically, the present invention relates to a photoreceptor having a white plate potential of 150 V or more and a small-diameter developing method. The present invention relates to a recycling developing method for developing an electrostatic image formed on a photoreceptor with a two-component magnetic developer using a sleeve.

[0002]

2. Description of the Related Art Generally, in image formation in electrophotography, the surface of a photoreceptor is charged (mainly charged), and then image exposure is performed to form an electrostatic image on the surface of the photoreceptor. Forming a visible toner image by developing with a developer, transferring the toner image to a predetermined sheet, and removing the toner image remaining on the photoreceptor after transfer by a cleaning blade or the like. , One cycle of the image forming process is completed. As the above-mentioned developer, for example, a two-component magnetic developer composed of a visible toner composed of a colored resin composition and a magnetic carrier is representative, and a developer transport sleeve provided in a developing device is used. The developer is conveyed to the developing area in the form of a magnetic brush, and the magnetic brush is rubbed against the electrostatic image on the photoreceptor to cause the toner to adhere to the electrostatic image, thereby performing the development.

Recently, in order to reduce the size and cost of copiers, a small-diameter developing sleeve or an inexpensive organic photoreceptor is used, and the toner removed and recovered by cleaning is circulated again in the developing device. Attention has been paid to a recycling developing method which is used again for development.

[0004]

However, for example, a single-layer type organic photoreceptor has a white plate potential of 150 V or more and a high residual potential, so that a large bias voltage must be applied during development. As a result, there is a problem that the carrier in the developer tends to be transferred to the surface of the photoreceptor, and the quality of the formed image is deteriorated. Also, when developing using a small diameter sleeve,
The rubbing time (development time) between the magnetic brush and the surface of the photoreceptor is inevitably shortened, the toner scraping effect of the magnetic brush is reduced, and fogging is likely to occur. In particular, in the case of performing recycle development, toner scattering is likely to occur due to deterioration of the physical properties of the recovered toner to be reused, and fogging becomes more remarkable.

Further, a toner density sensor is provided in the developing device filled with the two-component developer, and the toner density (T / D) of the developer composed of the toner and the carrier is provided.
Is controlled within a certain range. This toner density control utilizes the fact that the toner density in the developer also changes in accordance with the magnetic permeability of the developer, and the toner density sensor detects the magnetic permeability of the developer and outputs the output of the sensor. This is performed by replenishing toner into the developing device according to the value.

However, in the recycling developing method,
Since the recovered toner whose physical properties (for example, fluidity) has been reduced due to an external pressure such as cleaning is used again for development, an adverse effect is also recognized on the toner density control described above. For example, the curve A in FIG. 3 shows the relationship between the output of the density sensor (corresponding to the magnetic permeability of the developer) and the toner density (T / D) in the start developer.
The ON / OFF threshold value of the toner supply is set to the sensor output value 3
If it is set to V, the toner is replenished into the developing device when the toner concentration becomes 3.5% or less. However, when the collected toner is supplied into the developing device, the relationship between the output of the density sensor and the toner density changes as shown by a curve B, for example, due to the change in the physical properties of the developer. Therefore, it is difficult to maintain a constant toner density by setting the above-described threshold value.

Therefore, an object of the present invention is to make the white plate potential 15
Using a photoreceptor of 0V or more and a small-diameter developing sleeve,
To provide a method capable of solving all problems such as carrier pulling, fogging and toner scattering in a recycling developing method for developing an electrostatic image formed on a photoreceptor with a two-component magnetic developer. It is in. Another object of the present invention is to provide a recycling developing method which can stably perform development while keeping the toner concentration constant even when the collected toner is reused.

[0008]

According to the present invention, a photosensitive member having a white plate potential of 150 V or more and a small-diameter developing sleeve having a diameter of 35 mm or less are used. Developing the electrostatic image formed on the photoreceptor with a two-component magnetic developer composed of conductive toner particles to form a toner image, and transferring the toner image to the toner remaining on the photoreceptor Is collected by a cleaning means, and the collected toner and virgin toner for replenishment are supplied to a developing device in a recycling development method, wherein the two-component magnetic developer has an average particle diameter of 80 to 90 as a magnetic carrier.
There is provided a recycle developing method characterized by using one in the range of μm.

