JPH0869123A - Recycling developing method using monolayer organic photoreceptor - Google Patents

Abstract

PURPOSE: To control the wear amt. of the surface of a photosensitive layer to a proper degree so that certain thickness of the photosensitive layer and enough surface potential of the photoreceptor can be maintained and an image of certain density can be formed even after about 30000 copies are done, and to effectively prevent disadvantages due to fog or surface contamination of the photoreceptor such as splashing of a toner. CONSTITUTION: An electrostatic image formed on the surface of a monolayer- type org. photoreceptor is developed with a magnetic brush containing a binary developer comprising a magnetic carrier and electric toner particles to form a toner image. After the toner image is transferred, the toner remaining on the photoreceptor is recovered by a cleaning means. The recovered toner is again used to form a magnetic brush. In this recycling developing method, the toner used consists of such toner particles subjected to surface treatment with large diameter alumina particles having 0.1 to 1.0μm average particle size by 0.1 to 1.3wt.% of the toner particles.

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 in electrophotographic devices such as copiers and printers, and more specifically, a static developing layer formed on the surface of a single-layer organic photoreceptor. The present invention relates to a recycling developing method in which an electric image is developed with a magnetic brush formed of a two-component magnetic developer.

[0002]

2. Description of the Related Art Generally, in image formation in electrophotography, the surface of a photoconductor is charged (mainly charged), and then an image is exposed to form an electrostatic image on the surface of the photoconductor, which is filled in a developing device. Is developed with a developing agent to form a visible toner image, the toner image is transferred to a predetermined sheet, and the toner image remaining on the photoreceptor after the transfer is cleaned by a cleaning blade or the like. The one cycle of the image forming process is completed by removing. As the above-mentioned developer, for example, a two-component magnetic developer consisting of an electrophotographic toner made of a colored resin composition and a magnetic carrier is typical, and a developer carrying sleeve provided in the developing device Development is carried out by conveying the developer in the form of a magnetic brush to the developing area, rubbing the magnetic brush on the electrostatic image on the photoconductor, and adhering the toner onto the electrostatic image.

By the way, a single-layer type organic photoconductor is well known as the photoconductor used in the electrophotography. This type of organic photoconductor is cheaper than other photoconductors,
The thickness of the photosensitive layer is set to about 30 μm, and it is usually designed to have a life of about 30,000 copies. Also,
As the toner used for developing the electrostatic image formed on such an organic photoconductor, a toner whose surface is treated with alumina is used. That is, by utilizing the softness of the organic photoconductor, when the surface of the photoconductor is rubbed with the magnetic brush of the developer containing the toner to develop the electrostatic image, the surface of the photoconductor is scraped off by the action of alumina. In this way, the surface of the photoconductor is always kept new, fog and toner scattering are prevented, and stable image formation is performed.

[0004]

However, when a toner surface-treated with alumina is used, the surface of the organic photoconductor is scraped off, so that the minimum film thickness (about 15 μm) necessary for forming an electrostatic image is sufficiently obtained. There is a problem that it becomes difficult to hold for a long period. For example, since the thickness of the photosensitive layer becomes 15 μm or less before the number of copies reaches 30,000, effective image formation cannot be performed. That is, in order to form an electrostatic image on the surface of the photoconductor, the voltage applied to the grid is usually adjusted appropriately using a scorotron (corona discharger with a grid) to keep the surface of the photoconductor at a constant surface potential. To be done. However, if the film thickness of the photosensitive layer is 15 μm or less, discharge breakdown occurs due to voltage application by the scorotron, and it becomes difficult to sufficiently charge the surface of the photoconductor, and as a result, the image density decreases. Therefore, it becomes impossible to effectively form an image.

Further, in general, a toner concentration sensor is provided in a developing device filled with a two-component type developer, and the toner concentration (T / D) of the developer composed of toner and carrier is kept constant. It is designed to control the range. This toner concentration control utilizes the fact that the toner concentration in the developer also changes according to the magnetic permeability of the developer. The toner concentration sensor detects the magnetic permeability of the developer and outputs the sensor output. This is performed by supplying toner to the developing device according to the value.

