Positively chargeable toner

Abstract

To provide a positive charge type toner having high transfer efficiency and excellent in charge stability.SOLUTION: The positively chargeable toner includes toner particles. The toner particles each include a toner mother particle and an external additive attached to a surface of the toner mother particle. The external additive includes resin-containing particles containing a resin. The resin-containing particles further contain an anionic surfactant. The resin-containing particles are surface-treated with a silane coupling agent. The resin-containing particles have a number-average primary particle size of 60nm or more and 100nm or less. An area ratio of a region covered with the resin-containing particles to a surface region of the toner base particle is 15% or more and 30% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a positively charging toner. [Background technology]

[0002] In image formation using an image forming apparatus, a toner with high transfer efficiency is required. For example, Patent Document 1 discloses a toner in which at least negatively charged resin fine particles and positively charged inorganic fine particles are attached to the surface of toner base particles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-240158 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the toner disclosed in Patent Document 1 has room for improvement in terms of transfer efficiency, and is also insufficient in terms of charging stability.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a positively charged toner having high transfer efficiency and excellent charging stability. [Means for solving the problem]

[0006] The positively charged toner according to the present invention includes toner particles. The toner particles include toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes resin-containing particles containing a resin. The resin-containing particles further contain an anionic surfactant. The resin-containing particles are surface-treated with a silane coupling agent. The number-average primary particle diameter of the resin-containing particles is 60 nm or more and 100 nm or less. The area ratio of the surface area of ​​the toner base particles that is covered with the resin-containing particles is 15% or more and 30% or less. [Effects of the Invention]

[0007] The positively charged toner according to the present invention has high transfer efficiency and excellent charge stability. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described. First, the terms used in this specification will be described. A toner is an aggregate of toner particles (for example, powder). An external additive is an aggregate of external additive particles (for example, powder). Unless otherwise specified, the evaluation results (values ​​indicating shape, physical properties, etc.) of a powder (more specifically, powder of toner particles, powder of external additive particles, etc.) are the number average of values ​​measured for each of a considerable number of particles selected from the powder. The cumulative 50% value (D 50Unless otherwise specified, the mean diameter is the median diameter measured using a laser diffraction / scattering particle size analyzer (HORIBA, Ltd., LA-950). Unless otherwise specified, the number-average primary particle diameter of a powder is the number-average value of the equivalent circle diameters of primary particles (Heywood diameter: the diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a scanning electron microscope. The number-average primary particle diameter of a powder is, for example, the number-average value of the equivalent circle diameters of 100 primary particles. Unless otherwise specified, the strength of chargeability is the ease of triboelectric charging with respect to a standard carrier provided by the Imaging Society of Japan. For example, the object to be measured is triboelectrically charged by stirring it with standard carriers provided by the Imaging Society of Japan (anionic: N-01, cationic: P-01). For example, a Q / m meter (Trek Model 212HS) was used to measure the charge per unit mass of a test object before and after triboelectric charging. The greater the change in charge per unit mass before and after triboelectric charging, the stronger the chargeability of the test object. Unless otherwise specified, the melting point (Mp) is the temperature of the maximum endothermic peak in the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) measured using a differential scanning calorimeter (Seiko Instruments Inc. DSC-6220). This endothermic peak appears due to melting of the crystallized portion. Hereinafter, the compound name may be followed by "system" to collectively refer to the compound and its derivatives. When the compound name is followed by "system" to refer to a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacrylic may be collectively referred to as "(meth)acrylic." Acryloxy and methacryloxy may be collectively referred to as "(meth)acryloxy." Each component described in this specification may be used alone or in combination of two or more. The terms used in this specification have been explained above.

[0009] [Positively charged toner] The positively charged toner of this embodiment will be described below. The positively charged toner of this embodiment includes toner particles. The toner particles include toner base particles and external additives attached to the surfaces of the toner base particles. The external additives include resin-containing particles containing a resin. The resin-containing particles further contain an anionic surfactant. The resin-containing particles are surface-treated with a silane coupling agent. The number-average primary particle diameter of the resin-containing particles is 60 nm or more and 100 nm or less. The area ratio of the surface area of ​​the toner base particles covered with the resin-containing particles is 15% or more and 30% or less.

[0010] Hereinafter, the "positively charged toner" may be simply referred to as "toner." Furthermore, the "area ratio of the surface area of ​​the toner base particle that is covered with the resin-containing particles" may be referred to as the "predetermined coverage."

[0011] The toner of the present embodiment has the above-described structure, and therefore has high transfer efficiency and excellent charge stability. The reasons for this are presumed to be as follows.

[0012] External additives attached to the surface of toner base particles may become embedded or detached due to mechanical stress caused by agitation within the developing device. To prevent the embedding or detachment of external additives, large-diameter spacer particles may be included in the external additive. When silica particles are used as large-diameter spacer particles, the silica particles must be treated to be positively charged, which can result in defects such as fogging. On the other hand, when general resin particles are used as spacer particles instead of silica particles, the adhesive force of the resin particles to the photoreceptor drum is strong, and the adhesive force of the toner particles to the photoreceptor drum is also strong. As a result, it becomes difficult for toner particles to be transferred from the photoreceptor drum to paper, which tends to reduce transfer efficiency.

[0013] Therefore, in the toner of this embodiment, the resin-containing particles contain an anionic surfactant. By containing the anionic surfactant in the resin-containing particles, the resin-containing particles exhibit weak positive charging properties in frictional charging with the carrier. By the resin-containing particles, which are spacer particles that frequently come into contact with the photosensitive drum, exhibiting weak positive charging properties, the electrostatic adhesion force of the toner particles to the photosensitive drum can be reduced.

[0014] Furthermore, in the toner of this embodiment, the resin-containing particles are surface-treated with a silane coupling agent, which reduces the adhesive force of the resin-containing particles to the photosensitive drum, and also reduces the adhesive force of the toner particles to the photosensitive drum.

[0015] Furthermore, in the toner of this embodiment, the number average primary particle diameter of the resin-containing particles is 60 nm or more. When the number average primary particle diameter of the resin-containing particles is 60 nm or more, the resin-containing particles function sufficiently as spacers that reduce the frequency of contact between the photosensitive drum and the toner base particles.

