JP2000181127A - Toner recycling type developing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent worsening of base fog caused by embedding of silica fine particles in a toner and to extend the life of a toner in a developing method reusing the toner which is not transferred. SOLUTION: In the toner recycling developing method, after an electrostatic latent image formed on the surface of a photoreceptor is developed with a replenished toner consisting of toner particles and an external additive deposited on the surface of the toner particles to visualize the image as a toner image and the toner image is transferred to a recording sheet, the replenished toner remaining on the photoreceptor is recovered, and the recovered toner is reused to visualize an image. Features of this method are (a) the toner particles contain 3 to 10 wt.% magnetic powder, (b) silica fine particles are deposited by >=0.4 wt.% on the surfaces of the toner particles, and (c) the ratio (X/Y) of the bulk density (X) of the recovered toner to the bulk density (Y) of the replenished toner is >=0.75.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an image forming apparatus such as a copying machine or a printer using electrophotography, and develops toner remaining on the surface of a photoreceptor after a process of transferring to a recording sheet. The present invention relates to a toner recycling type developing method which is reused as an agent.

[0002]

2. Description of the Related Art A dry developer applied to the developing system of the image forming apparatus includes a two-component developer in which a carrier (ferrite powder, iron powder, glass beads, etc.) which is a magnetic substance is mixed with a toner, It is roughly divided into a one-component developer in which a magnetic powder is carried on the toner itself. The toner used in these developers contains a binder resin and a colorant as main components, and further includes a wax for improving low-temperature fixability to a recording sheet and a polarity (positive or negative charge). A charge control agent or the like for application is added. The toner is manufactured into powder through a process such as melt-kneading, pulverization, and classification after these materials are mixed in a predetermined formulation.Finally, the toner is used for controlling fluidity, chargeability, cleaning properties, storage stability, and the like. External additives such as silica, titanium oxide, alumina, and various resin fine particles are adhered to the surface of the substrate and subjected to a surface treatment, and finally used as a developer. By the way, in recent image forming apparatuses, there is a mechanism for reusing (recycling) toner in a developing apparatus for the purpose of resource saving, reduction of running cost, etc., or as a measure against stricter waste regulations. Additional ones are provided. When the toner is reused, the toner (recovered toner) remaining on the surface of the photoconductor after the toner image developed on the surface of the photoconductor is transferred to a recording sheet is scraped off with a cleaning blade or a fur brush, and the like. In general, a method in which the toner is conveyed to a developer container containing the developer and mixed with the developer is adopted.

[0003]

However, since the external additive adheres to the surface of the toner collected as described above, the toner is scraped off from the photoreceptor by a cleaning blade, or the toner is collected up to the developer container. The external additive is buried in the toner (mainly in the binder resin) due to a thermal or mechanical load during the recovery step of being transported or agitated in the developer container, and In some cases, the function of the additive was not sufficiently exhibited. Specifically, the chargeability of the toner is particularly reduced or the rise of the charge is deteriorated,
Image defects such as deterioration of ground fog occurring on the image after fixing occur. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a toner recycling type developing method in which deterioration of background fogging caused by the above problem is effectively prevented and the life of the toner is extended.

[0004]

According to the toner recycling developing method of the present invention, an electrostatic latent image formed on the surface of a photoreceptor is developed by a replenishment toner comprising toner particles and an external additive attached to the surface. After the toner image is transferred to a recording sheet, the replenishment toner remaining on the photoconductor is recovered, and the recovered toner is reused for visualization. In the developing method, a) magnetic particles are contained in the toner particles in an amount of 3 to 10% by weight, b) silica fine particles are attached to the surface of the toner particles in an amount of 0.4% by weight or more, and c) the bulk specific gravity (X) of the recovered toner is A toner recycling type developing method, wherein the ratio X / Y to the bulk specific gravity (Y) of the replenishment toner is 0.75 or more. In the present invention, by using such a replenishment toner and a collected toner, even if the toner is subjected to a thermal or mechanical load in a collection process or the like, the collected toner has a sufficient triboelectric charging property, so that the toner life is extended. In addition, image defects due to deterioration of ground fog are prevented.

