JP2014153469A - Carrier for electrostatic charge image development, developer for electrostatic charge image development, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development that suppresses the occurrence of image omission at a rear end of an image and white streaks in an image.SOLUTION: A carrier for electrostatic charge image development includes magnetic particles having a ferrite component represented by the general formula MFeO(wherein 0≤x≤1, and M represents a metal element); and when a peak intensity of FeOof the magnetic particles obtained by an X-ray diffraction method is A, and a peak intensity of FeOof particles obtained through pulverization processing to the magnetic particles is C, the peak intensity A is within a range of 150 or more and 500 or less; the peak intensity C is within a range of 25 or more and 80 or less; and a peak intensity ratio of the peak intensity A to the peak intensity C (A/C) is within a range of 2 or more and 20 or less.

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developing developer, a process cartridge, and an image forming apparatus.

  A method for visualizing image information through an electrostatic charge image such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image is formed on an image carrier by a charging and exposure process (latent image forming process), and an electrostatic charge image developing toner (hereinafter sometimes simply referred to as “toner”). The electrostatic latent image is developed with a developer for developing an electrostatic charge image (hereinafter sometimes referred to simply as “developer”) (development process), and visualized through a transfer process and a fixing process. The developer used here imparts an appropriate amount of positive or negative charge to the toner by triboelectrically charging both the carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and the toner. The two-component developer and the one-component developer used alone, such as magnetic toner, are roughly classified. In particular, the two-component developer is widely used for reasons such as easy design because the carrier itself has functions such as agitation, conveyance, and charging, and the functions required for the developer can be separated. ing.

  In recent years, there has been a demand for higher image quality of images formed by electrophotographic image forming apparatuses, higher process speed, long-term stability, etc. Various studies have been made.

For example, Patent Document 1 discloses Fe ₂ O obtained by an X-ray diffraction method in a carrier whose main component is a material represented by the general formula Mn _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1). _A carrier is disclosed in which the difference between the peak intensity ratio of ₃ and MnFe ₂ O ₄ before and after pulverization is 0.015 or less in absolute value.

  For example, Patent Document 2 discloses a carrier in which a part of magnetite is converted into hematite in a carrier mainly composed of magnetite.

For example, in Patent Document 3, the value of the peak area ratio (Sh / Sm) of the strongest diffraction peak area Sh of the Fe ₂ O ₃ crystal to the strongest diffraction peak area Sm of the Fe ₃ O ₄ crystal obtained by the X-ray diffraction method is described. A carrier in the range of 0.01 to 1.0 is disclosed.

JP 2011-248311 A JP 61-114249 A JP 2000-181145 A

  An object of the present invention is to provide a carrier for developing an electrostatic charge image, a developer for developing an electrostatic charge image, a process cartridge, and an image forming apparatus in which occurrence of image dropout and image whiteout in the rear end portion of the image is suppressed. It is in.

The invention according to claim 1 has magnetic particles containing a ferrite component represented by the general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element), and X-rays the peak intensity of Fe ₂ O ₃ of the magnetic particles obtained by diffraction method is a, wherein, when the peak intensity of Fe ₂ O ₃ particles after magnetic particles to pulverization treatment is C, the peak intensity a 150 The peak intensity C is in the range of 25 or more and 80 or less, and the peak intensity ratio (A / C) of the peak intensity A to the peak intensity C is in the range of 2 or more and 20 or less. It is a carrier for developing a charge image.

  The invention according to claim 2 is the electrostatic image developing carrier according to claim 1, wherein the metal element M contains at least one metal selected from strontium (Sr) and calcium (Ca).

  The invention according to claim 3 is an electrostatic charge image developing developer containing the electrostatic charge image developing carrier according to claim 1 or 2.

  The invention according to claim 4 contains the developer for developing an electrostatic image according to claim 3, and develops the electrostatic latent image formed on the surface of the image carrier with the developer for developing an electrostatic image. It is a process cartridge provided with developing means for forming a toner image.

  According to a fifth aspect of the present invention, there is provided an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and the electrostatic latent image. An image forming apparatus comprising: a developing unit that develops an image with the developer for developing an electrostatic image according to claim 3 to form a toner image; and a transfer unit that transfers the toner image to a transfer target.

According to the first aspect of the invention, the Fe ₂ O ₃ of the magnetic particles obtained by the X-ray diffraction method has a peak intensity A in the range of 150 to 500, and the Fe ₂ O of the particles after pulverizing the magnetic particles. _{3 in which} the peak intensity C is in the range of 25 to 80 and the peak intensity ratio of the peak intensity A to the peak intensity C is not in the range of 2 to 20; And an electrostatic charge image developing carrier in which the occurrence of white spots in the image is suppressed.

According to the second aspect of the present invention, the Fe ₂ O ₃ of the magnetic particles obtained by the X-ray diffraction method has a peak intensity A in the range of 150 to 500, and the Fe ₂ O of the particles after pulverizing the magnetic particles. _{3 in which} the peak intensity C is in the range of 25 to 80 and the peak intensity ratio of the peak intensity A to the peak intensity C is not in the range of 2 to 20 and the general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element) M indicating a metal element of the ferrite component does not include at least one metal selected from strontium (Sr) and calcium (Ca) Compared to the case, there is provided an electrostatic charge image developing carrier in which occurrence of image omission at the rear end of the image is suppressed and occurrence of image omission is further suppressed.

According to the invention of claim 3, the Fe ₂ O ₃ peak intensity A of the carrier magnetic particles obtained by the X-ray diffraction method is in the range of 150 to 500, and the particles after the pulverization of the magnetic particles Compared with the case where the peak intensity C of ₂ O ₃ is in the range of 25 to 80 and the peak intensity ratio of the peak intensity A to the peak intensity C is not in the range of 2 to 20, the image at the rear end of the image There is provided a developer for developing an electrostatic charge image in which occurrence of omission is suppressed and occurrence of image omission is further suppressed.

According to the invention of claim 4, the Fe ₂ O ₃ peak intensity A of the carrier magnetic particles obtained by the X-ray diffraction method is in the range of 150 to 500, and the particles after the magnetic particles are pulverized. Compared with the case where the peak intensity C of ₂ O ₃ is in the range of 25 to 80 and the peak intensity ratio of the peak intensity A to the peak intensity C is not in the range of 2 to 20, the image at the rear end of the image There is provided a process cartridge in which occurrence of omission is suppressed and occurrence of image omission is further suppressed.

According to the fifth aspect of the invention, the Fe ₂ O ₃ peak intensity A of the carrier magnetic particles obtained by the X-ray diffraction method is in the range of 150 to 500, and the particles after the pulverization of the magnetic particles Compared with the case where the peak intensity C of ₂ O ₃ is in the range of 25 to 80 and the peak intensity ratio of the peak intensity A to the peak intensity C is not in the range of 2 to 20, the image at the rear end of the image There is provided an image forming apparatus in which occurrence of omission is suppressed and occurrence of image omission is further suppressed.

1 is a schematic configuration diagram illustrating an example of a configuration of a developing device used in an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a state in which toner is supplied from a developing device to an electrophotographic photosensitive member. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. It is a schematic structure figure showing an example of a process cartridge concerning an embodiment of the present invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic configuration diagram illustrating an example of a configuration of a developing device used in an image forming apparatus according to an embodiment of the present invention. Developer is accommodated in the case 51 of the developing device 50 shown in FIG. A developing roll 52 is provided in the opening of the case 51 on the electrophotographic photoreceptor 20 side so as to face the electrophotographic photoreceptor 20. The developing roll 52 is a rotating body and is a cylindrical member. The developing roll 52 includes a magnet roll 521 disposed in a state of being fixed inside, and a developing sleeve 522 that is rotatably provided on the outer periphery of the magnet roll 521. The magnet roll 521 generates a magnetic field for holding the developer on the peripheral surface of the developing roll 52. The developing sleeve 522 is a non-magnetic sleeve, and is supplied with a developing bias voltage having a predetermined developing potential, and is rotated in the direction of arrow D in the drawing. The development potential here is, for example, −600V. In the developing device 50, a supply roll 53 that supplies the developer to the developing roll 52 while stirring the developer is provided on the further back side of the developing roll 52. On the further back side of the supply roll 53, a stirring roll 54 is provided.

