JP2018120054A - Positively-charged toner and two-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively-charged toner and a two-component developer that can reduce both fogging due to supply of toner and fogging after being left standing in image formation.SOLUTION: A positively-charged toner includes a plurality of toner particles each including a toner base particle and an external additive attached to the surface of the toner base particle. The external additive contains powder of a coated particle 13 including an inorganic particle 131 and a coating layer 132 that coats the inorganic particle 131. The coating layer 132 contains a copolymer of two or more types of vinyl compounds containing at least a compound represented by the following formula (1).SELECTED DRAWING: Figure 2

Description

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

  For example, a positively chargeable toner including a plurality of toner particles including toner mother particles and an external additive attached to the surface of the toner mother particles is known. A two-component developer can be prepared by mixing a positively chargeable toner with a carrier. Such a two-component developer is set in, for example, an image forming apparatus (specifically, a developing apparatus) and supplied to the photosensitive drum for developing the electrostatic latent image.

  Patent Document 1 discloses hydrophobic silica particles as a material for an external additive of toner particles. In Patent Document 1, the silica particles are surface-treated with aminosilane or the like.

JP 2010-198004 A

  However, in the toner disclosed in Patent Document 1, the surface layer portion (portion modified with the surface treatment agent) of the external additive (specifically, the surface-treated silica particles) is shaved by stirring in the developing device. Therefore, the positive chargeability tends to be weak. When the positive chargeability of the toner is weakened by stirring in the developing device, replenishment fog and / or neglected fog are likely to occur in image formation.

  The present invention has been made in view of the above problems, and an object thereof is to provide a positively chargeable toner and a two-component developer capable of suppressing both replenishment fog and left-over fog in image formation.

  The positively chargeable toner according to the present invention includes a plurality of toner particles including toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes powder of coated particles including inorganic particles and a coat layer that covers the inorganic particles. The said coat layer contains the copolymer of 2 or more types of vinyl compounds containing the compound represented by following formula (1) at least.

In formula (1), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent.

  The two-component developer according to the present invention includes the positively chargeable toner according to the present invention and a carrier that can positively charge the positively chargeable toner by friction. The carrier is a powder of carrier particles comprising a carrier core containing a ferromagnetic substance and a resin layer covering the carrier core.

  According to the present invention, it is possible to provide a positively chargeable toner and a two-component developer that can suppress both replenishment fog and neglected fog in image formation.

FIG. 3 is a diagram illustrating a two-component developer according to an embodiment of the invention. FIG. 2 is an enlarged view showing an external additive (coated particle) of the toner particles shown in FIG. 1. FIG. 2 is a diagram illustrating an example of a two-component developer in which coated particles are replaced with positively-charged silica particles in the two-component developer shown in FIG. 1.

  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 average values from the powder unless otherwise specified. This is the number average of the values measured for each of the average particles by selecting a significant number of such particles.

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 not specified, and the “Coulter Counter Multisizer 3” manufactured by Beckman Coulter Co., Ltd. is used. ) Measured based on.

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

Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acryloyl (CH ₂ ═CH—CO—) and methacryloyl (CH ₂ ═C (CH ₃ ) —CO—) may be collectively referred to as “(meth) acryloyl”. The crystalline polyester resin is described as “crystalline polyester resin”, and the non-crystalline polyester resin is simply described as “polyester resin”.

  In the present specification, both untreated silica particles (hereinafter referred to as silica substrate) and silica particles obtained by subjecting a silica substrate to surface treatment (surface-treated silica particles) are described as “silica particles”. To do. The silica particles hydrophobized with the surface treatment agent may be described as hydrophobic silica particles, and the silica particles positively charged with the surface treatment agent may be described as positively charged silica particles, respectively.

  The toner according to the exemplary embodiment is a positively chargeable toner that can be suitably used for developing an electrostatic latent image. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner according to this embodiment may be used as a one-component developer. However, in order to form a high-quality image, for example, by using a mixing device (more specifically, a ball mill or the like), the toner according to the present embodiment and the carrier are mixed, whereby the two-component developer is used. It is preferable to prepare. The positively chargeable toner is positively charged by friction with the carrier.

The carrier is preferably a carrier particle powder comprising a carrier core containing a ferromagnetic substance (for example, ferrite) and a resin layer covering the carrier core. In order to ensure a sufficient charge imparting property of the carrier to the toner for a long period of time, the resin layer must completely cover the surface of the carrier core (that is, there is no surface area of the carrier core exposed from the resin layer). preferable. In order to impart magnetism to the carrier particles, the carrier core may be formed of a ferromagnetic material, or the carrier core may be formed of a resin in which ferromagnetic particles are dispersed. Examples of the resin constituting the resin layer are 1 selected from the group consisting of a fluororesin (more specifically, PFA or FEP), a polyamideimide resin, a silicone resin, a urethane resin, an epoxy resin, and a phenol resin. More than one type of resin may be mentioned. However, in order to ensure sufficient carrier stress resistance, it is particularly preferable that the resin layer covering the carrier core contains a silicone resin. When the volume median diameter (D ₅₀ ) of the toner is 4 μm or more and 9 μm or less, the volume median diameter (D ₅₀ ) of the carrier is preferably 20 μm or more and 120 μm or less, and preferably 30 μm or more and 70 μm or less. Is particularly preferred. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier.

  The toner according to the exemplary 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 a positively chargeable toner and a carrier is set) supplies toner to the photoconductor, and the static image formed on the photoconductor. Develop the electrostatic latent image. The toner is positively charged by friction with the carrier in the developing device before being supplied to the photoreceptor. In the developing process, toner (specifically, positively charged toner) on a developing sleeve (for example, the surface layer portion of the developing roller in the developing device) disposed in the vicinity of the photosensitive member is supplied to the photosensitive member. As the toner adheres 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 toner according to this embodiment includes a plurality of toner particles. The toner particles include toner base particles containing a binder resin and an external additive. The external additive adheres to the surface of the toner base particles. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, if necessary.

  The toner base particles may be toner base particles without a shell layer (hereinafter referred to as non-capsule toner base particles), or toner base particles with a shell layer (hereinafter referred to as capsule toner base particles). It may be. Capsule toner base particles can be produced by forming a shell layer on the surface of non-capsule toner base particles (toner core). The shell layer is substantially composed of a resin. For example, by covering a toner core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the toner core or may partially cover the surface of the toner core.

