JP6536501B2 - Two-component developer and manufacturing method thereof - Google Patents

Description

  The present invention relates to a carrier for electrostatic latent image development and a method for producing the same, and a two-component developer and a method for producing the same.

  For example, a two-component developer including a toner for electrostatic latent image development and a carrier for electrostatic latent image development for charging the electrostatic latent image development toner by friction is known. As the carrier, a carrier containing a carrier core (for example, porous ferrite particles) and a resin layer coated on the surface of the carrier core can be used (for example, Patent Document 1). Patent Document 1 describes the following. At the entrance of the pores formed on the surface of the carrier core, electrostatically aggregated resin particles are present so as to bridge the bridge. Therefore, the pores formed on the surface of the carrier core are blocked by the resin particles.

JP 2012-173375 A

  The toner particles contained in the toner may include toner base particles and an external additive. When the toner particles contain an external additive, the flowability of the toner particles and the heat resistant storage stability of the toner particles are improved. Furthermore, at the time of image formation, the adhesion of toner particles to the developing roller, the photosensitive member and the transfer belt can be reduced.

  However, in a two-component developer containing toner particles including an external additive and a carrier, the external additive may move from the surface of the toner base particle to the carrier. The external additive transferred to the carrier adheres to the surface of the carrier particles, so that triboelectric charging between the toner and the carrier hardly occurs. As a result, the charge amount of the toner is reduced. And, it is considered that the decrease in the charge amount of the toner due to the movement of the external additive from the surface of the toner base particle to the carrier becomes remarkable when performing continuous printing.

  The present invention has been made in view of the above-described circumstances, and a purpose thereof is a two-component developer capable of maintaining the charge amount of toner within an appropriate range even when continuous printing is performed, and the two-component developer It is to provide a manufacturing method. Another object of the present invention is to provide a carrier for electrostatic latent image development capable of maintaining the charge amount of toner within an appropriate range even when continuous printing is performed, and a method of manufacturing the same.

  The two-component developer according to the present invention includes an electrostatic latent image developing toner containing a plurality of toner particles, and an electrostatic latent image developing carrier containing a plurality of carrier particles. The toner particles include toner base particles and an external additive externally added to the surface of the toner base particles. The carrier particles include a carrier core and a coat layer covering the surface of the carrier core. The external additive contains a plurality of first resin particles containing a first resin. The coat layer contains a second resin. The thickness of the coating layer is larger than the diameter of the first resin particle. A plurality of recesses are formed on the surface of the coat layer, and the opening diameter of the recesses is one or more and three or less times the diameter of the first resin particle.

  The carrier for developing an electrostatic latent image according to the present invention includes a plurality of carrier particles including a carrier core and a coat layer covering the surface of the carrier core. The coat layer contains a resin. A plurality of concave portions are formed on the surface of the coating layer, and the opening diameter of the concave portions is 50 nm or more and 600 nm or less.

  The method for producing a two-component developer according to the present invention comprises the steps of producing a toner for developing an electrostatic latent image, a step of producing a carrier for developing an electrostatic latent image, the toner for developing an electrostatic latent image and the electrostatic latent image. And a mixing step of mixing with the image developing carrier. The manufacturing process of the electrostatic latent image developing toner includes a process of manufacturing toner particles including toner base particles and an external additive externally added to the surface of the toner base particles. The manufacturing process of the carrier for electrostatic latent image development includes a coating process of covering the surface of the carrier core with a coating layer including a surface layer, and a treatment process of treating the carrier core whose surface is covered with the coating layer with a solvent including. The external additive contains a plurality of first resin particles containing a first resin. The surface layer is located on the outermost side in the radial direction of the carrier core in the coating layer, and includes a second resin and a third resin particle containing a third resin. The third resin particles have a diameter of 1 to 3 times the diameter of the first resin particles. In the treatment step, the third resin particles exposed on the surface of the coat layer are selectively dissolved.

  According to the present invention, even when continuous printing is performed, the charge amount of toner can be maintained within an appropriate range.

It is a figure which shows schematic structure of the two-component developer which concerns on this embodiment. It is an enlarged view of II area | region shown in FIG. It is a figure for demonstrating the effect which the two-component developer which concerns on this embodiment has. (A)-(c) is a figure which shows an example of the manufacturing method of the carrier which concerns on this embodiment to process order. (A)-(d) is a figure which shows an example of the manufacturing method of the carrier which concerns on this embodiment to process order.

  Embodiments of the present invention will be described. The evaluation results (for example, values indicating the shape or physical properties) of the powder (more specifically, toner base particles, external additives, toner particles, carrier particles, etc.) are not particularly limited. The average number of particles is selected from the above and the number average of the values measured for each of the average particles.

The number average particle diameter of the powder is the number average value of the circle equivalent diameter of the primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope if nothing is specified. . In addition, the measurement value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering type particle size distribution measuring apparatus (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. Value.

  Hereinafter, “system” may be added after the compound name to generically generically refer to the compound and its derivative. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Moreover, acryl and methacryl may be generically called "(meth) acryl" generically. In addition, acrylonitrile and methacrylonitrile may be generically generically referred to as "(meth) acrylonitrile".

[Configuration of Two-Component Developer According to this Embodiment]
The two-component developer according to this embodiment is a toner for electrostatic latent image development containing a plurality of toner particles (hereinafter sometimes referred to as a toner) and a carrier for electrostatic latent image development containing a plurality of carrier particles (hereinafter , And may be described as carrier). The toner particles include toner base particles and an external additive externally added to the surface of the toner base particles. The carrier particles include a carrier core and a coat layer covering the surface of the carrier core. The external additive contains a plurality of first resin particles containing a first resin. The coat layer contains a second resin. The thickness of the coat layer is larger than the diameter of the first resin particle. A plurality of recesses are formed on the surface of the coat layer. The opening diameter of the recess is one or more and three or less times the diameter of the first resin particle. As a result, even when continuous printing is performed, the charge amount of the toner can be maintained within an appropriate range.

  Hereinafter, an example of the two-component developer according to the present embodiment will be described using FIGS. 1 to 3. FIG. 1 is a view showing a schematic configuration of a two-component developer according to the present embodiment. FIG. 2 is an enlarged view of a II region shown in FIG. FIG. 3 is a view for explaining an effect exerted by the two-component developer according to the present embodiment.

The two-component developer 100 includes a toner including a plurality of toner particles 10 and a carrier including a plurality of carrier particles 20. The toner particles 10 include toner base particles 11 and an external additive externally added to the surface 11 a of the toner base particles 11. Carrier particle 20 includes carrier core 21 and coat layer 23 covering surface 21 a of carrier core 21. The external additive contains a plurality of first resin particles 13 containing a first resin. The coat layer 23 contains a second resin. The thickness T of the coat layer 23 is larger than the diameter r ₁ of the first resin particle 13. A plurality of recesses 27 (see FIG. 2) are formed on the surface 23 a of the coating layer 23, and the opening diameter R of the recesses 27 is one or more and three or less times the diameter r ₁ of the first resin particles 13. Hereinafter, the two-component developer according to the present embodiment will be further described after the diameter r ₁ of the first resin particle 13, the thickness T of the coating layer 23, the opening diameter R of the recess 27 and the depth D of the recess 27 are described. Do.

The diameter r ₁ of the first resin particles 13 refers to the number average length in a major axis direction of the scanning electron microscope (SEM (Scanning Electron Microscope)) first resin particles 13 was measured using a.

  The thickness T of the coating layer 23 means the size of the coating layer 23 in the radial direction of the carrier particles 20, and is measured according to the method described below. First, a cross-sectional TEM photograph of the carrier particle 20 is taken using a transmission electron microscope (TEM (Transmission Electron Microscope), for example, “H-7100 FA” manufactured by Hitachi High-Technologies Corporation). Next, the cross-sectional TEM photograph of the obtained carrier particles 20 is analyzed using image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). Specifically, two straight lines orthogonal to each other at the approximate center of the cross section of the carrier particle 20 are drawn. In each of the two straight lines, the length from the interface between the carrier core 21 and the coat layer 23 (corresponding to the surface 21 a of the carrier core 21) to the surface 23 a of the coat layer 23 is measured. The average value of the four lengths measured in this manner is taken as the thickness of the coat layer included in one carrier particle 20. The thickness of the coating layer 23 is measured for the plurality of carrier particles 20, and the average value of the thickness of the coating layer 23 included in the plurality of carrier particles 20 (target of measurement) is determined. The average value of the thickness of the coat layer 23 determined in this manner is taken as "the thickness T of the coat layer 23".

  When the boundary between the carrier core 21 and the coating layer 23 is unclear in the cross-sectional TEM photograph of the carrier particle 20, the cross-sectional TEM photograph of the carrier particle 20 is referred to as electron energy loss spectroscopy (EELS) It is preferable to analyze using a detector (for example, "GIF TRIDIEM (registered trademark)" manufactured by Gatan Co., Ltd.) and an image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). Thereby, the boundary between the carrier core 21 and the coat layer 23 becomes clear in the cross-sectional TEM photograph of the carrier particle 20, and therefore, the thickness T of the coat layer 23 can be obtained.

  The open hole diameter R of the recess 27 means the size (diameter) of the recess 27 in the surface 23 a of the coating layer 23 and is measured according to the method described below. First, the entire surface of the carrier particle 20 is observed using a field emission scanning electron microscope (FE-SEM (Field Emission Scanning Electron Microscope), for example, “JSM-7600F” manufactured by JEOL Ltd.). The obtained image is analyzed using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). A plurality of recesses 27 are detected by this image analysis. The circle equivalent diameter of each opening of the plurality of recesses 27 detected is determined, and the average value thereof is taken as "the opening diameter R of the recess 27".

  The depth D of the recess 27 described later means the size of the recess 27 in the radial direction of the carrier particle 20, and is measured according to the method of measuring the thickness T of the coat layer 23.

