JP2017129715A - Electrostatic latent image developing toner and external additive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner capable of preventing occurrence of image defect due to reduction of charge amount on a toner under high temperature and high humidity environment and/or due to reduction in mobility of the toner.SOLUTION: The electrostatic latent image developing toner contains plural kinds of toner particles. The toner particle includes toner base particles and particles plural kinds of external additives on the surface of toner base particles. The external additive particles are particles of hydrophobic nigrosine in which number average surface area equivalent diameter of 1.00 μm or less, and number average circularity is 0.940 or more.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic latent image developing toner and an external additive.

  The electrostatic latent image developing toner includes a plurality of toner particles. The toner base particles included in the toner particles contain, for example, a binder resin. Further, in order to charge the toner to a desired value, the toner base particles may contain a charge control agent such as a nigrosine compound. For example, the positively charged toner described in Patent Document 1 contains a binder resin containing a polyester resin, a colorant, and a nigrosine dye.

JP 2001-265061 A

  However, in the positively charged toner described in Patent Document 1, a nigrosine dye is contained in the toner base particles (internally added). When the nigrosine dye is internally added, the nigrosine dye may be compatible with the polyester resin as the binder resin. As a result, the ability of the nigrosine dye to charge the toner to a desired value (charge control ability) may be reduced. As a result, with the toner of Patent Document 1, an image defect may occur due to a decrease in the charge amount of the toner. In addition, with the toner of Patent Document 1, it is difficult to suppress the occurrence of image defects due to a decrease in fluidity.

  The present invention has been made in view of the above problems, and its object is to prevent image defects due to a decrease in the charge amount of toner in a high temperature and high humidity environment and image defects due to a decrease in toner fluidity. To provide a toner for developing an electrostatic latent image that can be suppressed. Another object of the present invention is to provide an external additive capable of providing such a toner for developing an electrostatic latent image.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles. The toner particles include toner base particles and a plurality of external additive particles provided on the surface of the toner base particles. The external additive particles are hydrophobized nigrosine particles having a number average area equivalent circle diameter of 1.00 μm or less and a number average circularity of 0.940 or more.

  The external additive according to the present invention includes a plurality of external additive particles. The external additive particles are hydrophobized nigrosine particles having a number average area equivalent circle diameter of 1.00 μm or less and a number average circularity of 0.940 or more. The surface of the hydrophobized nigrosine particle has a coating layer containing a disilylamine compound or a silicone compound.

  According to the toner for developing an electrostatic latent image of the present invention, it is possible to suppress the occurrence of an image defect due to a decrease in the charge amount of the toner in a high temperature and high humidity environment and the occurrence of an image defect due to a decrease in toner fluidity. . In addition, according to the external additive of the present invention, electrostatic latent image development that can suppress the occurrence of image defects due to a decrease in toner charge amount in a high temperature and high humidity environment and the occurrence of image defects due to a decrease in toner fluidity. Toner can be provided.

  Hereinafter, embodiments of the present invention will be described. Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. In addition, when “polymer” is added after the compound name to indicate the polymer name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof.

Hereinafter, the average value means a number average value unless otherwise specified. In addition, an evaluation value (a value indicating a shape or physical property) relating to powder (for example, electrostatic latent image developing toner, toner particles, toner base particles, and external additive, which will be described later) is not specified. Mean value. The number average value is a value obtained by dividing the sum of the values measured for a considerable number of measurement objects by the number of measurements. Further, the particle diameter of the powder is the equivalent-circle diameter of primary particles measured by an electron microscope unless otherwise specified. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particles. The volume median diameter D ₅₀ is a median diameter calculated on a volume basis using a Coulter counter method.

  The present embodiment relates to an electrostatic latent image developing toner (hereinafter sometimes referred to as toner). The toner of the present embodiment includes a plurality of toner particles. The toner is an aggregate of a plurality of toner particles (powder). The toner particles include toner base particles and a plurality of external additive particles. The external additive particles are provided on the surface of the toner base particles. The toner may be used as a one-component developer. Alternatively, the toner and the desired carrier may be mixed and used in the two-component developer.

  The toner of the present embodiment can suppress the occurrence of image defects due to a decrease in toner charge amount in a high temperature and high humidity environment and the occurrence of image defects due to a decrease in toner fluidity. The reason is presumed as follows.

  First, in the toner of the present embodiment, hydrophobic nigrosine particles are provided (externally added) on the surface of the toner base particles as external additive particles. By externally adding the hydrophobic nigrosine particles to the toner base particles, it becomes difficult for the binder resin contained in the toner base particles and the hydrophobic nigrosine particles to be compatible. Thereby, it can suppress that the capability (charge control capability) which the hydrophobic nigrosine particle charges a toner to a desired value falls. As a result, the toner is easily charged to a desired value.

  Secondly, in the toner of this embodiment, the nigrosine particles are hydrophobized. Usually, a nigrosine compound that forms nigrosine particles tends to have high hygroscopicity. Therefore, when the nigrosine particles are externally added to the toner base particles, the charge control ability of the nigrosine particles may be deteriorated particularly in a high temperature and high humidity environment. However, since the nigrosine particles of the present embodiment are hydrophobized, the charge control ability of the nigrosine particles is unlikely to deteriorate even under a high temperature and high humidity environment. As a result, even in a high temperature and high humidity environment, the toner charge amount is unlikely to decrease, and image defects (for example, a decrease in image density) in the formed image can be suppressed.

  Third, in the toner of this embodiment, the number average circularity of the hydrophobized nigrosine particles as the external additive particles is 0.940 or more. Usually, nigrosine particles have an irregular shape, and therefore, when the nigrosine particles are externally added, the fluidity of the toner tends to be lowered. However, in the toner of the present embodiment, the number average circularity of the hydrophobized nigrosine particles is 0.940 or more, so that the fluidity of the toner tends to be improved. When toner fluidity is improved, for example, when an image is formed using an image forming apparatus equipped with a developing roller using toner as a magnetic one-component developer, a thin layer of toner is uniformly formed on the developing roller. It becomes easy. When a thin toner layer is uniformly formed on the developing roller, streaks (striated portions where no toner is attached) are less likely to occur on the developing roller. This makes it difficult for image defects such as white streaks to occur in the formed image (for example, a halftone image). As a result, it is possible to suppress the occurrence of image defects due to a decrease in toner fluidity.