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 conceptually shows an image forming means of a copying machine. In the figure, reference numeral 1 denotes a photosensitive drum (photoconductor) that rotates in the direction of arrow A.
Around the corona charger 2, the optical system 3, the developer (one-component or two-component) 6 according to the rotation direction.
Container 4a, developing sleeve (developer) 4b, corona transfer device 5, cleaning blade 9
a, the static elimination means 10 are arranged in this order. A recording sheet (paper, resin film, or the like) indicated by reference numeral 7 is conveyed from the right side in the figure and passes between the photosensitive drum 1 and the corona transfer unit 5. Are disposed. The cleaning blade 9a scrapes off the toner (part of the toner image: collected toner) 6b remaining on the surface of the photosensitive drum 1 after the transfer, and the scraped collected toner 6b passes through the collection conveyance path 9b. After that, it is returned to the developer container 4a. In this case, the cleaning blade 9a and the recovery conveyance path 9b constitute the toner recovery unit 9,
The developing device 4 is constituted by a combination of the collecting means 9, the developer container 4a and the developing sleeve 4b.

The image forming process by the image forming means includes:
It is as follows. First, the surface of the rotating photosensitive drum 1 is uniformly charged by corona discharge of the corona charger 2, and then an electrostatic latent image is formed on the surface of the photosensitive drum 1 by exposure of the optical system 3. . The developing sleeve 4b rotates while adsorbing the developer 6 contained in the developer container 4a, and the toner in the developer 6 (in the case of a one-component system, all of the developer 6 is toner) is exposed to light. It is attracted to the electrostatic latent image formed on the surface of the body drum 1 by the action of the opposite polarity. Thus, the electrostatic latent image is visualized as the toner image 6a.
Next, the recording sheet 7 is transferred to the photosensitive drum 1 and the corona transfer device 5.
And the toner image 6a is superimposed on the toner image 6a, and a transfer charge is given from the back surface by the corona transfer device 5, whereby the toner image 6a is transferred onto the recording sheet 7. Thereafter, the recording sheet 7 passes between the fixing roller pair 8, and at that time, the toner image 6a is fixed on the recording sheet 7. On the other hand, the collected toner 6b remaining on the surface of the photosensitive drum 1 without being transferred to the recording sheet 7 is scraped off by the cleaning blade 9a, whereby the surface of the photosensitive drum 1 is cleaned. Is removed. The collected toner 6b scraped off by the cleaning blade 9a is returned to the developer container 4a via the collection conveyance path 9b, and is used again. Then, when a large number of recording sheets 7 are copied, the toner density of the developer 6 decreases, and the supply toner 11 is replenished in the developer 6 in order to maintain an appropriate toner density.

The above-mentioned developer is a one-component developer or a two-component developer. In the case of a one-component developer, the toner itself is used as the developer. In the case of a two-component developer, a carrier is mixed with the toner. The developer is used as a developer. In this case, it is preferable to use a replenishment toner that is replenished at the time of copying a large number of sheets as the toner constituting the developer at the start of copying in order to stabilize the charging property. Hereinafter, the materials constituting the replenishment toner in the present embodiment will be described. The main component of the replenishment toner of the present invention is a binder resin described below,
Silica fine particles are attached to toner particles containing a colorant and magnetic powder.

<Binder Resin> The binder resin is styrene, α-
Styrenes such as methylstyrene and chlorostyrene, acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and octyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methacrylic acid Octyl,
Methacrylates such as stearyl methacrylate,
Homopolymerized vinyl monomers such as glycidyl methacrylate, acrylonitrile, maleic acid, maleic ester, vinyl chloride, vinyl acetate, vinyl benzoate, vinyl methyl ketone, vinyl hexyl ketone, vinyl methyl ether, and vinyl isobutyl ether Alternatively, a vinyl resin such as a copolymerized styrene resin or an acrylic resin, an epoxy resin, a polyester resin, a polyurethane resin, or the like is used.