However, in the recycling developing method,
Since the collected toner whose physical properties (for example, fluidity) have been deteriorated due to external pressure such as cleaning is used again for development, the above-mentioned toner concentration control is also adversely affected. 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. According to this curve,
Toner supply ON-OFF threshold value is set to sensor output value 3
If it is set to V, the toner is replenished in the developing device when the toner concentration becomes 3.5% or less. However, when the collected toner comes to be replenished in the developing device, the relationship between the output of the density sensor and the toner density changes as shown by the curve B due to the change in the physical properties of the developer. Therefore, it becomes difficult to maintain a constant toner density by setting the threshold value described above.

Therefore, an object of the present invention is to provide a toner in a recycle developing method in which an electrostatic image formed on the surface of a single-layer type organic photoconductor is developed by a magnetic brush formed of a two-component magnetic developer. The amount of shaving on the surface of the photoconductor due to is controlled within a certain range, for example, a certain photosensitive layer thickness is secured over the number of copies of about 30,000 sheets, and stable without causing problems such as reduction in image density, fog, and toner scattering. To provide a method capable of forming an image. Another object of the present invention is to provide a recycle developing method capable of performing stable development by keeping the toner concentration constant even when the collected toner is reused.

[0008]

According to the present invention, a magnetic brush of a two-component developer comprising an electrostatic image formed on the surface of a single-layer type organic photoreceptor is composed of a magnetic carrier and electrophotographic toner particles. Is developed to form a toner image, and the toner remaining on the photoconductor after the toner image is transferred is collected by a cleaning unit, and the collected toner is used again for forming a magnetic brush for development. Method, the toner is at least 0.1 to 0.1 per toner particle.
A recycle developing method is provided which is characterized in that it is surface-treated with a large particle size alumina having an average particle size of 1.3% by weight of 0.1 to 1.0 μm.

In the method of the present invention, the supply of the replenishing virgin toner and the collected toner to the developing device is turned on based on the output from the sensor for detecting the toner concentration in the developing device.
The toner concentration of the developer is adjusted by performing the OFF control, and particularly, the threshold value of the sensor detection output that controls the ON-OFF of the toner supply 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 surface-treating agent for the toner in the developer has an average particle size of 0.1 to 1.0 μm, particularly 0.3 to
It is important to use large grain alumina of 0.8 μm. For example, if a toner surface-treated with alumina whose average is larger than the above range is used, a large amount of the photoconductor surface is scraped off by development (rubbing with a magnetic brush).
The progress of thinning of the photosensitive layer is rapid, the life of the photosensitive member cannot be extended to the number of copied sheets of about 30,000 sheets, and the image density is lowered by copying 10,000 to 20,000 sheets. When the average particle diameter of alumina is smaller than the above range, the photoconductor surface cannot be sufficiently scraped off, and it becomes difficult to keep the photoconductor surface new, and the photoconductor surface is contaminated. This causes fogging and toner scattering.

Further, the above-mentioned large-diameter alumina is 0.1 to 1.3% by weight, particularly 0.3 to 1.0% by weight, based on toner particles.
It is also important to use in an amount of. That is, when the amount of alumina used is larger than the above range, the surface of the photoconductor is also scraped off in a large amount and the image density is lowered. When the amount of alumina is less than the range, the photoconductor surface is sufficiently scraped off. Fogging and toner scattering. The effect of using the above-mentioned large-diameter alumina is sufficiently clearly shown in Examples and Comparative Examples described later.

Further, in the recycle development method of the present invention, it is preferable that the replenishing virgin toner and the recovered toner recovered from the cleaning device are remixed in advance and supplied into the developing device. As a result, the physical properties of the developer in the developing device are uniform and stable, and there is almost no effect on the image due to the mixing of the collected toner.

In the recycle developing method of the present invention, the toner concentration of the developer in the developing device is detected by the sensor, and the virgin toner and the recovered toner are replenished into the developing device based on the detected value, so that the toner concentration is kept constant. It is possible to effectively maintain the toner concentration of. Especially toner supply is ON
By changing the sensor detection value, which is the threshold of the OFF control, according to the operation time of the image forming cycle,
It is possible to always maintain a constant toner density. The operation time of the image forming cycle corresponds to, for example, the operation time of the developing sleeve provided in the developing device. Therefore, if the threshold value is changed according to the integrated value of the drive time of the drive motor of the sleeve. Good.

[0014]

Preferred Embodiment of the Invention

(Electrophotographic Apparatus) In FIG. 1, which schematically shows an example of an electrophotographic apparatus for suitably carrying out 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. 4, a transfer charging device 5, and a cleaning device 6 such as a cleaning blade are provided in this order, and further, a fixing device 7 is provided adjacent to the photosensitive drum 1.