  Fourth, in the toner of the present exemplary embodiment, the number average area equivalent circle diameter of the hydrophobized nigrosine particles as the external additive particles is 1.00 μm or less. When the number average area equivalent circle diameter of the hydrophobized nigrosine particles is 1.00 μm or less, the fluidity of the toner tends to be improved. As a result, as described above, it is possible to suppress the occurrence of image defects due to a decrease in toner fluidity.

<1. Toner mother particles>
Next, the toner base particles will be described. The toner base particles contain at least a binder resin. The toner base particles may contain one or more of a magnetic powder, a release agent, a black colorant, and a charge control agent as necessary. However, unnecessary components (for example, magnetic powder, release agent, black colorant, or charge control agent) may be omitted depending on the use of the toner.

  The toner base particles may be encapsulated. The encapsulated toner base particles have, for example, a toner core having the same structure and components as those of the toner base particles described below, and a shell layer (capsule layer) formed on the surface of the toner core.

The volume median diameter D ₅₀ of the toner base particles is preferably 5 μm or more and 10 μm or less.

<1-1. Binder resin>
The binder resin is not particularly limited as long as it is a binder resin used for toner preparation. As the binder resin, a thermoplastic resin is preferable from the viewpoint of improving the fixability of the toner. Preferable examples of thermoplastic resins include styrene resins, acrylic resins, styrene acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, urethane resins, polyvinyl alcohol resins, vinyl ether resins. N-vinyl compound resin or styrene butadiene resin.

  When a thermoplastic resin is used as the binder resin, one type of thermoplastic resin may be used alone, or two or more types may be used in combination. Moreover, you may add a crosslinking agent or a thermosetting resin to a thermoplastic resin. By partially introducing a cross-linked structure into the binder resin, it becomes easy to improve the storage stability, form retention and durability of the toner while ensuring the toner fixability.

  In order to improve the dispersibility of the colorant in the binder resin and the low-temperature fixability of the toner, the toner base particles preferably contain a polyester resin as the binder resin. Polyester resins are easily negatively charged. Therefore, when developing using positively charged toner, nigrosine particles may be internally added to the toner base particles for the purpose of charging the toner to a desired value. When the nigrosine particles are internally added, the polyester resin and the nigrosine particles are compatible with each other, the charge control ability of the nigrosine particles is lowered, and the toner may not be charged to a desired value. However, in the toner of this embodiment, hydrophobic nigrosine particles are provided on the surface of the toner base particles (externally added). Therefore, even when a polyester resin is used as the binder resin, the hydrophobized nigrosine particles are hardly compatible with the polyester resin. As a result, even when the toner base particles contain a polyester resin as a binder resin, it is possible to suppress a decrease in charge control ability of the hydrophobized nigrosine particles and to easily charge the toner to a desired value.

  The polyester resin can be obtained by, for example, condensation polymerization or co-condensation polymerization of alcohol and carboxylic acid.

  Preferable examples of the alcohol used for preparing the polyester resin include diols, bisphenols, and trivalent or higher alcohols.

  Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1, Examples include 5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

  Examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct.

  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 or 1,3,5-trihydroxymethyl Benzene is mentioned.

  Examples of the carboxylic acid used when synthesizing the polyester resin include a divalent carboxylic acid or a trivalent or higher carboxylic acid.

  Examples of divalent carboxylic 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, succinic acid. Examples include acids, alkyl succinic acids or alkenyl succinic acids. Examples of alkyl succinic acids include n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid or isododecyl succinic acid. Examples of alkenyl succinic acids include n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid or isododecenyl succinic acid.

  Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, Examples include 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid or emporic trimer acid.

  Alcohol and carboxylic acid may be used individually by 1 type, respectively, and may be used in combination of 2 or more type. Furthermore, the carboxylic acid may be derivatized into an ester-forming derivative. Examples of ester-forming derivatives include acid halides, acid anhydrides or lower alkyl esters. Here, the lower alkyl means an alkyl group having 1 to 6 carbon atoms.

  The acid value of the polyester resin is preferably 5 mgKOH / g or more and 30 mgKOH / g or less. The hydroxyl value of the polyester resin is preferably 15 mgKOH / g or more and 80 mgKOH / g or less. The acid value and hydroxyl value of the polyester resin are measured, for example, according to a method defined in JIS (Japanese Industrial Standard) K0070-1992 or a method based thereon.

  The acid value and hydroxyl value of the polyester resin are adjusted, for example, by appropriately changing the amount of alcohol used and the amount of carboxylic acid used in producing the polyester resin. Moreover, when the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  The softening point of the binder resin is preferably 80 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower.

  The glass transition point of the binder resin is preferably 30 ° C. or higher and 60 ° C. or lower. When the glass transition point of the binder resin is within such a range, it is easy to improve the storage stability, shape retention, and durability of the toner while maintaining high toner fixability.

<1-2. Magnetic powder>
The magnetic powder is not particularly limited as long as it can be used for toner. Examples of magnetic powders include ferromagnetic metals, alloys of multiple types of ferromagnetic metals, magnetic powders based on ferromagnetic metals, magnetic powders doped with cobalt or nickel in iron oxide, and no ferromagnetic metal elements An alloy or chromium dioxide which becomes ferromagnetic by heat treatment. Examples of ferromagnetic metals include iron, cobalt or nickel. Iron may be used in the form of iron oxide (eg, magnetite or ferrite). These magnetic powders may be used alone or in combination of two or more. Magnetite is preferred as the magnetic powder because the charge amount of the toner particles can be easily adjusted.

  The number average primary particle diameter of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less. When magnetic powder having a number average primary particle size in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

<1-3. Release agent>
The release agent is used, for example, for the purpose of improving the toner fixing property and offset resistance. In order to improve the fixing property and offset resistance of the toner, the amount of the release agent used 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. More preferably, it is at least 15 parts by mass.

