JPH06317933A - Magnetic toner and electrophotographic method - Google Patents

Abstract

PURPOSE:To eliminate the decrease of picture density and the occurrence of white void by using a binder resin of specified copolymer and subjecting a toner fine powder obtd. by kneading and pulverizing a binder resin and magnetic material to surface modifying treatment to perform simultaneously the coating of the magnetic material and the sphering of toner fine powder particles. CONSTITUTION:This magnetic toner consists of a binder resin, magnetic material and external additive. The binder resin consists of copolymers expressed by formula I and formula II and has 1X10<4>-5X10<5> (poise) melt viscosity at 135 deg.C and 3X10<3>-3X10<5> (poise) melt viscosity at 145 deg.C. The binder resin and the magnetic material are kneaded and pulverized to obtain a toner fine powder. The toner fine powder in a dispersed state is treated with hot air for surface modification so that the coating of the magnetic material and the sphering of toner powder particles are simultaneously and instantaneously performed. In formulae, R1 is H or CH3, R2 is H or alkyl group of 1-5 carbon number, and R3 is H or alkyl group of 1-20 carbon number.

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 Conventionally, as electrophotographic methods, there are a cascade developing method, a touchdown developing method, a jumping developing method and the like. 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 an electrophotographic copying machine. Also, there is US Pat. According to the present invention, the AC bias applied to the developing roller is used for the purpose of activating the movement of the toner, and the toner flies to the image portion and returns to the non-image portion in the middle.

Further, as an improvement of the technique of 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, a rigid or elastic regulation blade is installed on the toner carrier with a minute gap between the carrier and the regulation blade to regulate the toner in a thin layer, In this method, the toner is transferred to the developing section, where the toner is attached to the image section of the photoconductor by an AC bias. The technical idea of Japanese Patent Publication No. 63-42256 differs from the above-mentioned US Pat. No. 3,866,574 in that the toner reciprocates in the image portion and the non-image portion.

In order to further miniaturize the development and to improve the image quality, a developing system including a fixed magnet inside the photoconductor, and an electrode roller having a magnet at a position facing the photoconductor with a predetermined gap provided therebetween. Has been proposed to further improve the image quality,
It enables downsizing, simplification of the device, and low cost.

As is well known, 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.

However, in recent years, as the tendency toward higher image quality of copied images and long-term stability of image quality has become remarkable, the binder resin, charge control agent and external additive, which are the main constituent components of the toner, are more than conventional. The charging property and durability of are required. In recent years, reusing toner has been attracting attention from the viewpoint of protecting the global environment.

[0007]

However, with the above-mentioned structure, as is well known in the art, the cascade developing method is not good at reproducing solid images. Further, there is a problem that the device becomes large and complicated. Further, the developing device of US Pat.
There is a drawback that the device requires high accuracy, is complicated, and is expensive. In the jumping development method, it was essential to form a very uniform thin layer on a toner carrier carrying a toner layer. Further, in this method, 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.

Further, the developing method used in the present invention in which the development is made compact and high-performance is composed of an electrode roller having a fixed magnet in the photoconductor and having a magnet at a position facing the photoconductor with a predetermined gap. The development method faithfully reproduces a solid image, does not cause sleeve ghosts, and enables further downsizing, simplification, and cost reduction of the device. Includes aspects that must rely on improved toner properties. Although it is considered that this phenomenon is peculiar to this developing method, since the regulating blade that regulates the toner in a thin layer is not used, the toner jumps into the developing field where the photoconductor and the electrode roller rotate without regulating the layer.
Therefore, the opportunity of charging the toner is small, and the point is how quickly the charging property of the toner can be improved. The fluidity of the toner affects the charge amount. At the level of fluidity of the toner used in conventional one-component development and two-component development, unevenness occurs in solid black image areas and halftone image areas, and background fog increases in non-image areas. is there. This phenomenon remarkably appears in the toner having low fluidity.
This is because a toner with low fluidity has a low probability of contact with the developing member necessary for charging and cannot obtain a sufficient charge amount, and uneven charging occurs between the toners, which makes it impossible to obtain a rapid toner charging property. Is. This is because the toner that retains high fluidity has uniform contact properties and less variation in chargeability.
It is considered that a high charge amount can be obtained and a high quality image can be obtained.

