JPH07311474A - Magnetic toner and electrophotographic method - Google Patents

Abstract

PURPOSE:To obtain high image quality and to prevent the occurrence of toner filming by using specific toners in an electrophotographic method having a development method featuring a small size and high performance. CONSTITUTION:The magnetic toners 7 to be used are 5.5 to 8.5mum in the volume average grain size of the base material of the magnetic toners, are <=30number% in the amt. of the fine powder of 2 to 4mum and are <=4m<2>/g in the specific surface area value by a BET method. The toners described above contain external additives consisting of inorg. particles which have an average grain size of 0.1 to 4mum and true sp. gr. of 5.0 to 8.5g/cm<3> and negative charge type hydrophobic silica particulates which are 50 to 350m<2>/g in the BET specific surface area by nitrogen adsorption and are subjected to a surface treatment by silicone oil. An electrostatic latent image is formed on a photoreceptor 1 contg. a stationary magnet 9 and the toners 7 are sprinkled thereon and are magnetically stuck thereto in a developing process. The photoreceptor is carried and transported in this state to a recovering section facing an electrode roller 8, where this electrode roller 8 is biased by AC and the toners of the non-image parts on the photoreceptor 1 are removed by electrostatic force and magnetic force.

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 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. 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. A means for uniformly charging the surface has been put into practical use. 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 the light on and off. When a latent image (high or 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 charged positively or negatively in advance, and a charge having a polarity opposite to the polarity of the toner is applied from the back surface of the copy sheet and is 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 development 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 the first developing method used in a copying machine for electrophotography. 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 non-image portion in the middle.

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 comprises 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. It is configured. As the resin component, a natural or synthetic resin may be used alone or may be used by appropriately mixing.

In recent years, electrophotographic apparatuses are required to have higher quality of copied images and long-term stability of image quality. In order to meet such demand, the toner has a smaller particle size and is more stable than ever. Sex is required.

[0007]

However, in the above construction, there is a case where a so-called toner filming phenomenon occurs in which 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. If the toner adheres to the surface of the photoconductor, the light is blocked during exposure according to the image pattern,
No electrostatic latent image is formed, and in reversal development, white spots occur, resulting in image defects.

Therefore, an abrasive is added to prevent filming on the surface of the photoconductor. However, when inorganic fine particles having a small true specific gravity such as alumina and titania are added to the toner base as an abrasive, the mixing property with the toner base is poor, and the inorganic fine particles themselves tend to agglomerate, resulting in image defects due to adhesion to the photoreceptor. , It may damage the photoconductor.

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, the inventors of the present invention have proposed a new electrophotographic method capable of realizing downsizing and high performance of development (Japanese Patent Laid-Open No. 5-72).
890). This electrophotographic developing method eliminates the need for a non-image area by using a photoreceptor containing a fixed magnet and a toner recovery electrode roller (hereinafter referred to as an electrode roller) having a magnet facing the photoreceptor with a predetermined gap. The toner is removed. 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 improve the image quality and stabilize the image quality for a long time by using this developing method, a toner having higher charge and higher fluidity is 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. However, by reducing the toner particle size, the latent image formed on the photoconductor can be visualized more faithfully, and it is possible to reduce the toner scattering around the characters and the character thickening. High-quality and high-resolution images can be obtained.

Therefore, in order to improve the fluidity of the toner, conventionally, a means for adding an external additive such as silica as a fluidity imparting agent has been taken (Japanese Patent Publication No. 54-16219). However, when an external additive such as silica is added, the fluidity is improved to some extent with the addition amount, but the suspended matter of the external additive is increased, and this silica is driven into the photoreceptor by the pressing force of the cleaning blade. Scratches occur on the photoconductor. As a result, silica and toner tend to adhere to the photoconductor, and the toner filming described above frequently occurs.

The present invention solves the above-mentioned conventional problems, and is suitable for a developing method which enables further downsizing, simplification and cost reduction of the above-mentioned apparatus, and has high resolution and high resolution. It is an object of the present invention to provide a magnetic toner and an electrophotographic method capable of achieving image density and high image quality of low ground fog over a long period of time.

Another object of the present invention is to provide a magnetic toner and an electrophotographic method capable of preventing the occurrence of toner filming.

[0017]

In order to solve the above problems, the magnetic toner and electrophotographic method of the present invention have the following configurations.