  Examples of release agents include aliphatic hydrocarbon waxes, aliphatic hydrocarbon wax oxides, plant-derived waxes, animal-derived waxes, mineral-derived waxes, waxes based on fatty acid esters or fatty acid esters. A wax partially or completely deoxidized is mentioned. Examples of aliphatic hydrocarbon waxes include ester wax, polyethylene wax (eg low molecular weight polyethylene), polypropylene wax (eg low molecular weight polypropylene), polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax or Fischer-Tropsch A wax is mentioned. Examples of the oxide of the aliphatic hydrocarbon wax include an oxidized polyethylene wax or a block copolymer of oxidized polyethylene. Examples of plant-derived waxes include candelilla wax, carnauba wax, wood wax, jojoba wax or rice wax. Examples of animal-derived waxes include beeswax, lanolin or spermaceti. Examples of mineral-derived waxes include ozokerite, ceresin or petrolatum. Examples of the wax mainly composed of a fatty acid ester include montanic acid ester wax and caster wax. Deoxidized carnauba wax is an example of a wax in which a part or all of the fatty acid ester has been deoxidized. One of these release agents may be used alone, or two or more thereof may be used in combination.

<1-4. Other ingredients>
The toner base particles may contain a black colorant. Examples of the black colorant include black pigments or black dyes. Specific examples of the black pigment include carbon black. A black colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant described below may be used.

  In addition to the hydrophobized nigrosine particles externally added to the toner base particles, the toner base particles may further contain a charge control agent (may be added internally).

  Examples of charge control agents include azine compounds, direct dyes composed of azine compounds, nigrosine compounds, acidic dyes composed of nigrosine compounds, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines or alkylamides.

<2. External additive (hydrophobized nigrosine)>
The external additive includes a plurality of external additive particles. The external additive particles are hydrophobized nigrosine particles. The external additive is an aggregate of a plurality of hydrophobized nigrosine particles (powder). The hydrophobized nigrosine particles function as, for example, a positively chargeable charge control agent in the toner. For this reason, when an image is formed using the toner of this embodiment, it is preferable to develop the toner by positively charging the toner (as a positively chargeable toner).

  In the toner of this embodiment, a plurality of hydrophobic nigrosine particles, which are external additive particles, are provided on the surface of the toner base particles. By providing the hydrophobic nigrosine particles on the surface of the toner base particles (externally added), as described above, it is possible to suppress the charge control ability of the hydrophobic nigrosine particles from being lowered. As a result, the toner is easily charged to a desired value.

  The hydrophobized nigrosine particles are produced, for example, by hydrophobizing the surface of the nigrosine core using a surface treatment agent. For example, hydrophobic nigrosine particles are produced by coating a nigrosine core with a surface treatment agent. Since the nigrosine particles are hydrophobized, as described above, the charge control ability of the nigrosine particles is hardly lowered even in a high temperature and high humidity environment. For this reason, even in a high-temperature and high-humidity environment, the toner charge amount hardly decreases, and image defects (for example, a decrease in image density) in the formed image can be suppressed.

  When the surface of the nigrosine core is hydrophobized using a surface treatment agent, the surface of the resulting hydrophobized nigrosine particle has a coating layer containing the surface treatment agent. For example, a nigrosine core is coated with a surface treatment agent. The coating layer containing the surface treatment agent may be provided on at least a part of the surface of the hydrophobized nigrosine particle. In order to improve the image density of an image formed in a high-temperature and high-humidity environment, it is preferable that a coating layer containing a surface treatment agent is provided on substantially the entire surface of the hydrophobized nigrosine particles.

  The hydrophobized nigrosine particle has, for example, a nigrosine core and a coating layer. The coating layer is provided to cover the nigrosine core. The nigrosine core is formed from a nigrosine compound, for example. The coating layer contains, for example, a surface treatment agent. The coating layer is preferably hydrophobic.

  Examples of nigrosine compounds that form a nigrosine core include nigrosine, nigrosine salts, nigrosine derivatives, or acidic dyes containing one or more of these. Examples of the acid dye include nigrosine BK, nigrosine NB or nigrosine Z.

  The nigrosine compound is produced, for example, by condensing an aniline compound (for example, aniline or aniline hydrochloride) and a nitrobenzene compound (for example, nitrobenzene, nitrophenol, or nitrocresol). The condensation may be performed, for example, in the presence of a mixture of hydrochloric acid and iron, a mixture of hydrochloric acid and iron chloride, or iron chloride. The condensation may be performed under heating.

  Examples of the surface treatment agent contained in the coating layer include a disilylamine compound, a halogenated silane compound, a silicone compound, or a silane coupling agent.

  The disilylamine compound is a compound having a disilylamine (Si—N—Si) moiety. Examples of disilylamine compounds include hexamethyldisilazane (HMDS), N-methyl-hexamethyldisilazane or hexamethyl-N-propyldisilazane. An example of the halogenated silane compound is dimethyldichlorosilane.

  Examples of the silicone compound include silicone oil or silicone resin (varnish). Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil or fluorine modified silicone oil. Examples of the silicone resin (varnish) include methyl silicone varnish and phenylmethyl silicone varnish.

  Examples of the silane coupling agent include a silane coupling agent having an alkyl group and an alkoxy group, or a silane coupling agent having an amino group and an alkoxy group. More specific examples of the silane coupling agent include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, trimethylmethoxysilane, trimethyldiethoxysilane, triethylmethoxysilane, triethyldiethoxysilane, and γ-glycol. Sidoxypropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyldimethoxymethylsilane or γ-aminopropyldiethoxymethylsilane It is done.

  The above-mentioned surface treatment agents may be used alone or in combination of two or more. In order to improve the image density of an image formed in a high-temperature and high-humidity environment and suppress the occurrence of white streaks in the formed image, it is preferable to use a disilylamine compound or a silicone compound as a surface treatment agent, More preferably, hexamethyldisilazane or silicone oil is used.

