JP5659847B2 - Method for producing electrophotographic carrier - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic carrier, an electrophotographic carrier, and an electrophotographic developer, and more particularly, to a method for producing an electrophotographic carrier used for forming an electrostatic latent image into a toner image.

  In electrophotographic image formation, an electrostatic latent image is formed by an electrostatic charge on an image carrier such as a photoconductive material, and charged toner particles are attached to the electrostatic latent image to form a visible image. After the toner image is formed, the toner image is transferred to a recording medium such as paper, and the toner image is fixed to form an output image. In recent years, the technology of copiers and printers using an electrophotographic system has been rapidly expanding from monochrome to full color, and the full color market tends to expand.

  Color image formation by full-color electrophotography generally reproduces all colors by laminating three color toners of three primary colors, yellow, magenta, and cyan, or four color toners with black added thereto. . Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the fixed toner image surface to some extent to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines or the like is often 10 to 50% of medium to high gloss.

  In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated and pressed against the toner is frequently used. This method has high thermal efficiency and high-speed fixing, and is advantageous in that it can give gloss and transparency to the color toner. However, the surface of the heat-fixing member is brought into contact with the molten toner under pressure. Since the toner image is peeled from the surface of the post-heating fixing member, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the heat fixing member and is transferred onto another image.

  For the purpose of preventing this offset phenomenon, there is a method in which the surface of the heat fixing member is formed of silicone rubber or fluorine resin having excellent releasability, and further, a release oil such as silicone oil is applied to the surface of the heat fixing member. It was generally adopted. However, this method is extremely effective in preventing toner offset, but a device for supplying release oil is necessary, and the fixing device becomes large and unsuitable for downsizing the machine. For this reason, in a monochrome toner, by adjusting the molecular weight distribution of the binder resin so that the melted toner does not break internally, the viscoelasticity at the time of melting of the toner is increased, and a release agent such as wax is further included in the toner. There is a tendency to employ a method in which the release oil is not applied to the fixing roller (oilless) or the amount of oil applied is very small.

  On the other hand, as for color toners, there is a tendency toward oil-less for the purpose of downsizing machines and simplifying the configuration as in monochrome. However, as described above, in order to improve the color reproducibility of the color toner, it is necessary to smooth the surface of the fixed image, so the viscoelasticity at the time of melting must be lowered, and it is easier to offset than the glossy monochrome toner. Therefore, it is more difficult to make the fixing device oil-free and to apply a small amount. In addition, when a release agent is contained in the toner, the adhesion of the toner is increased and the transfer property to the transfer paper is lowered. Further, the release agent in the toner contaminates the frictional charging member such as a carrier to reduce the charging property. This causes a problem that the durability is lowered.

  Regarding the carrier, while the demand for faster and more beautiful image formation is increasing, the stress received by the developer containing the carrier and the toner has increased dramatically with the recent increase in machine speed. Even with a carrier having a long life, it is difficult to obtain a sufficient life.

  Further, the carrier has been reduced in particle size to achieve high image quality, but although it is highly effective in forming a high-definition image in terms of image quality, it has caused many side effects. One of them is deterioration of storage stability in a high temperature and high humidity environment. The storage stability under this high-temperature and high-humidity environment, especially the deterioration of storage stability under a high-humidity environment is remarkable, and the solidification of the developer (carrier and toner, or carriers, or toners stick together to form a lump) ). For example, when a new developer is set in the developing unit, the developer is usually easily dropped and transferred from the case filled with the new developer to the developing unit, so that the developer can be easily transferred into the developing unit. However, the solidified developer does not fall easily, and the developer does not move into the developing unit, so that there is a problem that it is impossible to draw a picture properly, or even if the developer moves into the developing unit, it is solidified. If a lump remains in the developer, the lump will be caught by a regulating plate that adjusts the amount of developer on the developing roller to a certain amount, which may cause the developer not to be pumped up on the developing roller. An abnormal image may occur. Further, when solidified in the developing unit, or when the developer is charged into the developing unit from the beginning and does not have a case packed with the developer, solidification proceeds to a level that cannot be broken by the stirring blades in the developing unit. Then, problems such as generation of abnormal images and inability to drive occur.

  One of the reasons for this is that the specific surface area of both the carrier and the toner has increased as the particle size has been reduced. In addition to this, the effects of low temperature fixing and oillessness are also considered to be significant. It is done. In addition, the downsizing of the developing unit accompanying the downsizing of the machine in recent years and the difficulty of dropping the developer on the layout make it easy to cause problems when the developer is solidified. Furthermore, with the diversification of the market, it is also necessary for the environment for guaranteeing use to be wider than before, and it is also true that stricter quality is required for the developer.

  In order to solve this problem, Patent Document 1 proposes a method for improving solidification by raising the firing temperature when firing a resin-coated carrier in an electric furnace. Since a blackish color is generated in the resin, a problem of color smearing occurs.

  Thus, solidification of the developer, which has not occurred so far, will be recognized as an important issue in the future. Incidentally, solidification of toner has been conventionally recognized, and examples thereof include Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, and the like. It is not about the solidification of the developer comprising the carrier.

  In order to cope with such a problem, for example, Patent Document 6 and Patent Document 7 propose an electrophotographic carrier in which particles larger than the film are contained in the carrier coating layer. Further, Patent Document 8 proposes a method of performing development while supplying toner and a carrier to the developing device and discharging the excess developer in the developing device.

As for the carrier, while the demand for faster and more beautiful image formation is increasing, the rotation of the developing roller during development is remarkably increased with the recent increase in machine speed, and the centrifugal force applied to the developer is It is increasing. Further, the same is true for high image quality, and the diameters of the carrier and the toner are remarkably reduced.
Therefore, the increase in centrifugal force associated with higher speeds is not affected by the particle size if the carrier magnetization is the same (magnetization per weight is the same), but the toner and carrier diameters are reduced with higher image quality. On the other hand, since the surface area per weight increases as the diameter decreases, the charge amount increases with respect to the magnetization. That is, there is a problem that the carrier becomes weak against the electric force from the photosensitive member, and the carrier is likely to adhere.

However, the effects described in Patent Documents 1 to 8 are insufficient, and the initial carrier adhesion and the time-dependent carrier adhesion, solidification resistance, and color stain resistance in the solid image portion of the developer are insufficient. There is a problem.
The present invention has been made in consideration of the above circumstances, and does not cause initial carrier adhesion and time-dependent carrier adhesion in the solid image portion of the developer, has good solidification resistance, and good color stain resistance. An object is to provide a method for producing an electrophotographic carrier, a carrier, and a developer.