  In a two-component developer containing toner particles including an external additive and a carrier, the external additive may move from the surface of the toner base particle to the carrier. The external additive transferred to the carrier adheres to the surface of the carrier particles, so that triboelectric charging between the toner and the carrier hardly occurs. As a result, the charge amount of the toner is reduced. Here, it is considered that the decrease in the charge amount of the toner due to the movement of the external additive from the surface of the toner base particle to the carrier becomes remarkable when performing continuous printing. In addition, the particle diameter of the resin particles used as the external additive is larger than the particle diameter of the inorganic particles (for example, silica particles) used as the external additive. Therefore, the decrease in the charge amount of the toner due to the movement of the external additive from the surface of the toner base particle to the carrier becomes remarkable when resin particles are used as the external additive. From these facts, the decrease in the charge amount of the toner due to the movement of the external additive from the surface of the toner base particle to the carrier is remarkable when performing continuous printing using a toner containing resin particles as the external additive. Become.

  However, in the carrier particles 20 contained in the two-component developer 100, a plurality of recesses 27 are formed on the surface 23a of the coat layer 23. As a result, although the toner particles 10 contain the first resin particles 13 as an external additive, it is possible to prevent a decrease in the charge amount of the toner when continuous printing is performed.

The two-component developer 100 will be described in more detail with reference to FIG. In the two-component developer 100, inserted for opening diameter R of the concave portion 27 is diameter r ₁ or more of the first resin particles 13, the first resin particles 13 having moved from the surface 11a of the toner mother particle 11 to the carrier in the recess 27 It is easy to be done. Further, since the opening diameter R of the recess 27 is not more than three times the diameter r ₁ of the first resin particle 13, the first resin particle 13 inserted into the recess 27 can be prevented from escaping outside the recess 27. Further, since the thickness T of the coating layer 23 is larger than the diameter r ₁ of the first resin particles 13 may be the depth D of the concave portion 27 and the diameter r ₁ or more of the first resin particles 13. Accordingly, it is possible to prevent the first resin particles 13 accommodated in the recess 27 from protruding outward in the radial direction of the carrier particles 20 from the surface 23 a of the coating layer 23. From these facts, the first resin particles 13 moved from the surface 11 a of the toner base particle 11 to the carrier are accommodated in the recess 27 without protruding outward from the surface 23 a of the coating layer 23 in the radial direction of the carrier particles 20. Therefore, even when the movement of the first resin particles 13 from the surface 11 a of the toner base particles 11 to the carrier is remarkable, the contact between the toner particles 10 and the coat layer 23 of the carrier particles 20 is secured.

  When the contact between the toner particles 10 and the coat layer 23 of the carrier particles 20 is secured, the toner and the carrier cause frictional charging. Therefore, in the two-component developer 100, the movement of the first resin particles 13 from the surface 11a of the toner base particles 11 to the carrier occurs even though the toner particles 10 contain the first resin particles 13 as an external additive. It is possible to prevent the decrease of the charge amount of the toner when it becomes remarkable. For example, even when continuous printing is performed, the charge amount of the toner can be maintained within an appropriate range.

  As described above, in the two-component developer 100, the plurality of the concave portions 27 are formed on the surface 23a of the coat layer 23, so that the charge amount of the toner can be maintained within an appropriate range even when continuous printing is performed. However, when the recess is formed on the surface of the coating layer, the carrier core may be exposed. When the carrier core is exposed, charge leakage from the toner to the carrier is likely to occur in the portion where the carrier core is exposed. As a result, the charge amount of the toner may be reduced.

However, in the two-component developer 100, the depth D of the concave portion 27 can be smaller than the thickness T of the coating layer 23. Specifically, as described above, when the depth D of the recess 27 is equal to or more than the diameter r ₁ of the first resin particle 13, the first resin particle 13 accommodated in the recess 27 is the carrier particle from the surface 23 a of the coating layer 23 It can be prevented from projecting radially outward of 20. Therefore, in the two-component developer 100, the depth D of the recess 27 is preferably equal to or greater than the diameter r ₁ of the first resin particle 13. Further, the thickness T of the coat layer 23 is larger than the diameter r ₁ of the first resin particle 13. From these facts, the depth D of the recess 27 can be made smaller than the thickness T of the coating layer 23.

  If the depth D of the recess 27 is smaller than the thickness T of the coat layer 23, the bottom surface 27 a of the recess 27 is located radially outward of the carrier particle 20 than the surface 21 a of the carrier core 21. That is, the entire surface 21 a of the carrier core 21 is covered with the coat layer 23. Therefore, since the leak of the charge from the toner to the carrier can be prevented, it is possible to prevent the decrease in the charge amount of the toner due to the formation of the concave portion 27 on the surface 23 a of the coat layer 23.

Furthermore, in the two-component developer 100, the opening diameter R of the recess 27 is three times or less the diameter r ₁ of the first resin particle 13. Thereby, on the surface 23 a of the coat layer 23, a contact area with the toner particles 10 (coat layer) is secured while securing the number of concave portions 27 necessary to accommodate the first resin particles 13 detached from the toner particles 10. It is possible to secure a region where the recess 27 is not formed in the surface 23 a of 23. Also in this case, it is possible to prevent the decrease in the charge amount of the toner due to the formation of the concave portion 27 on the surface 23 a of the coat layer 23. Therefore, even when the movement of the first resin particle 13 from the surface 11 a of the toner mother particle 11 to the carrier is not remarkable, the charge amount of the toner can be maintained within the desired range.

  As described above with reference to FIG. 3, the two-component developer 100 can maintain the charge amount of the toner within an appropriate range even when continuous printing is performed. Therefore, even when continuous printing is performed, the fluctuation of the image density can be suppressed.

The relationship between the diameter r ₁ of the first resin particle 13 and the thickness T of the coating layer 23 is further shown. The concave portion 27 is preferably formed by selectively dissolving resin particles (third resin particles described later) using a specific solvent. For example, in the case of forming the recess 27 whose opening diameter R is one time the diameter r ₁ of the first resin particle 13, the resin particle whose diameter is about one time the diameter r ₁ of the first resin particle 13 is dissolved It is preferable to Therefore, the depth D of the recess 27 to be formed is equal to or less than one time the diameter r ₁ of the first resin particle 13. Thus, if the thickness T of the coat layer 23 is larger than 1 time the diameter r ₁ of the first resin particle 13, for example, the thickness T of the coat layer 23 is 1.5 of the diameter r ₁ of the first resin particle 13. If it is twice or more, the depth D of the recess 27 can be smaller than the thickness T of the coat layer 23. Therefore, the exposure of the carrier core 21 can be prevented even in the portion of the coating layer 23 in which the recess 27 is formed.

Further, in the case of forming the recess 27 in which the opening diameter R is three times the diameter r ₁ of the first resin particle 13, the resin particle whose diameter is about three times the diameter r ₁ of the first resin particle 13 is dissolved. It is preferable to Therefore, the depth D of the recess 27 to be formed is 3 times or less the diameter r ₁ of the first resin particle 13. Thus, if the thickness T of the coating layer 23 is greater than three times the diameter r ₁ of the first resin particle 13, for example, the thickness T of the coating layer 23 is 3.5 of the diameter r ₁ of the first resin particle 13. If it is twice or more, the depth D of the recess 27 can be smaller than the thickness T of the coat layer 23. Therefore, the exposure of the carrier core 21 can be prevented even in the portion of the coating layer 23 in which the recess 27 is formed. From the above, the thickness T of the coating layer 23 is preferably 1.5 or more times the diameter r ₁ of the first resin particles 13, and more preferably 3.5 or more times the diameter r ₁ of the first resin particles 13 It is. It is preferable from the viewpoint of the dispersibility of the carrier particles 20, the thickness T of the coating layer 23 is less than 15 times the diameter r ₁ of the first resin particles 13. The thickness T of the coating layer 23 is preferably, for example, 500 nm or more and 1500 nm or less.

  When the recess 27 is formed by selectively dissolving a resin particle (third resin particle described later) using a specific solvent, the resin particle used to form the recess 27 is of the coat layer 23. It may remain inside. This is shown in [Production of carrier according to this embodiment] in the following [Production of a two-component developer according to this embodiment].

By the way, unevenness is often formed on the surface of the carrier core, and the unevenness of the surface of the coating layer is easily affected by the unevenness of the surface of the carrier core. However, the depressions 27 do not include the unevenness formed on the surface 23 a of the coat layer 23 under the influence of the unevenness of the surface 21 a of the carrier core 21. The depth D of the recess 27 is preferably 1/2 or more of the diameter r ₁ of the first resin particle 13, and more preferably the diameter r ₁ of the first resin particle 13 or more. The depth D of the recess 27 is preferably smaller than the thickness T of the coating layer 23.

Specifically, if the depth D of the recess 27 is equal to or more than half the diameter r ₁ of the first resin particle 13, the first resin particle 13 accommodated in the recess 27 escapes out of the recess 27. It can prevent. As a result, it is possible to suppress a decrease in the charge amount of toner when continuous printing is performed.

When the depth D of the recess 27 is equal to or more than the diameter r ₁ of the first resin particle 13, the first resin particle 13 accommodated in the recess 27 can be prevented from protruding from the surface 23 a of the coating layer 23. Thereby, even when the movement of the first resin particles 13 from the surface 11 a of the toner base particles 11 to the carrier becomes remarkable, the contact between the toner particles 10 and the coat layer 23 of the carrier particles 20 can be secured. Therefore, even when continuous printing is performed, the charge amount of the toner can be maintained within an appropriate range.

  If the depth D of the recess 27 is smaller than the thickness T of the coating layer 23, exposure of the carrier core 21 can be prevented even in the portion of the coating layer 23 in which the recess 27 is formed. As a result, the charge amount of toner in continuous printing can be maintained within a desired range.

