JP2018200372A - Electrostatic latent image developing carrier and two component developer - Google Patents

Abstract

To secure sufficient carrier durability and charging application property, and form a high quality image continuously for a long term.SOLUTION: An electrostatic latent image developing carrier comprises plural carrier particles comprising a carrier core, a first coat layer and a second coat layer for covering a surface of the carrier core. The first coat layer and the second coat layer have a laminate structure in the order of the first coat layer and second coat layer from a surface of the carrier core. The first coat layer includes a first thermosetting resin. The second coat layer includes a second thermosetting resin. A surface absorption force of the first coat layer is 70 nN or higher and 100 nN or lower. A pencil hardness of the second coat layer is 2H or more and 6H or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carrier for developing an electrostatic latent image and a two-component developer.

  For example, a two-component developer including a carrier (specifically, a carrier for developing an electrostatic latent image) and a positively chargeable toner that is positively charged by friction with the carrier is known. In addition, an image forming apparatus that consumes toner in the developing device for image formation and repeatedly uses a carrier in the developing device while stirring such a two-component developer in the developing device is known (for example, Patent Document 1). In such an image forming apparatus, only the toner out of the two-component developer (carrier and toner) is supplied into the developing apparatus.

  In the image forming apparatus described in Patent Document 1, the surface of carrier particles contained in a carrier is covered with a resin. The resin surface layer covering the surface of the carrier particles is a silicone resin.

JP-A-4-3333861

  Covering the surface of the carrier particles with a silicone resin can improve the durability of the carrier. Further, the presence of the silicone resin on the surface of the carrier particles improves the charge imparting property of the carrier. However, when the silicone resin is detached from the carrier particles, the charge imparting property of the carrier is lowered.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to continuously form high-quality images over a long period of time while ensuring sufficient carrier durability and chargeability.

  The carrier for developing an electrostatic latent image according to the present invention includes a plurality of carrier particles each including a carrier core and a first coat layer and a second coat layer that cover the surface of the 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 contains a first thermosetting resin. The second coat layer contains a second thermosetting resin. The surface adsorption force of the first coat layer is 70 nN or more and 100 nN or less. The pencil hardness of the second coat layer is 2H or more and 6H or less.

  The two-component developer according to the present invention includes the electrostatic latent image developing carrier according to the present invention and a positively chargeable toner that can be positively charged by friction between the electrostatic latent image developing carrier and the carrier.

  According to the present invention, it is possible to continuously form high-quality images over a long period of time while ensuring sufficient carrier durability and chargeability.

It is a figure which shows an example of the cross-sectional structure of the two-component developer which concerns on embodiment of this invention. It is a figure which expands and shows a part of surface of the carrier particle shown by FIG.

  An embodiment of the present invention will be described. Note that the evaluation results (values indicating shape, physical properties, etc.) regarding the powder (more specifically, toner base particles, external additives, toner, carrier, etc.) are not specified in the powder unless otherwise specified. It is the number average of the values measured for a considerable number of particles contained.

Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent-circle diameters of primary particles (Haywood diameter: the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Value. 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.

  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.

  The carrier according to the present embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

  First, an image forming unit (for example, a charging device and an exposure device) of an electrophotographic apparatus forms an electrostatic latent image on a photosensitive member (for example, a surface layer portion of a photosensitive drum) based on image data. Subsequently, a developing device of the electrophotographic apparatus (specifically, a developing device in which a two-component developer including toner and carrier is set) supplies the toner to the photosensitive member, and the electrostatic latent image formed on the photosensitive member. Develop the image. The toner is charged by friction with the carrier in the developing device before being supplied to the photoreceptor. For example, a positively chargeable toner is positively charged. In the developing process, toner (specifically, charged toner) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is supplied to the photosensitive member, and the supplied toner is By attaching to the electrostatic latent image on the photoconductor, a toner image is formed on the photoconductor. The consumed toner is replenished to the developing device from a toner container containing replenishment toner.

  In the subsequent transfer process, after the transfer device of the electrophotographic apparatus transfers the toner image on the photosensitive member to an intermediate transfer member (for example, a transfer belt), the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Transcript to. Thereafter, a fixing device (fixing method: nip fixing with a heating roller and a pressure roller) of the electrophotographic apparatus heats and pressurizes the toner to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan. After the transfer step, the toner remaining on the photoreceptor is removed by a cleaning member (for example, a cleaning blade). The transfer method may be a direct transfer method in which the toner image on the photosensitive member is directly transferred to the recording medium without using the intermediate transfer member. The fixing method may be a belt fixing method.

  The two-component developer includes a toner and a carrier. The toner is a powder composed of a large number of toner particles. The carrier is a powder composed of a large number of carrier particles. The toner contained in the two-component developer can be used as, for example, a positively chargeable toner. The positively chargeable toner is positively charged by friction with the carrier. Carrier particles contained in the carrier have magnetism. In order to impart magnetism to the carrier particles, at least a part of the carrier particles may be formed of a magnetic material (for example, a ferromagnetic material such as ferrite), or the carrier particles may be formed of a resin in which the magnetic particles are dispersed. You may form at least one part.

  The two-component developer according to this embodiment has the following configuration.

(Two-component developer according to this embodiment)
The two-component developer includes a carrier according to this embodiment having the following configuration (hereinafter referred to as a basic configuration) and a positively chargeable toner that can be positively charged by friction with the carrier.

(Basic carrier structure)
The carrier includes a plurality of carrier particles including a carrier core, a first coat layer, and a second coat layer. The first coat layer and the second coat layer cover the surface of the 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 contains a thermosetting resin (hereinafter referred to as “first thermosetting resin”). The second coat layer contains a thermosetting resin (hereinafter referred to as “second thermosetting resin”). The surface adsorption force of the first coat layer is 70 nN or more and 100 nN or less. The pencil hardness of the second coat layer is 2H or more and 6H or less. Each measuring method of the surface adsorption force and the pencil hardness is the same method as an example described later or an alternative method thereof. In addition, as a measuring method of pencil hardness, the method (JIS K5600-5-4) based on JIS is also known. However, with this method, it is difficult to measure the pencil hardness of carrier particles having a spherical shape. For this reason, in Examples described later, when a stirring test is performed using powder obtained by pulverizing a pencil lead (that is, a powdery pencil lead), a carrier is formed by the pencil lead powder. The pencil hardness of the coat layer was measured based on whether the particle coat layer was polished.