In the method for producing an electrophotographic carrier comprising at least a core material and a coating layer formed on the surface of the core material, the inventors have used an alternating magnetic field from a high frequency induction heating device on the core material coated with the coating material. The present invention finds that the above-mentioned problems can be solved by heating the core material to cause a crosslinking reaction by heating the core material due to core loss (hysteresis loss and eddy current loss). Was completed.
That is, the present invention is as described below.

(1) A method for producing an electrophotographic carrier comprising at least a core material and a coating layer formed on the surface of the core material, the step of coating the core material with a coating material and the heat treatment of the coated material The high-frequency induction heating device per unit mass of the carrier, wherein the high-temperature induction heating device heats the coating material by high-frequency induction heating of the core material. A method for producing a carrier for electrophotography, wherein the electric power E is 0.01 to 2.5 [kWh / kg].
However, the electric power E is a value calculated by the following formula (1).
E = W / M [kWh / kg] (1)
W: Power per hour [kW]
M: Mass of carrier processed per hour [kg / h]
(2) The method for producing an electrophotographic carrier according to (1), wherein an output frequency of the high-frequency induction heating device is 10 to 500 kHz.
(3) The method for producing an electrophotographic carrier according to (1) or (2), wherein an output voltage of the high-frequency induction heating device is 200 to 1500 V.
(4) The method for producing an electrophotographic carrier according to any one of (1) to (3), wherein a holding time of the baking temperature by the high-frequency induction heating device is 0 to 60 minutes.

  According to the method for producing a carrier of the present invention, an electrophotographic carrier having good solid resistance and good color stain resistance is produced without causing initial carrier adhesion and time-dependent carrier adhesion in a solid image of a developer. be able to.

It is a schematic diagram of an example of the high frequency dielectric heating in this invention. It is the schematic of an example of the process cartridge of this invention.

Hereinafter, the present invention will be described in more detail. As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have produced an electrophotographic carrier comprising at least a core material and a coating layer formed on the surface of the core material. A method comprising a step of coating a core material with a coating material and a baking step of heat-treating the coated material, wherein the baking step is performed by high-frequency induction heating of the core material with a high-frequency induction heating device. The power E of the high frequency induction heating device per unit mass of the carrier is 0.01 to 2.5 [kWh / kg] (E = W / M [kWh / kg], W: power per hour [kW], M: mass of carrier processed per hour [kg / h]), it was found that the improvement effect was remarkable.
The electric power E of the high-frequency induction heating device per carrier unit mass in the present invention is, for example, the mass M of the carrier processed per hour at an electric power W = 5.0 [kW] per hour = 6.25 [kg]. / H], a value that can be calculated as E = W / M = 5.0 / 6.25 = 0.80 [kWh / kg].

  That is, in firing by high frequency induction heating, the core material is heated by the loss of the core material (hysteresis loss and eddy current loss) due to the alternating magnetic field generated from the conducting wire through which the high frequency current flows, thereby drying the residual solvent in the coating film. Alternatively, a crosslinking reaction of the coating material is performed. Therefore, high frequency induction heating can raise the temperature of the coating layer of each carrier from the inside. Therefore, when the residual solvent is dried, the solvent can easily escape from the coating layer by starting to dry from the inside. The amount can be kept low. On the other hand, in a conventional baking machine such as an electric furnace or a rotary kiln, heat is applied from the outside of the core material coated with the coating material, so that the coating layer undergoes drying and cross-linking reaction from the outside, so that the residual solvent on the inside escapes. As a result, it is difficult to keep the residual solvent low.

  On the other hand, the same applies to the cross-linking reaction of the coating material. In the firing by high-frequency induction heating, the temperature of the coating layer of each carrier can be raised from the inside, so that equivalent heat enters all the coating layers, It becomes possible to make a carrier particle coating layer into a uniform crosslinking reaction state. On the other hand, in conventional baking machines such as electric furnaces and rotary kilns, heat is applied from the outside of the laminated carrier particles, so that the carrier particles arranged on the side closer to the heat source (outside) have a desired amount of heat exactly. However, it is difficult for heat to be transferred to the carrier particles arranged on the side (inner side) far from the heat source, so that a desired amount of heat cannot be input. Therefore, the variation in the degree of cross-linking across the entire carrier is large, and it is difficult to make all the carrier particle coating layers into a uniform cross-linking reaction state.

  And the residual solvent and uncrosslinked reaction coating material of this coating layer is solidified during storage, especially during storage in a high-humidity environment (a phenomenon in which the carrier and the toner, the carriers adhere to each other, and the toners clump together). This will disadvantageously reduce storage resistance. In addition, in order to improve the storage resistance, conventionally, a means for raising the firing temperature has been taken, but this means for raising the firing temperature is disadvantageous against color stains. In particular, there is a limit in full color. The current situation is that there is no choice but to select a compromise between solidification and color stains.

  In contrast, in the high frequency induction heating of the present invention, as described above, the coating layer can be efficiently dried and the crosslinking reaction can be performed. Therefore, the drying can be performed at a lower firing temperature than in the past. The cross-linking reaction is also the same. Conventionally, since heat is supplied to the particles inside the laminated carrier layer, excessive heat is given to the carrier particles on the surface, but uniform heating by high frequency induction heating is possible. This makes it possible to perform firing at a firing temperature lower than that of the prior art, and is effective against color stains.

  In addition, in the firing by high frequency induction heating, since the coating resin can be dried and in a uniform cross-linking reaction state as described above, the charging sites on the particle surface can be uniformly formed, and therefore, depending on the location on the particle. In addition to improving the uniformity of the charge amount, the uniformity of the charge amount among the particles can also be improved, and the charge amount distribution as carrier particles can be sharpened. As a result, since there are no carrier particles having an extremely high charge amount, no particles are electrically pulled to the photoreceptor side during development, so that it is possible to improve carrier adhesion in the solid image portion at the initial stage.

Furthermore, in firing by high-frequency induction heating, the coating resin can be dried and brought into a uniform crosslinking reaction state as described above, so that a strong resin coating film can be formed, and the film strength depending on the location on one particle In addition to improving the uniformity of the film, it is also possible to improve the uniformity of the film strength between the particles. Accordingly, since the film strength of the entire carrier can be made uniform at a high level, the wear resistance of the carrier can be improved.
Thereby, the carrier adhesion in the solid image portion accompanying the resistance decrease with time can be improved.

When the electric power of the high-frequency induction heating device is increased, the alternating magnetization generated from the conducting wire is increased, and the temperature rising rate of the carrier is increased.
However, when the electric power E of the high frequency induction heating device per unit mass of the carrier exceeds 2.5 [kWh / kg], the carrier is rapidly heated by a large alternating magnetic field generated from the conducting wire through which the high frequency current flows. Causes a decrease in magnetization. The carrier whose magnetization has been lowered cannot resist the electrostatic force and is attracted to the photoconductor, causing carrier adhesion. As a cause of the decrease in the magnetization of the carrier, it is considered that the structure of the core material itself was destroyed and the magnetization decreased due to a rapid temperature increase. Furthermore, since the temperature of the carrier suddenly rises and a large amount of heat (energy) is applied to the coating layer, it is disadvantageous for color stains due to coloring of the coating layer.

