JPH07295282A - Magnetic toner and electrophotographic method - Google Patents

Abstract

PURPOSE:To remove the foreign matter sticking to a photoreceptor without damaging the photoreceptor and to prevent toner filming by using barium titanate particulates produced by thermal decomposition method of oxalate as an external additive. CONSTITUTION:The barium titanate particulates are separated from toners 7 and are independently adhered onto the photoreceptor 1 and are supplied to a cleaning section without being transferred to a transfer material emerging from a transfer stage and are stuck to a cleaning blade 11. Then, the foreign matter sticking to the photoreceptor 1 is removed. The barium titanate particulates having an average grain size 0.1 to 4mum, BET specific surface area 0.5 to 20m<2>/g by nitrogen adsorption, reverse polarity chargeability from the polarity of the magnetic toner base material particles and a charge quantity +3 to +20muc/g are used at this time, by which the dispersibility of the barium titanate particulates is improved. The barium titanate particulates are uniformly adhered to the magnetic toner base material particles and act effectively to prevent the filming thereof.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

A printing process of an electrophotographic copying machine or printer will be described. First, the photoreceptor is charged to form an image. As a charging method, a conventionally used corona charger is used, and in recent years, a contact type charging method in which a conductive roller is directly pressed against the photoreceptor to reduce the amount of ozone generation is used. Charge the surface uniformly. After the photoconductor is charged, in the case of a copying machine, the copy original is irradiated with light and the reflected light is applied to the photoconductor through a lens system. Alternatively, 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 a pre-charged colored powder toner (having a diameter of 5 μm).
m to about 15 μm). The toner adheres to the surface of the photoconductor according to the level of the surface potential of the photoconductor, and is electrically transferred to the copy sheet. 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. Up to now, a corona discharger has been widely used as the charge applying method as in the charging method, but in recent years, a transfer device using a conductive roller has been put into practical use in order to reduce the ozone generation amount. 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, there are a cascade developing method, a touchdown developing method, a jumping developing method and the like as a developing method for making an electrostatic latent image 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. In this 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,
In the non-image part, it is explained that it returns 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 developing method, toner is carried on a toner carrier, and a rigid or elastic regulating blade is installed on the toner carrier with a minute gap from the carrier. Then, the regulation blade regulates the toner in a thin layer, conveys the toner to a developing portion, and the toner is attached to the image portion of the photoconductor by an AC bias there. 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 is generally composed of a resin component, a coloring component consisting of a pigment or a dye, and an additive component such as a plasticizer and a charge control agent. ing. As the resin component, natural or synthetic resins are used alone or in a proper mixture.

[0007]

However, in the above-mentioned structure, the cascade developing method is not good at reproducing a solid image, which is well known in the technical field of the developing method. Further, there is a problem that the device becomes large and complicated. Furthermore, US Pat.
The developing device of type 574 has a drawback that the device is required to have high accuracy and is complicated and costly. In the jumping development method, it was essential to form a very uniform thin layer on a toner carrier carrying a toner layer. Further, in this method, so-called sleeve ghost development occurs in which the history of the previous image remains in the thin toner layer on the toner carrier and an afterimage appears in the image. Further, there is a drawback that the device is complicated and the cost is high.

Therefore, the applicant of the present invention has found that the electrophotographic method of the present invention can realize the downsizing and high performance of development (Japanese Patent Laid-Open No. 5-72).
890). In the developing method of this electrophotographic method, unnecessary toner in the non-image area is removed by 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. It is a configuration to be removed. Therefore, this developing method faithfully reproduces a solid image, does not generate a sleeve ghost, and enables further downsizing, simplification, and cost reduction of the apparatus.

However, in order to improve the image quality by using this developing method, higher performance toner characteristics are required.
Since this developing method does not use a regulating blade that regulates the toner in a thin layer, the toner is conveyed to the developing field, which is a space having a narrow gap between the photoconductor and the electrode roller, without regulating the layer. Therefore, there are few places and spaces required for the toner to be triboelectrically charged to obtain a desired charge amount, and the toner requires higher charging characteristics and higher fluidity characteristics than ever before.

At the level of fluidity of the toner used in the conventional one-component developing method or two-component developing method, unevenness occurs in the solid black image area and the halftone image area, and the background fog occurs in the non-image area. Will increase. This phenomenon remarkably appears in the toner having low fluidity. This is because a toner having a low fluidity has a low probability of coming into contact with the developing member, so that a sufficient triboelectric charge amount cannot be obtained. Further, the triboelectric chargeability varies among the toners, and uniform toner chargeability cannot be obtained.

