JP2009015084A - Magnetic material-containing resin carrier, two-component developer, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier which reliably prevents carrier deposition on a photoreceptor by increasing the contact area of carriers and the contact area of the carrier and a developing roller, and which can form a high-quality image free of image deficits, and a two-component developer. <P>SOLUTION: The columnar carrier is obtained by crushing a filiform product obtained by a spinning method by which a melt-kneaded product containing a resin and a magnetic material is extruded in filaments and cooled. Since the carrier has a larger contact area of carrier particles and a larger contact area of the carrier and a developing roller as compared with a spherical carrier, the adherence of carriers to each other and the adherence of the carrier to the developing roller can be increased, accordingly the carrier reliably prevents carrier deposition on a photoreceptor and can form a high-quality image free of image deficits. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic substance-containing resin carrier, a two-component developer, a developing device, and an image forming apparatus.

  Toner that visualizes a latent image is used in various image forming processes, and as an example, it is known to be used in an electrophotographic image forming process.

  An image forming apparatus that forms an image using an electrophotographic system includes a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The charging unit charges the surface of the photoreceptor. The exposure unit irradiates the charged photosensitive member surface with signal light to form an electrostatic latent image corresponding to the image information. The developing means supplies toner in the developer to the electrostatic latent image formed on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image formed on the surface of the photoreceptor to a recording medium. The fixing unit fixes the transferred toner image on the recording medium. The cleaning unit cleans the surface of the photoconductor after the toner image is transferred. In such an image forming apparatus, an electrostatic latent image is developed using a one-component developer containing toner or a two-component developer containing toner and a carrier as a developer to form an image. The toner used here is resin particles granulated by dispersing a colorant, a wax as a release agent, etc. in a binder resin as a matrix.

  The carrier contained in the two-component developer has a function of stirring, transporting, and charging the toner. The toner has a function of developing an electrostatic latent image formed on the surface of the photoreceptor. Thus, since the functions of the carrier and the toner are separated in the two-component developer, the toner potential can be easily set as compared with the one-component developer, and the high-speed compatibility and stability are excellent. In the development using a two-component developer, a developer layer called a magnetic brush is formed on the surface of a developing roller containing a magnet, and a carrier and toner are mixed and frictionally charged to each other, and the toner is applied to a photoreceptor. It is mainly performed by a magnetic brush method for electrostatic attachment.

  The carrier comprises a resin-impregnated carrier comprising a carrier core material that is magnetic particles and a coating material that covers the carrier core material, and a magnetic powder-dispersed carrier comprising magnetic particles dispersed in a binder resin. It is divided roughly into.

  Resin-impregnated carriers use materials with high specific gravity and high density, such as iron powder and ferrite, as the carrier core material. Therefore, it is necessary to increase the stirring force to frictionally charge the carrier and toner, resulting in mechanical wear. Is big. Further, when the stirring force is increased, the amount of heat generated by the friction between the carriers, the friction between the toners, and the friction between the toner and the carrier increases, and the low melting point component such as wax contained in the toner may melt. When the low-melting-point component contained in the toner is melted, the melted component adheres to the carrier surface and the carrier spent. Further, when the stirring force is increased, the carrier and the toner are pulverized and the developer is deteriorated.

  On the other hand, the magnetic powder-dispersed carrier has a smaller specific gravity and density than the resin-impregnated carrier, so that the stirring force for frictionally charging the carrier and the toner can be reduced, and the spent of the carrier and the deterioration of the developer are reduced. Can be prevented. Further, the magnetization can be made smaller than that of the resin-impregnated carrier by changing the amount of the magnetic powder dispersed in the binder resin. As a result, a flexible magnetic brush can be formed as compared with the resin-impregnated carrier, and the toner can be stably adhered to the surface of the photoreceptor, so that a higher definition and higher resolution image can be obtained. Can do.

  As such a magnetic powder-dispersed carrier, one having a spherical shape is common. However, if the shape of the carrier is spherical, the contact area between the carriers and the contact area between the carrier and the developing roller when forming the magnetic brush are small, and the adhesion between the carriers and the adhesion between the carrier and the developing roller are low. Get smaller. As a result, carrier adhesion occurs in which the carrier to be carried on the developing roller moves to the photosensitive member, and problems such as image loss occur in the portion where the carrier is adhered.

In view of such a problem, a deformed carrier for the purpose of preventing carrier adhesion to the photoreceptor has been proposed (see, for example, Patent Document 1). The carrier disclosed in Patent Document 1 is a magnetic substance-containing resin carrier configured by further covering a carrier core containing a binder resin and a magnetic substance with a resin. The carrier disclosed in Patent Document 1 has a true specific gravity of 2.5 to 4.0 g / cm ³ , a volume average particle size of 15 μm or more and less than 25 μm, and under a magnetic field of 10,000 / 4π (kA / m). The magnetization intensity is 40 to 80 Am ² / kg, the average circularity C is 0.850 to 0.950, and 0 ≦ (C−C30) ≦ 0. The abundance of carriers having a recess in the projected shape that satisfies the relationship of 200 and is magnified 1000 times with a scanning electron microscope is 20.0% by number or less.

  According to such a deformed carrier, the contact area between the carriers at the time of forming the magnetic brush and the contact area between the carrier and the developing roller can be increased as compared with the spherical carrier, the adhesion between the carriers, and Since the adhesion force between the carrier and the developing roller can be increased, it is possible to reduce the possibility of carrier adhesion. However, although it is possible to reduce the possibility of carrier adhesion compared to spherical carriers, problems with carrier adhesion also occur with such irregularly shaped carriers, which reliably prevent carrier adhesion to the photoreceptor. Therefore, it is difficult to form a high-quality image without image defects.

JP 2005-352473 A

  The object of the present invention is to reliably prevent carrier adhesion to the photoreceptor by increasing the contact area between carriers and the contact area between the carrier and the developing roller, and form a high-quality image free from image defects. A carrier, a two-component developer, a developing device, and an image forming apparatus are provided.

  The present invention is a magnetic substance-containing resin carrier comprising a resin and a magnetic substance and having a cylindrical shape.

The present invention is characterized by being produced by a spinning method.
In the present invention, the spinning method is
A melt-kneading step of melt-kneading the resin and the magnetic material;
An extrusion cooling step in which the melt-kneaded product obtained in the melt-kneading step is extruded into a filament and cooled;
And a pulverizing step of pulverizing the thread-like solidified material obtained in the extrusion cooling step to obtain a cylindrical magnetic substance-containing resin carrier.

In addition, the present invention is characterized in that the true specific gravity is 2.5 g / cm ³ or more and 4.0 g / cm ³ or less.

Further, the present invention is characterized in that the surface is coated with a coating agent.
Further, the invention is characterized in that the coating agent contains a silicone resin or a fluororesin.

The aspect ratio of the present invention is 1.2 or more and 2.0 or less.
The present invention also provides a two-component developer comprising the magnetic material-containing resin carrier of the present invention and a toner containing at least a binder resin and a colorant.

According to the present invention, the toner has a cylindrical shape.
The present invention is also characterized in that the toner has an aspect ratio of 1.0 or more and 3.0 or less.

  According to another aspect of the present invention, there is provided a developing device which performs development using the above two-component developer.

  According to another aspect of the present invention, there is provided an image forming apparatus that forms an image using the developing device.

  According to the present invention, the magnetic substance-containing resin carrier (hereinafter sometimes simply referred to as “carrier”) includes a resin and a magnetic substance, and has a cylindrical shape. A carrier having a cylindrical shape has a larger contact area between carriers and a contact area between the carrier and the developing roller than a carrier having a spherical shape. For example, in the case of a carrier having a spherical shape, the contact between carriers and the contact between the carrier and the developing roller are close to point contact, whereas in the case of a carrier having a cylindrical shape, the contact between carriers and the carrier and development. The contact with the roller can be a state close to line contact or a state close to surface contact. As a result, the adhesion force between the carriers and the adhesion force between the carrier and the developing roller are increased, and the carrier adhesion to the carrier and the photosensitive member can be surely prevented, and a high-quality image free from image defects can be formed.

  According to the invention, the magnetic substance-containing resin carrier is produced by a spinning method. When a magnetic material-containing resin carrier is produced by a spinning method, a carrier having a uniform size can be produced at least in the radial direction of a circle on the bottom surface of the cylinder, and the properties of each carrier, in particular, charging properties, charging performance to toner, etc. Thus, it is possible to obtain a carrier having a small variation and excellent stability.

  According to the invention, the spinning method includes a melt-kneading step, an extrusion cooling step, and a pulverizing step. In the melt-kneading step, the resin and the magnetic material are melt-kneaded to uniformly disperse the magnetic material in the resin. In the extrusion cooling step, a melt-kneaded product in which the magnetic material is uniformly dispersed in the resin is extruded into a thread shape and cooled to obtain a thread-like solidified product. In the pulverization step, the filamentous solidified material is pulverized to obtain a cylindrical carrier.

  By melt-kneading the resin and the magnetic material in the melt-kneading step, a magnetic material-containing resin carrier in which the magnetic material is uniformly dispersed in the resin is obtained. The magnetic substance-containing resin carrier has a smaller specific gravity and density than, for example, a resin-impregnated carrier, so that the stirring force for frictionally charging the carrier and the toner can be reduced, and the spent of the carrier and deterioration of the developer are prevented Is done. Further, the magnetization can be adjusted by changing the amount of the magnetic material dispersed in the resin. As a result, the hardness of the magnetic brush can be controlled and the adhesion of the toner to the surface of the photoreceptor can be improved, so that a higher definition and higher resolution image can be obtained.

  Further, the melt-kneaded product is extruded into a thread shape in an extrusion cooling step, and a solidified product is obtained by cooling, and a cylindrical carrier can be produced by pulverizing this in the pulverization step. It can be manufactured by a simple method.

According to the invention, the true specific gravity of the carrier is 2.5 g / cm ³ or more and 4.0 g / cm ³ or less. The carrier having such a suitable true specific gravity can reduce the stirring force for triboelectrically charging the carrier and the toner, and can prevent the spent of the carrier and the deterioration of the developer.