Therefore, a measure taken to increase the fluidity is to increase the addition amount of an external additive such as silica as a fluidity imparting agent. However, if the external additive such as silica is increased, the fluidity is improved, but if it exceeds a certain amount, the fluidity tends to decrease. Further, the amount of suspended silica increases, and this silica serves as nuclei to be driven into the photosensitive member by the pressing force of the cleaning blade to cause scratches, and the suspended silica causes filming on the photosensitive member. In addition, there is a problem that a suspended matter of silica adheres to a solid black portion to generate white spots, and simply increasing the amount of silica causes many problems, and cannot solve the problem.

Further, in a magnetic toner to which a magnetic substance is added, a magnetic substance having a resistance lower than that of the binder resin is exposed on the surface of the toner, so that the charge obtained by frictional charging leaks and a high charge amount can be obtained. It has a difficult drawback. Therefore, attempts have been made to increase the resistance of the magnetic substance by surface-coating the magnetic substance itself with an organic film, but uneven coating, increased cost of the magnetic substance material, and reverse polarity charging tend to occur, and the problem has not been solved. .

In view of the above problems, the present invention is a developing method which can be further downsized, the apparatus can be simplified, and the cost can be reduced.
In addition, the high fluidity and high chargeability of the toner achieves high image quality with high density and low background fog, prevents filming on the photoconductor, is small and has a long life, does not cause toner contamination in the device, and reduces image density. It is an object of the present invention to provide a magnetic toner and an electrophotographic method which have a long life without white spots.

[0012]

In order to solve the above problems, a magnetic toner and an electrophotographic method of the present invention are provided with an electrostatic latent image holder that moves by enclosing a fixed magnet, and the electrostatic latent image holder. A toner reservoir facing the surface of the electrostatic latent image carrier, which is magnetically attracted by the fixed magnet to supply magnetic toner, and is installed at a position having a predetermined gap with the surface of the electrostatic latent image holding member,
In the electrophotographic method including a developing step including an electrode roller having a magnet inside, the magnetic toner is composed of at least a binder resin, a magnetic substance and an external additive, and the binder resin is at least represented by the general formula ), (Chemical Formula 6), and has a melt viscosity at 135 ° C. of 1 × 10 ^{4 to} 5 ×.
10 ⁵ (poise), melt viscosity at 145 ° C. is 3 × 10 ³
The binder resin, the magnetic material, and other additives used as necessary are kneading treatment, pulverization treatment, and, if necessary, a copolymer having a porosity of 3 × 10 ⁵ (poise). Toner fine powder that has been classified and classified is subjected to a surface modification treatment with hot air in a dispersed state to simultaneously coat the magnetic substance and spherical the toner fine powder simultaneously and instantaneously. Is a surface reforming device comprising at least a dispersion spraying means for spraying and dispersing the toner fine powder, and a hot air generating means for emitting the hot air to apply hot air to the toner fine powder sprayed from the dispersion spraying means. Done,
The dispersing / spraying means is a dispersing nozzle that disperses and sprays the toner fine powder with compressed air, and is a magnetic toner that is surface-modified with the hot air temperature of 100 to 600 degrees.

[0013]

[Chemical 5]

[0014]

[Chemical 6]

Further, the electrostatic latent image holding member which moves by enclosing the fixed magnet, the magnetic toner, and the surface of the electrostatic latent image holding member which faces the surface of the electrostatic latent image holding member are magnetically attracted by the fixed magnet to supply the magnetic toner. An electrophotographic method comprising a toner reservoir and a developing step including an electrode roller having a magnet inside, the developing step being installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member. The toner is composed of at least a binder resin, a magnetic substance, and an external additive, and the binder resin is composed of at least one of the general formulas (Chem. 7) and (Chem. 8), and 1
Melt viscosity at 35 ° C. is 1 × 10 ^{4 to} 5 × 10 ⁵ (pois
e) Melt viscosity at 145 ° C. is 3 × 10 ^{3 to} 3 × 10 ^5.
(poise) is a copolymer, and with the binder resin,
The magnetic fine particles and other additives used as necessary are kneaded, pulverized, and further subjected to classification, if necessary, subjected to surface modification treatment with hot air in a dispersed state, The coating of the magnetic material and the spheroidizing of the toner fine powder are simultaneously and instantaneously performed, and the surface modification treatment is performed by at least a dispersion spraying means for spraying the toner fine powder by dispersion, and a spraying means sprayed from the dispersion spraying means. A hot air generating means for radiating the hot air to apply the hot air to the toner fine powder, and the dispersing and spraying means is a dispersing nozzle for dispersing and spraying the toner fine powder by compressed air, This is an electrophotographic method using a magnetic toner that is subjected to surface modification treatment of fine powder at a hot air temperature of 100 to 600 degrees.