In order to improve the fluidity of the toner, conventionally, a means for adding silica or the like as an external additive has been proposed. (Japanese Patent Publication No. 54-16219). However, although the fluidity of the toner is improved by adding an external additive such as silica,
Since the silica fine particles have a strong cohesive property, the suspended matter such as silica lumps increases, and the silica suspended matter serves as a nucleus, which is driven into the photoconductor by the pressing force of the cleaning blade and causes scratches. So-called toner filming occurs in which toner adheres to the top. Further, in the magnetic toner containing the magnetic substance internally, the magnetic substance particles are exposed on the surface at the time of pulverization, so that the photoconductor is likely to be scratched, which promotes the occurrence of filming. When this filming occurs, the surface potential is less likely to drop when the charged photoconductor is exposed, and, for example, in the reversal development, an image defect that a solid black image portion becomes white is generated.

Further, the suspended matter of silica adheres to the solid black image portion to generate white spot noise. Further, in the electrophotographic method of the present invention, toner is first sprinkled on the entire surface of the electrostatic latent image holding member and developed. Therefore, compared with the conventional method, the toner and the photoconductor are in contact with each other longer. Therefore, the toner filming is more likely to occur.

On the other hand, in order to avoid filming, it is known to use a so-called polyvinylidene fluoride powder as the friction reducing substance, for example, Japanese Patent Publication No. 48-8136.
Nos. 48-8141, 51-1130, and the like. Further, JP-A-48-47
In 345, it has been proposed to add both a friction reducing substance and an abrasive substance to the toner. According to this, it is effective for avoiding the photoconductor filming phenomenon,
When a friction reducing substance is added, it becomes difficult to remove low electric resistance substances such as paper powder and ozone adhering substances that adhere to the surface of the photoconductor by repeated use, and the latent image on the photoconductor is especially noticed in an environment of high temperature and high humidity. Has the drawback that it is significantly impaired by the low electrical resistance.

Further, JP-A-60-32060 and JP-A-59-219754 propose to add a titanate type fine powder as a second external additive. The material described here uses mechanically pulverized material, which has an irregular shape and can remove foreign matters on the photoconductor, but on the contrary, irregular protrusions. This may cause unnecessary deep scratches on the photoconductor and disturb the image.

Further, in the electrophotographic method of the present invention, since the toner is always in contact with the entire surface of the photoconductor, the original having a low blackening rate can be continuously taken by simply adding the titanate type fine powder. That is, the toner consumption is low, and the consumption of only the titanate-based fine particles is high. If the toner is used for a long period of time, the titanate-based fine particles in the toner will be exhausted and the effect on filming will be lost. There are challenges.

If the fine particles of the titanate type remain adhered to the cleaning blade, the effect on the filming continues, but when the residual toner after transfer comes to the cleaning blade, the waste toner of the titanate type remains together with the waste toner. The particles are removed from the cleaning blade, which reduces the effect.

There are also examples in which other abrasives such as alumina, titania, and zirconia are externally added to the toner. However, these substances adversely affect the charging characteristics of the toner, and lower the image density and increase the background fog. I will invite you.

In view of the above problems, the present invention provides a developing method capable of further downsizing, simplification, and cost reduction of the apparatus, in order to realize high image density and high image quality such as low background fog, high flow rate. To provide a magnetic toner having high charging property and high charging property and an electrophotographic method.

Another object of the present invention is to provide a magnetic toner and an electrophotographic method capable of preventing toner filming on a photosensitive member even after long-term use.

It is another object of the present invention to provide a magnetic toner and an electrophotographic method capable of obtaining a stable image even under high temperature and high humidity and low temperature and low humidity.

[0021]

In order to solve the above problems, a magnetic toner and an electrophotographic method of the present invention are magnetic toners comprising at least a binder resin, a magnetic substance and an external additive, wherein the external additive is used. At least an average particle size of 0.1 to 4 μm produced by an oxalate thermal decomposition method and a BET specific surface area of 0.5 to ²⁰ m ² / g by nitrogen adsorption, and at least the binder resin and the magnetic material. Which has an opposite polarity charging property to the magnetic toner base particles and has a charge amount of +3 to +30 μC / g with respect to the magnetic toner base particles, and a BET specific surface area by adsorption of nitrogen of 50 to 350 m. ^A magnetic toner made of negatively charged hydrophobic silica fine powder surface-treated with silicone oil at ² / g.

Further, the barium titanate fine particles are a magnetic toner having a static bulk density of 0.2 to 1.2 g / cm ³ .