That is, the main charging device 2 causes the photosensitive drum 1
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. The electrostatic image is developed by the developing device 4 to form a visible toner image, which 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 photoconductor drum after the transfer is removed and collected from the surface of the photoconductor drum 1 by the cleaning device 6. In this way, one stroke of the image forming cycle is completed.

(Developing Device) The developing device 4 is provided with a developing sleeve 10 having a magnet inside and a developing device 11, and in the developing device 11, a two-component system composed of an electrophotographic toner and a magnetic carrier. It is filled with magnetic developer. That is, the developer is conveyed by the sleeve 10 in the form of a magnetic brush, the magnetic brush is rubbed against the surface of the photosensitive drum 1, and a toner image is formed by attaching charged toner to the electrostatic image. is there.

The structure of the developing device 4 is shown in FIG. FIG.
As can be seen from FIG. 2, the developing device 11 is divided into two chambers 4a and 4b by the partition wall 20,
Spirals 21 and 22 are provided in each room, respectively. The partition wall 20 has a toner concentration sensor 23.
Is provided. Further, one chamber 4b communicates with a toner replenishing hopper 25 having a spiral 24 incorporated therein, and a toner tank 26 filled with replenishing virgin toner is arranged above the hopper 25. That is, the virgin toner in the toner tank 26 is supplied into the hopper 25, and the spiral 24 causes the developing device 11 to move.
It is replenished into the inner chamber 4b. The virgin toner replenished in the chamber 4b is supplied to the chamber 4b by the spirals 22 and 21.
And 4a, is mixed with the developer already existing in the developing device 11, and is supplied from the chamber 4a to the sleeve 10 for development. 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 independently driven separately from the motor 26.
ON-OFF control is performed by the detection output of 3.

On the other hand, a recovery toner storage tank 30 is provided in communication with the hopper 25, and the toner recovered by the cleaning device 6 is temporarily stored in the storage tank 30 by spontaneous dropping or suction. It In this storage tank 30, a spiral 31 is provided at the bottom, its tip extends to the inside of the hopper 25, and a paddle 32 is provided at the tip thereof.
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, is mixed and stirred with the replenishing virgin toner by the spiral 24, and is replenished into the developing device 11 together with the virgin toner for development. In general, the spiral 31 and the paddle 32 can be integrally driven 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, as the magnetic carrier of the developer filled in the developing device 11 of the developing device 4, a granular magnetic material known per se, for example, ferric tetroxide ( Fe ₃ O ₄ ), ferric oxide (γ-F
e ₂ O ₃ ) and other iron oxide-based magnetic materials; zinc iron oxide (ZnF)
e ₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ),
Iron oxide cadmium (CdFe ₂ O ₄ ), iron oxide gadolinium (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuFe
₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), iron nickel oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFeO)
₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnF)
e ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ) and their composites and the like ferrite-based magnetic materials; iron powder (Fe), cobalt powder (Co), nickel powder (Ni) and other magnetic powder-based magnetic materials And the like, and preferably C
soft ferrite containing at least one metal component selected from the group consisting of u, Zn, Mg, Mn and Ni,
For example, Cu-Zn-Mg ferrite or the like is used. The average particle size of these magnetic carriers is usually between 65 and 10
It is preferably in the range of 5 μm.

The above-mentioned magnetic carrier may be used alone, or two or more kinds may be used in combination, or carrier particles may be resin-coated and used. Such a resin is not particularly limited as long as it can form a film having an appropriate hardness and does not adversely affect the triboelectrification property, but in general, a silicone resin, an acrylic modified silicone resin, a fluororesin, an acrylic resin, Epoxy-modified acrylic resin, styrene resin,
One or more of styrene-acrylic resin, olefin resin, ketone resin, phenol resin, xylene resin, diallyl phthalate resin, melamine resin and the like are used. The resin coating using such a resin can be performed, for example, by dissolving the resin in a suitable solvent and spraying in a fluidized bed.

The mixing ratio of the magnetic carrier particles and the toner is
Generally a weight ratio of 98: 2 to 90:10, especially 97: 3.
It is preferable that the weight ratio is from 92 to 8.

