JPH07271090A - Magnetic toner, its production and electrophotographic method - Google Patents

Abstract

PURPOSE:To provide a magnetic toner capable of realizing the high picture quality of high picture density and low surface fogging over a long period. CONSTITUTION:An external additive contg. a fine silica particle 35 and a lubricative org. fine particle 36 is fixed on the surface of the globurized powder of a magnetic toner base body contg. at least a binder resin 31 and a magnetic substance particle 32 to constitute a magnetic toner. A bright image enhanced in charge amt., fluidity and concn. and without the toner being scattered around a character is obtained by this toner. Since the silica and org. fine particle are fixed on the toner base body, the adhesion of the silica and org. fine particle are fixed to the toner base body, the adhesion of the silica and org. fine particle is stable to the stress from the inside of a developing device and a cleaning blade as compared with the case when the additive is simply added, the fluidity and charge amt. are not fluctuated, the silica and org. particle are not liberated even after long continuous use, and the toner filming of the photoreceptor, the aggregation of the org. particles and the picture flowing are suppressed.

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 a copying machine, a printer or a facsimile, a method for producing the magnetic toner, and an electrophotographic method using the magnetic toner, and more particularly to realizing high image quality.

[0002]

2. Description of the Related Art In an electrophotographic copying machine or printer, printing is performed by the following process. First, an electrostatic latent image carrier (hereinafter referred to as a photoconductor) is charged for image formation. After charging the photoconductor, in the case of a copying machine, the copy original is irradiated with light and reflected light is applied to the photoconductor through a lens system. Further, in the case of a printer, an image signal is sent to a light emitting diode or a laser diode as an exposure light source, and a latent image is formed on the photoconductor by turning on / off the light. When a latent image (high and low surface potential) is formed on the photoconductor, the photoconductor is visualized with toner (having a diameter of about 5 μm to 15 μm) which is precharged colored powder. The toner adheres to the surface of the photoconductor according to the level of the surface potential of the photoconductor, and is then electrically transferred to the copy paper. That is, the toner is previously charged positively or negatively,
A charge having a polarity opposite to that of the toner is applied from the back surface of the copy sheet and electrically attracted. At the time of transfer, not all the toner on the photoconductor is transferred to the copy sheet, but a part of the toner remains on the photoconductor. This residual toner is scraped off by a cleaning blade or the like in the cleaning section to become waste toner.

Conventionally, a cascade developing method, a touch-down developing method, a jumping developing method and the like are known as developing methods for making an electrostatic latent image visible by an electrophotographic method. Among them, the cascade developing method is the first developing method used in a practical copying machine of an electrophotographic method, in which a developer is directly sprinkled on a photoconductor, and is shown in US Pat. No. 3,105,770. The touch-down developing method is a method in which an AC bias is applied to a developing roller to cause a single-component toner to fly and develop, and is disclosed in US Pat. No. 3,866,574.
In this invention, the AC bias applied to the developing roller is
It is used for the purpose of activating the movement of the toner, and it is explained that the toner flies to the image portion and returns to the middle in the non-image portion.

Further, as an improved technique for applying the AC bias, there is a jumping development disclosed in Japanese Patent Publication No. 63-42256. In this jumping development 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 regulating blade regulates the toner in a thin layer and conveys it to the developing portion, where the toner is attached to the image portion of the photoconductor by an AC bias. The technical idea of 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 generally contains 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. Containing fine particles. As the resin component, a natural or synthetic resin may be used alone or in an appropriate mixture.
Further, it is also practiced to use silicon dioxide particles (hereinafter referred to as silica) in order to enhance fluidization of the toner and organic fine particles as an external additive in order to enhance cleaning property of the surface of the photoconductor. . This silica is subjected to a hydrophobic treatment by a coupling treatment in advance so that it does not absorb the moisture at high humidity and impair the fluidity and chargeability of the toner.

In recent years, there has been a demand for ever higher quality of copied images and long-term stability of image quality. In order to meet such demand, the particle size of the toner is further reduced, and the charging property and stability are higher than ever before. Is required.

[0007]

However, with the conventional toner, a so-called toner filming phenomenon may occur in which the toner adheres to the surface of the photosensitive member while printing is repeated. It is considered that this is because when silica added as an external additive adheres to the surface of the photoconductor, it is difficult to remove it, which triggers and the toner begins to adhere to that part. This toner filming is more likely to occur because the smaller the toner particle size, the greater the adhesion to the photoconductor. When the toner adheres to the surface of the photoconductor, the light is blocked when the image pattern is exposed, an electrostatic latent image is not formed, and white spots occur in reversal development, resulting in an image defect.

When organic fine particles are added to the toner base in order to improve the cleaning property of the surface of the photoconductor, the organic fine particles, which are released from the toner during continuous use, are aggregated in the cleaning portion, which is effective at the initial stage. The cleaning effect is reduced, resulting in an image defect.

As for the developing method, which is well known in this technical field, the cascade developing method is not good at reproducing solid images, and has a problem that the apparatus becomes large and complicated. Was. Further, the developing device of U.S. Pat. No. 3,866,574 has a problem that the device is required to have high accuracy, is complicated, and is expensive. In the jumping development method, it was essential to form a very uniform thin layer on the toner carrier carrying the toner layer. Further, in this method, so-called sleeve ghost development occurs in which the history of the previous image often remains in the toner thin layer on the toner carrier and the afterimage appears in the image. Further, there is a drawback that the device is complicated and the cost is high.