  The non-capsule toner base particles can be produced by, for example, 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 base particles. In general, non-encapsulated toner base particles are roughly classified into pulverized toner and polymerized toner (also called chemical toner). The non-capsule toner base particles obtained by the pulverization method belong to the pulverized toner, and the non-capsule toner base particles obtained by the aggregation method belong to the polymerized toner.

  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, non-encapsulated toner base particles having a desired particle diameter 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, non-encapsulated toner base particles having a desired particle diameter are obtained.

  When the capsule toner base particles are manufactured, the shell layer can be formed by any method. For example, the shell layer can be formed on the surface of the toner core (non-encapsulated toner base particles) by an in-situ polymerization method, a liquid-cured coating method, or a coacervation method.

  The toner according to the exemplary embodiment is a positively chargeable toner having the following configuration (hereinafter referred to as a basic configuration).

(Basic toner configuration)
The toner includes a plurality of toner particles including toner mother particles and an external additive attached to the surface of the toner mother particles. The external additive includes powder of particles (hereinafter referred to as coated particles) including inorganic particles and a coat layer covering the inorganic particles. Hereinafter, the powder of the coated particles may be referred to as “coated powder”. A coat layer contains the copolymer (henceforth a specific vinyl copolymer) of the 2 or more types of vinyl compound containing the compound represented by the above-mentioned formula (1) at least.

  Further, a two-component developer can be prepared by mixing the toner having the above basic configuration and a carrier capable of positively charging the toner by friction. The carrier is preferably a carrier particle powder comprising a carrier core containing a ferromagnetic substance and a resin layer covering the carrier core.

In the polymer of the vinyl compound, it is considered that the repeating unit derived from the vinyl compound is addition-polymerized by a carbon double bond “C═C”. The vinyl compound is a compound having a vinyl group (CH ₂ ═CH—) or a group in which hydrogen in the vinyl group is substituted. Examples of the vinyl compound include ethylene, propylene, butadiene, vinyl chloride, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, or styrene.

  The compound represented by the above formula (1) becomes a repeating unit represented by the following formula (1-1) by addition polymerization to constitute a copolymer. Hereinafter, the compound represented by the above formula (1) is referred to as “compound (1)”, and the repeating unit represented by the following formula (1-1) is referred to as “repeating unit (1-1)”. .

In formula (1-1), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent.

  In the above basic configuration, the specific vinyl copolymer contains the repeating unit (1-1). The specific vinyl copolymer containing the repeating unit (1-1) has high adhesion to inorganic particles (particularly silica particles) and is difficult to peel off. The repeating unit (1-1) has an unopened oxazoline group. The unopened oxazoline group has a cyclic structure and exhibits strong positive chargeability. Unopened oxazoline groups are likely to react with carboxyl groups, aromatic sulfanyl groups, and aromatic hydroxyl groups. An unopened oxazoline group can form a chemical bond by opening as shown in the following formula (1-2).

  Unopened oxazoline groups can be opened with a ring-opening agent (eg, acetic acid). By synthesizing the oxazoline group of the repeating unit (1-1) when synthesizing the specific vinyl copolymer, a crosslinked structure derived from the ring-opened oxazoline group can be formed in the specific vinyl copolymer. . The stress resistance of the coated particles can be improved by the coating layer of the coated particles containing the specific vinyl copolymer that is appropriately cross-linked. The specific vinyl copolymer preferably includes a repeating unit (1-1) having an unopened oxazoline group and a repeating unit (1-1) in which the oxazoline group is opened. Instead of ring-opening all oxazoline groups of the repeating unit (1-1) contained in the specific vinyl copolymer, an excellent amount of the repeating unit (1-1) oxazoline group can be opened. The inventor of the present application has found that coated particles having charging properties and sufficient stress resistance can be obtained.

  As the inorganic particles of the coated particles, inorganic particles that are easily positively charged by friction are preferable. More specifically, the inorganic particles of the coated particles are preferably silica particles or aluminum oxide particles, and particularly preferably silica particles. That is, the coated particle is particularly preferably a particle including silica particles and a coating layer that covers the silica particles (hereinafter referred to as coated silica particles). Hereinafter, the powder of the coated silica particles may be referred to as “coated silica powder”.

  In order to obtain a toner suitable for image formation, the particle diameter of the silica particles in the coated silica powder is 15 nm or more and 30 nm or less in number average, and the amount of the coated silica powder is 100 parts by mass of the toner base particles. It is particularly preferably 0.5 parts by mass or more and 5.0 parts by mass or less.

  In order to obtain coated silica particles having excellent positive chargeability and sufficient stress resistance, the amount of unopened oxazoline groups contained in 1 g of the coated silica powder measured by gas chromatography mass spectrometry , 0.030 mmol or more and 2.000 mmol or less is particularly preferable. The inventors of the present application have found that the aggregation of the developer (or toner) in a high-temperature and high-humidity environment can be suppressed by adjusting the unopened oxazoline group to the above-mentioned amount. When such agglomeration of the developer (or toner) occurs, vertical stripes are likely to occur in the formed image. The ring opening ratio of the oxazoline group can be controlled based on, for example, the amount of ring opening agent added.

  Unlike the internal additive, the external additive (specifically, a powder containing a plurality of external additive particles) does not exist inside the toner base particles, and the surface of the toner base particles (the surface layer portion of the toner particles). Only present selectively. 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.

  In order to suppress the detachment of the external additive particles from the toner particles, it is preferable that the external additive particles are strongly bonded to the surface of the toner base particles. The external additive particles may be fixed on the surface of the toner base particles by mechanical bonding by embedding. However, in order to improve the fluidity of the toner by the external additive particles, the external additive particles are weakly bonded to the surface of the toner base particles (for example, spherical external additive particles having a small particle diameter are rotated). It is preferable that the toner particles adhere to the surface of the toner base particles in a possible state. It is considered that the fluidity of the toner is improved by allowing the external additive particles to move while rotating on the surface of the toner base particles. It is preferable that the external additive particles for improving the fluidity of the toner adhere to the surface of the toner base particles mainly by van der Waals force or electrostatic force.

  Note that the entire surface of the inorganic particles may be completely covered with the coat layer, or the entire surface of the inorganic particles is not completely covered with the coat layer, and the surface of the inorganic particles is covered with the coat layer. There may be a region (hereinafter referred to as a covered region) and a region not covered with the coat layer (hereinafter referred to as an exposed region). However, in order to obtain coated particles having excellent positive chargeability and stress resistance, it is preferable that the coat layer covers an area of 95% or more and 100% or less of the entire surface of the inorganic particles. % Area (the coat layer completely covers the surface of the inorganic particles) is particularly preferable.