(Toner) In the present invention, as the start toner and the replenishing virgin toner used in combination with the above magnetic carrier, a colorant pigment and, if necessary, a charge control agent and a release agent are contained in the fixing resin. Toner particles known per se in which toner compounding agents such as
The one whose surface is surface-treated with at least the above-mentioned average particle size and amount of alumina is used.

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

The colorant pigment is usually the fixing resin medium 10
It is used in an amount of 2 to 20 parts by weight, especially 5 to 15 parts by weight, based on 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, Hansa yellow G, Hansa yellow 10G, benzidine yellow G,
Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigment Red lead yellow molybdenum, Molybden orange, Permanent orange GTR, Pyrazolone orange, Balkan orange, Induslen brilliant orange RK, Benzidine orange G, Induslen brilliant orange GK. Red pigment Bengal, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, resole 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, phthalocyanine blue partial chlorinated compound, fast sky blue, indanthrene blue B
C. Green pigment chrome green, chrome oxide, pigment green B,
Malachite Green Rake, 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 control agent include oil-soluble dyes such as nigrosine base (CI.50415), oil black (CI.26150), and spirone black, metal-containing azo dyes, naphthenic acid metal salts, and the like. Metallic alkylalicylic acid salts, fatty acid soaps, resin acid soaps and the like are used. The amount of these charge control agents to be compounded is usually 0.1 to 10 parts by weight, especially 0.1 part by weight, per 100 parts by weight of the fixing resin.
5 to 5 parts by weight.

Further, when the toner image formed by development and transferred onto a predetermined paper is fixed by heat fixing, a releasing agent is blended in order to impart releasability at the time of heat fixing. As the mold release agent, a polyrefin resin, particularly a low molecular weight polypropylene is usually preferably used. The amount of such a 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 the fixing resin can be produced by a method known per se, such as a pulverizing and classifying method, a melt granulating method, a spray granulating method and a polymerization method. The crushing classification method is generally used. For example, each toner component is pre-mixed with a mixer such as a Henschel mixer, and then kneaded using a kneading device such as a twin-screw extruder, and the kneaded composition is cooled, pulverized, and classified into toner particles. To do. The toner particles have a median diameter of 5 to 15 μm, particularly 7 to 12 μm, as measured by a Coulter counter.
It should be in the range of m.

The above-mentioned toner particles are
Surface-treated with 0.1 to 1.3% by weight, especially 0.3 to 1.0% by weight, large particle size alumina having an average particle size of 0.1 to 1.0 μm, especially 0.3 to 0.8 μm. As a result, the amount of scraping off the surface of the photoconductor at the time of development can be made moderate, and a constant thickness of the photosensitive layer can be maintained for a certain period. Further, in the present invention, a surface treating agent other than alumina can be used in combination, as long as the object of the present invention of making the amount of scraping off the surface of the photosensitive member moderate is not impaired. As such other surface treatment agent, for example, hydrophilic or hydrophobic fine silica powder, a particle size of 0.005 to 0.
A fine powder treatment agent of 05 μm can be exemplified. These can be used alone or in combination of two or more. Such a fine powder treating agent has the function of improving the fluidity of the toner, preventing the mutual aggregation of the toner particles, and ensuring a certain amount of triboelectric charge, and usually 0.
It is preferably used in an amount of 1 to 2.0% by weight.

For the surface treatment of the toner particles with the above-mentioned large-diameter alumina and the fine powder treating agent, the large-diameter alumina and a small amount of the fine powder treating agent are intimately mixed under pulverization conditions, and the mixture and the remaining amount are left. It is advisable to add the above fine powder treating agent to the toner to sufficiently disintegrate it.

The above-mentioned toner is mixed in advance with the magnetic carrier in the above-mentioned amount ratio, and is used as the starting developer in the developing device 1.
1 and the toner tank 26 is used as a replenishing virgin toner for use.

(Photoreceptor) In the present invention, as the photoreceptor drum 1, a monodispersed layer having a photosensitive layer formed by dispersing a charge generating material together with a charge transporting agent in a binder resin on a conductive substrate. Type organophotoreceptors are used.

Examples of the charge generating material include selenium, selenium-tellurium, amorphous silicon, pyrylium salt,
Azo pigments, disazo pigments, Ansanthuron pigments,
Phthalocyanine pigments, indigo pigments, slene 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, particularly 0.5 to 2.0% by weight.