  The two-component developer includes a toner and a carrier. By stirring the two-component developer, the toner is charged by friction between the toner and the carrier. In the two-component developer, resin-coated carrier particles may be used for the purpose of improving the charge imparting property of the carrier (specifically, the ability to charge the toner). The resin-coated carrier particles include a carrier core and a coat layer (specifically, a resin layer) that covers the surface of the carrier core. The charge imparting property of the carrier core covered with the coat layer tends to be stronger than the charge imparting property of the carrier core (that is, the carrier core not covered with the coat layer). However, when the coating layer is worn by the above stirring, the charge imparting property of the carrier particles tends to be lowered. In order to suppress wear of the coating layer due to stirring, it is preferable that the coating layer is hard. However, a hard coat layer tends to have insufficient adhesion to the carrier core and tends to peel off from the carrier core. For this reason, it has been difficult to improve the durability of the carrier while suppressing the detachment of the coat layer.

  As a developing method of an image forming apparatus using a two-component developer, a developing method without carrier replenishment is known. In the developing method in which the carrier is not replenished, the carrier is not replenished to the developing device, and the carrier in the developing device is continuously used until the carrier is deteriorated and cannot be used. When the carrier in the developing device becomes unusable (or during regular maintenance of the image forming apparatus), the carrier in the developing device is changed from the old carrier (used carrier) to the new carrier (unused carrier). Replace with (carrier). In such a development method, it is necessary to change the carrier every time the lifetime of the carrier is reached. The high carrier replacement frequency impairs the convenience of the image forming apparatus. However, there are problems as described above in extending the life of the carrier. In view of this situation, an image forming apparatus using a trickle development method has been developed. In the trickle developing method, the image forming apparatus discharges the carrier in the developing apparatus and replenishes the carrier into the developing apparatus. That is, the carrier in the developing device is automatically replaced before the charge imparting property of the carrier in the developing device becomes insufficient.

  With the advent of trickle-development-type image forming apparatuses, little research has been conducted on extending the life of carriers. However, even after the trickle-development-type image forming apparatus has been put into practical use, the present inventor has continued research on the extension of the carrier life and invented the carrier having the above-described basic configuration. As described below, the above-described basic configuration makes it possible to improve the durability of the carrier while suppressing the detachment of the coat layer.

  In the carrier having the above-described basic configuration, the first coat layer and the second coat layer covering the surface of the carrier core 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 surface adsorption force of the first coat layer is 70 nN or more and 100 nN or less, and the pencil hardness of the second coat layer is 2H or more and 6H or less. By arranging the first coat layer having a strong surface adsorbing power as the lower layer and the hard second coat layer as the upper layer, the second coat layer has strong adhesiveness (specifically, a surface adsorbing force of 70 nN or more). The carrier core is strongly bonded via the first coat layer. The second coat layer is held on the carrier core with a strong adhesive force. Moreover, the second coat layer has sufficient hardness (specifically, pencil hardness of 2H or more). For this reason, it becomes easy to ensure sufficient durability of the carrier.

  As a method for increasing the hardness of the second coat layer, a method of dispersing conductive fine particles (for example, metal fine particles) in the second coat layer is also conceivable. However, when conductive fine particles are added to the second coat layer, the electric resistance of the second coat layer is lowered, and the charge imparting property of the carrier tends to be weakened. On the other hand, in the carrier having the above-described basic configuration, the second coat layer contains a thermosetting resin (specifically, the second thermosetting resin). For this reason, even if a 2nd coating layer does not contain electroconductive fine particles, the hardness of a 2nd coating layer can fully be raised. Further, in the carrier having the above-described basic configuration, not only the second coat layer but also the first coat layer contains a thermosetting resin (specifically, the first thermosetting resin). For this reason, after the resin (specifically, thermosetting resin) is cured, the first coat layer and the second coat layer are not easily deformed even when heated (or cooled). With such a configuration, peeling of the second coat layer due to thermal distortion can be suppressed.

  The surface adsorption force of the first coat layer is preferably 100 nN or less. If the surface adsorption force of the first coat layer is too strong, the material of the first coat layer oozes out to the surface of the carrier particles, and the adhesion force on the surface of the carrier particles tends to increase. When the adhesion force of the surface of the carrier particles becomes strong, the carrier is easily fixed to a member (more specifically, a photosensitive drum or a developing roller) existing in the image forming apparatus. Such sticking of the carrier causes image defects. Also, spent (specifically, a phenomenon in which toner particles adhere to carrier particles) is likely to occur. When spent occurs, the charge imparting property of the carrier tends to be weak (see carrier CB-2 described later).

  The pencil hardness of the second coat layer is preferably 6H or less. If the second coat layer is too hard, the second coat layer tends to become brittle. When the second coat layer becomes brittle, the charge imparting property of the carrier tends to be insufficient in continuous printing (see carrier CB-3 described later). In order to suppress spent, it is preferable that the surface adsorption force of the second coat layer is 65 nN or less.

  As described above, the above-described basic configuration makes it possible to improve the durability of the carrier while suppressing the detachment of the coat layer. For this reason, the carrier having the above-mentioned basic configuration has sufficient durability, and even when used in a developing method that does not supply the carrier, the charge imparting property is maintained in continuous printing and the image quality is continuously improved over a long period of time. Can continue to form images.

By changing the curing conditions of the thermosetting resin contained in the coating layer (more specifically, the temperature of the heat treatment, the time of the heat treatment, the amount of the hardener added, etc.), the surface adsorption force and pencil hardness of the coat layer Can be adjusted. The curing agent is a curing catalyst that acts to promote curing of the thermosetting resin. For example, tetrabutyl orthotitanate or tetraisopropyl orthotitanate can be used as a curing agent for the silicone resin. In the carrier having the above basic configuration, 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. After the first coat layer is cured on the surface of the carrier core, the laminated structure as described above can be formed on the surface of the carrier core by curing the second coat layer on the first coat layer. However, if the first coat layer is not sufficiently cured, the first coat layer is deformed when the second coat layer is cured, and the internal stress of the second coat layer is increased. In the carrier having the basic configuration described above, the second coat layer located in the upper layer is harder than the first coat layer located in the lower layer. The hard second coat layer is easily affected by the distortion of the first coat layer. When the internal stress of the second coat layer increases, the durability of the second coat layer tends to decrease. In order to suppress the distortion of the first coat layer when the second coat layer is cured, the curing start temperature of the first thermosetting resin (specifically, the thermosetting resin contained in the first coat layer) is It is preferably 20 ° C. or more higher than the curing start temperature of the second thermosetting resin (specifically, the thermosetting resin contained in the second coat layer). That, and the curing initiation temperature of the first thermosetting resin "T _CA", and the curing initiation temperature of the second thermosetting resin "T _CB", when referring respectively, wherein "20 ≧ (T _CA -T It is preferable to satisfy the relationship of “ _CB )”. By satisfying this relationship, it is possible to sufficiently cure the second thermosetting resin at the same temperature as the first thermosetting resin or at a lower temperature. For this reason, distortion of the 1st coat layer at the time of hardening the 2nd coat layer can be controlled.