Therefore, we have developed a new electrophotographic method capable of realizing a smaller size and higher performance of development (Japanese Patent Laid-Open No. 5-7289).
No. 0) is proposed. The development method of this electrophotographic method is
The configuration is such that the unnecessary toner in the non-image portion is removed by a photoconductor containing a fixed magnet and a toner recovery electrode roller (hereinafter referred to as an electrode roller) having a magnet facing the photoconductor with a predetermined gap. This developing method is a method that faithfully reproduces a solid image, does not cause a sleeve ghost, and enables further downsizing, simplification, and cost reduction of the apparatus.

However, in order to obtain high image quality by using this developing method, higher performance toner characteristics are required.

This is because the developing method does not use a regulating blade for regulating the toner in a thin layer, so that 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. To be done. Therefore, there are few places and spaces for the toner to be triboelectrically charged to obtain a desired amount of charge, and therefore the toner requires higher charging characteristics and higher flow characteristics than ever before. At the fluidity level of the toner used in the conventional two-component development method using two components of toner and carrier and the one-component development method of developing with one-component magnetic toner, solid black image areas and halftone images Unevenness occurs in the areas, and the background fog increases in the non-image areas. Such a phenomenon remarkably appears in a toner having low fluidity, but this is because a toner having low fluidity cannot obtain a sufficient triboelectric charge amount because the probability of contact with a developing member is low.
This is because the triboelectric chargeability varies among the toners, and uniform toner chargeability cannot be obtained.

The fluidity of the toner decreases as the particle size of the toner decreases. In order to increase the fluidity of the toner, conventionally, a means for increasing the addition amount of an external additive such as silica which is a fluidity imparting agent has been taken (Japanese Patent Publication No. 54-16219).
Issue). 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. Further, as an adverse effect when the amount of silica is increased, suspended matter of silica increases, and this silica is pushed into the photoconductor by the pressing force of the cleaning blade, and the photoconductor is scratched.
As a result, silica and toner tend to adhere to the photoconductor, and the toner filming described above frequently occurs.

The present invention solves these conventional problems, and by applying it to the newly developed developing method described above, it is possible to realize high image density and high image quality with low ground fog for a long period of time. An object of the present invention is to provide a toner, a method for producing the toner, and an electrophotographic method using the toner.

[0015]

Therefore, in the present invention, the surface of the spherical powder of the magnetic toner matrix containing at least the binder resin and the magnetic particles contains the hydrophobic silicon dioxide particles and the organic particles. An external additive is fixed to form a magnetic toner.

The amount of the magnetic particles added is set to 15 to 70% by weight of the weight of the magnetic toner base.

The addition amount of the hydrophobic silicon dioxide fine particles is 0.1 to 100 parts by weight of the magnetic toner base material.
It is set to 5.0 parts by weight.

The specific surface area of the hydrophobic silicon dioxide fine particles is set to 50 to 300 m ² / g.

The amount of organic fine particles added is set to 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner base.

Further, the specific surface area of the organic fine particles is 2 to
It is set to 25 m ² / g.

Further, the powder of the magnetic toner base containing at least the binder resin and the magnetic particles and the external additive containing the hydrophobic silicon dioxide fine particles and the organic fine particles are mixed to form a powder on the surface of the magnetic toner base powder. After attaching the external additive, the magnetic toner base powder is dispersed and jetted in a hot air stream to melt the surface of the magnetic toner base powder, and the external additive is fixed to the surface of the magnetic toner base powder, and at the same time, magnetic Magnetic toner is manufactured by spheroidizing toner base powder.

Further, the temperature of the hot air stream is set to 100 to 60.
It is set to 0 degrees.

The amount of the magnetic particles added when the magnetic toner is manufactured by such a method is set to 15 to 70% by weight with respect to the weight of the magnetic toner matrix.

Further, the amount of the hydrophobic silicon dioxide fine particles added when the magnetic toner is manufactured by such a method is set to 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner base.

The hydrophobic silicon dioxide fine particles used in the production of the magnetic toner by such a method have a specific surface area of 5
The thing of 0-300 m < ² > / g is used.

In addition, when the magnetic toner is manufactured by such a method, the amount of the organic fine particles added is determined by the magnetic toner base 100.
It is set to 0.01 to 3.0 parts by weight with respect to parts by weight. Further, fine particles having a specific surface area of ² to 25 m ² / g are used as the organic fine particles when the magnetic toner is manufactured by such a method.

Further, in the electrophotographic method using a one-component magnetic toner, hydrophobic silicon dioxide fine particles and organic fine particles are formed on the surface of a spherical toner powder of a magnetic toner matrix containing a binder resin and magnetic particles as the magnetic toner. Using a magnetic toner with fixed external additives, magnetically attach this magnetic toner to the photoconductor, rotate the photoconductor, carry the attached magnetic toner to the collection unit, and face the photoconductor. An electrostatic force and a magnetic force are applied to the arranged electrode roller to collect the magnetic toner attached to the non-image portion of the photoconductor.

The amount of the magnetic particles added to the magnetic toner used in this electrophotographic method is set to 15 to 70% by weight based on the weight of the magnetic toner base.

The amount of the hydrophobic silicon dioxide fine particles added to the magnetic toner used in this electrophotographic method is set to 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner base. .

The hydrophobic silicon dioxide fine particles of the magnetic toner used in this electrophotographic method have a specific surface area of 50.
˜300 m ² / g is used.