  The developing roll 52 is rotated while the developer is held on the peripheral surface by the magnetic attractive force of the magnet roll 521. More specifically, the developer is held on the developing sleeve 522 of the developing roll 52. This developer forms a so-called magnetic brush that is arranged in a bundle along the magnetic field lines by the magnetic force applied by the magnet roll 521. The magnetic brush is conveyed further downstream in the rotational direction after the layer thickness is regulated by the layer thickness regulating member 511 as the developing sleeve 522 rotates. The cover portion 512 of the case 51 is provided to prevent the toner scattered from the developing roll 52 and the electrophotographic photosensitive member 20 from reaching another place in the image forming apparatus.

  FIG. 2 is a schematic diagram illustrating a state in which toner is supplied from the developing device to the electrophotographic photosensitive member. The white circles shown in FIG. 2 represent an electrostatic charge image developing carrier (hereinafter sometimes referred to simply as a carrier), and the hatched circles represent an electrostatic charge image developing toner (hereinafter simply referred to as a toner). May be called). The developing roll 52 is rotated in the circumferential direction, which is the arrow D direction, while holding the magnetic brush as the developer by magnetic adsorption. Then, in the supply path T1 including the region where the distance between the developing roll 52 and the electrophotographic photosensitive member 20 is minimized, the magnetic brush is brought into contact with or close to the electrophotographic photosensitive member 20, and the toner in the magnetic brush is electronically transferred. The latent image on the photographic photosensitive member 20 is supplied. At this time, an electric attractive force acts due to an electric field (hereinafter referred to as “developing electric field”) generated by a potential difference between the developing potential of the developing sleeve 522 and the potential of the latent image formed on the electrophotographic photosensitive member 20. The toner moves and adheres to the surface of the photoreceptor 20 (development).

  Generally, the lower the carrier resistance, the more easily the charge charged in the toner is transferred to the carrier side at the time of development. Therefore, carrier scattering occurs in which the carrier moves to the electrophotographic photoreceptor 20 together with the toner. Conceivable. It is said that this carrier scattering is likely to occur particularly under high temperature (for example, 28 ° C. or higher) and high humidity (for example, 85% RH or higher) conditions. When the carrier moves to the electrophotographic photosensitive member 20, no toner is placed on that portion, so that white spots may occur in an image formed on the recording medium.

  On the other hand, the higher the resistance of the carrier, the easier the charge opposite to the charge charged on the toner is accumulated in the carrier during development, and the toner that is going to move to the electrophotographic photoreceptor 20 is attracted to the carrier side. Since it adheres to the carrier again, there may be a case where an image dropout occurs at the rear end portion of the image formed on the recording medium (so-called starvation occurs). The rear end portion of the image is a boundary region when the low density solid image and the high density solid image are adjacent to each other. In general, it is likely to occur when a low density image with an image coverage of about 20% and a high density image with 100% are adjacent to each other.

  As described above, suppression of white spots in the image and image dropout at the rear end portion of the image is contradictory from the viewpoint of carrier resistance. However, the present inventors have developed the electrostatic charge image developing carrier according to the present embodiment. It was found that the occurrence of white spots in the image and the occurrence of missing images at the rear end of the image are both suppressed by using. Hereinafter, the electrostatic image developing carrier according to the present embodiment will be described.

<Carrier for developing electrostatic image>
The electrostatic charge image developing carrier according to the present embodiment comprises magnetic particles containing a ferrite component represented by the general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element). Have. When the peak intensity of Fe ₂ O ₃ magnetic particles obtained by X-ray diffraction method is A, the peak intensity of Fe ₂ O ₃ particles after pulverizing the magnetic particles is C, peak intensity A is 150 to 500, peak intensity C is 25 to 80, and peak intensity ratio of peak intensity A to peak intensity C (peak intensity A / peak intensity C) is 2 to 20 is there. Here, the peak intensity A of Fe ₂ O ₃ magnetic particles obtained by X-ray diffraction method, the peak intensity of Fe ₂ O ₃ magnetic particles before pulverization, when used as an electrostatic image developing carrier It is the peak intensity of Fe ₂ O ₃ of the magnetic particles. The measurement conditions and pulverization treatment of the X-ray diffraction method will be described later (see Examples). The peak of Fe ₂ O ₃ is observed in the range where the X-ray diffraction angle is 33.0 deg or more and 34.0 deg or less by X-ray diffraction measurement under the conditions described later.

And Fe ₂ O ₃ peak intensity A range of 150 to 500, _Fe 2 _O and ₃ peak intensity C the range of 25 to 80., the peak intensity ratio of the peak intensity A to the peak intensity C (peak intensity A / By setting the peak intensity C) in the range of 2 or more and 20 or less, it can be said that more Fe ₂ O ₃ is present on the surface of the magnetic particle than in the magnetic particle. The ferrite represented by the general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element) is a crystal of metal ions and oxygen ions. The metal ion is composed of a divalent iron ion and a trivalent iron ion, and has a structure in which electrons of the iron ion easily move through oxygen. Therefore, the electric resistance is lower than that of Fe ₂ O ₃ . On the other hand, since Fe ₂ O ₃ is composed only of trivalent iron ions, the movement of electrons hardly occurs. Therefore, the electrical resistance is higher than that of ferrite. Therefore, in a state where more Fe ₂ O ₃ is present on the magnetic particle surface than inside the magnetic particle, it is considered that the resistance of the magnetic particle surface is higher than the resistance inside the magnetic particle.

As described above, carrier scattering is considered to occur due to transfer of toner charge to the carrier during development. However, when the peak intensities A and C and the peak intensity A / peak intensity C of Fe ₂ O ₃ satisfy the above ranges, the resistance of the magnetic particle surface becomes higher than the internal resistance, so that the charge of the toner is transferred to the carrier. It is considered that the carrier scattering is suppressed and the occurrence of white spots in the image is suppressed. Further, as described above, it is considered that the image omission (starvation) at the rear end portion of the image is caused by accumulation of electric charges in the carriers. However, when the peak intensities A and C and the peak intensity A / peak intensity C of Fe ₂ O ₃ satisfy the above ranges, the resistance inside the magnetic particles becomes lower than the resistance on the surface, so that it is difficult for charges to accumulate in the carriers. Therefore, it is considered that occurrence of image omission at the rear end portion of the image is suppressed. That, _Fe is the peak intensity A 2 _{O 3} in the range of 150 to 500, the range of peak intensity C is 25 to 80. of _Fe 2 _{O 3,} the peak intensity ratio of the peak intensity A to the peak intensity C ( By using a carrier containing magnetic particles satisfying a range of 2 to 20 in terms of peak intensity A / peak intensity C), both occurrence of image blanking and image missing at the rear end of the image are suppressed.