  Hereafter, the preferable form of the two-component developer 100 is shown using FIGS. 1-3. Preferably, the hole area ratio of the recess 27 in the surface 23 a of the coating layer 23 is 30% or more and 60% or less. If the hole area ratio of the recess 27 in the surface 23 a of the coating layer 23 is 30% or more, the amount of the first resin particles 13 accommodated in the recess 27 can be further secured. Thereby, even when the movement of the first resin particles 13 from the surface 11 a of the toner base particles 11 to the carrier becomes remarkable, the contact between the toner particles 10 and the coat layer 23 of the carrier particles 20 is easily ensured. Become. Therefore, even when continuous printing is performed, the charge amount of the toner can be easily maintained in an appropriate range. In addition, when the opening ratio of the recess 27 on the surface 23 a of the coating layer 23 is 60% or less, while securing the number of recesses 27 necessary to accommodate the first resin particles 13 detached from the toner particles 10. The contact area with the toner particles 10 can be further secured. As a result, the charge amount of toner in continuous printing can be effectively maintained.

  As described above, when the opening ratio of the concave portion 27 on the surface 23 a of the coat layer 23 is 30% or more and 60% or less, the charge amount of the toner is maintained within an appropriate range even when continuous printing is performed. It will be easier. Therefore, even when continuous printing is performed, the fluctuation of the image density can be further suppressed.

The hole area ratio of the recessed part 27 in the surface 23a of the coating layer 23 is calculated | required by the following formula. The total area of the opening surface of the recess 27 and the surface area of the coating layer 23 in the following formula are measured according to the following method. Here, the surface area of the coating layer 23 means the surface area of the coating layer 23 when assuming that the recess 27 is not formed. Specifically, the recess 27 is formed on the surface of the coating layer 23 It means the sum of the area of the non-portion and the total area of the opening surface of the recess 27.
(The opening ratio of the recess 27 in the surface 23 a of the coating layer 23) = (total area of the opening surface of the recess 27) / (surface area of the coating layer 23) × 100

  For example, the entire surface of the carrier particle 20 is observed using a field emission scanning electron microscope (FE-SEM, for example, “JSM-7600F” manufactured by JEOL Ltd.). The obtained image is analyzed using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). Then, the surface area of the coat layer 23 is calculated. Next, with respect to all the openings of the recess 27 detected by image analysis, the peripheral edge of the opening of each recess 27 is drawn using a pen tool, and the inside of the outline is filled. Calculate the sum of the projected area of the part filled with the pen tool (the part surrounded by the outline). The total of the calculated projected areas is taken as the total area of the opening surface of the recess 27 of one carrier particle. Such calculation of the total area of the opening surface of the recess 27 is performed on a plurality of carrier particles 20, and an average value of the total area of the opening surface of the recess 27 of the plurality of carrier particles 20 (measurement object) is determined. The average value of the total area of the opening surface of the recess 27 obtained in this manner is taken as the “total area of the opening surface of the recess 27”.

Preferably, the diameter r ₁ of the first resin particles 13 is 50nm or more 200nm or less. If the diameter r ₁ of the first resin particles 13 is 50 nm or more, the flowability of the toner particles 10 can be enhanced. Thereby, an image with high image density can be formed. The diameter r ₁ of the first resin particles 13 is equal to 200nm or less, it is likely to occur triboelectric charging of the toner and the carrier. As a result, the charge amount of the toner is more easily maintained within the appropriate range, so that the fluctuation of the image density can be further suppressed. The configuration of the two-component developer according to the present embodiment has been described above with reference to FIGS. 1 to 3.

[Configuration of Carrier According to this Embodiment]
The carrier according to the present embodiment includes a plurality of carrier particles including a carrier core and a coat layer covering the surface of the carrier core. The coat layer contains a resin. A plurality of concave portions are formed on the surface of the coating layer, and the opening diameter of the concave portions is 50 nm or more and 600 nm or less. As a result, it is possible to provide a two-component developer capable of maintaining the charge amount of the toner within an appropriate range even when continuous printing is performed.

  Hereinafter, an example of the carrier according to the present embodiment will be described with reference to FIGS. 1 to 3. The carrier includes a plurality of carrier particles 20 including the carrier core 21 and the coat layer 23 covering the surface 21 a of the carrier core 21. The coat layer 23 contains a resin (the second resin described above). A plurality of recesses 27 are formed on the surface 23 a of the coating layer 23, and the opening diameter R of the recesses 27 is 50 nm or more and 600 nm or less.

In the carrier particle 20, the opening diameter R of the recess 27 is 50 nm or more and 600 nm or less. In the two-component developer including the toner according to the embodiment and the toner including the resin particle having a diameter of 50 nm to 200 nm (for example, the first resin particle 13 shown in FIG. 1) as an external additive, the opening diameter of the recess 27 R is 1 to 3 times the diameter of the resin particles contained in the external additive of the toner (for example, the diameter r ₁ of the first resin particles 13 shown in FIG. ₁ ). As a result, it is possible to provide a two-component developer capable of maintaining the charge amount of the toner within an appropriate range even when continuous printing is performed.

  As mentioned above, it is preferable that the hole area ratio of the recessed part 27 in the surface 23a of the coating layer 23 is 30% or more and 60% or less. In a two-component developer including such a carrier, the charge amount of the toner is easily maintained within an appropriate range even when continuous printing is performed. Therefore, even when continuous printing is performed, the fluctuation of the image density can be further suppressed. The configuration of the carrier according to the present embodiment has been described above with reference to FIGS. 1 to 3.

[Production of Two-Component Developer According to this Embodiment]
The method of manufacturing a two-component developer according to the present embodiment includes a toner manufacturing process, a carrier manufacturing process, and a mixing process of mixing the electrostatic latent image developing toner and the electrostatic latent image developing carrier. . The manufacturing process of the electrostatic latent image developing toner includes a process of manufacturing toner particles including toner base particles and an external additive externally added to the surface of the toner base particles. The manufacturing process of the carrier for electrostatic latent image development includes a coating step of covering the surface of the carrier core with a coating layer including a surface layer, and a treatment step of treating the carrier core whose surface is covered with the coating layer with a solvent. The external additive contains a plurality of first resin particles containing a first resin. The surface layer is located on the outermost side in the radial direction of the carrier core in the coating layer, and includes a second resin and a third resin particle containing a third resin. The third resin particles have a diameter of 1 to 3 times the diameter of the first resin particles. In the treatment step, the third resin particles exposed on the surface of the coating layer are selectively dissolved.

  In the method of manufacturing a two-component developer according to the present embodiment, the third resin particles exposed on the surface of the coat layer are dissolved in the solvent to form a recess on the surface of the coat layer. Therefore, in the manufactured two-component developer, a plurality of recesses having an opening diameter of 1 to 3 times the diameter of the first resin particles are formed on the surface of the coating layer. Thereby, in the manufactured two-component developer, the charge amount of the toner can be maintained within an appropriate range even when continuous printing is performed. Hereinafter, an example of a method of manufacturing the two-component developer according to the present embodiment will be described.

[Manufacture of toner]
The toner is manufactured, for example, by the following method. The method of producing the toner may be arbitrarily changed according to the configuration or characteristics of the toner required. In order to produce the toner efficiently, it is preferable to simultaneously form a large number of toner particles.

(Production of toner mother particles)
An example of a method of producing toner base particles is an aggregation method or a grinding method. The grinding method can often produce toner base particles more easily than the aggregation method. Hereinafter, the production process of the toner base particles will be described by taking the pulverizing method as an example.

  The process for producing toner mother particles includes a kneading process. The process of producing toner mother particles may further include one or both of a grinding process and a classification process, as required.

  In the kneading step, the binder resin and the colorant are kneaded using a kneader. As a kneader, for example, a single screw extruder, a twin screw extruder, a roll mill or an open roll kneader can be used. In addition, at least one of a magnetic powder, a release agent and a charge control agent may be mixed with the binder resin and the colorant.

  In the pulverizing step, the kneaded material obtained in the kneading step is pulverized to obtain a pulverized material. In the classification step, the pulverized material obtained in the grinding step is classified to obtain toner base particles (for example, toner base particles 11 shown in FIG. 1).

(External attachment)
In the external addition step, the toner base particles and the external additive are mixed using a mixer. The external additive contains a plurality of first resin particles (for example, the first resin particles 13 shown in FIG. 1) containing the first resin.

  The mixing conditions are preferably set to conditions in which the external additive is not completely buried in the toner base particles. The external additive is physically bonded to the surface of the toner matrix particles by mixing the toner matrix particles with the external additive. As a result, a toner including a plurality of toner particles (for example, toner particles 10 shown in FIG. 1) is obtained.

(External addition: first resin particles)
The diameter of the first resin particles (for example, the diameter r ₁ of the first resin particles 13 shown in FIG. ₁ ) contained in the external additive is preferably 50 nm or more and 200 nm or less. When the diameter of the first resin particles is 50 nm or more, it is possible to manufacture a toner including toner particles excellent in fluidity. In addition, if the diameter of the first resin particles is 200 nm or less, it is possible to manufacture a toner that is likely to be frictionally charged with the carrier. Thus, it is possible to manufacture a toner capable of maintaining the charge amount within an appropriate range.

  The addition amount of the first resin particles is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. Thereby, it is possible to manufacture a toner including toner particles excellent in fluidity and heat resistant storage stability. Further, it is possible to manufacture a toner including toner particles with reduced adhesion to the developing roller, the photosensitive member and the transfer belt.

  The first resin contained in the first resin particles is preferably, for example, an acrylic resin, a styrene resin, or a styrene-acrylic acid resin.

  An acrylic resin is a polymer of an acrylic acid type monomer. The acrylic resin may be a homopolymer of one type of acrylic acid-based monomer, or may be a polymer of two or more types of acrylic acid-based monomers.