In the method of the present invention, the supply of the virgin toner for supply and the collected toner to the developing unit is turned on based on the output from the sensor for detecting the toner concentration in the developing unit.
The toner concentration of the developer is adjusted by performing the OFF control, and in particular, the threshold value of the sensor detection output for ON-OFF control of the supply of the toner into the developing device is changed according to the operation time of the image forming cycle. It is preferable to control the toner density.

[0010]

According to the present invention, the magnetic carrier in the developer has an average particle size of 80 to 90 μm, particularly 83 to 87 μm.
It is important to selectively use those in the range of m. By using a magnetic carrier with such a particle size, fogging and toner scattering can be effectively prevented and the occurrence of carrier pulling can also be effectively avoided. Was successful. In the present invention, it is not clear why the above-mentioned various problems can be solved by limiting the particle size of the magnetic carrier to the above range, but it is supposed that the density of the magnetic brush is moderately improved, and as a result, It is considered that the use of a small-diameter developing sleeve does not reduce the toner scraping effect of the magnetic brush even when the developing time is shortened, and also suppresses the separation of the carrier from the magnetic brush.

For example, when the particle size of the magnetic carrier is larger than the above range, the density of the magnetic brush becomes low, and the effect of scraping the magnetic brush becomes unsatisfactory. It becomes difficult to prevent scattering. If the particle size of the magnetic carrier is smaller than the above range, fogging and toner scattering can be effectively prevented, but when a large bias voltage is applied to the photoconductor and development is performed, carrier pulling occurs.

In the recycle developing method of the present invention, it is preferable to supply the virgin toner for replenishment and the collected toner collected from the cleaning device to the developing device in a state of being previously mixed. As a result, the properties of the developer in the developing device become uniform and stable, and there is almost no effect on the image due to mixing of the collected toner.

Further, in the recycling developing method of the present invention, the toner concentration of the developer in the developing device is detected by a sensor, and the virgin toner and the collected toner are supplied to the developing device based on the detected value. Can be effectively maintained. Especially ON of toner supply
By changing the sensor detection value serving as the threshold value of the OFF control in accordance with the operation time of the image forming cycle,
A constant toner density can be always maintained. Since the operation time of the image forming cycle corresponds to, for example, the operation time of the developing sleeve provided in the developing device, if the threshold is changed according to the integrated value of the driving time of the drive motor of the sleeve. Good.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Electrophotographic Apparatus) In FIG. 1 schematically showing an example of an electrophotographic apparatus for suitably implementing the recycling developing method of the present invention, a main charging device 2, an optical system 3, and a developing device are provided around a photosensitive drum 1. A transfer device 5 and a cleaning device 6 such as a cleaning blade are provided in this order, and a fixing device 7 is provided adjacent to the photosensitive drum 1.

That is, the photosensitive drum 1 is
The surface is charged, then image exposure is performed by the optical system 3, and an electrostatic image is formed on the photosensitive drum 1. This electrostatic image is developed by the developing device 4 to form a visualized toner image, and is transferred onto a predetermined sheet 8 by the transfer charging device 5. The sheet 8 having the transferred toner image is introduced into the fixing device 7 and the toner image is fixed by heat, pressure, or the like. On the other hand, the toner remaining on the photosensitive drum after the transfer is removed from the surface of the photosensitive drum 1 by the cleaning device 6 and collected. Thus, one step of the image forming cycle is completed.

(Developing Apparatus) The developing apparatus 4 includes a developing sleeve 10 having a magnet therein and a developing unit 11, and in the developing unit 11, a two-component system composed of a visible toner and a magnetic carrier is provided. Magnetic developer is filled. That is, the developer is conveyed by the sleeve 10 in the form of a magnetic brush, and the magnetic brush is rubbed against the surface of the photosensitive drum 1, and a charged toner adheres to the electrostatic image to form a toner image. is there.

