JPH07306543A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To attain such high image quality as high image density and low surface fog as well as to prevent the filming of a toner on a photoreceptor by using a specified magnetic toner. CONSTITUTION:This electrophotographic method includes a developing process in which an electrostatic latent image is converted into a visible image with a magnetic toner and a transferring process in which the toner forming the visible image is transferred to transfer paper. The magnetic toner consists essentially of a bonding resin, a magnetic substance and an additive consisting essentially of fine barium titanate powder and fine silica powder. The fine barium titanate powder is produced by thermally decomposing oxalates and has 0.1-4mum average particle diameter and 0.5-20m<2>/g BET specific surface area measured by nitrogen adsorption. The fine silica powder is negatively chargeable hydrophobic fine silica powder surface-treated with silicone oil and having 50-350m<2>/g BET specific surface area measured by nitrogen adsorption.

Description

Detailed Description of the Invention

[0001]

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

[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, 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. Charge the surface uniformly. After charging the photoreceptor,
In the case of a copying machine, a copy original is irradiated with light and reflected light is irradiated onto a 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 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 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.

FIG. 3 shows U of Japanese Patent Laid-Open No. 48-69524.
SP2,807,233, JP-A-3-15558
4 is a schematic diagram showing a configuration of a toner image transfer device disclosed in Japanese Patent Publication No. 4 or the like. FIG. In FIG. 3, 100 is a transfer roller made of foamed or solid rubber and adjusted to a medium resistance of about 10 ⁷ Ω, 101 is a power source for applying voltage to the transfer roller, 102 is a photoconductor, and 103 is a transfer. Paper (copy paper) 104 is toner. The operation of the transfer device configured as described above will be described.

An image is formed on the surface of the photoconductor 102 by the above-mentioned toner. Now, the normal development in which the polarity of the photoconductor 102 is negative and the polarity of the toner 104 is positive is defined. The transfer roller 100 is in contact with the photoconductor 102 with a predetermined pressing force. The transfer paper 103 is pressed against the photoconductor 102 and comes into contact with the toner 104. The transfer roller 100 has toner 10
Since the negative voltage opposite to the polarity of No. 4 is applied from the power supply device 101, the toner 104 is transferred to the transfer paper 103.
Since the transfer roller 100 is in contact with the transfer paper 103, the voltage applied from the power supply 101 can be as low as several hundreds to 3000V. The transfer paper 103 includes the photoconductor 102 and the transfer roller 10.
After passing the contact point of 0, it is conveyed to a fixing unit (not shown). With such a transfer method, generation of harmful ozone can be suppressed to an extremely low level as compared with the conventional corona discharger.

As is well known, the toner for electrostatic charge development used in these electrophotographic 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. Has been done. As the resin component, natural or synthetic resins are used alone or in a proper mixture.

[0009]

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 the 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 fluidity level of the toner used in the conventional one-component developing method and two-component developing method, unevenness is caused in the solid black image area and the halftone image area, and the background fog is caused 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.

Conventionally, in order to improve the fluidity of the toner, a means for adding silica or the like as an external additive (Japanese Patent Publication No. 54-1).
No. 6219), it has been proposed to use silica fine powder which is further hydrophobized. (JP-A-46-5782, JP-A-48-47345, JP-A-48-4
7346). For example, silica fine powder which has been hydrophobized by reacting silica fine powder with an organic silicon compound such as dimethyldichlorosilane to substitute silanol groups on the surface of the silica fine powder with organic groups is used. However, although the fluidity of the toner is improved by the addition of an external additive such as silica, the silica fine particles have a strong cohesive property, so that suspended matters such as silica particles increase. In addition, the floating silica has strong adhesion to the photoconductor.

When a pressing force is applied to the photoconductor during the process of forming an image, the silica suspended matter serves as a nucleus and is hit on the photoconductor to cause a scratch, or the nucleus serves as a nucleus to fix the toner on the photoconductor. The so-called toner filming occurs. 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, a suspended matter of silica adheres to a solid black image portion to generate white spot noise. The pressing force on the photoconductor has a force received from the cleaning blade in the cleaning section.

Further, in the electrophotographic method of the present invention, the transfer roller is in contact with the photoconductor at a constant pressure in the transfer step.

In the electrophotographic method of the present invention, the toner is first sprinkled on the entire surface of the electrostatic latent image carrier in the developing step,
It is developed. Therefore, compared with the conventional method, the toner and the photoconductor are in contact with each other for a long time, and silica is more likely to be attached.

