JP6583227B2 - Method for producing carrier for developing electrostatic latent image - Google Patents

Description

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

  For example, a two-component developer including a carrier and a toner that is charged by friction with the carrier is known. As the carrier, a carrier including a carrier core and a resin layer coated on the surface of the carrier core can be used (see, for example, Patent Document 1). The carrier described in Patent Document 1 includes a fluororesin layer formed on the surface of the carrier core and a silicone-based resin layer formed on the surface of the fluororesin layer as a resin layer coated on the surface of the carrier core. .

JP-A-4-3333861

  Silicone resins are known to have excellent wear resistance. Therefore, when the resin layer coated on the surface of the carrier core includes a silicone-based resin layer, wear of the resin layer coated on the surface of the carrier core can be prevented.

  However, when the surface layer of the resin layer coated on the surface of the carrier core is a silicone resin layer, the charge imparting ability of the carrier may become too high. As a result, charge-up is likely to occur, and thus the developability of the toner tends to be reduced. Here, the charge imparting ability of the carrier means the ability of the carrier to charge the toner. The charge-up means a phenomenon that the toner is excessively positively or negatively charged.

  On the other hand, when the base layer of the resin layer coated on the surface of the carrier core is a silicone-based resin layer, the charge imparting ability of the carrier tends to decrease. Therefore, fog is likely to occur.

  Thus, when the resin layer coated on the surface of the carrier core includes a silicone resin layer, the charging stability of the toner is reduced. The occurrence of such a problem becomes remarkable when the carrier is used for a long time. In addition, when the carrier is used for a long time, the resistance of the carrier may change. When the resistance of the carrier changes, carrier development may occur. Here, carrier development means a phenomenon in which a carrier moves to an image carrier (for example, a photosensitive drum) together with toner.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to have excellent toner developability even when used for a long period of time and to prevent occurrence of fogging and carrier development. An electrostatic latent image developing carrier and a method for producing the same are provided. Another object of the present invention is to provide a two-component developer that has excellent toner developability and can prevent fogging and carrier development even when the carrier is used for a long period of time.

  The electrostatic latent image developing carrier according to the present invention positively charges the electrostatic latent image developing toner by friction. More specifically, the carrier for developing an electrostatic latent image according to the present invention includes a carrier core having a concave portion on a surface, and a first coat layer and a second coat layer that cover the surface of the carrier core. Including a plurality. The first coat layer and the second coat layer have a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. The first coat layer covers the entire surface of the carrier core. The second coat layer partially covers the surface of the first coat layer. The first coat layer contains an acrylic acid resin. The second coat layer contains a fluororesin.

  The method for producing a carrier for developing an electrostatic latent image according to the present invention is a method for producing a carrier for developing an electrostatic latent image in which the toner for developing an electrostatic latent image is positively charged by friction. More specifically, the method for producing a carrier for developing an electrostatic latent image according to the present invention includes a first coating step of covering the surface of a carrier core having irregularities with a first coating layer containing an acrylic resin, The second coating step of covering the surface of the first coating layer with a second coating layer containing a fluororesin, and the stirring for stirring the carrier core covered with the first coating layer and the second coating layer And a process. In the stirring step, the second coat layer is partially shaved to expose the first coat layer.

  According to the present invention, even when the carrier is used for a long period of time, the toner developability is excellent, the occurrence of fogging can be prevented, and the occurrence of carrier development can be prevented.

It is a figure which shows the structure of the two-component developer containing the carrier for electrostatic latent image development which concerns on embodiment of this invention. (A)-(c) is a figure for demonstrating the manufacturing method of the carrier for electrostatic latent image development which concerns on embodiment of this invention, respectively.

  An embodiment of the present invention will be described. Note that the evaluation results (for example, values indicating the shape or physical properties) of the carrier, carrier particles, toner, toner particles, toner base particles, or external additive particles are average particles from the powder unless otherwise specified. It is the number average of values measured for each of these average particles, picking up a considerable number.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value.

  The chargeability means chargeability in frictional charging unless otherwise specified. The strength of positive charging in frictional charging or the strength of negative charging in frictional charging can be confirmed by a known charge train or the like.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth) acrylonitrile”.

[Electrostatic latent image developing carrier according to this embodiment]
The electrostatic latent image developing carrier (hereinafter sometimes referred to as “carrier”) according to the present embodiment is obtained by applying an electrostatic latent image developing toner (hereinafter sometimes referred to as “toner”) due to friction. Charge positively. The carrier which concerns on this embodiment contains multiple carrier particles provided with the carrier core which has a recessed part on the surface, and the 1st coat layer and 2nd coat layer which cover the surface of a carrier core. The first coat layer and the second coat layer have a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. The first coat layer covers the entire surface of the carrier core. The second coat layer partially covers the surface of the first coat layer. The first coat layer contains an acrylic acid resin. The second coat layer contains a fluororesin. Thus, when image formation is performed using the two-component developer containing the carrier according to the present embodiment, the toner developability is excellent even when the carrier according to the present embodiment is used over a long period of time. Can be prevented, fog can be prevented from being caused by a decrease in the charge imparting ability of the carrier, and replenishment fog can be prevented from occurring.

  Specifically, the first coat layer covering the entire surface of the carrier core contains an acrylic resin. Thereby, the adhesiveness of a 1st coat layer and a carrier core can be improved. Therefore, even if it is a case where a carrier is used over a long period of time, it can prevent that a 1st coat layer peels from the surface of a carrier core. As described above, even when the carrier is used for a long period of time, since the exposure of the carrier core can be prevented, it is possible to prevent the resistance of the carrier from changing. Therefore, even when the carrier is used for a long time, the occurrence of carrier development can be prevented.

  The first coat layer covering the entire surface of the carrier core contains an acrylic resin, and the second coat layer partially covering the surface of the first coat layer contains a fluororesin. Thus, the surface of the carrier particle includes a region where the acrylic resin is preferentially present and a region where the fluororesin is preferentially present. Here, the acrylic resin has positive chargeability, whereas the fluororesin has negative chargeability. Further, the carrier according to the present embodiment charges the toner positively by friction. For these reasons, in the two-component developer including the carrier according to the exemplary embodiment, the toner has a fluorine resin preferentially present on the surface of the carrier particle over a region where the acrylic resin is preferentially present. It is easy to be attracted electrically to the area to be operated. Therefore, the toner can be positively charged.

  Here, even when the carrier is used for a long period of time, it is considered that the materials of the first coat layer and the second coat layer hardly change. Therefore, even when the carrier is used for a long period of time, the toner is easily attracted electrically to a region where the fluororesin is preferentially present on the surface of the carrier particle. Therefore, the toner can be positively charged even when the carrier is used for a long time. As a result, even when the carrier is used for a long period of time, the developing property of the toner can be maintained in an appropriate state, and the occurrence of fog due to a decrease in the charge imparting ability of the carrier can be prevented.

