JPH07120969A - Magnetic toner and electrophotographic method - Google Patents

Abstract

PURPOSE:To impart a high electrostatic charge characteristic and high flow characteristic to the magnetic toners by mixing the toners under a reduced pressure. CONSTITUTION:An external adding and mixing device is composed of a mixing tank 1 of a specified volume, agitating vanes 2 for agitating powders, a motor 3 for rotating these agitating vanes 2, an air seal 4 for a shaft part, an oil diffusion vacuum pump 5, a filter 6, the magnetic toner 7 and an air generator 8. The mixing tank 1 is connected via the filter 6 installed on the tank to the vacuum pump 5 to reduce the pressure therein. Namely, the magnetic toner 7 is produced by executing the external addition treatment to mix and adhere external additive to toner base material particles composed of at least a binder resin and magnetic material by using the mixing device composed of at least the mixing tank 1 of the specified volume and the rotatable agitating vanes 2 for applying shearing force to the powder and by reducing the pressure in the mixing tank 1. The magnetic toner is used in the electrophotographic device which has a transporting pipe for sending the waste toners to a toner hopper of a developing device and has a stage for recycling the waste toners remaining after transfer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner used in copying machines, printers and facsimiles, and an electrophotographic method.

[0002]

2. Description of the Related Art In recent years, electrophotographic apparatuses have been shifting from the purpose of office use to personal use, and there is a demand for a technique for realizing downsizing and maintenance-free operation. Therefore, conditions such as maintainability such as recycling of waste toner and less ozone exhaust are required.

The printing process of the copying machine and printer of the electrophotographic method will be described. First, the photoreceptor is charged to form an image. As a charging method, a conventionally used corona charger is used, and in recent years, a contact type charging method in which a conductive roller is directly pressed against the photoreceptor to reduce the amount of ozone generation is used. Charge the surface uniformly. After the photoconductor is charged, in the case of a copying machine, the copy original is irradiated with light and the reflected light is applied to the photoconductor through a lens system. Or, if it is a printer, send an image signal to a light emitting diode or laser diode as an exposure light source,
A latent image is formed on the photoconductor by turning the light on and off. When a latent image (high or low surface potential) is formed on the photoconductor, the photoconductor is a toner (diameter of 5 μm
Visible image.

The toner adheres to the surface of the photoconductor according to the level of the surface potential of the photoconductor, and is electrically transferred to a copy sheet.
That is, the toner is charged in advance positively or negatively, and a charge having a polarity opposite to the polarity of the toner is applied from the back surface of the copy sheet to electrically attract the toner. Up to now, a corona discharger has been widely used as the charge applying method as in the charging method, but in recent years, a transfer device using a conductive roller has been put into practical use in order to reduce the ozone generation amount. When transferring, not all the toner on the photoconductor is transferred to the copy paper,
Some remain on the photoreceptor. This residual toner is scraped off by a cleaning blade or the like in the cleaning section to become waste toner.

In the conventional electrophotographic method, particularly in the one-component developing method, the waste toner is not reused but is discarded. These days
From the viewpoint of protecting the global environment, the importance of controlling the unrestricted disposal of industrial waste is being emphasized. Toner is a consumable powder, and careless disposal leads to environmental pollution. Therefore, the reuse of this waste is an important issue.

Conventionally, there are a cascade developing method, a touchdown developing method, a jumping developing method and the like as a developing method for making an electrostatic latent image into a visible image by an electrophotographic method. Among them, the cascade developing method shown in US Pat. No. 3,105,770 is known as a developing method in which a developer is directly sprinkled on the photoreceptor. The cascade developing method is an electrophotographic method, which is the first developing method used in a copying machine. Further, there is US Pat. No. 3,866,574 as a method of applying an AC bias to the developing roller to fly the one-component toner and develop the toner. According to the present invention, the AC bias applied to the developing roller is used for the purpose of activating the movement of the toner, and the toner flies to the image portion and returns to the middle in the non-image portion.

Further, as a modification of the technique for applying the AC bias, there is a jumping developing method disclosed in JP-B-63-42256. In this jumping developing method, toner is carried on a toner carrier, and a rigid or elastic regulating blade is installed on the toner carrier with a minute gap from the carrier. Then, the regulation blade regulates the toner in a thin layer, conveys the toner to a developing portion, and attaches the toner to the image portion of the photoconductor by an AC bias there. The technical idea of the Japanese Patent Publication No. 63-42256 differs from the above-mentioned US Pat. No. 3,866,574 in that the toner reciprocates in the image portion and the non-image portion.

As is well known, the toner for electrostatic charge development used in these developing methods is generally composed of a resin component, a coloring component composed of a pigment or a dye, and an additive component such as a plasticizer and a charge control agent. Has been done. As the resin component, natural or synthetic resins are used alone or in a proper mixture.