The amount of organic fine particles added to the magnetic toner used in this electrophotographic method is set to 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner base.

Further, the organic fine particles of the magnetic toner used in this electrophotographic method have a specific surface area of ² to 25 m ² /
The thing of g is used.

[0033]

In the magnetic toner of the present invention, silica having a high negative charging property and organic fine particles having a lubricating property are fixed on the surface of the magnetic toner base powder, and the toner shape is formed into a substantially spherical shape. Both the amount and the fluidity are high, the generation of the reverse polarity toner can be suppressed to an extremely low level, and it is possible to obtain a high density and clear image without scattering of the toner around the characters.

Further, the cleaning blade made of urethane or the like is hard in the environment of low temperature and low humidity, so that the cleaning property is deteriorated or the mounting state of the cleaning blade varies, Although cleaning may be incomplete and toner filming may occur, the organic fine particles having lubricity have a function of assisting the cleaning performance, and the residual toner adhering to the photoconductor can be removed cleanly.

In the magnetic toner of the present invention, since these silica and organic fine particles are fixed to the toner base, silica and organic particles are more resistant to the stress received from the inside of the developing device and the cleaning blade than when they are simply added. The adhered state of the organic fine particles is stable, and the fluidity and charge amount do not fluctuate. For this reason, silica and organic fine particles are not released even after continuous use for a long period of time, and toner filming of the photoconductor, aggregation of organic fine particles, and image deletion are suppressed.

The amount of the magnetic powder added to the magnetic toner is preferably 15 to 70% by weight. 15% by weight
Below, the toner scattering increases, and above 70% by weight, the toner charge amount decreases.

The amount of silica added is 10 for the magnetic toner base material.
0.1 to 5.0 parts by weight is preferable with respect to 0 parts by weight.
If it is 0.1 part by weight or less, the fluidity of the toner cannot be obtained, and if it is 5.0 parts by weight or more, floating silica increases and white spots are generated on the image.

The amount of the organic fine particles added is preferably 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner base. If it is 0.01 part by weight or less, the effect of adding the organic fine particles cannot be obtained, and if it is 3.0 parts by weight or more, uniform mixing with the toner cannot be performed, and an image defect of white spots appears on the image.

The specific surface area of silica is 50 to 300.
It is preferably m ² / g. When the specific surface area is 50 m ² / g or less, the particle size becomes large, and it becomes difficult to uniformly mix with the toner, and high fluidity cannot be obtained. Specific surface area is 300m
^{When the amount is 2} / g or more, the cohesiveness of silica becomes strong, the silica does not adhere uniformly to the toner base, and the amount of floating silica increases, resulting in toner filming.

The specific surface area of the organic fine particles is ^{2 to} 25 m ² /
g is preferred. If the specific surface area is 25 m ² / g or more, the cleaning effect cannot be obtained. If the specific surface area is less than 2 m ² / g, it will not be uniformly mixed with the toner.

In order to produce this magnetic toner, the magnetic toner base powder to which the external additive is attached is dispersed and sprayed in a hot air stream, and the surface of the toner particles is melted, and the silica and the organic fine powder are instantly fixed and the magnetic property is improved. Body coating and spheronization of the toner particles are performed.

At this time, the hot air temperature is from 100 degrees to 600 degrees.
Degree is preferred. If it is 100 degrees or less, the surface modification effect of the magnetic toner base cannot be obtained, and if it is 600 degrees or more, aggregation of the toner and deterioration of the toner material are likely to occur.

Further, since the electrophotographic method of the present invention has a simple structure, the magnetic toner is less likely to be charged and it is difficult to obtain high charging characteristics. Further, since the toner and the photoconductor are in long contact during development, the surface of the photoconductor is easily scratched, and toner filming is likely to occur on the photoconductor. However, since the above-mentioned magnetic toner having a high fluidity and a high charge amount is used as the magnetic toner, such a point can be covered, and a clear and high-quality image can be obtained for a long period of time.

[0044]

EXAMPLES First, the electrophotographic method carried out in the present invention will be explained. FIG. 3 schematically shows an apparatus for carrying out the electrophotographic method of the present invention. As the developing method, a one-component developing method in which only one component of magnetic toner is used for development is used. This apparatus includes a photoconductor 1 that rotates in one direction, a magnet 2 that is fixed coaxially with the photoconductor 1, a corona charger 3 that negatively charges the photoconductor 1, and a grid that controls the charging potential of the photoconductor. The photoconductor 1 is exposed to the signal light 5 to form a latent image.

Further, as a developing mechanism for visualizing the latent image after exposure, a toner hopper 6 for supplying the magnetic toner 7 to the surface of the photoconductor 1 and a nonmagnetic set with a gap with the photoconductor 1 are set. An electrode roller 8, a magnet 9 installed inside the electrode roller 8, an AC high-voltage power supply 10 for applying a voltage to the electrode roller 8, and a scraper 11 made of a polyester film for scraping off the toner on the electrode roller are provided. The excess toner adhering to the non-image portion of the photoconductor 1 is collected by the electrode roller 8. The numeral 16 smoothes the flow of the toner 7 in the toner hopper 6 and prevents the toner 7 from being crushed by its own weight and causing clogging between the photoconductor 1 and the electrode roller 8. It is a damper for.

In addition, the apparatus further comprises a transfer charger 12 for transferring the toner image 7 on the photoconductor 1 onto a transfer sheet, a fixing device (not shown) for fixing the transferred image, and the photoconductor 1 And a cleaning unit for scraping off the residual toner adhering to the surface with a cleaning blade.