  Further, according to the present invention, since the surface of the carrier is coated with the coating agent, for example, deterioration of the carrier with time due to stirring can be suppressed, and a carrier having excellent temporal stability can be obtained.

  According to the invention, the coating agent contains a silicone resin or a fluororesin. Silicone resin and fluororesin have releasability with respect to the toner and are excellent in adhesion to the core particles of the carrier containing the resin and the magnetic material. Thus, it is possible to prevent the carrier spent where the carrier is contaminated with the toner. Further, the charge imparting performance to the toner can be stabilized even after long-term use.

  According to the invention, the carrier aspect ratio is 1.2 or more and 2.0 or less. Since the carrier whose aspect ratio is in such a suitable range has a larger surface area than the spherical carrier having the same volume, a predetermined amount of charge can be imparted to the toner with a small amount of developer. Further, since the carrier is not easily cracked by stirring or the like, the durability is excellent.

  According to the invention, since the two-component developer contains the magnetic substance-containing resin carrier having the above-described effect and a toner, it is possible to form a high-quality image having excellent temporal stability and no image defect.

  Further, according to the present invention, since the toner has a cylindrical shape, the contact area between the carrier and the toner can be increased as compared with the case where, for example, a spherical toner is used. The toner can be charged to a predetermined potential in a shorter time.

  According to the invention, the toner aspect ratio is 1.0 or more and 3.0 or less. A toner having an aspect ratio in such a suitable range has a larger surface area than a spherical toner having the same weight, so that the toner has an excellent charge start-up property and takes a long time for the toner to be charged to a predetermined charge amount. It can be shortened. Further, since the toner is not easily cracked by stirring or the like, the durability is excellent. Also, if the aspect ratio is 3.0 or less, the axial dimension is not too large compared to the radial dimension of the circle on the bottom of the cylinder, so it is equivalent to or higher than the spherical toner. A fine image can be formed.

  Further, according to the present invention, since the development is performed using the above two-component developer, it is possible to form a toner image free from image defects due to carrier adhesion to the photoreceptor.

  Further, according to the present invention, a high-quality image free from image defects can be formed by forming an image using the above developing device.

  The magnetic substance-containing resin carrier of the present invention includes a resin and a magnetic substance, and has a cylindrical shape. A carrier having a cylindrical shape has a larger contact area between carriers and a contact area between the carrier and the developing roller than a carrier having a spherical shape. For example, in the case of a carrier having a spherical shape, the contact between carriers and the contact between the carrier and the developing roller are close to point contact, whereas in the case of a carrier having a cylindrical shape, the contact between carriers and the carrier and development. The contact with the roller can be a state close to line contact or a state close to surface contact. As a result, carrier adhesion to the photoconductor can be reliably prevented, and a high-quality image free from image defects can be formed.

  Such a cylindrical carrier can be manufactured, for example, by a spinning method. A method for producing a cylindrical carrier by the spinning method will be described below.

  FIG. 1 is a process diagram showing a procedure of a carrier manufacturing method according to an embodiment of the present invention. The carrier manufacturing method in the present embodiment includes a melt-kneading process in step s1, an extrusion cooling process in step s2, and a pulverizing process in step s3.

<Melting and kneading process>
In the melt-kneading step of step s1, the resin and the magnetic material are melt-kneaded to uniformly disperse the magnetic material in the resin.

  As the resin contained in the carrier, a known resin can be used, and examples thereof include acrylic resin and polyester. These resins may be used alone or in combination. Further, it may be used by mixing with other resins than the above.

  Examples of the acrylic resin include polyacrylate, polymethyl methacrylate, polyethyl methacrylate, poly-n-butyl methacrylate, polyglycidyl methacrylate, polyfluorinated acrylate, styrene-acrylic acid copolymer, styrene-methacrylate copolymer, and styrene. -A butyl methacrylate copolymer, a styrene-ethyl acrylate copolymer, etc. are mentioned.

  Examples of polyesters include polycondensates of alcohol monomers and / or acid monomers. As the alcohol monomer, those commonly used in the synthesis of polyesters can be used. For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neo Diols such as pentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, etc. Bisphenol A alkylene oxide adducts and other dihydric alcohols. As the acid monomer, those commonly used in the synthesis of polyester can be used. For example, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, Carboxylic acids such as adipic acid, sebacic acid, azelaic acid and malonic acid, alkenyl succinic acids such as n-dodecenyl succinic acid and n-dodecyl succinic acid, alkyl succinic acids, anhydrides of these acids, alkyl esters, other divalents These carboxylic acids are mentioned.

  Examples of the magnetic material include powders such as magnetite and ferrite. As a ferrite, a well-known thing can be used, for example, the ferrite powder containing manganese, zinc, copper, etc. can be used.

  As a magnetic body, the smaller the number average particle diameter of the primary particles, the better, and it is preferably 2.0 μm or less. Further, it is more preferably 0.5 μm or more and 2.0 μm or less. When the number average particle diameter of the primary particles of the magnetic material exceeds 2.0 μm, the carrier is easily cracked with the interface between the magnetic material and the resin as a fracture surface, and the durability of the carrier may be reduced. If the number average particle size of the primary particles of the magnetic material is less than 0.5 μm, the magnetic material may aggregate and the dispersion uniformity in the resin may be reduced. The smaller the particle size distribution width of the primary particles of the magnetic material, the better.

In the melt-kneading step, such a resin and a magnetic material are melt-kneaded to produce a melt-kneaded product. The magnetic material is preferably used at a rate such that the true specific gravity of the carrier is 2.5 g / cm ³ or more and 4.0 g / cm ³ or less, depending on the specific gravity of the resin and the specific gravity of the magnetic material. If the true specific gravity of the carrier is less than 2.5 g / cm ³ , the specific gravity of the carrier becomes too small, and there is a possibility of carrier adhesion in which the carrier moves onto the photoreceptor. Further, the charge imparting performance to the toner may be reduced, and the image density may be reduced. If the true specific gravity of the carrier exceeds 4.0 g / cm ³ , the specific gravity and density of the carrier become too large, and it is necessary to increase the stirring force in the developing container, and the carrier and toner deteriorate due to the increase in stirring force. For example, there is a possibility that carrier spent may be generated in which toner fine particles adhere to the carrier and contaminate the carrier. Moreover, the ratio of the magnetic body in a carrier becomes high, and the dispersibility of the magnetic body with respect to resin falls.

  The content of the magnetic material is preferably 20% by weight to 60% by weight and more preferably 30% by weight to 50% by weight with respect to the total amount of the carrier. By using the magnetic material in such a ratio, the true specific gravity of the carrier can be kept within the preferable range.

  In the melt-kneading step, it is preferable to dry-mix the carrier raw material containing the resin and the magnetic material with a mixer and then melt-knead with the kneader. Known mixers can be used, such as Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), etc. Henschel type mixing apparatus, ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), and the like.

  The carrier raw material mixed by the mixer is melt-kneaded by the kneader. A well-known thing can be used also as a kneading machine, for example, common kneading machines, such as a twin-screw extruder, a 3 roll, a laboratory blast mill, can be used. More specifically, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), etc. Extruder, Needex (trade name, manufactured by Mitsui Mining Co., Ltd.) and other open roll type kneaders. Among these, an open roll type kneader is preferable.

  In the melt-kneading step, the carrier raw material is melt-kneaded by heating to a temperature above the softening point of the resin contained in the carrier raw material and below the thermal decomposition temperature. This softens the resin and disperses the magnetic material in the resin. The specific heating temperature at the time of melt kneading is, for example, about 80 ° C. to 200 ° C., preferably about 100 ° C. to 150 ° C. When the carrier raw material is sufficiently melt-kneaded and the magnetic material can be uniformly dispersed in the resin, the process proceeds to the extrusion cooling step of step s2.

<Extrusion cooling process>
In the extrusion cooling step of step s2, the melt-kneaded product obtained in the melt-kneading step is extruded into a yarn shape and cooled. In the extrusion cooling step, for example, a spinning device 1 shown in FIG. 2 is used.

  FIG. 2 is a system diagram schematically showing the configuration of the spinning device 1 used in the extrusion cooling step. FIG. 3 is an enlarged cross-sectional perspective view of the spinning nozzle 5 provided in the spinning device 1 shown in FIG. FIG. 3 is a cross-sectional view perpendicular to the direction in which the kneaded product discharge dies 5b provided in the spinning nozzle 5 are arranged. The spinning device 1 generally includes a kneaded product feeding unit 2, a miniaturizing unit 3, and a cooling unit 4.

The kneaded product feeding unit 2 includes a gear pump 6 and a flow path 7. The gear pump 6 is provided between the discharge side of the kneader 8 used in the melt-kneading step and the flow path 7. The gear pump 6 adjusts the pressure and the amount of extrusion so that the molten kneaded material does not stay and drift, and supplies the molten kneaded material discharged from the kneader 8 to the flow path 7. The gear pump 6 controls the pressure and the amount of extrusion so that the diameter of the melt-kneaded material that is extruded from the spinning nozzle 5 and formed into a yarn shape is constant. In the present embodiment, the pressure applied to the melt-kneaded material in the spinning nozzle 5 is set to 70 kg / cm ² or more in order to set the diameter of the melt-kneaded material formed in the form of yarn to 20 to 30 μm. This pressure is preferably 90 kg / cm ² or more. Although not shown, the flow path 7 is provided so that the outlet thereof is connected to the inlet of the melt-kneaded material (not shown) formed on the upper surface of the spinning nozzle 5. Thereby, the internal space (not shown) of the flow path 7 and the internal flow path (not shown) of the spinning nozzle 5 communicate with each other. The gear pump 6 and the flow path 7 are provided with a heater (not shown) for keeping the melt-kneaded product in a softened state.

