JP6439718B2 - Method for producing magnetic toner - Google Patents

Description

  The present invention relates to a magnetic toner and a method for producing the magnetic toner.

  Magnetic toners used in image forming apparatuses tend to require a certain level of magnetic retention. This is because the magnetic toner is transported to the developing region of the developing sleeve and the thin layer (toner thin film) is formed by the magnetic toner on the developing sleeve. The strength of magnetism is determined, for example, by the amount of magnetic powder added to the magnetic toner. When the amount of magnetic powder added increases, the offset resistance of the magnetic toner to the recording medium may decrease. Moreover, since magnetic powder has electrical conductivity, the amount of magnetic powder added tends to affect the charge amount of the magnetic toner. For this reason, the amount of magnetic powder added to the magnetic toner particles tends to be limited. Therefore, it is desired to improve the image quality while keeping the amount of magnetic powder added constant. For example, Patent Document 1 describes a magnetic toner having an average circularity of 0.950 or more.

JP 2006-78983 A

  However, the magnetic toner described in Patent Document 1 is insufficient in charging stability and offset resistance.

  The present invention has been made in view of the above problems, and an object thereof is to provide a toner having excellent charging stability and offset resistance. Another object of the present invention is to provide a method for producing a magnetic toner having excellent charging stability and offset resistance.

  The magnetic toner of the present invention contains a plurality of toner particles. The toner particles include a crystalline polyester resin as a binder resin, magnetic powder, and a crystallization inhibitor. The crystallization inhibitor is attached to the surface of the magnetic powder.

  The method for producing a magnetic toner of the present invention is a method for producing the above-described magnetic toner. The method for producing a magnetic toner of the present invention includes an adhesion step, a kneading step, and a pulverizing step. In the attaching step, the crystallization inhibitor is attached to the surface of the magnetic powder. In the kneading step, the magnetic powder to which the crystallization inhibitor is adhered and the binder resin are kneaded to obtain a kneaded product. In the pulverization step, the kneaded product is pulverized.

  According to the present invention, a magnetic toner having excellent charging stability and offset resistance can be provided. In addition, according to the present invention, a method for producing a magnetic toner having excellent charging stability and offset resistance can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, about the location where description overlaps, although description may be abbreviate | omitted suitably, the summary of invention is not limited.

<First Embodiment: Magnetic Toner>
The magnetic toner according to the first embodiment (hereinafter sometimes simply referred to as “toner”) is an electrostatic latent image developing toner. The toner according to the first embodiment is a powder composed of a large number of toner particles. The toner according to the first embodiment can be used in, for example, an electrophotographic apparatus (image forming apparatus).

  In an electrophotographic apparatus, an electrostatic latent image is developed using a developer containing toner. In the developing step, a charged toner is attached to the electrostatic latent image formed on the photoconductor to form a toner image. In the subsequent transfer process, the toner image on the photoconductor is transferred to a recording medium (for example, paper). Thereafter, the toner image is heated and pressurized to fix the toner image on the recording medium.

The toner according to the first embodiment has the following configuration (1).
Configuration (1): The toner particles include a crystalline polyester resin as a binder resin, magnetic powder, and a crystallization inhibitor. The crystallization inhibitor is attached to the surface of the magnetic powder.

  “Crystallinity” as shown in the “crystalline polyester resin” defined in the present invention indicates that there is a clear endothermic peak, not a stepwise endothermic change, in differential scanning calorimetry (DSC). Specifically, “crystallinity” means that the half-value width of the endothermic peak when measured at a heating rate of 10 ° C./min is 15 ° C. or less. On the other hand, a polyester resin in which the half-value width of the endothermic peak exceeds 15 ° C. or a polyester resin in which no clear endothermic peak is observed means non-crystalline (amorphous).

  In the present specification, the charging stability of the toner is a property of the toner that indicates the ease of maintaining the charging. The charging stability can be evaluated by the ratio of charged toner that is present after a certain period of time after charging. Details of a specific evaluation method will be described later in Examples. The offset resistance can be evaluated by a difference between a fixing temperature (maximum fixing temperature) in the image forming apparatus and a standard fixing temperature. A large difference indicates excellent offset resistance. Details of a specific evaluation method will be described later in Examples.

  The adhesion of the crystallization inhibitor to the surface of the magnetic powder can be confirmed using a transmission electron microscope (TEM, “JSM-6700F” manufactured by JEOL Ltd.). Details of the confirmation method will be described later in Examples.