<Colorant> The colorant is carbon black,
Aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, etc. are used alone or in combination. The coloring agent needs to have a sufficient content of a sufficient concentration to form a visible image, and for example, is contained in an amount of about 1 to 20 parts by weight based on 100 parts by weight of the binder resin. .

<Magnetic Powder> Examples of the magnetic powder include fine particles such as ferrite powder, magnetite powder, and iron powder. As the ferrite powder, a mixed sintered body of MeO—Fe ₂ O ₃ is used in the present invention. Me in this case is Mn, Zn, N
i, Ba, Co, Cu, Li, Mg, Cr, Ca, V and the like, and any one or more of them can be used. A mixed sintered body of MeO—Fe ₃ O ₄ is used as the magnetite powder. Me in this case is the same as in the case of the ferrite powder. The magnetic powder is 3-1 in the replenishment toner.
It must be contained in an amount of 0% by weight, and if the amount is less than 3% by weight, an image having a lot of background fog is formed due to poor triboelectricity of the replenishment toner. If the content is more than 10% by weight, the replenishment toner is likely to be adsorbed on the surface of the developing sleeve, so that it is difficult to develop the photoreceptor, and a sufficient image density cannot be obtained.

The toner particles are mainly composed of the binder resin, the colorant and the magnetic powder.
The following materials are appropriately contained. <Low-melting point wax> The low-melting point wax is added for the purpose of lowering the melting start temperature of the toner to improve the low-temperature fixability, and synthetic wax, petroleum wax and the like are used. Examples of the synthetic wax include polypropylene wax and Fischer-Tropsch wax, and examples of the petroleum-based wax include paraffin wax, microwax, and petrotam. Other waxes include carnauba wax,
Natural waxes such as rice wax and candelilla wax, and synthetic fats and oils are used. <Charge Control Agent> The charge control agent is added to impart polarity, and is divided into those for positively charged toner and those for negatively charged toner. For positively charged toner, nigrosine dye, quaternary ammonium salt, viridinium salt, azine and the like are used. For negatively charged toner, azo-based metal-containing complexes and salicylic acid-based metal complexes are used. <Release Agent> The release agent is added in order to ensure releasability between the heat roller for fixing and the toner, and low molecular weight polypropylene, low molecular weight polyethylene or the like is used.

The toner particles constituting the present invention are produced by mixing the above-mentioned materials in a predetermined mixture, and subjecting the mixture to melt kneading, pulverization, and classification. In the replenishment toner of the present invention, the toner particles contain silica fine particles in an amount of 0.1%.
4% by weight or more, preferably 0.4 to 3% by weight. If the amount of the attached silica fine particles is less than 0.4% by weight, the replenishment toner has poor fluidity and triboelectricity, resulting in an image having a lot of background fog. 3% by weight
If the number is larger, the environmental resistance deteriorates, which is not preferable. In addition to the silica fine particles, the replenishment toner includes alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide, and various types of resin fine particles for controlling the fluidity, chargeability, cleaning property, and storage stability of the toner. An external additive other than the silica fine particles may be attached. In performing the surface treatment with the silica fine particles, a method of mixing and stirring with a general stirrer such as a turbine type stirrer, a Henschel mixer, a super mixer, or the like may be used.