[0009]

However, in the developing method as described above, it is well known in the art that the cascade developing method is not good at reproducing a solid image. Further, there is a problem that the device becomes large and complicated. Further, the developing device of U.S. Pat. No. 3,866,574 has the drawback that the device requires high precision, is complicated, and is expensive. In the jumping development method, it was essential to form a very uniform thin layer on a toner carrier carrying a toner layer. Further, in this method, a so-called sleeve ghost phenomenon occurs in which the history of the previous image remains in the thin toner layer on the toner carrier and an afterimage appears in the image. Further, there is a drawback that the device is complicated and the cost is high.

Therefore, the inventor of the present invention has proposed an electrophotographic method (Japanese Patent Laid-Open No. 5-72890) capable of realizing the downsizing and high performance of the developing device. The developing device of this electrophotographic method is a toner collecting electrode roller (hereinafter, referred to as a photoconductor containing a fixed magnet and a magnet facing the photoconductor with a predetermined gap therebetween).
This is a structure in which unnecessary toner in the non-image portion is removed by an electrode roller). Therefore, this developing device faithfully reproduces a solid image and does not generate a sleeve ghost, which is a method that enables further downsizing, simplification, and cost reduction of the apparatus.

However, in order to achieve high image quality by using this developing device, higher performance toner characteristics are required. Since this developing device does not use a regulating blade for regulating the toner in a thin layer, the toner is not regulated in the layer and is conveyed to the developing field which is a narrow gap space between the photoconductor and the electrode roller. Therefore, there are few places and spaces required for the toner to be triboelectrically charged to obtain a desired amount of charge, and the toner requires higher charging characteristics and higher fluidity characteristics than ever before.

At the level of fluidity of the toner used in the conventional one-component developing method and two-component developing method, unevenness occurs in the solid black image area and the halftone image area, and the background fog occurs in the non-image area. Will increase. This phenomenon remarkably appears in the toner having low fluidity. The reason for this is that a toner having a low fluidity has a low contact probability with the developing member, so that a sufficient triboelectric charge amount cannot be obtained. Also, the triboelectrification varies among the toners,
A uniform toner charging property cannot be obtained. However, it is considered that a toner having a high fluidity has a uniform contact property with the developing member, a high charge amount can be obtained, and a high-quality image can be obtained.

In order to improve the fluidity of the toner, conventionally, a measure has been taken to increase the amount of external additive such as silica which is a fluidity imparting agent. It is disclosed in Japanese Patent Publication No. 54-16219. However, if the amount of the external additive such as silica is increased, the fluidity is improved to some extent with the addition amount, but there is a limit. In addition, suspended matter of silica increases, and this silica serves as nuclei, and the silica is struck by the pressing force of the cleaning blade to cause scratches. Then, so-called photoconductor filming occurs in which silica or toner is fixed on the photoconductor.

Particularly, in the electrophotographic method according to the present invention, since the toner is adhered to the entire photoconductor during development, the toner and the photoconductor are in contact with each other longer than in the conventional one-component developing method. Therefore, if the generation of floating silica is not suppressed as much as possible, filming occurs on the photoconductor.

Further, a suspended matter of silica adheres to a solid black image portion to generate a white spot. As described above, increasing the amount of silica has many adverse effects and cannot solve the problem.

Conventionally, methods for externally treating silica have been described in JP-A-2-289859 and JP-A-53-58244. However, in JP-A-2-289859, only the rotation speed and time of stirring are optimized, and this makes it difficult to obtain stability during manufacturing. Moreover, since the conditions are pinpoints, the manufacturing specifications will be severe, and optimization of the conditions alone will not solve the problem.

Further, it is very difficult to uniformly mix an ultrafine powder having a low specific gravity such as silica and a magnetic toner having a considerably higher specific gravity than silica by a known mixing means such as a Henschel mixer. .

Further, ultrafine powder such as silica is apt to agglomerate and must be crushed and used before external addition treatment. However, since such ultrafine powder aggregates immediately after being crushed, it does not solve the problem because it reaggregates when externally added.

In the conventional magnetic toner, the magnetic substance is internally added to the binder resin. The toner is crushed into fine particles. At this time, a magnetic material having a resistance lower than that of the binder resin is exposed on the surface of the toner, so that the electric charge obtained by the triboelectric charging easily leaks, and it is difficult to obtain a high charge amount in the magnetic toner. Further, this magnetic material has a drawback that it tends to generate a reverse polarity toner upon contact with a binder resin.

In recent years, global environmental protection has become a big problem. In conventional copying machines, laser printers, laser plain paper fax machines, etc., toner is developed on the photoconductor in the developing process, and the toner is transferred to the paper in the transferring process. At this time, a part of the toner remains on the photoconductor. Part of the toner is scraped off in the cleaning process. The cleaned toner becomes waste toner. In the conventional method, especially the one-component developing method, most of the waste toner is discarded and not recycled.

The problems when recycling the waste toner are (1) The fluidity of the waste toner is lowered due to stress, and the charge amount varies.

(2) Toner aggregates with reduced fluidity are clogged by the toner layer regulating blade for development.

