JP2014153476A - 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 a difference in image density occurring on images on a recording medium, even when images are formed at high speed in a high-temperature and high-humidity environment.SOLUTION: A carrier for electrostatic charge image development includes magnetic particles, and has the following properties: an average interval Sm between protrusions and recesses on the surface of the magnetic particles within a range of 1.0 or more and 3.5 or less; an arithmetic average roughness Ra of the surface of the magnetic particles within a range of 0.2 or more and 0.7 or less; a BET specific surface area of the magnetic particles within a range of 0.08 m/g or more and 0.14 m/g or less; and a volume resistance of the magnetic particles in an electric field of 24000 V/cm within a range of 6.0 logΩcm or more and 8.0 logΩcm 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 includes magnetic particles, and the value of (BET specific surface area of magnetic particles) / (true sphere equivalent specific surface area when the magnetic particles are assumed to be true spheres) is 8.0 to 30. A carrier having a magnetic particle surface arithmetic mean roughness Ra of 0.050 μm or less and an apparent density of 2.40 g / cc or more is disclosed.

For example, Patent Document 2 discloses a carrier formed of magnetic particles and a coating layer that covers the magnetic particles, the carrier has an average particle size of 100 μm or less, and the carrier has a volume resistance of 10 ¹⁰ Ω · cm. The above carrier is disclosed.

  For example, Patent Document 3 discloses a carrier having a carrier core containing magnetic particles and a coating layer formed on the surface of the carrier core, and the carrier has a 10-point deviation of 0 in volume resistance at 5000 V / cm. The number-based circle equivalent diameter 50% value in the range of the circle equivalent diameter of the carrier of 0.5 μm or more and 200.0 μm or less is 15 μm or more and 70 μm, and the circle equivalent diameter of 0.5 μm or more and 200. The average circularity at a circularity of 0.200 or more and 1.000 or less within a range of 0 μm or less is 0.960 or more, and the circularity at a circle equivalent diameter of 15.0 μm or more and 100.0 μm or less is 0.200 or more. A carrier having a ratio of particles of 0.925 or less of 15.0% by number or less is disclosed.

  For example, Patent Document 4 discloses a carrier having at least porous magnetic particles and a resin, and a differential pore having a pore diameter in the range of 0.10 μm to 3.00 μm in the mercury intrusion method of the porous magnetic particles. The maximum pore diameter in which the volume is maximum is 0.80 μm or more and 1.50 μm or less, the maximum value of the differential pore volume in the range of 0.80 μm or more and 1.50 μm or less is P1, and the pore diameter is 2.00 μm or more and 3 P1 is 0.05 ml / g or more and 0.50 ml / g or less, and P2 / P1 is 0.05 or more and 0.30 or less when the maximum value of the differential pore volume in the range of 0.000 μm or less is P2. A carrier characterized in that is disclosed.

JP 2009-86340 A JP-A-7-234548 JP 2008-191463 A JP 2010-61120 A

  An object of the present invention is to provide an electrostatic charge image developing carrier and an electrostatic charge image developing development capable of suppressing an image density difference generated in an image on a recording medium even when an image is formed at high speed in a high temperature and high humidity environment. The present invention provides an agent, a process cartridge, and an image forming apparatus.

The invention according to claim 1 includes magnetic particles, wherein the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0. in the range of .2 to 0.7, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of said magnetic particles, 24000V / cm The electrostatic charge image developing carrier has a range of 6.0 log Ωcm or more and 8.0 log Ωcm or less under the electric field.

In the invention according to claim 2, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 2.5 to 3.0, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.4 to 0.7. in the range of less, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.12 m ² / g, a volume resistivity of said magnetic particles, under an electric field of 24000V / cm, 7 The carrier for developing an electrostatic charge image according to claim 1, wherein the carrier is in a range of 0.0 log Ωcm to 7.8 log Ωcm.

  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 present invention, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.2 to 0.00. 7 is a range of the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of said magnetic particles, under an electric field of 24000V / cm, Image density generated in an image on a recording medium even when an image is formed at high speed in a high-temperature and high-humidity environment as compared with a case where the condition of 6.0 logΩcm or more and 8.0 logΩcm or less is not satisfied. Provided is a carrier for developing an electrostatic image in which the difference is suppressed.

According to the invention of claim 2, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 2.5 to 3.0, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.4 to 0.7. in the range of below the range BET specific surface area is less than 0.08 m ² / g or more 0.12 m ² / g of magnetic particles, the volume resistivity of the magnetic particles, under an electric field of 24000V / cm, 7.0logΩcm Compared with the case where the above condition of 7.8 log Ωcm or less is not satisfied, even when an image is formed at high speed in a high temperature and high humidity environment, the difference in image density generated in the image on the recording medium is greater. A suppressed electrostatic charge image developing carrier is provided.

According to the invention of claim 3, the average interval Sm of the irregularities on the magnetic particle surface of the carrier is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the magnetic particle surface is 0.2 or more. in the range of 0.7 or less, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of the magnetic particles, an electric field of 24000V / cm Even when an image is formed at a high speed in a high temperature and high humidity environment as compared with the case where the condition of 6.0 log Ωcm or more and 8.0 log Ωcm or less is not satisfied, the image on the recording medium is generated. Provided is a developer for developing an electrostatic image in which a difference in image density is suppressed.