  Hereinafter, an example of a two-component developer containing toner having the above-described basic configuration will be described with reference to FIGS. 1 and 2.

  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 and a plurality of coated particles 13. Each of the plurality of coated particles 13 is attached to the surface of the toner base particles 11 mainly by van der Waals force or electrostatic force. The carrier includes a plurality of carrier particles 20.

  The carrier particles 20 preferably include a carrier core containing a ferromagnetic substance (for example, ferrite) and a resin layer that covers the surface of the carrier core. The resin layer may cover the entire surface of the carrier core, or may partially cover the surface region of the carrier core. However, in order to ensure sufficient carrier chargeability and durability, it is preferable that the resin layer completely covers the entire surface of the carrier core (with a covering area ratio of 100%).

  As shown in FIG. 2, the coated particles 13 include inorganic particles 131 and a coat layer 132 that covers the inorganic particles 131. The coat layer 132 contains a specific vinyl copolymer. The inorganic particles 131 are, for example, silica particles. The inorganic particles 131 may be surface-treated silica particles (for example, hydrophobic silica particles or positively charged silica particles). However, from the viewpoint of the productivity of the coated particles 13 and the coatability of the coat layer 132, the inorganic particles 131 are preferably silica particles that are not surface-treated (silica substrate).

  In the two-component developer (carrier and toner), the toner is charged by friction between the carrier and the toner. The positively chargeable toner is positively charged. In order to enhance the positive chargeability of the toner, silica particles (external additive) positively charged with a surface treatment agent may be applied to the surface of the toner particles. By using a surface treatment agent (for example, an aminosilane compound) to give an amino group to the surface of the silica particles, positively chargeable silica particles having a strong positive chargeability can be obtained. When the toner and the carrier are stirred in the developing device, the positively chargeable silica particles are positively charged. Further, when the toner is stressed by stirring in the developing device, the silica particles may be detached from the toner particles. When the positively charged silica particles are detached from the toner particles, a phenomenon (carrier contamination) occurs in which the silica particles adhere to the surface of the carrier particles due to electrostatic attraction between the silica particles and the carrier particles.

  The silica particles transferred from the toner particles to the carrier particles are present on the surface of the carrier particles and are easily subjected to strong stress due to stirring in the developing device. The positively chargeable silica particles have low resistance to such stress, and the surface layer portion (portion modified with the surface treatment agent) is worn by stirring in the developing device, and the positive chargeability tends to be weakened. Of the surface region of the positively chargeable silica particles, the region where the surface layer portion is cut has the chargeability (relatively strong negative chargeability) of the silica substrate. When the positively chargeable silica particles whose surface layer portion has been scraped on the carrier particles as described above return from the carrier particles to the toner particles, the surface of the toner particles has a strong positive chargeability region (the surface layer portion is damaged). The positively chargeable silica particles) and the low positively chargeable areas (areas where the positively charged silica particles with damaged surface layer are present) are included. Becomes weaker. In continuous printing, replenishment fog (specifically, fog generated due to poor charging of toner when a large amount of toner is replenished into the developing device at a time) occurs when the toner chargeability fluctuations in the developing device are large. It becomes easy.

  When the image forming apparatus is started (for example, when it is first run in the morning) or when the image forming apparatus is restarted after being left for a certain period of time, the charge amount of the toner tends to be insufficient, and the presence of insufficiently charged toner , Fogging easily occurs. Hereinafter, such a fog is referred to as a left-over fog in distinction from the replenishment fog. When the charge rising property and the charge retention property of the toner are insufficient, the presence of the insufficiently charged toner tends to cause neglected fog. When using non-surface-treated silica particles (silica substrate) as an external additive for toner particles, replenishment fog is less likely to occur than when positively charged silica particles are used, but neglected fog occurs. It becomes easy.

  FIG. 3 shows an example of a two-component developer in which the coated particles 13 are replaced with positively-charged silica particles 13a in the two-component developer shown in FIGS. The two-component developer shown in FIG. 3 includes a plurality of toner particles 10 a and a plurality of carrier particles 20. The toner particles 10a include a plurality of positively charged silica particles 13a as external additives. The positively chargeable silica particles 13a include inorganic particles 131 (specifically, a silica substrate) and a surface treatment layer 132a.

  When the toner and the carrier are agitated in the developing device, the positively-charged silica particles 13a are detached from the toner particles 10a and adhere to the surface of the carrier particles 20 as indicated by an arrow X1 in FIG. The positively-charged silica particles 13 a existing on the surface of the carrier particle 20 can move while rotating on the surface of the carrier particle 20.

  Further, when the positively chargeable silica particles 13a existing on the surface of the carrier particles 20 are subjected to strong stress by stirring in the developing device, as shown by an arrow X2 in FIG. 3, the positively chargeable silica particles 13a The surface treatment layer 132a is shaved.

  When the positively-charged silica particles 13a having the surface treatment layer 132a shaved on the carrier particles 20 as described above return to the toner particles 10a from the carrier particles 20 as indicated by an arrow X3 in FIG. The surface of the toner particle 10a has a region having a high positive chargeability (a region where the positively chargeable silica particles 13a exist before the arrow X1) and a region having a low positive chargeability (the positively chargeable silica particles 13a after the arrow X3). And the region in which it exists).

  In the toner having the basic configuration described above, the coating layer of the coated particles (external additive) contains a specific vinyl copolymer. For this reason, the coated particles tend to have excellent positive chargeability and sufficient stress resistance. By using the toner having the above basic configuration, it is possible to continuously form high-quality images while suppressing replenishment fog in continuous printing. Further, such coated particles tend to impart sufficient charge rise and charge retention properties to the toner. By using the toner having the above-described basic configuration, it is difficult to cause leftover fog. In particular, in the basic structure described above, when the inorganic particles of the coated particles are silica particles, it becomes easy to ensure sufficient charge rising property and charge retention of the toner. Further, in the toner having the above basic configuration, the chargeability and stress resistance of the coated particles can be easily adjusted by adjusting the ring-opening ratio of the oxazoline group of the specific vinyl copolymer.

  According to the above basic configuration, even when the toner base particles contain a resin having negative chargeability (more specifically, polyester resin or styrene-acrylic acid resin), sufficient toner chargeability is ensured. It becomes easy to do. In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, it is preferable that in the toner having the above-described basic configuration, the toner base particles are non-capsule toner base particles containing a polyester resin. The non-capsule toner base particles containing the polyester resin are particularly preferably pulverized toner. In such a pulverized toner, the non-capsule toner base particles contain one or more kinds of polyester resins melt-kneaded.