Since Fe ₂ O ₃ is not a magnetic substance, when the peak intensity A of Fe ₂ O ₃ of the magnetic particles obtained by the X-ray diffraction method exceeds 500, compared to the case where the peak intensity A is 500 or less, Magnetization is reduced, carrier scattering occurs, and occurrence of white spots in the image is not suppressed. Further, when the Fe ₂ O ₃ peak intensity A of the magnetic particles obtained by the X-ray diffraction method is less than 150, it is sufficient to increase the resistance of the magnetic particle surface compared to the case where the peak intensity A is 150 or more. The white spots are not suppressed. When the peak intensity C of Fe ₂ O ₃ exceeds 80, the resistance in the vicinity of the magnetic particle surface cannot be sufficiently increased as compared with the case where the peak intensity C is 80 or less, and image loss occurs at the rear end of the image. Not suppressed. Further, when the peak intensity C of Fe ₂ O ₃ is less than 25, the resistance inside the magnetic particles becomes lower than that of the peak intensity C of 25 or more (especially under high temperature and high humidity), white spots are likely to occur. Become. When the peak intensity ratio of the peak intensity A to the peak intensity C is less than 2, the resistance on the surface of the magnetic particle and the resistance inside the magnetic particle are compared with the case where the peak intensity ratio of the peak intensity A to the peak intensity C is 2 or more. And the occurrence of white spots in the image or the occurrence of image dropout at the rear edge of the image is not suppressed. Further, when the peak intensity ratio of the peak intensity A to the peak intensity C exceeds 20, the resistance on the surface of the magnetic particle and the inside of the magnetic particle are compared with the case where the peak intensity ratio of the peak intensity A to the peak intensity C is 20 or less. The difference from the resistance increases, and the occurrence of image omission at the rear end of the image is not suppressed.

In the ferrite represented by the general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element), the metal element M is lithium (Li), calcium (Ca), strontium ( Sr), tin (Sn), copper (Cu), zinc (Zn), barium (Ba), iron (Fe), titanium (Ti), nickel (Ni), aluminum (Al), cobalt (Co), manganese ( Although it contains at least one metal selected from Mn), magnesium (Mg) and the like, it preferably contains at least one metal selected from strontium (Sr), calcium (Ca) and the like. By including strontium (Sr) and calcium (Ca) in the ferrite, the resistance of the magnetic particles becomes higher than when strontium (Sr) and calcium (Ca) are not included, and the image is missing at the rear edge of the image. Occurrence is further suppressed.

  In addition to the above-mentioned ferrite, the carrier of the present embodiment includes, for example, magnetic metals such as iron, steel, nickel, cobalt, magnetic oxides such as magnetite, and magnetic particles other than ferrite such as resin particles in which magnetic particles are dispersed internally. Etc. may be included. However, when the carrier of this embodiment contains other magnetic particles in addition to ferrite, the content of ferrite is preferably 80% by mass or more based on the entire carrier. When the ferrite content is less than 80% by mass with respect to the entire carrier, it may be difficult to suppress the occurrence of whiteout in the image and image loss at the rear end of the image.

  The volume average particle size of the magnetic particles of the present embodiment is preferably in the range of 20 μm to 100 μm, for example. If the volume average particle size of the magnetic particles is less than 20 μm, carrier scattering may be difficult to suppress, and if it exceeds 100 μm, it may be difficult to charge the toner as uniformly as possible when the carrier is used.

  The method for producing the electrostatic charge image developing carrier of the present embodiment is not particularly limited, but for example, a preliminary firing step of firing a carrier material containing an iron compound, a manganese compound, a magnesium compound, a calcium compound, a strontium compound, and the like, After the pre-baking step, a pulverizing step of pulverizing the baked carrier material, after the pulverizing step, a granulating step of granulating the pulverized carrier material, and a main baking step of baking the carrier material after the granulating step And it is preferable that it is a manufacturing method including the additional baking process of baking a carrier material further after the said main baking process.

  The iron compound, manganese compound, magnesium compound, calcium compound, strontium compound and the like used as the carrier material may have any composition such as an oxide, a hydroxide, and a carbonate.

  The firing temperature in the preliminary firing step is not particularly limited, but is preferably 800 ° C. or higher and 1200 ° C. or lower, for example. The oxygen concentration in the pre-baking step is not particularly limited, but is preferably in the range of 1% to 10%, for example. The firing time in the pre-baking step depends on the composition of the carrier material, the firing temperature, the degree of drying, etc., but is preferably 0.5 hours or more and 48 hours or less, preferably 1 hour or more and 12 hours or less. More preferably. A known apparatus is used for the pre-baking process, and the baking of the main baking process and the additional baking process described later, and examples thereof include an electric furnace and a rotary kiln.

  It is preferable to include a pulverization step for pulverizing the baked carrier material after the pre-baking step, and a granulation step for granulating the pulverized carrier material after the pulverization step. In the pulverization step, a known apparatus is used, and examples thereof include a wet ball mill. In the pulverization step, it is preferable to pulverize until the volume average particle diameter of the calcined carrier material is 1 μm or more and 10 μm or less. In the granulation step, a known device is used, and examples thereof include a spray dryer. Moreover, it is preferable to include the drying process which dries the granulated carrier material after a granulation process.

  The firing temperature in the main firing step is not particularly limited, but is preferably 800 ° C. or higher and 1400 ° C. or lower, and more preferably 800 ° C. or higher and 1200 ° C. or lower. The oxygen concentration in the main baking step is not particularly limited, but is preferably in the range of 1% to 8%, for example. The firing time in the main firing step depends on the composition of the carrier material, the firing temperature, the degree of drying, and the like, but is preferably 1 hour or longer and 24 hours or shorter, and preferably 2 hours or longer and 12 hours or shorter. Is more preferable.

In this embodiment, by adjusting the firing temperature and oxygen concentration in the additional firing step, the peak intensity A of Fe ₂ O ₃ of the magnetic particles obtained by the X-ray diffraction method is in the range of 150 to 500, and the magnetic particles are The peak intensity C of Fe ₂ O ₃ of the particles after pulverization is in the range of 25 to 80, and the peak intensity ratio of the peak intensity A to the peak intensity C (peak intensity A / peak intensity C) is 2 to 20 It is preferable to adjust to the range. The adjustment of the peak intensities A and C of Fe ₂ O ₃ and the peak intensity A / peak intensity C is not limited to being performed in the additional firing step, and may be performed in the main firing step or the temporary firing step. Good.

Higher firing temperatures in the additional baking step, the higher the amount of Fe ₂ O ₃ inside from the surface of the magnetic particles, the higher the oxygen concentration, in the interior from the surface of the magnetic particles Fe ₂ O ₃ is abundant and easy. Therefore, the firing temperature in the additional firing step is lower than the firing temperature in the main firing step from the viewpoint of satisfying the above ranges of the peak strengths A and C and the peak strength A / peak strength C of Fe ₂ O ₃ of the magnetic particles. Preferably, the temperature is, for example, in the range of 650 ° C. to 950 ° C. In addition, the oxygen concentration in the additional baking step is preferably higher than the oxygen concentration in the main baking step, and is preferably in the range of 10% to 30%, for example. The firing time in the additional firing step is, for example, preferably 0.5 hours or more and 24 hours or less, and preferably 1 hour or more and 6 hours or less, depending on the composition of the carrier material, the firing temperature, and the like. More preferred.

Further, in the additional firing step, additional firing is performed from the viewpoint that the peak intensity A and C of the Fe ₂ O ₃ of the magnetic particles and the peak intensity A / peak intensity C satisfy the above ranges, etc., from maintaining the oxygen concentration constant. It is preferable to increase the oxygen concentration during the process. For example, baking is performed at an oxygen concentration in the atmosphere for 1 hour or more, and thereafter baking is performed at an oxygen concentration higher than the oxygen concentration in the atmosphere, for example, 25% or more for 1 hour or more. preferable.