Therefore, as compared with the conventional electrophotographic method, the toner filming is more likely to occur.

On the other hand, in order to avoid filming, the use of so-called polyvinylidene fluoride powder as the friction reducing substance is disclosed in, 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. By supplying the titanate-based fine powder to the cleaning blade, the effect can be obtained only for removing foreign matter on the photoconductor. However, the material described here uses mechanically pulverized material, which has an irregular shape, and although the effect of removing foreign matter on the photoreceptor can be obtained, conversely The protrusions may cause unwanted deep scratches on the photoconductor and disturb the image.

In the electrophotographic method of the present invention, the transfer roller is in contact with the photosensitive member. Therefore, by simply adding the titanate-based fine powder, the titanate-based fine powder is transferred to the transfer roller, is not supplied to the cleaning unit, and the effect of removing toner filming cannot be obtained.

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 is continuously taken by simply adding the titanate type fine powder. As a result, the toner consumption is low, the selective consumption of only the titanate-based fine particles is increased, and the titanate-based fine particles in the toner are exhausted when used for a long time, and the effect on filming is lost. There is a problem that it will end.

If the titanate-based fine particles remain adhered to the cleaning blade, the effect on filming continues, but when the transfer residual waste toner comes to the cleaning blade, the titanate-based particles together with the waste toner are removed. 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 the electrophotographic method of the present invention, a conductive elastic roller is used. The transfer method using the conductive elastic roller has problems such as hollow characters, hollow lines, and toner scattering around the characters.

When the toner on the photoconductor is transferred onto the transfer paper by using the transfer roller, the transfer roller is in contact with the photoconductor at a predetermined pressure. For this reason, characters and lines are edge-developed, where the amount of toner is large and the toner is concentrated, the pressure is higher than in the areas without toner, causing aggregation of toner due to pressure, A so-called "blank" occurs that is not transferred to the transfer paper. Low liquidity,
Remarkably appears in toner with a low charge amount. The transfer of the toner onto the transfer paper onto the photoconductor is carried out by the attraction between the charged electric charge of the toner and the electric charge opposite to the charged electric charge of the toner applied from the outside. When the toner charge amount is low, the toner easily scatters around the characters where no toner exists.

In view of the above problems, the present invention provides an electrophotographic method which realizes high image density and high image quality with low background fog in a developing method which enables further downsizing, simplification and cost reduction of the apparatus. To do.

Another object of the present invention is to provide an electrophotographic method capable of preventing hollow defects and scattering during transfer in a low ozone process using roller transfer.

Another object of the present invention is to provide an electrophotographic method capable of preventing toner filming on the photoconductor even in long-term use.

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

[0031]

In order to solve the above-mentioned problems, the electrophotographic method of the present invention comprises a developing step in which an electrostatic latent image formed on an electrostatic latent image carrier is visualized with a magnetic toner. A conductive elastic roller that comes into contact with the electrostatic latent image holding member, inserts a transfer sheet between the electrostatic latent image holding member and the conductive elastic roller, and applies the transfer paper to the conductive elastic roller. A transfer bias voltage for transferring the electrostatic latent image on the electrostatic latent image holding member to the transfer sheet, and a transfer step of transferring the magnetic toner onto the transfer paper. Is at least a binder resin,
It is composed of 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 and a BET specific surface area by nitrogen adsorption of at least 0.1.
Using barium titanate fine powder is 5 to 20 m ² / g, the magnetic toner BET specific surface area by nitrogen adsorption is composed of negatively chargeable hydrophobic silica fine powder surface-treated with silicone oil in 50~350m ² / g It is an electrophotographic method.

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

Further, it is an electrophotographic method using a magnetic toner containing a magnetic substance in an amount of 15 to 70% by weight based on the weight of the magnetic toner.

Furthermore, 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.