In order to obtain a toner suitable for image formation, it is preferable that the volume median diameter (D ₅₀ ) of the toner is 4 μm or more and 9 μm or less.

  Next, the configuration of the toner particles will be described. Specifically, the non-capsule toner base particles (binder resin and internal additive) and the external additive will be described in order.

[Toner mother particles]
(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 properties of the entire toner base particles. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and when the binder resin has an amino group, The toner base particles tend to be cationic.

  In order to improve the low-temperature fixability of the toner, it is preferable that the toner base particles contain a thermoplastic resin as the binder resin, and contain the thermoplastic resin in a proportion of 85% by mass or more of the entire binder resin. Is more preferable. Examples of the thermoplastic resin contained in the toner base particles include a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), an olefin resin (more specifically, In particular, polyethylene resin or polypropylene resin), vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, polyester resin, polyamide resin, or urethane resin are preferable. Further, a copolymer of the resin, 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 also used as the toner base. Preferred as a binder resin for the particles.

  In order to improve the low-temperature fixability of the toner, the toner base particles preferably contain a polyester resin or a styrene-acrylic acid resin, and particularly preferably contain a polyester resin. The toner base particles may contain a crystalline polyester resin as a binder resin.

  The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diol, bisphenol, trihydric or higher alcohol as shown below) and one or more polyhydric carboxylic acids (more specifically). 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).

  Suitable examples of the aliphatic diol 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, 1,12-dodecanediol, etc. ), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

  Preferable examples of 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), or cycloalkanedicarboxylic acid (more specifically, cyclohexanedicarboxylic acid etc.).

  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.

  To achieve both heat-resistant storage stability and low-temperature fixability of the toner, the glass transition of the binder resin (the most binder resin on a mass basis when the toner base particles contain multiple types of binder resins) It is preferable that a point (Tg) is 50 degreeC or more and 65 degrees C or less.

  In order to obtain a toner suitable for image formation, the softening point (Tm) of the binder resin (when the toner base particles contain a plurality of types of binder resins, the most binder resin on a mass basis) is 80. It is preferable that it is 150 degreeC or more.

  In order to ensure sufficient toner strength and fixability, the number average molecular weight of the binder resin (the largest binder resin on a mass basis when the toner base particles contain multiple types of binder resins) (Mn) is preferably 1000 or more and 2000 or less, and the molecular weight distribution (ratio Mw / Mn of mass average molecular weight (Mw) to number average molecular weight (Mn)) is preferably 20 or more and 40 or less.

(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 charging stability or charge rising property of the toner. The toner charge rising property is an index of whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner base particles, the anionicity of the toner base particles can be enhanced. Further, 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. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

[External additive]
In the toner having the basic configuration described above, the external additive is attached to the surface of the toner base particles. The external additive includes a coating powder defined by the basic configuration described above. The coated particles contained in the coated powder are particles including inorganic particles and a coat layer that covers the inorganic particles. The coat layer contains a specific vinyl copolymer (a copolymer of two or more vinyl compounds including at least the compound (1)).

  In addition to the coated particles, external additive particles other than the coated particles (hereinafter referred to as other external additive particles) may be used as the external additive. The other external additive particles are particularly preferably one or more external additive particles selected from the group consisting of silica particles, titanium oxide particles, and resin particles.

(Coated particles: inorganic particles)
The inorganic particles of the coated particles are preferably silica particles or metal oxide particles (more specifically, aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.), and silica. Particular preference is given to particles or aluminum oxide particles.

  The inorganic particles may be surface treated. For example, when silica particles are used as the inorganic particles, hydrophobicity and / or positive chargeability may be imparted to the surface of the silica particles by a 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), a silazane compound (for example, a chain silazane compound or a cyclic silazane compound). ) Or silicone oil (more specifically, dimethyl silicone oil or the like) can be preferably used. As the surface treatment agent, a silane coupling agent or a silazane compound is particularly preferable. Preferable examples of the silane coupling agent include silane compounds (more specifically, methyltrimethoxysilane or aminosilane). A preferred example of the silazane compound is HMDS (hexamethyldisilazane).

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 and silica are chemically bonded to each other, so that an amino group is imparted to the surface of the silica particles, and positively charged silica particles are obtained. 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 positive chargeability stronger than that of a silica substrate. When a silane coupling agent having an alkyl group is used, hydrophobic silica particles are obtained. More specifically, the hydroxyl group present on the surface of the silica substrate may be replaced with a functional group having an alkyl group at the end (more specifically, —O—Si—CH ₃ or the like) by the dehydration condensation reaction. it can. Thus, the silica particle to which the hydrophobic group (alkyl group) was provided instead of the hydrophilic group (hydroxyl group) tends to have a stronger hydrophobicity than the silica substrate.

(Coated particles: coat layer)
The coat layer of the coated particles contains a copolymer of one or more vinyl compounds represented by the above formula (1) and one or more other vinyl compounds (vinyl compounds other than the compound (1)). It is preferable to do. In each of the above formulas (1) and (1-1), R ¹ represents a hydrogen atom or an alkyl group (which may be linear, branched, or cyclic) that may have a substituent. . Examples of the substituent in the case where R ¹ represents an alkyl group having a substituent include phenyl group. R ¹ is particularly preferably a hydrogen atom, a methyl group, an ethyl group, or an isopropyl group. For example, in 2-vinyl-2-oxazoline, R ¹ represents a hydrogen atom.

  The coat layer particularly preferably contains a copolymer of a monomer (resin raw material) containing one or more kinds of compounds (1) and one or more kinds of (meth) acrylic acid alkyl esters. As a material for forming the coat layer, for example, an oxazoline group-containing polymer aqueous solution (“Epocross (registered trademark) WS series” manufactured by Nippon Shokubai Co., Ltd.) can be used. “Epocross WS-300” and “Epocross WS-700” each include a polymer of a monomer (resin raw material) containing 2-vinyl-2-oxazoline and one or more (meth) acrylic acid alkyl esters. .

  The other vinyl compound is preferably at least one vinyl compound selected from the group consisting of styrene monomers and acrylic monomers. Suitable examples of the styrenic monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), hydroxy styrene (more specifically, p-hydroxystyrene, m-hydroxystyrene, or the like), or halogenated styrene (specifically, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, or the like). Moreover, as a suitable example of an acrylic acid monomer, (meth) acrylic acid, (meth) acrylic acid alkyl ester, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylic acid aryl ester, (meth) acrylonitrile, or (Meth) acrylamide is mentioned.