  Preferred examples of the acrylic acid-based monomer include (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Preferred examples of (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, (meth) acrylic Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Preferred examples of (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylic acid, 3-hydroxypropyl (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, or (meth) acrylic The acid 4-hydroxybutyl is mentioned.

  The styrene resin is a polymer of a styrene-based monomer. The styrene resin may be a homopolymer of one styrenic monomer, or may be a polymer of two or more styrenic monomers.

  Preferred examples of the styrenic monomer include styrene, alkylstyrene (more specifically, α-methylstyrene, p-ethylstyrene or 4-tert-butylstyrene), p-hydroxystyrene, m-hydroxystyrene, And vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene or p-chlorostyrene.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. As a styrene-type monomer used in order to synthesize | combine a styrene- acrylic acid-type resin, the said styrene-type monomer can be used conveniently. Moreover, as said acrylic acid type monomer used in order to synthesize | combine styrene-acrylic acid type resin, the said acrylic acid type monomer can be used suitably.

[Manufacturing of the carrier according to the present embodiment]
The carrier is manufactured, for example, by the following method. In addition, the manufacturing method of a carrier may be arbitrarily changed according to the structure or the characteristic of a required carrier. In order to efficiently produce the carrier, it is preferable to simultaneously form a large number of carrier particles. Hereinafter, an example of the manufacturing method of a carrier is shown using FIG.4 (a)-(c). FIG. 4A to FIG. 4C are diagrams showing, in the order of steps, an example of the method of manufacturing the carrier according to the present embodiment.

[An example of a method of manufacturing a carrier: FIGS. 4A to 4C]
(Coating process)
In the coating step, as shown in FIG. 4A, the surface 21 a of the carrier core 21 is covered with the coating layer 231 including the surface layer 232.

(Coating process: Preparation of surface coating solution)
Specifically, first, a surface layer coating solution containing the second resin and the third resin particles 271 is prepared. By dissolving the second resin in the surface layer solvent and dispersing the third resin particles 271, a surface layer coating solution can be prepared. As the surface layer solvent, for example, one or more selected from the group consisting of methyl ethyl ketone and tetrahydrofuran can be used.

(Coating process: second resin)
The second resin is preferably an insulating resin, and may be a thermoplastic resin or a thermosetting resin as long as it has an insulating property. The thermosetting resin that can be used as the second resin also includes a resin that has a thermosetting property as a result of the curing agent being added to the thermoplastic resin and being cured. Hereinafter, the specific example of 2nd resin is shown. Two or more of the resins shown below can be mixed and used as the second resin.

  Examples of thermoplastic resins usable as the second resin include polystyrene resins, acrylic acid resins (more specifically, polymethyl methacrylate), styrene-acrylic acid resins, styrene-butadiene copolymers, and ethylene-acetic acid. Vinyl copolymer, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin (including perfluorocarbon resin exhibiting solvent solubility), vinyl resin (more specifically, vinyl chloride resin, vinyl acetate resin, polyvinyl alcohol resin, Vinyl acetal resin or polyvinyl pyrrolidone), petroleum resin, cellulose, cellulose derivative (more specifically, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose or hydroxypropyl cellulose), novolak resin, low molecular weight Polyethylene resin, saturated alkyl polyester resin, polyethylene terephthalate (more specifically, polyethylene terephthalate, polybutylene terephthalate, polyarylate), polyamide resin, polyacetal resin, polycarbonate resin, polyether sulfone resin, polysulfone resin, polyphenylene sulfide resin, or It is preferable that it is a polyether ketone resin.

  The thermosetting resin usable as the second resin is, for example, a phenolic resin, a modified phenolic resin, a maleic resin, an alkyd resin, an epoxy resin, an unsaturated resin obtained by the polycondensation of maleic anhydride and terephthalic acid with a polyhydric alcohol. Polyester resin, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide resin, polyamide imide resin, polyether imide resin, or It is preferable that it is a polyurethane resin. The thermosetting resin which can be used as the second resin is more preferably a silicone resin, specifically a methyl silicone resin.

(Coating process: 3rd resin particle)
Third diameter r ₃ of the resin particles 271, 1 times or more the diameter of the first resin particles contained in the external additive of the toner produced by the aforementioned (e.g., diameter r ₁ of the first resin particles 13 shown in FIG. 1) It is 3 times or less, preferably 50 nm or more and 600 nm or less.

  The third resin contained in the third resin particles 271 is preferably, for example, an acrylic resin, a styrene resin, or a styrene-acrylic acid resin.

  An acrylic resin is a polymer of an acrylic acid type monomer. The acrylic resin may be a homopolymer of one type of acrylic acid-based monomer, or may be a polymer of two or more types of acrylic acid-based monomers. As an acrylic acid type monomer used in order to synthesize an acrylic resin, the acrylic acid type monomer as described in the above (external addition: first resin particle) can be suitably used.

  The styrene resin is a polymer of a styrene-based monomer. The styrene resin may be a homopolymer of one styrenic monomer, or may be a polymer of two or more styrenic monomers. As a styrene-type monomer used in order to synthesize | combine a styrene resin, the styrene-type monomer as described in the above (external addition: 1st resin particle) can be used suitably.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. As a styrene-type monomer used in order to synthesize | combine styrene-acrylic acid-type resin, the styrene-type monomer as described in said (external addition: 1st resin particle) can be used suitably. Moreover, as an acrylic acid type monomer used in order to synthesize | combine styrene-acrylic acid type resin, the acrylic acid type monomer as described in said (external addition: 1st resin particle) can be used suitably.

(Coating process: formation of surface layer)
Next, the surface layer 232 is formed on the surface 21 a of the carrier core 21 using the surface layer coating solution. The carrier core 21 may be dipped in the surface layer coating solution, or the surface layer coating solution may be sprayed on the carrier core 21 in the fluidized bed. At this time, the surface 21 a of the carrier core 21 is coated with a surface layer coating solution so that the thickness of the surface layer 232 formed by heat treatment becomes larger than the diameter of the first resin particles contained in the external additive of toner. Is preferred.

  While flowing the carrier core 21 covered with the surface layer coating solution, heat treatment at a predetermined temperature (for example, a temperature selected from 200 ° C. to 300 ° C.) is performed for a predetermined time (eg, 30 minutes to 90 minutes) Time to be chosen from)). As a result, the surface layer coating solution is cured (resinized) to form the surface layer 232 covering the surface 21 a of the carrier core 21 (FIG. 4A).

  In the method of manufacturing the carrier shown in FIGS. 4A to 4C, the coat layer 231 having only the surface layer 232 is formed. Therefore, by forming the surface layer 232 covering the surface 21 a of the carrier core 21, the coat layer 231 covering the surface 21 a of the carrier core 21 is formed. The formed coat layer 231 includes the second resin and the third resin particles 271. Then, some of the third resin particles 271 are exposed from the surface 231 a of the coat layer 231.

(Processing process)
In the treatment step, as shown in FIG. 4B, the carrier core 21 whose surface 21a is covered with the coat layer 231 is washed with a solvent (hereinafter, referred to as a cleaning solvent). For example, the carrier core 21 whose surface 21a is covered with the coating layer 231 may be stirred in the cleaning solvent, or the cleaning solvent may be sprayed onto the carrier core 21 whose surface 21a is covered with the coating layer 231. Also good. Thus, the cleaning solvent comes in contact with the surface 231 a of the coating layer 231. Here, the cleaning solvent does not dissolve the second resin, but dissolves the third resin particles 271. Therefore, the third resin particles 271 exposed on the surface 23 a of the coat layer 23 are selectively dissolved, and the concave portions 27 are formed by the dissolution of the third resin particles 271. That is, a plurality of concave portions 27 are formed in the surface 23 a of the coat layer 23 formed to cover the surface 21 a of the carrier core 21 (FIG. 4C). As a result, a carrier including a plurality of carrier particles 20 is obtained.

Third diameter r ₃ of the resin particles 271, 1 times or more the diameter of the first resin particles contained in the external additive of the toner produced by the aforementioned (e.g., diameter r ₁ of the first resin particles 13 shown in FIG. 1) Less than three times. Therefore, the opening diameter R of the recess 27 formed by the dissolution of the third resin particle 271 is 1 to 3 times the diameter of the first resin particle. Further, the thickness of the coat layer 23 is larger than the diameter of the first resin particle. From these facts, in the two-component developer containing carrier particles 20 manufactured according to the method shown in FIGS. 4A to 4C, the charge amount of the toner is appropriate even when continuous printing is performed. Can be maintained within a certain range.

When the diameter r ₃ of the third resin particles 271 is 50nm or more 600nm or less, opening diameter R of the recess 27 formed by the dissolution of the third resin particles 271 becomes 50nm or 600nm or less. Therefore, if the diameter of the first resin particle included in the external additive of the toner manufactured above is 50 nm or more and 200 nm or less, the opening diameter R of the recess 27 formed by the dissolution of the third resin particle 271 is the first It is 1 to 3 times the diameter of the resin particle. Therefore, in a two-component developer including such a combination of toner and carrier, the charge amount of toner in continuous printing can be maintained within an appropriate range.

  The cleaning solvent does not dissolve the second resin, but dissolves the third resin particles 271. As such cleaning solvents, the following solvents can be used. When the second resin is a methyl silicone resin and the third resin particles 271 are acrylic resin particles, the washing solvent is preferably tetrahydrofuran.

  Since the third resin particles 271 are dissolved by contact with the cleaning solvent, the third resin particles 271 present inside the coat layer 23 are unlikely to be dissolved. Therefore, as shown in FIG. 4C, the third resin particles 271 may remain inside the formed coat layer 23.