Due to the magnetic force of the magnet 2, a magnetic field having a magnetic flux density of 600 Gs is formed on the surface of the photoconductor 1. By enhancing the magnetic force inside the electrode roller 8, the transportability in the recovery of toner is improved. The magnetic pole angle θ of the magnet 2 shown in the figure is set to 15 degrees. The photoconductor 1 has a diameter of 30 mm and is rotated at a peripheral speed of 60 mm / s in the direction of the arrow in the drawing. The diameter of the electrode roller 8 is 16 mm
At the peripheral speed of 40 mm / s, the photoconductor 1 is rotated in the direction opposite to the traveling direction (the direction of the arrow in the drawing). The gap between the photoconductor 1 and the electrode roller 8 is set to 300 μm.

The photoconductor 1 is connected to the corona charger 3 (applied voltage-
4.5kV, voltage of grid 4 -500V), -50
The photoreceptor 1 is charged to 0 V and the laser beam 5 is irradiated on the photoreceptor 1 to form an electrostatic latent image. The exposure potential of the photoconductor at this time is -9.
It is 0V. A toner hopper 6 is provided on the surface of the photoconductor 1.
The toner 7 is attached by the magnetic force of the magnet 2 in the process of rotating in contact with. Next, the photoconductor 1 passes in front of the electrode roller 8.

When passing through the uncharged area of the photoconductor 1, the electrode roller 8 is superposed with a DC voltage of 0V by the AC high-voltage power source 10 at 750V _0-p (peak-to-peak 1.5.
AC voltage (frequency 1 kHz) of kV) is applied,
When passing through the photoconductor 1 charged with −500V and having an electrostatic latent image written thereon, the AC high voltage power source 10 superimposes a DC voltage of −350V on 750V _0-p (peak-to-peak).
An alternating voltage (frequency 1 kHz) of 1.5 kV) is applied. By this application, the toner attached to the non-image portion of the charged portion of the photoconductor 1 is collected by the electrode roller 8, and a negative-positive inverted toner image of only the image portion remains on the photoconductor 1. The toner adhering to the electrode roller 8 rotating in the direction of the arrow is scraped off by the scraper 11 and again the toner hopper 6
It is put back in and used for the next imaging.

The toner image thus obtained on the photosensitive member 1 is transferred onto the transfer paper by the corona transfer 12 and then heat-fixed by a fixing device (not shown) to form a copy image. The residual toner remaining on the photoconductor is scraped off by a cleaning blade or the like in the cleaning section to become waste toner.

As described above, in this developing step, an electrostatic latent image is formed on the photoconductor 1 containing the fixed magnet 2, toner 7 is sprinkled on the electrostatic latent image and magnetically adhered thereto, and in that state, the electrode roller 8 is formed. The toner is carried and conveyed to a collecting portion opposite to, and an AC bias is applied to the electrode roller 8 to remove the non-image portion toner on the photoconductor 1 by electrostatic force and magnetic force. Therefore, this electrophotographic method is further miniaturized and has higher performance by adding to the cascade development method a configuration in which a magnet is installed inside the photoconductor and a configuration in which an AC voltage is applied to the electrodes.

In this electrophotographic method, the development is almost completed when the toner 7 is first sprinkled on the photosensitive member 1. It is the photoconductor 1 that carries and carries the toner from the toner hopper 6 to the collecting portion, and the electrode roller portion 8 functions to collect the toner in the non-image portion of the electrostatic latent image and circulate the toner 7 in the toner retainer. Are doing A bare surface of the electrode roller 8 which does not carry a toner layer faces the photoconductor 1. The electrode roller 8 and the photoconductor 1 are rotating in opposite directions. Therefore, even if foreign matter is accidentally mixed in the collecting field where the photoconductor 1 and the electrode roller 8 face each other or the toner is aggregated, It is immediately removed due to rotation.

Since the developing method by the electrophotographic method has a simple structure, there are few toner charging opportunities,
It is difficult to obtain high charging characteristics. When the charge amount of the toner is reduced, the mirror image force with the photoconductor is weakened, the toner attached to the photoconductor is easily removed by the magnetic force of the magnet 9, and the image density is lowered. Further, it has been found that the toner scattering around the characters is increased and the sharpness of the image is deteriorated. Also, if the toner has low fluidity, the background fog may increase,
Unevenness occurs in a solid black image or a halftone image part.

Further, since the toner adheres 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 photosensitive member is easily scratched, Toner filming easily occurs on the photoconductor.

In the present invention, such a point is prevented by using the improved magnetic toner.

This magnetic toner is manufactured by the steps of mixing of materials, kneading, pulverization, external addition treatment, surface modification treatment, and (if necessary) classification treatment.

In the present invention, an insulating one-component toner is used as the magnetic toner. In the case of one component toner,
This is because the mixing and stirring mechanism of the carrier and the toner, which is necessary for the two-component development, and the toner concentration control are unnecessary, and the configuration of the apparatus can be simplified.

In the material of the magnetic toner, the toner base is composed of a binder resin, magnetic powder, and additives (internal additives) such as a charge control agent and a release agent, and an external additive surrounding the surface of the toner base particles. Is composed of silica and organic fine particles.