When a thermosetting resin solution (that is, a solution in which a thermosetting resin is dissolved in a solvent) is heated at a rate of temperature increase of 10 ° C./min, the solid in the thermosetting resin solution before the start of curing The temperature at which the mass reduction rate becomes 1% by mass or more with respect to the mass of the minute corresponds to the curing start temperature of the thermosetting resin. The mass of the solid content before the start of curing (specifically, when all the solvent in the solution is volatilized and only the solid content remains) is “M _A ”, and the mass of the solid content at the curing start temperature is “M _B ”. And satisfying the relationship of the expression “1 ≦ 100 × (M _A −M _B ) / M _A ”. “100 × (M _A −M _B ) / M _A ” corresponds to the mass reduction rate (unit:%). For example, regarding the coating material A-1 described later, the temperature when all the solvent in the solution was volatilized and only the solid content remained was 140 ° C. Since the thermosetting resin is generally cured by a dehydration condensation reaction, it is possible to detect the timing at which the curing of the resin starts based on a decrease in the mass of the resin (that is, the solid content). The mass of the resin can be measured using, for example, a thermogravimetric measurement device (“Pyris1 TGA” manufactured by Perkin Elmer, measurement method: hanging balance).

  In order to easily adjust the curing start temperature of the thermosetting resin in the coating layer, it is preferable that at least one of the first coating layer and the second coating layer contains a curing agent. By adding a curing agent, the curing start temperature of the thermosetting resin can be lowered. In order to suppress peeling of the second coat layer, it is preferable that the first coat layer and the second coat layer each contain a silicone resin. Since both the first thermosetting resin contained in the first coat layer and the second thermosetting resin contained in the second coat layer are silicone resins, the first coat layer and the second coat layer A crosslinked structure is easily formed between the two. By forming such a crosslinked structure, peeling of the second coat layer can be suppressed. Regarding the silicone resin, there are commercially available products having a high curing start temperature (for example, a coating material A-3 described later) and commercial products having a low curing start temperature (for example, a coating material A-5 described later).

  In the first preferred example of the first coat layer and the second coat layer, the first coat layer contains a silicone resin and does not contain a curing agent, and the second coat layer contains a silicone resin and is cured. Contains no agent.

  In the second preferred example of the first coat layer and the second coat layer, the first coat layer contains a silicone resin and does not contain a curing agent, and the second coat layer comprises a silicone resin, a curing agent, Containing.

  In a third preferred example of the first coat layer and the second coat layer, the first coat layer contains a silicone resin and a curing agent, and the second coat layer contains a silicone resin and contains a curing agent. do not do.

  In a preferred example of the carrier having the basic configuration described above, the first coat layer contains a silicone resin (first thermosetting resin), and the second coat layer contains a silicone resin (second thermosetting resin). . It is particularly preferable that the first coat layer and the second coat layer have a thickness as shown below.

  The thickness of the first coat layer is not less than 100 nm and not more than 450 nm, the thickness of the second coat layer is not less than 550 nm and not more than 800 nm, and the total thickness of the thickness of the first coat layer and the thickness of the second coat layer is 800 nm. The thickness is 1200 nm or less.

  When the first coat layer is too thick, when the first coat layer is distorted due to mechanical stress or the like, the stress applied to the second coat layer increases. The thickness of the first coat layer is particularly preferably 300 nm or less. If the total thickness of the first coat layer and the second coat layer is too large, the influence of the magnetic force of the carrier core on the surface of the carrier particles is weakened, and it is difficult to secure a sufficient magnetic force of the carrier. . Further, when the amount of the material for forming the coat layer is increased, the carriers are likely to aggregate before the coat layer is cured. The total thickness of the first coat layer and the second coat layer is particularly preferably 1000 nm or less.

  The thickness of the coat layer can be measured by analyzing a TEM image of the cross section of the carrier particle using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). The cross section of the carrier particles can be prepared using, for example, a cross-section sample preparation device (“Cross Section Polisher (registered trademark)” manufactured by JEOL Ltd.). When the thickness of the coat layer is not uniform in one carrier particle, four equally spaced locations (specifically, two straight lines that are perpendicular to each other at the approximate center of the cross section of the carrier particle are drawn, and the two straight lines are The thickness of the coat layer is measured at each of the four points intersecting the coat layer, and the arithmetic average of the four measured values obtained is taken as the evaluation value of the carrier particles (coat layer thickness). When the boundary between the carrier core and the coat layer is unclear in the TEM image, the TEM and the electron energy loss spectroscopy (EELS) are combined to include the feature included in the coat layer in the TEM image. By performing basic element mapping, the boundary between the carrier core and the coating layer can be clarified. Further, the boundary between the carrier core and the coating layer may be clarified by SEM-EDX (energy dispersive X-ray spectroscopy).

  In addition, the first coat layer and the second coat layer having the thicknesses as described above preferably cover the carrier core in the following manner.

  The first coat layer covers an area of 85% to 98% of the surface area of the carrier core, and the second coat layer is an area exposed from the first coat layer in the surface area of the carrier core. And all of the above are also present on the first coat layer.

  By covering the carrier core with the first coat layer and the second coat layer as described above, the entire surface of the carrier core is covered with either the first coat layer or the second coat layer. There are no exposed parts on the surface. In the carrier having such a configuration, the presence of the coat layer makes it easy to ensure sufficient chargeability of the carrier. When the surface of the carrier core (for example, ferrite particles) is covered with the first coat layer, it is possible to completely cover the surface of the carrier core as long as the first coat layer is quite thick. It is difficult to completely cover the surface of the carrier core (for example, ferrite particles) with only one coat layer. However, the first coat layer and the second coat layer are formed by further covering the surface of the carrier core (hereinafter sometimes referred to as the first coat particles) covered with the first coat layer with the second coat layer. Can cover the entire surface of the carrier core. In order to improve the durability of the carrier, the coverage of the second coat layer is preferably 90% or more and 100% or less in terms of area ratio. The coverage of the second coat layer can be calculated based on the formula “100 × (second coat layer coverage area) / (surface area of the first coat particles)”. In the formula, the “second coat layer covering area” is an area of a region covered with the second coat layer in the surface region of the first coat particle. The “surface area of the first coated particles” is an area of the entire surface of the first coated particles.

  The presence of each of the first coat layer and the second coat layer can be confirmed by an electron microscope. Further, the coverage (area ratio) of each of the first coat layer and the second coat layer is obtained by photographing the surface of carrier particles (for example, pre-stained carrier particles) with an electron microscope, It can be measured by analyzing using commercially available image analysis software.

  The carrier core is preferably ferrite particles. 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. It is considered that when the surface of the carrier core has an appropriate roughness, the adhesion between the surface of the carrier core and the first coat layer is improved, and peeling of the first coat layer is suppressed.