On the other hand, when the electric power E of the high frequency induction heating device per unit mass of the carrier is less than 0.01 [kWh / kg], the alternating magnetic field generated from the conducting wire through which the high frequency current flows becomes small, and the temperature can be raised to the firing temperature. Therefore, the crosslinking reaction of the coating material does not proceed sufficiently. Since the crosslinking reaction does not proceed sufficiently, it is disadvantageous for initial carrier adhesion and carrier adhesion over time.
Moreover, the drying property of a residual solvent is also bad and will cause deterioration of solidification resistance. In particular, the power per hour is preferably in the range of 2 to 350 [kW], and more preferably in the range of 2 to 200 [kW]. The range where the power per hour is 2 to 350 [kW] is a preferable range in which the alternating magnetic field generated from the conducting wire through which the high-frequency current flows is an appropriate value, and more preferably within the range of 2 to 200 [kW]. Thus, the coating resin can be dried and brought into a uniform cross-linking reaction state, and the carrier magnetization is not lowered. On the other hand, the mass of the carrier processed per hour is preferably in the range of 1.0 to 400.0 [kg / h], and more preferably in the range of 1.0 to 100.0 [kg / h]. The range of 1.0 to 400.0 [kg / h] of the mass of the carrier processed per hour is a range in which the variation in the degree of crosslinking of the coating material in the entire carrier is small, and further 1.0 to 100 In the range of 0.0 [kg / h], the variation in the degree of crosslinking of the coating material becomes smaller.

The high-frequency induction heating in the present invention is a heating method generally called high-frequency induction heating, induction heating, electromagnetic induction heating, IH (Induction Heating) or the like, and the heating principle is as described above. Since the metal can directly generate heat, the energy efficiency is very high.
FIG. 1 is a diagram schematically showing the state of high-frequency induction heating in the present invention. A high-frequency current supplied from a high-frequency transmitter 3 is passed through a coil 4 to generate an alternating magnetic field, and the coating material 2 is coated with this magnetic field. The core material 1 is repeatedly magnetized to generate heat, and this heat causes the coating material to undergo a crosslinking reaction.

  Solidification in the present invention refers to a phenomenon in which a carrier and toner, carriers and toners adhere to each other and become a lump, and this phenomenon is remarkable in a high temperature and high humidity environment, particularly in a high humidity environment. Further, when the solidification progresses, for example, when the developer is solidified in the developing unit, the solidified lump is developed on the developing roller when the solidification proceeds to a level at which the lump cannot be broken by stirring in the developing unit. Since a portion where the developer is not pumped up is generated on the developing roller by being caught by a regulation plate that adjusts the amount of the agent to a constant amount, an abnormal image such as a white stripe is generated. Furthermore, when the solidification is severe, the developer cannot be destroyed at all by the stirring force in the developing unit, and the situation may be such that stirring is impossible due to insufficient driving force.

Color stains in the present invention mean that when a developer is agitated in a development unit, a small amount of the coating film is scraped off and moves to the toner side and is mixed in the image. The problem is that the range becomes narrower. The scraping of the coating film of the carrier has a great influence on the color even though the amount is very small, and particularly has a great influence on the yellow image. It should be noted here that there is a large difference between the conventional color stain level and the color stain level referred to in the present invention.
More specifically, as the speed increases in recent years, the stress applied to the developer has increased dramatically, and carriers that have conventionally been allowed to have color stains are now unacceptable. In addition, the demand for color has become stricter year by year, while the level of color stain that has been allowed in the past has become unacceptable in recent years.

  Furthermore, it has been found that the improvement effect is remarkable when the output frequency of the high-frequency induction heating apparatus is 10 to 500 kHz. In general, in heating using electromagnetic waves including high-frequency induction heating, the higher the output frequency, the more difficult the energy of electromagnetic waves penetrates into the object to be heated, and the energy of electromagnetic waves concentrates on the surface of the object to be heated. For example, in the case of microwave heating (1,000 to 10,000 MHz), which has a higher frequency than high-frequency induction heating (3 to 300 MHz), the heating rate of the heated object is high for heating the thin heated object. Although it is excellent in efficiency, for the uniform heating of the laminated carrier particles, the energy of electromagnetic waves cannot penetrate into the inside of the carrier particles, and only the carrier particles of a thin surface layer are heated. It is disadvantageous. Furthermore, high-frequency induction heating is induction heating that heats a conductor, and microwave heating is dielectric heating that heats a nonconductor. Therefore, high-frequency induction heating is more efficient when heating a carrier that is a conductor. Can be heated. That is, in the carrier firing (heating), the output frequency range of 10 to 500 kHz is a preferable frequency band in which the carrier heating efficiency and uniform heating properties can be obtained. If the output frequency is less than 10 kHz, the temperature cannot be raised to the firing temperature, and the crosslinking reaction of the coating material does not proceed sufficiently. Furthermore, the drying property of the residual solvent is also bad, and the solidification resistance is deteriorated. On the other hand, when the output frequency exceeds 500 kHz, the carrier particles in the surface layer are remarkably heated, so that the coating material cannot be uniformly promoted to be crosslinked, and the variation in the crosslinking state of the entire carrier becomes large. This is disadvantageous for the initial and aging carrier adhesion.

Furthermore, it has been found that the improvement effect is remarkable when the output voltage of the high-frequency induction heating apparatus is 200 to 1500V. It has been found that the method of gradually raising the temperature to the firing temperature with a small output voltage is advantageous for the drying property of the residual solvent in the coating material. However, in the case of an output voltage of less than 200 V, the alternating magnetic field generated from the conducting wire through which the high-frequency current flows becomes small, so that the temperature cannot be raised to the firing temperature as described above, and the crosslinking reaction of the coating material does not proceed sufficiently. Since the crosslinking reaction does not proceed sufficiently, it is disadvantageous for initial carrier adhesion and carrier adhesion over time. Moreover, the drying property of a residual solvent is also bad and will cause deterioration of solidification resistance.
On the other hand, in the case of a voltage exceeding 1500 V, the carrier is rapidly heated by the large alternating magnetic field generated from the conducting wire through which the high-frequency current flows as described above, thereby causing a decrease in the magnetization of the carrier and causing carrier adhesion. Become.