  The micronizing unit 3 includes a spinning nozzle 5 for extrusion and a hot air blowing unit 9. The spinning nozzle 5 is a nozzle that discharges the melt-kneaded material supplied from the direction of the arrow 17 by the gear pump 6 through the flow path 7 downward, and extrudes the melt-kneaded material into a thread shape. The nozzle body 5a and the nozzle cover 12 and so on. On the upper surface of the nozzle body 5a, an inlet for a melt-kneaded material (not shown) is formed. This receiving port is connected to the flow path 7 as described above. The nozzle body 5a is provided such that the distance between the side walls in the short direction gradually decreases as it goes downward. A plurality of kneaded material discharge dies 5b penetrating the bottom surface in the thickness direction are arranged in a line in the longitudinal direction of the nozzle body 5a on the bottom surface of the nozzle body 5a. The melt-kneaded material in a pressurized state supplied from the flow path 7 through the inlet of the nozzle body 5a is extruded from the kneaded material discharge die 5b, thereby forming the melt-kneaded material into a thread shape. In the present embodiment, the nozzle body 5a has a kneaded material discharge die 5b having a hole diameter of 200 μm, and the melt-kneaded material is extruded from the kneaded material discharge die 5b to form a thread-like material having a diameter of 20 to 30 μm. The diameter of the melt-kneaded product extruded into a thread shape can be confirmed, for example, by observing a cylindrical carrier obtained by solidifying and pulverizing the thread-shaped melt-kneaded material with an electron microscope at a magnification of 1,000 times. Can do. The nozzle cover 12 is provided at a lower portion of the nozzle body 5a so as to be separated from both side walls in the short direction of the nozzle body 5a, and forms a hot air flow passage 12a together with the both side walls. Hot air is supplied from the hot air blowing section 9 to the hot air flow passage 12a.

  The hot air blowing unit 9 includes a blower 10 that blows hot air and a heater 11 that controls the temperature of the hot air blown from the blower 10. The hot air blowing section supplies the hot air blown from the blower 10 and controlled at a predetermined temperature by the heater 11 to the hot air flow passage 12a from the direction of the arrow 13, thereby causing the temperature of the nozzle main body 5a, and thus the kneaded material discharge die. The viscosity of the melt-kneaded material discharged from 5b is suitably maintained. Thereby, the diameter of the filamentous melt-kneaded material is kept constant.

  In the present embodiment, the hot air blowing section 9 is controlled in the supply amount and temperature of the hot air so that the temperature of the nozzle body 5a is 100 ° C. or higher and 160 ° C. or lower. When the temperature of the nozzle body 5a is less than 100 ° C., the viscosity of the melt-kneaded product is high, and it becomes difficult to discharge the melt-kneaded product from the kneaded product discharge die 5b. Further, even if the melt-kneaded material can be discharged from the kneaded material discharge die 5b, the discharged melt-kneaded material is easily cut, and a filamentous material having a uniform diameter cannot be formed. When the temperature of the nozzle body 5a exceeds 160 ° C., the viscosity of the melt-kneaded product becomes low and the melt-kneaded product becomes easy to stretch, so that the diameter of the melt-kneaded product formed in a thread shape becomes too thin. When forming a 20 to 30 μm-diameter melt-kneaded product as in the present embodiment, the amount of hot air supplied and the temperature are controlled so that the temperature of the nozzle body 5a is 120 ° C. or higher and 130 ° C. or lower. It is preferable.

Although the amount of hot air supplied from the hot air blowing section 9 depends on the temperature of the hot air controlled by the heater 11, for example, when the temperature of the hot air is 160 ° C., 1.5 m ³ / min to 3.0 m ³ / min The following is preferable. If the supply amount of hot air is less than 1.5 m ³ / min, the temperature of the nozzle body 5a cannot be raised to a suitable temperature, and it becomes difficult to discharge the melt-kneaded material from the kneaded material discharge die 5b. Further, the discharged melt-kneaded material is easily cut, and a filamentous material having a uniform diameter cannot be formed. When the supply amount of hot air exceeds 3.0 m ³ / min, the temperature of the nozzle body 5a becomes too high, and the diameter of the melt-kneaded material formed in a thread shape becomes thin.

  The cooling unit 4 cools the melt-kneaded material extruded from the spinning nozzle 5 into a yarn shape. The cooling unit 4 includes a cold air blower 14 and solidifies the melt-kneaded material by blowing cold air onto the melt-kneaded material extruded into a thread shape. The supply amount and temperature of the cold air from the cold air blower 14 are not particularly limited. The spinning device 1 includes a conveying unit 16 that conveys the solidified product of the melt-kneaded product cooled by the cooling unit 4 to the pulverizer 15.

  The extrusion cooling process by the spinning device 1 is performed as follows. The melt-kneaded product obtained in the melt-kneading process is supplied from the gear pump 6 to the spinning nozzle 5 through the flow path 7 with a predetermined extrusion amount and pressure. At this time, the spinning nozzle 5 is heated to a suitable temperature by the hot air blowing section 9. The melt-kneaded material supplied to the spinning nozzle 5 in the direction indicated by the arrow 17 maintains a preferable viscosity when the nozzle body 5a is heated to a suitable temperature and is extruded downward from the kneaded material discharge die 5b into a thread shape. Is done. The melt-kneaded product extruded into a thread shape is cooled and solidified by the cooling unit 4. The solidified product that has been cooled and solidified is conveyed by the conveying means 16 while maintaining its shape in the form of a thread. When the thread-like solidified material is conveyed to the pulverizer 15 by the conveying means 16, the process proceeds to the pulverization step of step s3.

<Crushing process>
In the pulverization step of step s3, the thread-like solidified material obtained in the extrusion cooling step is pulverized to obtain a columnar magnetic substance-containing resin carrier. As a pulverizer used for pulverization, a known pulverizer can be used. For example, a jet-type pulverizer that pulverizes using a supersonic jet stream, a rotor (rotor) that rotates at high speed, and a stator (liner). An impact pulverizer that introduces and pulverizes a coarsely pulverized product into the space formed between the two can be used.

  In the pulverization step, the solidified product formed in a thread shape is pulverized until the dimension in the extending direction of the solidified product is, for example, 20 μm or more and 150 μm or less, preferably 20 μm or more and 60 μm or less. obtain. As a result, a cylindrical carrier having a radial dimension of a circle on the bottom surface of the cylinder of 20 μm or more and 30 μm or less and an axial dimension of 20 μm or more and 150 μm or less, preferably 20 μm or more and 60 μm or less can be obtained.

  After pulverization, classification is preferably performed as necessary. As a result, the particle size distribution width of the carrier can be narrowed, and the charge imparting performance to the toner can be further stabilized. For classification, a known classifier that removes fine powders by classification by centrifugal force or classification by wind force can be used.

  The cylindrical carrier preferably has an aspect ratio of 1.2 or more and 2.0 or less. The aspect ratio is a dimension in the axial direction (a dimension in the axial direction / a dimension in the radial direction) with respect to the dimension in the radial direction of the circle on the bottom surface of the cylinder. When the aspect ratio is less than 1.2, the surface area of the cylindrical carrier cannot be made sufficiently larger than the surface area of the spherical carrier having the same volume, and the effect of using the cylindrical carrier For example, there is a possibility that effects such as a reduction in the developer amount cannot be exhibited. When the aspect ratio exceeds 2.0, the carrier is likely to be cracked by stirring or the like, and the durability may be deteriorated.

  The cylindrical carrier manufactured by the spinning method including the melt-kneading step, the extrusion cooling step, and the pulverizing step as described above has at least a uniform radial dimension and a uniform shape. Can be charged. A carrier having a cylindrical shape has a larger contact area between carriers and a contact area between the carrier and the developing roller than a carrier having a spherical shape. For example, in the case of a carrier having a spherical shape, the contact between carriers and the contact between the carrier and the developing roller are close to point contact, whereas in the case of a carrier having a cylindrical shape, the contact between carriers and the carrier and development. The contact with the roller can be a state close to line contact or a state close to surface contact. As a result, carrier adhesion to the photoconductor can be reliably prevented, and a high-quality image free from image defects can be formed.

  The spinning method including the melt-kneading step, the extrusion cooling step, and the pulverizing step for producing the carrier as described above is particularly preferably used when a thermoplastic resin is mainly used as the resin.

  As the resin used for the carrier, in addition to the resin exemplified above, for example, a thermosetting resin such as a silicone resin, a fluororesin, and an epoxy resin may be used. These resins may be used alone or in combination. Further, it may be used by mixing with other resins than the above.

  Examples of the silicone resin include methyl silicone resin, epoxy-modified silicone resin, acrylic-modified silicone resin, phenol-modified silicone resin, urethane-modified silicone resin, and polyester-modified silicone resin.

  Examples of the fluororesin include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, etc. Is mentioned.

  As an epoxy resin, an acidic group or a basic group containing epoxy resin is mentioned, for example. An acidic group or basic group-containing epoxy resin is produced, for example, by adding or addition polymerizing a base epoxy resin with a polycarboxylic acid such as adipic acid or trimellitic anhydride or an amine such as dibutylamine or ethylenediamine. be able to.

  Even when a thermosetting resin is mainly used as the carrier resin, the above method can be used by carrying out the melt-kneading step and the extrusion cooling step within a range in which the resin maintains a softened state. When a thermosetting resin is mainly used as the resin, the following method can be preferably used instead of the melt-kneading step and the extrusion cooling step.

  When a thermosetting resin is used as the resin, a mixture of a water-soluble polymer compound having fiber formability and a thermosetting resin is spun in a bath having a solidifying ability for the water-soluble polymer compound. The curing process is performed.

  Examples of the water-soluble polymer compound having fiber-forming properties include polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, alginic acid, sodium alginate, and casein acid. These may be used alone or in combination of two or more. For example, when polyvinyl alcohol is used, it can be dissolved in water or a mixture of water and alcohol. Examples of the bath having a solidifying ability with respect to these water-soluble polymer compounds include aqueous solutions of inorganic salts such as ammonium sulfate and sodium sulfate.

  Among the thermosetting resins, liquid ones are left as they are, and solid ones are mixed with a water-soluble polymer in a state of being dissolved in a solvent such as water or alcohol, or a mixed solvent thereof. Mixing of the water-soluble polymer compound having fiber formability and the thermosetting resin is performed by a known mixer as described above. The solid content in the mixed solution used for spinning is 2 to 50% by weight, preferably 5 to 40% by weight, and more preferably 10 to 20% by weight. Furthermore, it is preferable to adjust the solid content concentration so that the viscosity is 5 to 10 Pa · s at the solidification bath temperature at the time of spinning.