  For example, when the other vinyl compound is an alkyl acrylate ester that may have a substituent on the alkyl group, the alkyl acrylate ester is, for example, a repeating unit represented by the following formula (2) by addition polymerization. To constitute a copolymer.

In formula (2), R ² represents an alkyl group (which may be linear, branched or cyclic) which may have a substituent. As the alkyl group, an alkyl group having 1 to 8 carbon atoms is preferable. When R ² represents an alkyl group having a substituent, the substituent of the alkyl group is preferably a hydroxyl group. R ² is preferably a methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, 2-ethylhexyl group, hydroxyethyl group, hydroxypropyl group, or hydroxybutyl group. .

  For example, when the other vinyl compound is a methacrylic acid alkyl ester which may have a substituent, the methacrylic acid alkyl ester which may have a substituent is represented by, for example, the following formula (3) by addition polymerization. To form a copolymer.

In formula (3), R ³ represents an alkyl group (which may be linear, branched or cyclic) which may have a substituent. As the alkyl group, an alkyl group having 1 to 8 carbon atoms is preferable. When R ³ represents an alkyl group having a substituent, a hydroxyl group is preferable as the substituent of the alkyl group. R ³ is preferably a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a 2-ethylhexyl group, a hydroxyethyl group, a hydroxypropyl group, or a hydroxybutyl group. .

  For example, when the other vinyl compound is a styrene monomer, the styrene monomer becomes a repeating unit represented by, for example, the following formula (4) by addition polymerization to constitute a copolymer.

In formula (4), R ^{41 to} R ⁴⁷ each independently represent a hydrogen atom or an arbitrary substituent. R ^{41 to} R ⁴⁵ are each independently preferably a halogen atom, a hydroxyl group, an alkyl group which may have a substituent, or an aryl group which may have a substituent, a halogen atom, a methyl group, An ethyl group or a hydroxyl group is particularly preferred. R ⁴⁶ and R ⁴⁷ are each independently preferably a hydrogen atom or a methyl group.

[Toner Production Method]
Hereinafter, an example of a method for producing a toner having the above-described basic configuration will be described.

(Preparation of toner mother particles)
First, toner mother particles are prepared. The toner base particles can be produced, for example, by the pulverization method or the aggregation method described above. The toner base particles may be commercially available products.

(Preparation of external additives)
Inorganic particles (for example, silica particles) are coated with a coat layer. In order to firmly bond the inorganic particles and the coating layer, it is particularly preferable to coat the inorganic particles by a reaction method. Hereinafter, the material for forming the coat layer may be referred to as a coat material.

  In an example of the reaction method, first, a coating material (for example, an oxazoline group-containing polymer) is dissolved in a solvent. By dissolving the coating material in a solvent in advance, the inorganic particles and the coating layer are easily bonded firmly by heating described below. The solvent for the coating material is preferably an aqueous medium. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100 ° C.

  Subsequently, inorganic particles are dispersed in the coating material solution to obtain a dispersion of inorganic particles. Further, the pH of the dispersion is adjusted as necessary.

  Subsequently, the dispersion liquid of the inorganic particles is heated to cause the coating material in the dispersion liquid to undergo a polymerization reaction on the surface of the inorganic particles. While the temperature of the liquid is maintained at a high temperature (or during the temperature increase), the coating material reacts with the inorganic particles and is immobilized on the surface of the inorganic particles. Thereafter, the dispersion is cooled to room temperature (about 25 ° C.). Thereby, a coat layer is formed on the surface of the inorganic particles, and coated particles are formed. As a result, a dispersion containing the coated powder (external additive) is obtained.

  Prior to or during the formation of the coat layer, a basic substance (more specifically, ammonia, sodium hydroxide, etc.) and / or a ring-opening agent (more specifically, in the dispersion of inorganic particles). Specifically, acetic acid or the like) may be added. By changing the amount of each of the basic substance and the ring-opening agent, the amount of unopened oxazoline groups contained in the toner can be adjusted. As the amount of the basic substance in the liquid increases, the amount of unopened oxazoline groups tends to increase. It is considered that the basic substance neutralizes (traps) the carboxylic acid, thereby suppressing the ring-opening reaction (nucleophilic addition reaction to the carbonyl group) of the oxazoline group. On the other hand, since the ring-opening agent promotes the ring-opening reaction of the oxazoline group, the amount of the unopened oxazoline group tends to decrease as the amount of the ring-opening agent in the liquid increases.

  In order to accelerate the polymerization reaction of the oxazoline group-containing polymer (coating material), the temperature of the inorganic particle dispersion is selected from an appropriate rate (for example, from 0.1 ° C./min to 3.0 ° C./min). It is preferable to keep the temperature at 60 ° C. or higher and 100 ° C. or lower. By maintaining the temperature of the dispersion at an appropriate temperature, the polymerization reaction of the coating material is facilitated.

  By filtering the dispersion of the coated particles, the liquid and the coated particles can be separated (solid-liquid separation). The resulting coated particles may be washed. When the coated particles are washed, the coated particles are preferably dried after washing.

(External addition process)
Next, an external additive is attached to the surface of the toner base particles. As the external additive, only the coated powder defined in the above-mentioned basic configuration may be used, or other external additive (for example, titanium oxide) together with the coated powder (for example, coated silica powder). Powder) may be used. Using a mixing device, the toner base particles and the external additive are mixed under the condition that the external base material is not embedded in the toner base particles, so that the external additive particles (coated particles, etc.) are formed on the surface of the toner base particles. Can be attached. As the mixing apparatus, for example, an FM mixer, a multipurpose mixer, or a hybridization system (registered trademark) can be suitably used.

  Through the above process, a toner containing a large number of toner particles can be produced. Note that unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. In order to produce the toner efficiently, it is preferable to produce a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

[Method for producing two-component developer]
A two-component developer can be obtained by mixing the toner obtained as described above and a carrier using a mixing device (for example, a ball mill). The carrier is preferably a carrier particle powder comprising a carrier core containing a ferromagnetic substance and a resin layer covering the carrier core. Examples of the ferromagnetic material contained in the carrier core include magnetite, barium ferrite, maghemite, Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Mn—Mg—Sr ferrite, Ca—Mg ferrite, and Li ferrite. Or iron oxide such as Cu-Zn ferrite is preferred. 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. Examples of the method for forming the resin 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.

