JP2019053155A - Positively chargeable toner, two-component developer, and external additive for toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously form a high-quality image by suppressing fog and toner scattering in continuous printing. SOLUTION: A positively charged toner contains a plurality of toner particles including toner mother particles and an external additive adhering to the surface of the toner mother particles. The external additive contains the powder of the coated titania particles 13 including the titania particles 131 and the coat layer 132 covering the titania particles 131. The coat layer 132 contains a copolymer of two or more kinds of vinyl compounds including a compound represented by the following formula (1). The amount of unopened oxazoline groups in 1 g of the powder of the coated titania particles 13 is 0.100 mmol or more and 0.600 mmol or less, and the amount of oxazoline groups that are ring-opened by the reaction with the functional groups is 0.100 mmol or more and 0. It is 400 mmol or less. [Selection diagram] Fig. 2

Description

  The present invention relates to a positively chargeable toner, a two-component developer, and an external additive for toner.

  Patent Document 1 discloses titanium oxide fine particles surface-treated with a coupling agent as an external additive for toner.

JP 7-295285 A

  However, in the toner using the external additive disclosed in Patent Document 1, the surface layer portion of the external additive (specifically, the portion modified with the surface treatment agent) is shaved by stirring in the developing device, The chargeability of the toner tends to fluctuate. If the chargeability of the toner fluctuates due to stirring in the developing device, it becomes difficult to continuously form high-quality images in continuous printing.

  The present invention has been made in view of the above problems, and an object of the present invention is to continuously form high-quality images while suppressing fogging and toner scattering in continuous printing.

  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 a powder of coated titania particles including titania particles and a coat layer covering the titania 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. The amount of unopened oxazoline groups contained in 1 g of the powder of the coated titania particles is 0.100 mmol or more and 0.600 mmol or less. The amount of the oxazoline group in the coating layer contained in 1 g of the powder of the coated titania particles and ring-opened by the reaction with the functional group present on the surface of the titania particles is 0.100 mmol or more and 0.400 mmol or less. It is.

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.

  The external additive for toner according to the present invention includes powder of coated titania particles including titania particles and a coating layer covering the titania particles. The coat layer contains a copolymer of two or more kinds of vinyl compounds including at least the compound represented by the formula (1). The amount of unopened oxazoline group contained in 1 g of the toner external additive is 0.100 mmol or more and 0.600 mmol or less. The amount of the oxazoline group in the coating layer that is ring-opened by reaction with the functional group present on the surface of the titania particles contained in 1 g of the external additive for toner is 0.100 mmol or more and 0.400 mmol or less. is there.

  According to the present invention, it is possible to continuously form high-quality images while suppressing fogging and toner scattering in continuous printing.

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 titania particles) of the toner particles 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 not specified in the powder unless otherwise specified. It is the number average of the values measured for a considerable number of particles contained.

Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent-circle diameters of primary particles (Haywood diameter: the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Value. Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is 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 titania particles (hereinafter referred to as “titania substrate”) and titania particles obtained by subjecting the titania substrate to surface treatment (that is, surface-treated titania particles) include “titania”. Particles ". In some cases, titania particles hydrophobized with a surface treatment agent are referred to as “hydrophobic titania particles”, and titania particles positively charged with a surface treatment agent are referred to as “positively chargeable titania particles”.

  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 a plurality of binder resin fine particles, a plurality of release agent fine particles, and a plurality of colorant fine particles 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 a powder of particles (hereinafter referred to as “coated titania particles”) including titania particles and a coating layer covering the titania particles. Hereinafter, the powder of the coated titania particles may be referred to as “coated titania powder”. The coat layer contains a copolymer of two or more kinds of vinyl compounds including at least the compound represented by the above formula (1) (hereinafter referred to as “specific vinyl copolymer”). The amount of unopened oxazoline group (hereinafter referred to as “amount of unopened OXZ”) contained in 1 g of the powder of coated titania particles is 0.100 mmol or more and 0.600 mmol or less. Amount of oxazoline groups in the coating layer that are ring-opened by reaction with functional groups present on the surface of the titania particles contained in 1 g of the powder of coated titania particles (hereinafter referred to as “amount of ring-opened OXZ”) Is 0.100 mmol or more and 0.400 mmol or less. The amount of unopened OXZ and the amount of ring-opened OXZ can be measured by gas chromatography mass spectrometry, respectively. Hereinafter, the material for forming the coat layer may be referred to as “coat material”.