  In addition, the method for producing an electrostatic charge image developing carrier according to the present embodiment may include a coating layer forming step of coating a resin or the like on the surface of the magnetic particle containing the ferrite component obtained through the additional baking step. . Moreover, you may add external additives, such as electroconductive particle and an electrical strength regulator, to the coating layer formed by the coating layer formation process.

  As the material constituting the coating layer, for example, an insulating resin or the like is used. Examples of the method for coating the surface of the magnetic particles on the surface of the magnetic particles include a wet method using a solvent and a dry method using no solvent.

  Examples of the wet method include a dipping method in which a resin and a conductive material are added to a soluble solvent to form a coating layer forming solution, and magnetic particles are immersed in the coating layer forming solution. Spray method in which the solution is sprayed on the surface of the magnetic particles, fluidized bed method in which the coating solution for forming the coating layer is sprayed in a state where the magnetic particles are suspended by fluidized air, etc., and the magnetic particles and the coating layer forming solution are mixed in a kneader coater Then, there is a kneader coater method for removing the solvent.

  As a dry method, resin particles or the like are synthesized by an emulsion polymerization method or a suspension polymerization method, or resin particles obtained by emulsifying and dispersing a synthesized resin or the like in water are mixed with magnetic particles. For example, there is a method in which the surface of magnetic particles is coated with a mechanical impact force and, if necessary, heated and melted above the glass transition point of the resin to form a coating layer.

  After the coating layer is formed on the magnetic particles by a wet method, a dry method, or the like, for example, an external additive or the like is added, mixed and stirred, and the external additive or the like is attached onto the coating layer. Then, the carrier is obtained by sieving the particles to which the external additive or the like is adhered with a sieving net or the like.

  The material constituting the coating layer of the present embodiment is not particularly limited. For example, a methacrylate resin and a derivative thereof, a styrene-methacrylate copolymer resin, a silicone resin and a modified product thereof, a fluororesin, and a vinyl And vinylidene resins, olefin resins such as polyethylene and polypropylene, phenol resins, polyester resins, epoxy resins, amino resins, and the like.

  As a coating amount of the coating layer, for example, a range of 0.5 wt% or more and 5 wt% or less is preferable with respect to the entire carrier. When the coating amount of the coating layer is less than 0.5% by weight, the effect of improving the charging property is small, and when it is 5% by weight or more, the coating layer may be easily peeled off from the magnetic particles.

  In the present embodiment, in the coating layer, cationic surfactants such as laurylamine hydrochloride and stearylamine hydrochloride, anionic surfactants such as potassium laurate and sodium oleate, polyoxyethylene octyl ether, polyoxyethylene lauryl ether It may contain known surfactants such as nonionic surfactants.

  In the present embodiment, the coating layer may contain a known charge control agent such as a nigrosine dye or a benzimidazole compound.

  The average film thickness of the resin coating layer is preferably 0.5 μm or more and 3 μm or less from the viewpoint of expressing the volume resistivity of the carrier that is stable over time.

The volume specific resistance value of the carrier according to this embodiment is 10 ⁶ Ω · cm or more and 10 ¹⁴ Ω · cm or less at 1000 V corresponding to the upper and lower limits of a normal development contrast potential from the viewpoint of achieving high image quality. Preferably, it is 10 ⁸ Ω · cm or more and 10 ¹³ Ω · cm or less. When the volume specific resistance value of the carrier is less than 10 ⁶ Ω · cm, the reproducibility of the thin line may be deteriorated. On the other hand, when the volume resistivity value of the carrier exceeds 10 ¹⁴ Ω · cm, reproduction of a black solid image or a halftone image may be deteriorated.

  As a volume average particle diameter of the carrier which concerns on this embodiment, 20 micrometers or more and 100 micrometers or less are preferable, for example. If the volume average particle diameter of the carrier is less than 20 μm, it may be easily developed together with the toner, and if it exceeds 100 μm, it may be difficult to charge the toner substantially uniformly.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image (developer) according to this embodiment contains the carrier for developing an electrostatic charge image according to this embodiment and the toner for developing an electrostatic charge image. The developer according to this embodiment is prepared by mixing the carrier and toner according to this embodiment at an appropriate blending ratio. The carrier content ((carrier) / (carrier + toner) × 100) is preferably in the range of 85 to 99% by mass, more preferably in the range of 87 to 98% by mass, and 89% by mass or more. The range of 97% by mass or less is more preferable.

  Hereinafter, the toner used in the developer for developing an electrostatic charge image according to the exemplary embodiment will be described.

  The toner used in this embodiment contains at least a binder resin and a colorant, and if necessary, a release agent and other components. In addition to the so-called toner particles having the above-described configuration, an external additive (hereinafter sometimes simply referred to as “external additive”) is added to the toner used in the exemplary embodiment for various purposes. Good.

  For the toner used in this embodiment, a known binder resin, various colorants, and the like may be used. As the binder resin in the toner used in this embodiment, in addition to the polyester resin, polyolefin resin, copolymer of styrene and acrylic acid or methacrylic acid, polyvinyl chloride, phenol resin, acrylic resin, methacrylic resin, poly Vinyl acetate, silicone resin, modified polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, polyether polyol resin, etc. may be used alone You may use together.

  Examples of the colorant in the toner used in the exemplary embodiment include cyan colorants such as C.I. I. Pigment blue 1, C.I. I. Pigment Blue 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 17, 23, 60, 65, 73, 83, 180, C.I. I. Vat cyan 1, 3 and 20, etc., bitumen, cobalt blue, alkali blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indanthrene blue BC cyan pigment, C.I. I. Cyan dyes such as solvent cyan 79 and 162 may be used.

  Examples of magenta colorants include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90 112, 114, 122, 123, 163, 184, 202, 206, 207, and 209, pigment violet 19 magenta pigments, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 30, 49, 81, 82, 83, 84, 100, 109, 121, C . I. Disper thread 9, C.I. I. Basic Red 1, 2, 9, 9, 13, 14, 15, 17, 17, 18, 22, 23, 24, 27, 29, 32, 34, the same 35, 36, 37, 38, 39, 40, etc. Magenta dyes, etc., Bengala, Cadmium Red, Lead Tan, Mercury Sulfide, Cadmium, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red, Calcium Salt, lake red D, brilliant carmine 6B, eosin lake, rotamin lake B, alizarin lake, brilliant carmine 3B and the like may be used.

  Examples of yellow colorants include C.I. I. Pigment Yellow 2, 3, 15, 15, 16, 17, 97, 180, 185, 139, and the like may be used.

  Further, in the case of black toner, for example, carbon black, activated carbon, titanium black, magnetic powder, Mn-containing nonmagnetic powder, or the like may be used.

  The toner used in the exemplary embodiment may contain a charge control agent, and nigrosine, a quaternary ammonium salt, an organometallic complex, a chelate complex, or the like may be used.

Furthermore, in this embodiment, various resin powders, inorganic compounds, and the like may be added as external additives to the surface of the toner particles as a surface modifier. As the resin powder, polymethyl methacrylate resin (PMMA), nylon, melamine, benzoguanamine, spherical particles such as fluorine resin, and the like can be used. Examples of various known inorganic compounds include SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O, and Na ₂ O. , ZrO ₂ , CaO · SiO ₂ , CaCO ₃ , K ₂ O (TiO ₂ ) _n , MgCO ₃ , Al ₂ O ₃ · 2SiO ₂ , BaSO ₄ , MgSO _{4 and the} like, preferably SiO ₂ , Examples thereof include TiO ₂ and Al ₂ O _3, but are not limited to these, and one or more of these may be used in combination. The volume average particle size of the external additive is preferably 0.1 μm or less, and the addition amount of the external additive is, for example, from 0.1% by mass to 20% by mass with respect to 100% by mass of the toner particles. Range.