As the binder resin, a vinyl polymer obtained by polymerizing or copolymerizing vinyl monomers such as styrene, alkyl acrylate and alkyl methacrylate can be used. Examples of the monomer styrene constituting the binder resin include styrene, α-methylstyrene,
There are styrenes such as P-chlorostyrene and its substitution products, and examples of alkyl acrylates include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, isobutyl acrylate, and acrylic. There is hexyl acid, and examples of the methacrylic acid alkyl ester include a double bond such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, isobutyl methacrylate, dodecyl methacrylate, and hexyl methacrylate. There are carboxylic acids and their substitution products.

When this copolymer is used, it is preferable that the styrene component is contained in an amount of 50 to 95% by weight. When the proportion of styrene is less than 50% by weight, the melting property of the toner in the surface modification treatment described later is poor, the fixability of the external additive becomes insufficient, and the pulverizability deteriorates.

For the production of these copolymers, bulk polymerization,
Known polymerization methods such as solution polymerization, suspension polymerization and emulsion polymerization are used.

In addition to the above components, other known polymers or copolymers such as polyester resins, epoxy resins, polyurethane resins, etc. may be used as the binder resin, if necessary. You can also

As the magnetic powder, metal powder such as iron, manganese, nickel and cobalt, and ferrite powder such as iron, manganese, nickel, cobalt and zinc are used. The average particle size of the powder is preferably 1 μm or less, and particularly preferably 0.6 μm or less.

If necessary, a suitable pigment or dye is added to the internal additive for the purpose of coloring or controlling charge. As the pigment or dye, carbon black, iron black, graphite, nigrosine, a metal complex of azo dye, phthalocyanine blue, DuPont oil red, aniline blue,
Benzidine yellow, rose bengal, or a mixture of these can be used, and these are blended in an amount required for charge and coloring.

As the internal additive, further, if necessary,
A release agent such as WAX, an abrasive such as tin oxide, strontium titanate, barium titanate, or tungsten carbide, a fluidity aid made of fine powder of an organic material, a charging aid, a cleaning aid, etc. may be included. it can.

As the external additive, silica subjected to a hydrophobizing treatment (hydrophobic silica) and organic fine particles are added. By adding silica having high negative chargeability to the magnetic toner, a high charge amount and high fluidity of the toner are secured, and generation of reverse polarity toner is suppressed to an extremely low level. Therefore, a clear image with high image density and no toner scattering around the characters can be obtained.

The hydrophobizing treatment of silica is carried out by a known coupling treatment using a treating agent such as dimethyldichlorosilane, hexamethylenedisilazane and octylsilane.

The organic fine particles increase the lubricity of the toner and promote the cleaning action for removing the residual toner from the photoconductor. When using urethane etc. as the cleaning blade, the blade becomes hard in a low temperature and low humidity environment and the cleaning property deteriorates, and the residual toner is not completely removed even when the mounting state of the cleaning blade varies. However, toner filming easily occurs, but such a situation can be avoided by adding organic fine particles. It has been found that the organic fine particles have a function of widening the permissible range for obtaining a clear image as described above, and are very effective particularly against environmental changes.

As the organic fine particles, known fine particles having lubricity, for example, fine particles of polytetrafluoroethylene, polyvinylidene fluoride, polyester, polymethylmethacrylate, styrene-acrylic copolymer, polyethylene and the like can be used. Among them, polytetrafluoroethylene and polyvinylidene fluoride are preferable.

As the external additive, other known external additives, for example, known inorganic fine powder materials such as titania, alumina and zirconia can be used if necessary.

The mixing treatment is carried out by uniformly dispersing the binder resin, the magnetic powder, and other optional additives such as a charge control agent, a release agent, and an internal additive such as a pigment by a mixer equipped with a stirring blade. In the examples, the materials shown in (Table 1) are used as the toner base composition (the composition before the external additive is externally added), and this mixture is used as a Henschel mixer FM-2.
0B (manufactured by Mitsui Miike Kakoki Co., Ltd.).

[Table 1] In the kneading process, the mixed materials are heated to disperse the internal additive in the binder resin by shearing force.For this kneading, three roll type, single screw type, twin screw type, Banbury type are used. A known heat kneader such as a mixer type can be used. In the embodiment, a twin-screw kneading extruder P
The mixture is heated and kneaded using CM-30 (manufactured by Ikegai Tekko KK).

Next, the mass obtained by the kneading process is roughly crushed by a cutter mill or the like and then finely crushed. A jet mill pulverizer or the like is used for this fine pulverization treatment, and further, if necessary, classification treatment is performed using an airflow classifier to cut fine powder particles to obtain a desired particle size distribution. Further, for this fine pulverization, a mechanical system in which the toner is put into a fine gap between a fixed stator and a rotating roller and pulverized can be used. For classification, centrifugal force of a rotating rotor is used. It is also possible to use mechanical classification methods. In the examples, the kneaded product was finely pulverized with a jet mill pulverizer IDS-2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and the pulverized product was then subjected to an air flow classifier DS-2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). After classification, the fine powder was cut to form toner particles having an average particle diameter of 8 μm. The toner obtained at this stage is called a toner base to distinguish it from the finished toner.

The external additive treatment is a treatment in which silica and organic fine particles are added as an external additive to the toner base, and these are mixed by a mixer or the like. In the embodiment, this mixture is mixed with Henschel mixer FM-20B (Mitsui Miike Kako Co., Ltd.). (Manufactured by Kikisha).