  In order to improve the image density of an image formed in a normal temperature and humidity environment, in addition to improving the image density formed in a high temperature and high humidity environment and suppressing the occurrence of white streaks in the formed image, the surface As the treating agent, it is preferable to use a disilylamine compound, and it is more preferable to use hexamethyldisilazane.

  In order to particularly improve the image density of an image formed in a high-temperature and high-humidity environment, it is preferable to use a silicone compound as the surface treatment agent, and it is more preferable to use silicone oil.

  The surface treatment agent contained in the coating layer may be chemically bonded to the nigrosine compound contained in the nigrosine core. For example, when the nigrosine compound has a hydroxyl group and hexamethyldisilazane is used as the surface treatment agent, the hydroxyl group may be silylated to form a trimethylsilyloxy group.

  The content of the surface treatment agent in the coating layer is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass with respect to the mass of the coating layer. .

  The content of the surface treatment agent in the hydrophobized nigrosine particles is preferably larger than 0 parts by mass and 20 parts by mass or less, preferably from 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the nigrosine core. More preferred.

  The number average area equivalent circle diameter of the hydrophobized nigrosine particles is 1.00 μm or less. If the number average area equivalent circle diameter of the hydrophobized nigrosine particles is 1.00 μm or less, as described above, it is possible to suppress the occurrence of image defects (for example, the occurrence of white streaks) due to a decrease in toner fluidity. it can. The number average area equivalent circle diameter of the hydrophobized nigrosine particles is preferably from 0.50 μm to 1.00 μm.

  The number average circularity of the hydrophobized nigrosine particles is 0.940 or more. When the number average circularity of the hydrophobized nigrosine particles is 0.940 or more, as described above, it is possible to suppress the occurrence of image defects (for example, the generation of white streaks) due to a decrease in toner fluidity. The number average circularity of the hydrophobized nigrosine particles is preferably 0.940 or more and 0.975 or less. In order to further improve the image density of an image formed in a high temperature and high humidity environment, the number average circularity of the hydrophobized nigrosine particles is more preferably 0.950 or more and 0.975 or less.

  When a disilylamine compound (preferably hexamethyldisilazane) is used as the surface treatment agent, the number average circularity of the hydrophobized nigrosine particles is preferably 0.950 or more. When the number average circularity of the hydrophobized nigrosine particles is within such a range, the image density of each image formed in a normal temperature and normal humidity environment and a high temperature and high humidity environment is improved, and white streaks in the formed image are improved. It becomes easy to achieve both suppression of generation.

  The number average area equivalent circle diameter and the number average circularity of the hydrophobized nigrosine particles are measured, for example, by the following method. The number of hydrophobized nigrosine particles in the suspension, the equivalent area circle diameter, and the circularity are measured using a flow particle image analyzer. The sum of the area equivalent circle diameters of the measured hydrophobized nigrosine particles is divided by the number of the measured hydrophobized nigrosine particles. Thereby, the number average area equivalent circle diameter of the hydrophobized nigrosine particles is calculated. Further, the sum of the circularity of the measured hydrophobized nigrosine particles is divided by the number of the measured hydrophobized nigrosine particles. Thereby, the number average circularity of the hydrophobized nigrosine particles is calculated. Details of the measurement method will be described later in Examples. The number average area equivalent circle diameter and number average circularity of the hydrophobized nigrosine particles tend to coincide with the number average area equivalent circle diameter and number average circularity of the nigrosine core before hydrophobization.

  The content of the hydrophobized nigrosine particles is preferably more than 0 parts by mass and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner base particles. More preferably, it is 0.5 parts by mass or more and 2 parts by mass or less. When the content of the hydrophobized nigrosine particles is within such a range, the toner is easily charged to a desired value. In the toner of this embodiment, a plurality of hydrophobic nigrosine particles are provided on the surface of the toner base particles. Therefore, compared to the case where the hydrophobic nigrosine particles are contained (added internally) in the toner base particles, the toner tends to be charged to a desired value with a small amount of the hydrophobic nigrosine content.

  The surface of the toner base particles may be provided with an external additive (other external additives) other than the hydrophobized nigrosine particles, if necessary, in addition to the hydrophobized nigrosine particles. Other external additives are used, for example, for the purpose of improving the fluidity of the toner or for the purpose of easily polishing the photosensitive member with the toner.

  Examples of other external additives include silica or metal oxide. Specific examples of the metal oxide include alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. Other external additives may be used alone or in combination of two or more.

  The number average particle size of the other external additives is preferably 1 nm or more and 1 μm or less, and more preferably 1 nm or more and 50 nm or less. The amount of other external additives used is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of toner base particles.

<3. Method for producing hydrophobized nigrosine particles>
The method for producing hydrophobized nigrosine particles includes, for example, a nigrosine core forming step and a hydrophobizing step. The method for producing hydrophobized nigrosine particles may be carried out with appropriate modifications as necessary.

<3-1. Nigrosine core formation process>
Examples of the method for forming the nigrosine core include a pulverization method and a spray drying method.

(Crushing method)
Hereinafter, an example (pulverization method) of the nigrosine core forming step will be described. The pulverization method has an advantage that a nigrosine core having a desired number average circularity and a number average area equivalent circle diameter can be easily manufactured by adjusting the pulverization conditions. An example of the nigrosine core forming step includes a pulverization step and a pulverized material classification step.

  In the pulverization step, the nigrosine raw material is pulverized to obtain a pulverized nigrosine product. The pulverization is performed using, for example, a pulverizer. The number of pulverizations is preferably 1 or more and 10 or less, more preferably 2 or more and 4 or less. As the number of pulverization increases, the number average area equivalent circle diameter of the nigrosine core and thus the hydrophobized nigrosine particles decreases, and the number average circularity tends to increase. The rotation speed of the pulverizer is preferably 3000 rpm or more and 11000 rpm or less. When the rotational speed of the pulverizer is within such a range, the number average area equivalent circle diameter of the nigrosine core and thus the hydrophobized nigrosine particles can be easily adjusted to a desired value. As the rotational speed increases, the number average area equivalent circle diameter of the nigrosine core and thus the hydrophobized nigrosine particles tends to decrease.