  FIG. 1 shows a schematic configuration of a two-component developer according to this embodiment. The two-component developer shown in FIG. 1 includes a plurality of toner particles 10 and a plurality of carrier particles 20.

  The toner particles 10 include toner base particles 11 and external additives (a plurality of external additive particles 13) attached to the surface of the toner base particles 11. The external additive particles 13 may be inorganic particles (for example, silica particles) or resin particles.

  The carrier particle 20 includes a carrier core 21 and a coat layer 22 that covers the surface of the carrier core 21. The coat layer 22 includes a first coat layer 22a and a second coat layer 22b. Each of the first coat layer 22a and the second coat layer 22b is a resin film.

  FIG. 2 shows an enlarged surface of the carrier particle 20. As shown in FIG. 2, the first coat layer 22a and the second coat layer 22b have a laminated structure in the order of the first coat layer 22a and the second coat layer 22b from the surface of the carrier core 21. For example, the first coat layer 22 a covers an area of 85% or more and 98% or less of the surface region of the carrier core 21. The second coat layer 22b covers all of the surface area of the carrier core 21 exposed from the first coat layer 22a (for example, the area R in FIG. 2), and the first coat layer. 22a also exists. The entire surface of the carrier core 21 is covered with either the first coat layer 22a or the second coat layer 22b, and no exposed portion exists on the surface of the carrier core 21. The coverage (area ratio) of the second coat layer 22b is, for example, 100%.

  The toner particles contained in the toner may be toner particles not having a shell layer (hereinafter referred to as non-capsule toner particles) or toner particles having a shell layer (hereinafter referred to as capsule toner particles). There may be. Capsule toner particles can be produced by forming a shell layer on the surface of non-externally added non-capsule toner particles (toner core). The shell layer may consist essentially of a thermosetting resin, may consist essentially of a thermoplastic resin, or may contain both a thermoplastic resin and a thermosetting resin. .

  Non-capsule toner particles can be produced, for example, by a pulverization method or an aggregation method. In these methods, the internal additive is easily dispersed well in the binder resin of the non-capsule toner particles.

  In an example of the pulverization 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 pulverized, and the obtained pulverized product is classified. Thereby, toner mother particles are obtained. When the pulverization method is used, the toner base particles can often be produced more easily than when the aggregation method is used.

  In an example of the aggregation method, first, these fine particles are aggregated in an aqueous medium containing fine particles of the binder resin, the release agent, and the colorant until a desired particle diameter is obtained. Thereby, aggregated particles containing 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 mother particles having a desired particle diameter are obtained.

  When producing the capsule toner particles, the method for forming the shell layer is arbitrary. For example, the shell layer may be formed using any of an in-situ polymerization method, a submerged cured coating method, and a coacervation method.

  Next, preferred examples of the configuration of each of the non-capsule toner particles and the carrier particles will be described. The toner particles may include an external additive. When the toner particles include an external additive, the toner particles include a toner base particle and an external additive. However, external additives may be omitted if not necessary. When omitting the external additive, the toner base particles correspond to the toner particles.

[Non-capsule toner particles: toner base particles]
The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, at least one of 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 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 overall properties of the toner base particles. In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, it is particularly preferable that the toner base particles contain at least one of a polyester resin and a styrene-acrylic acid resin as a binder resin.

(Coloring agent)
The toner base particles may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. In order to obtain a toner suitable for image formation, 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. 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 base particles include a yellow colorant (more specifically, naphthol yellow, monoazo yellow, diazo yellow, disazo yellow, or anthraquinone compound), a magenta colorant (more specifically, quinacridone compound, naphthol compound, carmine). 6B, or monoazo red), or a cyan colorant (more specifically, a phthalocyanine blue or anthraquinone compound) may be contained.

(Release agent)
The toner base particles may contain a 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 part by mass or more and 30 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 can be suitably used. One type of release agent may be used alone, or multiple 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 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 positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner base particles, the cationicity of the toner base particles can be increased. However, if sufficient chargeability is ensured in the toner, it is not necessary to add a charge control agent to the toner base particles.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, Ferrite, magnetite, chromium dioxide, or the like) or a material subjected to ferromagnetization treatment (more specifically, a carbon material or the like imparted with ferromagnetism by heat treatment) can be suitably used. In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to use the surface-treated magnetic particles as the magnetic powder. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

[Non-capsule toner particles: external additive]
An external additive (specifically, a powder containing a plurality of external additive particles) may be adhered to the surface of the toner base particles. Unlike the internal additive, the external additive does not exist inside the toner base particles, but selectively exists only on the surface of the toner base particles (surface layer portion of the toner particles). For example, by stirring together the toner base particles (powder) and the external additive (powder), the external additive particles can be attached to the surface of the toner base particles. The toner base particles and the external additive particles do not chemically react with each other and are physically bonded instead of chemically. The strength of the bond between the toner base particles and the external additive particles depends on the stirring conditions (more specifically, the stirring time, the rotation speed of the stirring, etc.), the particle diameter of the external additive particles, and the shape of the external additive particles. And the surface condition of the external additive particles.

  The external additive particles are preferably inorganic particles such as silica particles or metal oxide particles (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate). Particularly preferred. However, particles of an organic acid compound such as a fatty acid metal salt (more specifically, zinc stearate) or resin particles may be used as the external additive particles. Moreover, you may use the composite particle which is a composite of a multiple types of material as external additive particle | grains. One type of external additive may be used alone, or a plurality of types of external additives may be used in combination.

  The external additive particles may be surface-treated. For example, when silica particles are used as the external additive particles, hydrophobicity and / or positive chargeability may be imparted to the surface of the silica particles by the surface treatment agent. Examples of the surface treatment agent include a coupling agent (more specifically, a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent), or silicone oil (more specifically, dimethyl silicone oil). Etc.) can be suitably used.

  In order to improve the fluidity of the toner, it is preferable to use inorganic particles (powder) having a number average primary particle diameter of 5 nm to 30 nm as external additive particles. In order to make the external additive function as a spacer between the toner particles to improve the heat-resistant storage stability of the toner, resin particles (powder) having a number average primary particle diameter of 50 nm to 200 nm are used as the external additive particles. It is preferable to do.

  In order to fully perform the functions of the external additive while suppressing the detachment of the external additive particles from the toner particles, the amount of the external additive (if multiple types of external additive particles are used, The total amount of external additive 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.

[Carrier particles]
In the carrier having the basic configuration described above, the carrier particles include a carrier core, and a first coat layer and a second coat layer that cover the surface of the 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 carrier particles having such a laminated structure are obtained by forming a first coat layer on the surface of the carrier core to obtain first coat particles (specifically, a composite of the carrier core and the first coat layer), It is obtained by forming a second coat layer on the surface of the coat particles. Any part of the first coat layer is located closer to the carrier core than the second coat layer. That is, on the carrier core, there is no portion where the second coat layer and the first coat layer are laminated in this order from the surface of the carrier core.