According to the invention of claim 4, the average interval Sm of the irregularities on the surface of the magnetic particles of the carrier is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.2 or more. in the range of 0.7 or less, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of the magnetic particles, an electric field of 24000V / cm Even when an image is formed at a high speed in a high temperature and high humidity environment as compared with the case where the condition of 6.0 log Ωcm or more and 8.0 log Ωcm or less is not satisfied, the image on the recording medium is generated. A process cartridge is provided in which a difference in image density is suppressed.

According to the invention of claim 5, the average interval Sm of the irregularities on the magnetic particle surface of the carrier is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the magnetic particle surface is 0.2 or more. in the range of 0.7 or less, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of the magnetic particles, an electric field of 24000V / cm Even when an image is formed at a high speed in a high temperature and high humidity environment as compared with the case where the condition of 6.0 log Ωcm or more and 8.0 log Ωcm or less is not satisfied, the image on the recording medium is generated. An image forming apparatus in which a difference in image density is suppressed is provided.

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 the electrostatic image developing carrier, and the hatched circles represent the electrostatic image developing toner. 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).

  A recording medium on which an image is formed is output from the image forming apparatus through a transfer process, a fixing process, and the like, which will be described later. In general, when an image is formed on a recording medium at a high speed, it is necessary to rotate the developing roll 52 or the like at a high speed. However, the higher the image formation speed, that is, the higher the developing roll 52 is at a higher speed. As the rotation increases, variations may occur in the height of the magnetic brush that is formed on the developing roll 52, the density of the magnetic brush, and the like. Here, forming an image at high speed means outputting plain paper at 40 sheets / minute or more.

  In addition, when an image is formed on a recording medium in a high temperature (for example, 28 ° C. to 32 ° C.) and high humidity (for example, 80% RH or more) environment, the lower the carrier resistance, the more charged the toner is In some cases, there is a tendency for variations to occur in the height of the head of the magnetic brush formed on the developing roll 52, the density of the magnetic brush, and the like. The magnetic brush head height is the height of the magnetic brush in the supply path T1 shown in FIG. The height of the magnetic brush head is obtained by observing with a microscope or the like and measuring the average height. The density of the magnetic brush is the density of the magnetic brush in the supply path T1 shown in FIG. is there. The density of the magnetic brush is determined by the laser transmittance or the like, and there are methods of relative comparison from visual observation with a magnifying glass and photographic images.

  When variations occur in the height of the magnetic brush head, the density of the magnetic brush, and the like, it is considered that a difference occurs in the developing efficiency at the tip of the magnetic brush and an image density difference occurs in the image on the recording medium. Therefore, when an image is formed at a high speed in a high temperature and high humidity environment, an image density difference tends to occur in the image on the recording medium. By using the electrostatic charge image developing carrier according to the present embodiment, the present inventors can produce an image density difference in an image on a recording medium even when an image is formed at a high speed in a high temperature and high humidity environment. It was found to be suppressed. Hereinafter, the electrostatic image developing carrier according to the present embodiment will be described.

<Carrier for developing electrostatic image>
The carrier for developing an electrostatic charge image according to this embodiment has magnetic particles, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 1.0 to 3.5, and the arithmetic average of the surface of the magnetic particles ranges roughness Ra of 0.2 to 0.7, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of said magnetic particles Is in the range of 6.0 log Ωcm or more and 8.0 log Ωcm or less under an electric field of 24000 V / cm. A method for measuring the average spacing Sm of the irregularities on the surface of the magnetic particles, the arithmetic average roughness Ra of the surface of the magnetic particles, the BET specific surface area of the magnetic particles, and the volume resistance of the magnetic particles will be described later (see Examples).

The average interval Sm of the irregularities on the magnetic particle surface is in the range of 1.0 to 3.5, the arithmetic average roughness Ra of the magnetic particle surface is in the range of 0.2 to 0.7, and the BET specific surface area of the magnetic particles with 0.08 m 2 / ^g or more 0.14 m 2 / ^g or less of range, as compared with the case that does not satisfy the above these ranges, even when forming an image at a high speed, a developing device shown in FIG. 1 The fluidity of the developer containing the carrier is stabilized inside the 50 case 51, the magnetic brush is difficult to slide on the developing roll 52, and variations such as the height of the magnetic brush head and the density of the magnetic brush can be suppressed. it is conceivable that. Further, by setting the volume resistance of the magnetic particles in the range of 6.0 log Ωcm to 8.0 log Ωcm under an electric field of 24000 V / cm, the toner can be used in a high temperature and high humidity environment as compared with the case where the above range is not satisfied. It is considered that the charged electric charge is less likely to leak through the carrier, and variations in the height of the magnetic brush formed on the developing roll 52 and the density of the magnetic brush are suppressed. Therefore, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 1.0 to 3.5, the arithmetic average roughness Ra of the surface of the magnetic particles is in the range of 0.2 to 0.7, and the BET of the magnetic particles the specific surface area and 0.08 m ² / g or more 0.14 m ² / g or less in the range, the volume resistivity of the magnetic particles in an electric field of 24000V / cm, by a 8.0logΩcm following range of 6.0Logomegacm, Compared to the case where the above range is not satisfied, even when an image is formed at high speed in a high-temperature and high-humidity environment, variations such as the height of the magnetic brush head and the density of the magnetic brush are suppressed, and the image on the recording medium is reduced. The resulting image density difference is suppressed. In the present embodiment, even in a carrier having magnetic particles and a coating layer formed on the surface of the magnetic particles, the average interval Sm of the irregularities on the surface of the magnetic particles, the arithmetic average roughness Ra of the surface of the magnetic particles, the BET of the magnetic particles If the specific surface area and the volume resistivity of the magnetic particles satisfy the above range, an image generated on the image on the recording medium even when an image is formed at a high speed in a high temperature and high humidity environment as compared with the case where the above range is not satisfied. Density difference is suppressed.