  In addition, even when the carrier is used for a long period of time, if the toner can be positively charged, the occurrence of reversely charged toner can be prevented. Even if the reversely charged toner is generated, the generated reversely charged toner is electrically attracted to a region of the carrier particle surface where the acrylic resin is preferentially present. Accordingly, even when the carrier is used for a long period of time, it is possible to prevent the reversely charged toner from being used for image formation, and thus it is possible to prevent occurrence of replenishment fog. Here, replenishment fog refers to a further decrease in the charge amount of the deteriorated toner due to the supply of new toner to the deteriorated toner (for example, reversely charged toner). It means that a small color point appears. The carrier according to the present embodiment has been described above. In the present embodiment, the carrier further has a configuration in which “the second coat layer selectively covers a portion of the surface region of the first coat layer corresponding to the concave portion on the surface of the carrier core”. It is preferable to use a carrier (hereinafter sometimes referred to as “carrier A”).

[Preferred configuration of carrier for developing electrostatic latent image according to this embodiment]
(Carrier A)
Preferably, the second coat layer selectively covers a portion of the surface region of the first coat layer corresponding to the concave portion on the surface of the carrier core. Here, the “part corresponding to the concave part on the surface of the carrier core” means a part located above the concave part on the surface of the carrier core. In addition, the “part corresponding to the convex part on the surface of the carrier core” described later means a part located above the convex part on the surface of the carrier core. The “convex part on the surface of the carrier core” means a part of the entire surface of the carrier core that is different from the concave part on the surface of the carrier core.

  When image formation is performed using a two-component developer containing carrier A, it becomes easy to maintain the developing property of the toner in an appropriate state even when carrier A is used over a long period of time. It is possible to further prevent the occurrence of fog due to a decrease in capability, further prevent the occurrence of carrier development, and further prevent the occurrence of replenishment fog.

  Specifically, the carrier A is preferably manufactured by a method described later (see [Method of manufacturing carrier according to this embodiment] below). Therefore, in carrier A, the surface roughness of the carrier particles is easily affected by the surface roughness of the carrier core. Thereby, the site | part corresponding to the recessed part of the surface of a carrier core among the surface area | regions of a 1st coat layer tends to have a recessed part shape compared with the site | part corresponding to the convex part of the surface of a carrier core. Here, in the carrier A, a portion of the surface region of the first coat layer corresponding to the concave portion on the surface of the carrier core is covered with the second coat layer. Therefore, the second coat layer is more likely to have a concave shape than the portion of the first coat layer exposed from the second coat layer. Therefore, in the two-component developer containing carrier A, the toner is more in comparison with the case where the second coat layer covers the portion corresponding to the convex portion of the surface of the carrier core in the surface area of the first coat layer. It is easy to gather in 2 coat layers.

  As described above, in the two-component developer including the carrier A, the toner has not only the reason that an electric attractive force acts between the toner and the second coat layer but also the surface of the second coat layer has a concave shape. It is easy to gather in a 2nd coat layer also for a reason. Here, even when the carrier A is used over a long period of time, it is considered that the materials of the first coat layer and the second coat layer are hardly changed, and the carrier core and the carrier particles are hardly deformed. it is conceivable that. Therefore, even when the carrier A is used for a long period of time, the toner is likely to collect in the second coat layer, and thus is easily positively charged. Therefore, even when the carrier A is used for a long period of time, it becomes easy to maintain the developing property of the toner in an appropriate state, and the occurrence of fog due to a decrease in the charge imparting ability of the carrier can be further prevented.

  Even when the carrier A is used for a long period of time, if the toner is easily positively charged, the generation of the reversely charged toner can be further prevented. Even if the reversely charged toner is generated, the generated reversely charged toner is electrically attracted to the portion of the first coat layer exposed from the second coat layer. Therefore, even when the carrier A is used for a long period of time, it is possible to further prevent the reversely charged toner from being used for image formation, thereby further preventing the occurrence of replenishment fog.

  Even when the carrier A is used for a long period of time, if the toner easily collects in the second coat layer, the portion of the first coat layer exposed from the second coat layer (that is, the surface of the first coat layer). In the region, it can be prevented from gathering at a portion corresponding to the convex portion on the surface of the carrier core. Here, the carrier particles are more likely to come into contact with each other in the part corresponding to the convex part on the surface of the carrier core than in the part corresponding to the concave part on the surface of the carrier core in the surface region of the carrier particle. Therefore, in the two-component developer containing the carrier A, it is possible to prevent the toner from being present at a location where the carrier particles are easily in contact with each other. Thus, if an image is formed using a two-component developer containing carrier A, an image can be formed without applying stress to the toner even when carrier A is used for a long time. This can also prevent a decrease in image density when the carrier A is used over a long period of time. The carrier A has been described above.

(Arithmetic mean roughness of the surface of the carrier core)
Preferably, the arithmetic average roughness of the surface of the carrier core is 0.3 μm or more and 2.0 μm or less. If image formation is performed using such a two-component developer containing a carrier, the adhesion between the first coat layer and the carrier core can be further enhanced even when the carrier is used over a long period of time. Therefore, even when the carrier is used for a long period of time, it becomes easy to maintain the developing property of the toner in an appropriate state, and it is possible to further prevent the occurrence of fog due to a decrease in the charge imparting ability of the carrier. Can be further prevented. Here, the above “arithmetic average roughness” means the arithmetic average roughness Ra defined by JIS (Japanese Industrial Standards) B0601-2013.

(Content of acrylic resin in first coat layer)
Preferably, the 1st coat layer contains 1.00 mass part or more and 30.0 mass parts or less of acrylic acid system resin to 100 mass parts carrier core. When the content of the acrylic resin in the first coat layer is 1.00 parts by mass or more with respect to 100 parts by mass of the carrier core, the coverage of the first coat layer on the surface of the carrier core is likely to be 100%. Therefore, it is easy to ensure the adhesion between the first coat layer and the carrier core. Therefore, even when the carrier is used for a long time, the occurrence of carrier development can be further prevented. Moreover, if the content of the acrylic resin in the first coat layer is 30.0 parts by mass or less with respect to the carrier core of 100 parts by mass, the thickness of the first coat layer can be prevented from becoming too large. Thereby, since the second coat layer is easily formed on the surface of the first coat layer, it is easy to maintain the charge imparting ability of the carrier.

(Content of fluororesin in the second coat layer)
Preferably, the 2nd coat layer contains 1.00 mass part or more and 30.0 mass parts or less of fluororesin with respect to 100 mass parts carrier core. If the content of the fluororesin in the second coat layer is 1.00 parts by mass or more with respect to 100 parts by mass of the carrier core, it is easy to prevent a decrease in charge imparting ability of the carrier. On the other hand, if the content of the fluororesin in the second coat layer is 30.0 parts by mass or less with respect to the carrier core of 100 parts by mass, it is easy to prevent the charge imparting ability of the carrier from becoming too high. From these things, if the content of the fluororesin in the second coat layer is 1.00 parts by mass or more and 30.0 parts by mass or less with respect to the carrier core of 100 parts by mass, it is easy to maintain the charge imparting ability of the carrier. Become.