Furthermore, it has been found that the improvement effect is remarkable when the holding time of the firing temperature by the high-frequency induction heating apparatus is 0 to 60 minutes. There is a heat amount (energy) necessary for crosslinking the coating material, and by adjusting the holding time of the firing temperature, a heat amount (energy) for crosslinking the coating material of the carrier is given, and the crosslinking reaction is sufficiently performed. be able to. If the crosslinking reaction of the coating material does not proceed sufficiently, the solidification resistance will be deteriorated. Furthermore, by providing the holding time, the variation in the degree of cross-linking of the entire carrier is reduced, which is advantageous for adhesion of the carrier over time. However, if the holding time exceeds 60 minutes, an excessive amount of heat (energy) is applied to the coating layer of the carrier, which causes color stains due to coloring of the coating layer.
The firing temperature can be appropriately set depending on the coating material.

Examples of the coating material include a resin, a resin crosslinking agent, a charge control agent, and inorganic fine particles.
Examples of the resin used for the coating material in the present invention include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene, polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, Polyvinyl and polyvinylidene resins such as polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polybiliketone, etc., vinyl chloride-vinyl acetate copolymer, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychloro Fluoroethylene such as trifluoroethylene, polyamide, polyester, polyurethane, polycarbonate, urea-formaldehyde resin, epoxy resin, silica Various thermoplastic resins and thermosetting resins such as carbon resins, urethane / urea resins, polyethylene resins, Teflon (registered trademark) resins, and mixtures thereof, and copolymers and block polymers of these resins , Graft polymers, polymer blends, and the like, but are not limited thereto.

  In the present invention, an amino resin can be used as a resin crosslinking agent. As the amino resin, any amino resin can be used, but the use of guanamine or melamine significantly improves the charge imparting ability. In addition to the resins listed here, any of those commonly used as carrier coating resins can be used, such as polystyrene resins, poly (meth) acrylic resins, polyolefin resins, polyamides. Resin, polycarbonate resin, polyether resin, polysulfinic acid resin, polyester resin, epoxy resin, polybutyral resin, urea resin, urethane / urea resin, silicon resin, polyethylene resin , Various thermoplastic resins such as Teflon (registered trademark) resins and thermosetting resins and mixtures thereof, and copolymers, block polymers, graft polymers and polymer blends of these resins. It is not limited.

Examples of the charge control agent include a silane coupling agent and a titanium coupling agent. For example, the silane coupling agent is a compound represented by the following general formula.
YRSiX ₃
X represents a hydrolyzable group bonded to a silicon atom, such as a chloro group, an alkoxy group, an acetoxy group, an alkylamino group, or a propenoxy group. Y is an organic functional group that reacts with the organic matrix and is a vinyl group, a methacryl group, an epoxy group, a glycidoxy group, an amino group, a mercapto group, or the like. R is a C1-C20 alkyl group or alkylene group.
Further, among silane coupling agents, an aminosilane coupling agent having an amino group in Y is preferable in order to obtain a developer having negative chargeability. In order to obtain a developer having positive chargeability, an epoxy group is present in Y. The epoxy silane coupling agent which has is preferable.

  In the present invention, particles can be contained in the coating layer. Examples thereof include inorganic oxide fine particles such as silica, titanium oxide, alumina, zinc oxide, and tin oxide, and organic resin fine particles such as phenol resin and melamine resin, but are not limited to these examples. Further, the surface of the particle base material may be subjected to a hydrophilic treatment, a hydrophobic treatment, a low resistance treatment, or the like, and is not limited to these examples. The particle size is not particularly limited, but in order to retain the particles over a long period of time, it is desirable that the particles completely enter the coating layer or be within 3 times the average thickness of the coating layer, Preferably it is 0.01-1 micrometer, More preferably, it is 15-0.5 micrometer, However, It is not limited to this. Further, the content of the particles is not easily determined because of the balance between the quality and the coating resin, but is preferably 10 to 90% by weight, more preferably 40 to 80% by weight, but is not limited thereto. Absent.

  In the present invention, a diluting solvent can be used in order to easily form the coating liquid on the core material. By using this diluting solvent, not only can the viscosity of the coating liquid be properly controlled, but also the drying speed, surface tension, and the like can be controlled, so that the film formation state of the coating layer can be arbitrarily controlled. The type of the dilution solvent is not particularly limited, and may be arbitrarily selected from the type of coating solution and the desired film formation state. For example, water, tetrahydrofuran, methanol, ethyl acetate, methyl ethyl ketone, ethyl cellosolve , Butyl cellosolve, toluene, isoparaffinic hydrocarbons (IP solvent, IP clean), isopropyl alcohol, neocol, etc. are useful, but not limited thereto.

  The carrier core material particles of the present invention are heated by high frequency induction heating, and a magnetic core material or eddy current flows in or between the core materials due to the above heating principle. For example, as known two-component carriers for electrophotography, iron, ferrite, magnetite, hematite, cobalt, iron-based, magnetite-based, Mn-Mg-Sr-based ferrite, Mn-based ferrite, Mn-Mg ferrite, Li-based ferrite Mn—Zn based ferrite, Cu—Zn based ferrite, Ni—Zn based ferrite, Ba based ferrite, and the like may be appropriately selected according to the use and purpose of use of the carrier, and are not limited to the above examples. The particle size of the carrier core particles is not particularly limited, but is preferably 10 to 100 [μm], more preferably 20 to 60 [μm].

Next, an example of a method for producing the electrophotographic carrier of the present invention will be described.
The method described below is merely an example of a number of carrier manufacturing methods, and the carrier manufacturing method of the present invention is not limited to the following exemplified methods.
First, the major flow of the carrier manufacturing method is as described below.
[Raw material measurement] ⇒ [Coating liquid dispersion] ⇒ [Coating layer coating] ⇒ [Firing] ⇒ [Crushing]
That is, first, a raw material is weighed in a desired ratio and subjected to a dispersion process by a disperser. The disperser used here may be any commonly used disperser, such as a homomixer, a blade rotating disperser (Ebara Milder, Cavitron, etc.), a bead mill, and the like. A machine may be used as appropriate. The dispersion thus obtained is coated on the surface of the core material by a coating apparatus. The coating apparatus used here may be any coating apparatus that is generally used, and examples thereof include a rolling fluidized bed using a spray and a method of immersing the core material in the dispersion and drying the solvent. Then, the coating layer of the coated particles is baked to advance the drying and crosslinking reaction. As a baking apparatus used here, baking is performed under specific conditions using a high-frequency induction heating apparatus. Finally, crushing is performed to break up the agglomerated particles by firing. The crusher used here may be anything as long as the particles can be broken into one particle, but generally a sieve device is often used, and examples thereof include a vibrating sieve and an ultrasonic vibrating sieve. Furthermore, when this sieving apparatus is used, not only the aggregation of particles but also the removal of coarse particles and the removal of foreign substances can be performed at the same time, which is very efficient.
The particles thus obtained are carrier particles referred to in the present invention, but only one of the production methods is illustrated here, and the present invention is not limited to the contents described here.