  In the pulverized product classification step, the nigrosine pulverized product is classified to obtain a nigrosine core. In classification, for example, a classifier is used.

(Spray drying method)
Hereinafter, another example (spray drying method) of the nigrosine core forming step will be described. The spray-drying method has an advantage that it is easy to produce a nigrosine core having a high number average circularity and thus a hydrophobized nigrosine particle. Another example of the nigrosine core forming step includes a spray drying step and a granulated product classification step.

  In the spray drying step, a nigrosine granulated product is obtained by dissolving the nigrosine raw material in a solvent and spray drying the obtained solution. The addition amount of the nigrosine raw material is preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the solvent. The solvent used in the spray drying process is not particularly limited as long as the nigrosine raw material can be dissolved. Examples of solvents include ethers (eg tetrahydrofuran, dimethyl ether, diethyl ether, ethylene glycol dimethyl ether or diethylene glycol dimethyl ether), alcohols (eg methanol, ethanol, isopropanol or butanol), ketones (eg acetone, methyl ethyl ketone or cyclohexanone). ) Or aromatic hydrocarbons (eg, benzene, toluene or xylene). In the spray drying process, for example, a spray dryer is used. The spray drying temperature is preferably 20 ° C. or higher and 80 ° C. or lower. The solution is preferably sprayed while passing through the mesh. The pore diameter of the mesh is preferably 0.5 μm or more and 3.0 μm or less. The solution is sprayed, for example, by vibrating with ultrasonic waves. The vibration frequency of the ultrasonic wave at that time is preferably 10 kHz or more and 80 kHz or less.

  In the granulated product classification step, the nigrosine granulated product is classified to obtain a nigrosine core. In classification, for example, a classifier is used.

<3-2. Hydrophobization process>
In the hydrophobizing step, the surface of the nigrosine core is hydrophobized with a surface treatment agent. An example of the hydrophobizing method includes a method of mixing (for example, stirring) the nigrosine core and the surface treatment agent. In mixing, for example, a mixer (for example, an FM mixer manufactured by Nippon Coke Industries, Ltd. or a Nauter mixer (registered trademark) manufactured by Hosokawa Micron Corporation) is used. Another example of the hydrophobization method includes a method of spray-drying a surface treatment agent on the nigrosine core. In spray drying, for example, a spray dryer is used. According to the hydrophobizing step as described above, the surface of the nigrosine core can be easily and efficiently hydrophobized even when a polymerization reaction or the like is not performed.

<4. Toner Production Method>
For example, the toner is manufactured by the following method. The toner manufacturing method may be arbitrarily changed according to the required configuration or characteristics of the toner. Further, unnecessary operations may be omitted. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously.

<4-1. Step of forming toner base particles>
Examples of the method for producing toner base particles include an agglomeration method or a pulverization method. The aggregation method makes it easier to produce toner mother particles having a higher number average circularity than the pulverization method. Further, the aggregation method is easy to produce toner base particles having a uniform shape and particle size. On the other hand, the pulverization method can produce toner base particles more easily than the aggregation method.

(Crushing method)
Hereinafter, an example of the pulverization method will be described. First, the binder resin and components contained as necessary (for example, magnetic powder, release agent, black colorant, and charge control agent) are melted and kneaded. Subsequently, the obtained melt-kneaded product is pulverized to obtain a pulverized product. The obtained pulverized product is classified to obtain toner base particles (for example, toner base particles having a desired volume median diameter D ₅₀ ).

(Aggregation method)
Next, an example of the aggregation method will be described. First, a dispersion of fine particles of each component is obtained for the binder resin and components contained as necessary (for example, magnetic powder, release agent, black colorant, and charge control agent). The obtained dispersion liquid of fine particles of each component is added to an aqueous medium. The fine particles of each component are aggregated in an aqueous medium to obtain aggregated particles of a plurality of components. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. Thereby, toner mother particles are obtained.

<4-2. External process>
In the external addition step, a plurality of hydrophobized nigrosine particles are attached to the surface of the toner base particles (external addition). Thereby, toner particles are obtained. In the external addition step, an external additive other than the hydrophobized nigrosine particles may be attached to the surface of the toner base particles as necessary. As a suitable example of the external addition method, toner base particles and hydrophobicized nigrosine particles are prepared using a mixer (for example, FM mixer manufactured by Nippon Coke Industries, Ltd. or Nauter Mixer (registered trademark) manufactured by Hosokawa Micron Corporation). And a method of mixing them. The mixing condition of the mixer is preferably set to a condition in which at least a part of the hydrophobized nigrosine particles are buried in the toner base particles. When at least a part of the hydrophobic nigrosine particles are embedded in the toner base particles, the hydrophobic nigrosine particles are difficult to be detached from the toner base particles, and the charge amount of the toner is easily stabilized.

  Examples of the present invention will be described. However, the present invention is not limited to the following examples.

<1. Manufacture of polyester resin>
A polyester resin to be contained in the toner base particles was produced. Specifically, a four-necked flask with a capacity of 2 liters equipped with a thermometer, a stainless steel stirrer, a glass nitrogen inlet tube, and a falling condenser was prepared. In the flask, 54 mol equivalent of ethylene glycol, 40 mol equivalent of terephthalic acid and 6 mol equivalent of 1,2,4-benzenetricarboxylic anhydride were added as monomers. The flask was set on a mantle heater, and nitrogen gas was introduced from a glass nitrogen gas inlet tube. This replaced the air in the flask with an inert atmosphere (nitrogen atmosphere). Subsequently, the temperature inside the flask was increased to 220 ° C. in a nitrogen atmosphere. While maintaining the internal temperature of the flask at 220 ° C. under a nitrogen atmosphere, the flask contents were stirred to cause the flask contents to undergo a polymerization reaction. When the monomer decreased due to scattering or sublimation, an amount of monomer corresponding to the decreased amount was replenished in the flask. The reaction system (flask contents) was appropriately sampled, and the acid value of the flask contents was measured. When the acid value of the flask contents reached 10 mgKOH / g, the polymerization reaction was stopped. The reaction product in the flask was taken out into a vat and cooled to room temperature. As a result, a polyester resin was obtained.