[Two-component developer according to this embodiment]
The two-component developer according to this embodiment includes a carrier according to this embodiment and a toner that is positively charged by friction between the carrier according to this embodiment and the carrier according to this embodiment. As described above, the two-component developer according to this embodiment includes the carrier according to this embodiment. As a result, if image formation is performed using the two-component developer according to the present embodiment, the toner developability can be maintained in an appropriate state even when the carrier is used over a long period of time, and the charge imparting ability of the carrier can be maintained. It is possible to prevent the occurrence of fog due to the lowering of the toner level, the occurrence of carrier development, and the occurrence of replenishment fog.

  Hereinafter, an example of the configuration of the two-component developer according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of a configuration of a two-component developer according to the present embodiment.

  The two-component developer shown in FIG. 1 includes toner and a carrier that positively charges the toner by friction. The toner included in the two-component developer shown in FIG. 1 includes a plurality of toner particles 30. Each of the toner particles 30 is positively charged and includes toner base particles 31 and an external additive attached to the surface of the toner base particles 31. The external additive includes a plurality of external additive particles 32.

  The carrier included in the two-component developer shown in FIG. 1 includes a plurality of carrier particles 40. Each of the carrier particles 40 includes a carrier core 41 having a recess on the surface, and a first coat layer 42 and a second coat layer 43 that cover the surface of the carrier core 41. The first coat layer 42 and the second coat layer 43 have a laminated structure in the order of the first coat layer 42 and the second coat layer 43 from the surface of the carrier core 41. The first coat layer 42 covers the entire surface of the carrier core 41. The second coat layer 43 selectively covers a portion of the surface region of the first coat layer 42 corresponding to the concave portion on the surface of the carrier core 41. The first coat layer 42 contains an acrylic acid resin. The second coat layer 43 contains a fluororesin. As described above, since the two-component developer shown in FIG. 1 includes the carrier A, the functions and effects described in the above (Carrier A) can be achieved. The example of the configuration of the two-component developer has been described above with reference to FIG.

[Carrier Manufacturing Method According to this Embodiment]
The carrier manufacturing method according to this embodiment is a carrier manufacturing method in which toner is positively charged by friction. Specifically, in the carrier manufacturing method according to the present embodiment, the first coating step of covering the surface of the carrier core having irregularities with the first coating layer containing an acrylic resin, and the surface of the first coating layer, A second coating step covering with a second coating layer containing a fluororesin; and an agitation step of stirring the carrier core covered with the first coating layer and the second coating layer. In the stirring step, the second coat layer is partially shaved to expose the first coat layer. Thereby, the carrier which concerns on this embodiment can be manufactured comparatively simply.

  Hereinafter, an example of a carrier manufacturing method according to the present embodiment will be described with reference to FIGS. FIG. 2A to FIG. 2C are diagrams showing an example of a carrier manufacturing method according to this embodiment in the order of steps. The carrier manufacturing method shown in FIGS. 2A to 2C is a method of manufacturing a carrier including a plurality of carrier particles 40 shown in FIG. 1, and includes a carrier core preparation step, a first coating step, A 2nd coating process and a stirring process are included. The carrier particles manufactured at the same time are considered to have substantially the same configuration.

(Preparation process of carrier core)
A carrier core 41 shown in FIG. A plurality of recesses P are formed on the surface of the prepared carrier core 41. Thereby, the surface of the carrier core 41 has unevenness.

  Preferably, a carrier core having a surface arithmetic average roughness of 0.3 μm or more and 2.0 μm or less is prepared as the carrier core 41. This will be described below (stirring step).

(First coating process)
As shown in FIG. 2B, the surface of the carrier core 41 having irregularities is covered with a first coat layer 42 containing an acrylic resin. Thereby, the surface of the carrier core 41 is completely covered with the first coat layer 42. That is, the coverage of the first coat layer 42 on the surface of the carrier core 41 is 100%.

  Specifically, first, an acrylic acid resin is dispersed or dissolved in a first solvent to prepare a first coating liquid. As the first solvent, for example, methyl ethyl ketone or THF (tetrahydrofuran) can be used, and a mixed solution of methyl ethyl ketone and THF may be used. Next, the first coating liquid is attached to the surface of the carrier core 41. As a method of attaching the first coating liquid to the surface of the carrier core 41, for example, a method of immersing the carrier core 41 in the first coating liquid, or a method of spraying the first coating liquid onto the carrier core 41 in the fluidized bed. Is mentioned. While flowing the carrier core 41 having the first coating liquid adhered to the surface, heat treatment at a predetermined temperature (for example, a temperature selected from 200 ° C. to 300 ° C.) is performed for a predetermined time (for example, 30 minutes to 90 minutes or less). Time to be chosen). As a result, the first coating liquid is cured and the first coating layer 42 covering the surface of the carrier core 41 is formed. Hereinafter, the carrier core having the first coat layer 42 formed on the surface is referred to as a “first coated core 141”.

(Second coating process)
As shown in FIG. 2C, the surface of the first coat layer 42 is covered with a second coat layer 43a containing a fluororesin.

  Specifically, first, a fluororesin is dispersed or dissolved in a second solvent to prepare a second coating solution. As the second solvent, for example, methyl ethyl ketone or THF can be used, and a mixed solution of methyl ethyl ketone and THF may be used. Next, the second coating liquid is attached to the surface of the first coating layer 42. As a method of attaching the second coating liquid to the surface of the first coating layer 42, for example, a method of immersing the first coated core 141 (see FIG. 2B) in the second coating liquid, or in a fluidized bed A method of spraying the second coating liquid onto the first coated core 141 may be mentioned. While flowing the first coated core 141 having the second coating liquid adhered to the surface, heat treatment at a predetermined temperature (for example, a temperature selected from 200 ° C. to 300 ° C.) is performed for a predetermined time (for example, 30 minutes to 90 minutes). (Time selected from below). As a result, the second coating liquid is cured, and a second coating layer 43 a that completely covers the surface of the first coating layer 42 is formed. Hereinafter, the carrier core in which the first coat layer 42 and the second coat layer 43a are formed on the surface in this order is referred to as a “second coated core 142”.

(Stirring process)
The second coated core 142 (see FIG. 2C) is stirred. In detail, the 2nd coating core 142 is stirred using a mixing apparatus. By this stirring process, a physical impact is applied to the second coated core 142. Specifically, the second coated cores 142 easily collide with each other in a portion corresponding to the convex portion on the surface of the carrier core 41 in the surface region of the second coat layer 43a. As a result, the second coat layer 43a is preferentially scraped and the first coat layer 42 is exposed at that portion (the portion corresponding to the convex portion of the surface of the carrier core 41 in the surface region of the second coat layer 43a). Easy to do. In this way, a carrier including a plurality of carrier particles 40 shown in FIG. 1 is obtained. Therefore, the surface of the carrier particle 40 contained in the obtained carrier has an uneven shape along the unevenness of the surface of the carrier core 41 (see FIG. 1). Further, in the surface of the carrier particle 40, the first coat layer 42 is preferentially present in the portion corresponding to the convex portion on the surface of the carrier core 41, and the portion corresponding to the concave portion P on the surface of the carrier core 41. The second coat layer 43 is preferentially present (see FIG. 1).