  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 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 unit represented by the following formula (1-1) is referred to as “unit (1-1)”.

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

In the basic configuration described above, the coated titania particles (external additive) include titania particles. In general, titania particles are hard. For this reason, titania particles have abrasiveness. The coat layer of the coated titania particles contains a specific vinyl copolymer. The specific vinyl copolymer contains the unit (1-1). The 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. In addition, the unopened oxazoline group can also react with a hydroxyl group (—OH) present on the surface of the titania particle. The acidity of the surface of the titania particle is strong, and the hydroxyl group (—OH) present on the surface of the titania particle tends to react with the oxazoline group. For example, when the unit (1-1) in the coat layer reacts with the hydroxyl group of titania particles (represented as R ^{0 in the} formula (1-2)), an oxazoline group is formed as shown in the following formula (1-2). The ring is opened, and a chemical bond (specifically, a covalent bond) is formed between the titania particles and the coat layer. By forming such a bond, the bond between the titania particles and the coat layer becomes strong, and the detachment of the coat layer from the titania particles is suppressed. Hereinafter, the unit represented by the following formula (1-2) is referred to as “unit (1-2)”.

The coat layer of the coated titania particles preferably includes units (1-1) and units (1-2). The unit (1-2) includes an oxazoline group that is ring-opened by reaction with a functional group present on the surface of the titania particle. In formula (1-2), R ¹ represents the same group as R ¹ in formula (1-1), and R ⁰ represents titania particles.

  The unopened oxazoline group has both crosslinkability and positive chargeability. For this reason, the coating titania particle (external additive) which has the outstanding positive charging property and sufficient stress resistance is obtained by making a coating layer contain a specific vinyl copolymer. By using the toner containing such coated titania particles (external additives), it is possible to continuously form high-quality images while suppressing fogging and toner scattering in continuous printing.

  In the basic configuration described above, the positive chargeability of the toner tends to increase as the amount of unopened OXZ increases. However, if the amount of unopened OXZ is too large, the toner tends to attenuate the charge. In the toner having the above-described basic configuration, the amount of unopened OXZ is an appropriate amount (specifically, 0.100 mmol or more and 0.600 mmol or less), so that sufficient positive charging of the toner can be achieved while sufficiently suppressing charge attenuation of the toner. It becomes possible to ensure the sex. If the positive chargeability of the toner is insufficient, or if the toner is subject to charge attenuation, toner scattering tends to occur.

  In the above-described basic configuration, as the amount of ring-opening OXZ increases, the bond between the titania particles and the coating layer tends to become stronger. In the coated titania particles, the bond strength between the titania particles and the coat layer is insufficient, and when the coat layer is peeled off and the titania particles are exposed, the chargeability of the coated titania particles varies. For example, a titania substrate can be used as the core portion (titania particles) of the coated titania particles. The titania substrate has a stronger positive chargeability than the coat layer (resin layer). For this reason, when the coat layer is peeled off and the titania substrate is exposed, the toner is likely to be excessively charged up. An excessive charge-up of the toner reduces the quality (specifically, the image density) of the image formed by the toner. However, if the amount of ring-opening OXZ is too large, the developability of the toner tends to deteriorate. The titania substrate has a low electrical resistance. For this reason, when titania particles are used as an external additive, excessive charging of the toner is suppressed and the charge amount distribution of the toner is narrowed. Even when the coated titania particles are used as an external additive, the same effect can be obtained unless the amount of ring-opening OXZ is sufficiently small. On the other hand, when the amount of ring-opening OXZ is too large, the above-mentioned effect cannot be achieved due to the increased electrical resistance of the coated titania particles. As a result, the developability of the toner is deteriorated. In the toner having the above-described basic configuration, the amount of ring-opening OXZ is an appropriate amount (specifically, 0.100 mmol or more and 0.400 mmol or less), so that high-quality images can be obtained while suppressing the peeling of the external additive coating layer. Can be formed continuously.

  In the basic structure described above, the total amount of the unopened OXZ amount and the ring-opened OXZ amount is preferably 1.000 mmol or less, and more preferably 0.950 mmol or less. In the coating layer forming step, when the coating material is added in such an amount that the total amount of the unopened OXZ and the ring-opened OXZ exceeds 1.000 mmol, the coating layer is appropriately formed. The titania particles may agglomerate before being applied. Also from the viewpoint of toner productivity, it is not preferable that the amount of ring-opening OXZ exceeds 0.400 mmol in the above-described basic configuration.