In the surface modification treatment, the toner base material subjected to the external addition treatment is exposed to hot air to modify the surface thereof. In the embodiment, therefore, the magnetic toner base material to which the external additive is attached is heated in a hot air stream. It is dispersed and sprayed inside. By this treatment, the surface of the toner particles is melted, silica and the organic fine powder are instantly fixed to the toner base, and at the same time, the magnetic particles are coated and the toner particles are deformed into a spherical shape. As a surface modification method using hot air, there is a method of supplying toner into the circulating hot air.
This method is not preferable because the aggregation of toner particles is unavoidable and the particle size distribution changes. On the other hand, in the method of the embodiment, the toner particles are instantly dispersed in the hot air and modified, so that stable treatment is performed without the occurrence of aggregation.

FIG. 2 shows an apparatus for performing this surface modification treatment. Magnetic toner 21 after external addition processing
It is injected at a speed of 1 kg / h from 22 and is sent to the dispersion nozzle 24 by the compressed air 23, from which it is dispersed and jetted. The compressed air pressure was set to 0.5 kg / cm ² . In order to uniformly jet the magnetic toner into the hot air stream 25, two dispersion nozzles 24 are arranged facing each other. The hot air flow 25 is a hot air generator
Generated from 26. The hot air volume was set to 0.3 m ³ . The magnetic toner 21 dispersed and jetted in the hot air stream 25 is subjected to a surface modification treatment, and then taken in by the hood 27 together with the surrounding air and cooled. Cool magnetic toner arrow
Recovered by a cyclone (not shown) at the end of 28.

FIG. 1 shows a cross-sectional view of the surface-modified magnetic toner. 31 is a binder resin, 32 is magnetic particles, 33 is a charge control agent, 34 is a release agent, 35 is silica, and 36 is organic fine particles.

Since the magnetic toner is made spherical by the surface modification treatment, high fluidity can be obtained. Further, since the silica 35 and the organic fine particles 36 are fixed, the adhesion state of the silica and the organic fine particles is stable against the stress received from the inside of the developing device and the cleaning blade as compared with the case of simply adding, and the flow is There is no change in the charging property or the charge amount. Therefore, silica or organic fine particles are not released even after continuous use for a long period of time, toner filming of the photoconductor, aggregation of organic fine particles, image generation are suppressed, and cleaning property is stable.

In the examples, a magnetic toner was manufactured by adding an external additive shown in (Table 2) to the toner base having the material composition shown in (Table 1) and performing an external addition treatment and a surface modification treatment. Its properties were measured.

[Table 2] In addition, in (Table 2), the addition amount is 10 of the toner base.
It represents the parts by weight of each external additive with respect to 0 parts by weight. The specific surface area is the ratio of the surface area to the weight of each external additive (unit is m ² / g), and is measured by a normal BET measurement method. Shimadzu specific surface area measuring device Flow
Sorb 2300 was used. The toner particle size is the average particle size of the manufactured magnetic toner. The volume average particle size is measured using a Coulter Counter TA-2 manufactured by Nikkaki Co., Ltd., and 50% of the volume distribution is the average particle size. The diameter. The surface modification temperature is the hot air temperature in the surface modification treatment.

The physical property values of each magnetic toner in (Table 2) are shown in (Table 3).

[Table 3] In (Table 3), the static bulk density defines the fluidity of the magnetic toner, and a large value thereof means that the fluidity is high. Static bulk density in the initial state,
The static bulk density after copying 25,000 sheets was measured using a powder tester PT-E manufactured by Hosokawa Micron. The charge amount was measured by the blow-off method. For the measurement sample, the toner was mixed so that the toner concentration was 10% with respect to the non-coated ferrite carrier, and the mixture was put into a 100 ml polyethylene bottle and the rotation speed was 6
The one stirred at 0 rpm for 10 min was used. Regarding this charge amount, the charge amount in the initial state and the charge amount after the copying test of 25,000 sheets were performed were measured.

From Table 3, the toners A1, A2, A3
Is less than the toner B1 in the initial state and the charge amount is 2
It can be seen that it is high after the copying test of 5,000 sheets, and when compared with Toner B2, both the fluidity and the chargeability are extremely high both in the initial state and after the copying test.

Next, various toners were used to perform copying by the electrophotographic method shown in FIG. 3, and the copied image was measured and evaluated. In this copy test, 16 lines / mm of image lines and solid black images were repeatedly copied until the number of copies reached 25,000, the image density of the copied images was measured with a reflection densitometer (Macbeth Co.), and the image quality was visually checked. evaluated. Less than,
Those having excellent image quality evaluation are shown as examples, and those having poor image quality evaluation are shown as comparative examples.

(Example 1) When Toner A1 is used,
Distortion of horizontal lines and scattering of toner were not seen in the initial copied image, and a high density uniform solid black image with an image density of 1.4 or more could be obtained. Also, the concentration is 1.4
Image lines of 16 lines / mm can be reproduced, and an image with extremely high resolution and high image quality was obtained. There is no background fog in the non-image area.

Even after copying 25,000 sheets, the fluidity of the toner did not decrease, a high charge amount was maintained, and toner filming and image deletion did not occur on the photosensitive member.
Even in the 25,000th copy, a high-density, low-ground fog copy image comparable to the initial image was obtained.

(Example 2) As a result of a copying test using the toner A2, good characteristics were obtained as in the case of the toner A1.

(Example 3) As a result of a copying test using the toner A3, good characteristics were obtained as in the case of the toner A1.