  In the above (preparing step of the carrier core), when a carrier core having a surface arithmetic average roughness of 0.3 μm or more and 2.0 μm or less is prepared as the carrier core 41, the second coated core 142 is stirred and the first In the surface region of the coat layer 42, the second coat layer 43 a is more likely to remain in a portion corresponding to the concave portion on the surface of the carrier core 41. Therefore, when the carrier core 41 having a surface arithmetic average roughness of 0.3 μm or more and 2.0 μm or less is used as the carrier core, a carrier including a plurality of carrier particles 40 shown in FIG. 1 is easily manufactured.

  As a mixing device used for stirring the second coated core 142, for example, an FM mixer (manufactured by Nippon Coke Industries, Ltd.) can be used. The FM mixer includes a mixing tank with a temperature adjusting jacket, and further includes a deflector, a temperature sensor, an upper blade, and a lower blade in the mixing tank. When mixing the material (more specifically, powder or slurry, etc.) charged into the mixing tank using an FM mixer, the material in the mixing tank is swung in the vertical direction by rotating the lower blade. To flow. This causes convection of the material in the mixing tank. The upper blade rotates at a high speed and gives a shearing force to the material. The FM mixer applies a shearing force to the material, thereby allowing the material to be mixed with a strong mixing force.

  The stirring time of the second coated core 142 is determined, for example, by manufacturing a test carrier according to the above-described carrier manufacturing method. Specifically, first, a slight amount of colorants of different colors are mixed in the first coating liquid and the second coating liquid. In this way, the first coating liquid for test and the second coating liquid for test are prepared. Next, in the above-described carrier manufacturing method, using “test first coating liquid” instead of “first coating liquid”, using “test second coating liquid” instead of “second coating liquid”, A test first coat layer and a test second coat layer are sequentially formed on the surface of the carrier core. In this way, a carrier core (hereinafter, referred to as “test carrier core”) having the test first coat layer and the test second coat layer formed on the surface in this order is obtained. Subsequently, the test carrier core is stirred. At this time, the test carrier core is agitated while observing the test carrier core with a scanning electron microscope equipped with an EDX (energy dispersive X-ray analyzer). Then, the time point at which the first coating layer for testing is exposed at the portion corresponding to the convex portion of the surface of the carrier core in the surface area of the second coating layer for testing is defined as the end point of the stirring process, and stirring is started from the starting point of the stirring process The time required until the end of the treatment is regarded as the stirring time.

If carrier particles are observed with a scanning electron microscope equipped with EDX, it can be confirmed whether or not a carrier containing a plurality of desired carrier particles has been manufactured. Specifically, first, carrier particles are embedded in an ultraviolet curable resin. Next, CP (cross section polisher) processing is applied to the ultraviolet curable resin in which the carrier particles are embedded. The cut surface of the carrier particles formed by the CP processing is observed with a scanning electron microscope equipped with EDX. And if the following a and b are observed, it will be estimated that the carrier containing the desired carrier particle was manufactured.
a: The coating layer exists over the entire surface of the carrier core. b: The fluorine element (F) exists only in the portion corresponding to the concave portion of the surface of the carrier core in the surface region of the carrier particles.

  In the carrier manufacturing method shown in FIGS. 2A to 2C, the first coat layer 42 and the second coat layer 43a may be provided by the same method or different methods. It may be provided. Moreover, you may harden a 1st coating liquid and a 2nd coating liquid simultaneously (refer the below-mentioned Example).

[Method for Producing Two-Component Developer According to this Embodiment]
The method for producing a two-component developer according to this embodiment includes, for example, a step of producing a carrier by any of the methods described in [Method for producing carrier according to this embodiment] and a toner containing a plurality of toner particles. And a step of mixing the carrier and the toner.

<Toner preparation process>
The toner preparation step preferably includes a toner mother particle manufacturing step and an external addition step. The toner particles produced at the same time are considered to have substantially the same configuration.

(Manufacturing process of toner base particles)
When the toner base particles have a toner core and a shell layer, the toner base particles are preferably manufactured by sequentially performing the toner core manufacturing step and the shell layer forming step. When the toner base particles do not have a shell layer, it is preferable to manufacture the toner base particles without performing the shell layer forming step after the toner core manufacturing step.

(Manufacturing process of toner core)
The toner core is preferably produced by a known agglomeration method or a known pulverization method. Thereby, the toner core can be easily manufactured.

(Shell layer formation process)
For example, the shell layer can be formed by an in-situ polymerization method, a submerged cured coating method, or a coacervation method.

(External addition process)
The toner base particles and the external additive are mixed using a mixer (for example, an FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.). As a result, the external additive is physically bonded to the surface of the toner base particles. In this way, a toner containing a large number of toner particles is obtained.

<Mixing process>
The toner and carrier are mixed and stirred. At this time, the toner particles are preferably added in an amount of 1.00 to 20.0 parts by mass, more preferably 3.00 to 15.0 parts by mass with respect to 100 parts by mass of carrier particles. The In addition, the toner particles and the carrier particles can be mixed and stirred using a mixer (for example, a ball mill, a Nauter mixer, or a rocking mixer). In this way, the two-component developer according to this embodiment is obtained.

[Examples of materials constituting carrier particles]
As described above, the carrier particles contained in the carrier include a carrier core having a concave portion on the surface, and a first coat layer and a second coat layer that cover the surface of the carrier core.

<Carrier core>
The carrier core preferably contains a magnetic material. For example, the carrier core may be particles made of only a magnetic material, or particles made only of a magnetic material may be dispersed in a binder resin.

  Examples of the magnetic material contained in the carrier core include a ferromagnetic metal or a ferromagnetic metal oxide. Examples of the ferromagnetic metal include iron, cobalt, nickel, or a metal containing one or more of these metals. Examples of the “metal including one or more of these metals” include, for example, one or more of iron, cobalt, and nickel, copper, zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese, magnesium, Examples include alloys or mixtures with one or more of selenium, tungsten, zirconium, and vanadium. Examples of the ferromagnetic metal oxide include ferrite and magnetite.

  As another example of the magnetic material contained in the carrier core, for example, a mixture of at least one of a metal oxide, a metal nitride, and a metal carbide and the ferromagnetic metal oxide can be given. Examples of the metal oxide include iron oxide, titanium oxide, and magnesium oxide. Examples of the metal nitride include chromium nitride and vanadium nitride. Examples of the metal carbide include silicon carbide and tungsten carbide.