[0016] Furthermore, in the toner of this embodiment, the predetermined coverage is 15% or more. When the predetermined coverage is 15% or more, the toner base particles are sufficiently covered with the resin-containing particles. Therefore, the resin-containing particles function sufficiently as spacers that reduce the frequency of contact between the photosensitive drum and the toner base particles.

[0017] By reducing the adhesive force of the toner particles to the photosensitive drum and the frequency of contact between the photosensitive drum and the toner base particles, the toner particles are easily separated from the photosensitive drum during transfer, improving the toner transfer efficiency.

[0018] On the other hand, if the number-average primary particle diameter of the resin-containing particles is too large, the resin-containing particles are more likely to detach from the toner base particles. Furthermore, if the predetermined coverage is too high, the amount of resin-containing particles becomes excessive, making the resin-containing particles more likely to detach from the toner base particles. If the detached resin-containing particles adhere to the carrier, carrier contamination occurs, and the charge stability of the toner decreases. Therefore, in the toner of this embodiment, the number-average primary particle diameter of the resin-containing particles is set to 100 nm or less. Furthermore, in the toner of this embodiment, the predetermined coverage is set to 30% or less. These factors make it difficult for the resin-containing particles to detach from the toner base particles, thereby suppressing carrier contamination. As a result, the charge stability of the toner is improved.

[0019] The reasons why the toner of this embodiment has high transfer efficiency and excellent charge stability have been explained above.

[0020] [Toner particles] The toner particles contained in the toner of this embodiment include toner base particles and an external additive. The external additive is attached to the surface of the toner base particles. The toner containing the toner particles is suitably used as a positively charged toner for developing electrostatic latent images. The toner base particles are, for example, non-encapsulated toner particles that do not have a shell layer. However, the toner base particles may also be encapsulated toner particles that include a toner core and a shell layer that covers the toner core. The toner is also used as a two-component developer mixed with a carrier, for example. However, the toner may also be used as a one-component developer without being mixed with a carrier. In order to obtain a toner suitable for image formation, the D of the toner particles is adjusted. 50 The particle size is preferably 4 μm or more and 9 μm or less. The external additives provided on the toner particles and the toner base particles will be described below.

[0021] [External additives] The external additive contains resin-containing particles as external additive particles, and may further contain other external additive particles in addition to the resin-containing particles, as necessary.

[0022] <Resin-containing particles> As already mentioned, the number-average primary particle diameter of the resin-containing particles is 60 nm or more and 100 nm or less. In order to improve the transfer efficiency of the toner, the number-average primary particle diameter of the resin-containing particles is preferably 70 nm or more, more preferably 75 nm or more. In order to improve the charging stability of the toner, the number-average primary particle diameter of the resin-containing particles is preferably 90 nm or less, more preferably 85 nm or less.

[0023] As already mentioned, the predetermined coverage is 15% or more and 30% or less. In order to improve the transfer efficiency of the toner, the predetermined coverage is preferably 20% or more. In order to improve the charging stability of the toner, the predetermined coverage is preferably 25% or less. The predetermined coverage is measured by the same method as in the examples described below or a method equivalent thereto. The predetermined coverage can be adjusted, for example, by changing one or both of the amount of resin-containing particles added relative to the mass of the toner base particles and the type of resin-containing particles.

[0024] In order to adjust the predetermined coverage rate to a value within the desired range, the content of the resin-containing particles is preferably 0.7 parts by mass or more and 1.3 parts by mass or less, and more preferably 0.8 parts by mass or more and 1.2 parts by mass or less, relative to 100.0 parts by mass of the toner base particles.

[0025] The external additive may contain only resin-containing particles as external additive particles, or may contain other external additive particles in addition to the resin-containing particles. The content of the resin-containing particles in the external additive particles is preferably 30% by mass or more and 50% by mass or less, and more preferably 35% by mass or more and 45% by mass or less.

[0026] The resin-containing particles contain a resin. The resin-containing particles further contain an anionic surfactant. The resin-containing particles are surface-treated with a silane coupling agent. Hereinafter, "resin-containing particles before being surface-treated with a silane coupling agent" may be referred to as "untreated particles."

[0027] (resin) The resin content in the resin-containing particles is preferably 80% by mass or more and 99% by mass or less, more preferably 85% by mass or more and 95% by mass or less, and even more preferably 89% by mass or more and 91% by mass or less.

[0028] In order to obtain a toner with high transfer efficiency and excellent charging stability, the resin contained in the resin-containing particles preferably contains a styrene-acrylic resin, and more preferably a styrene-acrylic resin containing a silane bond. The silane bond is represented by the chemical formula "-SiR2-". In the chemical formula "-SiR2-", R represents a hydrogen atom or an alkyl group. When the styrene-acrylic resin contains a silane bond, the adhesive force of the resin-containing particles to the photoreceptor drum can be further reduced.

[0029] In order to further reduce the adhesive force of the resin-containing particles to the photoreceptor drum, the styrene-acrylic resin containing a silane bond is preferably a polymer of styrene or a derivative thereof, (meth)acrylic acid or a derivative thereof, a silane compound having at least one (meth)acryloxy group, and a crosslinker having at least two unsaturated bonds. Hereinafter, "styrene or a derivative thereof" may be referred to as "styrene-based monomer." Furthermore, "(meth)acrylic acid or a derivative thereof" may be referred to as "acrylic acid-based monomer."

[0030] Examples of styrene-based monomers include styrene, alkylstyrene, hydroxystyrene, and halogenated styrene. Examples of alkylstyrenes include α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, and 4-t-butylstyrene. Examples of hydroxystyrenes include p-hydroxystyrene and m-hydroxystyrene. Examples of halogenated styrenes include α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. Styrene is preferred as the styrene-based monomer. The styrene-based monomer does not have, for example, a silane bond. The content of repeating units derived from styrene-based monomers in the resin is preferably 25% by mass or more and 40% by mass or less, more preferably 30% by mass or more and 35% by mass or less.