[0016]

[Chemical 7]

[0017]

[Chemical 8]

[0018]

According to the present invention, with the above-described structure, the electrostatic latent image holding member including the fixed magnet is used, and the toner is sprinkled and magnetically adhered to the electrostatic latent image holding member 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 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 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 reservoir 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.

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.

In the electrophotographic method according to the present invention, the toner is once attached to the entire surface of the electrostatic latent image holding member, and then the toner in the non-image portion is removed by the electrostatic force and magnetic force by the electrode roller. Therefore, in this method, the charging property and fluidity of the toner are strong and the image properties are affected. When the fluidity is poor, the toner in the non-image area adheres strongly to the electrostatic latent image carrier and cannot be removed, resulting in background fog and degrading the image. Also, when toner is adhered to the entire surface of the electrostatic latent image carrier. It was found that unevenness occurred in the solid image. As the fluidity of the toner is increased (for example, the amount of silica added is increased), the non-electrostatic adhesion force to the electrostatic latent image holding member is reduced, and the background fog is reduced.
Although there is a tendency that the increase in image density and the unevenness of solid black portions are suppressed, the adverse effect of increasing the amount of silica occurs. For example, filming on the photoconductor and adhesion of white spots on the solid black part of silica aggregates.

Further, when the charge amount of the toner decreases, the mirror image force with the electrostatic latent image holding member weakens, the toner attached to the electrostatic latent image holding member is easily removed by the magnetic force, and the image density lowers. It was found that there was a lot of dust around the characters and the sharpness of the image deteriorated.

Further, in order to stabilize the image quality even during long-term use, it is necessary to stabilize the fluidity and charging characteristics of the toner at high values.

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

A known method is used as a method for producing the magnetic toner of the present invention. In the mixing, kneading, crushing and external addition treatments, a classification treatment is carried out if necessary. Other methods such as a polymerization method may also be used. Mixing is a step of uniformly dispersing a binder resin, a magnetic material, and other internal additives such as a charge control agent, a release agent, and a pigment, which are added as necessary, with a mixer equipped with a stirring blade, and a known treatment. A method is used. Then, the step of heating the mixed material to disperse the internal additive in the binder resin by shearing force is kneading. The kneading at this time can be performed using a known heating kneader. As the heating and kneading machine, it is possible to use an apparatus for heating a kneaded material such as a three-roll type, a single-screw type, a twin-screw type, a banbury mixer type, and applying a shearing force to knead the mixture. The agglomerate is roughly crushed by a cutter mill or the like, then finely crushed by a jet mill crusher or the like, and fine powder particles are cut by an airflow classifier if necessary, followed by classification to obtain a desired particle size distribution. Mechanical crushing and classification are also possible. For example, injecting toner into a minute gap between a fixed stator and a rotating roller,
There is a method of crushing. Also in classification, there is a method of classifying by centrifugal force with a rotating rotor. Known methods are used in both cases.

The magnetic toner according to the present invention is subjected to surface modification treatment with hot air after pulverization treatment or, if necessary, classification treatment. In this method, the surface-modifying treatment is performed by dispersing and ejecting the externally added magnetic toner by compressed air from a dispersing nozzle which is a dispersing atomizing means, and radiating hot air heated by a heater which is a hot air generating means. Conventionally, there is an example of applying surface treatment with heat, but a method of supplying toner into the circulating hot air stream and treating it is taken. However, the surface is not uniformly treated. There are also examples in which toner is made spherical by mechanical impact, but noise and vibration are unavoidable due to the fusion of toner particles on the rotating shaft and the presence of a rotating body.