  The magnetic material contained in the carrier core is preferably ferrite or magnetite. Examples of ferrites 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 for 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 commercially available product may be used as the carrier core. Also, the carrier core may be made by pulverizing and firing the magnetic material. In the production of the carrier core, the saturation magnetization of the carrier can be adjusted by changing the amount of magnetic material added (particularly, the proportion of the ferromagnetic material). Further, the circularity of the carrier can be adjusted by changing the firing temperature in the production of the carrier core.

  More preferably, the carrier core is a ferrite particle. Ferrite particles tend to have sufficient magnetism for image formation. Moreover, the ferrite particle produced by the general manufacturing method does not become a true sphere but tends to have moderate irregularities on the surface. Specifically, the arithmetic average roughness of the surface of the ferrite particles (specifically, the arithmetic average 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 analyzer (“LA-700” manufactured by Horiba, Ltd.).

<First coat layer>
The first coat layer covers the entire surface of the carrier core. The first coat layer contains an acrylic acid resin, and is preferably composed of an acrylic resin.

(Acrylic acid resin)
The acrylic resin includes an acrylic resin and a styrene-acrylic resin.

(acrylic resin)
The acrylic resin is a polymer of one or more acrylic acid monomers. In order to synthesize an acrylic resin, for example, acrylic monomers as shown below can be preferably used.

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

(Styrene-acrylic acid resin)
The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. As the styrene monomer used for synthesizing the styrene-acrylic acid resin, the following styrene monomers can be suitably used. Moreover, as an acrylic acid-type monomer used in order to synthesize styrene-acrylic acid-type resin, the acrylic acid-type monomer as described in the above (acrylic resin) can be used conveniently.

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

<Second coat layer>
The second coat layer partially covers the surface of the first coat layer, and preferably selectively covers a portion of the surface region of the first coat layer corresponding to the concave portion on the surface of the carrier core. . The second coat layer contains a fluororesin, and is preferably composed of a fluororesin.

(Fluorine resin)
Examples of the fluororesin include polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene (hereinafter referred to as “PTFE”), polytrifluoroethylene (more specifically, polychlorotrifluoroethylene), and polyhexafluoro. Propylene, a copolymer of tetrafluoroethylene and hexafluoropropylene (hereinafter referred to as “FEP”), or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as “PFA”). Can be mentioned. Preferably, the fluororesin is at least one resin selected from the group consisting of PTFE, FEP, and PFA. Specifically, the fluororesin is made of PTFE, FEP, PFA, a mixture of PTFE and FEP (see Example 4 described later), a mixture of FEP and PFA, a mixture of PTFE and PFA, or PTFE, FEP and PFA. It is preferable that it is a mixture.

[Examples of materials constituting toner particles]
The toner particles include toner mother particles, and preferably further includes an external additive attached to the surface of the toner mother particles. When the toner particles do not have an external additive, the toner base particles correspond to the toner particles.

<Toner base particles>
When the toner base particles are capsule toners, the toner base particles include the following toner core and the following shell layer. When the toner base particles are non-capsule toner, the toner base particles correspond to the following toner core.

(Toner core)
The toner core contains a binder resin. The toner core may further contain at least one of a colorant, a release agent, a charge control agent, and magnetic powder.

(Toner core: Binder resin)
In the toner core, the binder resin generally occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core.

  Moreover, the property (specifically, hydroxyl value, acid value, glass transition point, or softening point) of the binder resin can be adjusted by using a combination of a plurality of types of resins as the binder resin. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to become anionic. Further, when the binder resin has an amino group or an amide group, the toner core tends to be cationic.

  The toner core preferably contains a thermoplastic resin. As the thermoplastic resin, for example, polyester resin, styrene resin, acrylic acid resin, olefin resin, vinyl resin, polyamide resin, or urethane resin can be used. As the acrylic resin, for example, an acrylic ester polymer or a methacrylic ester polymer can be used. As the olefin resin, for example, a polyethylene resin or a polypropylene resin can be used. As the vinyl resin, for example, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin can be used. A copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin, can also be used as the thermoplastic resin constituting the toner particles. For example, a styrene-acrylic acid resin or a styrene-butadiene resin can also be used as the thermoplastic resin constituting the toner core. Below, the polyester resin which is an example of binder resin is explained in full detail.

  The polyester resin is obtained by polycondensing one or more alcohols and one or more carboxylic acids. As alcohol for synthesizing a polyester resin, the following dihydric alcohol or trihydric or higher alcohol can be used, for example. As the dihydric alcohol, for example, diols or bisphenols can be used. As the carboxylic acid for synthesizing the polyester resin, for example, the following divalent carboxylic acids or trivalent or higher carboxylic acids can be used.

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

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

  Examples of the trivalent or higher alcohol include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5-trihydroxy Mention may be made of methylbenzene.

  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. Acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (more specifically, N-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.).

  Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4, 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

(Toner core: Colorant)
As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using toner, the amount of the colorant is preferably 1.00 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  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 the yellow colorant include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 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 used.

  The magenta colorant is, for example, selected from the group consisting of condensed 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 the magenta colorant include C.I. I. Pigment Red (2, 3, 5, 6, 7, 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).

  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 used.

(Toner core: Release agent)
The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to improve the fixing property or offset resistance of the toner, the amount of the release agent is preferably 1.00 parts by mass or more and 30.0 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the release agent include 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 a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated be used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

(Toner core: charge control agent)
The charge control agent is used, for example, for the purpose of improving the charge stability or charge rising property of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent to the toner core, the anionicity of the toner core can be enhanced. Further, the cationic property of the toner core can be increased by including a positively chargeable charge control agent in the toner core. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Toner core: magnetic powder)
As the material of the magnetic powder, for example, a ferromagnetic metal or an alloy thereof, a ferromagnetic metal oxide, or a material subjected to ferromagnetization treatment can be used. For example, iron, cobalt, or nickel can be used as the ferromagnetic metal. As the ferromagnetic metal oxide, for example, ferrite, magnetite, or chromium dioxide can be used. Examples of the ferromagnetization treatment include heat treatment. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

(Shell layer)
The shell layer preferably contains a thermoplastic resin. As the thermoplastic resin contained in the shell layer, for example, the thermoplastic resin described in the above (toner core: binder resin) can be used. Preferably, the shell layer contains a copolymer of one or more styrene monomers and one or more acrylic monomers. Thereby, the charging stability of the toner can be further improved. As the styrene monomer, for example, styrene can be used. As the acrylic monomer, for example, an acrylic ester can be used.

  The shell layer may further contain a thermosetting resin. Examples of the thermosetting resin contained in the shell layer include an aminoaldehyde resin, a polyimide resin, or a xylene-based resin. The amino aldehyde resin is a resin formed by condensation polymerization of a compound having an amino group and an aldehyde. Here, as the aldehyde, for example, formaldehyde can be used. Examples of aminoaldehyde resins include melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, or aniline resins. As the polyimide resin, for example, a maleimide polymer or a bismaleimide polymer can be used.