A magnetic toner comprising at least a binder resin, a magnetic toner matrix comprising magnetic particles and an external additive, wherein the magnetic toner matrix has a volume average particle size of 5.5.
The amount of fine powder of ˜8.5 μm, 2 to 4 μm is 30% by number or less, the specific surface area value by BET method is 4 m ² / g or less, and the external additive has an average particle diameter of 0.1 to 4 μm and a true specific gravity. Is 5.
A magnetic toner comprising inorganic fine particles of 0 to 8.5 g / cm ³ and negatively chargeable hydrophobic silica fine particles having a BET specific surface area of 50 to 350 m ² / g by nitrogen adsorption and surface-treated with silicone oil.

Further, in the present invention, the addition amount of magnetic particles is
The magnetic toner is 15 to 70% by weight of the magnetic toner base weight.

Further, in the present invention, the addition amount of the inorganic fine particles is 0.1 to 5.0 with respect to 100 parts by weight of the magnetic toner base.
It is a magnetic toner that is part by weight.

Furthermore, the present invention is a magnetic toner in which the amount of negatively charged hydrophobic silica fine particles added is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner base.

Further, the present invention is a magnetic toner in which the inorganic fine particles are titanate fine particles or zirconate fine particles.

Further, according to the present invention, the electrostatic latent image holding member that moves by containing a fixed magnet, the toner hopper, and the toner having the magnet inside at a position having a predetermined gap with the surface of the electrostatic latent image holding member. It has a collecting electrode roller and forms an electrostatic latent image on the electrostatic latent image holder, and then magnetically attracts magnetic toner to the surface of the electrostatic latent image holder located in the toner hopper to electrostatically absorb the electrostatic latent image. Magnetic toner is carried on the surface of the image holding member, the electrostatic latent image holding member is moved to face the toner collecting electrode roller, the toner is left in the image portion of the electrostatic latent image holding member, and the toner in the non-image portion is removed. A developing process in which the toner recovery electrode roller collects the toner, a transfer process in which the magnetic toner that has become a visible image on the electrostatic latent image carrier is transferred to transfer paper by electrostatic force, and a partial electrostatic latent image is held during the transfer process. Cleaning process to remove the magnetic toner remaining on the body from the electrostatic latent image carrier Which is a magnetic toner comprising at least a binder resin, a magnetic toner base composed of magnetic particles, and an external additive, wherein the volume average particle diameter of the magnetic toner base is at least 5.5-
The amount of fine powder of 8.5 μm, 2 to 4 μm is 30% by number or less,
The specific surface area value by the BET method is 4 m ² / g or less,
The external additive has an average particle size of 0.1 to 4 μm and a true specific gravity of 5.0 to
Inorganic fine particles of 8.5 g / cm ³ and BE by nitrogen adsorption
The electrophotographic method uses a magnetic toner composed of negatively charged hydrophobic silica fine particles having a T specific surface area of 50 to 350 m ² / g and surface-treated with silicone oil.

Further, in the present invention, the addition amount of magnetic particles is
It is an electrophotographic method using a magnetic toner whose amount is 15 to 70% by weight of the magnetic toner base weight.

Further, in the present invention, the addition amount of the inorganic fine particles is 0.1 to 5.0 with respect to 100 parts by weight of the magnetic toner base.
This is an electrophotographic method using a magnetic toner, which is part by weight.

Furthermore, the present invention is an electrophotographic method using a magnetic toner in which the amount of negatively charged hydrophobic silica fine particles added is 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner base. .

Furthermore, the present invention is an electrophotographic method using a magnetic toner in which the inorganic fine particles are titanate fine particles or zirconate fine particles.

[0028]

The volume average particle diameter of the magnetic toner matrix of the present invention is
30% by number of fine powder of 5.5 to 8.5 μm and 2 to 4 μm
In the following, since the specific surface area value by the BET method is 4 m ² / g or less, the fluidity is high, the latent image on the photoconductor can be faithfully reproduced, and a high-resolution image can be obtained.

Further, the amount of fine powder of 2 to 4 μm of the magnetic toner base is 30% by number or less, and the specific surface area value by the BET method is 4 m.
^Since it is ² / g or less, the amount of fine powder that reduces the fluidity of the magnetic toner is small. Therefore, when the inorganic fine particles of the present invention are added and mixed, the inorganic fine particles are uniformly mixed with the toner base without agglomeration or segregation, so that an image defect or a filming trigger is generated on the surface of the photoreceptor. It won't hurt you. Then, since the inorganic fine particles are uniformly dispersed, it is possible to remove the foreign matter attached to the surface of the photoconductor.