In the magnetic toner according to the present invention, the pulverized or classified toner particles are dispersedly supplied in a hot air stream to melt the surface of the binder resin of the toner particles, and the binder resin instantly forms toner fine particles. The coating of the magnetic material exposed on the surface and the spheroidization of the toner particles are simultaneously performed. When this method is used, since it is a continuous method, production efficiency is improved, and since surface modification is performed in a dispersed state, particles are not bound to each other and coarse particles are not generated. In addition, it has a very simple structure and is compact, the temperature of the machine wall does not rise, the product recovery rate is high, and since it is an open type, there is almost no possibility of dust explosion. Since the toner is instantly treated with hot air, the toner is not aggregated with each other and the entire toner is uniformly treated. Since the corners of the particles generated by the pulverization are cleanly taken and spherical, the fluidity is dramatically improved. The hot air temperature of the treatment at this time is preferably 50 to 600 degrees. When the temperature is 50 degrees or less, the effect of the surface modification treatment cannot be obtained. At 600 degrees or more, aggregation of toners is likely to occur. Further, by using the dispersion nozzle, the dispersibility of the toner can be further improved.

In the magnetic toner according to the present invention, an external additive is externally added to the toner fine powder obtained by the surface modification treatment. A known stirring method using a mixer or the like is used for the external addition treatment.

Further, in the electrophotographic method presented in the present invention, the toner adheres to the entire surface of the photoconductor during development, so that the toner and the photoconductor are in contact with each other longer than in the conventional one-component developing method. Therefore, if a large amount of an external additive (such as silica) is added in order to improve the fluidity of the toner, floating silica is generated, and the filming of the toner on the photoreceptor with the silica as a core is likely to occur. However, in the magnetic toner of the present invention, the external additive which has been subjected to the minimum hydrophobic treatment by the surface modification treatment (in the present invention, hydrophobic silica was used, but other known inorganic fine powder and organic fine powder external additives are used). May be used) to impart a high level of fluidity to the toner. Further, since the toner is spheroidized, silica can be uniformly adhered to the toner during the external addition process, and the amount of floating silica is extremely smaller than that of the toner which is not spheroidized. Therefore, there is no occurrence of scratches or filming on the photoconductor due to the floating silica. The addition amount is preferably 0.5 to 3.0 parts by weight with respect to 100 parts by weight of the magnetic toner. It is necessary to add 0.5 parts by weight or more in order to prevent the toner from aggregating.
If it is more than the weight part, floating silica is generated.

Further, in the toner to which the magnetic substance is added, the magnetic substance is exposed on the surface of the binder resin at the time of pulverization, and since the magnetic substance has conductivity, it is difficult to hold the charge and the toner charge amount is increased. There are difficult drawbacks. It has been found that the surface modification treatment makes it possible to coat the surface of the magnetic material projecting on the toner surface with a binder resin, which has a great effect of increasing the charge amount of the toner.

Further, in the electrophotographic method according to the present invention, a developing method in which the toner layer is not restricted so that the size and weight can be further reduced is used. However, by using the highly charged and highly fluid magnetic toner obtained by the surface modification treatment, High density and high image quality of low ground fog can be obtained.

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

The binder resin of the magnetic toner according to the present invention is a vinyl polymer obtained by polymerizing or copolymerizing vinyl monomers. Examples of the monomer styrene constituting the binder resin include styrene, 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 the 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-based component as a 50-95% 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 binder resin of the magnetic toner according to the present invention has a melt viscosity at 135 ° C. of 1 × 10 ^{4 to} 5 × 10 ⁵ (poi).
se) melt viscosity at 145 ° C. is 3 × 10 ^{3 to} 3 × 10
It is preferably ⁵ (poise). This is related to the surface modification treatment temperature, and the melt viscosity at 135 ° C. is 5 × 10 5.
⁵ (poise), melt viscosity at 145 ° C is 3 × 10 ⁵ (pois)
If it is e) or more, the spheroidization will be weak unless the surface modification treatment temperature is raised to a high temperature, and the coating of the magnetic material will be incomplete. When the processing temperature is increased, power consumption increases, which is uneconomical, and the temperature control of the device becomes unstable. In addition, the resin becomes hard and the pulverizability decreases. On the other hand, when the melt viscosity at 135 ° C. is 1 × 10 ⁴ (poise) or 145 ° C. and the melt viscosity is 3 × 10 ³ (poise) or less, the toner particles are apt to aggregate due to the heat of the surface modification treatment. It is not preferable. Therefore, it was found that when the treatment temperature is lowered, the agglomeration disappears, but the treatment ends when the coating of the magnetic material is halfway and the charging characteristics vary. Further, an offset in which toner adheres to the heat roll is likely to occur during fixing.