  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, it is preferable that the external additive particles are weakly bonded to the surface of the toner base particles. For example, it is preferable that spherical external additive particles having a small particle size adhere to the surface of the toner base particles in a rotatable 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 titania particles may be completely covered with the coat layer, or the entire surface of the titania particles is not completely covered with the coat layer, and the surface of the titania 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 titania particles having excellent positive chargeability and stress resistance, it is preferable that the coating layer covers an area of 95% or more and 100% or less of the entire surface of the titania particles, It is particularly preferable to cover 100% of the area (that is, the coat layer completely covers the surface of the titania particles).

  In an example of a toner suitable for image formation, in the above-described basic configuration, the titania particles are a titania substrate that has not been surface-treated, the coating layer covers the entire surface of the titania particles, and the powder of the coated titania particles The number average particle size of the titania particles is 15 nm or more and 50 nm or less (particularly preferably, 15 nm or more and 30 nm or less), and the amount of powder of the coated titania particles is 0.5 to 100 parts by mass of the toner base particles. It is not less than 5.0 parts by mass. In the toner having such a configuration, sufficient fluidity of the toner can be secured by the coated titania particles even if the external additive does not contain silica particles.

  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 (specifically, powder of toner particles 10) and carrier (specifically, powder of carrier particles 20). The toner includes a plurality of toner particles 10 including toner base particles 11 and a plurality of coated titania particles 13. Each of the plurality of coated titania 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 (that is, with a covering area ratio of 100%).

  As shown in FIG. 2, the coated titania particles 13 include titania particles 131 and a coat layer 132 that covers the titania particles 131. The coat layer 132 contains a specific vinyl copolymer. The titania particles 131 are, for example, a titania substrate (that is, untreated titanium oxide particles). The titania particles 131 may be surface-treated titanium oxide particles (for example, hydrophobic titania particles or positively charged titania particles). However, from the viewpoint of the productivity of the coated titania particles 13 and the coverage of the coat layer 132, the titania particles 131 are preferably a titania substrate.

  According to the basic configuration described above, even when the toner base particles contain a resin having negative chargeability (more specifically, a polyester resin or a styrene-acrylic acid resin), sufficient toner chargeability can be obtained. It becomes easy to secure. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, non-encapsulated toner base particles in which the toner base particles contain a polyester resin and do not contain an oxazoline group in the toner having the basic structure described above. It is preferable that That is, it is preferable that the internal additive of the non-capsule toner base particles does not contain a material having an oxazoline group. 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 coated titania powder defined by the basic configuration described above. The coated titania particles contained in the coated titania powder are particles including titania particles and a coating layer covering the titania particles. The coat layer contains a specific vinyl copolymer (specifically, a copolymer of two or more vinyl compounds including at least the compound (1)).

  In addition to the coated titania particles, external additive particles other than the coated titania particles (hereinafter referred to as “other external additive particles”) may be used as the external additive. As the other external additive particles, one or more external additive particles selected from the group consisting of silica particles, titania particles, and resin particles are particularly preferable.

(Coat layer)
The coating layer of the coated titania particles is composed of a co-weight of one or more kinds of vinyl compounds represented by the above formula (1) and one or more kinds of other vinyl compounds (that is, vinyl compounds other than the compound (1)). It is preferable to contain a coalescence. In each of the aforementioned formula (1), formula (1-1), and formula (1-2), R ¹ is a hydrogen atom or an alkyl group (straight, branched, and optionally substituted). It may be any ring shape. 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, when the coating material is 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)
Titania particles are coated with a coating layer. In order to firmly bond the titania particles and the coating layer, it is particularly preferable to coat the titania particles by a reaction method.

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

  Subsequently, the dispersion of titania particles is heated, and the coating material in the dispersion is polymerized on the surface of the titania particles. While the temperature of the liquid is kept high (or during the temperature rise), the coating material reacts with the titania particles and is immobilized on the surface of the titania particles. Thereafter, the dispersion is cooled to room temperature (about 25 ° C.). Thereby, a coat layer is formed on the surface of the titania particles, and coated titania particles are formed. As a result, a dispersion containing the coated titania 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 titania particles). Specifically, acetic acid or the like) may be added.