[0023]

This is because when the waste toner scraped off from the photosensitive member in the cleaning step is recycled again for development, the conventional toner has a non-uniform charge amount distribution when the waste toner and new toner in the developing device are mixed. However, the reverse polarity toner increases, and the quality of the copied image deteriorates.

One of the factors is considered to be the accumulation of silica aggregates. That is, silica aggregates in the toner are released and are unevenly distributed in the cleaning box. It is considered that this is accumulated and the composition of the waste toner gradually changes, which affects the charging characteristics and the flow characteristics.

FIGS. 4 and 5 are schematic views of a developing device of each example according to the conventional one-component developing method. In both figures, 302 is a photoconductor, 301 is a developing sleeve which is a toner carrier, 303 is a toner layer regulating blade, and 304 is toner. This developing device has a structure in which a toner layer restriction blade 303 such as a rigid body or an elastic body is provided in a narrow gap or in contact with the developing sleeve 301 to form a thin layer of toner 304 on the developing sleeve 301.

In FIG. 4, an elastic toner layer regulating blade 30 is used.
3 is brought into contact with the developing sleeve 301 with a constant pressing force to form a thin layer of toner. Further, in FIG. 5, a rigid toner layer regulating blade 303 is installed in a narrow gap with the developing sleeve 301.

In this configuration, when the waste toner is recycled, aggregates of the waste toner cause clogging in the vicinity of the toner layer control blade within the circle 305 indicated by the broken line, and white spots are generated. It is thought to be a factor that makes it difficult.

In this case, the resources cannot be effectively used and the global environment may be polluted. In other words, recycling this waste toner and reusing resources is an urgent task to protect the global environment.

In view of the above-mentioned problems, the present invention is intended to realize a high image density and a high image quality with a low background fog in a developing method which enables further downsizing, simplification, cost reduction and recycling of the apparatus. The present invention aims to provide a magnetic toner having high fluidity and high electrification property, and an electrophotographic method.

It is another object of the present invention to provide a magnetic toner and an electrophotographic method capable of preventing the occurrence of scratches on a photoconductor due to silica aggregates and further preventing filming on the photoconductor.

It is another object of the present invention to provide a magnetic toner and an electrophotographic method which do not reduce the charge amount and fluidity of the toner even when the waste toner is recycled, and do not generate aggregates.

It is another object of the present invention to provide a magnetic toner and an electrophotographic method which can extend the life of the magnetic toner, enable recycling development, prevent global environmental pollution and reuse resources.

[0034]

In order to solve the above-mentioned problems and to achieve the object, the present invention provides a magnetic toner of the present invention in which toner base particles composed of at least a binder resin and a magnetic substance are added as an external additive. The external addition treatment for mixing and adhering the mixture is performed by decompressing the inside of the mixing tank by using a mixing device composed of at least a mixing tank having a constant volume and a rotatable stirring blade that gives a shearing force to the powder. Characterize.

Further, in the image forming method of the present invention, the above-mentioned magnetic toner is used, and an electrostatic latent image holding member that moves while containing a fixed magnet therein, a toner hopper, a surface of the electrostatic latent image holding member, and a predetermined surface. The toner collecting electrode roller having a magnet inside is provided at a position having a gap, and after the electrostatic latent image is formed on the electrostatic latent image holder, the electrostatic latent image is positioned in the toner hopper. The magnetic toner is magnetically attracted to the surface of the holding body, the magnetic toner is carried on the surface of the electrostatic latent image holding body, and the electrostatic latent image holding body is moved to face the toner collecting electrode roller. Then, the magnetic toner remains on the image portion of the electrostatic latent image holding member, and the magnetic toner on the non-image portion is collected by the toner collecting electrode roller. The magnetic toner that visualizes the latent image is transferred onto the transfer paper by electrostatic force. A transfer step of transferring, a cleaning step of removing the magnetic toner partially remaining on the electrostatic latent image holder from the electrostatic latent image holder during the transfer step, and a magnetic toner removed by the cleaning step. And a toner recycling step of returning to the developing step again for reuse.

[0036]

The magnetic toner according to the present invention is mixed, kneaded, pulverized, externally added, and if necessary classified.

That is, the magnetic toner according to the present invention is subjected to an external additive treatment to the toner fine powder which has been pulverized or, if necessary, classified.

In the external addition process, a stirring blade for stirring the powder is provided in a mixing tank having a constant volume, and the pressure inside the mixing tank is reduced to perform the external addition process. A known method is used for the treatment for reducing the pressure.

Powder having a very low bulk density such as silica fine powder is difficult to apply stirring power, it is difficult to loosen agglomeration, and uniform mixing treatment cannot be performed. If the stirring strength is increased in order to strengthen the crushing of silica, extra stress is applied to the toner fine powder, the toner is fused to the stirring blade, or the toner is melted to generate a lump having a large particle size. If the strength is weakened, it is necessary to increase the processing time, which lowers the production efficiency.

By mixing under reduced pressure, the air in the powder layer is removed to increase the apparent specific gravity, and the shearing force required for mixing can be effectively applied. Therefore, the silica fine particles can be sufficiently crushed, and the fine toner particles having different specific gravities and the silica fine particles can be uniformly mixed.