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 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 holder, the electrostatic latent image holder is moved to face the toner recovery electrode roller, and the magnetic toner is applied to the image portion of the electrostatic latent image holder. The magnetic toner of the non-image portion is left, and the developing step of collecting the magnetic toner by the toner collecting electrode roller, and a conductive elastic roller that abuts on the electrostatic latent image holding member are provided. When a transfer paper is inserted between the conductive elastic roller and A transfer step of transferring the toner, which visualizes the electrostatic latent image on the electrostatic latent image holder by a transfer bias voltage applied to the conductive elastic roller, to the transfer paper, and a part of the transfer step. A cleaning step of removing the toner remaining on the electrostatic latent image carrier from the electrostatic latent image carrier, the magnetic toner comprising at least a binder resin, a magnetic material,
It is composed of an external additive, and the external additive has at least an average particle size of 0.1 to 4 produced by an oxalate thermal decomposition method.
μm, BET specific surface area due to nitrogen adsorption is 0.5 to 20 m
Electrophotographic method using barium titanate fine powder is ² / g, the magnetic toner BET specific surface area by nitrogen adsorption is composed of negatively chargeable hydrophobic silica fine powder surface-treated with silicone oil in 50~350m ² / g Is.

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, it is an electrophotographic method using a magnetic toner containing a magnetic substance in an amount of 15 to 70% by weight based on the weight of the magnetic toner.

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.

Furthermore, the magnetic toner is an electrophotographic method which is a one-component toner. Further, it is an electrophotographic method in which the elastic member of the elastic roller is a urethane foam to which a conductivity-imparting agent is added in the transfer step.

Further, in the transfer step, the electrophotographic method is one in which the conductivity-imparting agent dispersedly added to the urethane foam is a lithium salt.

[0043]

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. 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 carrier 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.

Further, when combined with a transfer process using a conductive elastic roller as the transfer means, the magnetic toner is required to have a higher fluidity and a higher charging property than before in order to prevent hollowing during transfer and scattering around characters. Is.

In the developing process having a simple structure and the transfer process using a conductive elastic roller, a stable and high-quality image cannot be obtained unless the toner is kept to have higher fluidity and higher charging property than ever before. Further, it is necessary to improve printing durability against toner filming on the photoconductor more than ever before. Therefore, if negatively charged hydrophobic silica fine powder whose surface is treated with silicone oil is used as an external additive, negatively charged property is obtained. It is possible to obtain a high magnetic toner, which leads to an improvement in image quality.
This is because the silanol groups, which are hydrophilic groups, present on the surface of the silica fine particles are completely covered and the siloxane groups are present on the surface, and the silica fine particles have a high negative chargeability.

However, since the material itself has a high chargeability, the secondary agglomeration is strong, and many silica agglomerates are present, which promotes the deterioration of fluidity, the generation of white spot noise due to the silica soul, and the occurrence of filming.

However, the BET specific surface area due to nitrogen adsorption is 5
Negatively-charged hydrophobic silica surface-treated with silicon oil represented by the general formula (Formula 1) at 0 to 350 m ² / g is used, and further mixed with barium titanate fine particles to perform external addition treatment to obtain silica. It was found that the generation of aggregates was greatly suppressed. 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.

[0051]

[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. If the degree of polymerization n is 100 or more, the surface treatment becomes uneven.

The BET specific surface area due to nitrogen adsorption is 50
When it is less than m ² / g, the fluidity of the toner is lowered. 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.

However, it is difficult to suppress the occurrence of toner filming on the photosensitive member only by eliminating the silica aggregates and obtaining a uniform dispersion. Since silica is added to the toner by a mixing process, it is impossible to completely suppress the free silica, so that it is inevitably attached to the photoreceptor. The silica is driven into the photoconductor by some kind of stress, and toner filming occurs using it as a trigger. The stress is the cleaning blade and the transfer roller. Particularly in the electrophotographic method according to the present invention,
Since the toner is attached to the entire surface of the photoconductor during development, the toner and the photoconductor are always in contact with the entire surface as compared with the conventional one-component developing method, and thus toner filming is more likely to occur.

However, by using the barium titanate fine powder, which is produced by the oxalate thermal decomposition method and has a substantially spherical shape, as an external additive, the photoreceptor is protected from unnecessary scratches. It is possible to remove the foreign matter attached to the.

The barium titanate fine particles are separated from the toner and adhere to the photoconductor independently, and 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, barium titanate having an average particle diameter of 0.1 to 4 μm, a BET specific surface area by nitrogen adsorption of 0.5 to ²⁰ m ² / g, and a static bulk density of 0.2 to 1.2 g / cm ^3. By using the fine particles, 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.

Further, in the electrophotographic method according to the present invention, since the toner is adhered to the entire surface of the photosensitive member during development, the barium titanate fine particles added to the toner are liberated from the toner and selectively adhere to the photosensitive member without limitation. However, the consumption of only the barium titanate fine particles progresses. 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.