[0031] Examples of acrylic acid monomers include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid alkyl esters, and (meth)acrylic acid hydroxyalkyl esters. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of (meth)acrylic acid hydroxyalkyl esters include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of acrylic acid monomers include (meth)acrylic acid alkyl esters, more preferably (meth)acrylic acid alkyl esters having an alkyl group with 1 to 3 carbon atoms, even more preferably methyl (meth)acrylate, and particularly preferably methyl methacrylate. The acrylic acid monomer does not have a silane bond, for example. The content of repeating units derived from acrylic acid-based monomers in the resin is preferably 35% by mass or more and 50% by mass or less, and more preferably 40% by mass or more and 45% by mass or less.

[0032] The silane compound having at least one (meth)acryloxy group has a silane bond. By using the silane compound having at least one (meth)acryloxy group as a monomer, a silane bond can be introduced into the styrene-acrylic resin.

[0033] As the silane compound having at least one (meth)acryloxy group, a silane coupling agent having at least one (meth)acryloxy group is preferred. Hereinafter, "a silane coupling agent for surface treating resin-containing particles" may be referred to as "a silane coupling agent for surface treatment," and "a silane coupling agent for synthesizing a resin contained in a resin-containing particle" may be referred to as "a silane coupling agent for resin synthesis." By introducing a repeating unit derived from a silane coupling agent for resin synthesis into a resin, when surface treatment is performed, a silanol group generated by hydrolysis of an alkoxysilyl group in the repeating unit derived from the silane coupling agent for resin synthesis and a silanol group generated by hydrolysis of the silane coupling agent for surface treatment undergo a condensation reaction, thereby facilitating the surface treatment.

[0034] Examples of silane coupling agents for resin synthesis having a (meth)acryloxy group include 3-(meth)acryloxypropyl alkyl dialkoxy silanes and 3-(meth)acryloxypropyl trialkoxy silanes. Examples of 3-(meth)acryloxypropyl alkyl dialkoxy silanes include 3-methacryloxypropyl methyl dimethoxy silane and 3-methacryloxypropyl methyl diethoxy silane. Examples of 3-(meth)acryloxypropyl trialkoxy silanes include 3-methacryloxypropyl trimethoxy silane, 3-methacryloxypropyl triethoxy silane, and 3-acryloxypropyl trimethoxy silane. As a silane compound having at least one (meth)acryloxy group, 3-methacryloxypropyl methyl diethoxy silane is preferred. The content of repeating units derived from a silane compound having at least one (meth)acryloxy group in the resin is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less.

[0035] Examples of unsaturated bonds contained in the crosslinking agent include carbon-carbon double bonds. Examples of crosslinking agents having two or more unsaturated bonds include N,N'-methylenebisacrylamide, divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate. Ethylene glycol dimethacrylate is preferred as a crosslinking agent having two or more unsaturated bonds. Crosslinking agents having two or more unsaturated bonds do not have silane bonds, for example. The content of repeating units derived from a crosslinking agent having two or more unsaturated bonds in the resin is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less.

[0036] (anionic surfactant) In order to further reduce the electrostatic adhesion of the toner particles to the photoreceptor drum, the anionic surfactant contains a sulfate anion group (-O-SO2-O - group) or sulfonate anion group (-SO2-O - It is preferable that the surfactant has a sulfate anion group. Examples of anionic surfactants having a sulfate anion group include alkyl sulfate ester salts having an alkyl group with 10 to 25 carbon atoms, more specifically sodium lauryl sulfate. Examples of anionic surfactants having a sulfonate anion group include alkyl benzene sulfonates having an alkyl group with 10 to 25 carbon atoms, more specifically sodium dodecyl benzene sulfonate.

[0037] Resin-containing particles can be produced, for example, by polymerizing a monomer in a solution containing a monomer for synthesizing the resin and an anionic surfactant. During the polymerization reaction, the anionic surfactant tends to orient at the interface between the monomer and the solution. Therefore, after removing the untreated particles from the solution after the polymerization reaction, the untreated particles can be surface-treated with a silane coupling agent for surface treatment without washing the untreated particles (or without completely removing the anionic surfactant present on the surface of the untreated particles in the washing process). This allows the anionic surfactant to be present near the surface of the resin-containing particles (e.g., on the surface of the untreated particles). More specifically, the near-surface area of ​​the resin-containing particles refers to the surface of a base particle made of a resin and inside a surface-treatment film made of a silane coupling agent. In this case, the resin-containing particles have a base particle made of a resin, an anionic surfactant attached to the surface of the base particle, and a surface-treatment film made of a silane coupling agent that covers the base particle to which the anionic surfactant is attached. In this case, the anionic surfactant is present between the surface of the base particle and the surface-treatment film. This arrangement of the anionic surfactant further reduces the positive chargeability of the resin-containing particles. As a result, the electrostatic adhesion of the toner particles to the photosensitive drum can be further reduced.

[0038] In order to further reduce the electrostatic adhesion of toner particles to a photoreceptor drum, the content of the anionic surfactant in the surface region of the resin-containing particle is preferably higher than the content of the anionic surfactant in the internal region of the resin-containing particle. The surface region of the resin-containing particle is, for example, a region that includes the surface of the resin-containing particle and has a depth of 1 / 10 of the radius of the resin-containing particle in the direction from the surface to the center. The internal region of the resin-containing particle is, for example, a spherical region centered on the center of the resin-containing particle, and the radius of the internal region is, for example, 1 / 10 of the radius of the resin-containing particle.

[0039] In order to further reduce the electrostatic adhesion force of the toner particles to the photosensitive drum, the ratio Ws / Wr of the mass of the anionic surfactant Ws to the mass of the resin Wr is preferably 0.01 or more and 0.50 or less, more preferably 0.05 or more and 0.20 or less, and even more preferably 0.10 or more and 0.12 or less.

[0040] In order to further reduce the electrostatic adhesion of the toner particles to the photosensitive drum, the surfactant content in the resin-containing particles is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, and even more preferably 9% by mass or more and 11% by mass or less.