FIG. 2 shows the structure of the developing device 4. FIG.
As can be understood from FIG. 2 and FIG. 2, the developing device 11 is divided into two chambers 4a and 4b by a partition wall 20,
Spirals 21 and 22 are provided in each room. The partition wall 20 has a toner density sensor 23
Is provided. Further, one of the chambers 4b communicates with a toner replenishing hopper 25 containing a spiral 24, and a toner tank 26 filled with replenishing virgin toner is disposed above the hopper 25. That is, the virgin toner in the toner tank 26 is supplied into the hopper 25 and is
Is supplied to the inside chamber 4b. The virgin toner replenished in the chamber 4b is supplied to the chamber 4b by the spirals 22 and 21.
And 4a reciprocate, and are mixed with the developer already existing in the developing device 11, and supplied to the sleeve 10 from the chamber 4a for development. Note that the sleeve 10 is driven and rotated by a motor 26, and the spiral 24 in the hopper 25 is rotated.
Is driven and rotated by a motor 27 that is driven independently and independently of the motor 26.
ON / OFF control is performed by the detection output of No. 3.

On the other hand, a collected toner storage tank 30 is provided in communication with the hopper 25, and the toner collected by the above-described cleaning device 6 is temporarily stored in the storage tank 30 by natural fall or suction. You. In the storage tank 30, a spiral 31 is provided at the bottom, a tip of the spiral 31 extends into the hopper 25, and a paddle 32 is provided at the tip, and the paddle 32 is
It is adjacent to the spiral 24. That is, the collected toner is
It is fed into the hopper 25 by the spiral 31 and the paddle 32, mixed and stirred with the virgin toner for replenishment by the spiral 24, replenished with the virgin toner into the developing device 11, and subjected to development. Usually, the spiral 31 and the paddle 32 can be driven integrally with the sleeve 10 by drive transmission means (for example, worm, gear, etc.) connected to the drive motor 26 of the sleeve 10.

(Magnetic Carrier) In the present invention, the magnetic carrier of the developer filled in the developing unit 11 of the developing device 4 has an average particle diameter of 80 to 90 μm, particularly 83 to 87 μm. Magnetic particles are selectively used. Suitable examples of such a magnetic material include ferromagnetic iron oxides such as triiron tetroxide (Fe ₃ O ₄ ) and iron sesquioxide (γ-Fe ₂ O ₃ ), and zinc iron oxide (ZnFe ₂ O ₄ ). , Iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium (Gd ₃ Fe ₅₎
O ₁₂ ), iron oxide copper (CuFe ₂ O ₄ ), iron oxide lead (Pb)
Fe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), neodymium iron oxide (NdFeO ₃ ), barium oxide (B
aFe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe
Ferrites such as ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ) and a composite thereof, iron powder (Fe), cobalt powder (Co), nickel powder (Ni), etc. Ferromagnetic metals or alloys, etc. can be exemplified. These can be used alone or in combination of two or more. Generally, triiron tetroxide and ferrite are particularly preferred. The mixing ratio between the magnetic carrier and the toner is generally in a weight ratio of 98: 2 to 90:10, particularly preferably in a weight ratio of 97: 3 to 92: 8.

(Toner) In the present invention, as the start toner and the replenishing virgin toner used in combination with the above magnetic carrier, the start toner in the start developer when recycling development by the developing device 4 is as follows. Known per se, a fixing resin is used in which toner particles in which a colorant pigment and, if necessary, a toner compounding agent such as a charge controlling agent and a release agent are dispersed are subjected to a surface treatment with a surface treating agent. You.

For example, as the fixing resin, a resin having a fixing property and an electric detecting property required for the toner, specifically, a styrene resin, a styrene-acrylic resin, a polyester resin, a polyurethane resin, a silicone resin, and a polyamide Resin, modified rosin and the like are used, and styrene-acrylic resin is preferably used.