<2. Production of nigrosine particles>
Nigrosine particles (aggregates of a plurality of nigrosine particles) A to G were produced. The number average area equivalent circle diameter and number average circularity of the nigrosine particles described later were measured by the following methods.

(Measurement method of number average area equivalent circle diameter and number average circularity)
A sample (for example, nigrosine particles) 0.1 g and a dispersion (sheath solution) 20 mL were mixed to obtain a suspension of nigrosine particles. The number of nigrosine particles contained in the obtained suspension, the area equivalent circle diameter of each nigrosine particle, and the circularity of each nigrosine particle were determined using a flow particle image analyzer (“FPIA (registered trademark)” manufactured by Sysmex Corporation). -3000 "). The sum of the area equivalent circle diameters of the measured nigrosine particles was divided by the number of measured nigrosine particles. Thereby, the number average area equivalent circle diameter of the nigrosine particles was calculated. Further, the sum of the circularity of the measured nigrosine particles was divided by the number of the measured nigrosine particles. Thereby, the number average circularity of the nigrosine particles was calculated. The number average area equivalent circle diameter and number average circularity of the hydrophobized nigrosine particles tend to coincide with the area equivalent circle diameter and number average circularity of the nigrosine core before hydrophobization. Therefore, in the following Examples and Comparative Examples, the number average area circle equivalent diameter and the number average circularity of the nigrosine core were measured and regarded as the number average area circle equivalent diameter and the number average circularity of the hydrophobized nigrosine particles.

<2-1. Production of Nigrosine Particle A>
(Nigrosine core formation process)
Nigrosine raw material ("BONTRON (registered trademark) N-71" manufactured by Orient Chemical Industry Co., Ltd., azine compound) is used with a mechanical crusher ("Turbomill T250" manufactured by Freund Turbo Co., Ltd.) at a rotational speed of 5000 rpm. The powder was pulverized twice to obtain a pulverized product. The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a nigrosine core. The number average area equivalent circle diameter of the nigrosine core was 0.98 μm, and the number average circularity was 0.942.

(Hydrophobicization process)
100 parts by mass of the obtained nigrosine core and 5 parts by mass of hexamethyldisilazane (HMDS, manufactured by Wako Pure Chemical Industries, Ltd.) were stirred using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.). . Thereby, the surface of the nigrosine core was hydrophobized. As a result, hydrophobized nigrosine particles A (an aggregate of a plurality of nigrosine particles A) were obtained.

<2-2. Production of Nigrosine Particle B>
(Nigrosine core formation process)
50 parts by mass of nigrosine raw material (“BONTRON (registered trademark) N-71” manufactured by Orient Chemical Co., Ltd., azine compound) was dissolved in 100 parts by mass of tetrahydrofuran. The obtained tetrahydrofuran solution of nigrosine was spray-dried using a spray dryer (“Nano Spray Dryer B-90” manufactured by Nihon Buch Co., Ltd.) to obtain a granulated product. The spray drying temperature was 40 ° C. The solution was sprayed as it passed through the mesh (pore size 3.0 μm). Further, the solution was sprayed by vibrating the solution with ultrasonic waves having a vibration frequency of 60 kHz. The obtained granulated product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a nigrosine core. The number average area equivalent circle diameter of the nigrosine core was 0.98 μm, and the number average circularity was 0.973.

(Hydrophobicization process)
The surface of the nigrosine core was hydrophobized in the same manner as in the step of hydrophobizing the nigrosine particle A. As a result, hydrophobized nigrosine particles B (an aggregate of a plurality of nigrosine particles B) were obtained.

<2-3. Production of Nigrosine Particle C>
(Nigrosine core formation process)
Nigrosine raw material ("BONTRON (registered trademark) N-71" manufactured by Orient Chemical Co., Ltd., azine compound) is used with a mechanical crusher ("Turbomill T250" manufactured by Freund Turbo Co., Ltd.) at a rotational speed of 8000 rpm. The powder was pulverized twice to obtain a pulverized product. The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a nigrosine core. The number average area equivalent circle diameter of the nigrosine core was 0.97 μm, and the number average circularity was 0.938.

(Hydrophobicization process)
The surface of the nigrosine core was hydrophobized in the same manner as in the step of hydrophobizing the nigrosine particle A. As a result, hydrophobized nigrosine particles C (an aggregate of a plurality of nigrosine particles C) were obtained.

<2-4. Production of Nigrosine Particle D>
(Nigrosine core formation process)
Nigrosine raw material ("BONTRON (registered trademark) N-71" manufactured by Orient Chemical Co., Ltd., azine compound) is used at a rotational speed of 4000 rpm with a mechanical crusher ("Turbomill T250" manufactured by Freund Turbo). The powder was pulverized twice to obtain a pulverized product. The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a nigrosine core. The number average area equivalent circle diameter of the nigrosine core was 1.20 μm, and the number average circularity was 0.941.

(Hydrophobicization process)
The surface of the nigrosine core was hydrophobized in the same manner as in the step of hydrophobizing the nigrosine particle A. As a result, hydrophobized nigrosine particles D (an assembly of a plurality of nigrosine particles D) were obtained.

<2-5. Production of Nigrosine Particle E>
A nigrosine core was obtained by the same method as the nigrosine core forming step of the nigrosine particle A. Thereafter, the hydrophobization step was not performed. The nigrosine core obtained in the nigrosine core formation step was used as nigrosine particle E (an aggregate of a plurality of nigrosine particles E).

<2-6. Production of Nigrosine Particle F>
(Nigrosine core formation process)
A nigrosine core was obtained by the same method as the nigrosine core forming step of the nigrosine particle A.