The developer of the present invention contains the carrier of the present invention and a toner.
The color toner referred to in the present invention includes not only a color toner generally used for a single color, but also black toner in addition to yellow, magenta, cyan, red, green, blue and the like used for full color. Furthermore, the toner referred to in the present invention may be a general toner regardless of whether it is a monochrome toner, a color toner, or a full color toner. For example, conventionally kneaded and pulverized toners and various polymerized toners that have been used in recent years can be used.

  Furthermore, a toner containing a release agent, so-called oilless toner can also be used. In general, oilless toner contains a release agent, so that the release agent is likely to be transferred to the carrier surface, and so-called spent is likely to occur. Quality can be maintained. In particular, oilless full color toners are generally said to be spent easily because the binder resin is soft, but it can be said that the carrier of the present invention is very suitable.

  As the binder resin used in the toner according to the present invention, known resins can be used. For example, styrene such as polystyrene, poly-p-styrene, and polyvinyltoluene, and homopolymers thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene- Methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid copolymer Corp., Styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid Butyl copolymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene-isopropyl copolymer, styrene-male Styrene copolymers such as acid ester copolymer, polythyme methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified Rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination.

  Furthermore, as the pressure fixing binder resin, known resins can be mixed and used. For example, polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-chlorinated Vinyl copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin, epoxy resin, polyester resin, styrene-butadiene copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride, maleic acid modified phenol resin Phenol-modified terpene resins and the like can be used alone or in combination, but are not limited thereto.

  The toner used in the present invention may contain a release agent in addition to the binder resin, the colorant, and the charge control agent. Accordingly, it can be used in a fixing system in which toner fixing prevention oil is not applied to the fixing roll, so-called oilless system. A well-known thing can be used as a mold release agent. For example, polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin waxes, amide waxes, polyhydric alcohol waxes, silicone varnishes, carnauba waxes and ester waxes can be used, but are not limited thereto.

  As the colorant used in the toner such as the color toner of the present invention, known pigments and dyes capable of obtaining yellow, magenta, cyan, and black toners can be used, and are not limited to those listed here. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C. I. And CI Pigment Yellow 180.

  Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

  Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC.

Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.
Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides.
Moreover, these colorants can use 1 type (s) or 2 or more types.

  The toner such as the color toner of the present invention may contain a charge control agent in the toner as necessary. For example, nigrosine, an azine dye containing an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627), a basic dye (for example, CI Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C. I. Basic Red 1 (C.I. 45160), C. I. Basic Red 9 (C.I. 42500), C. I. Basic Violet 1 (C.I. 42535), CI Basic Violet 3 (C.I. 42555), C.I.Basic Violet 10 (C.I.45170), C.I.Basic Violet 14 (C.I. 42510), C.I.Basic Violet Blue 1 (C.I. 42025), C.I.Basic Blue 3 (C.I. 51005), C.I. Basic Blue 5 (C.I. 42140), CI Basic Blue 7 (C.I. 42595), C.I.Basic Blue 9 (C.I. 522015), C.I.Basic Blue 24 ( CI Basic Blue 25 (C.I.52025), C.I.Basic Blue 26 (C.I.44045), C.I.Basic Green 1 (C.I.42040) CI Basic Green 4 (CI 42000) and other basic dye lake pigments, CI Solvent Black 8 (CI 26150), benzoylmethylhexadecyl ammonium chloride, decyltrimethyl Quaternary ammonium salts such as chloride, or dibutyl or dichlor Polyamine resins such as dialkyltin compounds, such as dialkyltin compounds, dialkyltinborate compounds, guanidine derivatives, vinyl polymers containing amino groups, condensation polymers containing amino groups, JP-B-41-20153, JP-B-43-27596 No. 44, Japanese Patent Publication No. 44-6397, Japanese Patent Publication No. 45-26478, metal complexes of monoazo dyes, Japanese Patent Publication No. 55-42752, Japanese Patent Publication No. 59-7385, and salicylic acid , Metal complexes of dialkyl salicylic acid, naphthoic acid, dicarboxylic acid such as Zn, Al, Co, Cr, Fe, sulfonated copper phthalocyanine pigment, organic boron salts, fluorine-containing quaternary ammonium salts, calixarene compounds, etc. It is done. Naturally, color toners other than black should avoid the use of charge control agents that impair the target color, and white metal salts of salicylic acid derivatives are preferably used.

  As for the external additive, transferability and durability are further improved by externally adding inorganic fine particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride and resin fine particles to the base toner particles. This effect can be obtained by covering the wax that lowers transferability and durability with these external additives and reducing the contact area due to the toner surface being covered with fine particles. The surface of these inorganic fine particles is preferably subjected to a hydrophobic treatment, and metal oxide fine particles such as silica and titanium oxide subjected to the hydrophobic treatment are preferably used. As the resin fine particles, polymethyl methacrylate or polystyrene fine particles having an average particle size of about 0.05 to 1 μm obtained by a soap-free emulsion polymerization method are suitably used.

In addition, the combination of hydrophobized silica and hydrophobized titanium oxide increases the amount of hydrophobized titanium oxide externally added compared to the amount of hydrophobized silica externally charged. The toner can also be excellent in stability. In combination with the above-mentioned inorganic fine particles, silica having a specific surface area of 20 to 50 m ² / g or resin fine particles having an average particle diameter of 1/100 to 1/8 of the average particle diameter of the toner can be used. The durability can be improved by externally adding an external additive having a particle size larger than that of the additive to the toner.

  This is because the metal oxide particles externally added to the toner tend to be embedded in the base toner particles in the process where the toner is mixed and stirred with the carrier in the developing device, charged, and used for development. This is because it is possible to prevent the metal oxide fine particles from being embedded by externally adding an external additive having a particle size larger than that of the oxide fine particles to the toner.

  The above-mentioned inorganic fine particles and resin fine particles are contained (internally added) in the toner, but the effect is reduced as compared with the case of external addition, but the effect of improving transferability and durability can be obtained and the pulverization property of the toner can be improved. Can do. In addition, since external addition and internal addition can be used together to suppress embedding of externally added fine particles, excellent transferability can be stably obtained and durability can be improved.