  In order to promote the polymerization reaction of the oxazoline group-containing polymer (coating material), the temperature of the titania 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 titania particles, the liquid and the coated titania particles can be separated (solid-liquid separation). The resulting coated titania particles may be washed. When the coated titania particles are washed, it is preferable to dry the coated titania particles 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 toner external additive (specifically, the coated titania powder) defined in the above basic configuration may be used, or other external additives may be used together with the coated titania powder. May be used. By using a mixing device, the toner base particles and the external additive are mixed under conditions such that the external additive is not embedded in the toner base particles, so that the external additive particles adhere to the surface of the toner base particles. it can. 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-5 and TB-1 to TB-6 (each positively chargeable toner) according to Examples or Comparative Examples.

In Table 1, regarding “materials” for the surface treatment, “S-1” to “S-3” were as follows.
The surface treating agent S-1 was n-octyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.).
The surface treating agent S-2 was 3-aminopropyltriethoxysilane (“KBE-903” manufactured by Shin-Etsu Chemical Co., Ltd.).
The surface treating agent S-3 was n-propyltrimethoxysilane (“KBM-3033” manufactured by Shin-Etsu Chemical Co., Ltd.).

In Table 1, “C-1” and “C-2” were as follows regarding the “material” of the coat layer.
The coating material C-1 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.
The coating material C-2 is 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%).

  In Table 1, the “amount” of the coating layer indicates the amount (unit: g) of the coating material (that is, the material of the coating layer) added.

  In Table 1, “ring-opening agent” means acetic acid (distributor: Wako Pure Chemical Industries, Ltd., grade: reagent grade). Acetic acid functions as a ring-opening agent for the oxazoline group.

  In Table 1, “Unopened ring” in “OXZ amount” indicates the amount of unopened oxazoline group contained in 1 g of the external additive. In Table 1, “opening” of “OXZ amount” indicates the amount of oxazoline groups in the coating layer that are ring-opened by reaction with functional groups present on the surface of titania particles contained in 1 g of the external additive. Show.

  Hereinafter, the production methods, evaluation methods, and evaluation results of the toners TA-1 to TA-5 and TB-1 to TB-6 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 additives for toners TA-1 to TA-5 and TB-1 to TB-4)
Coated titania particles were used as external additives for toners TA-1 to TA-5 and TB-1 to TB-4, respectively. However, the coat layer was formed under different conditions for each toner. Specifically, the amount of the coating material added was as shown in Table 1. 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 type and amount of coating material (coating material C-1 or C-2) shown in Table 1 and ions in the flask We put in exchange water. 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, 15 g of the coating material C-1 (Epocross WS-300) and 285 g of ion-exchanged water were added. Further, in the production of the external additive for toner TA-5, 25 g of the coating material C-2 (Epocross WS-700) and 275 g of ion-exchanged water were 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 titania particles (“AEROXIDE (registered trademark) P25” manufactured by Nippon Aerosil Co., Ltd., content: untreated dry fumed titanium oxide, number average primary particle size: 21 nm) are added to the flask, and the rotation speed is increased. The flask contents were stirred for 1 hour at 200 rpm.

  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. After completion of the temperature increase, an oxazoline group ring-opening agent (acetic acid) was added in an amount shown in Table 1. For example, in the production of toner TA-1, 6 g of a ring-opening agent (acetic acid) was added. Further, no ring-opening agent (acetic acid) was added in the production of the toners TB-3, TB-5, and TB-6.

  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 (coated titania 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, external additives (coated titania powder) for toners TA-1 to TA-5 and TB-1 to TB-4 were obtained. In any coated titania powder, the coat layer covered the entire surface of the titania particles.

  The external additives for each of the toners TA-1 to TA-5 and TB-1 to TB-4 obtained as described above had a sharp particle size distribution. Specifically, each external additive contains 80 number% or more of titania particles having a particle size (specifically, equivalent circle diameter) of “number average primary particle size−5 nm” or more and “number average primary particle size + 5 nm” or less. Was included.

(External additive for toner TB-5 and TB-6)
As an external additive for each of toners TB-5 and TB-6, surface-treated titania particles 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 the surface treatment agent of the type and amount shown in Table 1 are included in the flask. , 50 g of titania particles (“AEROXIDE P25” manufactured by Nippon Aerosil Co., Ltd.) was added. In the production of the external additive for toner TB-5, 6 g of surface treatment agent S-1 (n-octyltrimethoxysilane) was added as a surface treatment agent. In the preparation of the external additive for toner TB-6, 3 g of the surface treatment agent S-2 (3-aminopropyltriethoxysilane) and 3 g of the surface treatment agent S-3 (n-propyl) are used as the surface treatment agents. Trimethoxysilane).