Further, the magnetic toner is a magnetic toner containing 15 to 70% by weight based on the weight of the magnetic toner base particles.

Furthermore, the barium titanate fine particles are a magnetic toner containing 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner.

Further, fine silica powder is used as the magnetic toner 10.
It is a magnetic toner containing 0.1 to 5.0 parts by weight with respect to 0 parts by weight.

Further, the electrostatic latent image holding member which moves by enclosing a fixed magnet, the toner hopper, and the toner collecting member having a magnet inside at a position having a predetermined gap with the surface of the electrostatic latent image holding member. An electrode roller, after forming an electrostatic latent image on the electrostatic latent image holder, magnetically attract the toner to the surface of the electrostatic latent image holder located in the toner hopper, The toner is carried on the surface of the electrostatic latent image holder, the electrostatic latent image holder is moved to face the toner recovery electrode roller, and the toner is left on the image portion of the electrostatic latent image holder. The developing device is configured to collect the toner in the non-image area with the toner collecting electrode roller, and a conductive elastic roller that comes into contact with the electrostatic latent image holder is provided. Insert the transfer paper between the elastic roller and A transfer step of transferring the toner, which visualizes the electrostatic latent image on the electrostatic latent image holder by the transfer bias voltage applied to the elastic roller, to the transfer paper, and a part of the electrostatic latent image during the transfer step. An electrophotographic method comprising at least a cleaning step of removing the toner remaining on the image carrier from the electrostatic latent image carrier, wherein the magnetic toner comprises at least a binder resin, a magnetic material and an external additive. And the external additive has at least an average particle size of 0.1 to 4 μm produced by an oxalate thermal decomposition method, a BET specific surface area by nitrogen adsorption of 0.5 to ²⁰ m ² / g, and at least the binder. A barium titanate fine powder having an opposite polarity charging property to a magnetic toner base particle composed of a resin and the magnetic substance and having a charge amount of +3 to +30 μC / g with respect to the magnetic toner base particle, and nitrogen adsorption. That has a BET specific surface area of electrophotographic method using a magnetic toner comprising a negatively chargeable hydrophobic fine silica powder surface-treated with silicone oil 50~350m ² / g.

Further, it is an electrophotographic method using a magnetic toner in which the barium titanate fine particles have a static bulk density of 0.2 to 1.2 g / cm ³ .

Further, the electrophotographic method uses a magnetic toner containing a magnetic substance in an amount of 15 to 70% by weight based on the weight of the magnetic toner base particles.

Further, it is an electrophotographic method using a magnetic toner containing 0.1 to 5.0 parts by weight of barium titanate fine particles with respect to 100 parts by weight of the magnetic toner.

Further, fine silica powder is used as the magnetic toner 10.
The electrophotographic method uses 0.1 to 5.0 parts by weight of magnetic toner with respect to 0 parts by weight.

[0031]

According to the present invention, by using the barium titanate fine powder, which is produced by the oxalate pyrolysis method and has a spherical shape, as the external additive, the present invention can prevent unnecessary damage to the photoreceptor. Therefore, it becomes possible to remove the foreign matter attached to the photoconductor.

The barium titanate fine particles are separated from the toner and independently adhere to the photoconductor, are supplied to the cleaning section without being transferred to the transfer material in the transfer step, and adhere to the cleaning blade. By adhering the barium titanate fine particles to the cleaning blade, it is possible to remove foreign matter attached to the photoconductor.

At this time, the average particle diameter is 0.1 to 4 μm, the BET specific surface area due to nitrogen adsorption is 0.5 to ²⁰ m ² / g, and the magnetic toner base particles have the opposite polarity charging property, and the charge amount is blow-off. According to the measurement method, +3 to +20 μC / g of barium titanate fine particles is used, and the static bulk density is 0.2.
By using the barium titanate fine particles having a weight ratio of up to 1.2 g / cm ³ , the dispersibility of the barium titanate fine particles is improved, the barium titanate fine particles are uniformly attached to the magnetic toner base particles, and effectively act on the filming.

If the average particle diameter is less than 0.1 μm, the dispersibility of the barium titanate fine particles deteriorates, and the aggregates increase,
Image defects. Further, when the BET specific surface area due to nitrogen adsorption is 20 m ² / g or more, the dispersibility of barium titanate fine particles is deteriorated, and aggregates are increased, resulting in image defects. When the static bulk density is 0.2 g / cm ³ or less, the barium titanate fine particles have a strong cohesive property and the dispersion is deteriorated.