The colorant pigment is usually a fixing resin medium 10
It is used in an amount of 2 to 20 parts by weight, especially 5 to 15 parts by weight, per 0 parts by weight, suitable examples of which are as follows. Black pigments Carbon black, acetylene black, run black, aniline black. Yellow pigment Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hanza yellow G, Hanza yellow 10G, benzidine yellow G,
Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigments Red mouth lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, induslen brilliant orange RK, benzidine orange G, induslen brilliant orange GK. Red pigment Bengala, cadmium red, lead red, cadmium mercury sulfide, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B. Purple pigment Manganese purple, fast violet B, methyl violet lake. Blue pigment Navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indaslen blue B
C. Green pigment chrome green, chromium oxide, pigment green B,
Malachite Green Lake, Fanal Yellow Green G. White pigment Zinc white, titanium oxide, antimony white, zinc sulfide. Extender barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white.

Examples of the charge controlling agent include oil-soluble dyes such as nigrosine base (CI. 50415), oil black (CI. 26150) and spiron black, metal-containing azo dyes, metal salts of naphthenic acid, and the like. Metal salts of alkylalicylic acid, fatty acid soaps, resin acid soaps and the like are used. The amount of the charge control agent is usually 0.1 to 10 parts by weight, especially 0.1 part by weight, per 100 parts by weight of the fixing resin.
It is 5 to 5 parts by weight.

When the toner image formed by development and transferred onto a predetermined sheet is fixed by heat fixing, a releasing agent is added to impart releasability at the time of heat fixing. As the release agent, usually, a polyrefin-based resin, particularly, polypropylene having a low molecular weight is suitably used. The amount of the release agent used is usually 0.1 to 6 parts by weight per 100 parts by weight of the fixing resin medium.

The toner particles in which the above-mentioned toner compounding agent is dispersed in a fixing resin can be produced by a method known per se such as a pulverization classification method, a melt granulation method, a spray granulation method, and a polymerization method. The pulverization classification method is common. For example, after each toner component is pre-mixed with a mixer such as a Henschel mixer, the mixture is kneaded using a kneading device such as a twin-screw extruder, and the kneaded composition is cooled, pulverized, classified, and classified into toner particles. I do. The toner particles generally have a median diameter of 5 to 15 μm, particularly 7 to 12 μm as measured by a Coulter counter.
m.

The above-mentioned toner particles are subjected to a surface treatment with a surface treatment agent. Examples of such a surface treatment agent include a fluidity improver and spacer particles. The fluidity improver improves the fluidity of the toner particles, prevents aggregation of the particles, and maintains a certain fluidity. As such a fluidity improver, for example, a particle size of 0.005 to
Resin powders such as 0.05 μm hydrophilic or hydrophobic fine silica powder and acrylic powder are known, and particularly, hydrophobic fumed silica surface-treated with organopolysiloxane, silazane or the like is preferably used. You. The amount of such a fluidity improver is preferably from 0.1 to 2.0% by weight per toner.

The spacer particles are usually used in combination with the above-mentioned flow improver, and are particles having a particle size of 0.05 to 1.0 μm, which is larger than the flow improver, and in particular, Used to improve transfer efficiency. By the external addition of the spacer particles, the coupling between the toner image and the latent image on the surface of the photoreceptor is weakened, so that the toner image can be easily peeled off, thereby improving the transfer efficiency in the toner image transfer step. Things. In particular, in the method of the present invention in which an organic photoreceptor is used, there is also an advantage that the external addition of spacer particles causes the surface of the photoreceptor to be worn during development, so that development can always be performed on a virgin surface.

As the spacer particles, any organic or inorganic inert particles having the above-mentioned particle size can be used. Generally, magnetic powder, alumina or the like is used. In particular, when magnetic powder is used as the spacer particles, there is an advantage that toner scattering can be effectively prevented. Such spacer particles are preferably externally added in an amount of 0.1 to 1.5% by weight per toner. In addition, as the above-mentioned magnetic powder, the above-mentioned magnetic material can be exemplified, and magnetite (iron sesquioxide) is preferable.