However, by adding the barium titanate fine particles of the present invention, the barium titanate fine particles are appropriately held by the magnetic toner base particles, so that the toner of the present invention is always in contact with the entire surface of the photoreceptor. Even if the photographic method is used, even if a manuscript having a low blackening rate is continuously taken, selective and unlimited consumption of only barium titanate fine particles can be suppressed.

As a result, barium titanate particles are present as long as the magnetic toner remains, and the effect on filming is maintained even if the waste toner is recycled and used for a long time.

Furthermore, the barium titanate fine particles have an opposite polarity charging property to the toner base particles, the charge amount is +3 to +30 μC / g by the blow-off measurement method, and the true specific gravity is 5.0 to 8.5 g / cm. By using the barium titanate fine particles of ³ , the dispersibility of the barium titanate fine particles is further improved, and the barium titanate fine particles are uniformly attached to the magnetic toner base particles,
Effectively affects filming.

Further, since the barium titanate fine particles have the opposite polarity charging property, they are supplied to the cleaning blade portion without adhering to the transfer roller, which is very effective for filming.

With the above structure, the barium titanate particles can be positively charged and sufficiently charged. Furthermore, it becomes possible to obtain a high positive chargeability by surface treatment of a titanium coupling agent, a coupling agent having a nitrogen group, an organic material having a nitrogen group, or the like.

When the average particle diameter is 0.1 μm or less, the dispersibility of barium titanate fine particles is deteriorated, and 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.

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. In addition, the amount of the toner that adheres to the transfer roller also increases, and the effect on filming decreases. When the charge amount of the barium titanate fine particles is +30 μC / g or more, the chargeability 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.

As described above, in the electrophotographic method using the magnetic toner of the present invention, the magnetic toner capable of maintaining the high fluidity and the high charging property by the developing method capable of further downsizing, simplification and cost reduction of the apparatus. By using, a high image density and a low ground fog image can be obtained, and in a transfer process using a conductive elastic roller, when toner such as characters and lines is concentrated, transfer is performed with a predetermined pressing force. However, aggregation of toner particles does not easily occur, and a clear image with no voids can be obtained.

Further, it is possible to provide an electrophotographic method capable of preventing the occurrence of toner filming on the photoconductor.

[0070]

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 material, and other internal additives such as a release agent and a pigment, which are added as necessary, by a mixer equipped with a stirring blade. 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 barium titanate fine particles having the above structure have a sufficient positive charging property. Furthermore, it becomes possible to obtain a high positive chargeability by surface treatment of a titanium coupling agent, a coupling agent having a nitrogen group, an organic material having a nitrogen group, or the like.

The amount of fine barium titanate particles added is preferably 0.1 to 5.0 parts by weight per 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.

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

[0084]

[Chemical 2]

The preferred silicone oil for surface-treating the silica fine particles used in the present invention is polydimethyl silicone oil, and alkyl-modified silicone oil, fluorine-modified silicone oil and the like are also preferred.

As the surface treatment method, a known technique is used, and a method of mixing using a mixer such as a Henschel mixer or a method of spraying silicone oil may be used.

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.