  Configuration (1) is useful for improving the charging stability and offset resistance of the toner. In the toner having the configuration (1), the crystallization inhibitor is attached to the surface of the magnetic powder. For this reason, crystallization of the crystalline polyester resin tends to be suppressed on the surface of the magnetic powder. On the other hand, when the crystalline polyester resin is crystallized, the electric resistance is lowered. For this reason, by reducing the presence of the crystallized polyester resin on the surface of the magnetic powder, the release of charges from the magnetic powder tends to be efficiently suppressed. Therefore, the toner having the configuration (1) can suppress a decrease in charging stability. In the toner having the configuration (1), the crystallization inhibitor is attached to the surface of the magnetic powder. For this reason, when the toner in the fixing process of the image forming process is melted, the cohesive force of the toner tends not to decrease. Therefore, the toner having the configuration (1) can suppress a decrease in offset resistance. Therefore, the toner having the configuration (1) has excellent charging stability and offset resistance.

In order to further improve at least one of the charging stability and offset resistance of the toner, the toner has at least one of the following configurations (2), (3), and (4) in addition to the configuration (1). It is preferable to have one.
Configuration (2): The crystallization inhibitor includes nigrosine.
Configuration (3): The toner particles further include an amorphous polyester resin as a binder resin.
Configuration (4): The crystallization inhibitor is substantially not present in the binder resin.

  Configuration (2) is useful for improving the charging stability and offset resistance of the toner. In the toner having the configuration (2), the crystallization inhibitor contains nigrosine. Nigrosine tends to suppress crystallization of the crystalline polyester resin. For this reason, the toner having the configuration (2) can easily improve the charging stability and the offset resistance.

  The toner having the configuration (3) is useful for improving charging stability and offset resistance. The toner having the configuration (3) further includes an amorphous polyester resin as a binder resin. The amorphous polyester resin increases the fixing temperature range of the toner.

  In the configuration (4), “the crystallization inhibitor is substantially not present in the binder resin” means that in the toner according to the present invention, the crystallization inhibitor is dispersed in the toner particles in an isolated state. It means that it exists only in an aspect that is substantially attached to the surface of the magnetic powder.

  Configuration (4) is useful for improving charging stability and offset resistance. In the toner having the configuration (4), the crystallization inhibitor is not present in the binder resin. That is, the crystallization inhibitor is substantially present only on the surface of the magnetic powder. In the toner having the configuration (4), since the crystallization inhibitor is not dispersed in the binder resin, the cohesive force of the toner is hardly reduced when the toner is melted in the fixing step of the image forming step. For this reason, the toner having the configuration (4) can easily suppress a decrease in offset resistance. In addition, since the crystallization inhibitor exists only in a form that substantially adheres to the surface of the magnetic powder, it tends to suppress crystallization only in the vicinity of the magnetic powder. For this reason, it is easy to control the charging stability of the toner. Therefore, the toner having the configuration (4) can improve charging stability and offset resistance.

  The toner according to the first embodiment includes a plurality of toner particles having the configuration (1) (hereinafter sometimes referred to as toner particles according to the first embodiment). The toner having the toner particles of the first embodiment has excellent charging stability and offset resistance. The toner preferably has the toner particles of the first embodiment in a proportion of 80% by mass or more, more preferably has the toner particles of the first embodiment in a proportion of 90% by mass or more, and 100% by mass. It is further preferred to have the toner particles of the first embodiment in proportion.

  The toner particles may contain an optional component (for example, a charge control agent, a release agent, or an external additive) as necessary. For example, an external additive may be attached to the surface of the toner particles as necessary. Hereinafter, the toner particles before the external additive adheres may be referred to as toner mother particles. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. In addition, a compound and a derivative thereof may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Hereinafter, the binder resin, magnetic powder, crystallization inhibitor, and optional components will be described in order.

[1. Binder resin]
As already described, the toner particles contain a crystalline polyester resin as the binder resin. In addition, the toner particles may contain a binder resin other than the crystalline polyester resin (hereinafter, may be referred to as other binder resin). Hereinafter, the crystalline polyester resin and other binder resins will be described.

[1-1. Crystalline polyester resin]
The crystalline polyester resin is obtained, for example, by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. A divalent or trivalent or higher alcohol can be used as the alcohol component. Specific examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, di1,2-propanediol, polyethylene glycol, poly1,2-propanediol or polytetramethylene glycol; Bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylene bisphenol A or polyoxypropylene bisphenol A; 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-butane Examples thereof include trivalent or higher alcohols such as triol, trimethylolethane, trimethylolpropane, or 1,3,5-trihydroxymethylbenzene.

  Among these alcohol components, aliphatic diols having 2 to 8 carbon atoms are preferable, α, ω-alkanediols having 2 to 8 carbon atoms are more preferable, and 1,4-butanediol or 1 More preferred is 6-hexanediol.