When the fluidity improver and the spacer particles are externally added to the toner for surface treatment, the fluidity improver and the spacer particles are previously mixed intimately under pulverization conditions, and this mixture is added to the toner. Good crushing is recommended.

The above-mentioned toner is mixed in advance with the magnetic carrier at the above-mentioned ratio, and is used as a start developer in the developing device 1.
1 and used as a supply virgin toner in the toner tank 26.

(Photoreceptor) In the present invention, as the photosensitive drum 1, a photosensitive drum having a potential of 150V or more when exposed to a white plate potential, that is, a photosensitive drum charged to a saturated potential is used. Such a photoreceptor is a very inexpensive organic photoreceptor, and is generally a monodispersed layer type organic photoreceptor.

The monodispersed layer type organic photoreceptor has a photosensitive layer formed by dispersing a charge generating material together with a charge transporting agent in a binder resin on a conductive substrate. Examples of the charge generation material include selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, anthanthrone pigments, phthalocyanine pigments,
Indigo pigments, sllen pigments, toluidine pigments, pyrazoline pigments, perylene pigments, quinacridone pigments and the like are used alone or in combination of two or more. These charge generating materials are dispersed in the photosensitive layer in an amount of 0.1 to 10.0% by weight, especially 0.5 to 2.0% by weight.

As the charge transporting material, a well-known hole transporting material or electron transporting material is used. Suitable hole transport materials include poly-N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5
-Diphenyl-1,3,4-oxadiazole, 2,5
-Bis (4-diethylaminophenyl) -1,3,4-
Oxadiazole, bis-diethylaminophenyl-
1,3,6-oxadiazole, 4,4′-bis (diethylamino) -2,2′-dimethyltriphenylmethane, 2,4,5-triaminophenylimidazole,
2,5-bis (4-diethylaminophenyl) -1,
Examples include 3,4-triazole, 1-phenyl-3- (4-diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazolin, p-diethylaminobenzaldehyde- (diphenylhydrazone), and the like. Examples of the electron transporting substance include 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone,
2,4,5,7-tetranitro-9-fluorenone, 2
-Nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, dinitroanthraquinone and the like. The charge transport material described above is used in the photosensitive layer in an amount of 10 to 4
It is dispersed in an amount of 0% by weight, especially 20-30% by weight.

Various binder resins, for example, styrene-based polymers, styrene-butadiene-based polymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic polymers, styrene-acrylic resins Copolymer, styrene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide resin, polyurethane resin, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, Examples thereof include a silicone resin, a ketone resin, a polyvinyl butyral resin, a polyether resin, and a phenol resin; and a photocurable resin such as an epoxy acrylate and a urethane acrylate.

The photosensitive layer is formed, for example, by dissolving or dispersing a predetermined amount of the binder resin, the charge generating material and the charge transport material in an appropriate organic solvent to prepare a coating solution. It is formed by applying the composition on a porous substrate and drying. The thickness of the photosensitive layer is generally in the range of 20 to 40 μm, particularly preferably in the range of 25 to 35 μm. As the conductive substrate, any conductive material such as an inorganic conductor such as aluminum, gold, silver, copper, nickel, tin oxide, indium oxide, and copper iodide; and an organic polymer such as polyacetylene and polyvirol is used. be able to.

In the present invention, the above-mentioned monodispersed layer type organic photoreceptor is used.
As long as it is as described above, a laminated organic photoreceptor in which a charge generation layer and a charge transport layer are formed on a conductive substrate in this order or in the reverse order can also be used.

In the present invention, it is preferable that the photosensitive drum 1 composed of the above-mentioned organic photosensitive member has a small diameter of usually 35 mm or less from the viewpoint of miniaturization of the apparatus.