As the charge transport material, a hole transport material or electron transport material known per se 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-pyrazoline, p-diethylaminobenzaldehyde- (diphenylhydrazone) and the like. Examples of the electron transport material 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 can be exemplified. 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, in particular 20 to 30% by weight.

As the binder resin, various resins such as styrene-based polymers, styrene-butadiene-based polymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic polymers, styrene-acrylic resins are used. 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 silicone resins, ketone resins, polyvinyl butyral resins, polyether resins, phenol resins; and photocurable resins such as epoxy acrylate and urethane acrylate.

The photosensitive layer is formed by, for example, dissolving or dispersing a predetermined amount of the above-mentioned binder resin, charge generating material and charge transporting material in a suitable organic solvent to prepare a coating liquid, and then conducting the coating liquid. It is formed by coating on a flexible substrate and drying. The thickness of the photosensitive layer is generally in the range of 20 to 40 μm, and preferably 25 to 35 μm. As the conductive substrate, any conductive substance such as an inorganic conductor such as aluminum, gold, silver, copper, nickel, tin oxide, indium oxide, or copper iodide; an organic polymer such as polyacetylene or polyvirol is used. be able to.

In the present invention, it is generally preferable to use the photosensitive drum 1 made of the above-mentioned organic photosensitive member having a diameter of 15 mm or more. If the diameter is too small, the frequency of contact between the magnetic brush and the surface of the photosensitive drum becomes high even if the number of copies is the same, so that the amount of abrasion of the photosensitive layer may become excessive.

(Developing Method) In the development using the apparatus shown in FIGS. 1 and 2, as described briefly above, main charging and image exposure are carried out while rotating the photosensitive drum 1, and the image is formed on the drum. This is performed by forming an electrostatic image and rubbing it against a magnetic brush of the developer carried by the developing sleeve 10. In the present invention, since a monodispersed layer type organic photoconductor having a high residual potential is used as the photoconductor drum 1 in such development, it is preferable to apply a bias voltage to the photoconductor drum 1. Such bias voltage is typically 250 to 350V, especially 280 to 32V.
It is preferably in the range of 0V. 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, disadvantages such as carrier pulling and dielectric breakdown of the photosensitive layer cannot be avoided. .

The conveying direction of the magnetic brush 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 the opposite direction. The moving speed d _{1 of the} magnetic brush (corresponding to the peripheral speed of the sleeve 10 in the case of the sleeve rotation system) and the peripheral speed d _{2 of the} drum 1 are in the range of 2.0 to 4.0 (d ₁ / d ₂ ). It is desirable to do. Further, the photosensitive drum 1 and the developing sleeve 1
It is usually desirable that the distance from 0 be in the range of 0.55 to 0.85 mm.

According to the present invention, the toner image formed on the photoconductor drum 1 by the above-mentioned development is transferred to the predetermined paper 8 by the transfer device 5, and the toner remaining on the photoconductor drum 1 after the transfer. Are collected by the cleaning device 6, resupplied into the developing device 11 together with the virgin toner, and recycled. Such recycling development proceeds in the next step, which is indicated by the change in toner of the developer in the developing device 11. Development with start developer toner. Development with start developer toner + replenishing virgin toner + collected toner. Development with replenishing virgin toner + collected toner. Development with collected toner.

In the present invention, the replenishment virgin toner and the collected toner are replenished when the toner density of the developing device 11 becomes a certain value or less. 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 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 which are 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 replenished in the developing device 11.

As described above, the recovered toner is mixed with the virgin toner for replenishment in advance and is replenished in the developing device 11, whereby the homogeneity of the developer is maintained and the physical property of the developer is prevented from being suddenly deteriorated. It is extremely suitable for this.

In the method of the present invention, the developing device 1 described above is used.
It is preferable to set and change the ON-OFF threshold value of the toner replenishment into 1 according to the copying time, for example, the integrated value of the driving time of the motor 26 that drives the sleeve 10. That is, the ON-OFF threshold value is set every time the integrated value of the driving time of the motor 26 becomes a constant time. As a result, even when the collected toner whose physical properties are deteriorated due to external pressure due to cleaning or the like is replenished in the developing device 11, the threshold value is changed in accordance with the replenished toner so that a constant toner density is always maintained. It is possible to adjust like this.

[0043]

The present invention will be further described in the following examples.