The negatively charged hydrophobic silica fine particles surface-treated with silicone oil are completely covered with silanol groups having hydrophilicity present on the surface, and a large number of siloxane groups are present on the surface. Therefore, it has a high negative chargeability, and has an effect of increasing the charge amount of the toner. And silica itself also has a releasing effect. However, although the silica fine particles surface-treated with silicone oil have a high negative charge amount, they have a strong cohesive property and it is difficult to uniformly mix them with the toner base. Since the magnetic toner matrix of the present invention has a specific particle size distribution, the inorganic fine particles are uniformly mixed, and at the same time, the inorganic fine particles have a specific particle size, specific surface area, and true specific gravity. , Has a function of loosening silica aggregates and can be uniformly dispersed.

Therefore, the BET by the nitrogen adsorption of the present invention is
A toner having a specific surface area of 50 to 350 m ² / g and negatively chargeable hydrophobic silica fine particles surface-treated with a silicone oil represented by the general formula (Formula 1) and inorganic fine particles is added, the silica aggregates are loosened. Therefore, uniform mixing with the toner base can be performed. Therefore, both the charge amount and the fluidity are increased, the generation of the opposite polarity toner can be suppressed to an extremely low level, and a clear image with high image density and no toner scattering around the characters can be obtained.

[0032]

[Chemical 1]

At this time, the polymerization degree n is preferably 10 to 100. When the polymerization degree n is 10 or less, it is difficult to obtain high negative chargeability. Further, when the degree of polymerization is 100 or more, the surface treatment becomes uneven.

The volume average particle diameter of the magnetic toner matrix is 5.5 μm.
When it is m or less, the fluidity is low, the image density is low, and the image has many unevenness even when used in combination with the inorganic fine particles and silica of the present invention. If the volume average particle diameter of the magnetic toner base is 8.5 μm or more, the image resolution is lowered.

The amount of fine powder of 2 to 4 μm of the magnetic toner matrix is 3
When it is 0% by number or more, the fluidity of the magnetic toner is lowered. Therefore, it becomes difficult to remove the magnetic toner attached to the non-image portion of the photoconductor, and the background fog increases. Further, since the inorganic fine particles are not uniformly mixed with the magnetic toner and agglomerate, an image defect or a scratch as a trigger for filming is given to the photoconductor.

The fact that the specific surface area value of the magnetic toner base material by the BET method is 4 m ² / g or more means that the magnetic toner base material has
Even if the amount of fine powder of ˜4 μm is 30 number% or less, it means that there are many fine powder of 2 μm or less that cannot be measured by the particle size distribution measuring device, or that the surface irregularities of the magnetic toner base are severe. Therefore, the fluidity of the magnetic toner is low and a high-quality image cannot be obtained.

If the average particle size of the inorganic fine particles is 0.1 μm or less, the inorganic fine particles agglomerate, so that even if mixed with the toner base having the particle size distribution of the present invention, they are not uniformly mixed and the toner particles are not mixed. Minging occurs. Further, when the average particle size of the inorganic fine particles is 4 μm or more, the inorganic fine particles cause scratches on the photoconductor.

When the true specific gravity of the inorganic fine particles is 5.0 g / cm ³ or less, the inorganic fine particles themselves tend to agglomerate, and even when mixed with the toner base having the particle size distribution of the present invention, they are not uniformly mixed, Image defects or scratches on the photoconductor occur. When the true specific gravity of the inorganic fine particles is 8.5 g / cm ³ or more, the inorganic fine particles are selectively consumed from the toner hopper during continuous printing, and toner filming does not occur in the initial stage, but a stable image is obtained for a long period of time. I can't.

If the BET specific surface area of the negatively-charged hydrophobic silica fine particles due to nitrogen adsorption is 50 m ² / g or less, the particle size becomes large and high fluidity cannot be obtained. Specific surface area is 3
When it is 50 m ² / g or more, the cohesiveness of silica becomes strong,
Even when mixed with the inorganic fine particles, agglomerates are generated, the particles are not evenly attached to the toner base, the amount of floating silica increases, and toner filming occurs.

The amount of the magnetic particles added to the magnetic toner is preferably 15 to 70% by weight. 15% by weight
If the amount is less than 70% by weight, the amount of toner scattering increases, and if the amount is more than 70% by weight, the amount of charge on the toner decreases and the image quality deteriorates.

The addition amount of the inorganic fine particles is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner base. If the addition amount is 0.1 parts by weight or less, the polishing effect is not exerted, so that toner filming occurs on the photoconductor. If it is 5.0 parts by weight or more, the fluidity of the toner is lowered, the image density is lowered, and the image becomes uneven.