(Developing Sleeve) In the developing device 4 described above, as the developing sleeve 10, a small-diameter one having a diameter of 25 mm or less is used from the viewpoint of miniaturization of the device. The developing sleeve 10 is formed of a non-magnetic material such as aluminum.
It has a magnet (not shown) inside, and carries the developer in the form of a magnetic brush by rotation of the sleeve or rotation of the magnet.

(Developing Method) In the development using the apparatus shown in FIGS. 1 and 2, the main charging and the image exposure are performed while rotating the photosensitive drum 1 so as to form the image on the photosensitive drum 1 as described briefly above. This is performed by forming an electrostatic image and rubbing the electrostatic image with the magnetic brush of the developer conveyed by the developing sleeve 10. In the present invention, since a photoconductor having a high residual potential is used as the photoconductor drum 1 during such development, it is necessary to apply a bias voltage to the photoconductor drum 1. Such a bias voltage is typically 2
It is preferably in the range of 50 to 350 V, particularly 280 to 320 V. That is, if the bias voltage is lower than the above range, it becomes difficult to form an image with high contrast, and if the bias voltage is higher than the above range, inconveniences such as carrier pulling and dielectric breakdown of the photosensitive layer cannot be avoided. .

The direction in which the magnetic brush is carried by the photosensitive drum 1 and the developing sleeve 10 may be a so-called forward direction (the same direction in the developing area) or a reverse direction. It is desirable that the direction is reversed in order to obtain a sufficient toner scraping effect. It is desirable that the moving speed of the magnetic brush (corresponding to the peripheral speed of the sleeve 10 in the case of the sleeve rotating system) and the peripheral speed of the drum 1 be in the range of 2.0 to 4.0. Further, the interval between the photosensitive drum 1 and the developing sleeve 10 is usually set to 0.
It is desirable to set it in the range of 55 to 0.85 mm. If it is smaller than this range, the scraping effect of the magnetic brush becomes unsatisfactory and fogging and toner scattering tend to occur. If it is larger than this range, carrier pulling tends to occur.

According to the present invention, the toner image formed on the photosensitive drum 1 by the above-described development is transferred to a predetermined sheet 8 by the transfer device 5, and the toner remaining on the photosensitive drum 1 after the transfer. Is collected by the cleaning device 6, supplied again into the developing device 11 together with the virgin toner, and recycled. This recycling development proceeds in the next step, as indicated by a change in the toner of the developer in the developing device 11. Development with start developer toner. Development with start developer toner + replenishing virgin toner + recovered toner. Development with virgin toner for replenishment + collected toner. Development with collected toner.

In the present invention, replenishment of the replenishing virgin toner and the collected toner is performed when the toner concentration of the developing device 11 becomes lower than a predetermined value. That is, when the density detection output value of the toner density sensor 23 reaches a preset threshold value, the motor 27 is driven for a certain period of time, and the spiral 24 in the hopper 25 operates. In this case, the collected toner collected by the cleaning device 6 is accommodated in the storage tank 30, and is sent into the hopper 25 by the spiral 31 and the paddle 32 driven simultaneously with the driving of the developing sleeve 10, that is, during the developing operation. Further, it is mixed and stirred with the virgin toner in the hopper 25. Therefore, by the operation of the spiral 24, the mixed toner of the virgin toner and the collected toner is supplied into the developing device 11.

As described above, the recovered toner is mixed with the virgin toner for replenishment in advance and replenished into the developing unit 11, thereby maintaining the uniformity of the developer and preventing a sudden decrease in the physical properties of the developer. It is very suitable for performing.

In the method of the present invention, the developing device 1 described above is used.
It is preferable to set and change the threshold value of ON-OFF of toner supply into the printer 1 according to a copying time, for example, an integrated value of a driving time of the motor 26 for driving the sleeve 10. That is, each time the integrated value of the drive time of the motor 26 reaches a certain time, the threshold value of ON-OFF is set. Thus, even when the collected toner whose physical properties have been reduced due to an external pressure such as cleaning is supplied into the developing device 11, the threshold value is changed and set in accordance therewith, thereby always maintaining a constant toner concentration. It is possible to make adjustments in this way.