When the average particle diameter is 4 μm or more, the toner particles are separated from the toner base particles to give unnecessary damage to the photoreceptor. When the BET specific surface area due to nitrogen adsorption is 0.5 m ² / g or less, coarse particles increase and the coarse particles are separated from the toner base particles to give unnecessary damage to the photoreceptor. When the static bulk density is 1.2 g / cm ³ or more, the dispersibility is deteriorated and the number of scratches on the photoreceptor is increased.

When the negatively charged hydrophobic silica fine powder whose surface is treated with silicone oil is used as an external additive, a magnetic toner having a high negatively charged property can be obtained, which leads to an improvement in image quality. However, the material itself has a strong secondary agglomeration property and many agglomerates of silica are present, so that the fluidity is lowered and white spot noise due to the silica soul is likely to occur.

However, the BET specific surface area due to nitrogen adsorption is 5
0 to 350 m ² / g of negatively charged hydrophobic silica is used,
Further, it was found that the silica aggregate generation can be significantly suppressed by mixing with barium titanate fine particles and externally treating. The cause is unknown, but it is speculated that a shearing force is applied to the silica during the external addition process to loosen the aggregates. It was also found that this has the effect of improving the fluidity of the toner and also enhancing the charging property.

In the electrophotographic method according to the present invention, an electrostatic latent image holder containing a fixed magnet is used, and toner is sprinkled and magnetically adhered to the electrostatic latent image holder on which the electrostatic latent image is formed, and the electrode roller It is configured such that the toner is carried and conveyed to another portion, an AC bias is applied to the electrode roller, and the non-image portion toner of the electrostatic latent image holding member is removed by electrostatic force and magnetic force.

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

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

Since the developing method in the electrophotographic method according to the present invention has a simple structure, there are few toner charging opportunities and it is difficult to obtain high charging characteristics.

However, by using the magnetic toner of the present invention, high fluidity and high chargeability can be obtained, a high image density can be obtained, and a clear image can be obtained without toner scattering around the characters. .

Further, in the electrophotographic method according to the present invention, since the toner is adhered to the entire surface of the photoconductor at the time of development, the toner and the photoconductor are always in contact with each other as compared with the conventional one-component developing method. The toner filming is more likely to occur.

Further, if the barium titanate fine particles added to the toner are released from the toner and selectively adhere to the photosensitive member without limitation, the consumption of only the barium titanate fine particles may be promoted. If a document having a low blackening rate is continuously taken, the consumption of only barium titanate fine particles increases, and the effect on filming gradually decreases.

Therefore, by using the barium titanate fine particles of the present invention, the dispersibility of the barium titanate fine particles is improved, and the barium titanate fine particles are uniformly attached to the magnetic toner base particles and effectively act on filming.

Further, since the barium titanate fine particles are appropriately held by the magnetic toner base particles, the blackening rate is obtained even in the constitution of the electrophotographic method of the present invention in which the toner is always in contact with the entire surface of the photoconductor. Even if the manuscript of low quality is continuously taken, selective and unlimited consumption of only barium titanate fine particles is slightly suppressed.

This has a polarity opposite to that of the magnetic toner base particles, and its charge amount is +3 to + by the blow-off measurement method.
By using barium titanate fine particles of 30 μC / g and further having a true specific gravity of 5.0 to 8.5 g / cm ³ ,
realizable.

The charge amount of the barium titanate fine particles is +3 μm.
When it is C / g or less, the barium titanate fine particles are severely detached from the toner base particles, and the selective consumption proceeds. The charge amount of fine particles of barium titanate is +30
When it is more than μC / g, the charging property of the toner itself is affected and the background fog occurs.

If the true specific gravity is 5.0 g / cm ³ or less, the dispersibility deteriorates. If the true specific gravity is 8.5 g / cm ³ or more, selective consumption proceeds, and stable images cannot be obtained for a long period of time.

Furthermore, the BET specific surface area due to nitrogen adsorption is 5
It was found that by adding 0 to 350 m ² / g of negatively charged hydrophobic silica, consumption of only barium titanate fine particles was strongly suppressed, and the effect on filming was significantly improved even after long-term use. .

By using this in combination with barium titanate, the adhesion to the surface of the magnetic toner base can be appropriately controlled and taken in successfully, and the consumption of barium titanate fine particles can be prevented from increasing. It is presumed to be a thing.

As a result, barium titanate fine particles are present as long as the magnetic toner remains, and the effect on filming continues even after long-term use.

BET specific surface area due to nitrogen adsorption of 50 m ²
If it is less than / g, the fluidity of the toner will decrease. When the BET specific surface area due to nitrogen adsorption is 350 m ² / g or more, the aggregating property becomes strong, and even if it is mixed with barium titanate fine particles, the agglomerates cannot be suppressed.