(Career core)
The carrier core preferably contains a magnetic material. The carrier core may be magnetic material particles, or the magnetic material particles may be dispersed in the binder resin of the carrier core. Examples of the magnetic material contained in the carrier core include a ferromagnetic metal (more specifically, iron, cobalt, nickel, or an alloy containing one or more of these metals), a ferromagnetic metal oxide (more specifically, Specifically, a ferrite etc. are mentioned. Suitable examples of 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. 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, in the production of the carrier core, the circularity of the carrier can be adjusted by changing the firing temperature.

(First coat layer and second coat layer)
Each of the first coat layer and the second coat layer is substantially composed of a resin. However, the additive may be dispersed in the resin constituting each coat layer. In the carrier having the basic configuration described above, each of the first coat layer and the second coat layer contains a thermosetting resin. Examples of thermosetting resins include silicone resins, epoxy resins, melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, aniline resins, polyimide resins (more specifically, maleimides). Polymer or bismaleimide polymer), or a xylene-based resin.

  In order to improve the durability of the carrier, the first coat layer and the second coat layer preferably each contain a thermosetting silicone resin. Moreover, it is preferable that a crosslinked structure exists between the first coat layer and the second coat layer.

The silicone resin has a siloxane bond “Si—O—Si” as a main chain and an organic group as a side chain. The methyl silicone resin has only methyl groups as side chain organic groups. The methylphenyl silicone resin has a methyl group and a phenyl group as side chain organic groups. The silicone resin has, for example, a structure represented by the following formula (1-1) or the following formula (1-2). N ₁₁ , n ₂₁ , and n ₂₂ in formula (1-1) and formula (1-2) each independently represent the number of repeating units (arbitrary number). In order for the silicone resin to have excellent durability, it is preferable that the main chains (siloxane bonds: Si—O—Si) of the silicone resin are three-dimensionally connected.

In formula (1-1), R ₁₁ represents an organic group (more specifically, a methyl group or a phenyl group). R ₁₂ represents a hydrogen atom or an organic group (more specifically, a methyl group or a phenyl group). R ₁₁ and R ₁₂ may be the same or different from each other. Y ₁₁ represents the first terminal part, and Y ₁₂ represents the second terminal part. For example, an organosiloxy group (more specifically, a trimethylsiloxy group or the like) is attached to the first terminal portion. For example, an organosilyl group (more specifically, a trimethylsilyl group or the like) is attached to the second terminal portion.

In formula (1-2), R ₂₁ , R ₂₂ , and R ₂₃ each independently represents an organic group (more specifically, a methyl group or a phenyl group). R ₂₄ represents a hydrogen atom or an organic group (more specifically, a methyl group or a phenyl group). Y ₂₁ represents the first end, and Y ₂₂ represents the second end. For example, an organosiloxy group (more specifically, a trimethylsiloxy group or the like) is attached to the first terminal portion. For example, an organosilyl group (more specifically, a trimethylsilyl group or the like) is attached to the second terminal portion.

  Examples of the present invention will be described. Table 1 shows carriers CA-1 to CA-7 and CB-1 to CB-7 (each carrier for electrostatic latent image development) according to Examples or Comparative Examples.

  In Table 1, “A-1” to “A-5” regarding the “materials” of the first coat layer and the second coat layer were as follows.

The coating material A-1 is a thermosetting silicone resin solution (“SR2431” manufactured by Toray Dow Corning Co., Ltd., resin: methyl silicone resin, curing start temperature: 220 ° C. (210 ° C. when a curing agent is added), nonvolatile content : 20% by mass).
The coating material A-2 was a thermosetting silicone resin solution (“SR2400” manufactured by Toray Dow Corning Co., Ltd., resin: methyl silicone resin, curing start temperature: 185 ° C., nonvolatile content: 50 mass%).
The coating material A-3 is a thermosetting silicone resin (“KR-220L” manufactured by Shin-Etsu Chemical Co., Ltd., resin: methyl silicone resin, curing start temperature: 170 ° C., properties: white solid flakes, nonvolatile content: 100 mass %)Met.
The coating material A-4 was a thermosetting polyamide-imide resin (“COMPOCERAN (registered trademark) H901-2” manufactured by Arakawa Chemical Industries, Ltd., curing start temperature: 240 ° C., nonvolatile content: 30% by mass).
The coating material A-5 is a silicone resin solution (“KR-255” manufactured by Shin-Etsu Chemical Co., Ltd., resin: methylphenyl silicone resin, curing start temperature: 260 ° C. (240 ° C. when a curing agent is added), nonvolatile content : 50% by mass).

In Table 1, “B-1”, “B-5”, and “B-6” were as follows regarding the “material” of each of the first coat layer and the second coat layer. Specifically, each of the coating materials B-1, B-5, and B-6 was a mixture of a silicone resin and its curing agent. The curing agent acts to promote the curing of the silicone resin. The curing agent was tetrabutyl orthotitanate (manufactured by Tokyo Chemical Industry Co., Ltd.). The amount of the curing agent was set to an amount that would be 0.5% by mass with respect to the mass of the silicone resin (specifically, the solid content of the silicone resin).
The coating material B-1 was a mixture of the above-described coating material A-1 and a curing agent (tetrabutyl orthotitanate).
The coating material B-5 was a mixture of the above-described coating material A-5 and a curing agent (tetrabutyl orthotitanate).
The coating material B-6 was a mixture of the coating material A-6 and a curing agent (tetrabutyl orthotitanate). The coating material A-6 is a thermosetting silicone resin (“RSN-0233” manufactured by Toray Dow Corning Co., Ltd., resin: methylphenyl silicone resin, curing start temperature: 225 ° C. (but 210 ° C. when a curing agent is added), Properties: flake, nonvolatile content: 99% by mass).

  Hereinafter, the production methods, evaluation methods, and evaluation results of the carriers CA-1 to CA-7 and CB-1 to CB-7 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.

[Production of toner]
(Preparation of toner base particles)
Using an FM mixer (manufactured by Nippon Coke Industries Co., Ltd.), 100 parts by mass of a polyester resin (“XPE258” manufactured by Mitsui Chemicals, Inc.) and polypropylene wax (“Viscol (registered trademark) 660P” manufactured by Sanyo Chemical Industries, Ltd.) 5 Parts by weight, 5 parts by weight of a colorant ("REGAL (registered trademark) 330R" manufactured by Cabot), and 1 part by weight of a quaternary ammonium salt ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Co., Ltd.) Were mixed.

Subsequently, 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.