[0045]

The present invention is further described in the following examples.

(Example 1) Preparation of toner particles : Each agent was melt-kneaded using a twin-screw extruder according to the following formulation, and the kneaded material was pulverized by a jet mill, classified by an air classifier, and averaged. Toner particles having a particle size of 10.0 μm were obtained. -Toner formulation-Fixing resin: 100 parts by weight Colorant: 10 parts by weight Charge control agent: 1 part by weight Release agent: 5 parts by weight

Preparation of Surface Treatment Agent : The following two surface treatment agents were prepared. Alumina pretreatment agent: Alumina having a center particle diameter of 0.5 μm (AKP-20, manufactured by Sumitomo Chemical Co., Ltd.) and hydrophobic silica powder of 0.015 μm (TS-720, manufactured by Cabot Corporation) were mixed at a ratio of 10: 1.
And mixed for 1 minute using Vitamix to obtain an alumina pretreatment agent. Magnetite pretreatment agent: magnetite having a saturation magnetization of 83 emu / g and a center particle diameter of 0.3 μm (manufactured by Titanium Industry: BR-
220) and the above-mentioned hydrophobic silica powder were mixed at a weight ratio of 10: 1 using Vitamix for 1 minute to obtain a magnetite pretreatment agent.

Preparation of start developer : To the toner particles prepared above, 0.25 of the above magnetite pretreatment agent was added.
% By weight and mixed with a Henschel mixer for 2 minutes to prepare a magnetite-treated toner. Next, 0.3% by weight of the hydrophobic silica powder used in the preparation of the surface treatment agent was added to the magnetite-treated toner, and mixed with a Henschel mixer for 2 minutes to prepare a toner for a start developer. The toner for the start developer has an average particle diameter of 80 μm.
m ferrite carrier (Powdertech: FL1
84-150) with a ball mill (75 rpm, 2
Time), a start developer having a toner concentration of 4.5% was prepared.

Preparation of virgin toner for replenishment : To the toner particles prepared above, 1.0 g of the above alumina pretreatment agent was added.
% By weight and mixed with a Henschel mixer for 2 minutes to prepare an alumina-treated toner. Next, 0.3% by weight of the hydrophobic silica powder used in the preparation of the surface treatment agent was added to the alumina-treated toner, and the mixture was added to the alumina-treated toner using a Henschel mixer.
The mixture was mixed for a minute to prepare a replenishing virgin toner toner.

Experimental Copier DC manufactured by Mita Kogyo using monodispersed layer type organic photoreceptor
-2556 was modified into a recycling machine shown in FIG. 1 and the following developing conditions were set. Organic photoreceptor; Photosensitive layer thickness: 30 μm White plate potential: 180 V Photoreceptor surface charging potential: 800 V Photoreceptor drum diameter: 30 mm Developing sleeve diameter: 20 mm Drum-sleeve distance: 0.70 mm Drum-sleeve peripheral speed ratio: 3.0 Bias Voltage: 300V

Under the above conditions, 30,000 copies were continuously made using the start developer prepared above and the virgin toner for replenishment, and fog, carrier pulling and toner scattering were evaluated. Table 1 shows the results. The control of the toner concentration was performed by changing the ON-OFF control threshold value of the toner supply according to the sensor output according to the flowchart shown in FIG. The evaluation of each test item was performed as follows.

Fog: The fog density was shown for the first image (initial), the 15,000th image and the 30,000th image. Carrier pull; evaluated by the presence or absence of white streaks in the image due to carrier transfer. ：: Carrier pull is not recognized at all. X: Carrier pull was recognized. Toner scattering: The degree of toner scattering in the machine after the end of the experiment and in the 30,000th sheet image was visually determined and indicated by the following criteria. ：: No toner scattering. Δ: Scattering of toner was slightly observed, but there was no effect on the image. ×: Toner scattering occurred to such an extent that toner was removed from the image.