  In addition, the following are mentioned as a typical example of the hydrophobization processing agent used here. Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyl-tris (β-methoxyethoxy) ) Silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyl Trichlorosilane, decyl-trichlorosilane, nonyl-trichlorosilane, (4-t-propylphenyl) -trichlorosilane, (4-t-butylphenyl) -trichlorosilane, diventyl-dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl -Dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, dihexadecyl-dichlorosilane, (4-t-butylphenyl) -octyl-dichlorosilane, dioctyl-dichlorosilane, didecenyl-dichlorosilane, dinonenyl-dichlorosilane, di-2-ethylhexyl-dichlorosilane, di- 3,3-dimethylbenthyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-chlorosilane, tridecyl-chlorosilane Dioctyl-methyl-chlorosilane, octyl-dimethyl-chlorosilane, (4-t-propylphenyl) -diethyl-chlorosilane, octyltrimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilazane, hexaphenyldisilazane , Hexatolyl disilazane and the like. In addition, titanate coupling agents and aluminum coupling agents can also be used. In addition, as an external additive for the purpose of improving cleaning properties, a lubricant such as a fatty acid metal salt or a fine particle of polyvinylidene fluoride can be used in combination.

  A conventionally known method such as a pulverization method or a polymerization method can be applied to the production of the toner in the present invention. For example, in the case of the pulverization method, as a device for kneading the toner, a batch type two roll, a Banbury mixer or a continuous twin screw extruder, for example, KTK type twin screw extruder manufactured by Kobe Steel, TEM manufactured by Toshiba Machine Co., Ltd. Type twin screw extruder, KCK twin screw extruder, Ikegai Iron Works PCM type twin screw extruder, Kurimoto Iron Works KEX type twin screw extruder, continuous single screw kneader, for example Buss Co-kneader is preferably used.

  The melt-kneaded product obtained as described above is cooled and then pulverized. For pulverization, for example, coarsely pulverized using a hammer mill, a funnel plex or the like, and further, a fine pulverizer using a jet stream or mechanical pulverization A machine can be used. The pulverization is desirably performed so that the average particle diameter is 3 to 15 μm. Furthermore, it is preferable that the particle size of the pulverized product is adjusted to 5 to 20 μm by a wind classifier or the like.

  Subsequently, the external additive is externally added to the base toner. The base toner and the external additive are mixed and stirred using a mixer, and the external additive is crushed and coated on the toner surface. At this time, it is important in terms of durability that external additives such as inorganic fine particles and resin fine particles are uniformly and firmly attached to the base toner. The above is only an example, and the present invention is not limited to this.

  In the developer of the present invention, the content of the carrier in the developer is not particularly limited and can be appropriately selected according to the purpose. For example, 90 to 98% by mass is preferable, and 93 to 97% by mass is preferable. More preferred.

FIG. 2 shows the configuration of the process cartridge of the present invention. In FIG. 2, the process cartridge includes a latent image carrier (photoconductor), a charging unit, a developing unit, and a cleaning unit.
In the present invention, among the components such as the latent image carrier, the charging unit, the developing unit, and the cleaning unit, at least the latent image carrier and the developing unit are integrally coupled as a process cartridge. Is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer. At this time, in the developing device, development is performed using the developer of the present invention.

  Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these.

[Example 1]
・ Acrylic resin solution (solid fraction: 50 mass%) 70 mass parts ・ Guanamine solution (solid fraction: 70 mass%) 20 mass parts ・ Acid catalyst (solid fraction; 40 mass%) 1 mass part ・ Silicone resin solution (Solid fraction: 20% by mass) 350 parts by mass Aminosilane (solid fraction: 100% by mass) 5 parts by mass Conductive treated titanium oxide particles (surface: ITO treatment, primary particle size: 50 nm,
Volume resistivity: 1.0 × 10 ² Ω · cm) 165 parts by mass 700 parts by mass of toluene was dispersed with a homomixer for 10 minutes to prepare a coating layer forming solution.

  Next, an average particle diameter of 35 μm sintered ferrite powder [DFC-400M (Mn ferrite, manufactured by DOWAIP Creation Co., Ltd.)] was used as the core material particles, and the coating film forming solution was coated on the surface of the core particles with a film thickness of 0.3 μm. Then, it was applied with a Spira coater (Okada Seiko Co., Ltd.) at a coater temperature of 60 ° C. and dried.

  The coated carrier thus obtained is allowed to stand inside a three-winding coil having a hollow conductor wire diameter of 6 mm, the power W per hour is 40.0 [kW], and the mass M of the carrier processed per hour is M = 50.0 [ kg / h], the electric power E = 0.80 [kWh / kg] of the high frequency induction heating device per unit mass of the carrier, the output frequency of 480 [kHz], and the output voltage of 220 [V] are caused to flow through the conductor. Firing was performed at a product temperature of 160 ° C. and a holding time of 0 minutes. The hollow conductor has a thickness of 1 mm and an inner diameter of 4 mm, and the temperature of the conductor is increased by a high-frequency induced current flowing in the conductor. Therefore, cooling water was allowed to flow inside the conductor to cool this heat. In addition, EKOHEAT made by AMBRELL was used as the transmitter of the high frequency induced current. The carrier thus fired was cooled and then crushed using a sieve having an aperture of 63 μm to obtain [Carrier 1].

On the other hand, toner
Binder resin: 100 parts by weight of polyester resin Release agent: 5 parts by weight of carnauba wax Charge control agent: E-84 [manufactured by Orient Chemical Co., Ltd.] 1 part by weight Colorant: C.I. I. P. Y. 180 8 parts by mass Of the above materials, the colorant, the binder resin, and pure water were mixed at a ratio of 1: 1: 0.5 and kneaded by two rolls. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch in advance. Using the master batch obtained in this way, weigh the materials so that they are the same as the above recipe, mix with a Henschel mixer, melt knead for 40 minutes at 120 ° C. with two rolls, cool, and then coarsely pulverize with a hammer mill Thereafter, fine powder obtained by fine pulverization with an air jet pulverizer was classified to prepare toner base particles having a weight average particle diameter of 5 μm.

Further, to 100 parts of the toner base material, 1 part of silica whose surface was hydrophobized and 1 part of titanium oxide whose surface was hydrophobized were added and mixed with a Henschel mixer to obtain yellow toner [Toner 1 ] Was obtained.
7 parts by mass of [Toner 1] thus obtained and 93 parts by mass of [Carrier 1] were mixed and stirred to prepare a developer having a toner concentration of 7% by mass.

[Example 2]
In Example 1, the mass M of carrier processed per time is equal to 50.0 [kg / h], and the electric power per time is changed to W = 1.50 [kW]. [Carrier 2] was obtained in the same manner except that the electric power E of the high frequency induction heating apparatus was changed to 0.03 [kWh / kg]. A developer was prepared in the same manner as in Example 1 using [Carrier 2] and [Toner 1] thus obtained.
Example 3
In Example 1, the mass M of the carrier processed per time is equal to 50.0 [kg / h], and the power per time is changed to W = 115 [kW], so that the high frequency per carrier unit mass is obtained. [Carrier 3] was obtained in the same manner except that the electric power E of the induction heating apparatus was changed to 2.30 [kWh / kg]. A developer was prepared in the same manner as in Example 1 using [Carrier 3] and [Toner 1] thus obtained.