The amount of negatively charged hydrophobic silica fine particles added is
0.1 to 5 parts by weight per 100 parts by weight of the magnetic toner base.
It is preferably 0 part by weight. When the amount is 0.1 parts by weight or less, the fluidity of the toner is lowered, the image density is lowered, and the image becomes uneven. If the amount is 5.0 parts by weight or more, toner filming occurs on the photoconductor even if inorganic fine particles are mixed.

The inorganic fine particles are preferably titanate fine particles or zirconate fine particles. The fine particles of titanate or fine particles of zirconate are extremely uniformly dispersed when mixed with the toner base material, no aggregates of the inorganic fine particles themselves are generated, and the photoreceptor is not damaged.
It is considered that the high dielectric properties of the titanate fine particles or zirconate fine particles and the surface shape influence the miscibility with the negatively charged hydrophobic silica fine particles.

In the developing step of the electrophotographic method of the present invention, an electrostatic latent image is formed on a photosensitive member containing a fixed magnet, toner is sprinkled on the electrostatic latent image and magnetically adhered thereto, and the electrostatic latent image is opposed to the electrode roller in this state. The toner is carried and conveyed to the collecting unit, and an AC bias is applied to the electrode roller to remove the non-image portion toner on the photoconductor by electrostatic force and magnetic force.

Therefore, the electrophotographic method presented in the present invention can be made smaller and higher in performance by adding to the cascade development method a magnet inside the photosensitive member and a structure for applying an AC voltage to the electrodes. It was done.

In this electrophotographic method, the development is almost completed when the toner is first sprinkled on the photosensitive member. It is the photoconductor that carries and carries the toner from the toner hopper to the developing section, and the electrode roller section functions to collect the toner in the non-image section of the electrostatic latent image and to circulate the toner in the toner retainer. The bare surface of the electrode roller, which does not carry the toner layer, faces the photoconductor. Since the electrode roller and the photoconductor rotate in opposite directions, even if a foreign substance suddenly enters the collection field where the photoconductor and the electrode roller face each other or the toner aggregates, it can be immediately removed by the reverse rotation. It is a composition.

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. When the charge amount of the toner decreases, the image force with the photoconductor becomes weaker, the toner attached to the photoconductor is easily removed by the magnetic force, and the image density decreases. Further, the amount of toner scattering around the characters increases, and the sharpness of the image decreases. In addition, when the fluidity of the toner is low, the background fog is increased and unevenness occurs in a solid black image and a halftone image portion. Further, as compared with the conventional one-component developing method, since the toner and the photoconductor are in contact with each other for a long time during development, the photoconductor surface is easily scratched, and toner filming is likely to occur on the photoconductor. However, since the magnetic toner that has high fluidity and charge amount described above and that rapidly abrades and removes substances adhering to the photoconductor is used, these points can be covered, and clear and high image density and , It is possible to obtain a lowland fog image for a long time.

[0048]

EXAMPLES First, the electrophotographic method carried out in the present invention will be explained.

FIG. 1 schematically shows an apparatus for carrying out the electrophotographic method of the present invention. As the developing method, a one-component developing method is used. This apparatus includes a photosensitive member 1 that rotates in one direction, and a non-rotating magnet 2 that is fixed coaxially with the photosensitive member 1.
And a corona charger 3 for negatively charging the photoconductor 1,
The photoconductor 1 is provided with a grid electrode 4 for controlling the charging potential, and the photoconductor 1 is irradiated with the signal light 5 to form a latent image.

Further, as a developing device for visualizing the latent image after exposure, a toner hopper 6 for supplying the magnetic one-component toner 7 to the surface of the photoconductor 1 and a non-magnetic set with a gap with the photoconductor 1 are set. An electrode roller 8, a non-rotating magnet 9 fixed 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 for scraping off the toner on the electrode roller are provided. Electrode roller 8
Thus, the extra toner attached to the non-image portion of the photoconductor 1 is collected. Reference numeral 16 is a damper for smoothing the flow of the toner 7 in the toner hopper 6 and for preventing the toner 7 from being crushed by its own weight and clogged between the photoconductor 1 and the electrode roller 8. is there.

The apparatus also includes a transfer charger 12 for transferring the toner image 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.

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 1
It is set to 5 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, and the electrode roller 8 is rotated at a peripheral speed of 40 mm / s in the direction opposite to the traveling direction of the photoconductor (the direction of the arrow in the drawing). The gap between the photoconductor 1 and the electrode roller 8 is 3
It is set to 00 μm.