(Comparative Example 1) In the copy test using the magnetic toner B1 shown in (Table 2), the photoreceptor is scratched, toner filming occurs from about several thousand sheets, and vertical streaks occur in the image. , A practical image could not be obtained.

(Comparative Example 2) In the copying test conducted using the magnetic toner B2 in (Table 2), the toner and the organic fine particles could not be mixed well, vertical stripes were generated in the image, and a practical image was obtained. I couldn't do it.

Comparative Example 3 A toner was experimentally manufactured under the same composition and manufacturing conditions as toner A1 except that the amount of silica added was 0.05 part by weight. In a copy test conducted using this toner, the toner fluidity was low, toner aggregation was large, and practical characteristics could not be obtained.

Comparative Example 4 A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except that the amount of silica added was 6.0 parts by weight. In a copying test conducted using this toner, a large amount of floating silica, many white spots of silica adhered to a solid black image portion, and toner filming also occurred, so that a practical image could not be obtained.

(Comparative Example 5) The amount of the magnetic material added was 10% by weight.
A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except for the above. In the copy test conducted using this toner, the toner was scattered so much that practical characteristics could not be obtained.

(Comparative Example 6) The amount of the magnetic material added was 80% by weight.
A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except for the above. In the copy test conducted using this toner, the amount of charge was low, and there was much background fog, and practical characteristics could not be obtained.

Comparative Example 7 A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except that silica having a specific surface area of 20 m ² / g was used. In a copy test conducted using this toner, the toner has low fluidity and a large amount of background fog, and practical properties cannot be obtained.

Comparative Example 8 A toner was experimentally manufactured under the same composition and production conditions as the toner A1 except that silica having a specific surface area of 400 m ² / g was used. In a copy test conducted using this toner, silica agglomeration was strong, toner filming occurred, and practical characteristics were not obtained.

Comparative Example 9 A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except that the addition amount of polytetrafluoroethylene was changed to 5.0 parts by weight. In the copy test conducted using this toner, polytetrafluoroethylene aggregates were generated and adhered as white spots on the solid black part,
No practical image was obtained.

(Comparative Example 10) Specific surface area of 1.5 m ² / g
A toner was experimentally manufactured under the same composition and manufacturing conditions as the toner A1 except that the polytetrafluoroethylene fine particles of No. 1 were used. In the copy test conducted using this toner, polytetrafluoroethylene could not be dispersed uniformly with the toner during the external addition process, and a practical image could not be obtained.

Comparative Example 11 A toner was experimentally manufactured under the same composition and production conditions as the toner A1 except that polytetrafluoroethylene fine particles having a specific surface area of 30 m ² / g were used. In the copy test conducted using this toner, polytetrafluoroethylene could not be dispersed uniformly with the toner during the external addition process, and a practical image could not be obtained.

Through such a copying test, a suitable range in material composition and manufacturing conditions was determined as follows.

The addition amount of silica as an external additive is the same as that of the magnetic toner 1.
It is preferably set to 0.1 to 5.0 parts by weight with respect to 00 parts by weight. If the amount of silica added is 0.1 parts by weight or less, the fluidity of the toner will be insufficient, and if it is 5.0 parts by weight or more, the amount of floating silica will increase and white spots will appear on the image.

The addition amount of the organic fine particles is preferably set to 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner. If the addition amount of the organic fine particles is 0.01 parts by weight or less, the effect of adding the organic fine particles cannot be obtained,
If the amount is 5.0 parts by weight or more, uniform mixing with the toner cannot be performed, and an image defect of white spots appears on the image.

The specific surface area of silica is 50 to 300.
It is preferably m ² / g. Specific surface area is 50m ² /
If it is less than g, the particle size becomes large, and it becomes difficult to uniformly mix with the toner, and high fluidity cannot be obtained. Further, when the specific surface area is 300 m ² / g or more, the cohesiveness of silica becomes strong, the silica is not evenly attached to the toner base, and the amount of floating silica increases, so that toner filming occurs.

The specific surface area of the organic fine particles is ^{2 to} 25 m ² /
It is preferably g. If the specific surface area is 25 m ² / g or more, the cleaning effect cannot be obtained. If the specific surface area is less than 2 m ² / g, it will not be uniformly mixed with the toner.

The addition amount of the magnetic powder in the magnetic toner is preferably set to 15 to 70% by weight. When the addition amount of the magnetic powder 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, which causes deterioration of image quality.

The hot air temperature in the surface modification treatment is
It is preferable to set it to 100 to 600 degrees. 10
If it is 0 ° or less, the surface modification effect cannot be obtained, and if it is 600 ° or more, aggregation of the toner and deterioration of the toner material are likely to occur.

[0104]

As is apparent from the above description of the embodiments, the magnetic toner of the present invention has a toner base powder on which the external additives of silica and organic fine particles are fixed and coated with the magnetic powder. Is spherically shaped, the fluidity and charge amount of the toner are improved, and the generation of free silica and the aggregation of organic fine particles are suppressed. In addition, these characteristics do not change after long-term continuous use and maintain a long life.

Therefore, this magnetic toner is small in size and low in cost because the photoconductor attracts the magnetic toner by magnetic force and conveys it to the collecting portion, and the electrode roller collects the magnetic toner in the non-image portion by using electrostatic force and magnetic force. Even when it is used in the electrophotographic method using the developing method described above, it is possible to copy a clear and high-quality image with high density and without background fog, hollow characters and scattering of characters. Further, even if it is continuously used for a long period of time, toner filming does not occur on the photosensitive member, and excellent cleaning property can be maintained.