Example 4
In Example 1, the electric power E = 0.80 [kWh / kg] of the high-frequency induction heating device per unit mass of the carrier is similarly changed to a carrier in the same manner except that the output frequency is changed to 5.0 [kHz]. [Carrier 4] was obtained. Using [Carrier 4] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
Example 5
In Example 1, the electric power E = 0.80 [kWh / kg] of the high-frequency induction heating device per unit mass of the carrier is similarly changed to a carrier in the same manner except that the output frequency is changed to 30.0 [kHz]. [Carrier 5] was obtained. A developer was prepared in the same manner as in Example 1 using [Carrier 5] and [Toner 1] thus obtained.

Example 6
In Example 1, the electric power E = 0.80 [kWh / kg] of the high-frequency induction heating device per unit mass of the carrier is similarly changed to a carrier in the same manner except that the output frequency is changed to 520.0 [kHz]. [Carrier 6] was obtained. Using [Carrier 6] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.

Example 7
In Example 1, since the output voltage was changed to 180 [V], the electric power W per hour was 32.7 [kW], and thus the electric power of the high-frequency induction heating device per carrier unit mass was changed to the same E = In order to obtain 0.80 [kWh / kg], the carrier is processed in the same manner except that the mass of the carrier processed per hour is changed to M = 40.9 [kg / h] to obtain [Carrier 7]. It was. A developer was prepared in the same manner as in Example 1 using [Carrier 7] and [Toner 1] thus obtained.
Example 8
In Example 1, since the output voltage was changed to 1480 [V], the electric power W per hour was 269 [kW], and thus the electric power of the high-frequency induction heating device per carrier unit mass was the same as E = 0. In order to obtain 80 [kWh / kg], a carrier was formed in the same manner except that the mass of the carrier processed per hour was changed to M = 336 [kg / h] to obtain [Carrier 8]. A developer was prepared in the same manner as in Example 1 using [Carrier 8] and [Toner 1] thus obtained.
Example 9
In Example 1, since the output voltage was changed to 1520 [V], the electric power W per hour was 276 [kW]. Therefore, the electric power of the high frequency induction heating device per unit mass of the carrier was similar to E = 0. In order to obtain 80 [kWh / kg], the carrier was processed in the same manner except that the mass of the carrier processed per hour was changed to M = 345 [kg / h] to obtain [Carrier 9]. A developer was prepared in the same manner as in Example 1 using [Carrier 9] and [Toner 1] thus obtained.

Example 10
In Example 1, except that the holding time was changed to 50 [min], the carrier was formed in the same manner to obtain [Carrier 10]. Using [Carrier 10] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
Example 11
In Example 1, except that the holding time was changed to 70 [min], a carrier was formed in the same manner to obtain [Carrier 11]. Using [Carrier 11] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
Example 12
In Example 1, except that the holding time was changed to 30 [min], the carrier was formed in the same manner to obtain [Carrier 12]. A developer was prepared in the same manner as in Example 1 using [Carrier 12] and [Toner 1] thus obtained.

Example 13
In Example 1, a carrier was obtained in the same manner except that the product temperature was 200 ° C. and the coating formulation for coating layer formation was changed as follows to obtain [Carrier 13]. Using [Carrier 13] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
-Silicone resin solution (solid content: 20% by mass) 597 parts by mass-Aminosilane (solid content: 100% by mass) 5 parts by mass-Conductive-treated titanium oxide particles (surface: ITO treatment, primary particle size: 50 nm,
Volume resistivity: 1.0 × 10 ² Ω · cm) 165 parts by mass Toluene 700 parts by mass [Example 14]
In Example 1, carrier temperature was obtained in the same manner except that the product temperature was 180 ° C. and the coating formulation for coating layer formation was changed as follows to obtain [Carrier 14]. A developer was prepared in the same manner as in Example 1 using [Carrier 14] and [Toner 1] thus obtained.
・ Acrylic resin solution (solid content ratio: 50 mass%) 169 mass parts ・ Guanamine solution (solid content ratio; 70 mass%) 48 mass parts ・ Acid catalyst (solid content ratio; 40 mass%) 2.5 mass parts ・ Aminosilane (Solid fraction: 100% by mass) 5 parts by mass Conductive treated titanium oxide particles (surface; ITO treatment, primary particle size; 50 nm,
Volume resistivity: 1.0 × 10 ² Ω · cm) 165 parts by mass Toluene 700 parts by mass

[Comparative Example 1]
In Example 1, the mass M of carrier processed per time is equal to 50.0 [kg / h], and the electric power per time is changed to W = 0.40 [kW]. [Carrier 15] was obtained in the same manner except that the electric power E of the high-frequency induction heating apparatus was changed to 0.008 [kWh / kg]. A developer was prepared in the same manner as in Example 1 using [Carrier 15] and [Toner 1] thus obtained.
[Comparative Example 2]
In Example 1, the mass M of carrier processed per time is equal to 50.0 [kg / h], and the power per time is changed to W = 135 [kW]. [Carrier 16] was obtained in the same manner except that the electric power E of the induction heating apparatus was changed to 2.70 [kWh / kg]. Using [Carrier 16] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.

[Comparative Example 3]
In Example 1, the baking method is changed from high frequency induction heating to microwave heating, and the power E of the microwave heating apparatus per unit mass of the carrier in the microwave heating apparatus (microwave batch type oven manufactured by Microelectronics Co., Ltd.) Firing was performed at 0.08 [kWh / kg], an output frequency of 2450 [MHz], an output voltage of 220 [V], and a product temperature of 160 ° C. Thereafter, the carrier was formed in the same manner as in Example 1 to obtain [Carrier 17]. Using [Carrier 17] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
[Comparative Example 4]
In Example 1, the baking method was changed to high-frequency induction heating to an electric furnace, and baked in an electric furnace at a product temperature of 160 ° C. for 60 [min]. Thereafter, the carrier was formed in the same manner as in Example 1 to obtain [Carrier 18]. Using [Carrier 18] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.
[Comparative Example 5]
In Example 1, the baking method was changed to high-frequency induction heating to an electric furnace, and baked in an electric furnace at a product temperature of 180 ° C. for 60 [min]. Thereafter, the carrier was formed in the same manner as in Example 1 to obtain [Carrier 19]. Using [Carrier 19] and [Toner 1] thus obtained, a developer was prepared in the same manner as in Example 1.

Using the developers prepared in Examples 1 to 14 and Comparative Examples 1 to 5, evaluation of initial carrier adhesion and time-dependent carrier adhesion, solidification resistance, and color stain resistance in the solid image portion of the developer Carried out. The evaluation results are shown in Table 1.
In addition, the measuring method of the physical-property value of the carrier obtained in the Example and the comparative example and the evaluation method regarding the said evaluation item of a carrier followed the following.

