JP2018036375A - Two-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously form high-quality images while suppressing supply fogging in continuous printing.SOLUTION: A two-component developer contains a toner and a carrier. The toner contains toner base particles 11, and a plurality of toner particles 10 having a plurality of first resin particles 13a attached onto a surface of the toner base particles 11. The carrier contains carrier base particles, and a plurality of carrier particles 20 having a plurality of second resin particles 23 attached onto a surface of the carrier base particles. A blocking ratio of the first resin particles 13a after pressurization at a temperature of 160°C and a pressure of 0.1 kgf/mmfor 5 minutes is less than 30 mass% in measurement by a mesh with a sieve opening of 75 μm. A blocking ratio of the second resin particles 23 after pressurization at a temperature of 160°C and a pressure of 0.1 kgf/mmfor 5 minutes is 30 mass% or more in measurement by a mesh with a sieve opening of 75 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a two-component developer containing a toner and a carrier.

  Patent Document 1 discloses a technique of dispersing resin fine particles and conductive fine particles in a resin coating layer of carrier particles in a two-component developer.

JP-A-10-198078

  However, with the technology disclosed in Patent Document 1 alone, it is difficult to provide a two-component developer capable of continuously forming high-quality images while suppressing replenishment fog in continuous printing. . Specifically, when the two-component developer described in Patent Document 1 is stirred in the developing device, the external additive of the toner particles is detached from the toner particles, and the detached external additive adheres to the carrier particles. Easy to do. If the toner particle external additive adheres to the carrier particles in the developing device, the charge imparting property of the carrier fluctuates, and the charge amount of the toner becomes excessive or insufficient.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a two-component developer capable of continuously forming a high-quality image while suppressing replenishment fog in continuous printing. And

The two-component developer according to the present invention includes a toner and a carrier. The toner includes a plurality of toner particles each including toner mother particles and a plurality of first resin particles attached to the surface of the toner mother particles. The carrier includes a plurality of carrier particles including carrier mother particles and a plurality of second resin particles attached to the surfaces of the carrier mother particles. The blocking rate of the first resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is less than 30% by mass as measured with a mesh having an opening of 75 μm. The blocking rate of the second resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 30% by mass or more as measured with a mesh having an opening of 75 μm.

  According to the present invention, it is possible to provide a two-component developer capable of continuously forming high-quality images while suppressing replenishment fog in continuous printing.

FIG. 3 is a diagram illustrating a configuration of a two-component developer according to an embodiment of the present invention.

  An embodiment of the present invention will be described. Note that the evaluation results (values indicating the shape or physical properties) of the powder (more specifically, toner base particles, carrier base particles, external additives, toner, carrier, etc.) are not stipulated. It is the number average of values measured for each of the average particles by selecting a considerable number of average particles from the powder.

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. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth) acrylonitrile”.

  The two-component developer according to this embodiment includes a toner and a carrier. The toner and the carrier are each a powder composed of a large number of particles. The toner includes a plurality of toner particles having the configuration described below. The carrier includes a plurality of carrier particles having the configuration described below. The toner contained in the two-component developer according to this embodiment can be used as, for example, a positively chargeable toner. The positively chargeable toner is positively charged by friction with the carrier.

  The two-component developer according to this 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 (charging device and 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, the developing device of the electrophotographic apparatus (specifically, the developing device in which the two-component developer is set) supplies only the toner of the two-component developer to the photosensitive member, and the electrostatic formed on the photosensitive member. Develop the latent image. The toner is charged by friction with the carrier or blade 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. 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 according to this embodiment has the following configuration (hereinafter referred to as a basic configuration).

(Basic configuration of two-component developer)
The two-component developer includes a toner and a carrier. The toner includes a plurality of toner particles including toner mother particles and a plurality of resin particles (hereinafter referred to as first resin particles) attached to the surfaces of the toner mother particles. The carrier includes a plurality of carrier particles including carrier mother particles and a plurality of resin particles (hereinafter referred to as second resin particles) attached to the surfaces of the carrier mother particles. The blocking rate of the first resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is less than 30% by mass as measured with a mesh having an opening of 75 μm. The blocking rate of the second resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 30% by mass or more as measured with a mesh having an opening of 75 μm. In addition, the measuring method of a blocking rate is the same method as the Example mentioned later, or its alternative method.

  Hereinafter, the blocking rate of the resin particles defined by the basic configuration may be simply referred to as the blocking rate of the resin particles, omitting measurement conditions and the like.

  In a general image forming apparatus, the toner remaining on the photosensitive drum is removed by cleaning together with other deposits on the photosensitive drum after the transfer process. For example, in the blade cleaning method, the surface of the photosensitive drum is rubbed with the edge portion of the cleaning blade to scrape and remove the deposits on the photosensitive drum.

  By attaching resin particles (external additives) to the surface of the toner base particles, it is possible to improve the heat resistant storage stability of the toner. In order for the resin particles to function as a spacer between the toner particles, the number average primary particle diameter of the resin particles is preferably 50 nm or more and 100 nm or less. However, the inventors have found that the following problems may occur when resin particles are used as an external additive for toner particles. The inventor has invented a two-component developer having the above-described basic configuration in order to solve these problems.