When the average interval Sm between the irregularities on the surface of the magnetic particles is less than 1.0, the magnetic brush is more easily slid on the developing roll 52 as compared with the case where Sm is 1.0 or more. There may be variations in the density and the like of the magnetic brush. Further, when the average interval Sm of the irregularities on the surface of the magnetic particles exceeds 3.5, the irregularities on the surface of the magnetic particles become too large compared to the case where Sm is 3.5 or less, and the magnetic brush is on the developing roll 52. It may become slippery and may cause variations in the height of the magnetic brush head, the density of the magnetic brush, and the like. Further, when the arithmetic average roughness Ra on the surface of the magnetic particles is less than 0.2, the trapping between the magnetic particles becomes smaller compared to the case where Ra is 0.2 or more, and the height of the magnetic brush spikes and the magnetic Variations may occur in brush density and the like. Further, when the arithmetic average roughness Ra of the magnetic particle surface exceeds 0.7, the magnetic brush is fixed to the developing roll 52 and becomes difficult to move as compared with the case where Ra is 0.7 or less. However, it may become slippery on the developing roll 52, and variations may occur in the height of the magnetic brush head, the density of the magnetic brush, and the like. Further, when the volume resistance of the magnetic particles is less than 6.0 log Ωcm under an electric field of 24000 V / cm, the toner has a volume resistance of 6.0 log Ωcm or more under an electric field of 24000 V / cm. In some cases, the charged electric charge easily leaks through the carrier, causing variations in the height of the magnetic brush head, the density of the magnetic brush, and the like. In addition, when the volume resistance of the magnetic particles exceeds 8.0 log Ωcm under an electric field of 24000 V / cm, the toner has a higher volume resistance than that of 8.0 log Ωcm under an electric field of 24000 V / cm. Charges opposite to the charged charges are likely to be accumulated in the carriers, and variations may occur in the height of the magnetic brush heads, the density of the magnetic brushes, and the like. Further, if the BET specific surface area of the magnetic particles is more than a case or 0.14 m ² / g of less than 0.08 m ² / g, BET specific surface area is less than 0.08 m ² / g or more 0.14 m ² / g and In comparison, the electric charge charged in the toner easily leaks through the carrier in the range of 6.0 log Ωcm or more and 8.0 log Ωcm or less under the electric field where the volume resistance of the magnetic particles is 24000 V / cm, and the height of the magnetic brush head and the magnetic Variations may occur in brush density and the like. Therefore, at least any one of the average interval Sm of the irregularities on the magnetic particle surface, the arithmetic average roughness Ra of the magnetic particle surface, the BET specific surface area of the magnetic particle, and the volume resistance of the magnetic particle satisfy the above ranges. Compared to the case where it is not satisfied, even when an image is formed at high speed in a high-temperature and high-humidity environment, variations such as the height of the magnetic brush ears and the density of the magnetic brush are suppressed, and this occurs in the image on the recording medium. The image density difference is suppressed.

  As a volume average particle diameter of the magnetic particles of the present embodiment, for example, a range of 30 μm or more and 50 μm or less is preferable. If the volume average particle size of the magnetic particles is less than 30 μm, carrier scattering may be difficult to suppress, and if it exceeds 50 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 It is preferable that it is a manufacturing method containing.

  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 pulverized product (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 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 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. Moreover, it is preferable to perform the crushing process and the classification process of the magnetic particles obtained by the main baking process after the main baking process. In the crushing step, a known device is used, and examples thereof include a pin mill and a hammer mill. In the classification process, a known device is used, and examples thereof include a vibration sieve and an airflow classifier.

In the present embodiment, a surface property adjusting agent such as silica (SiO ₂ ) is added to the carrier material, the volume average particle diameter of the pulverized product (carrier material) in the pulverization step after temporary calcination, etc. is controlled. By adjusting the firing temperature and oxygen concentration in the process, etc., the average interval Sm of the irregularities on the surface of the magnetic particles is set in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.2. above 0.7 and the range, the BET specific surface area of the magnetic particles and 0.08 m ² / g or more 0.14 m ² / g or less in the range, the volume resistivity of the magnetic particles in the electric field of 24000V / cm, 6. It is preferable to adjust in the range of 0 log Ωcm or more and 8.0 log Ωcm or less.