With the above-described structure, by using a magnetic toner having a high charge amount and a high fluidity, the developing method which enables further downsizing, simplification and cost reduction of the apparatus can be achieved. It is possible to provide a magnetic toner and an electrophotographic method capable of realizing image quality and preventing occurrence of filming on a photoconductor.

[0055]

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

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

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

In the kneading process, the mixed material is heated to disperse the internal additive in the binder resin by shearing force. The kneading at this time can be performed using a known heating kneader. As the heating and kneading machine, it is possible to use an apparatus for heating a kneaded material such as a three-roll type, a single-screw type, a twin-screw type, and a banbury mixer type and applying a shearing force to knead the mixture. The mass obtained by the kneading treatment is roughly pulverized by a cutter mill or the like, and then finely pulverized by a jet mill pulverization or the like, and fine powder particles are further cut by an airflow classifier as necessary to obtain a desired particle size distribution.

Mechanical crushing and classification are also possible. For example, there is a method of injecting toner into a minute gap between a fixed stator and a rotating roller. Known methods are used in both cases.

External additives are externally added to the magnetic toner base particles thus obtained. A known method such as a Henschel mixer or a super mixer is used for the external addition treatment.

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

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

The copolymer used in the magnetic toner according to the present invention preferably contains a styrene component as a 50 to 95% by weight component. 50% by weight of styrene
If it is less than the above range, the melting property of the toner is poor, the fixing property is insufficient, and the pulverizability is deteriorated.

The magnetic toner according to the present invention contains the binder resin as a main component as described above, but other known polymers or copolymers may be used in addition to the main component as required. . For example, there are polyester resin, epoxy resin, polyurethane resin, and the like.

To the magnetic toner according to the present invention, barium titanate fine particles are added, and the barium titanate fine particles are produced by an oxalate thermal decomposition method. This is TiCl ₄ (a
q) and BaCl ₂ .2H ₂ O mixed solution A (maintained at 30 ° or lower) was prepared, and oxalic acid (CO
OH) ₂ · 2H ₂ O aqueous solution with the mixed solution A added dropwise to BaT
iO (C ₂ O ₄ ) .4H ₂ O is obtained. Fine particles of BaTiO3 are obtained by heating this to 600 ° or more.

The amount of barium titanate particles added is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner. When the amount is 0.1 parts by weight or less, the effect on filming is small, and when the amount is 5.0 parts by weight or more, the cohesiveness is increased and the photoreceptor is uselessly scratched.

The amount of silica added is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the magnetic toner. In order to prevent the toner particles from coagulating, the addition amount of 0.1 parts by weight or more is necessary, and if it is 5.0 parts by weight or more, the floating silica increases.

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

Further, the magnetic toner according to the present invention may further contain a release agent such as WAX if necessary.

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

Next, the electrophotographic method of the present invention will be described with reference to the drawings. The present invention is not limited to this.

(Embodiment 1) FIG. 1 is a sectional view of an electrophotographic apparatus according to an embodiment of the electrophotographic method of the present invention. The developing method is a one-component developing method. 1 is an organic photosensitive drum in which phthalocyanine is dispersed in polyester binder resin, 2 is a non-rotating magnet fixed coaxially with the photosensitive body 1,
3 is a corona charger for negatively charging the photoconductor, 4 is a grid electrode for controlling the charging potential of the photoconductor, 5 is signal light,
The developing device for visualizing the latent image after exposure includes a magnetic one-component toner 7; a toner hopper 6 for supplying the magnetic toner 7 to the surface of the photoconductor 1; and a gap 8 between the photoconductor 1 and the photoconductor 1. A set non-magnetic electrode roller, 9 is a non-rotating magnet installed inside the electrode roller 8, 10 is an AC high-voltage power supply for applying a voltage to the electrode roller 8, and 11 is a polyester film for scraping off toner on the electrode roller. It is composed of a scraper, and the electrode roller 8 collects excess toner in the non-image area.

Reference numeral 12 is a damper for smoothing the flow of the toner in the toner hopper and for preventing the toner from being crushed by its own weight and being clogged between the photosensitive member and the electrode roller.