(External)
Subsequently, external addition was performed on the obtained toner base particles. Specifically, 100 parts by mass of toner base particles, conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd., substrate: TiO ₂ , coating layer: Sb-doped SnO ₂ film, number average primary particle size: 1 part by mass of about 0.36 μm) and hydrophobic silica particles (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd.), content: dry silica particles surface-modified with trimethylsilyl group and amino group, number average 1 (Next particle size: about 12 nm) 0.7 part by mass is mixed on the surface of the toner base particles by using an FM mixer (“FM-10B” manufactured by Nippon Coke Kogyo Co., Ltd.) at a rotational speed of 3500 rpm for 5 minutes. External additives (titanium oxide particles and silica particles) were adhered. Thereafter, the obtained powder was sieved using a 200-mesh (aperture 75 μm) sieve. As a result, a toner containing a large number of toner particles (non-capsule toner particles) was obtained.

[Manufacture of carriers]
In the manufacture of each of the carriers CA-1 to CA-7 and CB-1 to CB-5, materials were prepared as described below, and the first coat and the second coat were performed on the carrier core. In each manufacture of carrier CB-6 and CB-7, preparation of the 2nd coating liquid and 2nd coating were not performed among the following processes. In the production of each of the carriers CB-6 and CB-7, the powder of the first coated particles corresponds to the carrier.

(Preparation of materials)
As the carrier core, an Mn—Mg—Sr ferrite core (“EF-35” manufactured by Powder Tech Co., Ltd., particle size: 35 μm) was prepared. In addition, the coating material shown in “Material” of “First coating layer” in Table 1 was diluted with a solvent to prepare a first coating liquid having a solid content concentration of 10 mass%. For example, in the manufacture of carrier CA-1, the coating material A-1 (SR2431) was diluted with a solvent (toluene) to prepare a first coating liquid having a solid content concentration of 10% by mass. Moreover, the coating material shown in “Material” of “Second coating layer” in Table 1 was diluted with a solvent to prepare a second coating solution having a solid content concentration of 10 mass%. For example, in the manufacture of carrier CA-1, the coating material A-2 (SR2400) was diluted with a solvent (toluene) to prepare a second coating liquid having a solid content concentration of 10% by mass.

(First coat)
The carrier core (powder) was put into a tumbling fluidized coating apparatus (“Multiplex MP-01” manufactured by POWREC Co., Ltd.), and the first coating liquid was sprayed toward the carrier core while flowing the carrier core. The amount of the first coating solution added was such that the thickness of the first coating layer would be the value shown in “Thickness” of “First coating layer” in Table 2. As the amount of the first coating solution added increases, the thickness of the first coating layer tends to increase. For example, in the manufacture of carrier CA-1, the amount is such that a first coat layer having a thickness of 300 nm is formed. Subsequently, the fluidized bed in the tumbling fluidized coating apparatus was subjected to curing treatment under the conditions shown in “curing conditions” of “first coating layer” in Table 1 to cure the first coating liquid. For example, in the manufacture of carrier CA-1, a curing process (specifically, a heat treatment) at a temperature of 220 ° C. was performed for 1 hour. As a result, first coated particles (carrier core covered with the first coated layer) were obtained. In each of the carriers CA-1 to CA-7 and CB-1 to CB-5, the first coat layer covered an area of about 95% of the surface region of the carrier core. In each of the carriers CB-6 and CB-7, the first coat layer covered about 98% of the surface area of the carrier core.

(Second coat)
Subsequently, the second coating liquid was sprayed toward the first coated particles while flowing the first coated particles (powder) using the rolling fluidized coating apparatus. The amount of the second coating solution added was such that the thickness of the second coating layer reached the value shown in “Thickness” of “Second coating layer” in Table 2. As the amount of the second coating solution added increases, the thickness of the second coating layer tends to increase. For example, in the manufacture of carrier CA-1, the amount is set such that a second coat layer having a thickness of 600 nm is formed. Subsequently, the fluidized bed in the rolling fluidized coating apparatus was subjected to a curing treatment under the conditions shown in “Curing conditions” of “Second coating layer” in Table 1 to cure the second coating liquid. For example, in the manufacture of carrier CA-1, a curing process (specifically, a heat treatment) at a temperature of 205 ° C. was performed for 1 hour. In any carrier, the second coat layer covered an area of about 98% of the surface area of the first coat particle.

  As described above, carriers containing a large number of carrier particles (carriers CA-1 to CA-7 and CB-1 to CB-7) were obtained. For each of the obtained carriers CA-1 to CA-7 and CB-1 to CB-7, each of the thickness of the coating layer, the surface adsorption force of the coating layer, and the pencil hardness of the coating layer (only the uppermost layer) Table 2 shows the measurement results.

  For example, in carrier CA-1, the thickness of the first coat layer is 300 nm, the thickness of the second coat layer is 600 nm, the surface adsorption force of the first coat layer is 79 nN, The surface adsorption force was 47 nN, and the pencil hardness of the second coat layer (that is, the uppermost coat layer) was 2H. These measuring methods were as follows.

<Measurement method of surface adsorption force of coat layer>
Carrier (measuring object: any of carriers CA-1 to CA-7 and CB-1 to CB-7) in visible light curable resin ("Aronix (registered trademark) D-800" manufactured by Toagosei Co., Ltd.) After the dispersion, the resin was cured by light irradiation to obtain a cured product. Subsequently, the obtained cured product was processed using a knife and a file to obtain a rectangular plate-shaped flake sample having predetermined dimensions (length: 1 cm, width: 1 cm, thickness: 3 mm). Then, using a cross-section sample preparation device (“Cross Section Polisher (registered trademark) SM-09010” manufactured by JEOL Ltd., processing method: ion beam), the thin piece sample was processed under the following conditions, A cross section was obtained.

(Processing conditions)
・ Ion acceleration voltage: 4.0 kV
-Gas used: Argon (purity: 99.9999% or more, pressure: 0.15 MPa)
・ Processing time: 12 hours

  The surface adsorbing force was measured for the cross section of the carrier particles produced as described above. An SPM probe station (“NanoNaviReal” manufactured by Hitachi High-Tech Science Co., Ltd.) equipped with a scanning probe microscope (SPM) (“Multifunctional Unit AFM5200S” manufactured by Hitachi High-Tech Science Co., Ltd.) was used as the measuring device. Using such a measuring apparatus, measurement was performed under the following conditions.