  First, the area (size) of the grain boundary of the magnetic particles finally obtained is adjusted by adding a surface property adjusting agent such as silica to the carrier material for performing the pre-baking step. Specifically, as the amount of the surface property adjusting agent such as silica increases, the area of the grain boundary of the magnetic particles increases, and the average interval Sm of the irregularities on the surface of the magnetic particles tends to increase. The larger the volume average particle size of the pulverized product in the pulverization step after the pre-baking step, the larger the area of the grain boundary of the magnetic particles, and the average interval Sm between the irregularities on the surface of the magnetic particles is likely to increase. Moreover, the area (size) of the grain boundary of the finally obtained magnetic particles is adjusted by adjusting the firing temperature and oxygen concentration in the main firing step. Specifically, when the firing temperature in the main firing step is increased, the area of the grain boundary of the magnetic particles is increased, and the average interval Sm of the irregularities on the surface of the magnetic particles is likely to be increased. In addition, when the oxygen concentration in the main firing step is increased, the growth of grain boundaries is slowed and gaps between grain boundaries are likely to remain, and the arithmetic average roughness Ra on the surface of the magnetic grains is likely to increase. Moreover, the higher the firing temperature in the main firing step and the lower the oxygen concentration, the lower the volume resistance mainly (the magnetization of the magnetic particles becomes higher). Further, after obtaining the magnetic particles in the main firing, by performing additional firing in which the magnetic particles are flowed in the air atmosphere, the gap between the grain boundaries is smaller than in the case where the additional firing is not performed. The BET specific surface area of the magnetic particles is likely to be small while suppressing the change in Sm and Ra. For example, in order to make the average interval Sm of the irregularities on the magnetic particle surface, the arithmetic average roughness Ra of the magnetic particle surface, the BET specific surface area of the magnetic particle, and the volume resistance of the magnetic particle within the above ranges, The addition amount is preferably in the range of 0.01% by mass to 0.5% by mass with respect to the total amount of the carrier material, and the firing temperature in the main firing step is, for example, 900 ° C. or more and 1500 ° C. or less. The oxygen concentration in the main baking step is preferably in the range of 0.5% to 8%, for example. Furthermore, after the main firing step, for example, it is more preferable to perform additional firing in which the magnetic particles are fired at 700 ° C. or higher and 1000 ° C. or lower in the atmosphere while flowing the magnetic particles.

  In addition, the method for producing an electrostatic charge image developing carrier of this embodiment may include a coating layer forming step of coating the surface of magnetic particles obtained through the main baking step and the like with a resin or the like. 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, and further mixed and stirred to attach the external additive or the like on 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 a stable volume resistance of the carrier over time.

The volume resistance 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. Is preferably 10 ⁸ Ω · cm or more and 10 ¹³ Ω · cm or less. When the volume resistance 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 resistance 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 vinyl such as styrene and acrylic acid Using system 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)
(Preparation of coating layer forming solution)
Cyclohexyl acrylate resin (weight average molecular weight 50,000) 36 parts by mass Carbon black VXC72 (manufactured by Cabot) 4 parts by mass Toluene 250 parts by mass Isopropyl alcohol 50 parts by mass The above components and glass beads (particle size: 1 mm, equivalent to toluene) Was put in a sand mill manufactured by Kansai Paint Co., Ltd. and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a coating layer forming solution having a solid content of 11%.

(Preparation of magnetic material 1)
As a carrier material, 1318 parts by mass of Fe ₂ O ₃ , 586 parts by mass of Mn (OH) ₂ , 96 parts by mass of Mg (OH) ₂ were prepared, and they were mixed, and a dispersant (sodium polycarboxylate) was added to the mixture. Water and zirconia beads having a diameter of 1 mm were added, and the mixture was pulverized and mixed in a sand mill for 1 hour. Next, the zirconia beads were filtered, and the dried carrier material was calcined using a rotary kiln at 20 rpm, 900 ° C. for 2 hours in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 5%. After calcination, a dispersant (sodium polycarboxylate), water, and 6.6 parts by mass of polyvinyl alcohol were added to the carrier material (oxide), and the mixture was pulverized and mixed with a wet ball mill for 5 hours. The obtained pulverized product had a volume average particle size of 1.4 μm. Next, the pulverized product was granulated and dried with a spray dryer so that the volume average particle size became 40 μm. Furthermore, the main calcination was carried out using an electric furnace at 1100 ° C. for 5 hours in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1%. And the magnetic particle 1 was obtained through the crushing process and the classification process. The volume average particle size of the magnetic particles 1 is 35 μm, the average interval Sm of the irregularities on the surface of the magnetic particles 1 (hereinafter sometimes referred to as Sm of the magnetic particles 1) is 2.5, and the calculation of the surface of the magnetic particles 1 The average roughness Ra (hereinafter sometimes referred to as Ra of the magnetic particles 1) is 0.4, the BET specific surface area of the magnetic particles 1 is 0.12 m ² / g, and the volume resistance of the magnetic particles 1 is 24000V. It was 7 log Ωcm under an electric field of / cm. These measurement methods are as follows.