The photoconductor 1 is connected to the corona charger 3 (applied voltage-
-50 at 4.5kV, voltage of grid 4 -500V)
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. At this time, the exposure potential of the photoconductor 1 is -9.
It is 0V. Toner 7 is attached to the surface of the photoconductor 1 by the magnetic force of the magnet 2 while rotating in contact with the toner hopper 6. Next, the photoconductor 1 passes in front of the electrode roller 8.

When the photoconductor 1 passes through the uncharged region, the electrode roller 8 is superposed with a DC voltage of 0 V by the AC high voltage power source 10 at 750 V 0-p (peak-to-peak 1.5).
AC voltage (frequency 1 kHz) of kV) is applied,
When the photoconductor 1 charged to -500V and having the electrostatic latent image written thereon is passed, the electrode roller 8 is superposed with a DC voltage of -350V by the AC high voltage power source 750V0-p (peak-to-peak 1. An AC voltage (frequency 1 kHz) of 5 kV) is applied. Then, 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 attached to the electrode roller 8 rotating in the direction of the arrow is scraped off by the scraper 11 and returned to the toner hopper 6 again for the next image formation.

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 obtain a copied image.

The toner remaining on the photosensitive member is scraped off by a cleaning blade or the like in the cleaning section to become waste toner.

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.

For the binder resin of the magnetic toner of the present invention, a vinyl polymer obtained by polymerizing or copolymerizing styrene and vinyl monomers such as alkyl acrylate and alkyl methacrylate can be used. Examples of the monomer styrene constituting the binder resin include styrene and α
-Styrene such as methyl styrene and P-chlorostyrene and substituted products thereof, and examples of the alkyl acrylate include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, and acrylic. There are isobutyl acid and hexyl acrylate, and examples of the alkyl methacrylates include double methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, isobutyl methacrylate, dodecyl methacrylate, and hexyl methacrylate. There are monocarboxylic acids having a bond and substituted products thereof.

When using this copolymer, it is preferable to contain 50 to 95% by weight of a styrene component. When the proportion of styrene is less than 50% by weight, the melting property of the toner is inferior, the fixing property of the toner 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.

As the binder resin, other known polymers or copolymers such as polyester resin, epoxy resin, polyurethane resin, etc. may be used, if necessary, in addition to the above main components. 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.

Further, the magnetic toner of the present invention may be blended with an appropriate pigment or dye for the purpose of coloring or controlling the charge, if necessary. As the pigment or dye, it is possible to use 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, These are blended in an amount required for charge and coloring.

The magnetic toner of the present invention may further contain a releasing agent such as WAX, a fluidity auxiliary agent such as fine powder of an organic material, a charging auxiliary agent and a cleaning auxiliary agent, if necessary.

As the inorganic fine particles of the present invention, fine particles having abrasiveness and having a true specific gravity of 5.0 to 8.5 g / cm ³ , for example, titanic acid such as barium titanate, strontium titanate, lead titanate and the like. Salts and zirconates such as barium zirconate, strontium zirconate and lead zirconate, cerium oxide, zirconium oxide, zinc oxide, tantalum oxide, niobium oxide, molybdenum oxide, lanthanum oxide, tin oxide, tungsten oxide, zirconium carbide, nitriding Fine particles such as titanium and zirconium nitride can be used. Among them, titanates such as barium titanate, strontium titanate, lead titanate, magnesium titanate, aluminum titanate and calcium titanate, and zirconates such as barium zirconate, strontium zirconate and lead zirconate are preferable. .

The titanate and zirconate are prepared by the solid phase method. Alternatively, it may be prepared by a wet synthesis method, an oxalate thermal decomposition method, or a coprecipitation method.

The solid phase method is a method in which a mixture of oxides or salts of constituent cations is baked and then pulverized. In the case of barium titanate, BaCO ₃ and TiO ₂ are mixed,
BaTiO ₃ fine particles are obtained by firing at 1150 ° C. Strontium zirconate is SrCO ₃
And ZrO ₂ are mixed and fired.

Negatively charged hydrophobic silica fine particles surface-treated with silicone oil are added to the magnetic toner of the present invention. The silica fine particles are preferably silica fine particles produced by vapor phase oxidation of a halogenated silicic acid compound. For example, the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxyhydrogen flame is utilized. The general formula of the reaction is shown in (Chemical Formula 2).