  In order to obtain a crystalline polyester resin, the proportion of the aliphatic diol having 2 to 10 carbon atoms in the alcohol component is preferably 80 mol% or more, more preferably 90 mol% or more. Similarly, the content of the component (single compound) contained in the largest amount in the alcohol component is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%. Most preferred.

  As the carboxylic acid component, a divalent or trivalent or higher carboxylic acid can be used. Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, azelaic acid, malonic acid, alkyl succinic acid or alkenyl succinic acid (e.g. n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, divalent carboxylic acids such as n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid or isododecenyl succinic acid); 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5, 7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, , 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, or trivalent or higher carboxylic acid such as empole trimer acid. These divalent or trivalent or higher carboxylic acid components may be used by being transformed into ester-forming derivatives such as carboxylic acid halides, carboxylic acid anhydrides or lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  Among these carboxylic acid components, aliphatic dicarboxylic acids having 2 to 16 carbon atoms are preferable, and α, ω-alkanedicarboxylic acids having 2 to 16 carbon atoms are more preferable. The carboxylic acid component may further contain a monovalent carboxylic acid. Examples of the monovalent carboxylic acid include stearic acid.

  In order to obtain a crystalline polyester resin, the aliphatic dicarboxylic acid having 2 to 16 carbon atoms in the carboxylic acid component is preferably 70 mol% or more, and more preferably 90 mol% or more. Similarly, the content of the component (single compound) contained in the largest amount in the carboxylic acid component is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%. Is most preferred.

  The content of the crystalline polyester resin is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the toner particles. When the content of the crystalline polyester resin is 1 part by mass or more and 15 parts by mass or less, the offset resistance of the toner is improved.

[1-2. Other binder resins]
As the other binder resin, a thermoplastic resin is preferable. Examples of the thermoplastic resin include acrylic acid resin, styrene-acrylic acid resin, amorphous polyester resin, polyamide resin, urethane resin, or vinyl alcohol resin. Among these resins, an amorphous polyester resin is preferable from the viewpoint of improving the charging stability of the toner. Hereinafter, the amorphous polyester resin will be described.

  When preparing an amorphous polyester resin, it is necessary to suppress the crystallinity of the resulting polyester resin. Although the crystallinity suppression method of a polyester resin is not particularly limited, examples of the crystallinity suppression method include the following methods (A) to (C).

  Method (a): A method in which only a small amount of alcohol and carboxylic acid for improving the crystallization of the crystalline polyester resin are used or not.

  Method (b): A method of using two or more compounds as alcohol and carboxylic acid.

  Method (c): A method of suppressing crystallization by using an alcohol such as an alkylene oxide adduct of bisphenol A or a carboxylic acid such as an alkyl-substituted succinic acid.

  Among these methods for suppressing crystallization, the method (c) is more preferable because the number of types of monomers is small and the preparation of an amorphous polyester resin is easy. In the method (c), crystallization is more easily suppressed as the amounts of alcohol (for example, an alkylene oxide adduct of bisphenol A) and carboxylic acid (for example, alkyl-substituted succinic acid) are increased. However, the amount of these monomers used is preferably adjusted as appropriate in consideration of the crystallinity index of the resulting polyester resin and other physical properties. In addition, an amorphous polyester resin may be used independently and may be used in combination of 2 or more type.

  The content of the amorphous polyester resin is preferably 30 parts by weight or more and 90 parts by weight or less, and more preferably 35 parts by weight or more and 85 parts by weight or less with respect to 100 parts by weight of the toner particles.

[2. Magnetic powder]
Examples of magnetic powders include ferromagnetic metals, alloys of multiple types of ferromagnetic metals, magnetic powders composed mainly of ferromagnetic metals, magnetic powders doped with cobalt oxide or nickel in iron oxide, and no ferromagnetic metal elements. An alloy or chromium dioxide which becomes ferromagnetic by heat treatment. Examples of the ferromagnetic metal include iron, cobalt, and nickel. Iron may be used in the form of iron oxide (eg, magnetite or ferrite). As the magnetic powder, one of these magnetic powders may be used alone, or two or more thereof may be used in combination. Magnetite is preferred as the magnetic powder because the charge amount of the toner particles can be easily adjusted.

  The magnetic powder may be subjected to a surface treatment in order to improve the dispersibility of the magnetic powder in the binder resin and the durability of the magnetic powder. When surface-treating magnetic powder, examples of surface treatment agents include cationic surfactants, anionic surfactants, amphoteric surfactants, silane coupling agents, titanium coupling agents, aluminum coupling agents, phenolic resins, An epoxy resin, a cyanate resin, or a urethane resin can be used. You may use a surface treating agent individually by 1 type or in combination of 2 or more types.