<External additive>
As the external additive particles contained in the external additive, particles made of an inorganic material can be used. As the particles made of an inorganic material, for example, silica particles or particles made of a metal oxide can be used. The metal oxide constituting the particles made of metal oxide is preferably, for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate.

  As the external additive particles, particles made of an organic acid compound or particles made of a resin may be used. As particles composed of an organic acid compound, particles composed of a fatty acid metal salt typified by zinc stearate can be used. Moreover, you may use the particle | grains which consist of a composite of 2 or more types of materials as an external additive particle | grain. One type of external additive particles may be used alone, or two or more types of external additive particles may be used in combination.

  The external additive is preferably contained in an amount of 0.500 parts by mass to 10.0 parts by mass with respect to 100 parts by mass of the toner base particles. Thereby, the fluidity and handleability of the toner particles are improved. When the external additive includes two or more types of external additive particles, the total amount of the two or more types of external additive particles is 0.500 parts by mass or more and 10 to 10 parts by mass with respect to 100 parts by mass of the toner base particles. It is preferably 0.0 part by mass or less. The particle diameter of the external additive particles is preferably 0.005 μm or more and 1 μm or less. Thereby, the fluidity and handleability of the toner particles are improved.

  Examples of the present invention will be described. Table 1 shows carriers C-01 to C-04 and C-11 to C-15 according to Examples or Comparative Examples. In Table 1, “MMA” means methyl methacrylate, and “MA” means methyl acrylate. “FEP + PTFE” means a mixture of FEP and PTFE. “Copolymer of MMA and MA + FEP” means a mixture of a copolymer of MMA and MA and FEP.

  Hereinafter, first, a carrier manufacturing method, an evaluation method, and an evaluation result will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Carrier manufacturing method]
(Manufacturing method of carrier C-01)
First, a carrier core was manufactured. Specifically, a mixture of 40 parts by mass of MnO, 9.0 parts by mass of MgO, 50 parts by mass of Fe ₂ O ₃ and 1.0 part by mass of SrO was pulverized over 2 hours using a ball mill. did. Then, it baked at 1000 degreeC for 5 hours, and obtained the carrier core which consists of manganese-type ferrite (Mn-Mg-Sr ferrite). In the obtained carrier core, the saturation magnetization in an applied magnetic field of 3000 (10 ³ / 4π · A / m) was 65 Am ² / kg, and the volume median diameter (D ₅₀ ) was 40 μm.

  Next, the first coat was performed. Specifically, first, a copolymer of methyl methacrylate and methyl acrylate and methyl ethyl ketone were mixed to obtain a first coating solution. Next, the carrier core was put into a fluid coating apparatus, and the first coating liquid was sprayed toward the carrier core while fluidizing the carrier core. The spray amount of the first coating liquid was adjusted so that the amount of the copolymer was 20.0 parts by mass with respect to 100 parts by mass of the carrier core. In this way, a carrier core whose surface was completely covered with the first coating liquid (hereinafter referred to as “third coated core”) was obtained. In the third coated core, the coverage of the first coating liquid on the surface of the carrier core was 100%.

  Subsequently, a second coat was performed. Specifically, first, the FEP solution and methyl ethyl ketone were mixed to obtain a second coating solution. Next, the second coating liquid was sprayed toward the third coated core while flowing the third coated core using the fluidized coating apparatus. The spray amount of the second coating liquid was adjusted so that the amount of FEP was 20.0 parts by mass with respect to 100 parts by mass of the carrier core. In this way, a carrier core (hereinafter referred to as “fourth coated core”) whose surface was covered in the order of the first coating liquid and the second coating liquid was obtained. In the fourth coated core, the coverage of the second coating liquid on the surface of the third coated core was 100%.

  Subsequently, heat treatment was performed. Specifically, the fluidized bed in the fluidized coating apparatus was subjected to heat treatment at a temperature of 280 ° C. for 1 hour to cure (resinize) the first coating liquid and the second coating liquid. As a result, a carrier core whose surface was covered in the order of the first coat layer and the second coat layer (hereinafter referred to as “fifth coated core”) was obtained.

  Subsequently, a stirring process was performed (“Stirring” in Table 1 is “Yes”). Specifically, the fifth coated core was put into an FM mixer ("FM-10B" manufactured by Nippon Coke Kogyo Co., Ltd.), and the FM mixer was used to perform a stirring process under conditions of a rotation speed of 1200 rpm and a processing time of 10 minutes. . By this stirring treatment, the second coat layer was shaved and exposed to the first coat layer in the surface region of the fifth coated core (powder) corresponding to the convex portion on the surface of the carrier core. As a result, a carrier containing a large number of carrier particles (carrier C-01) was obtained.

(Method for producing carrier C-02)
Carrier C-02 was produced according to the carrier C-01 production method except that the second coating liquid was prepared by mixing the PTFE solution and methyl ethyl ketone.

(Manufacturing method of carrier C-03)
Carrier C-03 was produced according to the carrier C-01 production method except that the second coating liquid was prepared by mixing the PFA solution and methyl ethyl ketone.

(Manufacturing method of carrier C-04)
A solution containing a mixture of FEP and PTFE and methyl ethyl ketone were mixed to prepare a second coating solution. In the mixture of FEP and PTFE, FEP: PTFE = 1: 1 (mass ratio). Except for this, carrier C-04 was produced according to the method for producing carrier C-01.

(Manufacturing method of carrier C-11)
Carrier C-11 was produced according to the production method of carrier C-01 except that the stirring treatment was not performed (“stirring” in Table 1 was “none”).

(Manufacturing method of carrier C-12)
After spraying the second coating liquid onto the carrier core, the first coating liquid was sprayed. Except for this, carrier C-12 was produced according to the production method of carrier C-01.

(Manufacturing method of carrier C-13)
The second coating liquid was sprayed on the carrier core without spraying the first coating liquid. Further, the stirring treatment was not performed (“stirring” in Table 1 is “none”). Except for these, carrier C-13 was produced according to the production method of carrier C-01.

(Manufacturing method of carrier C-14)
After spraying the first coating liquid onto the carrier core, the second coating liquid was not sprayed. Further, the stirring treatment was not performed (“stirring” in Table 1 is “none”). Except for these, carrier C-14 was produced according to the production method of carrier C-01.

(Manufacturing method of carrier C-15)
A copolymer of methyl methacrylate and methyl acrylate, FEP and methyl ethyl ketone were mixed to obtain a first coating solution. Moreover, after spraying the 1st coating liquid, the 2nd coating liquid was not sprayed. Further, the stirring treatment was not performed (“stirring” in Table 1 is “none”). Except for these, carrier C-15 was produced according to the production method of carrier C-01.