[0069]

[Chemical 2]

The silicone oil for surface-treating the silica fine particles used in the present invention is preferably polydimethyl silicone oil, alkyl-modified silicone oil, fluorine-modified silicone oil, or the like.

As the surface treatment method, known techniques such as a method of mixing using a mixer such as a Henshur mixer or a method of spraying silicone oil are used.

The magnetic toner of the present invention is manufactured by the following method. The toner is manufactured by mixing, kneading, pulverizing, classifying, and externally treating. Other methods such as a polymerization method may also be used.

The mixing treatment is carried out by using a binder resin, magnetic particles,
In addition, a charge control agent, a release agent, and an internal additive such as a pigment, which are added as necessary, are uniformly dispersed by a mixer having a stirring blade, and a known treatment method is used.

In the embodiment, the Henshur mixer FM-2 is used.
OB (manufactured by Mitsui Miike Kakoki Co., Ltd.) is used for mixing treatment.

In the kneading treatment, the mixed material is heated to disperse the internal additive in the binder resin by a shearing force. For this kneading, a three-roll type, a uniaxial screw type, a biaxial screw type is used. It is possible to use a known heating kneader that heats a kneaded material such as a mold or a Banbury mixer and applies a shearing force to knead it. In the example, a twin-screw kneader PCM
The mixture is heated and kneaded using -30 (made by Ikegai Tekko Co., Ltd.).

Next, the lump obtained by the kneading process is roughly pulverized by a cutter mill or the like and then finely pulverized. A jet mill pulverizer or the like is used for this fine pulverization treatment. Further classifying using an airflow classifier, cutting fine powder particles,
Obtain the desired particle size distribution. Further, for this fine pulverization, it is also possible to use a mechanical pulverization method in which the toner is put into a fine gap between a fixed stator and a rotating roller and pulverized. Further, for classification, it is possible to use a mechanical classification method in which the centrifugal force of a rotating rotor is used for classification. In the embodiment, the kneaded product is jet mill crusher IDS-.
Type 2 (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), then finely pulverized material is classified by using an air stream classifier DS-2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), fine powder is cut, and magnetic toner particles are obtained. Got 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 an external additive comprising silica and inorganic fine particles is added to the toner base and mixed by a known mixer or the like. In this embodiment, this mixture is mixed with Henshur Mixer FM-20B (Mitsui Miike). (Made by Kakoki Co., Ltd.).

In the examples, the material composition shown in (Table 1)
The particle size distribution was changed to prepare a toner base having a particle size distribution shown in (Table 2).

[0079]

[Table 1]

[0080]

[Table 2]

Then, the external additives shown in (Table 3) were added, and external addition treatment was carried out to produce a magnetic toner, and its characteristics were measured.

[0082]

[Table 3]

In (Table 3), the addition amount represents parts by weight of each external additive with respect to 100 parts by weight of the toner base. Here, the specific surface area is measured by an ordinary BET measuring method, and a specific surface area measuring apparatus FlowSorb2 manufactured by Shimadzu Corporation is used.
-2300 was used.

The toner particle diameter is the average particle diameter of the manufactured magnetic toner, and the volume average diameter is measured using a Coulter Counter TA-2 manufactured by Nikkaki Co., Ltd. Was defined as the average particle size.

Further, (Table 4) shows physical property values of each magnetic toner of (Table 3).

[0086]

[Table 4]

In Table 4, the quietness density is
It defines the fluidity of the magnetic toner, and a large value indicates high fluidity. Quietness Density is measured by Hosokawa Micron's powder tester PT-
Type E was used. The charge amount was measured by the blow-off method. For the measurement sample, these were mixed so that the toner concentration was 10% with respect to the non-coated ferrite carrier, the mixture was put in a 100 ml polyethylene bottle, and the rotation speed was 6
The one stirred at 0 rpm for 10 min was used.

From Table 4, toner A1, A2, A3
Has a higher fluidity than toner B4, and toner B
Compared with No. 1, B3, B5, and B6, both the charge amount and the fluidity are higher.

Next, various toners were used to perform copying by the electrophotographic method shown in FIG. 1, and the copied image was evaluated. Then, a 10,000-sheet long-term copying test was performed, and image densities before and after copying were measured by a reflection densitometer (Macbeth Co.) and evaluated.

(Example 1) When Toner A1 was used,
There is no disturbance of horizontal lines and scattering of toner in the initial copy image, and a high density solid black image with an image density of 1.4 or more can be obtained uniformly, and an image line of 24 lines / mm with a density of 1.4. It was possible to obtain an extremely high resolution and high quality image that also reproduced. There is no background fog in the non-image area.