Reference numeral 13 is a corona transfer charger for transferring the toner image on the photoconductor to paper. The magnetic flux density on the surface of the photoconductor 1 is 600 Gs. The magnetic force inside the electrode roller was strengthened to improve the transportability. Further, the magnetic pole angle θ of the magnet 2 shown in the figure was set to 15 degrees. The diameter of the photoconductor 1 is 30 mm
Then, it was rotated in the direction of the arrow in the figure at a peripheral speed of 60 mm / s and used. The diameter of the electrode roller 8 is 16 mm and the peripheral speed is 40 mm.
/ S is the direction opposite to the direction of travel of the photoconductor (the direction of the arrow in the figure)
It was rotated and used. The gap between the photoconductor 1 and the electrode roller 8 was set to 300 μm.

The photoconductor 1 is connected to the corona charger 3 (applied voltage-
-50 at 4.5kV, voltage of grid 4 -500V)
It was charged to 0V. The photoconductor 1 was irradiated with laser light 5 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor is -9.
It was 0V. The magnetic toner 7 is formed on the surface of the photoconductor 1.
Was attached by a magnet in the toner hopper 6. Next, the photoconductor 1 was passed in front of the electrode roller 8. When the photoconductor 1 passes through the uncharged area, the AC high voltage power source 1 is applied to the electrode roller 8.
With 0, an AC voltage (frequency 1 kHz) of 750 V 0-p (peak-to-peak 1.5 kV) superposed with a DC voltage of 0 V was applied. After that, when the photoconductor 1 charged with −500V and having an electrostatic latent image written thereon is passed through, 750V 0-p (peak-to-peak) in which a DC voltage of −350V is superposed on the electrode roller 8 by the AC high-voltage power source 10.
An alternating voltage (frequency: 1 kHz) of 1.5 kV) was applied. Then, the toner adhered to the charged portion of the photoconductor 1 was collected by the electrode roller 8, and a negative-positive inverted toner image of only the image portion remained on the photoconductor 1. The toner adhering to the electrode roller 8 rotating in the direction of the arrow was scraped off by the scraper 11, returned to the inside of the toner hopper 6 and used for the next image formation. The toner image thus obtained on the photoconductor 1 is
After being transferred to the transfer paper by the transfer charger 13, it is thermally fixed by a fixing device (not shown) to obtain a copied image.

Examples of the magnetic toner of the present invention will be described. The present invention is not limited to this.

Table 1 shows an example of the material composition of the magnetic toner base particles of the present invention.

[0078]

[Table 1]

The measurement results of the fluidity and charge amount of each magnetic toner are shown in (Table 2). Flowability was defined as static bulk density. For the measurement, a powder tester PT-E type manufactured by Hosokawa Micron was used. The charge amount was measured by the blow-off method by weighing 0.2 g of the sample and blowing it for 180 sec at an air pressure of 0.2 kgf / cm ² . As the measurement conditions, a non-coated ferrite carrier was mixed at a toner concentration of 10%, put in a 100 ml polyethylene bottle, and stirred at a rotation speed of 60 rpm for 10 minutes.

[0080]

[Table 2]

Table 3 shows the external additives used in Examples and Comparative Examples and the characteristics of the external additives. TA-1 and TA-2 are barium titanate fine particles produced by an oxalate thermal decomposition method, TB-1 is lead titanate, and TB-2 is alumina fine powder.

[0082]

[Table 3]

The measurement of the chargeability of the external additive is the same as the condition for measuring the charge amount of the magnetic toner. The difference is that the coarsely crushed magnetic toner base particles before crushing are opened instead of the uncoated ferrite carrier. The one that had been sieved with a mesh having a diameter of 100 μm was used. The mixed concentration is 10%.

The specific surface area is measured by an ordinary BET measuring method,
Shimadzu specific surface area measuring device FlowSorb230
0 was used.

As the static bulk density of the external additive, a powder tester PT-E type manufactured by Hosokawa Micron Co., Ltd. was used as in the toner.

The production of the magnetic toner of the present invention will be described. The mixture shown in (Table 1) was used as a Henschel mixer FM.
Mix with 20B (Mitsui Miike). The mixture is heated and kneaded with a twin-screw kneading extruder PCM30 (manufactured by Ikegai Tekko KK). The kneaded product is roughly crushed to a size of 2 mm or less with a coarse crusher Rotoplex (manufactured by Alpine). Then, fine pulverization is performed with a jet mill pulverizer IDS-2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). Air flow classifier DS2
Cut fine powder with a mold (made by Nippon Pneumatic Mfg. Co., Ltd.). By the above treatment, magnetic toner base particles having an average particle diameter of 8 μm were obtained. Then, the external additive was externally added.

The material composition of the magnetic toner A1 of the present invention is shown in (Table 4).

[0088]

[Table 4]

As the external additive, barium titanate fine particles and hydrophobic silica treated with polydimethyl silicone oil were used.