[0041] (Silane coupling agent for surface treatment) When the surface of untreated particles is treated with a surface-treating silane coupling agent, the silanol groups (-SiOH groups) generated by hydrolysis of the surface-treating silane coupling agent undergo a self-condensation reaction on the surface of the untreated particles. In addition, if the untreated particles have hydroxyl groups on their surfaces (for example, silanol groups generated by hydrolysis of alkoxysilyl groups in the repeating units derived from the silane coupling agent for resin synthesis), the hydroxyl groups on the surface of the untreated particles and the silanol groups (-SiOH groups) generated by hydrolysis of the surface-treating silane coupling agent undergo a condensation reaction.

[0042] The surface treatment silane coupling agent may have the same chemical structure as the resin synthesis silane coupling agent. However, in order to facilitate the surface treatment of the resin-containing particles, it is preferable that the surface treatment silane coupling agent has a different chemical structure from the resin synthesis silane coupling agent. For example, the surface treatment silane coupling agent does not need to have a (meth)acryloxy group.

[0043] Examples of silane coupling agents for surface treatment include alkylalkoxysilanes. The alkyl group contained in the alkylalkoxysilane is preferably an alkyl group having 3 to 8 carbon atoms. The alkoxy group contained in the alkylalkoxysilane is preferably an alkoxy group having 1 to 3 carbon atoms.

[0044] Examples of alkylalkoxysilanes include propyltrimethoxysilane (more specifically, n-propyltrimethoxysilane, isopropyltrimethoxysilane, etc.), propyltriethoxysilane (more specifically, n-propyltriethoxysilane, isopropyltriethoxysilane, etc.), butyltrimethoxysilane (more specifically, n-butyltrimethoxysilane, isobutyltrimethoxysilane, etc.), butyltriethoxysilane (more specifically, n-butyltriethoxysilane, isobutyltriethoxysilane, etc.), hexyltrimethoxysilane (more specifically, n-hexyltrimethoxysilane, etc.), hexyltriethoxysilane (more specifically, n-hexyltriethoxysilane, etc.), octyltrimethoxysilane (more specifically, n-octyltrimethoxysilane, etc.), and octyltriethoxysilane (more specifically, n-octyltriethoxysilane, etc.). As the silane coupling agent for surface treatment, isobutyltrimethoxysilane or propyltrimethoxysilane is preferred.

[0045] In order to further reduce the adhesion force of the toner particles to the photosensitive drum, the content of the surface treatment silane coupling agent is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.8 parts by mass or more and 1.3 parts by mass or less, relative to 50.0 parts by mass of the untreated particles.

[0046] In order to further reduce the adhesion of the toner particles to the photosensitive drum, the content of the surface treatment silane coupling agent in the resin-containing particles is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 1.0% by mass or more and 3.0% by mass or less, and even more preferably 1.5% by mass or more and 2.5% by mass or less.

[0047] (Method of manufacturing resin-containing particles) As already mentioned, resin-containing particles can be produced, for example, by polymerizing a monomer in a liquid containing a monomer for synthesizing the resin and an anionic surfactant. The number-average primary particle diameter of the resin-containing particles can be adjusted, for example, by changing at least one of the stirring speed of the liquid in the polymerization reaction and the reaction time of the polymerization reaction. The higher the stirring speed of the liquid in the polymerization reaction, the smaller the number-average primary particle diameter of the resin-containing particles. Furthermore, the shorter the reaction time of the polymerization reaction, the smaller the number-average primary particle diameter of the resin-containing particles.

[0048] <Other external additive particles> Examples of other external additives include inorganic particles, more specifically, silica particles and particles of metal oxides (specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.). The surfaces of the other external additive particles may be subjected to one or both of a positive charging treatment and a hydrophobic treatment. The number average primary particle diameter of the other external additive particles is preferably 5 nm or more and 80 nm or less. The content of the other external additive particles is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 2.0 parts by mass or less, relative to 100.0 parts by mass of the toner base particles. The content ratio of the other external additive particles in the external additive particles is preferably 50% by mass or more and 70% by mass or less, and more preferably 55% by mass or more and 65% by mass or less.

[0049] [Toner base particles] The toner base particles contain a binder resin. In addition to the binder resin, the toner base particles may further contain an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and other components other than those described above) as needed.

[0050] <Binder resin> In the toner base particles, for example, the binder resin accounts for 70% by mass or more of all components. Therefore, it is thought that the properties of the binder resin have a significant impact on the properties of the entire toner base particles. By using a combination of multiple resins as the binder resin, it is possible to adjust the properties of the binder resin (more specifically, the glass transition point, etc.).

[0051] To obtain a toner with excellent low-temperature fixability, the toner base particles preferably contain a thermoplastic resin as a binder resin, and more preferably contain the thermoplastic resin in a proportion of 85% by mass or more of the total binder resin. Examples of thermoplastic resins include styrene resins, acrylic ester resins, olefin resins (more specifically, polyethylene resins, polypropylene resins, etc.), vinyl resins (more specifically, vinyl chloride resins, polyvinyl alcohol, vinyl ether resins, N-vinyl resins, etc.), polyester resins, polyamide resins, and urethane resins. Copolymers of these resins, i.e., copolymers in which any repeating unit is introduced into the above resins (more specifically, styrene-acrylic resins, styrene-butadiene resins, etc.), can also be used as binder resins.

[0052] In order to obtain a toner having excellent low-temperature fixability, the toner base particles preferably contain a polyester resin as a binder resin, and more preferably contain the polyester resin in a proportion of 80% by mass to 100% by mass of the total binder resin. The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polycarboxylic acids. Examples of polyhydric alcohols used to synthesize the polyester resin include dihydric alcohols (more specifically, aliphatic diols, bisphenols, etc.) and trihydric or higher alcohols, such as those shown below. Examples of polycarboxylic acids used to synthesize the polyester resin include dicarboxylic acids and tricarboxylic or higher carboxylic acids, such as those shown below. Instead of the polycarboxylic acid, a polycarboxylic acid derivative capable of forming an ester bond by polycondensation, such as a polycarboxylic acid anhydride or a polycarboxylic acid halide, may be used.