At this time, the melt viscosity was measured by using a Koka type flow tester (CFT-500C manufactured by Shimadzu Corporation). The measurement conditions are: die diameter 1 mm, die length 1 mm, load 10 k
gf, temperature rising condition 6 ° C./min.

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, if necessary, in addition to such a main component. . For example, there are polyester resin, epoxy resin, polyurethane resin, and the like.

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

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

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

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 20 to 60% by weight. When the addition amount is 20% by weight or less, the toner scattering tends to increase, and when the addition amount is 60% by weight or more, the toner charge amount tends to decrease and the image quality tends to deteriorate.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the electrophotographic method of the present invention. The developing method is a one-component method. Reference numeral 1 is an organic photoconductor drum in which phthalocyanine is dispersed in polyester binder resin, 2 is a 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, 5 is signal light, 6 is toner reservoir, 7 is a magnetic one-component toner, 8 is a non-magnetic electrode roller set with a gap from the photoconductor 1, and 9
Is a magnet installed inside the electrode roller 8, 10 is an AC high-voltage power supply for applying a voltage to the electrode roller 8, 11 is a scraper made of polyester film for scraping off the toner on the electrode roller, and 12 is a toner image on the photoconductor. It is a transfer corona charger that transfers paper onto paper. Numeral 13 is a damper for smoothing the flow of toner in the toner reservoir and for preventing the toner from being crushed by its own weight and clogged between the photoconductor and the electrode 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
It was used by rotating in the direction of the arrow in the figure at a peripheral speed of 60 mm / s in mm. The diameter of the electrode roller 8 is 16 mm and the peripheral speed is 40 mm.
The photosensitive member was rotated at a speed of mm / s in the direction opposite to the advancing direction of the photoconductor (the direction of the arrow in the figure). The gap between the photoconductor 1 and the electrode roller 8 was set to 300 μm.

The photosensitive member 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. Toner 7 was attached to the surface of the photoreceptor 1 in the toner reservoir 6 by a magnet. Next, the photoconductor 1 was passed in front of the electrode roller 8. When passing through the uncharged area of the photoconductor 1, the AC high voltage power supply 10 is applied to the electrode roller 8
AC voltage of 750V 0-p (peak-to-peak 1.5kV) superposed with 0V DC voltage (frequency 1kHz)
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. 1.5kV)
AC voltage (frequency 1 kHz) 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 attached to the electrode roller 8 rotating in the direction of the arrow was scraped off by the scraper 11 and returned to the toner reservoir 6 again for the next image formation. The toner image thus obtained on the photoconductor 1 is printed on paper (not shown).
After transferring by the transfer charger 12, a fixing device (not shown) heat-fixes it to obtain a copied image.

FIG. 2 shows an outline of a magnetic toner surface modifying apparatus of the present invention. The magnetic toner 22 is introduced from the constant quantity feeder 21 and sent to the dispersion nozzle 24 by the compressed air 23,
Here, it is injected in a direction of about 45 degrees. In the present invention, two dispersion nozzles 24 are arranged at symmetrical positions. This is because the magnetic toner is likely to be processed more uniformly by ejecting from a plurality of nozzles. Since hot air is emitted to the magnetic toner 22 ejected from the dispersion nozzle 24, hot air 26 is emitted from the hot air generator 25. The present invention uses a heater. The device is not limited as long as it can generate hot air. Magnetic toner 22 in hot air 26
Pass through the dispersion, where the surface is modified. The surface-modified magnetic toner is taken into the hood 28, and the arrow 29
Is collected in a cyclone (not shown) in front of.

Next, the material composition and manufacturing method of the magnetic toner will be described. All parts in the examples are% by weight. Only the amount of silica added is shown in parts by weight based on 100 parts by weight of the magnetic toner. Further, all the monomer ratios in the examples are% by weight.

(Example 1) Toner used in Example 1
The material composition of a1 is shown in (Table 1).