(SPM measurement conditions)
・ Moveable range of measurement unit (size of sample that can be measured): 100 μm (Small Unit)
Measurement probe: low spring constant silicon cantilever ("OMCL-AC240TS-C3" manufactured by Olympus Corporation, spring constant: 2 N / m, resonance frequency: 70 kHz, back reflection coating material: aluminum)
Measurement mode: SIS-DFM (SIS: sampling intelligent scan, DFM: dynamic force mode)
・ Measurement range (one field of view): 1μm × 1μm
・ Resolution (X data / Y data): 256/256

  Under the environment of temperature 23 ° C. and humidity 50% RH, the measurement range (XY plane: 1 μm × 1 μm) of the surface to be measured is scanned horizontally with a cantilever by the above measurement mode (SIS-DFM) Measurement was performed to obtain a mapping image regarding the surface adsorption force. The AFM force curve is a curve showing the relationship between the distance between the probe (tip end of the cantilever) and the measurement target and the force (deflection amount) acting on the cantilever. From the AFM force curve, the surface adsorption force of the measurement object (force necessary for the cantilever to move away from the surface of the measurement object) is obtained. In the measurement apparatus, the pressing force (deflection signal) of the cantilever is detected by an optical lever method. Specifically, the semiconductor laser device emits laser light toward the back surface of the cantilever, and the position sensor detects the laser light (flex signal) reflected from the back surface of the cantilever.

  Based on the mapping image regarding the surface adsorption force obtained as described above, the surface adsorption force of the region corresponding to each of the first coat layer and the second coat layer in the cross-sectional region of the carrier particles was obtained. For the five carrier particles contained in the carrier (measuring object), the surface adsorption force of ten first coat layers per one was measured, and 50 measurement values were obtained per one measuring object (carrier). Further, for the five carrier particles contained in the carrier (measuring object), the surface adsorption force of 10 second coat layers per one is measured, and 50 measured values are obtained per one measuring object (carrier). It was. For each of the first coat layer and the second coat layer, the arithmetic average of the 50 measurement values obtained as described above is used as the evaluation value of the measurement object (carrier) (the surface adsorption force of the first coat layer, and Surface adsorption force of the second coat layer).

<Method for measuring thickness of coat layer>
The cross section of the carrier particles was obtained in the same manner as the measurement of the surface adsorption force. Then, the cross section of the obtained carrier particle was image | photographed using the transmission electron microscope (TEM) (The JEOL Co., Ltd. product "JSM-6700F"). And the thickness of the coat layer was measured by analyzing a TEM image using image analysis software (“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, and the lengths of four points on the two straight lines intersecting the coat layer were measured. Subsequently, the arithmetic average value of the four measured lengths was taken as the thickness of the coat layer of the carrier particles. The thickness of the coat layer was measured for each of the 20 carrier particles contained in the carrier (measurement object), and the average number of the 20 particles was used as the evaluation value (coat layer thickness) of the carrier (measurement object).

<Method for measuring pencil hardness of coat layer>
The carrier (measuring object: any of carriers CA-1 to CA-7 and CB-1 to CB-7) is subjected to X-ray fluorescence analysis under the following conditions, and X-ray fluorescence spectrum (horizontal axis: energy, vertical axis: Intensity (number of photons)). The measurement element was a characteristic element in the coat layer located in the uppermost layer of the carrier particles. For example, for the coating layer made of silicone resin, the measurement element was Si (silicon). In the carrier having the first coat layer (lower layer) and the second coat layer (upper layer) on the surface of the carrier core (that is, carriers CA-1 to CA-7 and CB-1 to CB-5), the second The coat layer corresponds to “the coat layer positioned at the uppermost layer of the carrier particles”.

(Conditions for X-ray fluorescence analysis)
・ Analyzer: Scanning X-ray fluorescence analyzer (“ZSX” manufactured by Rigaku Corporation)
・ X-ray tube (X-ray source): Rh (Rhodium)
Excitation conditions: tube voltage 50 kV, tube current 50 mA
・ Measurement area (X-ray irradiation range): Diameter 30mm

The peak intensity of the measured element was read from the obtained fluorescent X-ray spectrum. Hereinafter, the peak intensity of the measurement element measured here is referred to as “initial intensity X _A ” (or simply “X _A ”).

  Next, a plurality of types of pencil lead powders having different hardnesses were prepared, and the following stirring test was performed using each of the pencil lead in an environment of a temperature of 23 ° C. and a humidity of 50% RH. . The hardness of each pencil core was HB, F, 1H, 2H, 3H, 4H, 5H, 6H, 7H, and 8H. After pulverizing the material of each pencil core using a mortar, the powder containing only the pencil core having a particle diameter of 20 μm or less was passed through a sieve of 635 mesh (aperture 20 μm) and used for the stirring test. .

(Agitation test)
1 g of carrier (measuring object: any of carriers CA-1 to CA-7 and CB-1 to CB-7) and 0.1 g of a pencil core powder having a predetermined hardness, a sample bottle with a capacity of 5 mL Put it in. Subsequently, the sample bottle was stirred for 48 hours using a shaker mixer (“Turbler (registered trademark) mixer T2F” manufactured by Willy et Bacofen (WAB)).

After the agitation test, the carrier component scraped by the pencil lead and detached from the carrier particles from the contents of the sample bottle is separated from the pencil lead by suction (specifically, suction through a 635 mesh sieve). To obtain a carrier after the stirring test. Subsequently, the carrier after the stirring test was subjected to fluorescent X-ray analysis under the above-described conditions to obtain a fluorescent X-ray spectrum. And the peak intensity of the measurement element was read from the obtained fluorescent X-ray spectrum. Hereinafter, the peak intensity of the measurement element measured here is referred to as “strength after stirring X _B ” (or simply “X _B ”). In the stirring test, the strength X _B after stirring tends to decrease as the amount of the carrier particle coating layer scraped by the pencil core increases.

From the initial strength X _A and the strength after stirring X _B measured as described above, the coating layer scraping amount is calculated based on the formula “coat layer scraping amount = 100 × (X _A −X _B ) / (X _A )”. Asked. A coating layer scraping amount of less than 5% means that the second coat layer of carrier particles is harder than the pencil core used in the stirring test. The hardness of the hardest pencil lead among the hardnesses of the pencil lead whose coat layer scraping amount was less than 5% was taken as the evaluation value (pencil hardness of the coat layer) of the measurement object (carrier). For example, when a 1H hardness pencil lead was used in the stirring test, the coating layer scraping amount was less than 5%. However, when the 2H hardness pencil lead was used in the stirring test, the coating layer scraping amount was 5%. In such a case, the evaluation value (pencil hardness of the coat layer) of the measurement target (carrier) was 1H.

[Evaluation method]
The evaluation method for each sample (carriers CA-1 to CA-7 and CB-1 to CB-7) is as follows.

(Preparation of two-component developer)
100 parts by mass of carrier (evaluation object: any of carriers CA-1 to CA-7 and CB-1 to CB-7) and 8 parts by mass of positively chargeable toner (toner prepared by the above procedure) A two-component developer was prepared by mixing for 30 minutes using a body mixer (“Rocking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd., mixing method: container rotation and shaking method).