Example 1 Preparation of Toner Particles : According to the following formulation, each agent was melt-kneaded by using a twin-screw extruder, the kneaded product was crushed by a jet mill, and 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 treating agent: The following surface treating agent was prepared. Alumina pretreatment agent: Alumina having an average particle size of 0.1 µm (AKP-50 manufactured by Sumitomo Chemical) and hydrophobic silica fine powder (TS-720 manufactured by Cabot Corporation) having an average particle size of 0.015 µm were weighed 10: 1. The mixture was mixed with Vitamix at a ratio of 1 minute to obtain an alumina pretreatment agent.

Preparation of toner and starting developer ; the above-mentioned alumina pretreatment agent was added to the toner particles prepared above.
0.2 wt% was added and mixed for 2 minutes with a Henschel mixer to prepare an alumina-treated toner. To this alumina-treated toner, a fine powder of hydrophobic silica with an average particle size of 0.015 μm was used.
0.3 wt% was added and mixed with a Henschel mixer for 2 minutes to prepare a replenishing virgin toner (alumina content: 0.
18% by weight). In addition, the toner prepared above and an average particle size of 8
A 0 μm ferrite carrier was mixed in a ball mill (75 rpm, 2 hours) to obtain a starting developer having a toner concentration of 4.5%.

Experiment Copier DC manufactured by Mita Kogyo Co., Ltd. using a monodisperse layer type organic photoreceptor
-2556 was modified into the recycling system machine shown in FIG. 1 and the following developing conditions were set. Monodisperse type organic photoconductor; Photosensitive layer thickness: 30 μm Binder resin: Polycarbonate Charge generator: Perylene pigment (5 wt% per resin) Charge transport agent: Ethylcarbazole hydrazone (90 wt% per resin) Photoconductor surface charging potential: 800V Photosensitive drum diameter: 78mm Developing sleeve diameter: 34mm Drum-sleeve distance: 0.75mm Drum-sleeve peripheral speed ratio: 3.0 Bias voltage: 300V

Under the above conditions, 30,000 copies were continuously copied using the above-prepared starting developer and replenishing virgin toner, and the abrasion resistance, fog and toner scattering of the photosensitive drum were evaluated. The results are shown in Table 1. The toner concentration is controlled by changing the ON-OFF control threshold value for toner replenishment according to the sensor output according to the flowchart shown in FIG. The evaluation of each test item was performed as follows.

Scratchability of drum: judged by reduction of image density due to scraping of photosensitive layer. The criteria are as follows. ◯: No decrease in image density. X: A decrease in image density due to a decrease in surface potential is recognized. Fog: Shown by the fog density in the initial (first sheet), 15,000th, and 30,000th images. Toner scattering: The presence or absence of toner scattering in the apparatus and whether or not the formed image has toner falling due to toner scattering were visually observed. The criteria are as follows. ◯: No toner scattering was observed in the apparatus, and there was no effect on the image. Δ: Toner scattering in the apparatus was slightly observed, but no influence on the image was recognized. X: Toner drop is observed in the image.

(Example 2) The amount of the alumina pretreatment agent added was
Toner prepared by replacing 1.3% by weight (alumina content:
1.18% by weight) was used as a replenishing virgin toner, and the start developer obtained using the toner was used,
An experiment was conducted in exactly the same manner as in Example 1. The results are shown in Table 1.

Example 3 Example 1 was repeated except that a toner prepared by using alumina having an average particle size of 1 μm was used as a replenishing virgin toner and the start developer obtained by using the toner was used. An experiment was conducted in exactly the same manner as. The results are shown in Table 1.

Example 4 The amount of the alumina pretreatment agent added was
Toner prepared by replacing 1.3% by weight (alumina content:
1.18% by weight) was used as a replenishing virgin toner, and the start developer obtained using the toner was used,
An experiment was conducted in exactly the same manner as in Example 3. The results are shown in Table 1.

Comparative Example 1 The amount of the alumina pretreatment agent added was
Toner prepared by replacing 0.15% by weight (alumina content:
An experiment was conducted in exactly the same manner as in Example 1 except that 0.136% by weight) was used as a replenishing virgin toner and the starting developer obtained by using the toner was used. The results are shown in Table 2.