  As the spinning device, the same spinning device as that shown in FIG. 2 can be used. However, the spinning nozzle 5 discharges a mixture of the water-soluble polymer compound and the thermosetting resin into a bath having a solidifying ability with respect to the water-soluble polymer compound. The spinning device discharges a mixture of a water-soluble polymer compound and a thermosetting resin into a bath having a solidifying ability with respect to the water-soluble polymer compound, thereby Is extruded into a thread. Next, the filamentous material is heat-treated at a temperature corresponding to the curing temperature of the resin to cure the thermosetting resin. The water-soluble polymer compound contained in the filament obtained by the spinning method is removed as necessary. Removal of the water-soluble compound is performed by dissolving in warm water, warm water adjusted to dilute alkalinity, or warm water adjusted to dilute acid depending on the type of the water-soluble polymer.

  According to the method as described above, even if a thermosetting resin is used, a filamentous material can be formed by a spinning method. The obtained filamentous material is pulverized by the same pulverization process as described above to obtain a magnetic substance-containing resin carrier having a cylindrical shape.

  The surface of the magnetic substance-containing resin carrier having a cylindrical shape of the present invention is preferably coated with a coating agent. When the surface of the carrier is coated with a coating agent, for example, deterioration of the carrier with time due to stirring can be suppressed, and a carrier having excellent stability over time can be obtained.

  The coating agent preferably contains a silicone resin or a fluororesin. Silicone resin and fluororesin have releasability with respect to the toner and are excellent in adhesion to the core particles of the carrier containing the resin and the magnetic material. As a result, the carrier spent where the carrier is contaminated by the toner can be prevented, and the charge imparting performance to the toner can be stabilized even after long-term use.

  For example, when the resin contained in the magnetic substance-containing resin carrier is a silicone resin or a fluororesin, the same material as the resin contained in the carrier is used as a coating agent to prevent the carrier properties from changing even after long-term use. Therefore, it is possible to obtain a carrier having excellent temporal stability. When the resin contained in the magnetic substance-containing resin carrier does not contain a silicone resin and a fluororesin, the surface energy of the carrier can be reduced by using a silicone resin or a fluororesin as a coating agent, and the charge amount of the toner can be reduced. It is possible to improve the performance of the carrier, for example, by preventing the toner from becoming too high and appropriately setting the amount of toner attached to the carrier.

  The amount of the coating agent used is preferably from 0.5 to 10 parts by weight, more preferably from 1 to 3 parts by weight, based on 100 parts by weight of the carrier. Examples of the coating of the coating agent on the carrier include an immersion method and a spray method. In the dipping method, the carrier is dipped in a coating solution in which the coating agent is dispersed in a solvent to coat the coating agent, and the solvent is removed by drying. In the spray method, a coating solution obtained by dispersing a coating agent in a solvent is sprayed on a carrier to coat the coating agent, and dried to remove the solvent.

The coating layer of the magnetic body-containing resin carrier having a cylindrical shape of the present invention may contain conductive particles. As the conductive particles, for example, conductive carbon black, oxides such as conductive titanium oxide and tin oxide are used. Carbon black or the like is suitable for developing the conductivity with a small addition amount, but there is a concern that the color toner may be desorbed from the carrier coating layer. In this case, conductive titanium oxide doped with antimony is used. The conductive particles are preferably contained in a proportion of 30 parts by weight or less with respect to 100 parts by weight of the resin contained in the coating agent. When the conductive particles contained in the carrier coating layer are used in an amount of 30 parts by weight or less with respect to 100 parts by weight of the resin contained in the coating agent, the charge imparting property of the carrier to the toner is further improved. In addition, the mechanical strength of the coating layer, the adhesion to the ferrite particles, and the like are improved. Therefore, it is possible to obtain a carrier capable of charging the toner stably for a long time. The specific resistance of the conductive particles is preferably 10 ¹⁰ Ω · cm or less.

  The carrier of the present invention is used as a two-component developer together with the toner. The toner used with the carrier of the present invention preferably has a cylindrical shape. The cylindrical toner is manufactured by the following melt-kneading process, spinning process, and pulverizing process in the same manner as the cylindrical carrier.

<Melting and kneading process>
In the melt-kneading step, a toner raw material containing a binder resin, a colorant, and a toner additive such as a release agent and a charge control agent is melt-kneaded.

  The binder resin is not particularly limited as long as it is commonly used as a binder resin for toner, and examples thereof include polyester, polyurethane, epoxy resin, acrylic resin, and styrene-acrylic resin. Among these, polyester, acrylic resin, and styrene-acrylic resin are preferable. One of these resins may be used alone, or two or more thereof may be used in combination. Moreover, even if it is the same kind of resin, it is possible to use a plurality of kinds of resins different in any one or more in terms of molecular weight, monomer composition, and the like.

  Polyester is excellent in transparency, and can impart good powder fluidity, low-temperature fixability, secondary color reproducibility, and the like to the aggregated particles, and is therefore suitable as a binder resin for color toners. Known polyesters can be used, and examples thereof include polycondensates of polybasic acids and polyhydric alcohols. As the polybasic acid, those known as polyester monomers can be used, for example, terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid and other aromatic carboxylic acids, maleic anhydride Examples thereof include aliphatic carboxylic acids such as acid, fumaric acid, succinic acid, alkenyl succinic anhydride, and adipic acid, and methyl esterified products of these polybasic acids. A polybasic acid can be used individually by 1 type, or can use 2 or more types together. As the polyhydric alcohol, those known as monomers for polyesters can be used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentylglycol, glycerin, cyclohexanediol, cyclohexanediene, etc. Examples thereof include aromatic diols such as alicyclic polyhydric alcohols such as methanol and hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A. A polyhydric alcohol can be used individually by 1 type, or can use 2 or more types together. The polycondensation reaction between the polybasic acid and the polyhydric alcohol can be carried out according to a conventional method. For example, the polybasic acid and the polyhydric alcohol are contacted in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst. The process is terminated when the acid value, softening point, etc. of the polyester to be produced reach a predetermined value. Thereby, polyester is obtained. When a methyl esterified product of a polybasic acid is used as a part of the polybasic acid, a demethanol polycondensation reaction is performed. In this polycondensation reaction, for example, the carboxyl group content at the end of the polyester can be adjusted by appropriately changing the mixing ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc., and thus the properties of the resulting polyester are modified. it can. When trimellitic anhydride is used as the polybasic acid, a modified polyester can also be obtained by easily introducing a carboxyl group into the main chain of the polyester. A self-dispersible polyester in water in which a hydrophilic group such as a carboxyl group or a sulfonic acid group is bonded to the main chain and / or side chain of the polyester can also be used. Further, polyester and acrylic resin may be grafted.

  Although it does not restrict | limit especially as an acrylic resin, An acidic group containing acrylic resin can be used preferably. The acidic group-containing acrylic resin is, for example, an acrylic resin monomer or an acrylic resin monomer containing an acidic group or a hydrophilic group and / or a vinyl having an acidic group or a hydrophilic group when an acrylic resin monomer or an acrylic resin monomer and a vinyl monomer are polymerized. It can manufacture by using together a system monomer. Known acrylic resin monomers can be used, for example, acrylic acid that may have a substituent, methacrylic acid that may have a substituent, acrylic ester that may have a substituent, and a substituent. Methacrylic acid ester and the like. Specific examples of the acrylic resin monomer include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, acrylic Acrylic acid ester monomers such as 2-ethylhexyl acid, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate Methacrylate monomers such as amyl, methacrylate n-hexyl, methacrylate 2-ethylhexyl, methacrylate n-octyl, decyl methacrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxy methacrylate Propyl and the like hydroxyl group (hydroxyl group) containing (meth) acrylic acid ester monomers such as. Acrylic resin monomers can be used alone or in combination of two or more. As the vinyl monomer, known monomers can be used, and examples thereof include styrene, α-methylstyrene, vinyl bromide, vinyl chloride, vinyl acetate, acrylonitrile and methacrylonitrile. A vinyl monomer can be used individually by 1 type, or can use 2 or more types together. The polymerization is carried out by solution polymerization, suspension polymerization, emulsion polymerization or the like using a general radical initiator.

  Examples of the styrene-acrylic resin include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate. Examples thereof include a copolymer, a styrene-butyl methacrylate copolymer, and a styrene-acrylonitrile copolymer.

  The binder resin preferably has a glass transition point of 30 ° C. or higher and 80 ° C. or lower. If the glass transition point of the binder resin is less than 30 ° C., blocking in which the toner thermally aggregates easily occurs in the image forming apparatus, and storage stability may be lowered. When the glass transition point of the binder resin exceeds 80 ° C., the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs.

  As the colorant, organic dyes, organic pigments, inorganic dyes, inorganic pigments and the like commonly used in the electrophotographic field can be used.

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Examples of yellow colorants include chrome lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, and benzidine. Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment orange 31, C.I. I. And CI Pigment Orange 43.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, and brilliant carmine 6B. Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of purple colorants include manganese purple, fast violet B, and methyl violet lake.

  Examples of blue colorants include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated products, first sky blue, induslen blue BC, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

  Examples of the green colorant include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, C.I. I. And CI Pigment Green 7.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  One colorant can be used alone, or two or more different colorants can be used in combination. Moreover, even if it is the same color, 2 or more types can be used together. The amount of the colorant to be used is not particularly limited, but is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, those commonly used in this field can be used, for example, petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax (polyethylene wax, polypropylene Wax etc.) and derivatives thereof, low molecular weight polypropylin wax and derivatives thereof, hydrocarbon polymer waxes such as polyolefin polymer wax (low molecular weight polyethylene wax etc.) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof , Candelilla wax and its derivatives, plant wax such as wood wax, animal wax such as beeswax and whale wax, fatty acid amide, phenol fatty acid ester, etc. Oil-based synthetic waxes, long-chain carboxylic acids and their derivatives, long-chain alcohols and derivatives thereof, silicone polymers, such as higher fatty acids. Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. The amount of the wax used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, particularly preferably 100 parts by weight of the binder resin. 1.0 to 8.0 parts by weight.