As a result, it is possible to impart high charging characteristics and high fluidity characteristics to the toner.

The magnetic toner according to the present invention is preferably an insulating one-component toner. When the one-component toner is used, the mixing and stirring mechanism of the carrier and the toner, which is necessary in the two-component developing method, and the toner concentration control are unnecessary, so that the apparatus configuration can be simplified.

It has been found that when the magnetic toner according to the present invention is subjected to an external addition treatment under reduced pressure, a high charge amount is obtained and the generation of a reverse polarity toner is suppressed to an extremely low level. It is considered that this is because silica adheres uniformly to the toner surface and thus substantially covers the magnetic particles that affect the generation of the opposite polarity toner.

Therefore, it was found that a high image density was obtained, a clear image without toner scattering around the characters was obtained, and the effectiveness was extremely large.

If the fluidity of the toner is low, the toner in the non-image portion adheres strongly to the electrostatic latent image holding member and cannot be removed, resulting in background fog and degrading the image. It was also found that unevenness was generated in the solid black image area. When the amount of external additive silica is increased to improve the fluidity of the toner, the non-electrostatic adhesion of the toner to the electrostatic latent image holding member is reduced, the background fog is reduced, the image density is increased, and a solid black image is obtained. The unevenness of parts tends to be eliminated. However, problems such as filming of silica on the photoconductor and adhesion of white spots on the solid black image portion of silica aggregates have occurred.

By the way, in the electrophotographic method according to the present invention, since the toner is attached to the entire surface of the photosensitive member during development, the toner and the photosensitive member are in contact with each other longer than in the conventional one-component developing method. Therefore, the surface of the photoconductor is easily scratched and filming is likely to occur on the photoconductor. Further, since the transfer means is an elastic roller, which is in contact with the photoconductor, the photoconductor is more easily scratched. This is largely influenced by silica aggregates.

However, since the magnetic toner according to the present invention is subjected to the external addition treatment under reduced pressure, no silica aggregates are generated and the silica toner is uniformly attached to the toner surface. Therefore, the amount of floating silica is extremely smaller than that of the conventional toner, and there is no scratch or filming on the photoconductor.

The amount of silica added is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner. In order to prevent the aggregation of toner particles, an addition amount of 0.1 parts by weight or more is necessary, and if it is 5.0 parts by weight or more, floating silica increases. Although hydrophobic silica is used as the external additive in the present invention, other known inorganic or organic fine powder external additives may be used.

The magnetic toner according to the present invention has high fluidity. Furthermore, the adhesion state of silica is stable against the stress received in the developing device and from the cleaning blade, and there is no fluctuation in the fluidity and the amount of electrification, which is extremely stable.

Next, in the electrophotographic method according to the present invention, an electrostatic latent image holding member containing a fixed magnet is used, and magnetic toner is sprinkled on the electrostatic latent image holding member on which an electrostatic latent image is formed to magnetically magnetically. The toner is adhered and carried to the electrode roller portion, an AC bias is applied to the electrode roller, and the non-image portion toner of the electrostatic latent image holding member is removed by electrostatic force and magnetic force.

That is, the electrophotographic method presented in the present invention is one in which a magnet is installed inside the electrostatic latent image holding member in the cascade developing method, and an AC voltage is applied to the electrodes to further reduce the size and improve the performance.

In the present invention, the development is almost completed when the magnetic toner is first sprinkled on the electrostatic latent image carrier. The electrode roller part circulates the magnetic toner in the toner hopper and at the same time collects the toner in the non-image part of the electrostatic latent image. That is, it is the electrostatic latent image carrier that carries and carries the magnetic toner from the toner hopper to the developing section. The bare surface of the electrode roller, which does not carry the magnetic toner layer, faces the electrostatic latent image carrier. The electrode roller and the electrostatic latent image carrier rotate in opposite directions.

Further, in the electrophotographic method according to the present invention, the remaining magnetic toner transferred is recycled for development. The remaining magnetic toner transferred by a cleaning blade made of elastic urethane or the like is scraped off from the photosensitive drum to become waste toner. At this time, the toner is strongly stressed. At this time, the cleaning method is not limited to the elastic blade, but the same stress is applied to the method using a metal rigid roller, a fur brush, or the like. In order to stabilize the image quality even when the waste toner is recycled, it is necessary to maintain the high charge amount and high fluidity of the waste toner.

With the above-described structure, by using a magnetic toner having a high charge amount and a high fluidity, a developing method which enables further downsizing, simplification and cost reduction of the apparatus, and a high density and a low background fog can be obtained. Image quality can be realized. In addition, since the waste toner to be recycled can maintain high fluidity and high chargeability, it is possible to recycle the waste toner, and it is possible to prevent the global environmental pollution and to reuse resources by recycling without waste. A photographic method can be provided.

[0055]

EXAMPLES The magnetic toner according to the present invention comprises at least a binder resin, a magnetic material and an external additive.