(First issue)
When toner particles having resin particles as an external additive are used for continuous printing, the inventor has noticed that the resin particles are detached from the toner particles and the detached resin particles adhere to the surface of the photosensitive drum. . When cleaning the surface of the photosensitive drum by the blade cleaning method, the resin particles existing on the surface of the photosensitive drum are sandwiched between the photosensitive drum and the cleaning blade and heated and pressurized by friction. . When the resin particles are thermally compressed by heating and pressing (specifically, plastically deformed) and fixed on the surface of the photosensitive drum, it becomes difficult to form a high-quality image. Specifically, a dash mark (image defect due to a fixed object existing on the surface of the photosensitive drum) easily occurs in the formed image.

  In the above basic configuration, the blocking rate of the resin particles indicates the ease of being thermally compressed. As the blocking rate of the resin particles is larger, the resin particles tend to be thermally compressed. In particular, when the blocking rate of the first resin particles (external additive for toner particles) is 30% by mass or more, when the resin particles are heated and pressurized by blade cleaning, the photosensitive member is contaminated (to the surface of the photosensitive drum). There is a tendency that the resin particles are easily fixed). In order to make the blocking rate of the first resin particles less than 30% by mass, it is considered necessary to produce very hard resin particles. The inventor succeeded in setting the blocking rate of the first resin particles to less than 30% by mass by using a high purity crosslinking agent. For example, when divinylbenzene is used as a crosslinking agent, divinylbenzene having a purity (mass fraction) of about 50% is generally used, but divinylbenzene having a purity (mass fraction) of 80% is used. Thus, the blocking rate of the first resin particles was successfully reduced to less than 30% by mass. The blocking rate of the resin particles can be adjusted, for example, by changing the amount of the crosslinking agent added during resin synthesis.

(Second problem)
In a general image forming apparatus, a two-component developer (toner and carrier) is used while being stirred in the developing apparatus. When the external additive of the toner particles is detached from the toner particles by stirring, the detached external additive may adhere to the carrier particles. When the external additive of toner particles adheres to the carrier particles in the developing device, the charge imparting property of the carrier fluctuates and the charge amount of the toner tends to become excessive or insufficient.

  In the two-component developer having the basic structure described above, the blocking rate of the first resin particles (external additive for toner particles) is less than 30% by mass. Such first resin particles have a weak adhesion to the surface of the toner base particles and tend to be detached from the toner particles. However, in the two-component developer having the basic configuration described above, the second resin particles (external additives for carrier particles) are attached to the surface of the carrier base particles. Moreover, the blocking rate of the second resin particles is 30% by mass or more. Such second resin particles have a strong adhesion to the surface of the carrier base particles and tend to be difficult to be detached from the carrier particles. Second resin particles are present on the surface of the carrier base particles. Specifically, the second resin particles protrude from the surface of the carrier base particles. This makes it difficult for the first resin particles detached from the toner particles to adhere to the surface of the carrier base particles. In the developing device, the first resin particles (external additive for toner particles) are difficult to move from the toner particles to the carrier particles. Further, since the second resin particles are present on the surface of the carrier base particles from the beginning, even if the external additive moves from the toner particles to the carrier particles, it is considered that there is little fluctuation in the charge imparting property of the carrier. . For this reason, in the two-component developer having the basic configuration described above, toner charging failure is unlikely to occur. By using such a two-component developer, it is possible to suppress replenishment fog (fog caused due to toner charging failure when a large amount of toner is replenished into the developing device) in continuous printing.

  As described above, by using the two-component developer having the above-described basic configuration, in continuous printing, a high-quality image (continuously suppressed while suppressing sticking of foreign matter to the photoreceptor and replenishment fogging). In detail, it is possible to continue forming an image without a dash mark.

In continuous printing, in order to continue to form high-quality images while suppressing sticking of foreign matters to the photoreceptor and replenishment fog, the first resin in the two-component developer having the above-described basic configuration is used. The blocking rate of the particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 5% by mass or more and 20% by mass or less as measured with a mesh having an opening of 75 μm. The blocking rate after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is particularly preferably 50% by mass or more and 90% by mass or less as measured with a mesh having an opening of 75 μm. In order for the first resin particles and the second resin particles to function suitably, the amount of the first resin particles is 0.50 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the toner base particles, The amount of the second resin particles is preferably 0.05 parts by mass or more and 0.30 parts by mass or less with respect to 100 parts by mass of the carrier base particles.

  In order to suppress the fluctuation in charge imparting property of the carrier when the external additive moves from the toner particles to the carrier particles, the first resin particles (toner external additive: toner particle external additive) and It is preferable that the second resin particles (carrier external additive: carrier particle external additive) have the same physical properties (or close physical properties). For example, the difference between the number average primary particle diameter of the first resin particles and the number average primary particle diameter of the second resin particles is preferably 10 nm or less in absolute value. Moreover, it is preferable that a 1st resin particle and a 2nd resin particle are mutually comprised with the same kind of resin.

  For example, it is preferable that the first resin particles and the second resin particles each contain a crosslinked styrene-acrylic acid resin. The cross-linked styrene-acrylic acid resin is excellent in chargeability, and it is easier to produce fine particles having a uniform shape and dimensions than a melamine resin or the like. The crosslinked styrene-acrylic acid resin has good durability and charging stability. Regarding charging stability, a decrease in charge amount is suppressed particularly in a high-temperature and high-humidity environment.

  The crosslinked styrene-acrylic acid resin is a polymer of one or more styrene monomers, one or more acrylic acid monomers, and a crosslinking agent. In order to synthesize a crosslinked styrene-acrylic acid resin, for example, a styrene monomer, an acrylic acid monomer, and a crosslinking agent as shown below can be suitably used.