[0048]

[Table 1]

The mixture shown in (Table 1) was mixed with a Henschel mixer FM20B (manufactured by Mitsui Miike Co., Ltd.), and the mixture was heated and kneaded by a twin-screw kneading extruder PCM30 (manufactured by Ikegai Tekko Co., Ltd.) and jet mill pulverized. Machine IDS2 (manufactured by Nippon Pneumatic Mfg. Co.)
Fine powder was cut with S2 type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain particles having an average particle size of 8 μm. And Figure 2
The surface modification treatment apparatus shown in FIG. Thereafter, as an external additive treatment, the toner fine powder matrix prepared as described above and the inorganic fine powder of hydrophobic silica were mixed by a Henschel mixer FM20B (manufactured by Mitsui Miike Co., Ltd.) and externally added.

A high fluidity, a high negative charge amount were obtained, and a sharp charge amount distribution was obtained.

The electrophotographic method of the present invention was used to perform a copying test on 10,000 sheets, and the image density was measured with a reflection densitometer (Macbeth Co.) and evaluated. As a result, horizontal lines are not disturbed and toner is not scattered, and the solid is uniform and the density is 1.
An image with an extremely high resolution and high quality was obtained in which the 16 lines / mm of 4 were reproduced. 1.4 reflection density in the initial image
A high-concentration image was obtained, the fog was low, and the internal additives such as the charge control agent and the magnetic material were well dispersed, and no aggregate was observed.

Further, the fluidity of the toner after 10000 sheets is less deteriorated, a high charge amount is maintained, and filming does not occur on the photosensitive member. A high-density copy which was comparable to the initial image was obtained.

Table 2 shows the fluidity of each toner. The fluidity of the initial toner and the waste toner after the 10,000-sheet copying test are shown. Flowability was defined as static bulk density. For the measurement, a powder tester manufactured by Hosokawa Micron was used.

[0054]

[Table 2]

Table 3 shows the image density of each toner in the copy test. The results are shown in the initial stage and after the 10,000-copy test.

[0056]

[Table 3]

(Example 2) Toner used in Example 2
The material composition of a2 is shown in (Table 4).

[0058]

[Table 4]

Toner a2 was prepared and evaluated in the same manner as in Example 1 except that the hot air temperature of the surface modification treatment of the mixture shown in Table 4 was changed to 350 ° C. As a result, a high fluidity and a high negative charge amount were obtained, and a sharp charge amount distribution was obtained.

A copying test was conducted on 10,000 sheets of the electrophotographic method of the present invention, and the image density was measured by a reflection densitometer (Macbeth Co.) and evaluated. As a result, horizontal lines are not disturbed and toner is not scattered, and the solid is uniform and the density is 1.
An image with an extremely high resolution and high quality was obtained in which the 16 lines / mm of 4 were reproduced. 1.4 reflection density in the initial image
A high-concentration image was obtained, the fog was low, and the internal additives such as the charge control agent and the magnetic material were well dispersed, and no aggregate was observed.

Further, the fluidity of the toner after 10000 sheets is little deteriorated, a high charge amount is maintained, and the fluidity of the waste toner is
The amount of charge was almost the same as that of the initial toner, and a high-density copy which was comparable to the initial image was obtained.

(Example 3) Toner used in Example 3
The material composition of a3 is shown in (Table 5).

[0063]

[Table 5]

Toner a3 was prepared and evaluated in the same manner as in Example 1 except that the hot air temperature of the surface modification treatment of the mixture shown in Table 5 was changed to 400 ° C. As a result, extremely high fluidity was obtained with a small amount of added silica, and a sharp negative charge amount distribution was obtained with a high negative charge amount.

A copying test was performed on 10,000 sheets of the image by the electrophotographic method of the present invention, and the image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, horizontal lines are not disturbed and toner is not scattered, and the solid is uniform and the density is 1.
An image with an extremely high resolution and high quality was obtained in which the 16 lines / mm of 4 were reproduced. 1.4 reflection density in the initial image
A high-concentration image was obtained, the fog was low, and the internal additives such as the charge control agent and the magnetic material were well dispersed, and no aggregate was observed.

Further, the decrease in the fluidity of the toner after 10,000 sheets is small, the high charge amount is maintained, and the fluidity of the waste toner is
The amount of charge was almost the same as that of the initial toner, and a high-density copy which was comparable to the initial image was obtained.