[Early carrier adhesion evaluation method]
The developer was set on a commercially available digital full-color printer (Rigoh Co., Ltd., imagio MP C5000) modified machine, and solid carrier adhesion of the initial developer was evaluated. In the evaluation method, the background potential was fixed at 150 V using the copying machine, and the solid image on the entire surface of the A3 sheet was developed and fixed continuously from the first sheet to the tenth sheet after the developer was set. By observing the solid image thus obtained with a magnifying glass, the number of white spots and the number of carriers actually attached were counted, and the total number was defined as the number of carriers attached to the image. Further, the average of the total number of the evaluated 10 images is defined as the initial carrier adhesion number in the developer. The case where the number is 0 is ◎, the case where it is 1 to 7 is ◯, and the case is 8 to 15 A case was judged as Δ, a case of 16 or more was judged as ×, ◎, ○, and Δ were passed, and × was rejected.

[Method of evaluating carrier adhesion over time]
The developer was set on a commercially available digital full-color printer (Imagio MP C5000, manufactured by Ricoh Co., Ltd.), and a running evaluation of 300,000 sheets in a single color was performed. Then, the solid carrier adhesion of the developer after the running was evaluated.
The solid image carrier adhesion evaluation method was evaluated by fixing the background potential to 150 V using the copying machine, developing a solid image on A3 size paper, and observing with a magnifying glass. ◎ when the number of white spots on the image and the total number of carriers actually attached are 0, ◯ when 1-5, △, 11 when 6-10 The case of more than one was determined as x, ×, ○, △ were accepted, and x was rejected.

[Method of evaluating solidification resistance]
In order to confirm the degree of solidification of the developer in the developing unit, evaluation is performed using an A4 halftone solid image. When the solidification state is poor, a developer lump is clogged behind the developing unit doctor blade and streaks are generated in the image, resulting in a defective image.
The evaluation method is that the developer is set in a developer hopper of a modified development unit of a commercially available digital full-color printer (IPSiO CX 8200 manufactured by Ricoh Co., Ltd.) with a seal so that the developer does not fall into the stirring section. In the state set, the sample was put into an environmental test room at 55 ° C. and 95% RH and stored for 48 hours. As a precaution, it is necessary to adjust the temperature and humidity to 55 ° C. and 95% RH while gradually raising the temperature and humidity in order to prevent dew condensation when it is put into the environmental test room. When the storage for 48 hours was completed, the sample was taken out in a room temperature environment and allowed to stand for 2 hours or more to return to room temperature and humidity. As a precaution in this case, the developing unit should not be vibrated. The reason is that the vibration will loosen the solidified material, which greatly affects the evaluation result.

In order to evaluate the degree of solidification of the developer stored at high temperature and high humidity in this way, the seal attached to the developing unit separating the developer hopper and the developing unit stirring unit is pulled out, and the developer is dropped to the stirring unit. . If it is not solidified, the developer falls smoothly and moves to the agitation unit, but if the solidification is severe, the developer does not fall and there is no transition to the agitation unit. After initial setting of the machine in this state, A4 halftone solid images were output and ranked according to the image state as follows.
◎: Initial agent can be set and good halftone image ○: Initial agent can be set, but streaks can be confirmed slightly □: Initial agent can be set, but streaks can be clearly confirmed △: Less developer fall Levels that cannot be set and cannot be used practically ×: Levels where the developer does not drop and cannot be initialized and cannot be used practically ◎, ○, and □ are acceptable, and Δ and × are unacceptable.

[Color stain resistance evaluation method]
A developer is set in the developing unit of a commercially available digital full-color printer (Ricoh Co., Ltd., imgio MP C5000) modified machine, and the developing unit alone is stirred for 1 hour. The developer thus obtained is developed and fixed, and the L * 1, a * 1, and b * 1 values of the CIE color system at the location where the image density is 1.5 are obtained. In addition, the measurement of the L * 1, a * 1, and b * 1 values of the CIE color system was performed by X-Rite 938, which is a spectral densitometer manufactured by X-Rite. On the other hand, in order to obtain an image free from color stains, an image formed with toner alone (including fixing) without being brought into contact with the carrier is prepared, and the CIE table of the portion where the image density is 1.5 as described above. The L * 0, a * 0, and b * 0 values of the color system are obtained. The color difference ΔE between the two images thus obtained is obtained by the following formula, ΔE ≦ 0.5 is ◎, 0.5 <ΔE ≦ 1.25 is ○, 1.25 <ΔE ≦ 2.00 is Δ, ΔE> 2. 0.0 was marked as x, ◎, ○, and Δ were accepted, and x was rejected.

  From the evaluation results shown in Table 1, the developers according to Examples 1 to 14 according to the present invention showed initial carrier adhesion and carrier adhesion over time in the solid image portion of the developer and solidification resistance compared to Comparative Examples 1 to 5. It is clear that the color stain resistance is improved.

  When the electrophotographic carrier of the present invention is used as a developer in combination with a toner, the initial carrier adhesion and the carrier adhesion over time do not occur in the solid image portion of the developer, the solidification resistance is good, and the color stain resistance Therefore, it can be suitably used as an electrophotographic carrier used for forming an electrostatic latent image into a toner image.

1 Core Material 2 Coating Layer 3 High Frequency Transmitter 4 Coil

JP 2006-154453 A Japanese Examined Patent Publication No. 02-051177 JP 09-304959 A JP 09-329910 A JP 2001-312093 A JP 2007-102159 A JP 2008-70837 A JP 2007-286078 A

Claims (4)

An electrophotographic carrier manufacturing method comprising at least a core material and a coating layer formed on the surface of the core material, the step of coating the core material with a coating material, and the baking step of heat-treating the coated material The firing step is a step of heating and heating the coating material by high-frequency induction heating of the core material with a high-frequency induction heating device, and the power E of the high-frequency induction heating device per unit mass of the carrier Is 0.01-2.5 [kWh / kg], The manufacturing method of the carrier for electrophotography characterized by the above-mentioned.
However, the electric power E is a value calculated by the following formula (1).
E = W / M [kWh / kg] (1)
W: Power per hour [kW]
M: Mass of carrier processed per hour [kg / h]   The method for producing an electrophotographic carrier according to claim 1, wherein an output frequency of the high-frequency induction heating device is 10 to 500 kHz.   3. The method for producing an electrophotographic carrier according to claim 1, wherein an output voltage of the high-frequency induction heating device is 200 to 1500 V. 4.   The method for producing an electrophotographic carrier according to any one of claims 1 to 3, wherein a holding time of the baking temperature by the high-frequency induction heating device is 0 to 60 minutes.