(Hydrophobicization process)
100 parts by mass of nigrosine core and 3 parts by mass of silicone oil (“KF-96” manufactured by Shin-Etsu Chemical Co., Ltd.) were stirred using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.). Thereby, the surface of the nigrosine core was hydrophobized. As a result, hydrophobized nigrosine particles F (an aggregate of a plurality of nigrosine particles F) were obtained.

<2-7. Production of Nigrosine Particle G>
(Nigrosine core formation process)
Nigrosine raw material ("BONTRON (registered trademark) N-71" manufactured by Orient Chemical Co., Ltd., azine compound) is pulverized four times using a mechanical pulverizer ("Turbomill T250" manufactured by Freund Turbo). I got a thing. The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a nigrosine core. The number average area equivalent circle diameter of the nigrosine core was 0.57 μm, and the number average circularity was 0.956.

(Hydrophobicization process)
The surface of the nigrosine core was hydrophobized in the same manner as in the step of hydrophobizing the nigrosine particle A. As a result, hydrophobized nigrosine particles G (an aggregate of a plurality of nigrosine particles G) were obtained.

<3. Production of toner>
Toners A1 to A4 and B1 to B4 were produced by the following method.

(Manufacture of toner A1)
52 parts by mass of a polyester resin, 45 parts by mass of magnetite (“TN-15” manufactured by Mitsui Mining & Smelting Co., Ltd.) as magnetic powder, and 3 parts by mass of carnauba wax (manufactured by Toa Kasei Co., Ltd.) as a release agent Nippon Coke Kogyo Co., Ltd. “FM-20B”) was mixed for 5 minutes under the condition of a rotational speed of 2000 rpm. The obtained mixture was melted using a twin screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) under the conditions of a melt kneading temperature (cylinder temperature) of 100 ° C, a rotation speed of 150 rpm, and a processing speed of 100 g / min. Kneaded. The obtained melt-kneaded product was coarsely pulverized using a pulverizer ("Rotoplex (registered trademark) Ro type" manufactured by Hosokawa Micron Corporation) until the major axis diameter was about 2 mm. The coarsely pulverized product was further pulverized using a mechanical pulverizer (“Turbo Mill T250” manufactured by Freund Turbo, Inc.). The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner mother particles were obtained. The obtained toner base particles had a volume median diameter D ₅₀ of 8 μm. The volume median diameter D ₅₀ of the toner base particles was measured using a precision particle size distribution measuring device (“Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc.).

  100 parts by mass of the obtained toner base particles, 0.7 parts by mass of hydrophobic silica particles (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd.) as an external additive, and conductive oxidation as an external additive 0.8 parts by mass of titanium particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) and 1 part by mass of Nigrosine Particle A as an external additive were mixed with an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.). And mixed for 5 minutes under the condition of a rotational speed of 2000 rpm. As a result, three types of external additives were adhered to the surface of the toner base particles, and toner particles were obtained. As a result, toner A1, which is an aggregate of toner particles, was obtained.

(Production of toners A2 to A4 and B1 to B3)
Toners A2 to A4 and B1 to B3 were produced in the same manner as in the production of the toner A1, except that the following points were changed. The nigrosine particles A in the production of the toner A1 were changed to the types of nigrosine particles shown in Table 1.

(Production of Toner B4)
1 part by mass of Nigrosine particle A, 52 parts by mass of polyester resin, 45 parts by mass of magnetite (“TN-15” manufactured by Mitsui Mining & Smelting Co., Ltd.) as magnetic powder, and carnauba wax (manufactured by Toa Kasei Co., Ltd.) as a release agent 3 parts by mass was mixed for 5 minutes under the condition of a rotational speed of 2000 rpm using an FM mixer (“FM-20B” manufactured by Nippon Coke Kogyo Co., Ltd.). The obtained mixture was melt-kneaded, pulverized and classified in the same manner as in the production of the toner A1. As a result, toner mother particles were obtained.

  101 parts by weight of the obtained toner base particles, 0.7 parts by weight of hydrophobic silica particles (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd.) as an external additive, conductive oxidation as an external additive 0.8 parts by mass of titanium particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) are mixed for 5 minutes under the condition of a rotational speed of 2000 rpm using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries Co., Ltd.). did. As a result, two types of external additives were adhered to the surface of the toner base particles to obtain toner particles. As a result, toner B4, which is an aggregate of toner particles, was obtained.

<4. Evaluation>
For each of toners A1 to A4 and B1 to B4, the image density (ID) in an environment at a temperature of 23 ° C. and a humidity of 50% RH, the presence or absence of white stripes, and the environment of a temperature of 30 ° C. and a humidity of 80% RH The image density (ID) was evaluated. As an evaluation machine, “FS-4020DN” manufactured by Kyocera Document Solutions Co., Ltd. was used. First, the toner was put into the black toner container of the evaluation machine. Subsequently, an installation operation was performed, and the toner in the toner container was filled in the black color developing device.

<4-1. Evaluation of image density (23 ° C., 50% RH)>
The image density was evaluated in an environment of a temperature of 23 ° C. and a humidity of 50% RH. After the toner was filled in the black color developing device as described above, a solid image (2.5 cm long × 2.5 cm wide) was formed on the paper using the toner and the evaluation machine. The image density of the obtained image was measured using a white photometer (“TC-6DS / A” manufactured by Tokyo Denshoku Co., Ltd.). Table 1 shows the measured image density under the environment of a temperature of 23 ° C. and a humidity of 50% RH. The higher the image density in an environment of a temperature of 23 ° C. and a humidity of 50% RH, the better the image density of an image formed in a normal temperature and humidity environment.

<4-2. Presence or absence of white stripes>
The presence or absence of white stripes was confirmed in an environment with a temperature of 23 ° C. and a humidity of 50% RH. After the toner was filled in the black color developing device as described above, a halftone image (image density of 25%) was formed on the entire surface of the paper using the toner and the evaluator. The obtained image was observed with the naked eye to confirm the presence or absence of white stripes. The confirmation results are shown in Table 1. Note that when the toner fluidity decreases, image defects (white streaks) tend to occur.