The binder resin of the magnetic toner according to the present invention is a vinyl polymer obtained by polymerizing or copolymerizing vinyl monomers. Examples of the monomer styrene constituting the binder resin include styrene and its substitution products such as styrene, α-methylstyrene, and P-chlorostyrene, and examples of the acrylic acid alkyl ester include acrylic acid, methyl acrylate, and Examples of ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, isobutyl acrylate, hexyl acrylate, and alkyl methacrylate include, for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, methacrylic acid. Isobutyl, dodecyl methacrylate,
Examples include monocarboxylic acids having a double bond such as hexyl methacrylate and substituted products thereof.

As a method for producing these copolymers, known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization are adopted.

The copolymer used in the magnetic toner according to the present invention preferably contains a styrene component as a component in an amount of 50 to 95% by weight. If the proportion of styrene is less than 50% by weight, the melting characteristics of the toner will be poor, the fixability will be insufficient, and the pulverizability will be poor.

The magnetic toner according to the present invention contains the binder resin as a main component as described above. However, other known polymers or copolymers may be used, if necessary, in addition to such a main component. it can. For example, polyester resin,
Epoxy resin, polyurethane resin, etc. are available.

If necessary, other known external additives are added to the magnetic toner according to the present invention. As a preferable material for the external additive, known inorganic fine powder materials such as hydrophobic silica, titania, alumina, zirconia are used. For example, in the case of hydrophobic silica, hydrophilic silica obtained by treating silicon tetrachloride is further surface-treated to obtain hydrophobic silica. However, as a treating agent, dimethyldichlorosilane in consideration of negative electrification and hydrophobicity, Known treating agents such as hexamethylene disilazane and dimethyl siloxane are effective materials for hydrophobicity and negative charging.

Further, fine particles of polytetrafluoroethylene are added to the magnetic toner according to the present invention. Although it is effective in improving the cleaning property and preventing the filming of the photoconductor, it has been found that the effect is more strongly brought out by a small addition amount in the external addition treatment of the present invention.

If necessary, the magnetic toner according to the present invention may be mixed with an appropriate pigment or dye for the purpose of coloring and controlling charge. Examples of such pigments or dyes include carbon black, iron black, graphite, nigrosine, metal complexes of azo dyes, phthalocyanine blue, DuPont oil red, aniline blue, benzidine yellow, rose bengal and mixtures thereof. The required amount is blended.

Further, the magnetic toner according to the present invention may further contain a release agent such as WAX if necessary. Further, other types of additives can be blended if necessary. For example, it is a polishing agent such as tin oxide, strontium titanate, or tungsten carbide. Fine powder of an organic material is also added as needed for the purpose of fluidity aid, charging aid, cleaning aid and the like.

Further, the magnetic toner according to the present invention contains a magnetic material. Magnetic powders include iron, manganese, nickel,
Examples include metal powder such as cobalt and ferrite such as iron, manganese, nickel, cobalt, and zinc. The average particle size of the powder is preferably 1 μm or less, particularly preferably 0.6 μm or less. The addition amount is preferably 15 to 70% by weight. When the addition amount is 15% by weight or less, the toner scattering tends to increase, and when the addition amount is 70% by weight or more, the toner charge amount tends to decrease and the image quality tends to deteriorate.

The magnetic toner according to the present invention is manufactured by the following method.

The toner is mixed, kneaded, pulverized, externally added, and if necessary classified. Other methods such as a polymerization method may also be used.

The mixing treatment is a treatment in which the binder resin, the magnetic substance and other internal additives such as a charge control agent, a release agent and a pigment, which are added as necessary, are uniformly dispersed by a mixer equipped with stirring blades. A known processing method is used.

In the kneading process, the mixed material is heated to disperse the internal additive in the binder resin by shearing force. The kneading at this time can be performed using a known heating kneader. As the heating and kneading machine, it is possible to use an apparatus for heating a kneaded material such as a three-roll type, a single screw type, a twin screw type, a Banbury mixer type, and applying a shearing force to knead the mixture. The mass obtained by the kneading process is roughly crushed with a cutter mill or the like.

In the pulverization process, the pulverization is performed by a jet mill pulverizer or the like. Further, in the classification treatment, if necessary, fine powder particles are cut by an airflow classifier to obtain a desired particle size distribution. At this time, mechanical crushing and classification are also possible. For example, there is a method in which toner is charged into a minute gap between a fixed stator and a rotating roller and pulverized. Also in classification, there is a method of classifying by centrifugal force with a rotating roller. Known methods are used in both cases.

The magnetic toner according to the present invention is subjected to an external additive treatment to the toner fine powder which has been pulverized or, if necessary, classified.

The magnetic toner of each embodiment of the present invention will be described below with reference to the drawings.

(Example 1) (Table 1) shows the magnetic toner A of the present invention.
An example of the material composition of No. 1 is shown, and at least a binder resin,
A small amount of charge control agent composed of magnetic material and external additive,
Including a release agent.