  Subsequently, the contents of the flask were reacted at a temperature of 80 ° C. for 2 hours. By this reaction, the titania 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 dried under conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coatmizer” manufactured by Freund Sangyo Co., Ltd.). As a result, external additives for toner TB-5 and TB-6 (surface-treated titania particle powder) were obtained.

[Production of toner]
Table 1 shows 100 parts by mass of toner base particles using a multipurpose small mixing and grinding machine (“Multipurpose mixer” manufactured by Nippon Coke Industries, Ltd., blade rotation speed (maximum): 10,000 rpm) under the condition of a rotation speed of 3000 rpm. 2 parts by weight of an external additive (coated titania powder or surface-treated titania particle powder) was mixed 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 containing toner particles (toners TA-1 to TA-5 and TB-1 to TB-6) were obtained.

  Regarding the toners TA-1 to TA-5 and TB-1 to TB-6 obtained as described above, the amount of unopened OXZ (specifically, the amount of unopened oxazoline group contained in 1 g of the external additive), The amount of ring-opening OXZ (specifically, the amount of oxazoline group in the coating layer that is ring-opened by reaction with a functional group present on the surface of titania particles contained in 1 g of the external additive) is shown in Table 1 respectively. It was as shown. For example, for toner TA-1, the amount of unopened OXZ was 0.128 mmol / g, and the amount of ring-opened OXZ was 0.173 mmol / g. Each measurement method of the amount of unopened OXZ and the amount of ring-opened OXZ was as shown below.

<Measurement method of OXZ amount>
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 one of toners TA-1 to TA-5 and TB-1 to TB-6) 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 based on the peak area of the measured chromatogram, the amount of unopened OXZ and the amount of ring-opened OXZ (each amount per 1 g of external additive for evaluation) ) Was measured. A calibration curve was used for quantification. Regarding the coated titania powder, the total of the amount of unopened OXZ and the amount of ring-opened OXZ is the amount of oxazoline groups added in the coating layer forming step (specifically, the amount of oxazoline groups added in an unopened state). Equivalent to.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-5 and TB-1 to TB-6) is as follows.

(Preparation of two-component developer)
100 parts by mass of developer carrier and 10 parts by mass of toner (evaluation target: any of toners TA-1 to TA-5 and TB-1 to TB-6) are mixed for 30 minutes using a ball mill, A two-component developer was prepared. 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, image density, fogging, and toner scattering were evaluated by the following procedure.

(Print life test)
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 method is put into a developing device of an evaluation machine, and a replenishing toner (evaluation object: any one of toners TA-1 to TA-5 and TB-1 to TB-6) is evaluated. In the toner container. The developing bias of the evaluator (specifically, the voltage between the developing sleeve and the magnet roll) was adjusted so that the initial image density (measuring device: “RD914” manufactured by X-Rite) was 1.20.

  Subsequently, in the environment of temperature 20 ° C. and humidity 50% 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, a sample image including a solid portion and a blank portion was printed on a recording medium (evaluation paper) using the evaluation machine. Then, the reflection density (ID: image density) of the solid portion of the sample image on the printed recording medium was measured using a reflection densitometer (“RD914” manufactured by X-Rite).

  When the measured image density (ID) was 1.00 or more, it was evaluated as ◯ (good), and when it was less than 1.00, it was evaluated as x (not good).

After the first printing durability test, continuous printing is performed on 2000 sheets of paper (A4 size plain paper) at a printing rate of 20% using the evaluation machine in an environment of a temperature of 20 ° C. and a humidity of 50% RH. A printing durability test was conducted. During the second printing durability test, every time 50 sheets were printed, a reflection densitometer (“RD914” manufactured by X-Rite) was used to measure the reflection density of the blank portion on the printed paper. 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 (that is, the maximum fog density) among all the fog densities (FD) measured at each timing during the second printing durability test (timing for every 50 sheets printed) was determined.

  When the measured maximum fog density was 0.010 or less, it was evaluated as ◯ (good), and when it was over 0.010, it was evaluated as x (not good).

  After the second printing durability test, all of the toner scattered in the developing device of the evaluation machine was collected. Then, the mass of the collected toner (that is, the toner scattering amount) was measured.

  When the measured toner scattering amount was less than 80 mg, it was evaluated as “good”, and when the toner scattering amount was 80 mg or more, it was evaluated as “poor” (not good).