In the present invention, the bulk specific gravity (X) (g / cm ³ ) of the recovered toner and the bulk specific gravity (Y) (g) of the replenishment toner are used.
/ Cm ³ ) should be at least 0.75, preferably 0.75 to 1.1. If it is less than 0.75, the frictional charging property of the collected toner is poor, and a difference occurs with the frictional charging amount of the replenishment toner, so that the replenishment toner is preferentially developed on the photoreceptor. Also,
Even when the ratio is greater than 1.1, the difference in the amount of triboelectric charge between the collected toner and the replenished toner is likely to occur similarly to the above, so that the image tends to have a lot of background fog. The bulk specific gravity of the replenishment toner and the recovered toner can be obtained by measuring according to JIS Z-5101. In order to make the ratio of the bulk specific gravity of the replenishment toner to the replenishment toner satisfy the above relation, the ratio can be obtained by adjusting the surface treatment method of the silica fine particles to be adhered to the surface of the replenishment toner. That is, when the silica fine particles are adhered to the surface of the toner particles using a stirrer such as a Henschel mixer, the mixing conditions are set such that the peripheral speed of the stirring blade is 20 m / sec to 40 m / sec, and the stirring time is 10 minutes to 10 minutes. It can be obtained by performing for 60 minutes. By stirring under such conditions, silica particles are embedded in advance in the particle surface of the replenishment toner, so that the replenishment toner becomes a recovered toner by receiving a thermal or mechanical load in a recovery step or the like. Since the bulk specific gravity hardly changes from the bulk specific gravity of the replenishment toner, the recovered toner is mixed with the replenishment toner without changing the triboelectric charging property. Therefore, since the collected toner has a sufficient triboelectric charging property, the life of the toner is prolonged, and image defects due to deterioration of background fog are prevented.

[0014]

The present invention will be described below based on examples and comparative examples. However, the present invention is not limited to these. <Preparation of Toner A for Electrophotography> Styrene-acrylate copolymer resin 81.2% by weight (Mitsui Chemicals: CPR-100) Polyethylene wax 3.5% by weight (Clariant: PE) -130) 7.8% by weight of carbon black (trade name: REGAL330, manufactured by Cabot) 1.5% by weight of metal-containing dye (trade name: Bontron S-34, manufactured by Orient Chemical Industries) 5.0% by weight of magnetite powder (titanium) Ingredients manufactured by Kogyo Co., Ltd .: BL-100) Raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded at 120 ° C. by a pressure kneader, pulverized by a jet mill, and then classified by a dry air classifier. Thus, toner particles having a volume average diameter of 10 μm were obtained. Then, the toner particles and hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd.)
R-972) was adjusted to 1.0% by weight of the hydrophobic silica, and a peripheral speed of 40 m / sec was obtained using a Henschel mixer.
For 10 minutes to obtain toner A for electrophotography.

<Preparation of Toner B for Electrophotography> 82.0% by weight of polyester resin (trade name: HP-301, manufactured by Nippon Synthetic Chemical Industry) 4.2% by weight of polyethylene wax (product name: PE-130, manufactured by Clariant) 8.3% by weight of carbon black (trade name: BLACK PEARLS430, manufactured by Cabot Corporation) 1.0% by weight of metal-containing dye (trade name: TRH, manufactured by Hodogaya Chemical Industry Co., Ltd.) 4.0% by weight of magnetite powder (manufactured by Toda Kogyo Co., Ltd.) (Product name: EPT-500) Raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded at 120 ° C by a pressure kneader, pulverized by a jet mill, and then classified by a dry air classifier to obtain a volume average. Thus, toner particles having a diameter of 10 μm were obtained. Then, the toner particles and hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd.)
R-972) was adjusted to 0.5% by weight of the hydrophobic silica, and a peripheral speed of 40 m / sec was obtained using a Henschel mixer.
For 15 minutes to obtain toner B for electrophotography.

<Preparation of Electrophotographic Toner C> (Comparative Example) In Example 1, mixing toner particles and hydrophobic silica with a Henschel mixer at a peripheral speed of 40 m / sec.
The toner C for electrophotography was obtained in the same manner except that the mixture was mixed for minutes.