  As the charge control agent, those for positive charge control and negative charge control commonly used in this field can be used. Examples of charge control agents for positive charge control include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, and triphenylmethane. Derivatives, guanidine salts, amidine salts and the like can be mentioned. As charge control agents for controlling negative charges, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and its derivatives, metal complexes and metal salts (metal is Chromium, zinc, zirconium, etc.), fatty acid soaps, long-chain alkyl carboxylates, resin acid soaps, and the like. The charge control agent can be used alone or in combination of two or more as required. The amount of the charge control agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the binder resin.

  In the melt-kneading step, as in the melt-kneading step in the carrier production method, the toner raw material containing at least the binder resin and the colorant is dry-mixed with a mixer and then melt-kneaded with the kneader. As the mixer and kneader used in the melt-kneading step, the same mixers and kneaders used in the melt-kneading step in the carrier production method can be used.

  In the melt-kneading step, the toner raw material is melt-kneaded by heating to a temperature above the softening point of the binder resin contained in the toner raw material and below the thermal decomposition temperature. This softens the resin and disperses the magnetic material in the resin. The specific heating temperature at the time of melt kneading is, for example, about 80 ° C. to 200 ° C., preferably about 100 ° C. to 150 ° C. When the toner raw material is sufficiently melt-kneaded and the components of the toner raw material other than the binder resin such as the colorant can be uniformly dispersed in the binder resin, the process proceeds to the spinning step.

<Spinning process>
In the spinning step, the melt-kneaded product obtained by melt-kneading the toner raw material is extruded into a yarn shape and cooled in the same manner as in the extrusion cooling step in the carrier production method described above. As the spinning device used in the spinning process, the spinning device 1 shown in FIG. 2 can be used. In the spinning step, the melt-kneaded material is extruded from the kneaded material discharge die of the spinning nozzle to form a thread-like material, as in the carrier manufacturing method. At this time, the melt-kneaded product is preferably formed into a filamentous material having a diameter of 3 to 8 μm. If the diameter of the filamentous material is less than 3 μm, the toner is likely to be cracked due to stirring or the like, and toner fine powder is likely to be generated. When the diameter of the filamentous material exceeds 8 μm, a high-definition image may not be formed. The hole diameter of the kneaded product discharge die of the spinning nozzle, the pressure and extrusion amount of the gear pump, the supply amount and temperature of hot air from the hot air blowing section, so that the filamentous material formed from the melt-kneaded product is extruded with the above-mentioned suitable diameter. Adjust as appropriate. In the spinning process, the melt-kneaded product is extruded from a kneaded product discharge die of a spinning nozzle, and is cooled and solidified by a cold air blower. When a solidified product of the filamentous melt-kneaded material containing the toner raw material is obtained, the process proceeds to the pulverization step.

<Crushing process>
In the pulverization step, the thread-like solidified product obtained in the extrusion cooling step is pulverized to obtain a cylindrical toner. As a pulverizer used for pulverization, the same pulverizer as used for the production of a carrier can be used. Further, after pulverization, classification is preferably performed as necessary. In the pulverization step, a cylindrical toner is obtained in which the radial dimension of the circle at the bottom of the cylinder is 3 μm or more and 8 μm or less, and the axial dimension is 3 μm or more and 15 μm or less, preferably 3 μm or more and 10 μm or less.

  The cylindrical toner preferably has an aspect ratio of 1.0 or more and 3.0 or less. The aspect ratio is more preferably 1.2 or more and 2.0 or less. When the aspect ratio is less than 1.0, the surface area of the cylindrical toner cannot be made sufficiently larger than the surface area of the spherical toner having the same volume, and the contact area between the carrier and the toner is sufficient. Therefore, the time required for the toner to be charged to a predetermined charge amount may not be shortened. When the aspect ratio exceeds 3.0, the toner is liable to be cracked by stirring or the like, which may cause problems such as deterioration in durability and carrier spent. Further, since the toner becomes large, there is a possibility that a high-definition image cannot be formed.

  Since the cylindrical toner manufactured as described above has at least a radial dimension uniform and uniform shape, there is little variation in charging performance among individual toner particles, and the charging stability is excellent. Further, the toner having a cylindrical shape has a larger contact area between the toner and the carrier than the toner having a spherical shape. Therefore, the toner can be efficiently frictionally charged, and the time required to rise to a predetermined charge amount can be shortened.

  An external additive may be added to the cylindrical toner. Known external additives can be used, and examples thereof include silica, titanium oxide, and alumina. These are preferably surface-treated with a silicone resin, a silane coupling agent or the like. The amount of the external additive used is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the toner.

  By using the cylindrical carrier of the present invention together with the cylindrical toner, it is possible to form a high-quality image with excellent temporal stability and no image defect, and to charge the toner with a predetermined amount with a small amount of developer. Can be granted. As a result, the time required for charging the toner can be further shortened, and a two-component developer excellent in toner charge rising property can be obtained. The cylindrical carrier of the present invention is particularly preferably used together with the cylindrical toner as described above. However, the present invention is not limited to this, and even when used with an irregularly shaped toner and a spherical toner, The effect can be exhibited sufficiently.

  FIG. 4 is a cross-sectional view schematically showing the configuration of the image forming apparatus 100 according to the embodiment of the present invention. The image forming apparatus is a multifunction machine having both a copying function, a printer function, and a facsimile function, and forms a full-color or monochrome image on a recording medium according to transmitted image information. In other words, the image forming apparatus has three types of printing modes, ie, a copier mode (copying mode), a printer mode, and a facsimile mode. Operation input from an operation unit (not shown), personal computer, portable terminal device, information recording A print mode is selected by a control unit (not shown) in response to reception of a print job from an external device using a storage medium or a memory device. The image forming apparatus includes a toner image forming unit 102, a transfer unit 103, a fixing unit 104, a recording medium supply unit 105, and a discharge unit 106. Each member constituting the toner image forming unit 102 and some members included in the intermediate transfer unit 103 are black (b), cyan (c), magenta (m), and yellow (y) included in the color image information. In order to correspond to the image information of each color, four each are provided. Here, each member provided by four according to each color is distinguished by attaching an alphabet representing each color to the end of the reference symbol, and when referring collectively, only the reference symbol is used.

  The toner image forming unit 102 includes a photosensitive drum 111, a charging unit 112, an exposure unit 113, a developing unit 114, and a cleaning unit 115. The charging unit 112, the developing unit 114, and the cleaning unit 115 are arranged around the photosensitive drum 111 in this order. The charging unit 112 is disposed below the developing unit 114 and the cleaning unit 115 in the vertical direction.

  The photosensitive drum 111 is supported by a driving unit (not shown) so as to be rotatable around an axis, and includes a conductive substrate (not shown) and a photosensitive layer formed on the surface of the conductive substrate. The conductive substrate can take various shapes, and examples thereof include a cylindrical shape, a columnar shape, and a thin film sheet shape. Among these, a cylindrical shape is preferable. The conductive substrate is formed of a conductive material. As the conductive material, those commonly used in this field can be used. For example, metals such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, etc. A conductive layer made of one or more of aluminum, aluminum alloy, tin oxide, gold, indium oxide and the like is formed on a film-like substrate such as two or more alloys, synthetic resin film, metal film, paper, etc. And a resin composition containing a conductive film, conductive particles and / or a conductive polymer. In addition, as a film-form base | substrate used for an electroconductive film, a synthetic resin film is preferable and a polyester film is especially preferable. Moreover, as a formation method of the electroconductive layer in an electroconductive film, vapor deposition, application | coating, etc. are preferable.

  The photosensitive layer is formed, for example, by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. In that case, it is preferable to provide an undercoat layer between the conductive substrate and the charge generation layer or the charge transport layer. By providing an undercoat layer, the scratches and irregularities present on the surface of the conductive substrate are coated to smooth the surface of the photosensitive layer, to prevent deterioration of the chargeability of the photosensitive layer during repeated use. Alternatively, an advantage of improving the charging characteristics of the photosensitive layer in a low humidity environment can be obtained. Further, a laminated photoreceptor having a three-layer structure having a high durability and having a photoreceptor surface protective layer as the uppermost layer may be used.

  The charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and contains a known binder resin, plasticizer, sensitizer and the like as necessary. As the charge generation material, those commonly used in this field can be used. Phthalocyanine pigments such as metal-free phthalocyanine, squalium dye, azulenium dye, thiapyrylium dye, carbazole skeleton, styryl stilbene skeleton, triphenylamine skeleton, dibenzothiophene skeleton, oxadiazole skeleton, fluorenone skeleton, bis stilbene skeleton, distyryl oxa And azo pigments having a diazole skeleton or a distyrylcarbazole skeleton. Among these, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing a fluorene ring and / or a fluorenone ring, bisazo pigments composed of aromatic amines, trisazo pigments, etc. have high charge generation ability and high sensitivity. Suitable for obtaining a photosensitive layer. One type of charge generating material can be used alone, or two or more types can be used in combination. The content of the charge generation material is not particularly limited, but is preferably 5 to 500 parts by weight, more preferably 10 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. As the binder resin for the charge generation layer, those commonly used in this field can be used. For example, melamine resin, epoxy resin, silicone resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, polycarbonate, phenoxy resin , Polyvinyl butyral, polyarylate, polyamide, polyester and the like. Binder resin can be used individually by 1 type, or can use 2 or more types together as needed.

  The charge generation layer generates charge by dissolving or dispersing appropriate amounts of charge generation materials, binder resins and, if necessary, plasticizers and sensitizers in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by preparing a layer coating solution, applying this charge generation layer coating solution to the surface of the conductive substrate and drying. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 2.5 μm.