  Preferable examples of the styrene monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), p-hydroxy styrene, m-hydroxy styrene. , Vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

  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.

As the cross-linking agent, a compound having two or more unsaturated bonds is preferable, a monocyclic compound (more specifically, divinylbenzene or the like) having two or more functional groups having an unsaturated bond, or each unsaturated compound. A condensate (more specifically, ethylene glycol dimethacrylate, etc.) of two or more monovalent carboxylic acids having a functional group having a bond and one polyhydric alcohol is particularly preferable. Examples of the functional group having an unsaturated bond include a vinyl group (CH ₂ ═CH—) or a functional group in which hydrogen in the vinyl group is substituted.

  In order for the two-component developer to have the above-described basic configuration, the first resin particles have a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms in the ester portion (hereinafter referred to as the first (meth)). An acrylic acid alkyl ester), a styrene monomer (hereinafter referred to as a first styrene monomer), a crosslinking agent having two or more unsaturated bonds (hereinafter referred to as a first crosslinking agent), and (Meth) acrylic acid alkyl ester having a polymer having an alkyl group having 1 to 4 carbon atoms in the ester part, containing a polymer (hereinafter referred to as a first crosslinked styrene-acrylic acid resin). (Hereinafter referred to as a second (meth) acrylic acid alkyl ester), a styrene monomer (hereinafter referred to as a second styrene monomer), and a bridge having two or more unsaturated bonds Agent (hereinafter, second to as crosslinking agent) polymer of (hereinafter, second crosslinked styrene - referred to as acrylic resin) is preferably contained.

  In the first preferred example of the combination of the first resin particles and the second resin particles, the crosslinked styrene-acrylic acid resin contained in the first resin particles and the crosslinked styrene-acrylic contained in the second resin particles. The acid resin is composed of the same type of monomer and the same type of cross-linking agent and has different cross-linking degrees. For example, in the combination of the first crosslinked styrene-acrylic resin and the second crosslinked styrene-acrylic resin, the first (meth) acrylic acid alkyl ester and the second (meth) acrylic acid alkyl ester are respectively It is butyl methacrylate, the first styrene monomer and the second styrene monomer are each styrene, and the first crosslinking agent and the second crosslinking agent are each divinylbenzene, or ethylene glycol dimethacrylate, respectively. It is preferable that Based on the difference in the degree of cross-linking between the first resin particles and the second resin particles, the blocking rate of the first resin particles (external additives for toner particles) is relatively low, and the second resin particles (outside of the carrier particles). The blocking rate of the additive) can be made relatively high. In addition, the crosslinking degree (for example, crosslinking density) of resin can be adjusted based on the addition amount of a crosslinking agent.

  In a second preferred example of the combination of the first resin particles and the second resin particles, a crosslinked styrene-acrylic acid resin contained in the first resin particles and a crosslinked styrene-acrylic contained in the second resin particles. The acid resin is crosslinked with different crosslinking agents. For example, in the combination of the first crosslinked styrene-acrylic acid resin and the second crosslinked styrene-acrylic acid resin, the first crosslinking agent is divinylbenzene and the second crosslinking agent is ethylene glycol dimethacrylate. Is preferred. Based on the difference in the crosslinking agent between the first resin particles and the second resin particles, the blocking rate of the first resin particles (the external additive of the toner particles) is relatively low, and the second resin particles (outside the carrier particles). The blocking rate of the additive) can be made relatively high.

  In order to appropriately attach the second resin particles to the surface of the carrier base particles, the carrier base particles preferably include a carrier core and a coat layer that covers the surface of the carrier core. In addition, in order to obtain a two-component developer suitable for image formation, inorganic particles are attached to the surface of the toner base particles in addition to the first resin particles, and the inorganic particles are attached to the surface of the carrier base particles. Is preferably not externally added. Adhering inorganic particles to the surface of the toner base particles makes it easy to ensure sufficient toner fluidity. Also, it is possible to impart abrasiveness to the toner particles by attaching titanium oxide particles to the surface of the toner base particles. In addition, since no inorganic particles are externally added to the surface of the carrier base particles, fluctuations in charge imparting properties of the carrier can be suppressed. It should be noted that the inorganic particles released from the toner particles by mixing the toner and the carrier during the production of the two-component developer (the toner particle external additive) adhere to the surface of the carrier mother particles. It does not fall under “inorganic particles are externally added to the surface of the particles”. In the two-component developer, it is considered that the inorganic particles detached from the toner particles are not integrated (bonded) with the carrier mother particles and are easily separated from the carrier mother particles on the surface of the carrier mother particles. “The inorganic particles are externally added to the surface of the carrier mother particles” means that the carrier particles are integrated (bonded) with the carrier mother particles at least in a stationary state (a state where no stress is applied). It means a state in which inorganic particles are stably held on the surface.