(Comparative Example 1) Example 1 having the same material composition as in Example 1 except that the surface modification treatment with hot air was not performed.
Toner b1 was manufactured by the same process as described above.

As a result, the fluidity was low, and as a result of the copy test, a large amount of background fog was generated and a large amount of unevenness was generated in the halftone image, and a practical image could not be obtained. In addition, filming on the photoconductor occurred.

(Comparative Example 2) A toner b2 was prepared in the same manner as in Example 2 except that the surface modification treatment with hot air was performed at 700 ° C. with the same material composition as in Example 2.

As a result, the fusion of the toner and the generation of aggregates were remarkable during the processing, and the productivity could not be endured.

(Comparative Example 3) The same material composition as in Comparative Example 1 except that the amount of silica added was increased to 11.0 parts by weight for the purpose of increasing the fluidity of the toner b1 of Comparative Example 1 to the toner a1 of Example 1. Toner b3 was manufactured by the manufacturing method. However, the fluidity did not increase, and on the contrary, silica suspended matter and aggregates increased, and white spots were generated due to the silica aggregates adhering to the solid black portion, and a practical image could not be obtained. Further, filming on the photoconductor occurred remarkably.

(Comparative Example 4) Toner used in Comparative Example 4
The material composition of b4 is shown in (Table 6).

[0073]

[Table 6]

Toner b4 was prepared from the mixture shown in Table 6 by the same method as in Comparative Example 1 and evaluated. Although the amount of charge control agent added was increased to increase the amount of charge, the charge amount of the toner could not be increased. This is because the dispersibility of the internal additive such as the charge control agent in the resin was poor and a large number of aggregates were observed. Therefore, the distribution of the charge amount became broad and the distribution had two peaks. High fluidity was obtained, but the toner charge amount distribution was non-uniform, the image density was low from the beginning, and there were many background fog. In the copying test, the image density was reduced after about 500 sheets, and a practical image could not be obtained.

(Comparative Example 5) Toner used in Comparative Example 5
The material composition of b5 is shown in (Table 7).

[0076]

[Table 7]

Toner b5 was prepared from the mixture shown in (Table 7) in the same manner as in Example 1. The spheroidizing treatment of the toner and the coating treatment of the magnetic material were insufficient, so that the fluidity was not improved and the charge amount distribution became non-uniform. It is expected that the coating of the magnetic material will remain insufficient. Although the treatment temperature of hot air was set to 650 ° C, agglomeration was partially observed, and other additives were beginning to show thermal damage. Power consumption is high and not practical. Image density is low from the beginning. Practical toner could not be obtained due to a large amount of background fog and poor fixability and pulverizability.

Comparative Example 6 Toner Used in Comparative Example 6
The material composition of b6 is shown in (Table 8).

[0079]

[Table 8]

Toner b6 was prepared from the mixture shown in (Table 8) in the same manner as in Example 1. Agglomeration of toner particles was often observed, and a practical toner could not be obtained. Although the hot air temperature was lowered, agglomeration did not disappear, and the spheroidizing treatment and coating treatment of the magnetic material were insufficient to improve fluidity, resulting in low image density from the beginning. A large amount of background fogging, poor offset property, and excessive pulverization property during pulverization were observed, and a practical toner could not be obtained.

Comparative Example 7 A toner was prepared in the same manner as in Example 1 except that the amount of the magnetic substance added was 10% by weight based on the weight of the magnetic toner. A large amount of toner was scattered and background fog was increased, and a practical image could not be obtained.

Comparative Example 8 A toner was prepared in the same manner as in Example 1 except that the amount of the magnetic substance added was 70% by weight based on the weight of the magnetic toner. The image density was low, the fixability was deteriorated, and a practical image could not be obtained.

[0083]

INDUSTRIAL APPLICABILITY As described above, the present invention provides an electrostatic latent image holding member which includes a fixed magnet and moves, and a predetermined position with respect to the surface of the electrostatic latent image holding member which is opposed to a part of the fixed magnet. The magnetic toner used in an electrophotographic method including a developing process including an electrode roller having a magnet inside, which is installed at a position having a gap of the magnetic toner. The spheroidizing process realizes a developing method that enables further downsizing, simplification of the device, and cost reduction.
Achieve high image quality with low density and high density with magnetic toner that retains high chargeability and high fluidity, small size and long life, no toner contamination in the device, and no filming on the photoreceptor. It is possible to provide a magnetic toner and an electrophotographic method capable of extending the life.