  The charge transport layer laminated on the charge generation layer has a charge transport material having the ability to accept and transport the charge generated from the charge generation material and a binder resin for the charge transport layer as essential components. Contains known antioxidants, plasticizers, sensitizers, lubricants and the like. As the charge transport material, those commonly used in this field can be used, for example, poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensation product and derivatives thereof, Polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline Derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, 3-methyl-2-benzothiazoline -Donating substances such as azine compounds, fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyano Examples include electron-accepting substances such as ethylene, tetracyanoquinodimethane, promanyl, chloranil, and benzoquinone. The charge transport materials can be used alone or in combination of two or more. The content of the charge transport material is not particularly limited, but is preferably 10 to 300 parts by weight, more preferably 30 to 150 parts by weight with respect to 100 parts by weight of the binder resin in the charge transport material. As the binder resin for the charge transport layer, those commonly used in this field and capable of uniformly dispersing the charge transport material can be used. For example, polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, polyurethane , Polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone resin, and copolymer resins thereof. Among these, in consideration of film formability, wear resistance of the resulting charge transport layer, electrical characteristics, etc., polycarbonate containing bisphenol Z as a monomer component (hereinafter referred to as “bisphenol Z type polycarbonate”), bisphenol Z type polycarbonate And a mixture of polycarbonate with other polycarbonates are preferred. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The charge transport layer preferably contains an antioxidant together with the charge transport material and the binder resin for the charge transport layer. As the antioxidant, those commonly used in this field can be used, and examples thereof include vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. It is done. One antioxidant can be used alone, or two or more antioxidants can be used in combination. The content of the antioxidant is not particularly limited, but is 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total amount of components constituting the charge transport layer. The charge transport layer is dissolved or dispersed in a suitable organic solvent that can dissolve or disperse these components in an appropriate amount such as a charge transport material and a binder resin, and if necessary, an antioxidant, a plasticizer, and a sensitizer. The charge transport layer coating liquid is prepared, and the charge transport layer coating liquid is applied to the surface of the charge generation layer and dried. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 10 to 50 μm, more preferably 15 to 40 μm. Note that a photosensitive layer in which a charge generation material and a charge transport material are present can be formed in one layer. In that case, the type, content, binder resin, and other additives of the charge generation material and the charge transport material may be the same as in the case of separately forming the charge generation layer and the charge transport layer.

  In this embodiment, the photosensitive drum formed by forming the organic photosensitive layer using the charge generation material and the charge transport material as described above is used. Instead, an inorganic photosensitive layer using silicon or the like is formed. Can be used.

  The charging unit 112 faces the photosensitive drum 111 and is disposed so as to be separated from the surface of the photosensitive drum 111 along the longitudinal direction of the photosensitive drum 111 with a gap, and the surface of the photosensitive drum 111 has a predetermined polarity and Charge to potential. As the charging unit 112, a charging brush type charger, a charger type charger, a sawtooth type charger, an ion generator, or the like can be used. In the present embodiment, the charging unit 112 is provided so as to be separated from the surface of the photosensitive drum 111, but is not limited thereto. For example, a charging roller may be used as the charging unit 112, and the charging roller may be disposed so that the charging roller and the photosensitive drum are in pressure contact with each other, or a contact charging type charger such as a charging brush or a magnetic brush may be used. .

  The exposure unit 113 is arranged so that light of each color information emitted from the exposure unit 113 passes between the charging unit 112 and the developing unit 114 and is irradiated on the surface of the photosensitive drum 111. The exposure unit 113 branches the image information into light of each color information of b, c, m, and y in the unit, and the surface of the photosensitive drum 111 charged to a uniform potential by the charging unit 112 is light of each color information. To form an electrostatic latent image on the surface. As the exposure unit 113, for example, a laser scanning unit including a laser irradiation unit and a plurality of reflection mirrors can be used. In addition, a unit in which an LED array, a liquid crystal shutter, and a light source are appropriately combined may be used.

  FIG. 5 is a cross-sectional view schematically showing the configuration of the developing unit 114 according to the embodiment of the present invention. The developing unit 114 includes a developing tank 120 and a toner hopper 121. The developing tank 120 is disposed so as to face the surface of the photosensitive drum 111, and is a container that supplies toner to an electrostatic latent image formed on the surface of the photosensitive drum 111 and develops it to form a visible toner image. It is a shaped member. The developing tank 120 accommodates toner in its internal space and accommodates a roller member such as a developing roller, a supply roller, and a stirring roller, or a screw member, and rotatably supports the developing tank 120. An opening is formed in a side surface of the developing tank 120 facing the photosensitive drum 111, and a developing roller is rotatably provided at a position facing the photosensitive drum 111 through the opening. The developing roller is a roller-like member that supplies toner to the electrostatic latent image on the surface of the photoconductor 111 at the pressure contact portion or the closest portion with the photoconductor drum 111. When supplying the toner, a potential having a polarity opposite to the charging potential of the toner is applied to the surface of the developing roller as a developing bias voltage (hereinafter simply referred to as “developing bias”). As a result, the toner on the surface of the developing roller is smoothly supplied to the electrostatic latent image. Further, by changing the developing bias value, the amount of toner (toner adhesion amount) supplied to the electrostatic latent image can be controlled. The supply roller is a roller-like member provided so as to be able to rotate and face the developing roller, and supplies toner around the developing roller. The agitating roller is a roller-like member that faces the supply roller and can be driven to rotate, and feeds toner newly supplied from the toner hopper 121 into the developing tank 120 around the supply roller. The toner hopper 121 is provided so that a toner replenishing port (not shown) provided at the lower part in the vertical direction communicates with a toner receiving port (not shown) provided at the upper part in the vertical direction of the developing tank 120. The toner is replenished according to the toner consumption status of 120. Further, the toner hopper 121 may not be used, and the toner may be directly supplied from each color toner cartridge.

  By developing using the two-component developer of the present invention, a high-definition and high-resolution high-quality toner image can be formed on the photoreceptor.

  The cleaning unit 115 removes the toner remaining on the surface of the photosensitive drum 111 after the toner image is transferred to the recording medium, and cleans the surface of the photosensitive drum 11. For the cleaning unit 115, for example, a plate-like member such as a cleaning blade is used. In the image forming apparatus of the present invention, an organic photosensitive drum is mainly used as the photosensitive drum 111, and the surface of the organic photosensitive drum is mainly composed of a resin component. Deterioration of the surface is likely to proceed due to the chemical action of ozone generated by. However, the deteriorated surface portion is worn by receiving a rubbing action by the cleaning unit 115 and is gradually but surely removed. Therefore, the problem of surface deterioration due to ozone or the like is practically solved, and the charging potential by the charging operation can be stably maintained over a long period of time. Although the cleaning unit 115 is provided in this embodiment, the present invention is not limited to this, and the cleaning unit 15 may not be provided.

  According to the toner image forming unit 102, the surface of the photosensitive drum 111 that is uniformly charged by the charging unit 112 is irradiated with signal light corresponding to image information from the exposure unit 113 to form an electrostatic latent image. Toner is supplied from the developing unit 114 to form a toner image, and the toner image is transferred to the intermediate transfer belt 125. Then, the toner remaining on the surface of the photosensitive drum 111 is removed by the cleaning unit 115. This series of toner image forming operations is repeatedly executed.

  The transfer unit 103 is disposed above the photosensitive drum 111, and includes an intermediate transfer belt 125, a driving roller 126, a driven roller 127, an intermediate transfer roller 128 (b, c, m, y), and a transfer belt cleaning unit. 129 and the transfer roller 130. The intermediate transfer belt 125 is an endless belt-like member that is stretched by a driving roller 126 and a driven roller 127 to form a loop-shaped movement path, and is driven to rotate in the direction of an arrow B. When the intermediate transfer belt 125 passes through the photosensitive drum 111 while being in contact with the photosensitive drum 111, the intermediate transfer roller 128 disposed on the surface of the photosensitive drum 111 via the intermediate transfer belt 125 faces the photosensitive drum 111. A transfer bias having a polarity opposite to the charging polarity of the toner is applied, and the toner image formed on the surface of the photosensitive drum 111 is transferred onto the intermediate transfer belt 125. In the case of a full-color image, each color toner image formed on each photoconductor drum 111 is sequentially transferred onto the intermediate transfer belt 125 to form a full-color toner image. The driving roller 126 is provided so as to be rotatable around its axis by driving means (not shown), and the intermediate transfer belt 125 is driven to rotate in the direction of arrow B by the rotational driving. The driven roller 127 is provided so as to be able to be driven and rotated by the rotational drive of the driving roller 126, and applies a constant tension to the intermediate transfer belt 125 so that the intermediate transfer belt 1 25 does not loosen. The intermediate transfer roller 128 is provided in pressure contact with the photosensitive drum 111 via the intermediate transfer belt 125, and can be driven to rotate about its axis by a driving unit (not shown). The intermediate transfer roller 128 is connected to a power source (not shown) for applying a transfer bias as described above, and has a function of transferring the toner image on the surface of the photosensitive drum 111 to the intermediate transfer belt 125. The transfer belt cleaning unit 129 is provided so as to face the driven roller 127 through the intermediate transfer belt 125 and to contact the outer peripheral surface of the intermediate transfer belt 125. The toner adhering to the intermediate transfer belt 125 due to contact with the photosensitive drum 111 causes the back surface of the recording medium to be contaminated. Therefore, the transfer belt cleaning unit 129 removes and collects the toner on the surface of the intermediate transfer belt 125. The transfer roller 130 is in pressure contact with the driving roller 1 26 via the intermediate transfer belt 125, and is provided so as to be rotationally driven around an axis line by a driving means (not shown). At the pressure contact portion (transfer nip portion) between the transfer roller 130 and the drive roller 126, the toner image carried and conveyed by the intermediate transfer belt 125 is transferred to the recording medium fed from the recording medium supply means 105 described later. Is done. The recording medium carrying the toner image is fed to the fixing unit 104. According to the transfer unit 103, the toner image transferred from the photosensitive drum 111 to the intermediate transfer belt 125 at the pressure contact portion between the photosensitive drum 111 and the intermediate transfer roller 128 rotates the intermediate transfer belt 125 in the arrow B direction. It is conveyed to a transfer nip portion by driving, and transferred to a recording medium there.