If necessary, a suitable pigment or dye is added to the magnetic toner according to the present invention for the purpose of controlling coloring and charge. Examples of such pigments or dyes include carbon black, iron black, graphite, nigrosine, metal complexes of azo dyes, phthalocyanine blue, DuPont oil red, aniline blue, benzidine yellow, rose bengal, and mixtures thereof, 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 shows a sectional view of an electrophotographic apparatus of an embodiment of the electrophotographic method of the present invention. The developing method is a one-component developing method. 1 is an organic photoconductor drum in which phthalocyanine is dispersed in a polycarbonate binder resin, 2 is a non-rotating magnet fixed coaxially with the photoconductor 1, 3 is a corona charger for negatively charging the photoconductor, 4
Is a grid electrode for controlling the charging potential of the photoconductor, and 5 is a 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 gap. The non-magnetic electrode roller set by opening the switch 9 is a non-rotating magnet fixed coaxially with the electrode roller 8, 10 is an AC high voltage power source for applying a voltage to the electrode roller 8, and 11 is polyester for scraping off toner on the electrode roller The scraper is made of a film, 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 denotes a transfer roller for transferring the toner image on the photoconductor to the paper, which is set so as to come into contact with the photoconductor 1. The transfer roller is an elastic roller in which a conductive elastic member is provided around a shaft made of a conductive metal. The pressing force to the photoconductor 1 is 0 per transfer roller 13 (about 216 mm).
~ 2000g, preferably 500-1000g.
This was measured from the product of the spring coefficient and the contraction amount of the spring for pressing the transfer roller 13 against the photosensitive member 1. The contact width with the photoreceptor is about 0.5 mm to 5 mm. The rubber hardness of the transfer roller 13 is 80 degrees or less by the Asker C measurement method (measurement using a block piece, not the roller shape), and preferably 30 degrees.
-40 degrees. In the present invention, the elastic roller 13 has a diameter of 6
A conductive urethane elastomer in which a foamable lithium salt was internally added to the periphery of a shaft having a diameter of 10 mm and having a resistance value of 10 ⁷ Ω (an electrode was provided on the shaft and the surface, and 500 V was applied to both electrodes) was used. Outer diameter of the entire transfer roller 13 is 16.4 mm
The hardness was 40 degrees in Asker C. Transfer roller 1
3 was brought into contact with the photoconductor 1 by pressing the shaft of the transfer roller 13 with a metal spring. The pressing force was about 1000 g. The present invention is not limited to this material.

Reference numeral 14 is a thrust guide made of a conductive member for introducing the transfer paper to the transfer roller 13, and reference numeral 15 is a conveyance guide in which the surface of the conductive member is covered with an insulating material. The plunge guide 14 and the transport guide 15 are grounded directly or through a resistor. Reference numeral 16 is a transfer sheet, and 17 is a voltage generating power source for applying a voltage to the transfer roller 13.

Reference numeral 18 is a cleaning blade for scraping off the transfer residual toner, and reference numeral 19 is a cleaning box for storing the waste toner.

Although an elastic urethane blade was used as the cleaning blade, a fur brush to which a bias was applied,
A similar result is obtained with a conductive metal roller.

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 and the peripheral speed is 60 m.
It was used by rotating in the direction of the arrow in the figure at m / s. The diameter of the electrode roller 8 is 16 mm and the peripheral speed is 40 mm / s.
It was used by rotating it in the direction opposite to the traveling direction (direction of arrow in the figure). The gap between the photoconductor 1 and the electrode roller 8 is 300μ
set to m.

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 1 was −90V. Toner 7 was attached to the surface of the photoconductor 1 by a magnet in the toner hopper 6. Next, the photoconductor 1 was passed in front of the electrode roller 8. When passing through the uncharged area of the photoconductor 1, an AC high voltage power source 10 superimposes a DC voltage of 0V on the electrode roller 8 and an AC voltage of 750V0-p (peak-to-peak 1.5kV) (frequency 1k).
Hz) was applied. After that, when the photoconductor 1 charged with −500V and having the electrostatic latent image written thereon passes, the electrode roller 8
750V 0-p (peak-to-peak 1.5) with a DC voltage of -350V superposed by an AC high-voltage power supply 10.
An alternating voltage (frequency 1 kHz) of kV) was applied. Then, the toner adhering to the charged portion of the photoconductor 1 is removed by the electrode roller
Then, a toner image in which only the image portion was negative-positive inverted was collected 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 transferred onto the transfer paper by the transfer roller 13 and then 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 one example of the material composition of the magnetic toner base particles of the present invention.

[0103]

[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.

[0105]

[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.

[0107]

[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, except that the coarsely crushed magnetic toner base particles before crushing are opened instead of the uncoated ferrite carrier. The one subjected to a sieving treatment 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 FlowSorb2-2
300 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).

[0113]

[Table 4]

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

As shown in (Table 2), it is understood that the magnetic toner A1 has high fluidity and high charging property.

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.

Using the electrophotographic apparatus shown in FIG. 1, a copy test was conducted with the magnetic toner A1 of the present invention. The image density was measured by a reflection densitometer (Macbeth) and evaluated.
As a result, an extremely high-resolution and high-quality image 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 photoreceptor. High density, comparable to the early images,
A copy image of the lowland fog was obtained.

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

[0120]

[Table 5]

It can be seen that the 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).