[0053] Examples of aliphatic diols, which are specific examples of dihydric alcohols, include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α,ω-alkanediols (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, and polytetramethylene glycol.

[0054] Examples of bisphenols, which are specific examples of dihydric alcohols, include bisphenol A, hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A.

[0055] Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0056] Examples of dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, 1,10-decanedicarboxylic acid, succinic acid, alkylsuccinic acids (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, etc.), and alkenylsuccinic acids (more specifically, n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, etc.).

[0057] Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (i.e., trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

[0058] The polyester resin is preferably a condensation polymer of at least one bisphenol, a dicarboxylic acid, and a tricarboxylic acid, and more preferably a condensation polymer of a bisphenol A ethylene oxide adduct, a bisphenol A propylene oxide adduct, fumaric acid, and trimellitic acid.

[0059] In order to obtain a toner having excellent low-temperature fixing properties, the polyester resin is preferably amorphous. It is often impossible to measure a clear melting point for amorphous polyester resins. Therefore, polyester resins that cannot be determined to have a clear endothermic peak in an endothermic curve measured using a differential scanning calorimeter can be considered to be amorphous polyester resins.

[0060] <Coloring agent> As the colorant, a known pigment or dye can be used in accordance with the color of the toner. In order to form a high-quality image using the toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the binder resin.

[0061] The toner base particles may contain a black colorant. Examples of black colorants include carbon black. The black colorant may also be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

[0062] The toner base particles may contain color colorants, such as yellow colorants, magenta colorants, and cyan colorants.

[0063] The yellow colorant may be, 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. Examples of the yellow colorant include CI 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, and 194), Naphthol Yellow S, Hansa Yellow G, and CI Vat Yellow.

[0064] Examples of magenta colorants that can be used include one or more compounds 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. Examples of magenta colorants include CI 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, and 254).

[0065] The cyan colorant may be, for example, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds, including, for example, CI Pigment Blue (1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66), phthalocyanine blue, CI Vat Blue, and CI Acid Blue.

[0066] <Release agent> A release agent is used, for example, to obtain a toner with excellent offset resistance. To obtain a toner with excellent offset resistance, the amount of release agent is preferably 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the binder resin. Examples of release agents include ester wax, polyolefin wax (more specifically, polyethylene wax, polypropylene wax, etc.), microcrystalline wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, candelilla wax, montan wax, and castor wax. Examples of ester waxes include natural ester wax (more specifically, carnauba wax, rice wax, etc.) and synthetic ester wax.

[0067] <Charge control agent> Charge control agents are used, for example, to obtain toners with excellent charge stability or charge rise characteristics. The charge rise characteristics of a toner are an index of whether the toner can be charged to a predetermined charge level in a short time. To obtain toners with excellent charge stability, the content of the charge control agent is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the binder resin. By incorporating a positively chargeable charge control agent into the toner base particles, the cationic nature (positive chargeability) of the toner base particles can be strengthened. Examples of positively chargeable charge control agents include azine compounds such as pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1,4-thiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline; Examples of dyes include direct dyes such as Fast Red FC, Azin Fast Red 12BK, Azin Violet BO, Azin Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL; acid dyes such as Nigrosine BK, Nigrosine NB, and Nigrosine Z; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzyldecylhexylmethylammonium chloride, decyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride, and dimethylaminopropylacrylamide methyl chloride quaternary salt; and resins containing quaternary ammonium cation groups.

[0068] <Other ingredients> Examples of other components that the toner base particles may contain include magnetic powder, a compatibilizer, and known additives other than those mentioned above.

[0069] [Toner manufacturing method] The method for producing the toner according to the present embodiment includes, for example, a step of producing toner base particles and a step of adding an external additive.

[0070] <Toner base particle manufacturing process> In the process of preparing the toner base particles, the toner base particles are formed by an aggregation method or a pulverization method.

[0071] The aggregation method includes, for example, an aggregation step and a coalescence step. In the aggregation step, fine particles containing components constituting the toner base particles are aggregated in an aqueous medium to form aggregated particles. In the coalescence step, components contained in the aggregated particles are coalesced in the aqueous medium to form toner base particles.

[0072] Next, the pulverization method will be described. The pulverization method allows toner base particles to be produced relatively easily and also enables reduction in production costs. When toner base particles are produced by the pulverization method, the process for producing the toner base particles includes, for example, a kneading process and a pulverization process. The process for producing the toner base particles may further include a mixing process before the kneading process. Furthermore, the process for producing the toner base particles may further include at least one of a fine pulverization process and a classification process after the pulverization process.

[0073] In the mixing step, a binder resin and an internal additive, which is added as needed, are mixed to obtain a mixture. In the kneading step, the toner materials are melted and kneaded to obtain a kneaded product. For example, the mixture obtained in the mixing step is used as the toner material. In the pulverizing step, the kneaded product obtained is cooled to room temperature (25°C), for example, and then pulverized to obtain a pulverized product. If it is necessary to reduce the diameter of the pulverized product obtained in the pulverizing step, a step of further pulverizing the pulverized product (fine pulverizing step) may be performed. Furthermore, if the particle size of the pulverized product is to be uniform, a step of classifying the pulverized product obtained (classifying step) may be performed. Through the above steps, toner base particles, which are the pulverized product, are obtained.

[0074] <External addition process> In the external addition step, the obtained toner base particles are mixed with an external additive using a mixer, and the external additive is adhered to the surface of the toner base particles. The external additive contains at least resin-containing particles. When the external additive is adhered by mixing, the toner base particles and the external additive particles do not chemically react with each other and are fixed physically, not chemically. An example of the mixer is an FM mixer (manufactured by Nippon Coke & Engineering Co., Ltd.). In this way, a toner containing toner particles is produced. [Example]

[0075] Examples of the present invention will be described below, but the present invention is not limited to the scope of the examples.