[0073]

[Table 1]

The production of the magnetic toner of the present invention will be described. The mixture shown in (Table 1) was used as a Henschel mixer FM2.
Mix with OB (Mitsui Miike Co., Ltd.). The mixture is kneaded by heating with a twin-screw kneading extruder PCM30 (made by Ikegai Tekko Co., Ltd.).
The kneaded product is finely pulverized with a jet mill pulverizer IDS2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). The pulverized material is cut into fine powder with an airflow classifier DS2 (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). By the above treatment, particles having an average particle size of 8 μm were obtained. Then, the inorganic fine powder of hydrophobic silica was used as shown in FIG.
External mixing was carried out by mixing with an external mixing device shown in.

FIG. 1 is a sectional view showing a main part of an external addition mixing apparatus for producing a magnetic toner according to an embodiment of the present invention. Figure 1
In the above, 1 is a mixing tank having a constant volume, which is about 20H. Two
Is a stirring blade for stirring the powder, 3 is a motor for rotating the stirring blade 2, 4 is an air seal of the shaft portion, 5 is an oil diffusion vacuum pump, 6 is a filter, 7 is magnetic toner, and 8 is an air generator. is there. A vacuum pump 5 is connected to the upper part of the mixing tank 1 through a filter 6 to reduce the pressure.

The degree of vacuum is 2.66 × 10 ⁴ Pa or less, preferably
It is 1.33 × 10 ⁴ Pa or less. If the degree of vacuum is 2.66 × 10 ⁴ Pa or more, silica aggregates remain and sufficient toner characteristics cannot be obtained.

In this embodiment, the process is performed at about 1.33 × 10 ⁴ Pa.

FIG. 2 is a schematic sectional view of a magnetic toner according to an embodiment of the present invention. In FIG. 2, 21 is a binder resin,
22 is magnetic particles, 23 is a charge control agent, 24 is a release agent, and 25 is hydrophobic silica.

The physical property values of the magnetic toner A1 of the present invention are shown in (Table 2).
Shown in.

[0080]

[Table 2]

Fluidity was defined as static bulk density. For the measurement, a powder tester manufactured by Hosokawa Micron was used. The charge amount was measured by the blow-off method. The measurement conditions were such that a non-coated ferrite carrier was mixed at a toner concentration of 10%, put in a 100 ml polyethylene bottle, and stirred at a rotation speed of 60 rpm for 10 minutes.

It can be seen that the magnetic toner A1 clearly exhibits high fluidity and high chargeability.

FIG. 3 is a sectional view showing the main part of an electrophotographic apparatus in which the electrophotographic method of one embodiment of the present invention is used.
This developing method uses a one-component developing method. In FIG. 3, 101 is an organic photoconductor drum (hereinafter referred to as a photoconductor) in which phthalocyanine is dispersed in a polyester binder resin, 102 is a magnet fixed coaxially with the photoconductor 101, and 103 is negatively charged to the photoconductor 101. A corona charger, 104 is a grid electrode for controlling the charging potential of the photoconductor 101, and 105 is signal light. In each part of the configuration of the developing device for visualizing the latent image after exposure, 107 is a magnetic one-component toner (hereinafter referred to as magnetic toner), 106 is a magnetic toner 107 on the surface of the photoconductor 101.
Toner hopper for supplying the toner, 108 is a non-magnetic electrode roller (hereinafter referred to as an electrode roller) set by opening a gap with the photoconductor 101, 109 is a magnet installed inside the electrode roller 108, and 110 is a voltage applied to the electrode roller 108. AC high-voltage power supply for applying a voltage, 111 is a scraper made of polyester film for scraping off the toner on the electrode roller 108,
The excess toner in the non-image area 108 is collected.

Reference numeral 113 is a damper for smoothing the flow of the toner in the toner hopper 106 and for preventing the toner from being crushed by its own weight and clogged between the photosensitive member and the electrode roller.

Reference numeral 114 is a cleaning blade for scraping off the residual toner after transfer, 116 is a cleaning box for temporarily storing the residual toner, and 115 is a transport pipe for sending the residual toner to the toner hopper 106 of the developing device. It is a recycling process. The method of transportation may be a method of using air, a method of sending in a spiral shape, a method of magnetically or vibrating, but not limited thereto. An elastic urethane blade was used as the cleaning blade, but a fur brush to which a bias is applied or a conductive metal roller also produces the same result.

Here, the magnetic flux density on the surface of the photoconductor 101 is 600 Gs. The magnetic force inside the electrode roller 108 was made stronger to improve the transportability. The magnetic pole angle θ of the magnet 102 inside the photoconductor 101 shown in the figure was set to 15 degrees. The photoreceptor 101 has a diameter of 30 mm and is rotated at a peripheral speed of 60 mm / s in the direction of arrow A in FIG. Electrode roller 108 has a diameter of 16 mm and a peripheral speed of 40 mm
The photoconductor 101 was rotated at a speed of / s in the opposite direction (the direction of arrow B in the figure). The gap between the photoconductor 101 and the electrode roller 108 was set to 300 μm.