  Unlike the internal additive, the external additive is not present inside the mother particle and is selectively present only on the surface of the mother particle. In the external addition step, for example, the base particles (powder) and the external additive (powder) are stirred together so that the external additive particles can be attached to the surface of the base particles. By stirring, the external additive particles are integrated with the base particles, and the external additive particles are stably held on the surface of the base particles. The mother 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 mother particles and the external additive particles is determined based on the mixing conditions (more specifically, the mixing time, the rotational speed of stirring, etc.), the particle diameter of the external additive particles, the shape of the external additive particles, It can be adjusted by the hardness of the external additive particles, the surface state of the external additive particles, and the like. In order to suppress detachment of the external additive particles, it is preferable that the external additive particles are strongly bonded to the surface of the mother particle. The external additive particles may be fixed on the surface of the mother particle by mechanical bonding by embedding. For example, for external additive particles having a large particle size, the mother particles and the external additive are vigorously stirred to embed a part (bottom part) of the external additive particles in the surface layer of the mother particle. External additive particles can be fixed on the surface. However, if the particle diameter of the external additive particles is too large, it is difficult to fix the external additive particles on the surface of the mother particles. In order to improve the fluidity of the toner or carrier by the external additive particles, the external additive particles are weakly bonded to the surface of the base particles (for example, spherical external additive particles having a small particle diameter are It is preferable that it is attached to the surface of the mother particle in a rotatable state. The external additive particles (for example, silica particles) for improving the fluidity of the toner or carrier are preferably attached to the surface of the base particles mainly by van der Waals force or electrostatic force.

  Hereinafter, an example of a two-component developer having the above-described basic configuration will be described with reference to FIG.

The two-component developer shown in FIG. 1 includes toner (powder of toner particles 10) and carrier (powder of carrier particles 20). The toner includes a plurality of toner particles 10 including toner base particles 11, a plurality of first resin particles 13a, and a plurality of inorganic particles 13b (for example, silica particles). The plurality of first resin particles 13 a and the plurality of inorganic particles 13 b are respectively attached to the surface of the toner base particles 11. The carrier includes a plurality of carrier particles 20 including carrier base particles (carrier core 21 and coat layer 22) and a plurality of second resin particles 23. The carrier mother particles include a carrier core 21 and a coat layer 22 that covers the surface of the carrier core 21. The coat layer 22 may cover the entire surface of the carrier core 21 or may partially cover the surface region of the carrier core 21. However, in order to ensure sufficient carrier chargeability and durability, it is preferable that the coat layer 22 completely covers the entire surface of the carrier core 21 (with a covering area ratio of 100%). Each of the plurality of second resin particles 23 is attached to the surface of the carrier base particle. The blocking rate of the first resin particles 13a after pressurization for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is less than 30% by mass as measured with a mesh having an opening of 75 μm. The blocking rate of the second resin particles 23 after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 30% by mass or more as measured with a mesh having an opening of 75 μm.

  The toner particles contained in the toner may be toner particles in which the toner base particles do not have a shell layer (hereinafter referred to as non-capsule toner particles), or toner particles in which the toner base particles have a shell layer (hereinafter referred to as “non-capsule toner particles”). (It is described as capsule toner particles). Capsule toner particles can be produced by forming a shell layer on the surface of toner base particles (toner core) of non-capsule toner particles. 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 a binder resin, a release agent, a charge control agent, and a colorant until a desired particle size is obtained. Thereby, aggregated particles containing a binder resin, a release agent, a charge control agent, and a 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 one 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. In the case of capsule toner particles, toner base particles in the non-capsule toner particles shown below may be used as the toner core.

[Toner mother particles]
The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, a colorant, a release agent, a charge control agent, and a magnetic powder).

(Binder resin)
In the toner base particles, generally, the binder resin occupies most 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.

  Preferable examples of the binder resin include a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), an olefin resin (more specifically, polyethylene). Resin or polypropylene resin), vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, polyester resin, polyamide resin, or urethane resin. Further, a copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is used. May be.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner base particles preferably contain at least one of a polyester resin and a styrene-acrylic acid resin, and particularly preferably contain a polyester resin. .

  The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diols, bisphenols, trihydric or higher alcohols, etc. as shown below) and one or more polyhydric carboxylic acids ( More specifically, it can be obtained by polycondensation with a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below. The polyester resin may contain a repeating unit derived from another monomer (a monomer that is neither a polyhydric alcohol nor a polyvalent carboxylic acid).

  Preferred examples of the aliphatic diols include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol (more specifically, ethylene glycol, 1,3-propanediol. 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, or 1,12-dodecanediol Etc.), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

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

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

  Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acid (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acid (more specifically, malonic acid). Succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decanedicarboxylic acid), alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid) Acid, n-dodecyl succinic acid, or isododecyl succinic acid), alkenyl succinic acid (specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isodode) Senylsuccinic acid, etc.), maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, or cyclohexanedicarboxylic acid Examples include acids.

  Preferred 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, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

(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 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. Vat yellow can be preferably 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) can be preferably used.

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

(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.

[Toner external additive]
In the two-component developer having the basic configuration described above, a toner external additive (specifically, a powder containing a plurality of external additive particles) is attached to the surface of the toner base particles. The toner particles include a plurality of first resin particles as a toner external additive. For example, the toner base particles (powder) and the external additive (powder) are stirred together so that a part (bottom part) of the external additive particles (for example, the first resin particles) is the surface layer of the toner base particles. The external additive particles adhere to the surface of the toner base particles by physical force and are physically bonded.

  Examples of the first resin particles (toner external additives) include a crosslinked styrene resin, a crosslinked acrylic acid resin, a crosslinked styrene-acrylic acid resin, a crosslinked polyester resin, a crosslinked urethane resin, a crosslinked polyacrylamide resin, and a crosslinked polyacrylonitrile resin. Resin particles containing one or more resins selected from the group consisting of the above are preferred, and resin particles containing a crosslinked styrene-acrylic acid resin are particularly preferred.