<Measurement of Sm and Ra of Magnetic Particle 1>
The measuring method of Sm and Ra of the magnetic particle 1 is a method of obtaining 50 magnetic particles 1 by converting the surface at a magnification of 3000 times using an ultra-deep color 3D shape measuring microscope (VK-9500, manufactured by Keyence Corporation). Yes, according to JIS B0601 (1994 edition). Specifically, the Sm of the magnetic particle 1 is obtained by calculating a roughness curve from the three-dimensional shape of the surface of the magnetic particle 1 observed with the microscope, and having one cycle of the Yamatani cycle obtained from the intersection where the roughness curve intersects the average line. The average value of the interval is obtained. The reference length for determining Sm of the magnetic particles 1 is 10 μm, and the cutoff value is 0.08 mm. Ra of the magnetic particle 1 is obtained by obtaining a roughness curve from the three-dimensional shape of the surface of the magnetic particle 1 observed with the microscope, and sums and averages the measured value of the roughness curve and the absolute value of the deviation to the average value. Is required. The reference length for determining Ra of the magnetic particle 1 is 10 μm, and the cutoff value is 0.08 mm.

<Measurement of Volume Average Particle Size of Magnetic Particle 1>
The volume average particle size of the magnetic particle 1 is the cumulative volume distribution from the small particle size side with respect to the particle size range (channel) obtained by dividing the particle size distribution obtained by the laser explanation particle size distribution measuring apparatus LA-700 (Horiba Seisakusho). By subtracting, the particle diameter at 50% cumulative was taken as the volume average particle diameter. The volume average particle size of the pulverized product is the same.

<Measurement of BET specific surface area of magnetic particle 1>
The BET specific surface area of the magnetic particle 1 is obtained by putting 5 parts by mass of the magnetic particle 1 into a cell of an SA3100 specific surface area measuring device (Beckman Coulter), performing a degassing treatment at 60 ° C. for 120 minutes, and then mixing a mixed gas of nitrogen and helium ( 30:70), and nitrogen was substituted, and measurement was performed by a three-point method according to JIS Z 8830 (2001 edition).

<Measurement of volume resistance of magnetic particle 1>
The volume resistance of the magnetic particle 1 is such that two electrode plates face each other in parallel with a width of 1 mm, and 0.25 part by mass of the magnetic particle 1 is put between them and held by a magnet having a cross-sectional area of 2.4 cm ² . The applied voltage was applied (the electric field at this time was 24000 V / cm), the current value was measured, and the current value was calculated.

  Into a vacuum degassing type 5 L kneader, 2000 parts by mass of the above magnetic particles 1 were added, and 560 parts by mass of the coating layer forming solution was added. While stirring, the pressure was reduced to −200 mmHg at 60 ° C. and mixed for 15 minutes. The carrier 1 was obtained by stirring and drying at / -720 mHg for 30 minutes and sieving with a 75 μm mesh sieving screen.

  When magnetic particles are collected from the developer and the Sm, Ra, BET specific surface area, and volume resistance of the magnetic particles are measured, the developer is first blown with air to remove the toner and collect the carrier. Then, 10 parts by mass of carrier is added to 100 parts by mass of toluene, and ultrasonic stirring is performed for 30 seconds under the condition of 40 kHz to dissolve the coating layer. The filter is separated into a magnetic particle and a solution in which the coating layer is dissolved using an arbitrary filter paper according to the particle size. The magnetic particles remaining on the filter paper are washed with 20 parts by mass of toluene, and the magnetic particles remaining on the filter paper are recovered. The recovered magnetic particles are similarly added to 100 parts by mass of toluene, and ultrasonic stirring is performed for 30 seconds under the condition of 40 kHz. Filtration is performed in the same manner as described above, and 20 parts by mass of toluene is poured to wash the magnetic particles remaining on the filter paper. This is done a total of 10 times. Finally, the collected magnetic particles are dried. The Sm, Ra, BET specific surface area, and volume resistance of the magnetic particles thus obtained are measured under the above conditions.

(Preparation of carrier 2)
Except for adding 1.5 parts by mass of SiO ₂ as a carrier material, setting the volume average particle size of the pulverized product to 2.1 μm, and setting the firing temperature of the main firing to 1150 ° C. (surface oxidation temperature 900 ° C.). The magnetic particles 2 were obtained under the same conditions as for the magnetic particles 1. The volume average particle diameter of the magnetic particles 2 is 35 μm, the Sm of the magnetic particles 2 is 3.2, the Ra of the magnetic particles 2 is 0.4, and the BET specific surface area of the magnetic particles 2 is 0.10 m ² / g, and the volume resistance of the magnetic particles 2 was 6.5 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 2, the same conditions as those of the carrier 1 were performed, and the carrier 2 was obtained.

(Preparation of carrier 3)
Other than that the volume average particle size of the pulverized product was 1.2 μm, the firing temperature of the main firing was 1050 ° C. (surface oxidation temperature 950 ° C.), and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.5%. Was performed under the same conditions as for magnetic particles 1 to obtain magnetic particles 3. The volume average particle size of the magnetic particles 3 is 35 μm, the Sm of the magnetic particles 3 is 1.2, the Ra of the magnetic particles 3 is 0.5, and the BET specific surface area of the magnetic particles 3 is 0.13 m ² / g, and the volume resistance of the magnetic particles 3 was 7.5 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 3, the same conditions as those of the carrier 1 were used to obtain the carrier 3.