The photosensitive member 101 is connected to the corona charger 103 (applied voltage −
It was charged to -500 V at 4.5 kV and the voltage of the grid electrode 104 of -500 V). The photoconductor 101 was irradiated with the signal light 105 of the laser to form an electrostatic latent image. At this time, the exposure potential of the photoconductor 101 was -90V. Magnetic toner 107 was attached to the surface of the photoconductor 101 by a magnet in the toner hopper 106. Next, the photoconductor 101 was passed in front of the electrode roller 108.
When passing through the uncharged region of the photoconductor 101, a DC voltage of 0 V is superimposed on the electrode roller 108 by an AC high voltage power source 750.
An AC voltage (frequency 1 kHz) of V0-p (peak-to-peak 1.5 kV) was applied. After that, when passing through the photoconductor 101 charged with −500 V and having the electrostatic latent image written therein, the electrode roller 108 is used.
AC voltage of 750V0-p (peak-to-peak 1.5kV) superimposed with DC voltage of -350V by AC high voltage power supply 110
(Frequency 1 kHz) was applied. Then, the magnetic toner 107 attached to the charged portion of the photoconductor 101 is collected by the electrode roller 108,
The negative-positive inverted magnetic toner image of only the image portion remained on the photoconductor 101. Electrode roller 108 rotating in the direction of arrow B
The magnetic toner 107 attached to was scraped off by the scraper 111, returned to the inside of the toner hopper 106, and used for the next image formation. The toner image thus obtained on the photoconductor 101 is transferred onto a transfer sheet by the transfer charger 112, and then thermally fixed by a fixing device (not shown) to obtain a copied image.

Using the electrophotographic apparatus shown in FIG. 3, a copy test was conducted with the magnetic toner A1 of the present invention. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, an extremely high-resolution and high-quality image was obtained in which the horizontal black line was not disturbed and the toner was not scattered, and a 16 / mm image line having a uniform solid black image surface and a density of 1.4 was reproduced. A high density image with an image density of 1.4 or more was obtained. No background fog has occurred in the non-image area.

While recycling the waste toner,
A long-term copy test of 10,000 sheets was performed. The fluidity of the magnetic toner after 10,000 sheets did not decrease, a high charge amount was maintained, and filming did not occur on the photoconductor. Compared with the initial image, a high-density, low ground fog copy image was obtained. The recyclability of the magnetic toner was also excellent.

Table 3 shows the fluidity and image density of the magnetic toner at the initial stage and after the 10,000-sheet copying test.

[0091]

[Table 3]

It can be seen that the toner A1 shows stable characteristics with little change in fluidity (static bulk density) and image density.

(Example 2) (Table 4) shows the magnetic toner A of the present invention.
An example of the material composition of No. 2 is shown, which is different from the example (Table 1) in that the external additive contains polytetofluoroethylene fine particles.

[0094]

[Table 4]

A copying test was conducted with the magnetic toner A2 of the present invention using the electrophotographic apparatus shown in FIG. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, an extremely high-resolution and high-quality image was obtained in which the horizontal black line was not disturbed and the toner did not scatter, and the solid black image was uniform and the density of 1.4 lines / mm was reproduced. A high density image with an image density of 1.4 or more was obtained. No background fog has occurred in the non-image area.

While recycling the waste toner,
A long-term copy test of 10,000 sheets was performed. The fluidity of the toner after 10,000 sheets did not decrease, a high charge amount was maintained, and filming did not occur on the photoconductor. Compared with the initial image, a high-density, low ground fog copy image was obtained. The recyclability of the magnetic toner was also excellent.

(Comparative Example 1) A magnetic toner B1 was produced as a trial with the same composition and formulation as in Example 1 except that the external addition treatment was carried out at normal pressure.

It can be seen that the magnetic toner B1 exhibits low fluidity and low charge amount.

Using the electrophotographic apparatus shown in FIG. 3, a copy test was conducted with magnetic toner B1. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, a large amount of toner was scattered, uneven solid black images were generated, low image densities, large background fog, and practical images could not be obtained.

In the long-term copying test, the fluidity of the toner was remarkably lowered, the image density was lowered, and the background fog in the non-image area was increased. In addition, the occurrence of scratches on the photoreceptor is significant,
In addition, filming also occurred, and a practical image could not be obtained.

The fluidity and image density of the toner at the initial stage and after the 10,000-sheet copying test are shown in (Table 3). It can be seen that both fluidity and image density have deteriorated.

Comparative Example 2 A toner was experimentally manufactured with the same composition as in Example 1 except that the addition amount of the magnetic material was 10% by weight. Due to the large amount of toner scattering, practical characteristics could not be obtained.

(Comparative Example 3) A toner was experimentally prepared with the same composition as in Example 1 except that the amount of the magnetic material added was 80% by weight. The amount of electrification was low, there was a lot of background fog, and practical characteristics could not be obtained.