[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 schematic view showing a main part of a magnetic toner surface modifying apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 Photoreceptor Drum 2 Fixed Magnet 3 Enclosed in Photoreceptor 3 Corona Charger 4 Grid Electrode 6 Toner Reservoir 7 Magnetic One-Component Toner 8 Electrode Roller 9 Magnet Installed Inside Electrode Roller 12 Transfer Corona Charger 21 Quantitative Feeder 23 Compressed air 24 Dispersion nozzle 25 Heater 26 Hot air 28 Hood

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 9/08 381

Claims (8)

[Claims] 1. An electrostatic latent image holder that includes a fixed magnet and moves, and a toner reservoir that faces the surface of the electrostatic latent image holder and that is magnetically attracted by the fixed magnet to supply magnetic toner. And a magnetic toner used in an electrophotographic method including a developing step including an electrode roller having a magnet inside, the magnetic toner being installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member. The magnetic toner is composed of at least a binder resin, a magnetic substance and an external additive, and the binder resin is composed of at least one of the general formulas (Formula 1) and (Formula 2), and 1
Melt viscosity at 35 ° C. is 1 × 10 ^{4 to} 5 × 10 ⁵ (pois
e) Melt viscosity at 145 ° C. is 3 × 10 ^{3 to} 3 × 10 ^5.
(poise) is a copolymer, and with the binder resin,
The magnetic fine particles and other additives used as necessary are kneaded, pulverized, and further subjected to classification, if necessary, subjected to surface modification treatment with hot air in a dispersed state, A magnetic toner comprising coating a magnetic material and spheronizing the toner fine powder simultaneously and instantaneously. [Chemical 1] [Chemical 2] 2. A dispersion spraying means for dispersing and spraying fine toner powder in the surface modification treatment, and a hot air generating means for radiating the hot air to apply hot air to the fine toner powder sprayed from the dispersion spraying means. The magnetic toner according to claim 1, wherein the magnetic toner is formed by a surface modification device provided. 3. The hot air temperature for surface-modifying the fine toner powder is 100 ° C. to 600 ° C.
The magnetic toner described. 4. The magnetic toner according to claim 2, wherein the dispersing / spraying means is a dispersing nozzle for dispersing and spraying the toner fine powder by compressed air. 5. An electrostatic latent image holding member that moves by containing a fixed magnet, magnetic toner, and a magnetic toner that is opposed to the surface of the electrostatic latent image holding member and is magnetically attracted by the fixed magnet. An electrophotographic method comprising a toner reservoir to be supplied, and a developing step including an electrode roller having a magnet inside, which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member, The magnetic toner is composed of at least a binder resin, a magnetic material and an external additive, and the binder resin is composed of at least one of the general formulas (Chemical Formula 3) and (Chemical Formula 4), and 1
Melt viscosity at 35 ° C. is 1 × 10 ^{4 to} 5 × 10 ⁵ (pois
e) Melt viscosity at 145 ° C. is 3 × 10 ^{3 to} 3 × 10 ^5.
(poise) is a copolymer, and with the binder resin,
The magnetic fine particles and other additives used as necessary are kneaded, pulverized, and further subjected to classification, if necessary, subjected to surface modification treatment with hot air in a dispersed state, An electrophotographic method characterized by using the magnetic toner, wherein the coating of a magnetic material and the spheroidization of the toner fine powder are simultaneously and instantaneously used. [Chemical 3] [Chemical 4] 6. A dispersion spraying means for dispersing and spraying fine toner powder in the surface modification treatment, and a hot air generating means for emitting hot air to apply hot air to the fine toner powder sprayed from the dispersion spraying means. The electrophotographic method according to claim 5, wherein a magnetic toner produced by a surface modifying apparatus provided therein is used. 7. The hot air temperature for surface modification treatment is 100 to 6 degrees.
The electrophotographic method according to claim 5, wherein a magnetic toner treated at 00 degrees is used. 8. The electrophotographic method according to claim 6, wherein the dispersing / spraying means is a dispersing nozzle for dispersing and spraying the toner fine powder by compressed air.