  In addition to the first resin particles, inorganic particles may adhere to the surface of the toner base particles. As inorganic particles (toner external additive), particles of silica particles or metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are preferable. Particularly preferred is one or more particles selected from the group consisting of silica particles and titanium oxide particles.

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. As the silane coupling agent, a silane compound (more specifically, methyltrimethoxysilane, aminosilane or the like) may be used, or a silazane compound (more specifically, HMDS (hexamethyldisilazane) or the like). May be used. When the surface of the silica substrate (untreated silica particles) is treated with the surface treatment agent, a large number of hydroxyl groups (—OH) present on the surface of the silica substrate are partially or entirely derived from the surface treatment agent. Substituted with a functional group. As a result, silica particles having a functional group derived from the surface treating agent (specifically, a functional group that is more hydrophobic and / or positively charged than the hydroxyl group) on the surface can be obtained. For example, when the surface of a silica substrate is treated with a silane coupling agent having an amino group, a hydroxyl group of the silane coupling agent (for example, a hydroxyl group generated by hydrolysis of an alkoxy group of the silane coupling agent with moisture) A dehydration condensation reaction (“A (silica substrate) —OH” + “B (coupling agent) —OH” → “A—O—B” + H ₂ O) occurs with a hydroxyl group present on the surface of the silica substrate. By such a reaction, a silane coupling agent having an amino group is chemically bonded to silica, whereby an amino group is imparted to the surface of the silica particles. More specifically, the hydroxyl group present on the surface of the silica substrate is substituted with a functional group having an amino group at the end (more specifically, —O—Si— (CH ₂ ) ₃ —NH ₂ or the like). Silica particles provided with amino groups tend to have a stronger positive charge than a silica substrate (untreated silica particles). When a silane coupling agent having an alkyl group is used, a hydroxyl group present on the surface of the silica substrate is converted into a functional group having an alkyl group at the end (more specifically,- it can be replaced by O-Si-CH _3, etc.). Thus, silica particles to which a hydrophobic group (alkyl group) is added instead of a hydrophilic group (hydroxyl group) tend to have stronger hydrophobicity than a silica substrate (untreated silica particles).

[Carrier mother particles]
The carrier base particles may be carrier base particles (for example, ferrite carrier particles) that do not include a coat layer, or may be carrier base particles (hereinafter referred to as coated carrier particles) that include a coat layer. In order to form a high-quality image over a long period of time using a two-component developer, it is preferable to use coated carrier particles. The coated carrier particles include a carrier core and a coat layer that covers the surface of the carrier core. In order to ensure sufficient carrier chargeability and durability, the coat layer preferably covers 90% or more of the surface area of the carrier core, and covers 100% of the area. It is particularly preferred.

  Hereinafter, suitable examples of the coated carrier particles will be described. In addition, you may use the carrier core which has the following structure as carrier mother particle as it is, without covering with a coating layer.

(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 magnetite, barium ferrite, maghemite, Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Ca—Mg ferrite, Li ferrite, and Cu—Zn ferrite. Iron oxide is preferred. 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.

(Coat layer)
The coat layer is formed on the surface of the carrier core so as to cover the carrier core. The coat layer is substantially composed of a resin. Additives may be dispersed in the resin constituting the coat layer. Examples of the method for forming the coat layer include a method of immersing the carrier core in a liquid containing a resin (or resin material), or a liquid containing a resin (or resin material) in the carrier core in the fluidized bed. The method of spraying is mentioned.

  The resin constituting the coat layer is preferably at least one resin selected from the group consisting of a fluororesin, a silicone resin, a polyamideimide resin, and a polyimide resin. Further, in order to reduce the adhesion (easiness of adhesion) of the carrier base particles, the coating layer is one or more kinds of resins selected from the group consisting of polyamideimide resin (PAI) and polyimide resin (PI); It is particularly preferable to contain a fluororesin. Examples of the fluororesin contained in the coating layer include polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polytrifluoroethylene (more specifically, polychlorotrifluoroethylene, etc.), polyhexafluoropropylene. One or more resins selected from the group consisting of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) are preferred, and FEP or PFA is particularly preferred preferable.

[Carrier external additive]
In the two-component developer having the basic structure described above, an external additive (specifically, a powder containing a plurality of external additive particles) adheres to the surface of the carrier base particles. The carrier particles include a plurality of second resin particles as a carrier external additive. For example, by stirring together the carrier base particles (powder) and the external additive (powder), a part (bottom part) of the external additive particles (for example, the second resin particles) is the surface layer of the carrier base particles. The external additive particles adhere to the surface of the carrier mother particles by physical force (physical bonding).

  Examples of the second resin particles (carrier external additive) include a crosslinked styrene resin, a crosslinked acrylic acid resin, a crosslinked styrene-acrylic acid resin, a crosslinked polyester resin, a crosslinked urethane resin, a crosslinked polyacrylamide resin, and a crosslinked polyacrylonitrile resin. Resin particles containing one or more resins selected from the group consisting of the above are preferred, and resin particles containing a crosslinked styrene-acrylic acid resin are particularly preferred.

  Examples of the present invention will be described. Table 1 shows developers DA-1 to DA-5 and DB-1 to DB-5 (two-component developers for electrostatic latent image development, respectively) according to Examples or Comparative Examples. Table 2 shows external additives (resin particles S-1 to S-6) used in the production of each developer shown in Table 1.