[Method for confirming coating state of carrier layer on carrier particles]
According to the following method, the coating state of the coating layer on the carrier particles was confirmed. Specifically, first, carrier particles were embedded in an ultraviolet curable resin. Next, CP processing was performed on the ultraviolet curable resin in which the carrier particles were embedded. The cut surfaces of the carrier particles formed by the CP processing were observed with a scanning electron microscope equipped with EDX. And it was investigated whether the following a and b were observed.
a: The coating layer exists over the entire surface of the carrier core. b: The fluorine element (F) exists only in the portion corresponding to the concave portion of the surface of the carrier core in the surface region of the carrier particles.

  In the carrier particles contained in each of the carriers C-01 to C-04, the above a and b were observed. Therefore, it was confirmed that the coverage of the first coat layer on the surface of the carrier core was 100%. Moreover, it was confirmed that the second coat layer preferentially exists in a portion corresponding to the concave portion on the surface of the carrier core in the surface region of the first coat layer.

  In the carrier particles contained in the carrier C-11, the above a was observed, but the above b was not observed. However, it was observed that elemental fluorine was present throughout the surface of the carrier particles. From these facts, it was confirmed that the coverage of the first coat layer on the surface of the carrier core was 100%. Further, it was confirmed that the coverage of the second coat layer on the surface of the first coat layer was 100%.

  In the carrier particles contained in the carrier C-12, the above a was observed. Further, in the surface region of the first coat layer (FEP layer), in a portion corresponding to the concave portion on the surface of the carrier core, a layer different from the first coat layer exists outside the first coat layer. Was observed. From these facts, it was confirmed that the coverage of the first coat layer on the surface of the carrier core was 100%. Moreover, it was confirmed that the second coat layer (acrylic resin layer) preferentially exists in a portion of the surface region of the first coat layer (FEP layer) corresponding to the concave portion on the surface of the carrier core.

  In the carrier particles contained in the carriers C-13 to C-15, it was confirmed that only one coat layer was formed on the surface of the carrier core. In the carrier particles contained in each of the carriers C-01 to C-04 and C-11 to C-15, the first coat layer and the second coat layer were each composed of the materials shown in Table 1. .

[Evaluation methods]
Each of the carriers C-01 to C-04 and C-11 to C-15 was evaluated using the target device prepared according to the following method. Specifically, the carriers C-01 to C-04 and C-11 to C-15 are placed in the housing of the developing device of the multifunction device (“TASKalfa 500ci” manufactured by Kyocera Document Solutions Co., Ltd., developing method: touch-down developing method). A two-component developer (target sample) containing each was added. In addition, the toner contained in the target sample was put in a toner container, and the toner container in which the toner was put was attached to the multifunction machine. Hereinafter, after explaining the manufacturing method of an object sample, an evaluation method is explained concretely.

<Production method of target sample>
As a target sample, a two-component developer including each of carriers C-01 to C-04 and C-11 to C-15 was manufactured.

(Method for producing two-component developer)
A toner containing a large number of non-capsule toner particles was produced according to the following method.
First, toner mother particles were produced. Specifically, using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries Co., Ltd.), 100 parts by mass of polyester resin (“XPE258” manufactured by Mitsui Chemicals, Inc.) and 5.00 parts by mass of polypropylene wax (Sanyo) “Viscol (registered trademark) 660P” manufactured by Kasei Kogyo Co., Ltd.), 5.00 parts by weight of a colorant (“REGAL® 330R” manufactured by Cabot), and 1.00 parts by weight of a quaternary ammonium salt ( "BONTRON (registered trademark) P-51" manufactured by Orient Chemical Co., Ltd.). The obtained mixture was melt-kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). Subsequently, the obtained kneaded product was cooled and then pulverized using a pulverizer (“Turbo Mill” manufactured by Freund Turbo). Subsequently, the obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner mother particles having a volume median diameter (D ₅₀ ) of 7 μm were obtained.

Next, external additive particles were externally added to the obtained toner base particles. Specifically, using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.), 100 parts by mass of toner base particles and 1.00 parts by mass of conductive titanium oxide particles (“EC manufactured by Titanium Industry Co., Ltd.”). −100 ”, base material: TiO ₂ , coating layer: Sb-doped SnO ₂ film, number average primary particle size: about 0.36 μm), 0.700 parts by mass of hydrophobic silica particles (manufactured by Nippon Aerosil Co., Ltd. AEROSIL (registered trademark) RA-200H ", content: dry silica particles surface-modified with trimethylsilyl groups and amino groups, number average primary particle size: about 12 nm) (rotation speed: 3500 rpm, mixing time: 5 minutes) )did. As a result, external additive particles (titanium oxide particles and silica particles) were adhered to the surface of the toner base particles. In this way, a toner containing a large number of non-capsule toner particles was obtained.

  The toner and each of the carriers C-01 to C-04 and C-11 to C-15 are mixed into a powder mixer ("Rocking Mixer (registered trademark)" manufactured by Aichi Electric Co., Ltd.), mixing method: container rotation swing method ) For 1 hour. At this time, the blending amount of the toner and the blending amount of each carrier were adjusted so that the toner content in the two-component developer was 10% by mass. In this way, a two-component developer was obtained.

<Measurement of image density and fog density>
First, a first evaluation sample image including a solid image portion and a blank portion (a region without printing) was printed using the target device. Then, the image density (ID) and the fog density (FD) of the first evaluation sample image were measured. In this way, the initial image density (ID) and fog density (FD) were each measured.

  Next, in an environment of a temperature of 20 ° C. and a humidity of 50% RH, using the target device, a printing durability test (hereinafter referred to as 1% printing durability) is performed by continuously printing 10,000 sample images with a printing rate of 1% on printing paper. Described). Then, the 2nd sample image for evaluation containing a solid image part and a blank part (area without printing) was printed using the object device. Then, the image density (ID) and the fog density (FD) of the second evaluation sample image were measured. Thus, the image density (ID) and the fog density (FD) after 1% printing durability were measured.

  Subsequently, a printing durability test (hereinafter referred to as 50% printing durability) in which 1000 sheets of sample images with a printing rate of 50% are continuously printed on printing paper using the target apparatus in an environment of a temperature of 20 ° C. and a humidity of 50% RH. Did). Then, the sample image for 3rd evaluation containing a solid image part and a blank part (area | region without printing) was printed using the object apparatus. The image density (ID) and fog density (FD) of the third evaluation sample image were each measured. Thus, the image density (ID) and the fog density (FD) after 50% printing durability were measured.

  Subsequently, in an environment of a temperature of 20 ° C. and a humidity of 50% RH, using the target apparatus, a printing durability test (hereinafter referred to as 5% printing durability) is performed by continuously printing 100,000 sample images with a printing rate of 5% on printing paper. Described). Then, the 4th sample image for evaluation containing a solid image part and a blank part (area without printing) was printed using the object device. Then, the image density (ID) and the fog density (FD) of the fourth evaluation sample image were measured. In this way, the image density (ID) and fog density (FD) after 5% printing durability were measured.

  In the measurement of the image density (ID), using a Macbeth reflection densitometer (“RD914” manufactured by X-Rite), the reflection density (ID: image density) of each of the solid image portions of the first to fourth evaluation sample images. ) Was measured.