[0076] [Surfactants] The surfactants used in the preparation of the resin-containing particles are shown below. Surfactant (S-1a): Sodium lauryl sulfate (type: anionic surfactant with sulfate anion group) Surfactant (S-2a): Sodium dodecylbenzenesulfonate (type: anionic surfactant with sulfonate anion group) Surfactant (S-3c): n-Hexadecyltrimethylammonium chloride (type: cationic surfactant) Surfactant (S-4n): Polyoxyethylene lauryl ether (type: nonionic surfactant)

[0077] [Surface treatment agent] The surface treatment agents used in the preparation of the resin-containing particles are shown below. Surface treatment agent (IBTMS): Isobutyltrimethoxysilane Surface treatment agent (PTMS): Propyltrimethoxysilane

[0078] [Preparation of resin-containing particles] The resin-containing particles used in the external addition step were prepared by the following method. The formulation of each resin-containing particle is shown in Table 1 below. The preparation conditions and number average primary particle diameter of each resin-containing particle are shown in Table 2 below.

[0079] [Table 1]

[0080] [Table 2]

[0081] The abbreviations used in Tables 1 and 2 are as follows: Part: Mass part Parts / 50.0 parts: Amount of surface treatment agent per 50.0 parts by mass of untreated particles (unit: parts by mass) MM: methyl methacrylate ST: styrene MSi: 3-methacryloxypropylmethyldiethoxysilane Crosslinker: Ethylene glycol dimethacrylate -:Does not contain any of the relevant ingredients Diameter: Number average primary particle diameter

[0082] <Method for measuring number average primary particle size> The number average primary particle diameter of the resin-containing particles shown in Table 2 was measured using a scanning electron microscope (JSM-7600F manufactured by JEOL Ltd.) In measuring the primary particle diameter, the circle equivalent diameter (Heywood diameter: diameter of a circle having the same area as the projected area of ​​the primary particle) of 100 resin-containing particles was measured, and the number average value was calculated.

[0083] <Resin-containing particles (RA-1)> A four-neck flask equipped with a stirrer, condenser, thermometer, and nitrogen inlet tube was charged with 600 parts by weight of ion-exchanged water, 10 parts by weight of benzoyl peroxide (initiator), 60 parts by weight of methyl methacrylate, 45 parts by weight of styrene, 15 parts by weight of 3-methacryloxypropylmethyldiethoxysilane, 15 parts by weight of ethylene glycol dimethacrylate (crosslinker), and 15 parts by weight of surfactant (S-1a). While stirring the contents of the flask, nitrogen gas was introduced into the flask to create a nitrogen atmosphere. Next, while stirring the contents of the flask, the temperature of the flask was raised to 90°C in a nitrogen atmosphere. Next, under conditions of a nitrogen atmosphere and a temperature of 90°C, the contents of the flask were stirred at a stirring speed of 800 rpm (hereinafter referred to as stirring speed Y) for 3 hours (hereinafter referred to as reaction time X) to obtain an emulsion containing the reaction product. The resulting emulsion was dried using a spray dryer to obtain untreated particles. Next, 1.0 part by mass of the surface treatment agent (IBTMS) was sprayed onto 50.0 parts by mass of untreated particles while stirring in a stainless steel vessel equipped with a stirrer. After spraying, the contents of the vessel were held at 60°C for 10 hours in a nitrogen atmosphere. The contents of the vessel were then heated to 150°C and held at 150°C for 5 hours in a nitrogen atmosphere. Residual volatile components were then removed from the contents of the vessel using a nitrogen stream to obtain resin-containing particles (RA-1). The resin-containing particles (RA-1) contained a resin (more specifically, a polymer of methyl methacrylate, styrene, 3-methacryloxypropylmethyldiethoxysilane, and ethylene glycol dimethacrylate) and a surfactant (S-1a), and were surface-treated with the surface treatment agent (IBTMS).

[0084] <Resin-containing particles (RA-2) to (RA-5), (RB-1) to (RB-2), and (RB-4) to (RB-5)> Resin-containing particles (RA-2) to (RA-5), (RB-1) to (RB-2), and (RB-4) to (RB-5) were prepared in the same manner as in the preparation of resin-containing particle (RA-1), except that the type and amount of surfactant and the type and amount of surface treatment agent were as shown in Table 1, and the reaction time X and stirring speed Y were as shown in Table 2.

[0085] <Resin-containing particles (RB-3)> Resin-containing particles (RB-3) were prepared in the same manner as for preparing resin-containing particles (RA-1), except that untreated particles were used as resin-containing particles (RB-3) without spraying a surface treatment agent.

[0086] [Synthesis of binder resin] The polyester resin PE used as the binder resin in the toner base particle production process was synthesized using the following method. A reaction vessel equipped with a thermometer (thermocouple), a dehydration tube, a nitrogen inlet tube, and a stirring blade was placed in an oil bath. 1575 g of bisphenol A propylene oxide adduct (BPA-PO), 163 g of bisphenol A ethylene oxide adduct (BPA-EO), 377 g of fumaric acid, and 4 g of dibutyltin oxide catalyst were added to the reaction vessel. A nitrogen atmosphere was then created inside the reaction vessel, and the temperature inside the reaction vessel was raised to 220°C using an oil bath while stirring the contents. Under the nitrogen atmosphere and at 220°C, the contents of the reaction vessel were polymerized for 8 hours while distilling off by-product water. The pressure inside the reaction vessel was then reduced, and the contents of the reaction vessel were polymerized for an additional hour under a reduced pressure (pressure: 60 mmHg) at 220°C. Subsequently, the temperature inside the reaction vessel was lowered to 210°C, and then 336 g of trimellitic anhydride was added to the reaction vessel. The contents of the reaction vessel were then subjected to a polymerization reaction under reduced pressure (pressure: 60 mmHg) at a temperature of 210°C. The reaction product was then removed from the reaction vessel and cooled to obtain an amorphous polyester resin PE.

[0087] [Toner production] The toners shown in Table 3 below were prepared by the following method.