(Preparation of carrier 4)
The magnetic particles 4 are obtained under the same conditions as the magnetic particles 1 except that 1.2 parts by mass of SiO ₂ is added as a carrier material and the main baking is performed in an oxygen-nitrogen mixed atmosphere having an oxygen concentration of 0.8%. It was. The volume average particle diameter of the magnetic particles 4 is 35 μm, the Sm of the magnetic particles 4 is 2.5, the Ra of the magnetic particles 4 is 0.2, and the BET specific surface area of the magnetic particles 4 is 0.10 m ² / g, and the volume resistance of the magnetic particles 4 was 6.4 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 4, it was performed under the same conditions as the carrier 1 to obtain the carrier 4.

(Preparation of carrier 5)
The magnetic particles 5 were prepared under the same conditions as the magnetic particles 1 except that the volume average particle size of the pulverized product was 2.0 μm and the firing temperature of the main firing was 1150 ° C. (surface oxidation temperature 880 ° C.). Obtained. The volume average particle diameter of the magnetic particles 5 is 35 μm, the Sm of the magnetic particles 5 is 3.0, the Ra of the magnetic particles 5 is 0.4, and the BET specific surface area of the magnetic particles 5 is 0.14 m ² / g, and the volume resistance of the magnetic particles 5 was 6.0 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 5, the same conditions as those of the carrier 1 were used, and the carrier 5 was obtained.

(Preparation of carrier 6)
Except that the volume average particle size of the pulverized product was 1.2 μm, the firing temperature of the main firing was 1170 (surface oxidation temperature 970 ° C.), and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.2%, The magnetic particles 6 were obtained under the same conditions as the magnetic particles 1. The volume average particle diameter of the magnetic particles 6 is 35 μm, the Sm of the magnetic particles 6 is 1.0, the Ra of the magnetic particles 6 is 0.3, and the BET specific surface area of the magnetic particles 6 is 0.09 m ² / g, and the volume resistance of the magnetic particles 6 was 6.8 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 6, the same conditions as those of the carrier 1 were performed to obtain a carrier 6.

(Preparation of carrier 7)
The addition of 1.4 parts by mass of SiO ₂ as a carrier material, the volume average particle size of the pulverized product was 2.2 μm, the firing temperature of the main firing was 1120 (surface oxidation temperature 920 ° C.), and the oxygen concentration was 1.5 The magnetic particles 7 were obtained under the same conditions as the magnetic particles 1 except that the main firing was performed in a mixed atmosphere of oxygen and nitrogen. The volume average particle diameter of the magnetic particles 7 is 35 μm, the Sm of the magnetic particles 7 is 3.5, the Ra of the magnetic particles 7 is 0.6, and the BET specific surface area of the magnetic particles 7 is 0.12 m ² / g and the volume resistance of the magnetic particles 7 was 7.6 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 7, it was performed under the same conditions as the carrier 1 to obtain the carrier 7.

(Preparation of carrier 8)
Except that the volume average particle size of the pulverized product was 2.0 μm, the firing temperature of the main firing was 1170 (surface oxidation temperature 900 ° C.), and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.5%, The magnetic particles 8 were obtained under the same conditions as the magnetic particles 1. The volume average particle diameter of the magnetic particles 8 is 35 μm, the Sm of the magnetic particles 8 is 3.0, the Ra of the magnetic particles 8 is 0.7, and the BET specific surface area of the magnetic particles 8 is 0.12 m ² / g, and the volume resistance of the magnetic particles 8 was 7.7 log Ωcm under an electric field of 24000 V / cm. The carrier 8 was obtained under the same conditions as the carrier 1 except that the magnetic particle 1 was changed to the magnetic particle 8.

(Preparation of carrier 9)
Except that the volume average particle size of the pulverized product was 2.1 μm, the firing temperature of the main firing was 1170 (surface oxidation temperature 970 ° C.), and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.0%, The magnetic particles 9 were obtained under the same conditions as the magnetic particles 1. The volume average particle size of the magnetic particles 9 is 35 μm, the Sm of the magnetic particles 9 is 3.0, the Ra of the magnetic particles 9 is 0.5, and the BET specific surface area of the magnetic particles 9 is 0.08 m ² / The volume resistance of the magnetic particles 9 was 7.8 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 9, it was performed under the same conditions as the carrier 1 to obtain the carrier 9.

(Preparation of carrier 10)
Except that the volume average particle size of the pulverized product was 2.1 μm, the firing temperature of the main firing was 1120 (surface oxidation temperature 970 ° C.), and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.0%, The magnetic particles 10 were obtained under the same conditions as the magnetic particles 1. The volume average particle size of the magnetic particles 10 is 35 μm, the Sm of the magnetic particles 10 is 2.5, the Ra of the magnetic particles 10 is 0.4, and the BET specific surface area of the magnetic particles 10 is 0.10 m ² / g, and the volume resistance of the magnetic particle 10 was 8 log Ωcm under an electric field of 24000 V / cm. The carrier 10 was obtained under the same conditions as the carrier 1 except that the magnetic particle 1 was changed to the magnetic particle 10.