In the measurement of the fog density (FD), the reflection density of each blank portion of the first to fourth evaluation sample images was measured using a color reflection densitometer (“R710” manufactured by Ihara Electronics Co., Ltd.). Then, the fog density (FD) was calculated based on the following equation.
FD = (reflection density of blank area) − (reflection density of unprinted paper)

  When the image density (ID) is 1.3 or more, it is evaluated as “very good”, when it is 1.0 or more and less than 1.3, it is evaluated as “good”, and when it is less than 1.0, “bad”. ". If the fog density (FD) is 0.0050 or less, it is evaluated as “very good”. If the fog density (FD) is more than 0.0050 and 0.010 or less, it is judged as “good”. ". The results are shown in Table 2.

<Whether carrier development has occurred>
Carrier particles adhering to the white paper portion of the printing paper (before the start of 1% printing) and at the end of 5% printing (the 100,000th sheet of 5% printing) The number of carrier particles transferred to the white paper portion was visually confirmed. Then, based on the number of carrier particles attached to the blank portion of the printing paper, it was evaluated whether or not carrier development occurred. The number of carrier particles, if the zero / cm ² was evaluated as "very good", to evaluate if the zero / cm ² ultra less than 0.25 pieces / cm ² as "good", 0.25 If the number of pieces / cm ² or more, it was evaluated as “bad”. The results are shown in Table 3.

  In Table 2, “1%”, “50%”, and “5%” indicate evaluation results after 1% printing, 50% printing, and 5% printing, respectively.

  In Table 3, “Carrier development” indicates the evaluation result of the occurrence of carrier development. “5%” indicates the evaluation result at the end of 5% printing durability (the 100,000th sheet with 5% printing durability).

  Carriers C-01 to C-04 (carriers according to Examples 1 to 4) each had the above-described basic configuration. Specifically, in each initial state of Examples 1 to 4, the two-component developer was accommodated in the accommodating portion of the developing device. The two-component developer includes a carrier and a positively chargeable toner that is positively charged by friction with the carrier. The carrier particles contained in the carrier were provided with a carrier core having a recess on the surface, and a first coat layer and a second coat layer covering the surface of the carrier core. The first coat layer and the second coat layer had a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. The first coat layer covered the entire surface of the carrier core. The second coat layer partially covered the surface of the first coat layer. The first coat layer contained an acrylic acid resin. The second coat layer contained a fluororesin.

  As shown in Tables 2 and 3, Carriers C-01 to C-04 were each excellent in image density and prevented from being fogged even after 5% printing durability. Further, the occurrence of carrier development was prevented even on the 100,000th sheet with a 5% printing durability. That is, in each of the carriers C-01 to C-04, even when the carrier was used for a long period of time, it was excellent in developability, the occurrence of carrier development could be prevented, and the occurrence of fogging could be prevented.

  The carrier C-11 (the carrier according to Comparative Example 1) was inferior in the evaluation of the fog density as compared with the carriers C-01 to C-04. Specifically, in the evaluation of fog density, fog occurred after 50% printing durability. The reason why such a result is obtained is considered as follows. Carrier C-11 was manufactured without performing a stirring process. Therefore, in the carrier particles contained in the carrier C-11, the FEP layer is formed over the entire surface region. Therefore, reversely charged toner is easily generated.

  The carrier C-12 (the carrier according to Comparative Example 2) was inferior in the fog density evaluation and the carrier development evaluation as compared with the carriers C-01 to C-04. Specifically, in the evaluation of fog density, fog occurred after 50% printing durability. In the carrier development evaluation, carrier development occurred at the end of 5% printing durability. The reason why such a result is obtained is considered as follows. In Carrier C-12, the first coat layer was an FEP layer, and the second coat layer was composed of a copolymer of methyl methacrylate and methyl acrylate. Moreover, the 2nd coat layer (acrylic resin layer) preferentially existed in the site | part corresponding to the recessed part of the surface of a carrier core among the surface regions of a 1st coat layer (FEP layer). Therefore, the charge imparting ability of the carrier is likely to be lowered. Further, it is difficult to improve the adhesion between the first coat layer (FEP layer) and the carrier core, and the resistance of the carrier is easily changed.

  Carrier C-13 (carrier according to Comparative Example 3) was inferior in evaluation of fog density and carrier development as compared with carriers C-01 to C-04. Specifically, fogging occurred after 5% printing durability. In the carrier development evaluation, carrier development occurred at the end of 5% printing durability. The reason why such a result is obtained is considered as follows. In Carrier C-13, only the FEP layer was formed on the surface of the carrier core. Therefore, reversely charged toner is easily generated.

  Carrier C-14 (carrier according to Comparative Example 4) was inferior in evaluation of the fog density as compared with Carriers C-01 to C-04. Specifically, in the evaluation of the fog density, fog was generated even in the initial stage. The reason why such a result is obtained is considered as follows. In Carrier C-14, only a layer composed of a copolymer of methyl methacrylate and methyl acrylate was formed on the surface of the carrier core. Therefore, the charge imparting ability of the carrier is likely to be lowered.

  Carrier C-15 (the carrier according to Comparative Example 5) was inferior in evaluation of fog density as compared with Carriers C-01 to C-04. Specifically, in the evaluation of the fog density, fog occurred after 50% printing and after 5% printing. The reason why such a result is obtained is considered as follows. In Carrier C-15, only a layer composed of a mixture of a copolymer of methyl methacrylate and methyl acrylate and FEP was formed on the surface of the carrier core. For this reason, it has been difficult to make FEP preferentially present in a portion of the surface region of the carrier particles contained in the carrier C-15 that corresponds to the concave portion on the surface of the carrier core. Therefore, it is difficult to stabilize the charge imparting ability of the carrier.

  The electrostatic latent image developing carrier according to the present invention can be used for forming an image in, for example, a copying machine, a printer, or a multifunction machine.

30 toner particles 31 toner mother particles 32 external additive particles 40 carrier particles 41 carrier core 42 first coat layer 43 second coat layer 43a second coat layer 141 first coated core 142 second coated core

Claims (2)

A method for producing an electrostatic latent image developing carrier for positively charging an electrostatic latent image developing toner by friction, comprising:
A first coating step of covering the entire surface of the carrier core having irregularities with a first coating layer containing an acrylic resin;
A second coating step of covering the entire surface of the first coating layer with a second coating layer containing a fluororesin;
An agitation step of agitating the carrier core covered with the first coat layer and the second coat layer;
Including
In the stirring step, the method for producing a carrier for developing an electrostatic latent image, wherein the second coat layer is partially shaved to expose the first coat layer. In the stirring step, in the surface region of the second coat layer, in the portion corresponding to the convex portion of the surface of the carrier core, the second coat layer is scraped to expose the first coat layer. Item 2. A method for producing a carrier for developing an electrostatic latent image according to Item 1 .

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