  The carrier according to the present embodiment can also be manufactured according to the method shown in FIGS. 5 (a) to 5 (d). FIG. 5A to FIG. 5D are diagrams showing, in the order of steps, another example of the method of manufacturing a carrier according to the present embodiment. The method of manufacturing the carrier shown in FIGS. 5 (a) to 5 (d) is the same as the method of manufacturing the carrier shown in FIGS. 4 (a) to 4 (c) except that the surface layer is formed after forming the underlayer. It is. In the following, differences from the carrier manufacturing method shown in FIGS. 4A to 4C will be mainly shown.

[Another Example of a Method of Manufacturing a Carrier: FIGS. 5 (a) to 5 (d)]
(Coating process)
In the coating step, as shown in FIG. 5A, after the surface 21a of the carrier core 21 is covered with the underlayer 230, the surface 230a of the underlayer 230 is covered with the surface layer 232.

(Coating step: preparation of coating solution for underlayer)
Specifically, first, a coating solution for the underlayer containing the second resin is prepared. The base layer coating solution can be prepared by dissolving the second resin in the base layer solvent. As the underlayer solvent, for example, one or more selected from the group consisting of methyl ethyl ketone and tetrahydrofuran can be used.

(Coating process: formation of underlayer)
Next, the underlayer 230 is formed on the surface 21 a of the carrier core 21 using the underlayer coating solution. The carrier core 21 may be immersed in the undercoat layer coating solution, or the undercoat layer coating solution may be sprayed on the carrier core 21 in the fluidized bed. At this time, it is preferable to coat the surface 21 a of the carrier core 21 with a coating solution for the underlayer so that the thickness of the underlayer 230 formed by heat treatment is 200 nm or more and 500 nm or less.

  A heat treatment at a predetermined temperature (for example, a temperature selected from 200 ° C. or more and 300 ° C. or less) for a predetermined time (for example, 30 minutes or more and 90 minutes) while flowing the carrier core 21 in a state covered with the underlayer coating liquid. Time selected from the following). As a result, the underlayer coating liquid is cured (made into resin) to form the underlayer 230 covering the surface 21 a of the carrier core 21 (FIG. 5A).

(Coating process: formation of surface layer)
Subsequently, the surface layer coating solution is prepared according to the method described above (coating step: preparation of surface layer coating solution). The surface layer 232 is formed according to the method described above (coating step: formation of the surface layer) except that the surface layer 232 is formed on the surface 230 a of the foundation layer 230 using the obtained surface layer coating solution.

  In the method of manufacturing the carrier shown in FIGS. 5A to 5D, the surface layer 232 is formed after the base layer 230 is formed on the surface 21a of the carrier core 21. Therefore, as shown in FIG. 5B, the surface layer 232 including the third resin particle 271 is positioned at the outermost side in the radial direction of the carrier core 21 in the coat layer 231.

  In the subsequent processing step (step shown in FIG. 5C), the cleaning solvent contacts the surface 231 a of the coating layer 231. Therefore, the third resin particles 271 exposed on the surface 231 a of the coat layer 231 are selectively dissolved, and the concave portions 27 are formed by the dissolution of the third resin particles 271. That is, a plurality of concave portions 27 are formed in the surface 231 a of the coat layer 231 formed to cover the surface 21 a of the carrier core 21 (FIG. 5 (d)). As a result, a carrier including a plurality of carrier particles 20 is obtained.

  When the carrier according to the present embodiment is manufactured according to the method shown in FIGS. 5A to 5D, a layer not containing the third resin particle 271 between the surface 21a of the carrier core 21 and the surface layer 232 (that is, the lower part). The formation 230) is formed (FIG. 5 (b)). Thereby, the depth D of the concave portion 27 formed by the dissolution of the third resin particle 271 is surely smaller than the thickness T of the coating layer 23. Therefore, in the manufactured carrier particle 20, the surface 21a of the carrier core 21 can be further prevented from being exposed.

  In the method of manufacturing the carrier shown in FIGS. 5 (a) to 5 (d), the undercoat layer coating solution and the surface layer coating solution are sequentially applied to the surface 21a of the carrier core 21, and then the undercoat layer coating solution and the surface layer are heated. It may be simultaneously cured with the coating solution. In the above, the manufacturing method of the carrier concerning this embodiment was explained using Drawing 4 (a)-(c) and Drawing 5 (a)-(d).

[Mixing of toner and carrier]
The toner particles and carrier particles are mixed and stirred. At this time, the toner particles are preferably added in an amount of 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of carrier particles. Also, mixing and stirring of the toner particles and the carrier particles can be performed using a mixer (for example, a ball mill, a Nauta mixer, a rocking mixer, etc.). Thus, the two-component developer according to the present embodiment is obtained.

[Example of Configuration of Carrier Particles and Toner Particles]
[Toner particle]
As described above, the toner particles contained in the toner include toner base particles and an external additive externally added to the surface of the toner base particles. The toner may contain toner particles consisting only of toner base particles. Hereinafter, after describing the external additive, toner base particles will be described.

(External additive)
The external additive contains the above-mentioned first resin particles. The content of the first resin particles in the toner particles is preferably 0.5 parts by mass to 10 parts by mass with respect to 100 parts by mass of the toner base particles. This improves the flowability of the toner particles and the heat resistant storage stability of the toner particles. Further, at the time of image formation, the adhesion of toner particles to the developing roller, the photosensitive member and the transfer belt can be reduced. Here, the content of the first resin particles in the toner particles means the total amount thereof when using a plurality of types of first resin particles.

  The external additive may further contain inorganic particles. The inorganic particles are preferably, for example, silica particles or metal oxide particles. As the metal oxide particles, for example, alumina particles, titanium oxide particles, magnesium oxide particles, zinc oxide particles, strontium titanate particles, or barium titanate particles can be used.

(Toner mother particles)
The toner particles may be toner particles having no shell layer (hereinafter referred to as non-capsulated toner particles) or may be toner particles provided with a shell layer (hereinafter referred to as capsule toner particles) . By forming a shell layer on the surface of non-externally added non-capsulated toner particles (toner core), capsule toner particles can be produced. The shell layer may consist essentially of the thermosetting resin, may consist essentially of the thermoplastic resin, or may contain both the thermoplastic resin and the thermosetting resin. .

  Non-encapsulated toner particles can be made, for example, by grinding or agglomeration methods. These methods facilitate the good dispersion of the internal additive in the binder resin of non-capsulated toner particles.

  In one example of the grinding method, first, a binder resin, a colorant, a charge control agent, and a release agent are mixed. Subsequently, the obtained mixture is melt-kneaded using a melt-kneading apparatus (for example, a single-screw or twin-screw extruder). Subsequently, the obtained melt-kneaded product is crushed and classified. Thereby, toner mother particles are obtained. When the pulverizing method is used, toner base particles can often be produced more easily than when the aggregating method is used.

  In one example of the aggregation method, first, in the aqueous medium containing the fine particles of each of the binder resin, the releasing agent, and the colorant, the fine particles are coagulated to a desired particle size. Thereby, aggregated particles including the binder resin, the release agent, and the colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. Thereby, toner base particles having a desired particle diameter can be obtained.

  When producing encapsulated toner particles, the method of forming the shell layer is optional. For example, the shell layer may be formed by any method of in-situ polymerization, in-liquid curing coating method, and coacervation method.

(Non-capsulated toner particles)
The toner base particles contain a binder resin. Further, the toner base particles may contain internal additives (for example, a colorant, a release agent, a charge control agent, and a magnetic powder).

(Binder resin)
In the toner base particles, generally, the binder resin occupies most (for example, 85% by mass or more) of the components. For this reason, it is considered that the properties of the binder resin greatly affect the overall properties of the toner base particles. In order to achieve both heat resistant storage stability and low temperature fixability of the toner, the toner base particles preferably contain a thermoplastic resin as a binder resin, and at least one of a styrene-acrylic acid resin and a polyester resin is used. It is particularly preferable to contain.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. As a styrene-type monomer used in order to synthesize | combine styrene-acrylic acid-type resin, the styrene-type monomer as described in said (external addition: 1st resin particle) can be used suitably. As an acrylic acid type monomer used in order to synthesize a styrene-acrylic acid type resin, the acrylic acid type monomer described in the above (external addition: first resin particle) can be suitably used.

  The polyester resin is obtained by condensation polymerization of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. As an alcohol for synthesizing a polyester resin, for example, a dihydric alcohol (more specifically, a diol or bisphenol) or a trihydric or higher alcohol as shown below can be suitably used. As a carboxylic acid for synthesizing a polyester resin, for example, a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below can be suitably used.

  Preferred examples of the diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4 Diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol.

  Preferable examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferred examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, and 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane or 1,3,5- Trihydroxymethylbenzene is mentioned.

  Preferred examples of the divalent carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid , Succinic acid, alkylsuccinic acid (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, or isododecylsuccinic acid), or alkenylsuccinic acid (more specifically) And n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, or isododecenylsuccinic acid).

  Preferred examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylene carboxyl) Methane, 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid, or Empol trimer acid can be mentioned.

(Colorant)
The toner mother particles may contain a colorant. As the colorant, known pigments or dyes may be used in accordance with the color of the toner. In order to form a high quality image using toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner base particles may contain a black colorant. Examples of black colorants include carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner matrix particles may contain color colorants such as yellow colorants, magenta colorants, or cyan colorants.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of yellow colorants include C.I. I. Pigment yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 or 194), Naphthol Yellow S, Hansa Yellow G or C.I. I. Bat yellow can be suitably used.

  The magenta colorant is selected, for example, from the group consisting of condensation azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be suitably used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 or 66), phthalocyanine blue, C.I. I. Bat blue or C.I. I. Acid blue can be suitably used.

(Release agent)
The toner mother particles may contain a release agent. The release agent is used, for example, for the purpose of improving the fixing property or the offset resistance of the toner. In order to improve the fixing property or the offset resistance of the toner, the amount of the releasing agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  As a mold release agent, for example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; vegetable waxes such as candelilla wax, carnauba wax, wax wax, jojoba wax, or rice wax; animal nature such as bees wax, lanolin or wax wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanic acid ester wax or castor wax; fatty acids such as deacidified carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or two or more types of release agents may be used in combination.