As shown in (Table 2), it can be seen that the magnetic toner A1 exhibits high fluidity and high chargeability.

Further, as shown in (Table 3), it is understood that the barium titanate fine particles of the present invention have the opposite chargeability to the magnetic toner base particles and keep them higher than the other particles.

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

Then, a long-term copying test of 10,000 sheets was conducted. There is no decrease in the fluidity of the toner after 10,000 sheets, a high charge amount is maintained, and filming does not occur on the photoconductor. A high-density, low-ground fog copy image comparable to the initial image was obtained.

Table 5 shows the fluidity and image density of the toner at the initial stage and after the 10,000-sheet copying test.

[0095]

[Table 5]

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

Example 2 The material composition of the magnetic toner A2 of the present invention is shown in (Table 6).

[0098]

[Table 6]

Barium titanate fine particles and hydrophobic silica treated with polydimethyl silicone oil were used as external additives.

A copying test was conducted using the magnetic toner A2 of the present invention by using the electrophotographic method shown in FIG. The image density was measured by a reflection densitometer (Macbeth) and evaluated.
As a result, an extremely high-resolution and high-quality image is obtained, in which horizontal lines are not disturbed, toner is not scattered, hollow characters are not present, and a solid black image is uniform and 16 lines / mm with a density of 1.4 are reproduced. Was given. A high-density image having an image density of 1.4 or more was obtained. No background fog has occurred in the non-image area.

Then, a long-term copying test of 10,000 sheets was conducted. There is no decrease in the fluidity of the toner after 10,000 sheets, a high charge amount is maintained, and filming does not occur on the photoconductor. A high-density, low-ground fog copy image comparable to the initial image was obtained.

(Comparative Example 1) A magnetic toner B1 was produced as a trial with the same composition and formulation as in Example 1 except that the external additives were different.
Table 7 shows the material composition of the magnetic toner B1.

[0103]

[Table 7]

As the external additive, fine particles of lead titanate and hydrophobic silica treated with dimethyldichlorosilane were used.

Using the electrophotographic method shown in Example 1,
A copy test was conducted with magnetic toner B1. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, the image density was slightly low and the image was heavily fogged.

In the long-term copying test, toner filming occurred after about 2000 sheets.

(Comparative Example 2) A magnetic toner B1 was manufactured as a trial with the same composition and formulation as in Example 1 except that the external additives were different.
Table 8 shows the material composition of the magnetic toner B1.

[0108]

[Table 8]

Hydrophobic silica treated with hexamethylenedisilazane and alumina fine powder were used as external additives.

Using the electrophotographic method shown in Example 1,
A copy test was conducted with magnetic toner B2. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, the image density was slightly low and the image was heavily fogged.

In the long-term copying test, toner filming occurred after 1000 sheets.

(Comparative Example 3) The addition amount of the magnetic material was 10% by weight.
A toner was trial-produced with the same composition as in Example 1 except for the above. Due to the large amount of toner scattering, practical characteristics could not be obtained.

(Comparative Example 4) The addition amount of the magnetic material was 80% by weight.
A toner was trial-produced with the same composition as in Example 1 except for the above. The amount of electrification was low, and there was a lot of background fog, and practical properties could not be obtained.

(Comparative Example 5) A toner was experimentally prepared with the same composition as in Example 1 except that the amount of silica added was 0.05 parts by weight. The fluidity was poor and practical properties could not be obtained.

(Comparative Example 6) A toner was experimentally prepared with the same composition as in Example 1 except that the amount of silica added was 6 parts by weight.
There were many silica aggregates and many white spots adhered to the solid black image area, and practical properties could not be obtained.

(Comparative Example 7) A toner was experimentally prepared with the same composition as in Example 1 except that the addition amount of barium titanate fine particles was changed to 0.05 part by weight.

In the long-term copying test, toner filming occurred after 1000 sheets and a practical image could not be obtained.

(Comparative Example 8) A toner was experimentally prepared with the same composition as in Example 1 except that the addition amount of barium titanate fine particles was 6 parts by weight. Many barium titanate fine particles were aggregated and many scratches were generated on the photoreceptor, so that practical characteristics could not be obtained.

[0119]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, an electrostatic latent image holding member that contains a fixed magnet and moves, is installed at a position having a predetermined gap with the surface of the electrostatic latent image holding member, and is internally provided. A developing step including an electrode roller having an electrode roller having a magnet,
A magnetic toner used in an electrophotographic method, comprising a transfer step and a cleaning step, the average particle diameter, the specific surface area,
By containing barium titanate fine particles defined by true specific gravity and silica fine powder surface-treated with silicone oil, highly fluid and highly chargeable toner can be obtained, and high performance, small size, low cost development method In, it is possible to realize high image quality with high density and low background fog. It is also possible to provide a magnetic toner and an electrophotographic method capable of suppressing the occurrence of toner filming on the photoconductor.