  Furthermore, the toner used in the exemplary embodiment preferably contains a release agent. Release agents include ester wax, polyethylene, polypropylene or a copolymer of polyethylene and polypropylene, polyglycerin wax, microcrystalline wax, paraffin wax, carnauba wax, sazol wax, montanic acid ester wax, deoxidized carnauba wax, palmitic Unsaturated fatty acids such as acid, stearic acid, montanic acid, brandic acid, eleostearic acid, valinalic acid, stearic alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, melyl alcohol, or even longer chain Saturated alcohols such as long-chain alkyl alcohols having an alkyl group, polyhydric alcohols such as sorbitol, linoleic acid amide, oleic acid amide, lauric acid Fatty acid amides such as methylenebisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene bisstearic acid amide, saturated fatty acid bisamides, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide N, N′-dioleyl adipate amide, N, N′-dioleyl sebacic acid amide, etc., unsaturated fatty acid amides, m-xylene bisstearic acid amide, N, N ′ distearyl isophthalic acid amide, etc. Aromatic bisamides, fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate, magnesium stearate (generally called metal soaps), aliphatic hydrocarbon waxes and vinyls such as styrene and acrylic acid Using monomers Methyl ester compounds and the like having a hydroxyl group obtained by hydrogenation such as vegetable oils; waxes obtained by shift of fatty acids with polyhydric alcohols of the partial esters of behenic acid monoglyceride.

  In this embodiment, the method for producing the toner (toner particles) is not particularly limited, but it is preferably produced by a wet production method in order to obtain high image quality. As a wet manufacturing method, the polymerizable monomer of the binder resin is emulsion-polymerized, and the formed binder resin dispersion is mixed with a dispersion of a colorant, a release agent, and, if necessary, a charge control agent. An emulsion aggregation method in which toner particles are obtained by agglomeration and heat fusion, a solution of a polymerizable monomer and a colorant, a release agent, and a charge control agent as necessary in order to obtain a binder resin in an aqueous solvent Suspension polymerization method in which the polymer is suspended and polymerized, a binder resin, a colorant, a release agent, and a solution suspension method in which a solution such as a charge control agent is suspended in an aqueous solvent and granulated if necessary. Can be mentioned. In addition, a manufacturing method may be performed in which the toner particles obtained by the above method are used as a core, and resin particles are further adhered and heat-fused to have a core-shell structure. Further, toner particles obtained by a general pulverization classification method may be used.

<Image forming apparatus and process cartridge>
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and the static The image forming apparatus includes a developing unit that develops the electrostatic latent image with the developer for developing an electrostatic image according to the exemplary embodiment to form a toner image, and a transfer unit that transfers the toner image to a recording medium. The image forming apparatus according to the present embodiment may include a fixing unit that fixes the toner image on the recording medium, an image carrier cleaning unit that cleans the surface of the image carrier, and the like, as necessary.

  In this image forming apparatus, for example, the part including the developing unit may have a cartridge structure (process cartridge) that can be attached to and detached from the main body of the image forming apparatus. The process cartridge contains the developer for developing an electrostatic image according to the present embodiment, and develops the electrostatic latent image formed on the surface of the image carrier with the developer for developing an electrostatic image to form a toner image. A process cartridge that includes a developing unit for forming and is detachably attached to the image forming apparatus is preferably used. This facilitates handling of the developer for developing an electrostatic charge image and enhances adaptability to image forming apparatuses having various configurations.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto.

  FIG. 3 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus 301 includes a charging unit 310, an exposure unit 312, an electrophotographic photosensitive member 314 that is an image holding member, a developing unit 316, a transfer unit 318, a cleaning unit 320, and a fixing unit 322.

  In the image forming apparatus 301, around the electrophotographic photosensitive member 314, a charging unit 310 that is a charging unit that charges the surface of the electrophotographic photosensitive member 314 and the charged electrophotographic photosensitive member 314 are exposed according to image information. An exposure unit 312 that is an electrostatic latent image forming unit that forms an electrostatic latent image, a developing unit 316 that is a developing unit that develops the electrostatic latent image with a developer to form a toner image, and an electrophotographic photosensitive member. The transfer unit 318 that is a transfer unit that transfers the toner image formed on the surface of the recording medium 324 to the surface of the recording medium 324, and foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 after the transfer are removed to perform electrophotography. A cleaning unit 320 that is an image carrier cleaning means for cleaning the surface of the photoconductor 314 is arranged in this order. A fixing unit 322 that is a fixing unit that fixes the toner image transferred to the recording medium 324 is disposed on the side of the transfer unit 318.

  The operation of the image forming apparatus 301 according to this embodiment will be described. First, the surface of the electrophotographic photosensitive member 314 is charged by the charging unit 310 (charging process). Next, light is applied to the surface of the electrophotographic photosensitive member 314 by the exposure unit 312, the charged charge of the exposed portion is removed, and an electrostatic latent image is formed according to image information (electrostatic charge image). Forming step). Thereafter, the electrostatic latent image is developed by the developing unit 316, and a toner image is formed on the surface of the electrophotographic photosensitive member 314 (developing step). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 314 and using a laser beam as the exposure unit 312, the surface of the electrophotographic photoconductor 314 is negatively charged by the charging unit 310. Then, a digital latent image is formed in a dot shape by the laser beam light, and a toner is applied to a portion irradiated with the laser beam light by the developing unit 316 to be visualized. In this case, a negative bias is applied to the developing unit 316. Next, a recording medium 324 such as paper is superimposed on the toner image at the transfer unit 318, and a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324. 324 is transferred (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 322, and is fused and fixed to the recording medium 324 (fixing step). On the other hand, foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 without being transferred are removed by the cleaning unit 320 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 3, the toner image is directly transferred to the recording medium 324 such as paper by the transfer unit 318, but may be transferred via a transfer body such as an intermediate transfer body.

  Hereinafter, the charging unit, the image carrier, the electrostatic charge image forming unit (exposure unit), the developing unit, the transfer unit, the image carrier cleaning unit, and the fixing unit in the image forming apparatus 301 of FIG. 3 will be described.

(Charging means)
As the charging unit 310 serving as a charging unit, for example, a charger such as a corotron as shown in FIG. 3 is used, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 314 or may apply an alternating current superimposed thereon. For example, such a charging unit 310 charges the surface of the electrophotographic photosensitive member 314 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 314. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Image carrier)
The image carrier has a function of forming at least a latent image (electrostatic charge image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 314 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order, if necessary. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. It may be a single layer type photoreceptor included in the above layer, and is preferably a laminated type photoreceptor. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Static charge image forming means)
The exposure unit 312 which is an electrostatic charge image forming unit (exposure unit) is not particularly limited, and for example, a light source such as a semiconductor laser beam, LED (Light Emitting Diode) light, or liquid crystal shutter light is provided on the surface of the image carrier. Examples thereof include an optical device that exposes a desired image.

(Development means)
The developing unit 316 serving as a developing unit has a function of developing the electrostatic charge image formed on the image carrier with a developer containing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-described function, and may be selected according to the purpose. For example, an electrostatic image developing toner is electrophotographic using a brush, a roller, or the like. A known developing device having a function of adhering to the photoreceptor 314 may be used. The electrophotographic photosensitive member 314 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 318 as a transfer unit, for example, a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324 as illustrated in FIG. 3, and the toner image is transferred to the recording medium 324 by electrostatic force. A transfer roll and a transfer roll pressing device using a conductive roll or a semiconductive roll that transfers directly in contact with the recording medium 324 may be used. A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll may be arbitrarily set according to the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. As a transfer method, a method of directly transferring to a recording medium 324 such as paper or a method of transferring to a recording medium 324 via an intermediate transfer member may be used.