<Preparation of Electrophotographic Toner D> (Comparative Example) In Example 2, the content of the polyester resin was changed to 83.
An electrophotographic toner D was obtained in the same manner except that the content of the magnetite powder was changed to 2.5% by weight and 5% by weight.

<Preparation of Electrophotographic Toner E> (Comparative Example) In Example 2, the content of the polyester resin was set to 74.
An electrophotographic toner E was obtained in the same manner except that the content of the magnetite powder was set to 12% by weight and 0% by weight.

<Preparation of Toner F for Electrophotography> (Comparative Example) In Example 2, the content of the polyester resin was changed to 82.
Electrophotographic toner F was obtained in the same manner except that the amount of hydrophobic silica was 3% by weight and the amount of hydrophobic silica was 0.2% by weight.

Next, 4 parts by weight of the electrophotographic toners A to F and 100 parts by weight of a silicone resin-coated ferrite carrier are mixed to prepare a developer, and the developer is recycled by the toner recycling method shown in FIG. An A4 original having a black ratio of 30% is converted to an A4 document by using the electrophotographic toner used in preparing the developer as a replenishing toner in a developing device of a copying machine having
Up to 30,000 sheets were copied on transfer paper, and the results obtained by the developing methods of Examples 1 and 2 and Comparative Examples 1 to 4 were obtained. Table 1 shows the bulk specific gravity (Y) (g / cm ³ ), 100
Bulk specific gravity (X) of the collected toner generated when copying the second sheet
(G / cm ³ ), X / Y, triboelectric charge amount (μc / g), image density, and background fog of the toner at the initial stage and after 30,000 copies. Here, the triboelectric charge was measured using a blow-off charge measuring device manufactured by Toshiba Chemical Co., and the image density was measured with a Macbeth reflection densitometer RD-914. Meter ZE200
It is a value measured at 0.

[0021]

[Table 1]

As is clear from the results shown in Table 1, in the developing methods of Examples 1 and 2, the triboelectric charge amount at the initial stage and after the 30,000th copy is stable with almost no change, and as a result, the image density is 1.37 or more. Thus, it was confirmed that copying was possible up to 30,000 sheets within a practically acceptable range of 0.72 or less. On the other hand, in Comparative Example 1, since the value of X / Y was smaller than 0.75, the triboelectric charge after 30,000 sheets became lower than that at the initial stage, the image density was low, the background fog was large, and there was a practical problem. confirmed. In Comparative Examples 2 to 4, it was confirmed that the image density was low or the image had a lot of background fog, and there was a practical problem.

[0023]

As described above, according to the present invention,
Even if the toner is subjected to a thermal or mechanical load in the recovery process or the like, the silica fine particles are prevented from being buried in the toner, so that even if recycling is repeated, the function of the silica fine particles is always maintained and the toner life is extended, Image defects due to deterioration of ground fog are always prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an image forming unit according to an embodiment of the present invention.

[Description of sign]

 Reference Signs List 1 photoconductor drum (photoconductor) 4a developer container 4b developing sleeve (developer) 6 developer 6a toner image 6b collected toner 7 recording sheet 9 toner collecting means 11 replenished toner

Claims (2)

[Claims] 1. An electrostatic latent image formed on a surface of a photoreceptor,
The toner image is developed into a toner image by developing with a replenishment toner comprising toner particles and an external additive attached to the surface thereof, and after the toner image is transferred to a recording sheet, the replenishment toner remaining on the photoconductor is recovered. And a toner recycling type developing method in which the recovered toner is reused for visualization, wherein a) magnetic particles are contained in the toner particles in an amount of 3 to 10% by weight; C) the ratio X / Y between the bulk specific gravity (X) of the recovered toner and the bulk specific gravity (Y) of the replenishment toner is 0.75 or more. 2. The toner recycle developing method according to claim 1, wherein the replenishment toner is obtained by depositing 0.4 to 3% by weight of silica fine particles on the surface of toner particles.