Comparative Example 2 The amount of the alumina pretreatment agent added was
Toner prepared by replacing 1.4% by weight (alumina content:
1.27% by weight) was used as a replenishing virgin toner, and the start developer obtained using the toner was used.
An experiment was conducted in exactly the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3 The amount of the alumina pretreatment agent added was
Toner prepared by replacing 0.15% by weight (alumina content:
The experiment was conducted in exactly the same manner as in Example 3 except that 0.136% by weight) was used as a replenishing virgin toner and the starting developer obtained by using the toner was used. The results are shown in Table 2.

Comparative Example 4 The amount of the alumina pretreatment agent added was
Toner prepared by replacing 1.4% by weight (alumina content:
1.27% by weight) was used as a replenishing virgin toner, and the start developer obtained using the toner was used.
An experiment was conducted in exactly the same manner as in Example 3. The results are shown in Table 2.

(Comparative Example 5) A comparative example 5 was carried out except that a toner prepared by using alumina having an average particle diameter of 1.3 μm was used as a replenishing virgin toner and the starting developer obtained by using the toner was used. An experiment was conducted in exactly the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 6) Example 6 except that a toner prepared by using alumina having an average particle diameter of 0.05 μm was used as a replenishing virgin toner and the starting developer obtained by using the toner was used. The experiment was performed in exactly the same manner as 1. The results are shown in Table 2.

[0059]

[Table 1]

[0060]

[Table 2]

In Comparative Example 2, a decrease in image density due to the abrasion of the photosensitive layer was recognized at the time of copying 25,000 sheets. Further, in Comparative Example 4, when 10,000 copies were made,
In Comparative Example 5, at the time when 20,000 copies were made, a decrease in image density due to abrasion of the photosensitive layer was observed.

[0062]

According to the present invention, a two-component magnetic developer using a toner surface-treated with a large particle size alumina having an average particle size of 0.1 to 1.0 μm is used as a surface treatment agent. Then, by developing the electrostatic image formed on the surface of the monodisperse layer type organic photoconductor, the amount of abrasion on the surface of the photoconductor layer is made moderate, and even if about 30,000 sheets are copied, the photosensitivity is kept constant. The layer thickness is secured, the surface potential of the photoconductor is sufficiently maintained, an image having a constant density can be formed, and inconveniences due to surface contamination of the photoconductor such as fogging and toner scattering can be effectively prevented. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an electrophotographic apparatus for preferably carrying out a recycling development 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 the relationship between the output of a toner concentration sensor and toner concentration.

FIG. 4 is a toner supply ON-O in the experiment of the embodiment.
FIG. 6 is a diagram showing a change in the threshold value of the output of the toner density sensor that performs FF control.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G03G 15/08 115 507 C 15/09 21/10 G03G 21/00 326 (72) Inventor Ryo Fujisawa 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Industrial Co., Ltd.

Claims (8)

[Claims] 1. A toner image is formed by developing an electrostatic image formed on the surface of a single-layer organic photoreceptor with a magnetic brush of a two-component developer composed of magnetic carriers and electrophotographic toner particles. In the recycle developing method, in which the toner remaining on the photoconductor after transferring the toner image is collected by a cleaning unit, and the collected toner is used again to form a magnetic brush for development, at least toner particles are used as the toner. A recycling developing method characterized in that a surface-treated alumina having a large particle diameter of 0.1 to 1.3% by weight and an average particle diameter of 0.1 to 1.0 μm is used. 2. The recycle development method according to claim 1, wherein the toner is surface-treated with silica fine powder having an average particle diameter of 0.05 μm or less together with the large particle diameter alumina. 3. The recycle developing method according to claim 1, wherein the photosensitive member is a drum-shaped member having a diameter of 15 mm or more. 4. The photosensitive member has an initial photosensitive layer thickness of 2
The recycle developing method according to claim 3, wherein the developing method is set in the range of 0 to 40 µm. 5. 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 photoconductor. 6. The recycle developing method according to claim 1, wherein a replenishing virgin toner is supplied together with the recovered toner into a developing device to form a magnetic brush. 7. The recycling developing method according to claim 6, wherein the supply of the replenishing virgin toner and the recovered toner into the developing device is controlled to be ON-OFF based on the output from the sensor that detects the toner concentration in the developing device. . 8. The toner supply into the developing device is turned on-of.
The recycle developing method according to claim 7, wherein the toner concentration is controlled while changing the threshold value of the sensor detection output for F control according to the operation time of the image forming cycle.