  A known intermediate transfer member may be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

(Image carrier cleaning means)
For the cleaning unit 320 that is an image carrier cleaning means, as long as it cleans foreign matter such as residual toner on the image carrier, a blade cleaning method, a brush cleaning method, a roll cleaning method, or the like is appropriately selected. do it.

(Fixing means)
The fixing unit 322 as a fixing unit (image fixing device) fixes a toner image transferred to the recording medium 324 by heating, pressing, or heating and pressing, and includes a fixing member.

(recoding media)
Examples of the recording medium 324 to which the toner image is transferred include plain paper, an OHP sheet, and the like used for electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, the surface of the recording medium is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are used. May be.

  Further, by combining with trickle development proposed in Japanese Patent Publication No. 2-21591, stable image formation can be achieved for a longer period.

  FIG. 4 is a schematic configuration diagram showing an example of a process cartridge containing the developer for developing an electrostatic charge image according to this embodiment. In the process cartridge 200, the photosensitive member 107, the charging roller 108, the photosensitive member cleaning device 113, the opening 118 for exposure, and the opening 117 for static elimination exposure are combined with the developing device 111 using the mounting rail 116. , And integrated. In FIG. 4, reference numeral 300 denotes a recording medium.

  The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device 112, a fixing device 115, and other components (not shown). It forms a forming apparatus.

  The process cartridge 200 shown in FIG. 4 includes a photosensitive member 107, a charging device 108, a developing device 111, a cleaning device 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. The devices may be selectively combined. In the process cartridge according to the present embodiment, in addition to the developing device 111, the photosensitive member 107, the charging device 108, the cleaning device (cleaning means) 113, the opening 118 for exposure, and the opening for static elimination exposure. You may provide at least 1 sort (s) selected from the group comprised from 117.

  Next, the toner cartridge will be described. The toner cartridge is detachably attached to the image forming apparatus, and contains at least toner to be supplied to a developing unit provided in the image forming apparatus. The toner cartridge only needs to contain at least toner, and may contain developer, for example, depending on the mechanism of the image forming apparatus.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Preparation of carrier 1)
_Fe 2 _O 3 1318 parts by weight carrier material, Mn _(OH) 2 586 parts by weight, Mg _(OH) 2 Prepare 96 parts by weight, and mixing them, 900 ° C., after calcination for 3 hours The mixture was mixed and pulverized in a wet ball mill for 10 hours, and granulated and dried by a spray dryer. Furthermore, main baking was performed at 1150 ° C. for 5 hours using a rotary kiln. Next, using a rotary kiln, additional baking was performed at 850 ° C. for 5 hours while rotating the sample at 10 rpm to obtain magnetic particles 1. This was Carrier 1. In the additional firing, the first 2 hours were fired in an air atmosphere, and the remaining 3 hours were fired at an oxygen concentration of 25%.

The peak intensity A of Fe ₂ O ₃ of the magnetic particles 1 measured using the X-ray diffraction method was 350. The measurement conditions of the X-ray diffraction method are as follows.
X-ray source: Cobalt Acceleration voltage: 40 kV
Current: 100 mA
Divergent slit: 1/2 °
Scattering speed: 1/2 °
Receiving slit: 0.15mm
Rotation speed: 5.000rpm
Measurement angle: 10 ° ≦ 2θ ≦ 90 °
Measurement interval: 0.01 °
Counting time: 2 seconds
X-ray diffractometer: RINT-TTR (Rigaku)

  Next, the magnetic particles 1 were pulverized. The pulverization process was performed as follows. 400 parts by mass of 1 mm zirconia beads and magnetic particles 1 were weighed and placed in a cylindrical container having a diameter of 20 cm and a height of 30 cm, and 600 parts by mass of water was further added. A circular rotating body having a diameter of 10 cm was submerged in a cylindrical container and rotated at a rotational speed of 120 rpm to start pulverization. After 6 hours from the start of the pulverization, sieving was performed with a 75 μm mesh. The sieved magnetic particles were dried and further selected with a magnet. This was designated as magnetic particles 1 after pulverization.

The peak intensity C of Fe ₂ O ₃ of the magnetic particles 1 after the pulverization treatment measured using the X-ray diffraction method was 50. The peak intensity A / peak intensity C was 7.0.

(Preparation of carrier 2)
Additional firing was performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing was performed at 800 ° C. for 1 hour in air at a temperature of 850 ° C. for 3 hours and 25% oxygen concentration. The magnetic particles 2 were obtained under the same conditions as the carrier 1 except that the conditions were changed to baking at an oxygen concentration of 25% at 800 ° C. for 1 hour. This was Carrier 2. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 2 measured using the X-ray diffraction method is 160, and the peak intensity C of the Fe ₂ O ₃ of the magnetic particles 2 measured using the X-ray diffraction method is 80. Moreover, the peak intensity A / peak intensity C was 2.0.

(Preparation of carrier 3)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 800 ° C. for 2 hours in an air atmosphere under conditions of firing at 850 ° C. for 3 hours and an oxygen concentration of 25%. The magnetic particles 3 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to baking at an oxygen concentration of 26% at 800 ° C. for 4 hours. This was Carrier 3. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 3 measured using the X-ray diffraction method is 500, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 3 after the pulverization treatment measured using the X-ray diffraction method is 25. The peak intensity A / peak intensity C was 18.0.

(Preparation of carrier 4)
As a carrier material, 1.8 parts by mass of SrCO ₃ was added, additional baking was performed at 850 ° C. for 2 hours in the air atmosphere, and then added at 850 ° C. for 3 hours at 25% oxygen concentration. The magnetic particles 4 were obtained under the same conditions as the carrier 1 except that the firing was performed at 820 ° C. for 2 hours in an air atmosphere and the conditions were changed to 820 ° C., 3 hours, and the oxygen concentration of 25%. It was. This was designated as carrier 4. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 4 measured using the X-ray diffraction method is 350, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 4 after pulverization measured using the X-ray diffraction method is 55. The peak intensity A / peak intensity C was 6.4.

(Preparation of carrier 5)
As a carrier material, 3.5 parts by mass of CaCO ₃ was added, and additional firing was performed at 850 ° C. for 2 hours in the air atmosphere, and then at 850 ° C. for 3 hours at 25% oxygen concentration. The magnetic particles 5 are obtained under the same conditions as those of the carrier 1 except that the firing is performed at 810 ° C. for 2 hours in an air atmosphere and the conditions are changed to 810 ° C., 3 hours, and the oxygen concentration of 25%. It was. This was designated as Carrier 5. The peak intensity A of Fe ₂ O ₃ of the magnetic particle 5 measured using the X-ray diffraction method is 340, and the peak intensity C of Fe ₂ O ₃ of the magnetic particle 5 after the grinding treatment measured using the X-ray diffraction method is 50. The peak intensity A / peak intensity C was 6.8.

(Preparation of carrier 6)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 850 ° C. for 1.5 hours in an air atmosphere under conditions of firing at 850 ° C. for 3 hours at an oxygen concentration of 25%. Then, the magnetic particles 6 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to 820 ° C., 3 hours, and the condition of firing at an oxygen concentration of 26%. This was designated as Carrier 6. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 6 measured using the X-ray diffraction method is 460, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 6 after the pulverization treatment measured using the X-ray diffraction method is 23. Moreover, the peak intensity A / peak intensity C was 20.0.