After long-term copying of 10,000 sheets, toner filming did not occur on the photosensitive member, and a high-density, low-fog copy image comparable to the initial image was obtained.

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

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

(Comparative Example 1) Magnetic toner B shown in Table 3
A copy test was conducted on 1. As a result, the fluidity was low and the image density was low, resulting in a poor image with crushed dots.

(Comparative Example 2) Magnetic toner B shown in Table 3
A copy test was conducted at 2. As a result, the image density is high,
Although there was little ground fog, the resolution was poor.

(Comparative Example 3) Magnetic toner B shown in Table 3
A copy test was carried out at 3. As a result, the fluidity was very low and the image was inferior with many irregularities.

(Comparative Example 4) Magnetic toner B shown in Table 3
A copy test was conducted at No. 4. As a result, the photoconductor was scratched, vertical streaks and white spots were generated in the image, and the fluidity of the toner was low, so that the image density was low and a practical image could not be obtained.

(Comparative Example 5) Magnetic toner B shown in Table 3
A copy test was conducted at No. 5. As a result, both the toner charge amount and the fluidity were low, ground fog occurred, and a practical image could not be obtained.

(Comparative Example 6) Magnetic toner B shown in Table 3
A copy test was conducted at 6. As a result, toner filming occurred from about several hundreds of sheets, vertical stripes occurred in the image, and a practical image could not be obtained.

(Comparative Example 7) The average particle size of the inorganic fine particles was set to 0.
A toner was trial-produced with the same composition and manufacturing conditions as the toner A1 except that the thickness was set to 08 μm. In a copying test conducted using this toner, aggregation of inorganic fine particles occurred, uniform mixing with the toner was not possible, toner filming occurred, and practical characteristics were not obtained.

(Comparative Example 8) The average particle size of the inorganic fine particles was 6.
A toner was experimentally manufactured with the same composition and manufacturing conditions as the toner A1 except that the thickness was 0 μm. In a copy test conducted using this toner, the photosensitive member was scratched and practical characteristics could not be 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 the inorganic fine particles was changed to 0.05 part by weight relative to 100 parts by weight of the magnetic toner base material. In the copy test conducted with this toner,
Toner filming occurred and practical characteristics could not be obtained.

(Comparative Example 10) A toner was experimentally manufactured with the same composition and manufacturing conditions as the toner A1 except that the addition amount of the inorganic fine particles was 8.0 parts by weight with respect to 100 parts by weight of the magnetic toner base material. In the copy test conducted with this toner,
The fluidity of the toner was lowered and the image was uneven, and practical properties could not be obtained.

(Comparative Example 11) The specific surface area of silica was 30 m.
^A toner was experimentally manufactured with the same composition as the toner A1 except that the amount was changed to ² / g. The fluidity was low and a practical image could not be obtained.

Comparative Example 12 The specific surface area of silica is 380
A toner was trial-produced with the same composition as the toner A1 except that m ² / g was used. A large amount of floating silica, many white spots of silica adhered to the solid black image area, and toner filming also occurred, and a practical image could not be obtained.

(Comparative Example 13) A toner was experimentally prepared with the same composition as the toner A1 except that the amount of silica added was 0.05 part by weight relative to 100 parts by weight of the magnetic toner base material. The fluidity was low and a practical image could not be obtained.

(Comparative Example 14) A toner was experimentally manufactured with the same composition as the toner A1 except that the amount of silica added was 7.0 parts by weight relative to 100 parts by weight of the magnetic toner base material. A large amount of floating silica, many white spots of silica adhered to the solid black image area, and toner filming also occurred, and a practical image could not be obtained.

(Comparative Example 15) A toner was experimentally manufactured with the same composition as the toner A1 except that the addition amount of the magnetic material was changed to 10% by weight. Due to the large amount of toner scattering, practical characteristics could not be obtained.

(Comparative Example 16) A toner was experimentally manufactured with the same composition as the toner A1 except that the addition amount of the magnetic material was 80% by weight. The amount of electrification was low, and there was a lot of background fog, and practical properties could not be obtained.