In Table 2, the meanings of items indicating resin raw materials are as follows.
(monomer)
BMA: n-butyl methacrylate MMA: methyl methacrylate S: styrene (crosslinking agent)
DVB: Divinylbenzene EGDMA: Ethylene glycol dimethacrylate

  Hereinafter, the production methods, evaluation methods, and evaluation results of developers DA-1 to DA-5 and DB-1 to DB-5 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.

[Preparation of materials]
(Preparation of resin particles S-1 to S-6)
In a 4-liter flask having a capacity of 1 L equipped with a stirrer, a cooling tube, a thermometer, and a nitrogen introduction tube, 600 g of ion-exchanged water, 6 g of emulsifier (DBS: sodium dodecylbenzenesulfonate), and an initiator (BPO: Benzoyl peroxide) 15 g and the raw materials of the types and amounts shown in Table 2 were added. For example, in the preparation of resin particles S-1, 100 g of n-butyl methacrylate (BMA), 95 g of styrene (S), and 5 g of divinylbenzene (DVB) were added as resin raw materials. In the preparation of the resin particles S-5, 100 g of methyl methacrylate (MMA), 95 g of styrene (S), and 5 g of divinylbenzene (DVB) were added as resin raw materials. In the preparation of resin particles S-6, 60 g of n-butyl methacrylate (BMA), 60 g of styrene (S), and 80 g of ethylene glycol dimethacrylate (EGDMA) were added as resin raw materials. In addition, in each preparation of resin particles S-1 to S-5, the purity (mass fraction) of divinylbenzene (DVB) used as a crosslinking agent was 80%. In the preparation of the resin particle S-6, the purity (mass fraction) of ethylene glycol dimethacrylate (EGDMA) used as a crosslinking agent was 97%.

  Subsequently, while stirring the contents of the flask, nitrogen gas was introduced into the flask to create a nitrogen atmosphere inside the flask. Further, while stirring the flask contents, the temperature of the flask contents is increased to 90 ° C. in a nitrogen atmosphere, and the flask contents are reacted for 3 hours (specifically, a polymerization reaction) in a nitrogen atmosphere and a temperature of 90 ° C. It was. As a result, an emulsion containing a reaction product having a number average primary particle diameter of 90 nm was obtained. Subsequently, the obtained emulsion was cooled, and resin particles S-1 to S-6 (respectively powders) were obtained through a washing step and a dehydration step. Each of the resin particles S-1 to S-6 was substantially composed of a crosslinked styrene-acrylic acid resin. The number average primary particle diameter of each of the resin particles S-1 to S-6 was as shown in “Particle diameter” in Table 2. A scanning electron microscope (SEM) was used to measure the number average primary particle diameter of the resin particles.

[Production of toner]
(Preparation of toner mother particles)
Non-capsule toner particles (binder resin: polyester resin, release agent: ester wax (“Nissan Electol (registered trademark) WEP-3” manufactured by NOF Corporation)), colorant: carbon black (Mitsubishi) “MA100” manufactured by Chemical Co., Ltd.), charge control agent: quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Industries, Ltd.), volume median diameter (D ₅₀ ): 7.0 μm) Got ready.

(External toner addition)
Using a multi-purpose small mixing and grinding machine (“Multipurpose mixer” manufactured by Nippon Coke Industries, Ltd., blade rotation speed (maximum): 10,000 rpm), 100 parts by mass of toner mother particles prepared as described above, and silica particles (surface treatment) : Methyl hydrogen polysiloxane (“KF-99P” manufactured by Shin-Etsu Chemical Co., Ltd.) and 3-aminopropyltriethoxysilane (“KBE-903” manufactured by Shin-Etsu Chemical Co., Ltd.), number average primary particle size: 16 nm, BET specific surface area: about 130 m ² / g) 2 parts by mass and external additives shown in “First resin particles” in Table 1 (resin particles S-1 to S-4 and S defined for each developer) Any of -6) 1 part by mass was mixed for 10 minutes. For example, in the production of toner for developer DA-1, resin particles S-4 were used as an external additive in addition to the silica particles. In the production of the toner for developer DA-2, resin particles S-3 were used as an external additive in addition to the silica particles. Further, in the production of the developer DB-5 toner, only the above silica particles were used as an external additive.

For each toner obtained as described above, the blocking rate of resin particles (external additive) (specifically, after pressurizing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² , a mesh having an opening of 75 μm) Table 1 shows the measurement results of the blocking rate measured by the above. For example, the blocking rate of the resin particles (external additive) in the toner for developer DA-1 was 14%. The method for measuring the blocking rate was as follows. The developer DB-5 toner was excluded from the measurement target because it did not include resin particles as an external additive.

<Measurement method of blocking rate>
A commercially available synthetic detergent (concentration 7 mass% alkyl ether sulfate sodium aqueous solution: “Mypet (registered trademark)” manufactured by Kao Corporation) diluted 10 times with water to prepare a surfactant aqueous solution, and its surface activity In 500 mL of the aqueous agent solution, 10 g of the measurement target (toner) was dispersed to obtain a toner dispersion.

  Subsequently, the obtained toner dispersion was subjected to ultrasonic treatment using an ultrasonic disperser (“Ultrasonic Miniwelder P128” manufactured by Ultrasonic Industrial Co., Ltd., output: 100 W, oscillation frequency: 28 kHz), and toner mother The particles and external additives (silica particles and resin particles) were separated. The resin particles (external additive) were any of the aforementioned resin particles S-1 to S-4 and S-6.