(Preparation of carrier 11)
The addition of 1.5 parts by mass of SiO ₂ as a carrier material, the volume average particle size of the pulverized product was 2.3 μm, the firing temperature of the main firing was 1150 ° C. (surface oxidation temperature 900 ° C.), and the oxygen concentration was 0.1. The magnetic particles 11 were obtained under the same conditions as the magnetic particles 1 except that the main calcination was performed in an 8% oxygen-nitrogen mixed atmosphere. The volume average particle diameter of the magnetic particles 11 is 35 μm, the Sm of the magnetic particles 11 is 3.6, the Ra of the magnetic particles 11 is 0.3, and the BET specific surface area of the magnetic particles 11 is 0.08 m ² / The volume resistance of the magnetic particles 11 was 6.5 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 11, it was performed under the same conditions as the carrier 1 to obtain the carrier 11.

(Preparation of carrier 12)
Except that the volume average particle diameter of the pulverized product was 1.2 μm, and that the firing temperature of the main firing was 1050 ° C. (surface oxidation temperature 920 ° C.) and the main firing was performed in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 0.8%. The magnetic particles 12 were obtained under the same conditions as for the magnetic particles 1. The volume average particle diameter of the magnetic particles 12 is 35 μm, the Sm of the magnetic particles 12 is 0.9, the Ra of the magnetic particles 12 is 0.7, and the BET specific surface area of the magnetic particles 12 is 0.13 m ² / g, and the volume resistance of the magnetic particles 12 was 7.5 log Ωcm under an electric field of 24000 V / cm. And except having changed the magnetic particle 1 into the magnetic particle 12, it carried out on the conditions similar to the carrier 1, and obtained the carrier 12.

(Preparation of carrier 13)
Except for adding 1.0 part by mass of SiO ₂ as a carrier material, and firing at a firing temperature of 1150 (surface oxidation temperature of 880 ° C.) in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.5%, It carried out on the conditions similar to the magnetic particle 1, and the magnetic particle 13 was obtained. The volume average particle diameter of the magnetic particles 13 is 35 μm, the Sm of the magnetic particles 13 is 2.2, the Ra of the magnetic particles 13 is 0.8, and the BET specific surface area of the magnetic particles 13 is 0.10 m ² / g, and the volume resistance of the magnetic particles 13 was 6.2 log Ωcm under an electric field of 24000 V / cm. And except having changed the magnetic particle 1 into the magnetic particle 13, it carried out on the conditions similar to the carrier 1, and the carrier 13 was obtained.

(Preparation of carrier 14)
The magnetic particles 14 were obtained under the same conditions as those of the magnetic particles 1 except that the main baking was performed at 1160 (surface oxidation temperature 920 ° C.) and an oxygen-nitrogen mixed atmosphere having an oxygen concentration of 0.50%. It was. The volume average particle diameter of the magnetic particles 14 is 35 μm, the Sm of the magnetic particles 14 is 2.1, the Ra of the magnetic particles 14 is 0.1, and the BET specific surface area of the magnetic particles 14 is 0.09 m ² / g, and the volume resistance of the magnetic particles 14 was 7.6 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 14, the same conditions as those of the carrier 1 were used to obtain the carrier 14.

(Preparation of carrier 15)
The magnetic particles 15 were obtained under the same conditions as the magnetic particles 1 except that the main baking was performed at 1100 ° C. in an oxygen-nitrogen mixed atmosphere having an oxygen concentration of 1.0%. The volume average particle diameter of the magnetic particles 15 is 35 μm, the Sm of the magnetic particles 15 is 2.0, the Ra of the magnetic particles 15 is 0.7, and the BET specific surface area of the magnetic particles 15 is 0.18 m ² / g, and the volume resistance of the magnetic particles 15 was 5.00 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 15, the same conditions as those of the carrier 1 were used, and the carrier 15 was obtained.

(Preparation of carrier 16)
Conditions similar to those of the magnetic particle 1 except that the volume average particle size of the pulverized product is 1.2 μm, the oxygen concentration of the main firing is 0.9%, and the firing temperature is 1160 ° C. (surface oxidation temperature 980 ° C.). To obtain magnetic particles 16. The volume average particle diameter of the magnetic particles 16 is 35 μm, the Sm of the magnetic particles 16 is 2.0, the Ra of the magnetic particles 16 is 0.2, and the BET specific surface area of the magnetic particles 16 is 0.07 m ² / g, and the volume resistance of the magnetic particles 16 was 8.00 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particles 1 were changed to the magnetic particles 16, it was performed under the same conditions as the carrier 1 to obtain a carrier 16.

(Preparation of carrier 17)
The magnetic particles 17 were subjected to the same conditions as the magnetic particles 1 except that the main baking was performed at 1150 ° C. (surface oxidation temperature of 970 ° C.) and an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1.20%. Obtained. The Sm of the magnetic particles 17 is 2.4, the Ra of the magnetic particles 17 is 0.2, the BET specific surface area of the magnetic particles 17 is 0.09 m ² / g, and the volume resistance of the magnetic particles 17 is 24,000 V / It was 9.0 log Ωcm under an electric field of cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 17, it was performed under the same conditions as the carrier 1 to obtain the carrier 17.