[0123]

[Table 6]

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

Using the electrophotographic apparatus shown in FIG. 1, a copy test was conducted with the magnetic toner A2 of the present invention. The image density was measured by a reflection densitometer (Macbeth) and evaluated.
As a result, an extremely high-resolution and high-quality image 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 photoreceptor. High density, comparable to the early images,
A copy image of the lowland fog was obtained.

(Embodiment 3) FIG. 2 shows a sectional view of an electrophotographic apparatus of an embodiment of the electrophotographic method of the present invention. The developing method is a one-component developing method. 1 is an organic photoconductor drum in which phthalocyanine is dispersed in a polycarbonate binder resin, 3 is a corona charger for negatively charging the photoconductor,
Reference numeral 4 is a grid electrode for controlling the charging potential of the photoconductor, and 5 is signal light.

The developing device for visualizing the latent image after exposure has a magnetic one-component toner 7, a magnet inside, and a non-magnetic developing sleeve 2 set with a gap between the photosensitive member 1 and the photoconductor 1.
1, a toner popper 20, a rigid toner layer regulating doctor blade 22, and a power source 23 for applying a bias to the developing sleeve 21.

Reference numeral 13 denotes a transfer roller for transferring the toner image on the photoconductor to the paper, which is set so as to come into contact with the photoconductor 1. The transfer roller is an elastic roller in which a conductive elastic member is provided around a shaft made of a conductive metal. The pressing force to the photoconductor 1 is 0 per transfer roller 13 (about 216 mm).
~ 2000g, preferably 500-1000g.
This was measured from the product of the spring coefficient and the contraction amount of the spring for pressing the transfer roller 13 against the photosensitive member 1. The contact width with the photoreceptor is about 0.5 mm to 5 mm. The rubber hardness of the transfer roller 13 is 80 degrees or less by the Asker C measurement method (measurement using a block piece, not the roller shape), and preferably 30 degrees.
-40 degrees.

The outer diameter of the entire transfer roller 13 is 16.4 mm.
The hardness was 40 degrees in Asker C. Transfer roller 1
3 was brought into contact with the photoconductor 1 by pressing the shaft of the transfer roller 13 with a metal spring. The pressing force was about 1000 g. The present invention is not limited to this material.

Reference numeral 14 is a thrusting guide made of a conductive member for introducing the transfer paper to the transfer roller 13, and reference numeral 15 is a conveyance guide in which the surface of the conductive member is covered with an insulating material. The plunge guide 14 and the transport guide 15 are grounded directly or through a resistor. Reference numeral 16 is a transfer sheet, and 17 is a voltage generating power source for applying a voltage to the transfer roller 13.

Reference numeral 18 is a cleaning blade for scraping off the residual toner remaining after transfer, and 19 is a cleaning box for storing the residual toner.

Although an elastic urethane blade was used as the cleaning blade, a fur brush to which a bias was applied,
A similar result is obtained with a conductive metal roller.

The photosensitive member 1 has a diameter of 30 mm and a peripheral speed of 60 m.
It was used by rotating in the direction of the arrow in the figure at m / s. The developing sleeve 21 had a diameter of 16 mm, and was rotated at a peripheral speed of 40 mm / s in the forward direction (the direction of the arrow in the figure) with respect to the traveling direction of the photoreceptor 1. The gap between the photoconductor 1 and the developing sleeve 21 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 1 was −90V. Toner 7 was attached to the electrostatic latent image on the photoconductor 1 to visualize the electrostatic latent image.

The toner image obtained on the photosensitive member 1 is transferred onto a transfer paper by the transfer roller 13 and then heat-fixed by a fixing device (not shown) to obtain a copy image.

A copying test was conducted with the magnetic toner A1 of the present invention using the electrophotographic apparatus shown in FIG. The image density was measured by a reflection densitometer (Macbeth) and evaluated.
As a result, an extremely high-resolution and high-quality image 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. Filming does not occur on the photoconductor. A high-density, low-ground fog copy image comparable to the initial image was obtained.

Example 4 A copying test was conducted using the magnetic toner A2 of the present invention using the electrophotographic apparatus shown in FIG. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, an extremely high-resolution and high-quality image 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. 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 manufactured 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.

[0142]

[Table 7]

Lead oxide titanate fine particles and hydrophobic silica surface-treated with dimethyldichlorosilane were used as external additives.

Using the electrophotographic apparatus 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.

[0147]

[Table 8]

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

Using the electrophotographic apparatus 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 manufactured with the same composition as in Example 1 except that the addition amount of barium titanate fine particles was changed to 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.