[0104]

As described above, when the magnetic toner of the present invention is mixed under reduced pressure, air in the powder layer is removed so that the apparent specific gravity is increased and the shearing force required for mixing is effective. Can be given to. Therefore, the silica fine particles can be sufficiently crushed, and the fine toner particles having different specific gravities and the silica fine particles can be uniformly mixed. As a result, it is possible to impart high charging characteristics and high fluidity characteristics to the toner.

In the electrophotographic method of the present invention, the above-mentioned magnetic toner is used, and an electrostatic latent image holding member that moves by enclosing a fixed magnet is provided, and a predetermined gap is provided between the surface of the electrostatic latent image holding member. , Which has a developing process consisting of an electrode roller having an electrode roller having a magnet inside, a cleaning process, and a waste toner recycling process, has high density, low background fogging in a high performance, small size and low cost developing method. High image quality can be achieved.

Further, the recycling of waste toner does not lower the image density, the filming of the photoconductor does not occur, and the life of the photoconductor is prolonged. By reuse, it is possible to prevent global environmental pollution and reuse resources.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of an external addition mixing device for producing a magnetic toner according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a magnetic toner according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of an electrophotographic apparatus in which an electrophotographic method according to an embodiment of the present invention is used.

FIG. 4 is a schematic view of a conventional developing device.

FIG. 5 is a schematic view of a conventional developing device.

[Explanation of symbols]

1 ... Mixing tank, 2 ... Stirring blade, 3 ... Motor, 4 ... Air seal, 5 ... Vacuum pump, 6 filter, 7,
107 ... Magnetic toner, 8 ... Air generator, 21 ... Binder resin, 22 ... Magnetic particles, 23 ... Charge control agent, 24 ... Release agent, 25 ... Hydrophobic silica, 101 ... Organic photosensitive drum, 102 ... Fixed magnet embedded in the organic photoconductor drum, 103 ... Corona charger, 104 ... Grid electrode, 10
6 ... Toner hopper, 108 ... Non-magnetic electrode roller, 109
… Magnets installed inside non-magnetic electrode rollers, 111… scrapers, 114… cleaning blades, 115… waste toner recycling transport pipes, 116… cleaning boxes.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03G 15/08 111 15/09 101 21/10 G03G 9/08 375 381 6605-2H 21/00 310 6605-2H 326

Claims (11)

[Claims] 1. The magnetic toner comprises an external additive treatment in which an external additive is mixed and attached to toner base particles composed of at least a binder resin and a magnetic material, and a mixing tank of at least a fixed volume is provided.
A magnetic toner characterized by being formed by decompressing the inside of the mixing tank using a mixing device composed of a rotatable stirring blade that gives a shearing force to powder. 2. The magnetic toner according to claim 1, wherein the pressure in the mixing tank is 2.66 × 10 ⁴ Pa or less and externally added. 3. The magnetic toner according to claim 1, wherein the amount of the magnetic material added is 15 to 70% by weight based on the weight of the magnetic toner. 4. The magnetic toner according to claim 1, wherein the external additive is composed of at least silicon dioxide fine particles. 5. The magnetic toner according to claim 1, wherein the external additive is composed of at least polytetrafluoroethylene fine particles. 6. The magnetic toner according to claim 1, wherein the magnetic toner is a one-component toner. 7. An electrostatic latent image holder that includes a fixed magnet and moves, a toner hopper, and a toner recovery member that has a magnet inside at a position having a predetermined gap from the surface of the electrostatic latent image holder. An electrode roller is provided, and after forming an electrostatic latent image on the electrostatic latent image holder, the magnetic toner is magnetically attracted to the surface of the electrostatic latent image holder located in the toner hopper. , The magnetic toner is carried on the surface of the electrostatic latent image holder, the electrostatic latent image holder is moved to face the toner recovery electrode roller, and the magnetic image is formed on the image portion of the electrostatic latent image holder. A developing process in which the toner is left and the magnetic toner in the non-image area is collected by the toner collecting electrode roller, and the magnetic toner that visualizes the electrostatic latent image on the electrostatic latent image holder is electrostatically charged. Transfer step of transferring the electrostatic latent image A cleaning step of removing the magnetic toner remaining on the holding member from the electrostatic latent image holding member; and a toner recycling step of returning the magnetic toner removed in the cleaning step to the developing step for reuse. An electrophotographic method characterized by: 8. An external additive treatment for mixing and adhering an external additive to toner base particles composed of at least a binder resin and a magnetic material is at least a mixing tank of a constant volume and a rotation for applying a shearing force to the powder. 8. The electrophotographic method according to claim 7, wherein the magnetic toner according to claim 1 is used by reducing the pressure in the mixing tank by using a mixing device including a possible stirring blade. 9. The electrophotographic method according to claim 7, wherein in the cleaning step, the cleaning means is an elastic urethane blade. 10. The electrophotographic method according to claim 7, wherein in the cleaning step, the cleaning means is a fur brush to which a bias is applied. 11. The electrophotographic method according to claim 7, wherein in the cleaning step, the cleaning means is a conductive metal roller to which a bias is applied.