(Example 2) An experiment was performed in exactly the same manner as in Example 1 except that a ferrite carrier having an average particle size of 90 µm was used as a carrier for the start developer. Table 1 shows the results.

(Comparative Example 1) An experiment was conducted in exactly the same manner as in Example 1 except that a ferrite carrier having an average particle size of 75 µm was used as a carrier for the start developer. Table 1 shows the results.

(Comparative Example 2) An experiment was performed in exactly the same manner as in Example 1 except that a ferrite carrier having an average particle size of 95 µm was used as a carrier for the start developer. Table 1 shows the results.

Comparative Example 3 An experiment was performed in exactly the same manner as in Example 1 except that a ferrite carrier having an average particle size of 105 μm was used as a carrier for the start developer.
Table 1 shows the results.

[0057]

[Table 1]

According to the present invention, by using a magnetic carrier having a mean particle diameter in the range of 80 to 90 μm as the magnetic carrier of the two-component magnetic developer, the white plate potential can be increased to 150V.
Even when a high bias voltage is applied to the photosensitive member having a high residual potential and development is performed, carrier pulling is effectively prevented, and even when a small-diameter developing sleeve having a diameter of 25 mm or less is used, magnetic The toner scraping effect of the brush is sufficiently exhibited, and fogging and toner scattering can be effectively prevented. ON-O for supplying toner into the developing device
By adjusting the sensor output threshold value of the FF control according to the image forming time, it is possible to always maintain a constant toner concentration even when the collected toner is used.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an electrophotographic apparatus for suitably implementing a recycling developing method of the present invention.

FIG. 2 is a diagram showing a main part of a developing device used in the apparatus of FIG.

FIG. 3 is a diagram showing a relationship between an output of a toner density sensor and a toner density.

FIG. 4 shows a toner supply ON-O in an experiment of an embodiment.
FIG. 7 is a diagram illustrating a change in a threshold value of an output of a toner density sensor that performs FF control.

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI G03G 15/08 507 G03G 21/00 326 21/10 15/08 507 (72) inventor Ryo Fujisawa, Chuo-ku, Osaka Tamatsukuri 1-chome, 2 No. 28 Mita Kogyo Co., Ltd. (56) References JP-A-7-261464 (JP, A) JP-A-6-308760 (JP, A) JP-A 5-241449 (JP, A) JP-A-1 -234859 (JP, A) JP-A-3-122665 (JP, A) JP-A-4-218080 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08- 15/09 G03G 15/06-15/06 101 G03G 9/10-9/113 G03G 21/10

Claims (6)

(57) [Claims] 1. A two-component system comprising a photosensitive member having a white plate potential of 150 V or more and a small-diameter developing sleeve having a diameter of 35 mm or less, and comprising a magnetic carrier filled in a developing device and visible toner particles. The electrostatic image formed on the photoconductor is developed with a magnetic developer to form a toner image, and the toner remaining on the photoconductor after the transfer of the toner image is collected by a cleaning unit. In a recycle developing method for replenishing toner and replenishing virgin toner into a developing device, a magnetic carrier of the two-component magnetic developer having an average particle diameter in a range of 80 to 90 μm is used. Recycling development method. 2. The recycling developing method according to claim 1, wherein the photoconductor is a single-layer organic photoconductor. 3. The recycling developing method according to claim 1, wherein the developing is performed by applying a bias voltage of 250 to 350 V to the photosensitive member. 4. The recycling developing method according to claim 1, wherein the replenishing virgin toner is mixed with the collected toner and supplied to a developing device. 5. The recycle developing method according to claim 4, wherein the supply of the supply virgin toner and the collected toner to the inside of the developing unit is ON-OFF controlled based on an output from a sensor for detecting the toner concentration in the developing unit. . 6. An ON-OF supply of the toner into the developing device.
6. The recycling developing method according to claim 5, wherein the toner density is controlled while changing a threshold value of a sensor detection output to be F-controlled according to an operation time of an image forming cycle.