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-12 and TB-1 to TB-2 (respectively positively chargeable toners) according to examples or comparative examples.

In Table 1, regarding the “material” of the inorganic particles, “N-1” and “N-2” were as follows.
The inorganic particles N-1 are hydrophilic fumed silica particles (“AEROSIL (registered trademark) 90G” manufactured by Nippon Aerosil Co., Ltd., surface treatment: none, BET specific surface area: about 90 m ² / g, number average primary particle size: About 20 nm).
Inorganic particles N-2 are hydrophilic fumed aluminum oxide particles (“AEROXIDE (registered trademark) Alu C” manufactured by Nippon Aerosil Co., Ltd.), surface treatment: none, BET specific surface area: about 100 m ² / g, number average primary particle size : About 13 nm).

In Table 1, “C-1” and “C-2” were as follows regarding the “material” of the coat layer.
The coating material C-1 was an oxazoline group-containing polymer aqueous solution (“Epocross WS-700” manufactured by Nippon Shokubai Co., Ltd.), monomer composition: methyl methacrylate / 2-vinyl-2-oxazoline / butyl acrylate, solid content concentration: 25 Mass%).
The coating material C-2 is an oxazoline group-containing polymer aqueous solution (“Epocross WS-300” manufactured by Nippon Shokubai Co., Ltd., monomer composition: methyl methacrylate / 2-vinyl-2-oxazoline, solid content concentration: 10% by mass). there were.

  In Table 1, the “amount” of the coating layer indicates the amount of addition (unit: g) of the coating material (coating layer material). “Ring-opening” of the coating layer indicates the amount (unit: g) of acetic acid (ring-opening agent) added in the coating layer forming step.

  In Table 1, “amount of unopened OXZ” indicates the amount of an unopened oxazoline group contained in 1 g of the external additive as measured by gas chromatography mass spectrometry.

  Hereinafter, a production method, an evaluation method, and an evaluation result of toners TA-1 to TA-12 and TB-1 to TB-2 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with which the error is sufficiently small are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Preparation of materials]
(External additive for toners TA-1 to TA-12)
As an external additive for each of toners TA-1 to TA-12, coated particles were used. However, the coat layer was formed under different conditions for each toner. Specifically, the types (materials) of inorganic particles, the addition amount of the coating material, and the addition amount of acetic acid (ring-opening agent) are shown in Table 1, respectively. The details of the method for producing the external additive were as follows.

  A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and the coating materials of the types and amounts shown in Table 1 (the coating shown in Table 1 defined for each toner) were placed in the flask. Material C-1 or C-2) and ion-exchanged water were added. The amount of ion-exchanged water added was such that the total amount of the coating material and ion-exchanged water was 300 g. For example, in the production of the external additive for toner TA-1, 21 g of the coating material C-1 (Epocross WS-700) was added. Further, in the production of the external additive for toner TA-7, 90 g of coating material C-2 (Epocross WS-300) was added.

  Subsequently, the temperature inside the flask was kept at 30 ° C. using a water bath while stirring the contents of the flask. Subsequently, 50 g of inorganic particles shown in Table 1 (inorganic particles N-1 or N-2 shown in Table 1 defined for each toner) are added to the flask, and the contents of the flask are set to 1 at a rotational speed of 200 rpm. Stir for hours. For example, in the production of the external additive for toner TA-12, 50 g of inorganic particles N-2 (AEROXIDE Alu C) were added. In preparing other toner external additives, 50 g of inorganic particles N-1 (AEROSIL 90G) were added.

  Subsequently, 200 g of ion exchange water was added to the flask. Subsequently, 6 mL of a 1% strength by weight aqueous ammonia solution was added into the flask. Subsequently, while stirring the contents of the flask at a rotational speed of 150 rpm, the temperature in the flask was raised to 80 ° C. at a rate of 1.0 ° C./min.

  In making the external additives for each of toners TA-6, TA-10, and TA-11, after the temperature in the flask reached 80 ° C., the amount of “ring opening” in Table 1 was used. A ring-opening agent (“acetic acid special grade” manufactured by Wako Pure Chemical Industries, Ltd.) was added into the flask at a constant rate. For example, in the production of toner TA-6, 1 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the flask. In the preparation of external additives for toners other than toners TA-6, TA-10, and TA-11, no ring-opening agent was added.

  Subsequently, while stirring the contents of the flask at a rotation speed of 100 rpm, the temperature in the flask was kept at 80 ° C. for 1 hour. Subsequently, a 1% by mass aqueous ammonia solution was added to the flask to adjust the pH of the flask contents to 7. Subsequently, the flask contents were cooled until the temperature reached room temperature (about 25 ° C.) to obtain a dispersion containing an external additive (coating powder).

  Subsequently, the dispersion of the external additive obtained as described above was filtered (solid-liquid separation) using a Buchner funnel to obtain a wet cake-like external additive. Thereafter, the obtained wet cake-like external additive was redispersed in ion-exchanged water. Furthermore, dispersion and filtration were repeated three times to wash the external additive.

Subsequently, the obtained external additive was used under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. As a result, an external additive (coated powder) for each of toners TA-1 to TA-12 was obtained. The external additive for each of toners TA-1 to TA-11 was a coated silica powder.

  The external additive for each of the toners TA-1 to TA-12 obtained as described above has a sharp particle size distribution, and is “number average primary particle diameter−5 nm” or more and “number average primary”. Only covered particles having a particle size (equivalent circle diameter) of “particle size + 5 nm” or less were substantially contained. The number average primary particle size of the external additive for each of the toners TA-1 to TA-11 is about 20 nm, and the number average primary particle size of the external additive for the toner TA-12 is about 13 nm. there were.

(External additive for Toner TB-1)
As an external additive for toner TB-1, hydrophilic fumed silica particles (AEROSIL 90G) were used. A coat layer was not formed.

(External additive for Toner TB-2)
As an external additive for the toner TB-2, silica particles hydrophobized and positively charged with a surface treatment agent were used. The details of the method for producing the external additive were as follows.