<4-3. Evaluation of image density (30 ° C., 80% RH)>
After the toner was charged into the black color developing device as described above, the evaluator was left in an environment of a temperature of 30 ° C. and a humidity of 80% RH for 24 hours. Subsequently, a solid image (2.5 cm long × 2.5 cm wide) was formed on the paper using a toner and an evaluation machine under an environment of a temperature of 30 ° C. and a humidity of 80% RH. The image density of the obtained image was measured using a white photometer (“TC-6DS / A” manufactured by Tokyo Denshoku Co., Ltd.). Table 1 shows the measured image density in an environment of a temperature of 30 ° C. and a humidity of 80% RH. It shows that the image density of the image formed in a high-temperature, high-humidity environment is so favorable that the image density in the environment of temperature 30 degreeC and humidity 80% RH is high. Note that when the charge amount of the toner decreases in a high-temperature and high-humidity environment, an image defect (decrease in image density) tends to occur.

In Table 1, ID and HMDS indicate image density and hexamethyldisilazane, respectively. In Table 1, the diameter and the circularity indicate the number average area equivalent diameter and the number average circularity of the nigrosine particles, respectively. The external addition means that nigrosine particles are provided on the surface of the toner base particles. Internal addition means that the nigrosine particles are contained in the toner base particles.

  In the toners A1 to A4, the toner particles had toner mother particles and a plurality of hydrophobicized nigrosine particles provided (externally added) on the surface of the toner mother particles. The hydrophobized nigrosine particles had a number average area equivalent circle diameter of 1.00 μm or less and a number average circularity of 0.940 or more. Therefore, as apparent from Table 1, the toners A1 to A4 have a high image density in an environment of a temperature of 30 ° C. and a humidity of 80% RH, and an image density of an image formed in a high temperature and high humidity environment is excellent. It was. In addition, with toners A1 to A4, the occurrence of white streaks in the formed image was also suppressed.

  In toners A1, A2 and A4, a disilylamine compound (specifically hexamethyldisilazane) was used as a surface treatment agent in the nigrosine hydrophobization step. Therefore, as is apparent from Table 1, in the toners A1, A2 and A4, in addition to improving the image density of an image formed in a high temperature and high humidity environment and suppressing the occurrence of white streaks, The image density of the formed image was also excellent.

  In toners A2 and A4, a disilylamine compound (specifically, hexamethyldisilazane) was used as a surface treating agent in the nigrosine hydrophobization step. The number average circularity of the hydrophobized nigrosine particles was 0.950 or more. Therefore, as apparent from Table 1, with toners A2 and A4, the image density of an image formed under a high-temperature and high-humidity environment is improved, white streaking is suppressed, and the image formed under a normal-temperature and normal-humidity environment Improvement in image density was achieved in a well-balanced manner.

  In toner A3, a silicone compound (specifically, silicone oil) was used as a surface treatment agent in the nigrosine hydrophobization step. Therefore, as apparent from Table 1, the toner A3 was particularly excellent in the image density of an image formed in a high temperature and high humidity environment.

  In toner B1, the number average circularity of the hydrophobized nigrosine particles was less than 0.940. Therefore, as apparent from Table 1, with the toner B1, white streaks occurred in the formed image.

  In the toner B2, the number average area equivalent circle diameter of the hydrophobized nigrosine particles exceeded 1.00 μm. Therefore, as apparent from Table 1, with the toner B2, white streaks occurred in the formed image.

  In toner B3, the nigrosine particles were not hydrophobized. Therefore, as apparent from Table 1, with toner B3, the image density of the image formed in a high temperature and high humidity environment was inferior.

  In toner B4, hydrophobized nigrosine particles were internally added and were not provided on the surface of the toner base particles. Therefore, as apparent from Table 1, an image could not be formed using the toner B4. The reason is presumed that the hydrophobic nigrosine particles were compatible with the polyester resin contained in the toner base particles and the charge control ability of the hydrophobic nigrosine was lowered, and the toner B4 could not be charged to a desired value.

  From the above, according to the toner of the present invention, it is possible to suppress the occurrence of an image defect due to a decrease in the charge amount of the toner in a high temperature and high humidity environment and the occurrence of an image defect due to a decrease in toner fluidity. In addition, according to the external additive of the present invention, it is possible to provide a toner capable of suppressing the occurrence of an image defect due to a decrease in the charge amount of the toner in a high temperature and high humidity environment and the occurrence of an image defect due to a decrease in toner fluidity. Can do.

  The toner according to the present invention can be used for forming an image in, for example, an electrophotographic image forming apparatus. The external additive according to the present invention can be used, for example, for producing a toner.

Claims (8)

An electrostatic latent image developing toner comprising a plurality of toner particles,
The toner particles include toner base particles and a plurality of external additive particles provided on the surface of the toner base particles.
The toner for electrostatic latent image development, wherein the external additive particles are hydrophobic nigrosine particles having a number average area equivalent circle diameter of 1.00 μm or less and a number average circularity of 0.940 or more.   The electrostatic latent image developing toner according to claim 1, wherein the toner base particles contain a polyester resin.   The electrostatic latent image developing toner according to claim 1, wherein the surface of the hydrophobized nigrosine particle has a coating layer containing a surface treatment agent.   4. The electrostatic latent image developing toner according to claim 3, wherein the surface treatment agent is a disilylamine compound or a silicone compound.   The electrostatic latent image developing toner according to claim 3, wherein the surface treatment agent is a disilylamine compound. The surface treatment agent is a disilylamine compound,
6. The electrostatic latent image developing toner according to claim 3, wherein the number average circularity of the hydrophobized nigrosine particles is 0.950 or more.   The electrostatic latent image developing toner according to claim 3, wherein the surface treatment agent is a silicone compound. An external additive comprising a plurality of external additive particles,
The external additive particles are hydrophobic nigrosine particles having a number average area equivalent circle diameter of 1.00 μm or less and a number average circularity of 0.940 or more,
The surface of the hydrophobized nigrosine particle is an external additive having a coating layer containing a disilylamine compound or a silicone compound.