(Print life test)
As an evaluation machine, a printer (“FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd.), photosensitive drum: organic photosensitive drum having a single-layer type photosensitive layer, charging device: contact charging type charging roller, photosensitive body cleaning method: cleaning Blade). The two-component developer prepared by the above-described method was put into the developing device of the evaluation machine, and the replenishment toner (toner prepared by the above-described procedure) was put into the toner container of the evaluation machine.

  A printing durability test was performed in which a sample image having a printing rate of 5% was continuously printed on a recording medium (printing paper) on a recording medium (printing paper) using the above-described evaluation machine in an environment of a temperature of 20 ° C. and a humidity of 50% RH.

(Fogging resistance)
Each time 10,000 sheets were printed during the above-mentioned printing durability test, the reflection density of the blank part in the printed paper was measured using a reflection densitometer (“RD-19I” manufactured by X-Rite). And the fog density (FD) was calculated | required based on the following formula.
Fog density = reflection density of blank area-reflection density of unprinted paper

  Further, the highest fog density (maximum fog density) among all fog densities (FD) measured at each timing during the printing durability test (timing for every 10,000 sheets printed) was obtained. When the maximum fog density was 0.020 or less, it was evaluated as ◯ (good), and when it exceeded 0.020, it was evaluated as x (not good).

(Charge amount fluctuation rate after printing durability test)
Immediately after preparing the two-component developer according to the procedure described above, the charge amount (unit: μC / g) of the toner contained in the obtained two-component developer was measured using a Q / m meter (“MODEL 210HS” manufactured by Trek). It measured using. Hereinafter, the measured charge amount is referred to as “initial charge amount E _A ” (or simply “E _A ”).

After the printing durability test described above, the developing device was taken out from the evaluation machine, and the two-component developer was taken out from the developing device. Then, the charge amount (unit: μC / g) of the toner contained in the taken out two-component developer was measured using a Q / m meter (“MODEL 210HS” manufactured by Trek). Hereinafter, the measured charge amount is referred to as “post-print charge amount E _B ” (or simply “E _B ”).

From the initial charge amount E _A and the post-printing charge amount E _B obtained as described above, the charge amount variation rate (unit:%) after the printing time was determined based on the following equation.
Charge amount fluctuation rate after printing durability = 100 × | E _A −E _B | / E _A

If the charge fluctuation rate after printing was less than 15%, it was evaluated as ◯ (good), and if it was 15% or more, it was evaluated as x (not good). In any evaluation of the carrier CA-1~CA-7 and CB-1~CB-7, E _B is smaller than E _A.

[Evaluation results]
Table 3 shows the results of evaluating the fog resistance (maximum fog density) and the charge amount fluctuation rate after printing for each of the carriers CA-1 to CA-7 and CB-1 to CB-7.

  Carriers CA-1 to CA-7 (carriers according to Examples 1 to 7) each had the above-described basic configuration. Specifically, each of the carriers CA-1 to CA-7 includes a plurality of carrier particles each including a carrier core, a first coat layer, and a second coat layer. The first coat layer and the second coat layer covered 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 contained the first thermosetting resin. The second coat layer contained a second thermosetting resin. The surface adsorption force of the first coat layer was 70 nN or more and 100 nN or less (see Table 2). The pencil hardness of the second coat layer was 2H or more and 6H or less (see Table 2).

  As shown in Table 3, each of the carriers CA-1 to CA-7 was able to maintain a sufficient charge imparting property in continuous printing and continuously form high-quality images over a long period of time.

  In the carriers CB-1 and CB-5 (carriers according to Comparative Examples 1 and 5), the first coat layer peeled off during the printing durability test.

  In Carrier CB-2 (carrier according to Comparative Example 2), the adhesion of the carrier particles increased during the printing durability test, and the surface of the carrier particles was contaminated by the external additive detached from the toner particles.

  In the carrier CB-3 (carrier according to Comparative Example 3), the second coat layer was severely worn during the printing durability test.

  In the carrier CB-4 (the carrier according to Comparative Example 4), the second coat layer was worn during the printing durability test, and the charge imparting property of the carrier became insufficient.

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

DESCRIPTION OF SYMBOLS 10 Toner particle 11 Toner mother particle 13 External additive particle 20 Carrier particle 21 Carrier core 22 Coat layer 22a 1st coat layer 22b 2nd coat layer R area | region

Claims (12)

A plurality of carrier particles comprising a carrier core 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 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 contains a first thermosetting resin,
The second coat layer contains a second thermosetting resin,
The surface adsorption force of the first coat layer is 70 nN or more and 100 nN or less,
The carrier for electrostatic latent image development, wherein the pencil hardness of the second coat layer is 2H or more and 6H or less.   The electrostatic latent image developing carrier according to claim 1, wherein the surface adsorption force of the second coat layer is 65 nN or less.   3. The electrostatic latent image developing carrier according to claim 1, wherein a curing start temperature of the first thermosetting resin is 20 ° C. or more higher than a curing start temperature of the second thermosetting resin. The first coat layer contains a silicone resin as the first thermosetting resin, does not contain a curing agent,
The electrostatic latent image developing carrier according to claim 1, wherein the second coat layer contains a silicone resin as the second thermosetting resin and does not contain a curing agent.   The electrostatic latent image developing carrier according to any one of claims 1 to 3, wherein at least one of the first coat layer and the second coat layer contains a curing agent. The first coat layer contains a silicone resin as the first thermosetting resin, does not contain a curing agent,
The electrostatic latent image developing carrier according to claim 5, wherein the second coat layer contains a silicone resin as the second thermosetting resin and a curing agent. The first coat layer contains a silicone resin as the first thermosetting resin, and a curing agent,
The electrostatic latent image developing carrier according to claim 5, wherein the second coat layer contains a silicone resin as the second thermosetting resin and does not contain a curing agent. Each of the first thermosetting resin and the second thermosetting resin is a silicone resin,
The thickness of the first coat layer is not less than 100 nm and not more than 450 nm,
The thickness of the second coat layer is 550 nm or more and 800 nm or less,
The carrier for electrostatic latent image development according to any one of claims 1 to 7, wherein a total thickness of the first coat layer and the second coat layer is 800 nm or more and 1200 nm or less. The first coat layer covers an area of 85% to 98% of the surface area of the carrier core,
The second coat layer covers the entire area exposed from the first coat layer in the surface area of the carrier core and is also present on the first coat layer. Carrier for electrostatic latent image development.   The carrier for developing an electrostatic latent image according to claim 9, wherein the coverage of the second coat layer is 90% or more and 100% or less in terms of area ratio.   The carrier for electrostatic latent image development according to any one of claims 8 to 10, wherein the carrier core is a ferrite particle.   A two-component development comprising the electrostatic latent image developing carrier according to claim 1 and a positively chargeable toner that can be positively charged by friction between the electrostatic latent image developing carrier and the carrier. Agent.

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