  A 1 L three-necked flask equipped with a thermometer and a stirring blade is set in a water bath, and 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.) and 3-aminopropyltriethoxysilane (Shin-Etsu Chemical Co., Ltd.) are placed in the flask. 5 g of company-made “KBE-903”), 5 g of n-propyltrimethoxysilane (“KBM-3033” manufactured by Shin-Etsu Chemical Co., Ltd.), and 50 g of hydrophilic fumed silica particles (AEROSIL 90G) were added. Thereafter, the contents of the flask were reacted at a temperature of 80 ° C. for 2 hours. By this reaction, silica particles were surface-treated. Subsequently, toluene was removed from the flask contents by boiling the flask contents at a temperature condition of about 100 ° C. for 2 hours. As a result, an external additive (powdered solid) before washing was obtained.

  Subsequently, the external additive obtained as described above was redispersed in ion-exchanged water. Subsequently, filtration (solid-liquid separation) was performed using a Buchner funnel. Furthermore, dispersion and filtration were repeated three times to wash the external additive.

Subsequently, the obtained external additive was used under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. As a result, an external additive for toner TB-2 (surface-treated silica particle powder) was obtained.

(External addition process)
100 parts by mass of toner base particles and 2 parts by mass of external additives (external additives shown in Table 1 defined for each toner) are mixed into a multipurpose small mixing and grinding machine (“Multipurpose mixer” manufactured by Nippon Coke Industries, Ltd. ”, Blade rotation speed (maximum): 10000 rpm) for 5 minutes.
The toner base particles used were non-externally added non-magnetic toner (production method: pulverization method (pulverized toner), shell layer: none (non-capsule toner base particles), binder resin: polyester resin, release agent: ester wax (day “Nissan Electol (registered trademark) WEP-3” manufactured by Oil Co., Ltd.), colorant: carbon black (“MA100” manufactured by Mitsubishi Chemical Corporation), charge control agent: quaternary ammonium salt (manufactured by Orient Chemical Industries, Ltd. BONTRON (registered trademark) P-51 ”), volume median diameter (D ₅₀ ): 7.0 μm).

  By the above mixing, the external additive adhered to the surface of the toner base particles. Thereafter, the obtained powder was sieved using a 200-mesh (aperture 75 μm) sieve. As a result, toners (toners TA-1 to TA-12 and TB-1 to TB-2) containing a large number of toner particles were obtained.

  Regarding the toners TA-1 to TA-12 and TB-1 to TB-2 obtained as described above, the unopened oxazoline group contained in 1 g of the external additive as measured by gas chromatography mass spectrometry. The amount (unopened OXZ amount) was as shown in Table 1. For example, the amount of unopened OXZ of toner TA-1 was 0.056 mmol / g. The method for measuring the amount of unopened OXZ was as shown below.

<Measurement method of the amount of unopened OXZ>
A surfactant aqueous solution was prepared by diluting a 2% by weight aqueous solution of a nonionic surfactant (“Emulgen (registered trademark) 120” manufactured by Kao Corporation, component: polyoxyethylene lauryl ether) 10 times with water, In 500 mL of the surfactant aqueous solution, 10 g of toner (measuring object: any of toners TA-1 to TA-12 and TB-1 to TB-2) 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 the external additive were separated. Subsequently, a reslurry for adding ion-exchanged water and suction filtration were repeated three times for the obtained external additive to obtain an external additive for evaluation.

  Next, the obtained external additive for evaluation was subjected to gas chromatography mass spectrometry (GC / MS method). In the GC / MS method, a gas chromatograph mass spectrometer (“GCMS-QP2010 Ultra” manufactured by Shimadzu Corporation) and a multi-shot pyrolyzer (“Frontier LAB Multi-functional Pyrolyzer” manufactured by Frontier Laboratories, Inc.) are used as measurement devices. Trademark) PY-3030D "). As a column, a GC column ("Agilent (registered trademark) J & W Ultra Inert Capillary GC Column DB-5ms" manufactured by Agilent Technologies, Inc.), phase: an arylene phase in which allylene is reinforced with a siloxane polymer to strengthen the main chain of the polymer, inner diameter: 0.25 mm, film thickness: 0.25 μm, length: 30 m).

(Gas chromatograph)
Carrier gas: Helium (He) gas Carrier flow rate: 1 mL / min Vaporization chamber temperature: 210 ° C
・ Pyrolysis temperature: Furnace “600 ° C”, interface part “320 ° C”
-Temperature rising condition: After holding at 40 ° C for 3 minutes, the temperature was raised from 40 ° C to 300 ° C at a rate of 10 ° C / min, and held at 300 ° C for 15 minutes.

(Mass spectrometry)
-Ionization method: EI (Electron Impact) method-Ion source temperature: 200 ° C
・ Interface temperature: 320 ℃
Detection mode: scan (measurement range: 45 m / z to 500 m / z)

  The components were estimated by analyzing the mass spectrum measured under the above conditions, and the amount of unopened oxazoline group (unopened OXZ) contained in 1 g of the external additive for evaluation based on the peak area of the measured chromatogram. Amount) was measured. Standard substances were used for quantification.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-12 and TB-1 to TB-2) is as follows.

(Preparation of two-component developer)
100 parts by mass of a developer carrier and 10 parts by mass of a sample (toner) were mixed for 30 minutes using a ball mill to prepare a two-component developer. The carrier for the developer is coated carrier particles (carrier core: Mn—Mg—Sr ferrite core (“EF-50” manufactured by Powder Tech Co., Ltd.)), resin layer: silicone resin (manufactured by Toray Dow Corning Co., Ltd.), resin layer Covering ratio: 100% (complete coating), volume median diameter (D ₅₀ ): 50 μm). Using the obtained two-component developer, the fog resistance and aggregation degree of the toner were evaluated by the following procedure.

(Fogging resistance)
A multifunction machine (“TASKalfa 5550ci” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. The two-component developer obtained by the above-described method was put into the developing device of the evaluation machine, and the sample (supplementary toner) was put into the toner container of the evaluation machine.

Subsequently, in the environment of a temperature of 32 ° C. and a humidity of 80% RH, the first printing durability test was performed to perform continuous printing on 10000 sheets of paper (A4 size plain paper) at a printing rate of 2% using the evaluation machine. It was. After the first printing durability test, in the environment of temperature 32 ° C. and humidity 80% RH, using the evaluation machine, continuous printing is performed on 500 sheets of paper (A4 size plain paper) at a printing rate of 20%. A printing durability test was conducted. During the second printing durability test, every time 50 sheets were printed, the reflection density of the blank portion in the printed paper was measured using a reflection densitometer (“SpectroEye (registered trademark)” 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

The highest fog density (maximum fog density) among all fog densities (FD) measured at each timing (timing for every 50 sheets) during the second printing durability test was determined. Hereinafter, the maximum fog density obtained here, referred to as fog density FD _A.