  Subsequently, the ultrasonically treated toner dispersion was subjected to suction filtration using a qualitative filter paper (“Whatman (registered trademark) grade 3” manufactured by Whatman, particle retention capacity: 6 μm). Then, after performing reslurry to add ion-exchanged water, suction filtration with the qualitative filter paper is performed again, and a filtrate (specifically, cloudy liquid) containing external additives (silica particles and resin particles) separated from the toner particles is obtained. Obtained. Subsequently, the obtained filtrate was subjected to a centrifugation treatment at a rotational speed of 3000 rpm for 1 minute using a centrifuge, and silica particles heavier (higher in density) than the resin particles were precipitated out of the external additive. . Thereafter, the supernatant liquid containing the resin particles (external additive) was collected, and wet cake-like resin particles were obtained by pressure filtration. Subsequently, the obtained wet cake-like resin particles were vacuum-dried. The separation operation as described above is repeated until the recovered amount of resin particles separated from the toner particles (specifically, dried resin particles) reaches 10 mg to obtain 10 mg of toner separated particles (resin particles separated from the toner particles). It was.

  As a measuring jig, a base (material: SUS304) in which a cylindrical hole (diameter: 10 mm, depth: 10 mm) is formed, a cylindrical indenter (diameter: 10 mm, material: SUS304), and a heater The equipment provided (Kyocera Document Solutions Co., Ltd.) was used. Note that SUS304 is an iron-chromium-nickel alloy (austenitic stainless steel) having a nickel content of 8% by mass and a chromium content of 18% by mass.

Under an environment of a temperature of 23 ° C. and a humidity of 50% RH, 10 mg of the toner separation particles (resin particles separated from the toner particles) obtained in the above-described procedure were put into the hole (measurement site) of the jig. The measurement site was heated to 160 ° C. with a jig heater, and a pressure of 0.1 kgf / mm ² was applied to the measurement site (resin particles) with a jig indenter (load: about 100 N) for 5 minutes. Thereafter, the entire amount of the resin particles at the measurement site (in the hole) was collected and set on a sieve (200 mesh defined by JIS Z8801-1) having a mesh size of 75 μm. And the mass of the sieve containing resin particles was measured, and the mass of resin particles on the sieve (the mass of resin particles before suction) was determined.

Subsequently, using a suction machine (“V-3SDR” manufactured by Amano Co., Ltd.), resin particles on the sieve were sucked from the lower side of the sieve. By this suction, only non-blocking resin particles out of the resin particles on the sieve passed through the sieve. After the suction, the mass of the resin particles that did not pass through the sieve (resin particles remaining on the sieve) was measured. Based on the mass of the resin particles before suction and the mass of the resin particles after suction (the mass of the resin particles that did not pass through the sieve), the blocking rate (unit: mass%) was determined according to the following formula. .
Blocking rate = 100 × mass of resin particles after suction / mass of resin particles before suction

[Manufacture of carriers]
(Preparation of carrier mother particles)
As carrier base particles, coated carrier particles (carrier core: Mn—Mg—Sr ferrite core (“EF-50” manufactured by Powder Tech Co., Ltd.)), coating layer: silicone polymer (manufactured by Toray Dow Corning Co., Ltd.), volume-medium A diameter (D ₅₀ ): 50 μm) was prepared. In the production of the developer DB-5 carrier, the prepared carrier base particles (powder) were used as they were as the carrier for the developer DB-5 without performing the following “external carrier addition”.

(External career)
Using a multi-purpose small mixing and grinding machine (“Multipurpose mixer” manufactured by Nippon Coke Industries, Ltd., blade rotation speed (maximum): 10,000 rpm), 100 parts by mass of carrier base particles prepared as described above, “ 0.1 part by mass of an external additive (any one of the resin particles S-1 to S-5 determined for each developer) shown in “second resin particles” was mixed for 5 minutes. For example, in the production of the carrier for developer DA-1, resin particle S-1 was used as an external additive. Further, in the production of the carrier for developer DA-3, resin particles S-2 were used as an external additive.

[Preparation of two-component developer]
10 parts by weight of the toner manufactured by the above procedure (as shown in Table 1), and the carrier manufactured by the above procedure (as shown in Table 1) 100 parts by mass of the defined carrier) were mixed for 30 minutes using a ball mill to obtain developers DA-1 to DA-5 and DB-1 to DB-5 (each two-component developer).

[Evaluation method]
The evaluation method of each sample (Developers DA-1 to DA-5 and DB-1 to DB-5) is as follows.

(Dash mark resistance, replenishment fog resistance)
A multifunction machine (“TASKalfa 5550ci” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. A sample (evaluation object: any one of developers DA-1 to DA-5 and DB-1 to DB-5) is put into the developing device of the evaluation machine, and toner corresponding to the sample (developer) (replenishment toner) Was put into the toner container of the evaluation machine.

  In the environment of temperature 24 ° C. and humidity 60% RH, a first press life test was performed in which continuous printing was performed on 100,000 sheets of paper (A4 size plain paper) at a printing rate of 5% using the evaluation machine. . During the first printing durability test, every time 1000 sheets were printed, the formed image was visually observed to confirm the presence or absence of a dash mark. When the dash mark is confirmed, the cumulative number of printed sheets at the time when the dash mark is confirmed is used as the evaluation value of the sample (developer). If the dash mark is not confirmed in the first printing test for 100,000 sheets, it is evaluated as ◎ (very good), and if the accumulated number of printed sheets at the time when the dash mark is confirmed is 80,000 or more, it is good (good) If the cumulative number of printed sheets at the time when the dash mark was confirmed was less than 80,000, it was evaluated as x (bad).