(Charge control agent)
The toner base particles may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charge stability or charge rise characteristics of the toner. The charge rising characteristic of the toner is an indicator of whether or not the toner can be charged to a predetermined charge level in a short time.

  By incorporating a positively chargeable charge control agent (more specifically, pyridine, nigrosine, or quaternary ammonium salt) in the toner matrix particles, the cationicity of the toner matrix particles can be enhanced. However, when sufficient chargeability is ensured in the toner, the toner base particles do not need to contain a charge control agent.

(Magnetic powder)
The toner base particles may contain magnetic powder. As a material of the magnetic powder, for example, ferromagnetic metal (more specifically, iron, cobalt, nickel, or an alloy containing one or more of these metals), ferromagnetic metal oxide (more specifically, ferrite) And magnetite or chromium dioxide) or a material subjected to a ferromagnetic treatment (more specifically, a carbon material to which ferromagnetism is imparted by heat treatment) can be suitably used. In order to suppress the elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to use surface-treated magnetic particles as the magnetic powder. One type of magnetic powder may be used alone, or two or more types of magnetic powder may be used in combination.

Carrier particle
As described above, the carrier particles contained in the carrier include the carrier core and the coat layer covering the surface of the carrier core. The carrier particles charge the toner particles by friction.

(Carrier core)
The carrier core preferably contains a magnetic material. The carrier core may be particles of a magnetic material, or particles of the magnetic material may be dispersed in a binder resin of the carrier core. Examples of the magnetic material contained in the carrier core include ferromagnetic metals (more specifically, iron, cobalt, nickel, or metals containing one or more of these metals), ferromagnetic metal oxides (more specifically) And ferrite or magnetite). The metal containing one or more of iron, cobalt and nickel includes, for example, one or more of iron, cobalt and nickel, copper, zinc, antimony, aluminum, lead, tin, bismuth, beryllium, Alloys or mixtures with one or more of manganese, magnesium, selenium, tungsten, zirconium and vanadium. As another example of the magnetic material contained in the carrier core, the above-mentioned ferromagnetic metal oxide, iron oxide, metal oxide of titanium oxide or magnesium oxide, nitride of chromium nitride or vanadium nitride, silicon carbide or tungsten carbide And mixtures with one or more of the following carbides.

  The magnetic material contained in the carrier core is preferably ferrite or magnetite. Preferred examples of the ferrite include magnetite (spinel ferrite), barium ferrite, Mn ferrite, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, Cu-Zn ferrite, or Mn -Mg-Sr ferrite is mentioned.

  As a material of each carrier core, one type of magnetic material may be used alone, or two or more types of magnetic materials may be used in combination. A commercial item may be used as a carrier core. Also, the magnetic material may be crushed and fired to make a carrier core by itself. In the preparation of the carrier core, the saturation magnetization of the carrier can be adjusted by changing the amount of the magnetic material added (in particular, the proportion of the ferromagnetic material). In the preparation of the carrier core, the degree of circularity of the carrier can be adjusted by changing the baking temperature.

  More preferably, in the carrier according to the present embodiment, the carrier core is a ferrite particle. Ferrite particles tend to have sufficient magnetism for imaging. In addition, ferrite particles produced by a general production method do not become true spheres and tend to have appropriate unevenness on the surface. Specifically, the arithmetic mean roughness of the surface of the ferrite particles (specifically, the arithmetic mean roughness Ra defined by JIS (Japanese Industrial Standards) B0601-2013) tends to be 0.3 μm or more and 2.0 μm or less.

The volume median diameter (D ₅₀ ) of the carrier core is preferably 30 μm or more and 100 μm or less. Thereby, better developability can be obtained. The volume median diameter (D ₅₀ ) of the carrier core is a value measured using a laser diffraction / scattering particle size distribution measuring apparatus (“LA-700” manufactured by Horiba, Ltd.).

(Coat layer)
The coat layer contains the second resin described above. The second resin is preferably contained in an amount of 0.3 to 5 parts by mass with respect to 100 parts by mass of the carrier core in the coating layer. If the second resin is contained in an amount of 0.3 parts by mass or more with respect to 100 parts by mass of the carrier core in the coat layer, occurrence of carrier development can be prevented. In addition, if the second resin is contained in an amount of 5 parts by mass or less based on 100 parts by mass of the carrier core in the coat layer, occurrence of charge up can be prevented, so that good developability can be obtained. Here, carrier development means a phenomenon in which the carrier also moves to the toner carrier together with the toner. Further, charge up means a phenomenon in which toner is positively charged excessively.

  The coat layer preferably further contains an additive having a polarity opposite to that of the second resin. For example, when a silicone resin is used as the second resin in a carrier for positively chargeable toner, the coating layer preferably contains an aminosilane coupling agent as an additive.

  Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to the examples shown below.

  Two-component developers D-1 to D-11 shown in Table 1 were produced according to the method shown below.

In Table 1, "Developer" means a two-component developer. The “diameter r ₁ ” means the diameter of the acrylic resin particles contained in the external additive. "Content" means the content of acrylic resin particles (described as resin particles in Table 1) relative to 100 parts by mass of a carrier core, and the unit is part by mass. "Treatment" means that carrier particles in which a coating layer is formed on the surface of a carrier core are washed with tetrahydrofuran.

  Hereinafter, the method for producing acrylic resin particles used in this example, the method for producing two-component developers D-1 to D-11, the evaluation method, and the evaluation results will be described in order. In addition, in the evaluation which an error produces, the measurement value of a considerable number which an error becomes small enough was obtained, and the arithmetic mean of the obtained measurement value was made into the evaluation value.

[Production of acrylic resin particles]
Potassium persulfate (Nacalai Tesque, Inc.) in a solution containing 100 parts by mass of methyl methacrylate (Nacalai Tesque, Inc. “Methyl methacrylate (monomer)”, product code: 22725-95) and 300 parts by mass of distilled water , Product code: 28717-25, polymerization initiator), sodium thiosulfate (manufactured by Nacalai Tesque, Inc., Product code: 32008-85, redox type polymerization initiator), copper sulfate (manufactured by Nacalai Tesque, Inc. "copper sulfate (II) Pentahydrate ", product code: 09604-85, accelerator) was added. At this time, potassium persulfate was added such that the concentration of potassium persulfate in the solution became 3.0 × 10 ⁻⁵ mol / L. Further, sodium thiosulfate was added such that the concentration of sodium thiosulfate in the solution was X (described in Table 2) mol / L. Moreover, as the concentration of copper sulfate is 2.5 × 10- ⁵ mol / L in the solution, was added copper sulfate. The temperature of the solution was raised to 70 ° C., and reaction was performed at 70 ° C. for 2 hours under a nitrogen stream. After cooling, it was filtered and dried. Thus, acrylic resin particles having a diameter of Y (as described in Table 2) nm were obtained. The obtained acrylic resin particles were particles made of polymethyl methacrylate (PMMA).

  In addition, the diameter of the obtained acrylic resin particle was measured according to the method shown next. The cross section of the acrylic resin particle was observed using a scanning electron microscope (SEM). Fifty acrylic resin particles were randomly extracted from the obtained image. The length in the long axis direction of each of the 50 extracted acrylic resin particles was determined, and the average value of the determined lengths was used as the diameter of the acrylic resin particles (Y shown in Table 2).

  In Table 2, X means the concentration of sodium thiosulfate in a liquid containing 100 parts by mass of methyl methacrylate and 300 parts by mass of distilled water. Y means the diameter of the obtained acrylic resin particle.

[Production of two-component developer]
[Production of Two-Component Developer D-1]
A two-component developer D-1 containing toner T-1 and carrier C-1 was produced according to the method described below.

[Preparation of Toner T-1]
(Preparation of toner base particles)
100 parts by mass of a polyester resin (“XPE 258” manufactured by Mitsui Chemicals, Inc., acid value: 5.6 mg KOH / g, melting point: 100 ° C.) using an FM mixer (“FM-10 B” manufactured by Japan Coke Industry Co., Ltd.) , 5 parts by mass of carnauba wax ("Kohoku Kato Wax Co., Ltd. special-purpose carnauba wax No. 1"), and 4 parts by mass of a colorant (copper phthalocyanine blue pigment (CIpigment Blue 15: 3) manufactured by Cabot "REGAL (registered trademark)" 330 R ′ ′) and 1 part by mass of quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Industry Co., Ltd.) were mixed.

The obtained mixture was melt-kneaded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.). After cooling the obtained kneaded material, it was pulverized using a pulverizer ("turbo mill" manufactured by Freund Turbo Co., Ltd.). The obtained pulverized material was classified using a classifier ("Elbow jet EJ-LABO type" manufactured by Nittetsu Mining Co., Ltd.). As a result, toner base particles having a volume median diameter (D ₅₀ ) of 6.8 μm were obtained.

(External attachment)
External addition was performed on the obtained toner base particles. Specifically, 100 parts by mass of toner base particles and 1 part by mass of hydrophobic silica particles (manufactured by Nippon Aerosil Co., Ltd. "AEROSIL (registered trademark) using an FM mixer (" FM-10B "manufactured by Japan Coke Industry Co., Ltd.) Content: dry silica particles surface-modified with trimethylsilyl and amino groups, number average primary particle diameter: about 12 nm, and 1 part by mass of acrylic resin particles (diameter r ₁ : 62 nm, Table 2) The acrylic resin particles P-2 described in the above were mixed (rotational speed: 3500 rpm, mixing time: 5 minutes). Thus, the external additives (hydrophobic silica particles and acrylic resin particles) were adhered to the surface of the toner base particles. As a result, Toner T-1 containing a large number of toner particles was obtained.