(Preparation of carrier 18)
Magnetic particles 18 were obtained under the same conditions as for magnetic particles 1 except that 1.5 parts by mass of SiO ₂ was added as a carrier material and the volume average particle size of the pulverized product was 2.1 μm. The volume average particle diameter of the magnetic particles 18 is 35 μm, the Sm of the magnetic particles 18 is 3.5, the Ra of the magnetic particles 18 is 0.5, and the BET specific surface area of the magnetic particles 18 is 0.14 m ² / g, and the volume resistance of the magnetic particles 18 was 5.00 log Ωcm under an electric field of 24000 V / cm. Then, except that the magnetic particle 1 was changed to the magnetic particle 18, it was performed under the same conditions as the carrier 1 to obtain the carrier 18.

Table 1 summarizes the addition amount of SiO ₂ in obtaining the magnetic particles 1 to 18, the volume average particle size of the pulverized product, the main firing temperature, the oxygen concentration, and the surface oxidation temperature. Table 2 summarizes the Sm, Ra, BET specific surface area, and volume resistance of the magnetic particles 1-18.

(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)
Pure Cyan developer (toner concentration 8%) was charged into the Cyan position of a DCC400 remodeling machine (toner concentration fixed at 8%, print speed 45 sheets / min). The sheet was left for 24 hours in an environment of 23 ° C. and 50% RH, and 100 solid patches were printed on A4 plain paper so that the area coverage was 2%. Next, the print speed of the DCC400 remodeling machine is adjusted to 90 sheets / min, the developer is charged into the Cyan position of the DCC400 remodeling machine, and left in an environment of 30 ° C. and 88% RH for 24 hours. 100 solid patches were printed on paper so that the area coverage was 2%. The image density difference ΔE of each 100th image was determined. The image density difference ΔE was obtained from CIE L * a * b * standardized by the International Commission on Illumination (CIE) using X-rite 938 (manufactured by X-Rite). The image density difference (ΔE) was evaluated according to the following criteria. The obtained results are shown in Table 3.

(Image density difference)
A: No difference in image density (when ΔE is 1.0 or less)
○: Little difference in image density (when ΔE is 1.0 or more and 2.0 or less)
Δ: Image density is slightly different (when ΔE is more than 2.0 and 3.0 or less)
X: Image density difference (when ΔE is more than 3.0 and 4.0 or less)
XX: Image density difference is remarkable (when ΔE exceeds 4.0)

<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.

<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 7. The obtained results are shown in Table 3.

<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 8. The obtained results are shown in Table 3.

<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 9. The obtained results are shown in Table 3.

<Example 10>
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 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 11. 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 12. 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 13. 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 14. 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 15. 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 16. 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 17. 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 18. The obtained results are shown in Table 3.

As the results of Examples 1 to 10 show, the Sm of the magnetic particles is in the range of 1.0 to 3.5, the Ra of the surface of the magnetic particles is in the range of 0.2 to 0.7, and the magnetic particles the BET specific surface area and 0.08 m ² / g or more 0.14 m ² / g or less in the range, the volume resistivity of the magnetic particles in an electric field of 24000V / cm, the magnetic particles with 8.0logΩcm following range of 6.0logΩcm Compared to Comparative Examples 1 to 8 using magnetic particles that do not satisfy at least one of Sm, Ra, BET specific surface area, and volume resistance of the magnetic particles, in a high-temperature and high-humidity environment. In addition, even when an image was formed at a high speed, the difference in image density generated in the image on the recording medium was suppressed. Further, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 2.5 to 3.0, the arithmetic average roughness Ra of the surface of the magnetic particles is in the range of 0.4 to 0.7, and the magnetic particles a BET specific surface area in the range of less 0.08 m ² / g or more 0.12 m ² / g, a volume resistivity of magnetic particles, under an electric field of 24000V / cm, at 7.8logΩcm following range of 7.0logΩcm In Examples 1, 8, and 9, compared to Examples 2 to 7 and 10, even if an image is formed in a high-temperature and high-humidity environment and at a high speed, there is a difference in image density that occurs in the image on the recording medium. More 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 rail, 117, 118 opening, 200 process cartridge, 300 recording medium, 301 image forming device, 310 charging unit, 312 exposure unit, 314 electrophotographic photosensitive member, 316 developing unit, 318 transfer unit, 320 Cleaning unit, 322 fixing unit, 324 recording medium, 511 layer thickness regulating member, 512 cover unit, 521 magnet roll, 522 developing sleeve.

Claims (5)

It has magnetic particles, the average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 1.0 to 3.5, and the arithmetic average roughness Ra of the surface of the magnetic particles is 0.2 to 0.7 in the range, the BET specific surface area of the magnetic particles is in the range of less 0.08 m ² / g or more 0.14 m ² / g, a volume resistivity of said magnetic particles, under an electric field of 24000V / cm, 6.0logΩcm A carrier for developing an electrostatic image, wherein the carrier is in a range of 8.0 log Ωcm or less. The average interval Sm of the irregularities on the surface of the magnetic particles is in the range of 2.5 to 3.0, the arithmetic average roughness Ra of the surface of the magnetic particles is in the range of 0.4 to 0.7, and the magnetic ranges BET specific surface area of 0.08 m ² / g or more 0.12m in ² / g or less of the particles, the volume resistivity of the magnetic particles, under an electric field of 24000V / cm, less than 7.0logΩcm 7.8logΩcm 2. The carrier for developing an electrostatic charge image according to claim 1, wherein the carrier for developing an electrostatic image is in a range.   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