Therefore, this electrophotographic method can sufficiently exhibit its performance by using this magnetic toner.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic toner according to an embodiment of the present invention,

FIG. 2 is a diagram showing an apparatus for performing surface modification treatment of magnetic toner according to an embodiment of the present invention,

FIG. 3 is a diagram showing a configuration of an apparatus for carrying out the electrophotographic method of the present invention.

[Explanation of symbols]

 1 photoconductor drum 2 fixed magnet contained in the photoconductor 3 corona charger 4 grid electrode 6 toner hopper 7 magnetic toner 8 electrode roller 9 magnet installed inside the electrode roller 11 scraper 12 transfer charger 16 damper 21 external addition Magnetic toner after 22 22 Fixed amount feeder 23 Compressed air 24 Dispersion nozzle 25 Hot air flow 26 Hot air generator 27 Hood 31 Toner binder resin 32 Magnetic material 33 Charge control agent 34 Release agent 35 Hydrophobic silica 36 Polytetrafluoroethylene fine particles

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 15/08 111 111 112 507 E G03G 9/08 375 381 (72) Inventor Hideki Tatematsu Kadoma City, Osaka Prefecture 1006 Kadoma, Matsushita Electric Industrial Co., Ltd.

Claims (19)

[Claims] 1. A magnetic toner in which a magnetic toner matrix contains at least a binder resin and magnetic particles, wherein hydrophobic silicon dioxide fine particles and organic particles are formed on the surface of the spherical powder of the magnetic toner matrix. A magnetic toner, wherein an external additive containing fine particles is fixed. 2. The magnetic toner according to claim 1, wherein the amount of the magnetic particles added is 15 to 70% by weight based on the weight of the magnetic toner base. 3. The addition amount of the hydrophobic silicon dioxide fine particles is 0.1 to 100 parts by weight of the magnetic toner base material.
The magnetic toner according to claim 1, which is 5.0 parts by weight. 4. The magnetic toner according to claim 1, wherein the hydrophobic silicon dioxide fine particles have a specific surface area of 50 to 300 m ² / g. 5. The magnetic toner according to claim 1, wherein the amount of the organic fine particles added is 0.01 to 3.0 parts by weight based on 100 parts by weight of the magnetic toner base. 6. The specific surface area of the organic fine particles is 2 to 25.
The magnetic toner according to claim 1 or 5, wherein the magnetic toner is m ² / g. 7. A method for producing a magnetic toner, wherein the magnetic toner base contains at least a binder resin and magnetic particles, and a magnetic toner base powder, hydrophobic silicon dioxide fine particles and organic fine particles are contained. After mixing an additive and attaching an external additive to the surface of the magnetic toner base powder, the magnetic toner base powder is dispersed and jetted in a hot air stream to melt the surface of the magnetic toner base powder. A method for producing a magnetic toner, wherein the external additive is fixed on the surface of the magnetic toner base powder, and at the same time, the magnetic toner base powder is made spherical. 8. The method for producing a magnetic toner according to claim 7, wherein the temperature of the hot air stream is set to 100 to 600 degrees. 9. The method for producing a magnetic toner according to claim 7, wherein the amount of the magnetic particles added is set to 15 to 70% by weight based on the weight of the magnetic toner base. 10. The amount of the hydrophobic silicon dioxide fine particles added is 0.1 to 100 parts by weight of the magnetic toner base.
The method for producing a magnetic toner according to claim 7, wherein the amount is set to 5.0 parts by weight. 11. The hydrophobic silicon dioxide fine particles,
The method for producing a magnetic toner according to claim 7, wherein a specific surface area of 50 to 300 m ² / g is used. 12. The production of magnetic toner according to claim 7, wherein the amount of the organic fine particles added is set to 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner base. Method. 13. The organic fine particles have a specific surface area of 2
The method for producing a magnetic toner according to claim 7 or 12, characterized in that fine particles of -25 m ² / g are used. 14. An electrophotographic method using a one-component magnetic toner, wherein, as the magnetic toner, hydrophobic silicon dioxide fine particles and organic fine particles are provided on the surface of a spherical powder of a magnetic toner matrix containing a binder resin and magnetic particles. Using a magnetic toner having an external additive fixed thereto, the magnetic toner is magnetically attached to the photoconductor, and the photoconductor is rotated to convey the attached magnetic toner to a collecting unit to face the photoconductor. An electrophotographic method, characterized in that an electrostatic force and a magnetic force are applied to the electrode rollers arranged in parallel to collect the magnetic toner adhered to the non-image portion of the photoconductor. 15. The amount of magnetic particles added to the magnetic toner is 15 to 70 with respect to the weight of the magnetic toner base.
15. The electrophotographic method according to claim 14, wherein the weight% is set. 16. The method according to claim 14, wherein the amount of the hydrophobic silicon dioxide fine particles added to the magnetic toner is set to 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner base. The described electrophotographic method. 17. The electrophotographic method according to claim 14, wherein the hydrophobic silicon dioxide fine particles of the magnetic toner have a specific surface area of 50 to 300 m ² / g. 18. The amount of organic fine particles added to the magnetic toner is 0.
The electrophotographic method according to claim 14, wherein the amount is set to 01 to 3.0 parts by weight. 19. The organic fine particles of the magnetic toner,
The electrophotographic method according to claim 14 or 18, wherein a specific surface area of ² to 25 m ² / g is used.