[Preparation of Carrier C-1]
(Preparation of career core)
Water was added to a mixture of 70 parts by mass of Fe ₂ O ₃ , 20 parts by mass of CuO, and 10 parts by mass of ZnO, and the mixture was pulverized using a wet ball mill for 2 hours. Polyvinyl alcohol was added to the obtained pulverized material (volume median diameter (D ₅₀ ): 1 μm or less). The resulting mixture was granulated and dried using a spray dryer. The obtained granulated product was calcined at 1000 ° C. for 5 hours. A carrier core (manganese ferrite carrier) having a volume median diameter of 40 μm and a saturation magnetization of 65 Am ² / kg at an applied magnetic field of 3000 (10 ³ / 4π · A / m) was obtained.

(coat)
Add 4 parts by mass of octylic acid (curing catalyst) to 100 parts by mass of a methyl silicone resin (a resin having a mass average molecular weight of 1.5 × 10 ⁴ measured by gel permeation chromatography (GPC)), A coating solution was obtained.

A coating solution and 0.5 parts by mass of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) were added to a fluid bed coating apparatus (manufactured by Freund Corporation) ) SFC-5 ′ ′) was sprayed onto 100 parts by mass of a carrier core while sending in 80 ° C. hot air. The amount of the coating solution added was such that the amount of methyl silicone resin was 3 parts by mass with respect to 100 parts by mass of the carrier core. As a result, the carrier core was coated with the uncured organic layer (fluidized layer). The carrier particles coated on the surface of the carrier core with the uncured organic layer (fluidized layer) were heated at 260 ° C. for 3 hours using a dryer. This cured the fluidised bed.

(Washing)
The carrier particles in which the hardened layer was formed on the surface of the carrier core were washed with tetrahydrofuran (manufactured by Nacalai Tesque, Inc.). Specifically, carrier particles in which a hardened layer was formed on the surface of the carrier core were dispersed in tetrahydrofuran. As a result, acrylic resin particles exposed from the surface of the cured layer were dissolved in tetrahydrofuran, and a plurality of recesses were formed on the surface of the cured layer. That is, the surface of the carrier core was covered with the coating layer, and a recess (open hole diameter: 67 nm) was formed on the surface of the coating layer. The resulting particles were removed from tetrahydrofuran and dried. Thus, carrier C-1 containing a plurality of carrier particles was obtained.

[Mixing of Toner T-1 and Carrier C-1]
The toner T-1 and the carrier C-1 are mixed for 30 minutes using a powder mixer ("rocking mixer (registered trademark)" manufactured by Aichi Electric Co., Ltd., mixing method: container rotational rocking method), 2 A component developer was prepared. The toner T-1 and the carrier C-1 were mixed at such a mass ratio that the ratio of the toner in the two-component developer was 8% by mass. Thus, a two-component developer D-1 was obtained.

[Production of Two-Component Developer D-2]
The two-component developer D-1 was prepared except that toner T-2 prepared in the following (preparation of toner T-2) and carrier C-2 prepared in the following (preparation of carrier C-2) were mixed. A two-component developer D-2 was produced according to the same method as for production.

(Preparation of Toner T-2)
Acrylic resin particles (diameter r ₁ : 153 nm, acrylic resin particles P-4 described in Table 2) were used instead of acrylic resin particles (diameter r ₁ : 62 nm, acrylic resin particles P-2 described in Table 2) Toner T-2 was prepared according to the same method as preparation of toner T-1 except for the following.

(Preparation of career C-2)
Acrylic resin particles (diameter r ₃ : 162 nm, acrylic resin particles P-5 described in Table 2) were used instead of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) Carrier C-2 was prepared according to the same method as preparation of carrier C-1 except for the following.

[Production of Two-Component Developer D-3]
A two-component developer D-3 was produced in the same manner as the production of the two-component developer D-1 except that the toner T-1 and the carrier C-2 were mixed.

[Production of Two-Component Developer D-4]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-1 and the carrier C-3 prepared in the following (preparation of the carrier C-3) are mixed D-4 was manufactured.

(Preparation of carrier C-3)
Carrier C-1 except that the addition amount of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) relative to 100 parts by mass of a carrier core was changed to 0.2 parts by mass The carrier C-3 was prepared according to the same method as preparation of.

[Production of Two-Component Developer D-5]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-1 and the carrier C-4 prepared in the following (preparation of the carrier C-4) are mixed D-5 was produced.

(Preparation of carrier C-4)
Carrier C-1 except that the addition amount of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) relative to 100 parts by mass of a carrier core was changed to 0.4 parts by mass The carrier C-4 was prepared according to the same method as preparation of.

[Production of Two-Component Developer D-6]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-1 and the carrier C-5 prepared in the following (preparation of the carrier C-5) are mixed D-6 was manufactured.

(Preparation of carrier C-5)
Carrier C-1 except that the addition amount of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) relative to 100 parts by mass of a carrier core was changed to 0.6 parts by mass The carrier C-5 was prepared according to the same method as preparation of.

[Production of Two-Component Developer D-7]
Two-component developer according to the same method as in the preparation of the two-component developer D-1 except that the toner T-1 and the carrier C-6 prepared in the following (preparation of the carrier C-6) are mixed D-7 was manufactured.

(Preparation of carrier C-6)
Carrier C-1 except that the addition amount of acrylic resin particles (diameter r ₃ : 71 nm, acrylic resin particles P-3 described in Table 2) relative to 100 parts by mass of a carrier core was changed to 0.8 parts by mass The carrier C-6 was prepared according to the same method as the preparation of.

[Production of Two-Component Developer D-8]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-3 prepared in the following (preparation of the toner T-3) and the carrier C-1 are mixed D-8 was produced.

(Preparation of Toner T-3)
Acrylic resin particles (diameter r ₁ : 41 nm, acrylic resin particles P-1 described in Table 2) were used instead of acrylic resin particles (diameter r ₁ : 62 nm, acrylic resin particles P-2 described in Table 2) Toner T-3 was prepared according to the same method as preparation of toner T-1 except for the following.

[Production of Two-Component Developer D-9]
Two-component developer according to the same method as the preparation of the two-component developer D-1 except that the toner T-4 prepared in the following (preparation of the toner T-4) and the carrier C-2 are mixed D-9 was produced.

(Preparation of Toner T-4)
Acrylic resin particles: Instead acrylic resin particles (diameter r ₁ 62 nm, acrylic resin particles P-2 according to Table 2) were used: (diameter r ₁ 250 nm, acrylic resin particles P-6 in Table 2) Toner T-4 was prepared according to the same method as preparation of toner T-1 except for the following.

[Production of Two-Component Developer D-10]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-1 and the carrier C-7 prepared in the following (preparation of the carrier C-7) are mixed D-10 was produced.

(Preparation of Carrier C-7)
Carrier C-7 was prepared according to the same method as preparation of carrier C-1, except that acrylic resin particles were not sprayed onto the carrier core.

[Production of Two-Component Developer D-11]
Two-component developer according to the same method as in the preparation of the two-component developer D-1, except that the toner T-1 and the carrier C-8 prepared in the following (preparation of the carrier C-8) are mixed D-11 was produced.

(Preparation of carrier C-8)
Acrylic resin particles: Instead acrylic resin particles (diameter r ₃ 71 nm, acrylic resin particles P-3 described in Table 2) were used: (diameter r ₃ 250 nm, acrylic resin particles P-6 in Table 2) Carrier C-8 was prepared according to the same method as preparation of carrier C-1 except for the following.

[Measurement of physical properties of carrier]
(Measurement of the open hole diameter R of the recess)
With respect to the carriers C-1 to C-8 obtained according to the above-described method, the opening diameter R of the recess was measured. First, the entire surface of the carrier particles was observed using a field emission scanning electron microscope (FE-SEM, “JSM-7600F” manufactured by Nippon Denshi Co., Ltd.). The obtained image was analyzed using image analysis software ("WinROOF" manufactured by Mitani Corporation). A plurality of recesses were detected by this image analysis. The circle equivalent diameter of each of the plurality of detected recesses was determined, and the average value thereof was taken as "the opening diameter R of the recess". The results are shown in Table 3.

(Measurement of open area ratio of recess on surface of coat layer)
The hole area ratio of the recessed part in the surface of a coating layer was computed using the following formula. The total area of the opening surface of the recess and the surface area of the coating layer in the following formula were measured according to the following method. The results are shown in Table 3.
(The opening ratio of the recess on the surface of the coating layer) = (total area of the opening surface of the recess) / (surface area of the coating layer) × 100

  The entire surface of the carrier particles was observed using a field emission scanning electron microscope (FE-SEM, “JSM-7600F” manufactured by Nippon Denshi Co., Ltd.). The obtained image was analyzed using image analysis software ("WinROOF" manufactured by Mitani Corporation). Then, the surface area of the coat layer was calculated.

  Next, for all the openings of the recess detected by image analysis, the periphery of the opening of each recess was drawn using a pen tool, and the inside of the outline was filled. The total of the projected area of the part filled with the pen tool (the part surrounded by the outline) was calculated. The total of the calculated projected areas was taken as the total area of the opening face of the recess of one carrier particle. The calculation of the total area of the opening surface of such a recessed part was performed with respect to several carrier particles, and the average value of the total area of the opening surface of the recessed part of several carrier particle (measurement object) was calculated | required. The average value of the total area of the opening surface of the recess obtained in this manner is taken as the “total area of the opening surface of the recess”.