[0088] <Toner (T-A1)> (Toner base particle manufacturing process) Using an FM mixer ("FM-10B" manufactured by Nippon Coke and Engineering Co., Ltd.), 100 parts by weight of binder resin, 4 parts by weight of colorant, 1 part by weight of charge control agent, and 5 parts by weight of release agent were mixed to obtain a mixture. The polyester resin PE obtained above was used as the binder resin. Copper phthalocyanine blue pigment (CI Pigment Blue 15:3) was used as the colorant. A quaternary ammonium salt ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Industries Co., Ltd.) was used as the charge control agent. Carnauba wax ("Special Carnauba Wax No. 1" manufactured by Kato Yoko Co., Ltd.) was used as the release agent. The resulting mixture was melted and kneaded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The kneading was performed under conditions of a set temperature of 120°C, a rotation speed of 150 rpm, and a throughput of 5 kg / hour. The kneaded material was pulverized using a mechanical pulverizer ("Turbo Mill" manufactured by Freund Turbo Corporation) to obtain a pulverized material. The pulverized material was classified using a classifier ("Elbow Jet" manufactured by Nittetsu Mining Co., Ltd.). 50 Powdery toner base particles having a particle size of 6.8 μm were obtained.

[0089] (External addition process) 100.0 parts by mass of toner base particles, 1.5 parts by mass of silica particles, and 1.0 part by mass of resin-containing particles (RA-1) were mixed for 5 minutes at 4,000 rpm using an FM mixer ("FM-10B" manufactured by Nippon Coke & Engineering Co., Ltd.). The silica particles used were "AEROSIL (registered trademark) REA90" manufactured by Nippon Aerosil Co., Ltd. (dry silica particles with a surface treatment to impart positive charging properties, number-average primary particle diameter of 20 nm). By mixing, the external additives (silica particles and resin-containing particles (RA-1)) were attached to the toner base particles. The resulting mixture was sieved using a 200-mesh sieve (openings of 75 μm) to obtain toner (T-A1).

[0090] <Toner (T-A2) to (T-A7) and (T-B1) to (T-B7)> Toners (T-A2) to (T-A7) and (T-B1) to (T-B7) were prepared in the same manner as toner (T-A1), except that the types and amounts of resin-containing particles used in the external addition step were as shown in Table 3 below.

[0091] [measurement] The predetermined coverage rate of each toner was measured by the following method, and the measurement results are shown in Table 3 below.

[0092] <Prescribed coverage rate> A field-emission scanning electron microscope (FE-SEM) (JEOL Ltd., "JSM-7600F") was used to obtain backscattered electron images (surface images) of toner particles contained in the toner. Image analysis software (Mitani Shoji Co., Ltd., "WinROOF") was used to analyze the obtained surface images and determine the predetermined coverage. The predetermined coverage corresponds to the area ratio of the surface area of ​​the toner base particle covered by resin-containing particles. Regarding areas on the surface of the toner base particle where multiple types of external additive particles overlap, the outermost external additive particle (specifically, the external additive particle located highest relative to the surface of the toner base particle) was determined to cover that area. For example, on the surface of the toner base particle, the area where silica particles and resin-containing particles overlap in this order was determined to be covered by the outermost resin-containing particle. The predetermined coverage was measured in 10 fields of view for each toner particle, and the arithmetic average of the 10 measurements was determined to be the predetermined coverage of that toner.

[0093] [evaluation] The transferability and charging stability of each toner were evaluated by the following methods, and the evaluation results are shown in Table 3 below.

[0094] <Preparation of two-component developer> First, a two-component developer to be used for each evaluation was prepared. 100 parts by mass of carrier and 8 parts by mass of toner (either toner (T-A1) to (T-A7) or (T-B1) to (T-B7) to be evaluated) were mixed for 30 minutes using a ball mill to obtain a two-component developer for evaluation.

[0095] The above carrier was prepared by the following method. 361.2 g of silicone resin solution ("KR-255" manufactured by Shin-Etsu Chemical Co., Ltd., solid content: 50% by mass), 9.0 g of barium titanate ("BT-01" manufactured by Sakai Chemical Industry Co., Ltd., number-average primary particle diameter: 102 nm), 5.4 g of carbon black ("Ketjenblack EC-300J" manufactured by Lion Specialty Chemicals Co., Ltd.), and 1444.8 g of toluene were mixed using a homomixer to obtain a coating solution. Using a fluidized bed coating device ("FD-MP-01 D" manufactured by Powrex Corporation), the coating solution was sprayed onto 5000 g of carrier cores while fluidizing them. In this way, carrier cores coated with the coating solution were obtained. The coating conditions were an inlet air temperature of 75°C and an inlet air volume of 0.3 m3. 3 The conditions were a rotor speed of 400 rpm and a flow rate of 1000 kJ / min. The carrier core was a manganese ferrite core (manufactured by DOWA IP Creation Co., Ltd., D 50 The carrier cores were coated with the coating solution and fired at 200°C for 1 hour in an electric furnace. In this way, a coating was formed on the surface of the carrier cores, and a carrier was obtained.

[0096] <Evaluation machine> The evaluation machine used for each evaluation was a multifunction printer (TASKalfa6054c manufactured by Kyocera Document Solutions, Inc.) The two-component developer prepared above was placed in the developing device of the evaluation machine, and replenishment toner (either of the toners (T-A1) to (T-A7) or (T-B1) to (T-B7) to be evaluated) was placed in the toner container of the evaluation machine.

[0097] <Transferability> An evaluation machine was used to print an image with a coverage rate of 5% on 10,000 sheets of paper in an environment with a temperature of 20°C and a humidity of 50%. The mass of the consumed toner and the mass of the recovered toner were then measured, and the transfer efficiency (unit: %) was calculated using the following formula. The consumed toner is the toner that was discharged from the toner container out of the toner set in the toner container. The recovered toner is the toner that was not transferred to the printing paper out of the consumed toner. From the calculated transfer efficiency, the transferability was evaluated according to the following criteria. Transfer efficiency = 100 x (mass of consumed toner - mass of recovered toner) / (mass of consumed toner)

[0098] (Transferability criteria) A (good): Transfer efficiency is 90% or more. B (poor): Transfer efficiency is less than 90%.