  The fixing unit 104 is provided downstream of the transfer unit 103 in the conveyance direction of the recording medium, and includes a fixing roller 131 and a pressure roller 132. The fixing roller 131 is rotatably provided by a driving unit (not shown), and heats and melts toner constituting an unfixed toner image carried on the recording medium to fix it on the recording medium. A heating unit (not shown) is provided inside the fixing roller 131. The heating unit heats the fixing roller 131 so that the surface of the fixing roller 131 reaches a predetermined temperature (heating temperature). For example, a heater or a halogen lamp can be used as the heating means. The heating means is controlled by fixing condition control means described later. The control of the heating temperature by the fixing condition control means will be described in detail later. A temperature detection sensor is provided near the surface of the fixing roller 131 to detect the surface temperature of the fixing roller 131. The detection result by the temperature detection sensor is written in the storage unit of the control means described later. The pressure roller 132 is provided so as to be in pressure contact with the fixing roller 131, and is supported so as to be driven to rotate by the rotation drive of the pressure roller 132. The pressure roller 132 assists the fixing of the toner image to the recording medium by pressing the toner and the recording medium when the toner is melted and fixed on the recording medium by the fixing roller 131. A pressure contact portion between the fixing roller 131 and the pressure roller 132 is a fixing nip portion. According to the fixing unit 104, the recording medium onto which the toner image is transferred by the transfer unit 103 is sandwiched between the fixing roller 131 and the pressure roller 132, and the toner image is recorded under heating when passing through the fixing nip portion. By being pressed against the medium, the toner image is fixed on the recording medium and an image is formed.

  The recording medium supply unit 105 includes an automatic paper feed tray 135, a pickup roller 136, a transport roller 137, a registration roller 138, and a manual paper feed tray 139. The automatic paper feed tray 135 is a container-like member that is provided in the lower part of the image forming apparatus in the vertical direction and stores a recording medium. Recording media include plain paper, color copy paper, overhead projector sheets, postcards, and the like. The pick-up roller 136 takes out the recording medium stored in the automatic paper feed tray 135 one by one and feeds it to the paper transport path S1. The conveyance rollers 137 are a pair of roller members provided so as to be in pressure contact with each other, and convey the recording medium toward the registration rollers 138. The registration rollers 138 are a pair of roller members provided so as to be in pressure contact with each other, and the recording medium fed from the conveyance roller 137 is used to convey the toner image carried on the intermediate transfer belt 125 to the transfer nip portion. Synchronously, it is fed to the transfer nip. The manual paper feed tray 139 is a device that takes a recording medium into the image forming apparatus by manual operation. The recording medium taken from the manual paper feed tray 139 passes through the paper conveyance path S2 by the conveyance roller 37, and It is fed to the registration roller 138. According to the recording medium supply unit 105, a toner image carried on the intermediate transfer belt 125 is conveyed to the transfer nip portion of the recording medium supplied one by one from the automatic paper feed tray 135 or the manual paper feed tray 139. In synchronism with this, the sheet is fed to the transfer nip portion.

  The discharge unit 106 includes a conveyance roller 137, a discharge roller 140, and a discharge tray 141. The conveyance roller 137 is provided on the downstream side of the fixing nip portion in the sheet conveyance direction, and conveys the recording medium on which the image is fixed by the fixing unit 104 toward the discharge roller 140. The discharge roller 140 discharges the recording medium on which the image is fixed to a discharge tray 141 provided on the upper surface in the vertical direction of the image forming apparatus. The discharge tray 141 stores a recording medium on which an image is fixed.

  The image forming apparatus 100 includes a control unit (not shown). The control unit is provided, for example, in an upper part of the internal space of the image forming apparatus, and includes a storage unit, a calculation unit, and a control unit. In the storage unit of the control means, various setting values via an operation panel (not shown) arranged on the upper surface of the image forming apparatus, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus, Image information and the like are input. In addition, programs for executing various means are written. Examples of the various means include a recording medium determination unit, an adhesion amount control unit, and a fixing condition control unit. As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). As the external device, an electric / electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus can be used. For example, a computer, a digital camera, a television, a video recorder, a DVD recorder, Examples include an HDVD, a Blu-ray disc recorder, a facsimile machine, and a mobile terminal device. The arithmetic unit takes out various data (image formation command, detection result, image information, etc.) written in the storage unit and programs of various means, and performs various determinations. The control unit sends a control signal to the corresponding device according to the determination result of the calculation unit, and performs operation control. The control unit and the calculation unit include a processing circuit realized by a microcomputer, a microprocessor, or the like provided with a central processing unit (CPU). The control means includes a main power supply together with the processing circuit described above, and the power supply supplies power not only to the control means but also to each device in the image forming apparatus.

  By forming an image using an image forming apparatus provided with the developing device of the present invention, it is possible to form a high-quality image with excellent reproducibility of a document image and high definition and high resolution.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified. The true specific gravity of the carrier, the size of the cylindrical carrier, the volume average particle size, and the number average particle size of the primary particles of the magnetic material in the examples and comparative examples were measured as follows.

[True specific gravity of carrier]
It measured using the dry-type automatic densimeter (Brand name: Accupic 1330, Shimadzu Corporation make). Measure in a constant temperature and humidity chamber maintained at 25 ± 1 ° C. and 50 ± 3%. The measurement sample is measured after being left in the constant temperature and humidity chamber for 12 hours or more. A standard 10 cm ³ model of Accupic 1330 was used, and the gas used was helium gas with an initial introduction pressure of 19.5 psig. Also, the condition was that the volume measurement value was consistent within 0.5% by repeated measurement.

[Dimensions of cylindrical carrier]
100 cylindrical carriers were photographed with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation) at a magnification of 1,000 times, and the radial dimension and axial dimension of the carrier were taken from the photograph. Was measured. Further, the axial dimension (axial dimension / radial dimension) with respect to the radial dimension of the cylindrical shape was calculated from this measured value, and the number average value was taken as the average aspect ratio of the cylindrical carrier.

[Volume average particle size]
In a 100 mL beaker, 20 mL of a 1% aqueous solution (electrolytic solution) of sodium chloride (first grade) was added, 0.5 mL of alkylbenzene sulfonate (dispersant) and 3 mg of a toner sample were sequentially added thereto, and ultrasonically dispersed for 5 minutes. . To this, a 1% aqueous solution of sodium chloride (first grade) was added so that the total amount would be 100 mL, and again ultrasonically dispersed for 5 minutes was used as a measurement sample. For this measurement sample, a Coulter Counter TA-III (trade name, manufactured by Coulter, Inc.) was used, and the measurement was performed under the conditions of an aperture diameter of 100 μm and a measurement target particle diameter of 2 to 40 μm on a number basis. Calculated.

[Number average particle diameter of primary particles of magnetic material]
Each of 100 particles randomly taken out from the magnetic material was observed at a magnification of 10,000 times by transmission electron microscope observation, and the particle size of the primary particles was measured by image analysis. The number average particle size was calculated from the obtained measured values.

[Production of Carrier A]
95 parts of a polyester resin (Tg: 60 ° C., Tm: 110 ° C.) and a magnetic material having a saturation magnetization of 50 to 70 (emu / g) in a Mn—Mg—Sr system with a primary particle number average particle size of 1 to 2 μm Five parts were mixed and dispersed in a Henschel mixer for 3 minutes, and melt kneaded and dispersed using a twin screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.) to prepare a resin kneaded product. The operating conditions of the twin screw extruder were a cylinder set temperature of 110 ° C., a barrel rotation speed of 300 revolutions per minute (300 rpm), and a raw material supply speed of 20 kg / hour. The obtained toner kneaded product was spun by a spinning device as shown in FIG. 2 to obtain a yarn-like product having a diameter of 20 to 25 μm. The spinning equipment was such that the pressure inside the spinning nozzle was 90 kg / cm ² , the supply amount of hot air at 160 ° C. was 5 m ³ / min, and the temperature of the nozzle body was 120 ° C. The obtained thread-like material was finely pulverized by a counter jet mill and then classified by a rotary classifier to produce a cylindrical carrier A having an average aspect ratio of 1.2 to 2.0.

[Production of Carrier B]
A cylindrical carrier B was produced in the same manner as the carrier A except that the polyester resin was changed to 98 parts and the magnetic material was changed to 2 parts.

[Production of Carrier C]
A cylindrical carrier C was produced in the same manner as the carrier A except that the polyester resin was changed to 90 parts and the magnetic material was changed to 10 parts.

[Production of Carrier D]
A cylindrical carrier D was produced in the same manner as the carrier A except that the pulverization conditions were changed and the average aspect ratio was less than 1.2.

[Production of Carrier E]
Cylindrical carrier E was produced in the same manner as carrier A except that the pulverization conditions were changed and the average aspect ratio was made larger than 2.0.

[Production of Carrier F]
A carrier F was prepared by coating 5 to 10 parts of silicone resin by spraying on 100 parts of a cylindrical carrier A.

[Production of Carrier G]
Carrier G was obtained by coating 5 to 10 parts of a silicone resin by spraying on 100 parts of ferrite having a number average particle diameter of 1 to 2 μm.

[Production of Carrier H]
For example, 95 parts of a styrene acrylic resin and 5 parts of a Mn—Mg—Sr magnetic material having a primary particle number average particle diameter of 1 to 2 μm can be produced as follows.

  A thermoplastic resin such as styrene acrylic resin, a magnetic material (magnetic powder), and other additives are sufficiently mixed by a mixer. The obtained mixture is melted and kneaded using a kneader such as a heating roll, a kneader, or an extruder. The carrier can be obtained by pulverizing and further classifying the cooled melt-kneaded product.

  The physical property values of the carriers A to H are shown in Table 1.