After performing the first printing test and the second printing test using the evaluation machine as described above, the evaluation machine was allowed to stand for 12 hours in an environment of a temperature of 32 ° C. and a humidity of 80% RH. Subsequently, in an environment of a temperature of 32 ° C. and a humidity of 80% RH, a sample image including a solid part and a blank part was printed on each of ten recording media (evaluation sheets) using the evaluation machine. Subsequently, using a reflection densitometer (“SpectroEye” manufactured by X-Rite), the reflection density of the blank portion of the sample image in each of the 10 printed recording media was measured. Subsequently, the fog density (FD) was determined for each recording medium based on the above formula. And the highest fog density (maximum fog density) was obtained among all the fog densities (FD) measured for each recording medium. Hereinafter, the maximum fog density obtained here, referred to as fog density FD _B.

Fog density FD _A is equal to or 0.008 ◎ (very good) and evaluated, and evaluated as long as 0.008 ultrasonic 0.025 ○ (good), × if it exceeds 0.025 ( Not good).

Fog density FD _B is equal to or 0.008 ◎ (very good) and evaluated, and evaluated as long as 0.008 ultrasonic 0.025 ○ (good), × if it exceeds 0.025 ( Not good).

(Degree of aggregation)
In the above-described evaluation of fog resistance, after performing the first printing test and the second printing test as described above, the developer (two-component developer) is taken out from the developing device of the evaluation machine and evaluated. A developer was obtained. 10 g of the developer for evaluation thus taken out was placed on a sieve having a known mass of 200 mesh (aperture 75 μm). Then, the mass of the developer for evaluation on the sieve (the mass of the developer before sieving) was determined by measuring the mass of the sieve on which the developer for evaluation was placed. Subsequently, the sieve was vibrated for 180 seconds under the conditions of a frequency of 50 Hz and an amplitude of 2 mm in accordance with a manual of a powder property evaluation apparatus (“Powder Tester (registered trademark) PT-X” manufactured by Hosokawa Micron Corporation). After sieving, the mass of the developer remaining on the sieve (the mass of the developer after sieving) was measured by measuring the mass of the sieve containing the developer for evaluation on the sieve. Then, the degree of aggregation (% by mass) of the developer was calculated based on the following formula.
Aggregation degree (% by mass) = 100 × mass of developer after sieving / mass of developer before sieving

  When the degree of aggregation is 1.0% by mass or less, it is evaluated as ◎ (very good), and when the degree of aggregation is more than 1.0% by mass and 3.0% by mass or less, it is evaluated as ○ (good). Was over 3.0% by mass, it was evaluated as x (not good).

[Evaluation results]
For each of toners TA-1 to TA-12 and TB-1 to TB-2, stress resistance (developer aggregation), replenishment fog (fogging density FD _A ), and neglected fog (fogging density FD _B ) are obtained. The evaluation results are shown in Table 2.

  The toners TA-1 to TA-12 (positively chargeable toners according to Examples 1 to 12) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-12 includes a plurality of toner particles each including toner mother particles and an external additive attached to the surface of the toner mother particles. The external additive included powder of coated particles including inorganic particles (specifically, silica particles or aluminum oxide particles) and a coat layer covering the inorganic particles. The coating layer contained a specific vinyl copolymer (a copolymer of two or more vinyl compounds including at least the compound represented by the above formula (1)) (the aforementioned “toners TA-1 to TA”. (Refer to the method of “External Additive for -12”).

  As shown in Table 2, the positively chargeable toners according to Examples 1 to 12 were excellent in stress resistance and were able to suppress both replenishment fog and neglected fog in image formation.

  In the toner TA-1 production method, a styrene monomer (specifically, styrene) is further added in addition to the oxazoline group-containing polymer aqueous solution (Epocross WS-700) in the external additive coating layer forming step. As a result, good results (◯ or ◎) were obtained in all evaluations.

  The positively chargeable toner according to the present invention can be used for forming an image in, for example, a copying machine, a printer, or a multifunction machine.

10 toner particles 10a toner particles 11 toner base particles 13 coated particles (external additives)
13a Positively chargeable silica particles (external additive)
20 Carrier particles 131 Inorganic particles 132 Coat layer 132a Surface treatment layer

Claims (12)

A plurality of toner particles comprising toner mother particles and an external additive attached to the surface of the toner mother particles;
The external additive includes a powder of coated particles comprising inorganic particles and a coat layer covering the inorganic particles,
The positively chargeable toner, wherein the coat layer contains a copolymer of at least two vinyl compounds including at least a compound represented by the following formula (1).

In formula (1), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent.   The positively chargeable toner according to claim 1, wherein the powder of the coated particles is a powder of coated silica particles including silica particles and a coating layer that covers the silica particles.   The amount of unopened oxazoline groups contained in 1 g of the powder of the coated silica particles, measured by gas chromatography mass spectrometry, is 0.030 mmol or more and 2.000 mmol or less, according to claim 2. Toner. The particle diameter of the silica particles in the powder of the coated silica particles is 15 nm or more and 30 nm or less in number average.
The positively chargeable toner according to claim 3, wherein an amount of the powder of the coated silica particles is 0.5 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the toner base particles.   The positively chargeable toner according to claim 2, wherein the silica particles are a silica base that is not surface-treated.   The positively chargeable toner according to claim 1, wherein the inorganic particles are aluminum oxide particles.   The positively chargeable toner according to claim 1, wherein the copolymer of the two or more vinyl compounds contained in the coat layer has a crosslinked structure derived from a ring-opened oxazoline group. .   The positive charge according to any one of claims 1 to 7, wherein the two or more vinyl compounds include one or more vinyl compounds selected from the group consisting of styrene monomers and acrylic monomers. Toner.   The copolymer of the two or more types of vinyl compounds contained in the coat layer includes one or more types of compounds represented by the formula (1) and one or more types of (meth) acrylic acid alkyl esters. The positively chargeable toner according to any one of claims 1 to 8, which is a copolymer of monomers.   The positively chargeable toner according to claim 1, wherein the toner base particles are non-capsule toner base particles containing a polyester resin.   The positively chargeable toner according to claim 10, wherein the toner base particles are pulverized toner. A positively chargeable toner according to any one of claims 1 to 11 and a carrier capable of positively charging the positively chargeable toner by friction,
The two-component developer, wherein the carrier is a carrier particle powder including a carrier core containing a ferromagnetic substance and a resin layer covering the carrier core.

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