[0099] <Charging stability> Using an evaluation machine, an image with a 5% coverage was printed on 500 sheets of paper under an environment of 20°C and 50% RH. After printing the 500 sheets, the toner charge (initial charge A) was measured. Next, using the evaluation machine, an image with a 5% coverage was printed on 100,000 sheets of paper. After printing the 100,000 sheets, the toner charge (post-printing charge B) was measured. The charge difference was calculated using the formula "charge difference = initial charge A - post-printing charge B." The toner charge was measured using a Q / m meter (Trek Model 212HS-F) by suctioning only the toner from the two-component developer on the magnet roller of the developing device of the evaluation machine through a sieve (wire mesh). From the calculated charge difference, the charge stability was evaluated according to the following criteria.

[0100] (Charging stability standard) A (particularly good): The difference in charge amount is less than 4 μC / g. B (Good): The difference in charge amount is 4 μC / g or more and less than 8 μC / g. C (poor): The charge difference is 8 μC / g or more.

[0101] [Table 3]

[0102] In Table 3, the "amount" of the resin-containing particles indicates the amount of resin-containing particles added relative to 100.0 parts by mass of the toner base particles. "Parts" indicates parts by mass.

[0103] In toner (T-B1), the surfactant contained in the resin-containing particles (more specifically, the surfactant (S-3c) contained in resin-containing particles (RB-1)) was a cationic surfactant, not an anionic surfactant. The transfer efficiency of toner (T-B1) was evaluated as poor. This is thought to be because resin-containing particles containing a cationic surfactant exhibited stronger positive charging properties than those containing an anionic surfactant, increasing the electrostatic adhesion of the toner particles to the photosensitive drum.

[0104] In toner (T-B2), the surfactant contained in the resin-containing particles (more specifically, the surfactant (S-4n) contained in the resin-containing particles (RB-2)) was a nonionic surfactant, not an anionic surfactant. The transfer efficiency of toner (T-B2) was evaluated as poor. The reason for this is thought to be that resin-containing particles containing a nonionic surfactant exhibit a stronger positive charge than those containing an anionic surfactant, which increased the electrostatic adhesion of the toner particles to the photosensitive drum.

[0105] In toner (T-B3), the resin-containing particles (more specifically, resin-containing particles (RB-3)) were not surface-treated with a silane coupling agent. The transfer efficiency of toner (T-B3) was evaluated as poor. The reason for this is thought to be that the adhesion of the resin-containing particles to the photosensitive drum increased because the resin-containing particles were not surface-treated with a silane coupling agent.

[0106] In toner (T-B4), the number average primary particle diameter of the resin-containing particles (more specifically, resin-containing particles (RB-4)) was greater than 100 nm. The evaluation of the charging stability of toner (T-B4) was poor. The reason for this is thought to be that the resin-containing particles were easily detached from the toner base particles, and the detached resin-containing particles adhered to the carrier, causing carrier contamination.

[0107] In toner (T-B5), the number-average primary particle diameter of the resin-containing particles (more specifically, resin-containing particles (RB-5)) was less than 60 nm. The evaluation of the transfer efficiency and the evaluation of the charging stability of toner (T-B5) were both poor. The reason for this is thought to be that, because the number-average primary particle diameter was less than 60 nm, the resin-containing particles did not function sufficiently as spacers to reduce the frequency of contact between the photosensitive drum and the toner base particles.

[0108] For toner (T-B6), the specified coverage was over 30%. The evaluation of the charging stability of toner (T-B6) was poor. The reason for this is thought to be that the resin-containing particles were easily detached from the toner base particles, and the detached resin-containing particles adhered to the carrier, causing carrier contamination.

[0109] For toner (T-B7), the specified coverage was less than 15%. The transfer efficiency of toner (T-B7) was evaluated as poor. The reason for this is thought to be that the toner base particles were not sufficiently covered with the resin-containing particles, and the resin-containing particles did not function sufficiently as spacers to reduce the frequency of contact between the photosensitive drum and the toner base particles.

[0110] On the other hand, in toners (T-A1) to (T-A7), the external additive contained resin-containing particles. The resin-containing particles further contained an anionic surfactant (more specifically, either surfactant (S-1a) or (S-2a)). The resin-containing particles were surface-treated with a silane coupling agent (more specifically, either surface treatment agent (IBTMS) or (PTMS)). The number-average primary particle diameter of the resin-containing particles was 60 nm or more and 100 nm or less. The predetermined coverage was 15% or more and 30% or less. The transfer efficiency of toners (T-A1) to (T-A7) was evaluated as good, and the charging stability was evaluated as good or particularly good.

[0111] The above results demonstrate that the toners according to the present invention, including the toners (T-A1) to (T-A7), have high transfer efficiency and excellent charge stability. [Industrial Applicability]

[0112] The toner according to the present invention can be used to form images in, for example, a multifunction machine or a printer.

Claims

1. 1. A positively charged toner comprising toner particles, The toner particles include toner base particles and an external additive attached to the surface of the toner base particles, The external additive includes resin-containing particles containing a resin, The resin-containing particles further contain an anionic surfactant, the resin-containing particles are surface-treated with a silane coupling agent; the number average primary particle diameter of the resin-containing particles is 60 nm or more and 100 nm or less; A positively charged toner, wherein the area ratio of the area covered with the resin-containing particles to the surface area of ​​the toner base particle is 15% or more and 30% or less.

2. 2. The positively charged toner according to claim 1, wherein the anionic surfactant has a sulfate anion group or a sulfonate anion group.

3. 3. The positively charged toner according to claim 1, wherein the anionic surfactant is present in the vicinity of the surface of the resin-containing particle.

4. 3. The positively charged toner according to claim 1, wherein the resin is a styrene-acrylic resin containing a silane bond.

5. 3. The positively charged toner according to claim 1, wherein the resin is a polymer of styrene or a derivative thereof, (meth)acrylic acid or a derivative thereof, a silane compound having at least one (meth)acryloxy group, and a crosslinking agent having at least two unsaturated bonds.

6. 3. The positively chargeable toner according to claim 1, wherein the content of the resin-containing particles is 0.7 parts by mass or more and 1.3 parts by mass or less with respect to 100.0 parts by mass of the toner base particles.

Images