[Preparation of Toner a]
90.5 parts of polyester resin, colorant C.I. I. 12 parts by weight of a master batch containing 40% by weight of Pigment Red 57: 1 as a colorant, 3 parts by weight of a release agent (trade name: REFINED CARRNAUBA WAX, manufactured by Kato Yoko Co., Ltd.), and a charge control agent (trade name: BONTRON E -84, manufactured by Orient Chemical Co., Ltd.) 2 parts by weight is mixed and dispersed for 3 minutes using a Henschel mixer, and melt kneaded and dispersed using a twin screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.), and toner kneaded. A product was prepared. The operating conditions of the twin screw extruder were a cylinder set temperature of 110 ° C., a barrel rotation speed of 300 revolutions per minute (300 rpm), and a raw material supply speed of 20 kg / hour. The obtained toner kneaded product was solidified and coarsely pulverized. Thereafter, the coarsely pulverized product was finely pulverized by a counter jet mill and classified by a rotary classifier to produce an irregular shaped toner a having a volume average particle diameter of 6.5 μm.

[Preparation of Toner b]
The binder resin fine particles and the colorant are dispersed in water with an anionic surfactant, and the wax fine particles are similarly dispersed in water with a cationic surfactant. These are agglomerated while stirring in a flask, and particles are obtained by fusing at a temperature not lower than the melting point of the binder resin and not higher than the melting point. The excess surfactant is washed from the aqueous particle dispersion, and the desired toner particles are obtained by filtering and drying the particles.

[Preparation of Toner c]
The toner kneaded product obtained in the preparation of the toner a was spun by a spinning device as shown in FIG. 2 to obtain a filamentous material having a diameter of 4 to 5 μm. The spinning equipment was such that the pressure inside the spinning nozzle was 90 kg / cm ² , the supply amount of hot air at 160 ° C. was 5 m ³ / min, and the temperature of the nozzle body was 130 ° C. The obtained thread-like material was finely pulverized by a counter jet mill and then classified by a rotary classifier to prepare a cylindrical toner c having an average aspect ratio of 1.0 to 3.0.

[Preparation of Toner d]
A cylindrical toner d was produced in the same manner as the toner c except that the pulverization conditions were changed and the average aspect ratio was less than 1.0.

[Production of Toner e]
A cylindrical toner e was produced in the same manner as the toner c except that the pulverization conditions were changed and the average aspect ratio was set to be larger than 3.0.
Table 2 shows the physical property values of the toners a to e.

Example 1
An external toner was prepared by mixing 100 parts of toner a with 0.7 part of silica particles having an average primary particle diameter of 20 nm hydrophobized with a silane coupling agent and 1 part of titanium oxide. The external additive toner containing the toner a and the carrier A were mixed so that the toner concentration was 5%, and the two-component developer of Example 1 was obtained.

(Example 2)
A two-component developer of Example 2 was obtained in the same manner as Example 1 except that Carrier B was used instead of Carrier A.

(Example 3)
A two-component developer of Example 3 was obtained in the same manner as Example 1 except that Carrier C was used instead of Carrier A.

Example 4
A two-component developer of Example 4 was obtained in the same manner as Example 1 except that Carrier D was used instead of Carrier A.

(Example 5)
A two-component developer of Example 5 was obtained in the same manner as Example 1 except that Carrier E was used instead of Carrier A.

(Example 6)
A two-component developer of Example 6 was obtained in the same manner as in Example 1 except that Carrier F was used instead of Carrier A.

(Example 7)
A two-component developer of Example 7 was obtained in the same manner as Example 1 except that toner b was used instead of toner a.

(Example 8)
A two-component developer of Example 8 was obtained in the same manner as in Example 1 except that the toner c was used instead of the toner a.

Example 9
A two-component developer of Example 9 was obtained in the same manner as in Example 1 except that the toner d was used instead of the toner a.

(Example 10)
A two-component developer of Example 10 was obtained in the same manner as in Example 1 except that the toner e was used instead of the toner a.

(Comparative Example 1)
A two-component developer of Comparative Example 1 was obtained in the same manner as in Example 1 except that Carrier G was used instead of Carrier A.

(Comparative Example 2)
A two-component developer of Comparative Example 2 was obtained in the same manner as in Example 1 except that Carrier H was used instead of Carrier A.

  The charge rising property of the toner in the two-component developers of Examples and Comparative Examples was evaluated by the following method. Further, the degree of occurrence of carrier adhesion and the resolution when images were formed using the two-component developers of Examples and Comparative Examples were evaluated.

<Charge rising characteristics>
40 g of the two-component developers of Examples and Comparative Examples were put into a polyethylene bottomed cylindrical container having a capacity of 100 mL, and rotated at 100 rpm around the axis of the container. The amount of charge was measured 0.5 minutes, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes, and 120 minutes after the start of rotation. For the measurement of the charge amount, a suction type small charge amount measuring device Model 2A10HS-2 manufactured by Trek Japan Co., Ltd. was used. Among the measured charge amounts after the elapse of each time, the maximum value is defined as Qm, and the time until the charge amount reaches 90% or more of Qm is defined as the charge rise time. It can be said that the shorter the charging rise time, the better the charge rising property. The evaluation criteria are as follows.
○: Good. Charge rise time is 5 minutes or less.
Δ: No problem in actual use. Charge rise time is over 5 minutes and less than 10 minutes.
X: Defect. Charge rise time exceeds 10 minutes.

<Carrier adhesion>
The two-component developers of Examples and Comparative Examples are filled in a commercial copying machine (trade name: MX-3500, manufactured by Sharp Corporation), and white on A4 size recording paper defined in Japanese Industrial Standard (JIS) P0138. A solid image was formed. The number of carriers adhering to the photoreceptor after the formation of the solid image was visually confirmed, and the degree of carrier adhesion was evaluated as follows.
○: Good. The number of carriers attached is 10 or less.
Δ: No problem in actual use. The number of carriers attached is 11 or more and 20 or less.
X: Defect. The number of carriers attached is 21 or more.

<Resolution>
An original image of a fine line having a line width of exactly 100 μm under the condition that a halftone image having an image density of 0.3 and a diameter of 5 mm can be copied with an image density of 0.3 to 0.5 by the copying machine. The original to be formed was copied, and the obtained copy image was used as a measurement sample. The line width of a thin line formed on the measurement sample was measured by an indicator from a monitor image obtained by enlarging the measurement sample 100 times using a particle analyzer (trade name Luzex 450, manufactured by Nireco Corporation). The image density is an optical reflection density measured by a reflection densitometer (trade name: RD-918, manufactured by Macbeth). Since the thin line has irregularities and the line width varies depending on the measurement position, the line width is measured at a plurality of measurement positions and an average value is obtained, and this line width is taken as the line width of the measurement sample. The line width of the measurement sample was divided by the original line width of 100 μm, and the obtained value was multiplied by 100 to obtain a fine line reproducibility value. The closer the value of the fine line reproducibility is to 100, the better the fine line reproducibility and the better the resolution. The evaluation criteria are as follows.
A: Very good. The value of fine line reproducibility is 100 or more and less than 105.
○: Good. The fine line reproducibility value is 105 or more and less than 115.
Δ: No problem in actual use. The fine line reproducibility value is 115 or more and less than 125.
X: Defect. Fine line reproducibility is 125 or more.

<Comprehensive evaluation>
The evaluation criteria for comprehensive evaluation are as follows.
A: Very good. There are no Δ and × in the evaluation results.
○: Good. There is no x in the evaluation result, and there is one Δ.
Δ: No problem in actual use. There are no X in the evaluation result, and there are two or more Δ.
X: Defect. There is a cross in the evaluation result.
The evaluation results are shown in Table 3.

  From Table 3, it can be seen that the two-component developer using the carrier within the prescribed range of the present invention has a fast toner charge rise, prevents carrier adhesion, and can form a high-definition image.

It is process drawing which shows the procedure of the manufacturing method of the carrier which is one Embodiment of this invention. It is a systematic diagram which shows schematically the structure of the spinning apparatus 1 used at an extrusion cooling process. 2 is an enlarged perspective view showing the vicinity of a spinning nozzle 5 provided in the spinning device 1. FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 100 that is an embodiment of the present invention. It is sectional drawing which shows typically the structure of the developing means 114 which is embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spinning apparatus 2 Kneaded material feeding part 3 Fine-refining part 4 Cooling part 5 Spinning nozzle 5a Nozzle main body 5b Kneaded substance discharge die 6 Gear pump 7 Flow path 8 Kneading machine 9 Hot air blowing part 10 Blower 11 Heater 12 Nozzle cover 12a Hot air flow passage DESCRIPTION OF SYMBOLS 13 Hot-air supply direction 14 Cold-air blower 15 Crusher 16 Conveying means 17 Melt kneaded material supply direction 100 Image forming apparatus 114 Developing means

Claims (12)

  A magnetic substance-containing resin carrier comprising a resin and a magnetic substance and having a cylindrical shape.   2. The magnetic substance-containing resin carrier according to claim 1, which is produced by a spinning method. The spinning method
A melt-kneading step of melt-kneading the resin and the magnetic material;
An extrusion cooling step in which the melt-kneaded product obtained in the melt-kneading step is extruded into a filament and cooled;
3. A magnetic substance-containing resin carrier according to claim 2, further comprising a pulverizing step of pulverizing the thread-like solidified material obtained in the extrusion cooling step to obtain a cylindrical magnetic substance-containing resin carrier. The magnetic substance-containing resin carrier according to any one of claims 1 to ³ , wherein a true specific gravity is 2.5 g / cm ³ or more and 4.0 g / cm ³ or less.   5. The magnetic substance-containing resin carrier according to claim 1, wherein the surface is coated with a coating agent.   6. The magnetic substance-containing resin carrier according to claim 5, wherein the coating agent contains a silicone resin or a fluororesin.   An aspect ratio is 1.2 or more and 2.0 or less, The magnetic body containing resin carrier as described in any one of Claims 1-6 characterized by the above-mentioned.   A two-component developer comprising: the magnetic substance-containing resin carrier according to any one of claims 1 to 7; and a toner containing at least a binder resin and a colorant.   The two-component developer according to claim 8, wherein the toner has a cylindrical shape.   The two-component developer according to claim 9, wherein an aspect ratio of the toner is 1.0 or more and 3.0 or less.   A developing device that performs development using the two-component developer according to claim 8. An image forming apparatus that forms an image using the developing device according to claim 11.