[0158]

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,
An electrophotographic method comprising a transfer step using a conductive elastic roller, and a cleaning step, wherein barium titanate fine particles produced by an oxalate thermal decomposition method defined by an average particle diameter and a specific surface area. By containing fine silica powder surface-treated with silicone oil, a highly fluid and highly charged toner can be obtained, and high density, high image quality with low background fog can be achieved in a high performance, small size and low cost development method. it can.

Further, it is possible to provide an electrophotographic method capable of preventing hollow defects during transfer and suppressing the occurrence of toner filming on the photosensitive member.

[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.

FIG. 2 is a sectional view showing a main part of an electrophotographic apparatus in which an electrophotographic method according to an embodiment of the present invention is used.

FIG. 3 is a schematic view of a transfer device.

[Explanation of symbols]

 1 Photoreceptor Drum 2 Fixed Magnet 3 Enclosed in Photoreceptor 3 Corona Charger 4 Grid Electrode 6 Toner Hopper 7 Magnetic Toner 8 Electrode Roller 9 Electrode Roller 9 Magnet Installed Inside Electrode Roller 11 Scraper 13 Transfer Roller 14 Inrush Guide 15 Transport Guide 16 Transfer paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location G03G 9/08 375 (72) Inventor Hideki Tatematsu 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. Within

Claims (13)

[Claims] 1. A developing step of visualizing an electrostatic latent image formed on an electrostatic latent image holder with magnetic toner, and a conductive elastic roller contacting the electrostatic latent image holder, A transfer sheet is inserted between the electrostatic latent image holder and the conductive elastic roller, and the electrostatic latent image on the electrostatic latent image holder is applied by a transfer bias voltage applied to the conductive elastic roller. And a transfer step of transferring the magnetic toner visualized onto the transfer paper, wherein the magnetic toner is composed of at least a binder resin, a magnetic material, and an external additive, and the external additive Is at least a barium titanate fine powder having an average particle size of 0.1 to 4 μm produced by an oxalate pyrolysis method and a BET specific surface area of 0.5 to ²⁰ m ² / g by nitrogen adsorption and nitrogen adsorption. BET specific surface area of 50-350m ² / g
2. An electrophotographic method comprising using a magnetic toner made of negatively charged hydrophobic silica fine powder surface-treated with silicone oil in 1. 2. Barium titanate fine particles having a static bulk density of 0.
The electrophotographic method according to claim 1, wherein a magnetic toner having a weight of 2 to 1.2 g / cm ³ is mixed. 3. The magnetic material comprises 15 to 15 parts by weight of the magnetic toner.
The electrophotographic method according to claim 1, wherein a magnetic toner containing 70% by weight is mixed. 4. A magnetic toner 1 comprising barium titanate fine particles.
The electrophotographic method according to claim 1, wherein 0.1 to 5.0 parts by weight of the magnetic toner is mixed with 100 parts by weight of the magnetic toner. 5. The electrophotographic method according to claim 1, 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. 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 conductive elastic roller that is in contact with the electrostatic latent image holder, and a transfer paper is inserted between the electrostatic latent image holder and the conductive elastic roller. A transfer step of transferring the toner, which visualizes the electrostatic latent image on the electrostatic latent image holder by a transfer bias voltage applied to the conductive elastic roller, to the transfer sheet, and a part of the transfer step during the transfer step. An electrophotographic method comprising at least a cleaning step of removing the toner remaining on the electrostatic latent image carrier from the electrostatic latent image carrier, wherein the magnetic toner is at least a binder resin, a magnetic material, and an external additive. Consists of The external additive is at least barium titanate fine powder having an average particle diameter of 0.1 to 4 μm and a BET specific surface area by nitrogen adsorption of 0.5 to ²⁰ m ² / g, which is produced by an oxalate thermal decomposition method. , BET specific surface area due to nitrogen adsorption is 50 to 350 m ² / g
2. An electrophotographic method comprising using a magnetic toner made of negatively charged hydrophobic silica fine powder surface-treated with silicone oil in 1. 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 mixed. 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. 12. The electrophotographic method according to claim 6, wherein in the transfer step, the elastic member of the elastic roller is a urethane foam to which a conductivity-imparting agent is added. 13. The electrophotographic method according to claim 6, wherein the conductivity-imparting agent dispersedly added to the urethane foam in the transfer step is a lithium salt.