  In addition, after the first printing durability test, in the environment of a temperature of 24 ° C. and a humidity of 60% RH, the above-mentioned evaluation machine is used to perform blank paper printing continuously on 1000 sheets of paper (A4 size printing paper). Subsequently, a second press life test was performed in which continuous printing was performed on 100 sheets of paper (A4 size plain paper) at a printing rate of 20%. During the second printing durability test, the fog density (FD) was measured for each of the 100 printed sheets. The largest value among the 100 measured values was used as the evaluation value (fogging density) of the sample (toner). For the measurement of fog density (FD), a fully automatic whiteness meter (“TC-6MC” manufactured by Tokyo Denshoku Co., Ltd.) was used. When the fog density (FD) was 0.010 or less, it was evaluated as ◯ (good), and when the fog density (FD) exceeded 0.010, it was evaluated as x (not good). The fog density (FD) corresponds to a value obtained by subtracting the reflection density of the base paper (unprinted paper) from the reflection density of the blank portion of the evaluation paper after printing.

[Evaluation results]
For each of the developers DA-1 to DA-5 and DB-1 to DB-5, the dash mark resistance (the presence or absence of a dash mark, or the cumulative number of printed sheets when the dash mark is confirmed), and the replenishment fogging resistance The results of evaluating the property (fogging density) are shown in Table 3.

Developers DA-1 to DA-5 (two-component developers according to Examples 1 to 5) each had the basic configuration described above. Specifically, in each of developers DA-1 to DA-5, the toner includes a plurality of toner particles each including toner base particles and a plurality of first resin particles attached to the surfaces of the toner base particles. In addition, the carrier includes a plurality of carrier particles including carrier mother particles and a plurality of second resin particles attached to the surfaces of the carrier mother particles. The blocking rate of the first resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² was less than 30% by mass as measured with a mesh having an opening of 75 μm (see Table 1). The blocking rate of the second resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² was 30% by mass or more as measured with a mesh having an opening of 75 μm (see Table 1).

  As shown in Table 3, each of the developers DA-1 to DA-5 was able to continuously form high-quality images while suppressing replenishment fog in continuous printing.

  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 13a 1st resin particle 13b Inorganic particle 20 Carrier particle 21 Carrier core 22 Coat layer 23 2nd resin particle

Claims (10)

A two-component developer comprising a toner and a carrier,
The toner includes a plurality of toner particles each including toner mother particles and a plurality of first resin particles attached to the surfaces of the toner mother particles,
The carrier includes a plurality of carrier particles comprising carrier mother particles and a plurality of second resin particles attached to the surfaces of the carrier mother particles, respectively.
The blocking rate of the first resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is less than 30% by mass as measured with a mesh having an opening of 75 μm,
A two-component developer in which the blocking rate of the second resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 30% by mass or more as measured with a mesh having an opening of 75 μm. The blocking rate of the first resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 5% by mass or more and 20% by mass or less as measured with a mesh having an opening of 75 μm.
The blocking rate of the second resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 50% by mass or more and 90% by mass or less as measured with a mesh having an opening of 75 μm. Item 2. The two-component developer according to Item 1.   The two-component developer according to claim 1, wherein each of the first resin particles and the second resin particles contains a crosslinked styrene-acrylic acid resin. The crosslinked styrene-acrylic acid resin contained in the first resin particles includes a first (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms in the ester portion, a first styrene monomer, A polymer with a first crosslinking agent having two or more unsaturated bonds,
The crosslinked styrene-acrylic acid resin contained in the second resin particles includes a second (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms in the ester portion, a second styrene monomer, The two-component developer according to claim 3, which is a polymer with a second crosslinking agent having two or more unsaturated bonds.   The crosslinked styrene-acrylic acid resin contained in the first resin particles and the crosslinked styrene-acrylic acid resin contained in the second resin particles are composed of the same kind of monomer and the same kind of crosslinking agent. The two-component developer according to claim 3, wherein the two-component developers have different degrees of crosslinking. The first (meth) acrylic acid alkyl ester and the second (meth) acrylic acid alkyl ester are each butyl methacrylate,
Each of the first styrene monomer and the second styrene monomer is styrene,
5. The two-component developer according to claim 4, wherein each of the first crosslinking agent and the second crosslinking agent is divinylbenzene or ethylene glycol dimethacrylate.   The crosslinked styrene-acrylic acid resin contained in the first resin particles and the crosslinked styrene-acrylic acid resin contained in the second resin particles are crosslinked with different crosslinking agents. Item 5. The two-component developer according to Item 3 or 4. The first cross-linking agent is divinylbenzene;
The two-component developer according to claim 4, wherein the second crosslinking agent is ethylene glycol dimethacrylate.   The two-component developer according to claim 1, wherein the carrier base particles include a carrier core and a coat layer that covers a surface of the carrier core. In addition to the first resin particles, inorganic particles are attached to the surface of the toner base particles,
The two-component developer according to any one of claims 1 to 9, wherein inorganic particles are not externally added to the surface of the carrier base particles.

Images