(Preparation of carrier 7)
Conditions for additional firing at 850 ° C. for 2 hours in the air atmosphere, then firing at 850 ° C. for 3 hours at an oxygen concentration of 25%, additional firing at 870 ° C. for 3 hours in the air atmosphere The magnetic particles 7 were obtained under the same conditions as in the carrier 1 except that the magnetic particles 7 were changed. This was designated as Carrier 7. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 7 measured using the X-ray diffraction method is 250, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 7 measured using the X-ray diffraction method is 200. Moreover, the peak intensity A / peak intensity C was 1.3.

(Preparation of carrier 8)
Additional firing was performed at 850 ° C. for 2 hours in an air atmosphere, and then firing was performed at 850 ° C. for 3 hours at an oxygen concentration of 25%. The magnetic particles 8 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to 820 ° C., 4 hours, and the condition of firing at an oxygen concentration of 26%. This was designated as Carrier 8. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 8 measured using the X-ray diffraction method is 440, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 8 after the pulverization treatment measured using the X-ray diffraction method is It was 20. The peak intensity A / peak intensity C was 22.0.

(Preparation of carrier 9)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, then firing at 850 ° C. for 3 hours at an oxygen concentration of 25%. Additional firing is performed at 820 ° C. for 5 hours at an oxygen concentration of 27%. The magnetic particles 9 were obtained under the same conditions as the carrier 1 except that the conditions were changed. This was Carrier 9. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 9 measured using the X-ray diffraction method is 550, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 9 measured using the X-ray diffraction method is 10. Moreover, the peak intensity A / peak intensity C was 55.0.

(Preparation of carrier 10)
Additional firing was performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing was performed at 800 ° C. for 1 hour in air at a temperature of 850 ° C. for 3 hours and 25% oxygen concentration. Subsequently, the magnetic particles 10 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to baking at an oxygen concentration of 25% at 800 ° C. for 1 hour. This was designated as Carrier 10. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 10 measured using the X-ray diffraction method is 60, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 10 after the pulverization treatment measured using the X-ray diffraction method is 10. The peak intensity A / peak intensity C was 6.0.

(Preparation of carrier 11)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 780 ° C. for 2.5 hours in an air atmosphere under conditions of firing at 850 ° C. for 3 hours and an oxygen concentration of 25%. Then, the magnetic particles 11 were obtained under the same conditions as the carrier 1 except that the conditions were changed to 780 ° C. for 1 hour and an oxygen concentration of 27%. This was designated as Carrier 11. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 11 measured using the X-ray diffraction method is 510, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 11 after the grinding treatment measured using the X-ray diffraction method is 30. The peak intensity A / peak intensity C was 17.

(Preparation of carrier 12)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 850 ° C. for 1 hour in an air atmosphere under the conditions of firing at 850 ° C. for 3 hours at an oxygen concentration of 25%. The magnetic particles 12 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to a condition of baking at an oxygen concentration of 23% at 800 ° C. for 4 hours. This was designated as Carrier 12. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 12 measured using the X-ray diffraction method is 100, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 12 after the pulverization treatment measured using the X-ray diffraction method is 50. The peak intensity A / peak intensity C was 2.

(Preparation of carrier 13)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 850 ° C. for 1.5 hours in an air atmosphere under conditions of firing at 850 ° C. for 3 hours at an oxygen concentration of 25%. Then, the magnetic particles 13 were obtained under the same conditions as those of the carrier 1 except that the firing conditions were changed to 850 ° C., 1.5 hours, and an oxygen concentration of 25%. This was designated as Carrier 13. The peak intensity A of Fe ₂ O ₃ of the magnetic particle 13 measured using the X-ray diffraction method is 250, and the peak intensity C of Fe ₂ O ₃ of the magnetic particle 13 after the pulverization treatment measured using the X-ray diffraction method is 90. The peak intensity A / peak intensity C was 2.8.

(Preparation of carrier 14)
Additional firing was performed at 850 ° C. for 2 hours in an air atmosphere, and then firing was performed at 850 ° C. for 3 hours at an oxygen concentration of 25%. The magnetic particles 14 were obtained under the same conditions as the carrier 1 except that the conditions were changed to 820 ° C., 5 hours, and the condition of baking at an oxygen concentration of 27%. This was designated as carrier 14. The peak intensity A of Fe ₂ O ₃ of the magnetic particles 14 measured using the X-ray diffraction method is 540, and the peak intensity C of Fe ₂ O ₃ of the magnetic particles 14 measured using the X-ray diffraction method is 25. The peak intensity A / peak intensity C was 21.6.

(Preparation of carrier 15)
Additional firing is performed at 850 ° C. for 2 hours in an air atmosphere, and then additional firing is performed at 870 ° C. for 2.5 hours in an air atmosphere under conditions of firing at 850 ° C. for 3 hours and an oxygen concentration of 25%. Then, the magnetic particles 15 were obtained under the same conditions as those of the carrier 1 except that the conditions were changed to 820 ° C., 1 hour, and an oxygen concentration of 26%. This was Carrier 15. The peak intensity A of Fe ₂ O ₃ of the magnetic particle 15 measured using the X-ray diffraction method is 150, and the peak intensity C of Fe ₂ O ₃ of the magnetic particle 15 after the pulverization treatment measured using the X-ray diffraction method is 80. The peak intensity A / peak intensity C was 1.9.

Table 1 peak intensity A of _Fe 2 _{O 3} magnetic particles 15, the peak intensity of _Fe 2 _{O 3} magnetic particles 15 after the pulverization treatment C, peak intensity A / peak intensity C of the magnetic particles 15 Summarized. Table 2 summarizes the carrier material composition, additional firing temperature, oxygen concentration, and time of magnetic particles 1-15.

(Preparation of colorant dispersion)
Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Co., Ltd.) 50 parts by mass Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass Ion-exchanged water 200 parts by mass

  The above components were mixed and dispersed for 5 minutes with an Ultra Turrax manufactured by IKA and for 10 minutes with an ultrasonic bath to obtain a colorant dispersion having a solid content of 21%. It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of release agent dispersion)
Paraffin wax: HNP-9 (Nippon Seiki Co., Ltd.) 19 parts by weight Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.) 1 part by weight Ion-exchanged water 80 parts by weight

  The above components were mixed in a heat-resistant container, heated to 90 ° C., and stirred for 30 minutes. Next, the molten liquid is circulated from the bottom of the container to the gorin homogenizer, and under a pressure condition of 5 MPa, a circulation operation corresponding to 3 passes is performed. Then, the pressure is increased to 35 MPa, and further a circulation operation corresponding to 3 passes is performed. It was. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent dispersion. It was 240 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of resin particle dispersion)
(Oil layer)
Styrene (manufactured by Wako Pure Chemical Industries, Ltd.) 30 parts by mass n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 10 parts by mass β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.) 1.3 parts by mass Dodecanethiol (Wako Pure Chemical Industries, Ltd.) Made) 0.4 parts by mass (water layer 1)
17 parts by mass of ion-exchanged water Anionic surfactant (Dowfax, manufactured by Dow Chemical Company) 0.4 parts by mass (water layer 2)
Deionized water 40 parts by weight Anionic surfactant (Dowfax, manufactured by Dow Chemical Co.) 0.05 part by weight Ammonium peroxodisulfate (Wako Pure Chemical Industries, Ltd.) 0.4 part by weight

  The above oil layer component and water layer 1 component were placed in a flask and mixed with stirring to obtain a monomer emulsified dispersion. The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was sufficiently replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The above monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours. The obtained resin particles were 250 nm when the volume average particle diameter D50v of the resin fine particles was measured with a laser diffraction particle size distribution analyzer LA-700 (manufactured by Horiba Seisakusho), and a differential scanning calorimeter (DSC-50 Shimadzu Corporation). The glass transition temperature of the resin was measured at a rate of temperature increase of 10 ° C./min. Using a molecular weight measuring device (HLC-8020 manufactured by Tosoh Corporation), and the number average molecular weight (polystyrene) was measured using THF as a solvent. Measurement) was 13,000. That is, a resin particle dispersion having a volume average particle size of 250 nm, a solid content of 42%, a glass transition temperature of 52 ° C., and a number average molecular weight Mn of 13,000 was obtained.