[0110]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, an electrode having a movable body containing a fixed magnet and an electrode roller installed at a position having a predetermined gap from the surface of the photosensitive body and having a magnet inside. 4. A magnetic toner used in an electrophotographic method including a developing process including a roller, a transfer process, and a cleaning process, wherein a volume average particle diameter of a magnetic toner base is 5.
The amount of fine powder of 5 to 8.5 μm and 2 to 4 μm is 30% by number or less, the specific surface area value by the BET method is 4 m ² / g or less, and the average particle size is 0.1 on the surface of the magnetic toner base. ~
Inorganic fine particles of 4 μm and true specific gravity of 5.0 to 8.5 g / cm ³ and BET specific surface area of 50 to 350 m due to nitrogen adsorption.
A magnetic toner to which an external additive composed of negatively charged hydrophobic silica fine particles surface-treated with silicone oil at ² / g is added is used.

As a result, high fluidity and high charging characteristics of the toner can be obtained, and in a high-performance, small-sized, low-cost developing method, an image having an extremely high resolution with high density, low background fog, and voids and scattering of characters does not occur. Can be realized.

Further, it is possible to provide a magnetic toner and an electrophotographic method in which toner filming of the photosensitive member does not occur during long-term continuous use and the life is extended.

[Brief description of drawings]

FIG. 1 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.

[Explanation of symbols]

 1 Photoconductor drum 2 Fixed magnet 3 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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G03G 15/08 507 C G03G 9/08 101 371 375 (72) Inventor Hideki Tatematsu Kadoma City Osaka Pref. 1006 Kadoma Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A magnetic toner comprising at least a binder resin, a magnetic toner matrix comprising magnetic particles, and an external additive, wherein the volume average particle diameter of the magnetic toner matrix is 5.5 to 5. 8.5
μm, fine powder amount of 2 to 4 μm is 30 number% or less, BET
The specific surface area by the method is 4 m ² / g or less, the external additive has an average particle size of 0.1 to 4 μm, and a true specific gravity of 5.
A magnetic toner comprising inorganic fine particles of 0 to 8.5 g / cm ³ and negatively chargeable hydrophobic silica fine particles having a BET specific surface area of 50 to 350 m ² / g by nitrogen adsorption and surface-treated with silicone oil. . 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 material. 3. The magnetic toner according to claim 1, wherein the addition amount of the inorganic fine particles is 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner base. 4. The addition amount of the negatively chargeable hydrophobic silica 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. 5. The magnetic toner according to claim 1, wherein the inorganic fine particles are titanate fine particles or zirconate fine particles. 6. A toner recovery electrode roller having a fixed magnet therein and moving, an electrostatic latent image holding member, a toner hopper, and a magnet inside thereof at a position having a predetermined gap from the surface of the electrostatic latent image holding member. After forming an electrostatic latent image on the electrostatic latent image holding member, magnetic toner is magnetically attracted to the surface of the electrostatic latent image holding member located in the toner hopper, The magnetic toner is carried on the surface of the latent image holding member, the electrostatic latent image holding member is moved to face the toner collecting electrode roller, and the toner is left on the image portion of the electrostatic latent image holding member. A developing process in which the toner in the image area is collected by the toner collecting electrode roller; a transferring process in which the magnetic toner, which is visualized on the electrostatic latent image holding member, is transferred to a transfer paper by electrostatic force; The magnetic toner that partially remains on the electrostatic latent image carrier during the process And a cleaning step for removing the toner from the electrostatic latent image holding member, wherein the magnetic toner base is composed of at least a binder resin, magnetic particles, and an external additive. The magnetic toner has a volume average particle diameter of 5.5 to 8.5.
μm, fine powder amount of 2 to 4 μm is 30 number% or less, BET
The specific surface area by the method is 4 m ² / g or less, the external additive has an average particle size of 0.1 to 4 μm, and a true specific gravity of 5.
A magnetic toner comprising inorganic fine particles of 0 to 8.5 g / cm ³ and negatively charged hydrophobic silica fine particles having a BET specific surface area of 50 to 350 m ² / g by nitrogen adsorption and surface-treated with silicone oil is used. The method of electrophotography. 7. The electrophotographic method according to claim 6, wherein a magnetic toner in which the amount of the magnetic particles added is 15 to 70% by weight based on the weight of the magnetic toner base is used. 8. An electrophotographic image forming apparatus according to claim 6, wherein the amount of the inorganic fine particles added is 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner base. Method. 9. The negatively-charged hydrophobic silica fine particles are added in an amount of 0.1 to 100 parts by weight of the magnetic toner base.
7. The electrophotographic method according to claim 6, wherein 5.0 parts by weight of the magnetic toner is used. 10. The electrophotographic method according to claim 6, wherein a magnetic toner in which the inorganic particles are titanate particles or zirconate particles are used.