(Measurement of thickness T of coat layer)
The thickness T of the coating layer was measured for the carriers C-1 to C-8 obtained according to the above-mentioned method. First, cross-sectional TEM photographs of carrier particles were taken using a transmission electron microscope (TEM, “H-7100 FA” manufactured by Hitachi High-Technologies Corporation). Next, cross-sectional TEM photographs of the obtained carrier particles were analyzed using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). Specifically, two straight lines perpendicular to each other at the approximate center of the cross section of the carrier particle were drawn. In each of the two straight lines, the length from the interface between the carrier core and the coat layer (corresponding to the surface of the carrier core) to the surface of the coat layer was measured. The average value of the four lengths measured in this manner was taken as the thickness of the coat layer provided on one carrier particle. The measurement of the thickness of such a coating layer was performed with respect to a plurality of carrier particles, and the average value of the thickness of the coating layer included in the plurality of carrier particles (measurement target) was determined. The average value of the thickness of the coating layer determined in this manner was taken as "the thickness T of the coating layer".

[Evaluation of two-component developer]
(Evaluation of toner charge amount)
The charge amount of the toner was evaluated using the two-component developers D-1 to D-11 obtained according to the method described above. First, the two-component developer obtained according to the above-described method was placed in a developing device of a color multifunction peripheral ("TASK alpha 5550 Ci" manufactured by KYOCERA Document Solutions Inc.). Also, the corresponding toner was placed in the toner container of the color multifunction peripheral. Thereafter, a sample image having a printing rate of 5% was printed on one recording medium. Thereafter, the two-component developer was taken out of the developing device. 0.10 ± 0.01 g of the removed two-component developer was placed in a measurement cell of a Q / m meter (“Model 210HS” manufactured by Trek Co.). Of the two-component developer contained in the measurement cell, only the toner was sucked for 10 seconds through a sieve (known in mass). The total amount of electricity of the sucked toner was measured using the above Q / m meter. Further, using an electronic balance, the mass of the sieve before suction and the mass of the sieve after suction were measured. The mass of the toner sucked was calculated by subtracting the mass of the sieve before suction from the mass of the sieve after suction. Then, the charge amount (μC / g) of the toner in the two-component developer was calculated using the following equation. Thus, the charge amount (initial) (μC / g) of the toner was calculated. The results are shown in Table 4.
[Toner charge amount in a two-component developer (μC / g)] = [total amount of toner attracted (μC)] / [mass of toner attracted (g)]

  Next, using the above-described color multi-function peripheral in which the two-component developer obtained according to the above-described method was placed in a developing device, a sample image with a printing rate of 5% was continuously printed on a recording medium for 5000 sheets. Thereafter, the charge amount (after continuous printing) (μC / g) of the toner was calculated according to the same method as the calculation of the charge amount (initial) (μC / g) of the toner. The results are shown in Table 4.

  When the charge amount of toner (initial) (μC / g) and the charge amount of toner (after continuous printing) (μC / g) are both 25 μC / g or more, “The charge amount of toner falls within the appropriate range It is evaluated that "it is maintained."

(Evaluation of image density)
The image density was evaluated using two-component developers D-1 to D-11 obtained according to the above-mentioned method. First, the two-component developer obtained according to the above-described method was placed in a developing device of a color multi-functional peripheral ("TASKalpha 5550" manufactured by Kyocera Document Solutions Inc.). Also, the corresponding toner was placed in the toner container of the color multifunction peripheral. Thereafter, the sample image for measuring the image density including the solid portion was printed on one recording medium. Thereafter, using a Macbeth reflection densitometer ("RD 914" manufactured by X-Rite), the reflection density (ID: image density) of the solid portion (solid portion of the formed sample image for measurement of image density) using the printing medium Was measured. Thus, the image density (initial) was obtained. The results are shown in Table 4.

  Next, using the color MFP, a sample image with a printing rate of 5% was continuously printed on a recording medium for 5000 sheets. Thereafter, the sample image for measuring the image density including the solid portion was printed on one recording medium. Thereafter, the image density (after continuous printing) was determined according to the same method as the measurement of the image density (initial). The results are shown in Table 4.

In Table 3, "Developer" means a two-component developer. “T” means the thickness of the carrier coat layer, and its unit is nm. “R ₁ ” means the diameter of the acrylic resin particle contained in the external additive, and its unit is nm. "R" means the opening diameter of the recess formed on the surface of the carrier coat layer, and the unit is nm. The "porosity" means the porosity of the recess on the surface of the coating layer. Further, in Table 4 below, "Developer" means a two-component developer.

  The two-component developers D-1 to D-8 (two-component developers according to Examples 1 to 8) each had the above-described basic configuration. That is, each of the two-component developers D-1 to D-8 contained a toner containing a plurality of toner particles and a carrier containing a plurality of carrier particles. The toner particles contained toner base particles and an external additive externally added to the surface of the toner base particles. The carrier particles contained a carrier core and a coat layer covering the surface of the carrier core. The external additive contained a plurality of first resin particles containing the first resin. The coat layer contained the second resin. The thickness of the coat layer was larger than the diameter of the first resin particle. A plurality of recesses were formed on the surface of the coat layer, and the opening diameter of the recesses was at least 1 time and not more than 3 times the diameter of the first resin particles.

  As shown in Table 4, with the two-component developers D-1 to D-8, not only after printing a sample image with a printing rate of 5% on one recording medium, but also with a sample with a printing rate of 5% Even after printing an image continuously on the recording medium for 5000 sheets, the charge amount of the toner was 25 μC / g or more. That is, in the two-component developers D-1 to D-8, even when continuous printing was performed, the charge amount of the toner could be maintained within the appropriate range.

In two-component developers D-9 to D-11 (two-component developers according to Comparative Examples 1 to 3), evaluation of charge amount of toner and image compared to two-component developers D-1 to D-8 It was inferior in the evaluation of concentration (ID). Specifically, in the two-component developer D-9, the charge amount of the toner was lower than the standard value even after printing a sample image with a printing rate of 5% on one recording medium. In addition, after printing a sample image of 5% printing rate continuously on the recording medium for 5000 sheets, the image density decreased. The reason why such a result is obtained is that, in the two-component developer D-9, the opening diameter R of the recess is considered to be less than the diameter r ₁ of the acrylic resin particles contained in the external additive ( Table 3).

  In the two-component developer D-10, the charge amount of the toner fell below the standard value after continuously printing 5000 sheets of a sample image having a printing rate of 5% on the recording medium. The reason why such a result is obtained is considered that in the two-component developer D-10, no recess is formed on the surface of the carrier coat layer (Table 3).

In the two-component developer D-11, the charge amount of toner was lower than the standard value even after printing a sample image with a printing rate of 5% on one recording medium. The reason why such a result is obtained is that, in the two-component developer D-11, the opening diameter R of the recess is more than three times the diameter r ₁ of the acrylic resin particle contained in the external additive. It is conceivable (Table 3).

The two-component developers D-1 to D-7 were more excellent in the evaluation of the image density (ID) than the two-component developer D-8. Specifically, in the two-component developers D-1 to D-7, even after printing 5000 sheets of a sample image having a printing rate of 5% continuously on a recording medium, the image density (ID) can be maintained high. Specifically, the image density (ID) was 1.2 or more. The reason why such results are obtained, in the two-component developer D-1 to D-7, the diameter r ₁ of the acrylic resin particles contained in the external additive is considered to be at 50nm or more 200nm or less ( Table 1).

  The carrier for developing an electrostatic latent image and the two-component developer according to the present invention can be used, for example, to form an image in a copying machine, a printer, or a multifunction machine.

DESCRIPTION OF SYMBOLS 10 toner particle 11 toner mother particle 13 first resin particle 20 carrier particle 21 carrier core 21 a surface 23 coat layer 23 a surface 27 concave portion 27 a bottom surface 100 binary developer 230 base layer 230 a surface 231 coat layer 231 a surface 232 surface layer 271 third resin particle

Claims (7)

An electrostatic latent image developing toner containing a plurality of toner particles,
And a carrier for electrostatic latent image development containing a plurality of carrier particles,
The toner particles include toner base particles and an external additive externally added to the surface of the toner base particles.
The carrier particles include a carrier core and a coat layer covering the surface of the carrier core,
The external additive contains a plurality of first resin particles containing a first resin,
The coat layer contains a second resin,
The thickness of the coating layer is larger than the diameter of the first resin particles,
The two-component developer, wherein a plurality of concave portions are formed on the surface of the coating layer, and the opening diameter of the concave portions is 1 to 3 times the diameter of the first resin particles.   The two-component developer according to claim 1, wherein an open area ratio of the concave portion on the surface of the coating layer is 30% or more and 60% or less.   The two-component developer according to claim 1, wherein the diameter of the first resin particles is 50 nm or more and 200 nm or less. The first resin is an acrylic resin,
The two-component developer according to any one of claims 1 to 3, wherein the second resin is a methyl silicone resin. Manufacturing process of toner for developing electrostatic latent image,
A process of manufacturing a carrier for developing an electrostatic latent image,
Mixing the toner for electrostatic latent image development and the carrier for electrostatic latent image development;
The manufacturing process of the electrostatic latent image developing toner includes a process of manufacturing toner particles including toner base particles and an external additive externally added to the surface of the toner base particles.
The manufacturing process of the carrier for electrostatic latent image development is as follows:
Coating the surface of the carrier core with a coat layer including a surface layer;
Treating the carrier core whose surface is covered with the coating layer with a solvent,
The external additive contains a plurality of first resin particles containing a first resin,
The surface layer is located on the outermost side in the radial direction of the carrier core in the coating layer, and includes a second resin and a third resin particle containing a third resin,
The third resin particles have a diameter of 1 to 3 times the diameter of the first resin particles,
In the processing step, a method for producing a two-component developer, in which the third resin particles exposed on the surface of the coating layer are selectively dissolved. The coating process is
Covering the surface of the carrier core with at least one underlayer;
Covering the surface of the underlayer with the surface layer,
The method of manufacturing a two-component developer according to claim 5 , wherein the underlayer includes the second resin and does not include the third resin particles. The second resin is a methyl silicone resin,
The third resin is an acrylic resin,
The solvent is tetrahydrofuran, the manufacturing method of the two-component developer according to claim 5 or 6.

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