[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 contained in photoconductor 3 Corona charger 4 Grid electrode 6 Toner hopper 7 Magnetic toner 8 Electrode roller 9 Magnet installed inside electrode roller 11 Scraper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 15/09 101 G03G 9/08 371 375 (72) Inventor Hideki Tatematsu Osaka Prefecture Kadoma City Kadoma 1006 Address: Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A magnetic toner comprising at least a binder resin, a magnetic material and an external additive, wherein the external additive has at least an average particle size of 0.1 to 4 μm produced by an oxalate thermal decomposition method. The magnetic toner base particles have a BET specific surface area of 0.5 to ²⁰ m ² / g by nitrogen adsorption, and have a reverse polarity charging property to at least the magnetic toner base particles composed of the binder resin and the magnetic material. Barium titanate fine powder having a charge amount of +3 to +30 μC / g, and a BET specific surface area of 50 to 350 m ² / g by nitrogen adsorption.
2. A magnetic toner comprising a negatively charged hydrophobic silica fine powder surface-treated with silicone oil. 2. Barium titanate fine particles having a static bulk density of 0.
It is 2-1.2 g / cm < ³ >, It is characterized by the above-mentioned.
The magnetic toner described. 3. The magnetic material is contained in an amount of 15 to 70% by weight based on the weight of the magnetic toner base particles.
The magnetic toner described. 4. A magnetic toner 1 comprising barium titanate fine particles.
The magnetic toner according to claim 1, wherein the magnetic toner is contained in an amount of 0.1 to 5.0 parts by weight with respect to 00 parts by weight. 5. The magnetic toner according to claim 1, wherein the fine silica powder is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the magnetic toner. 6. A toner recovery device having a magnet inside thereof, a toner hopper that moves by enclosing a fixed magnet, and a toner inside that has a predetermined gap with the surface of the electrostatic latent image carrier. An electrode roller, after forming an electrostatic latent image on the electrostatic latent image holder, magnetically attract magnetic toner to the surface of the electrostatic latent image holder located in the toner hopper, The magnetic toner is carried on the surface of the electrostatic latent image carrier,
The electrostatic latent image holding member is moved to face the toner collecting electrode roller, magnetic toner is left in the image portion of the electrostatic latent image holding member, and magnetic toner in the non-image portion is collected by the toner collecting electrode roller. And a transfer step of transferring the magnetic toner, which visualizes the electrostatic latent image on the electrostatic latent image holder, to a transfer paper by electrostatic force, and a part of the electrostatic toner during the transfer step. A cleaning process for removing the magnetic toner remaining on the latent image holding member from the electrostatic latent image holding member, wherein the magnetic toner is at least a binder resin, a magnetic member, and an external additive. Wherein the external additive has at least an average particle size of 0.1 to 4 μm prepared by an oxalate thermal decomposition method and a BET specific surface area of 0.5 to ²⁰ m ² / g by nitrogen adsorption, and at least the above. Binder resin and the above Barium titanate fine powder having a reverse polarity chargeability to the magnetic toner base particles made of a polymer and having a charge amount of +3 to +30 μC / g with respect to the magnetic toner base particles, and a BET specific surface area due to nitrogen adsorption of 50. ~ 350 m ² / g
An electrophotographic method comprising using a magnetic toner composed of a negatively charged hydrophobic silica fine powder surface-treated with silicone oil. 7. The barium titanate fine particles have a static bulk density of 0.
The electrophotographic method according to claim 6, wherein a magnetic toner having a weight of 2 to 1.2 g / cm ³ is used. 8. The magnetic material comprises 15 to 15 parts by weight of the magnetic toner.
7. The electrophotographic method according to claim 6, wherein a magnetic toner containing 70% by weight is used. 9. A magnetic toner 1 comprising barium titanate fine particles.
The electrophotographic method according to claim 6, wherein the magnetic toner is used in an amount of 0.1 to 5.0 parts by weight based on 00 parts by weight. 10. An electrophotographic method according to claim 6, wherein the magnetic toner contains 0.1 to 5.0 parts by weight of fine silica powder based on 100 parts by weight of the magnetic toner. 11. The electrophotographic method according to claim 6, wherein the magnetic toner is a one-component toner.