(Toner preparation)
Resin fine particle dispersion 150 parts by weight Colorant particle dispersion 30 parts by weight Release agent particle dispersion 40 parts by weight Polyaluminum chloride 0.4 part by weight

The above components were mixed and dispersed in a stainless steel flask using an IKE Ultra Turrax, and then heated to 48 ° C. while stirring the flask in a heating oil bath. After maintaining at 48 ° C. for 80 minutes, 70 parts by mass of the same resin fine particle dispersion as above was gradually added thereto. Then, after adjusting the pH in the system to 6.0 using a sodium hydroxide aqueous solution having a concentration of 0.5 mol / L, the stainless steel flask was sealed, and the stirring shaft seal was magnetically sealed while stirring was continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, filtered and thoroughly washed with ion-exchanged water, and then solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed with 3 L of ion exchanged water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 5 times. When the pH of the filtrate was 6.54 and the electric conductivity was 6.5 μS / cm, No. 2 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner mother particles. The volume average particle diameter D50v of the toner mother particles was measured with a Coulter counter. As a result, it was 6.2 μm and the volume average particle size distribution index GSDv was 1.20. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135, and it was observed that the particles had a potato shape. Further, the glass transition temperature of the toner was 52 ° C. Further, this toner was treated with silica (SiO ₂ ) particles having an average primary particle diameter of 40 nm and surface-hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyltrimethoxy. Metatitanic acid compound fine particles having an average primary particle diameter of 20 nm, which is a reaction product of silane, were added so that the coverage of the surface of the toner particles was 40%, and mixed with a Henschel mixer to prepare a toner.

<Example 1>
The developer was obtained by mixing the carrier 1 and the toner so that the toner concentration was 8% by weight.

(Developer evaluation)
The developer was charged into the Cyan position of a DCC400 remodeling machine (toner concentration fixed at 8%, print speed 60 sheets / min). In advance, 30000 halftone 30% A4 full face prints were made. Next, it was left in an environment of 10 ° C. and 15% RH for 1 day. After standing for 1 day, a starvation chart was prepared by alternately printing a low density image (5 cm × 5 cm) and a high density image (5 cm × 5 cm) alternately. The low density image has an area coverage of 20%, and the high density image has an area coverage of 100%. Evaluation of image omission at the rear end of the image (between the low density image and the high density image) in the starvation chart was performed according to the following criteria. Next, it was left for 1 day in an environment of 30 ° C. and 85% RH. After leaving for one day, 10 sheets of half-tone 50% A4 full surface printing were performed, and white spots in the 10th image were evaluated according to the following criteria. The obtained results are shown in Table 3.

(Image missing at the rear edge of the image)
◎: When image missing at the rear end of the image is not visually confirmed ○: Image missing at the rear end of the image is not visually confirmed, but slightly thin Δ: Image missing at the rear end of the image is slightly confirmed visually ×: When image omission at the rear end of the image is clearly confirmed visually

(Images are white)
◎◎: Image (20 cm ²⁾ when a white point was confirmed one or less visually ◎: image If white spots was confirmed one than 3 or less visually in (20cm ²⁾ ○: Image (20 cm ² ) If white spots were observed more than 3 more than nine visually △: image (if the white point 20 cm ²⁾ was confirmed nine than 19 or less visually ×: white spots in the image (20 cm ²⁾ When more than 19 items are visually confirmed

<Example 2>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 2. The obtained results are shown in Table 3.

<Example 3>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 3. The obtained results are shown in Table 3.

<Example 4>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 4. The obtained results are shown in Table 3.

<Example 5>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 5. The obtained results are shown in Table 3.

<Example 6>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 6. The obtained results are shown in Table 3.

<Comparative Example 1>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 7. The obtained results are shown in Table 3.

<Comparative example 2>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 8. The obtained results are shown in Table 3.

<Comparative Example 3>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 9. The obtained results are shown in Table 3.

<Comparative example 4>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 10. The obtained results are shown in Table 3.

<Comparative Example 5>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 11. The obtained results are shown in Table 3.

<Comparative Example 6>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 12. The obtained results are shown in Table 3.

<Comparative Example 7>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 13. The obtained results are shown in Table 3.

<Comparative Example 8>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 14. The obtained results are shown in Table 3.

<Comparative Example 9>
A developer was prepared and evaluated in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 15. The obtained results are shown in Table 3.

As the results of Examples 1 to 6 show, the Fe ₂ O ₃ peak intensity A of the magnetic particles obtained by the X-ray diffraction method is in the range of 150 to 500, and the particles after the magnetic particles are pulverized are processed. Magnetic particles (carriers) having a peak intensity C of ₂ O ₃ in the range of 25 to 80 and a peak intensity ratio of the peak intensity A to the peak intensity C (peak intensity A / peak intensity C) in the range of 2 to 20 Compared to Comparative Examples 1 to 9 using magnetic particles (carriers) that do not satisfy at least one of peak intensity A and C and peak intensity C / peak intensity A Occurrence of image omission at the end and white omission of the image was suppressed. Examples 4, 5, 9, and 10 using magnetic particles (carriers) containing strontium and calcium are Examples 1 to 3 and 6 using magnetic particles (carriers) not containing strontium and calcium. In comparison, the occurrence of white spots in the image was further suppressed.

  20 electrophotographic photosensitive member, 50 developing device, 51 case, 52 developing roll, 53 supply roll, 54 stirring roll, 107 photoconductor, 108 charging roller (charging device), 111 developing device, 112 transfer device, 113 photoconductor cleaning device , 115 fixing device, 116 mounting rail, 117 opening, 118 opening, 200 process cartridge, 300 recording medium, 301 image forming apparatus, 310 charging unit, 312 exposure unit, 314 electrophotographic photosensitive member, 316 developing unit, 318 transfer Part, 320 cleaning part, 322 fixing part, 324 recording medium, 511 layer thickness regulating member, 512 cover part, 521 magnet roll, 522 developing sleeve.

Claims (5)

Having magnetic particles containing a ferrite component represented by a general formula M _x Fe _3-x O ₄ (where 0 ≦ x ≦ 1, M represents a metal element),
When the peak intensity of Fe ₂ O ₃ of the magnetic particles obtained by X-ray diffraction method is A, the peak intensity of Fe ₂ O ₃ particles after pulverization of the magnetic particles is C, the peak intensity A Is in the range of 150 to 500, the peak intensity C is in the range of 25 to 80, and the peak intensity ratio (A / C) of the peak intensity A to the peak intensity C is in the range of 2 to 20 A carrier for developing an electrostatic image, which is characterized by the following.   2. The electrostatic image developing carrier according to claim 1, wherein the metal element M contains at least one metal selected from strontium (Sr) and calcium (Ca).   An electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to claim 1.   A developing means for accommodating the developer for developing an electrostatic charge image according to claim 3 and developing a latent image formed on the surface of the image carrier with the developer for developing an electrostatic charge image to form a toner image. A process cartridge comprising:   The image holding member, a charging unit that charges the surface of the image holding member, an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the image holding member, and the electrostatic latent image according to claim 3. An image forming apparatus comprising: a developing unit that develops a toner image by developing with a developer for developing an electrostatic image; and a transfer unit that transfers the toner image to a transfer target.

Images