[Evaluation results]
Table 2 shows the results of evaluating the image density, fog (fogging density), and toner scattering (toner scattering amount) for each of toners TA-1 to TA-5 and TB-1 to TB-6.

  The toners TA-1 to TA-5 (positively chargeable toners according to Examples 1 to 5) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-5 includes a plurality of toner particles each including toner base particles and an external additive attached to the surface of the toner base particles. The external additive contained powder of coated titania particles (specifically, particles comprising titania particles and a coat layer covering the titania particles). The coating layer contained a specific vinyl copolymer (specifically, a copolymer of two or more vinyl compounds including at least the compound represented by the above formula (1)) (the above-mentioned “Toner TA-”). (Refer to the manufacturing method of "External additive for 1-TA-5"). The amount of unopened OXZ (specifically, the amount of unopened oxazoline groups contained in 1 g of the powder of coated titania particles) was 0.100 mmol or more and 0.600 mmol or less (see Table 1). The amount of ring-opened OXZ (specifically, the amount of oxazoline groups in the coating layer that is ring-opened by reaction with the functional group present on the surface of the titania particles contained in 1 g of the powder of coated titania particles) is 0. It was 100 mmol or more and 0.400 mmol or less (see Table 1).

  As shown in Table 2, each of the toners TA-1 to TA-5 was able to continuously form high-quality images while suppressing fogging and toner scattering during continuous printing.

  In the toner TB-3 (positively chargeable toner according to Comparative Example 3), the coating layer of the external additive peeled off during the printing durability test, and the chargeability of the toner fluctuated.

  With toner TB-4 (positively chargeable toner according to Comparative Example 4), the developability of the toner was poor. The reason for this is considered to be that the coated titania particles no longer act to improve the developability of the toner by covering the titania particles with a coating layer having an excessive amount of ring-opening OXZ.

  In toners TB-5 and TB-6 (positively chargeable toners according to Comparative Examples 5 and 6), the surface treatment agent of the external additive was scraped during the printing durability test, and the chargeability of the toner fluctuated.

  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-300) in the external additive coating layer forming step. As a result, good results (◯) were obtained in all evaluations.

  Each of the positively chargeable toner and the two-component developer according to the present invention can be used for forming an image in, for example, a copying machine, a printer, or a multifunction machine.

10 Toner Particles 11 Toner Base Particles 13 Coated Titania Particles (External Additive)
20 Carrier particles 131 Titania particles 132 Coat layer

Claims (9)

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 titania particles including titania particles and a coat layer covering the titania particles,
The coat layer contains a copolymer of two or more kinds of vinyl compounds including at least a compound represented by the following formula (1),
The amount of unopened oxazoline groups contained in 1 g of the powder of the coated titania particles is 0.100 mmol or more and 0.600 mmol or less,
The amount of the oxazoline group in the coating layer contained in 1 g of the powder of the coated titania particles and ring-opened by the reaction with the functional group present on the surface of the titania particles is 0.100 mmol or more and 0.400 mmol or less. A positively chargeable toner.

[In Formula (1), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent. ] The titania particles are a titania substrate that is not surface-treated,
The coat layer covers the entire surface of the titania particles,
The particle diameter of the titania particles in the powder of the coated titania particles is 15 nm or more and 50 nm or less in number average.
The positively chargeable toner according to claim 1, wherein an amount of the powder of the coated titania 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 external additive does not contain silica particles.   The positive charge according to any one of claims 1 to 3, wherein the two or more vinyl compounds include one or more vinyl compounds selected from the group consisting of styrene monomers and acrylic acid 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 4, which is a monomer copolymer.   The positively chargeable toner according to claim 1, wherein the toner base particles are non-capsule toner base particles containing a polyester resin and containing no oxazoline group.   The positively chargeable toner according to claim 6, wherein the toner base particles are pulverized toner. A positively chargeable toner according to any one of claims 1 to 7 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. An external additive for toner comprising powder of coated titania particles comprising titania particles and a coating layer covering the titania particles,
The coat layer contains a copolymer of two or more kinds of vinyl compounds including at least a compound represented by the following formula (1),
The amount of the unopened oxazoline group contained in 1 g of the external additive for toner is 0.100 mmol or more and 0.600 mmol or less,
The amount of the oxazoline group in the coating layer that is ring-opened by reaction with the functional group present on the surface of the titania particles contained in 1 g of the external additive for toner is 0.100 mmol or more and 0.400 mmol or less. An external additive for toner.

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

Images