[3. Crystallization inhibitor]
Examples of the crystallization inhibitor include nigrosine. Nigrosine is a mixture of various azine compounds obtained by adding hydrochloric acid to aniline or hydrochloride of aniline and nitrobenzene and subjecting to oxidation-reduction condensation reaction in the presence of a catalyst. Examples of nigrosine include C.I. I. Solvent Black 7, C.I. I. Solvent Black 5 or C.I. I. Acid Black 2 is exemplified.

  C. I. Examples of the solvent black 7 include Spirit Black SB, Spirit Black SSBB, Spirit Black AB, Spirit Black ABL, and Nubian Black (registered trademark) BLACK. ) NH-805 or Nubian Black (NUBIAN® BLACK) C.I. commercially available under the trade name NH-815. I. Solvent Black 7 (both manufactured by Orient Chemical Co., Ltd.) can be mentioned.

  In addition, C.I. I. Examples of the solvent black 5 include Nigrosine Base SA, Nigrosine Base SAP, Nigrosine Base SAPL, Nigrosine Base EE, Nigrosine E, Nigrosine E, and Nigrosine E. (Nigrosine Base) EX, Nigrosine Base EXBP, Special Black EB, Nubian Black (NUBIAN (registered trademark) BLACK) TN-870, Nubian Black (NUBIAN (registered trademark) BLACK) TN 877, Nubian Black (NUBIAN (registered trademark) B LACK) TN-807, nubian black (NUBIAN® BLACK) TH-827 or nubian gray (NUBIAN® GRAY) IR-B. I. Solvent black 5 (all manufactured by Orient Chemical Co., Ltd.) can be mentioned.

  Besides these, Bontron (registered trademark) N-01, Bontron (registered trademark) N-04, Bontron (registered trademark) (BONTRON (registered trademark)) ) N-07, Bontron (registered trademark) N-09, Bontron (registered trademark) N-21, Bontron (registered trademark) (NONTRON) N -Nigrosin marketed under the trade names of Bontron (registered trademark) N-75 and Bontron (registered trademark) N-79 (all of which are Orient Chemical Co., Ltd.) Company-made).

[4. Arbitrary ingredients]
[4-1. Charge control agent]
The toner particles may contain a charge control agent as necessary. The charge control agent is used for the purpose of improving the charge level of the toner and the charge rising characteristics of the toner. Further, it is used for the purpose of obtaining a toner having excellent durability. The toner charge rising characteristic is an index of whether or not the toner can be charged to a predetermined charge level in a short time.

  When developing with positively charged toner, it is preferable to use a positively chargeable charge control agent. On the other hand, when developing using negatively charged toner, it is preferable to use a negatively chargeable charge control agent. However, when a sufficient charge amount is secured in the toner, the charge control agent may not be used.

  Examples of positively chargeable charge control agents include azine compounds, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, alkylamides or quaternary ammonium salts (more specifically, Bontron® (BONTRON) (Registered trademark)) quaternary ammonium salt marketed under the trade name of P-51, and the like.

  A resin having a quaternary ammonium salt, a carboxylate or a carboxyl group can also be used as a positively chargeable charge control agent. A nigrosine compound is particularly preferred in order to obtain good toner charge rise characteristics. One charge control agent may be used alone, or two or more charge control agents may be used in combination.

[4-2. Release agent]
The release agent is usually used for the purpose of improving the offset resistance of the toner. In order to improve the offset resistance of the toner, the content of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin. It is more preferable that the amount is not more than parts.

  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.

  A mold release agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The melting point of the release agent is preferably 50 ° C. or higher and 150 ° C. or lower. When the melting point of the release agent is within such a range, the low-temperature fixability of the toner containing the release agent is improved, and the occurrence of offset at a high temperature of the toner tends to be suppressed. The melting point of the release agent is measured using, for example, a differential scanning calorimeter (DSC) (for example, “DSC-6220” manufactured by Seiko Instruments Inc.).

  As described above, the toner according to the first embodiment has excellent charging stability and offset resistance. Therefore, the toner according to the first embodiment can be suitably used in various image forming apparatuses.

[4-3. External additive]
Examples of the external additive include fine particles of metal oxide (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate or barium titanate) or silica fine particles. For example, the surface of the external additive may be modified with a coupling agent (more specifically, a hydrophobic treatment or a positive charging treatment).

Second Embodiment: Toner Manufacturing Method
The toner manufacturing method according to the second embodiment is a method of manufacturing the toner according to the first embodiment. The toner according to the second embodiment has the following configuration (5).
Configuration (5): In the adhesion step, a crystallization inhibitor is adhered to the surface of the magnetic powder. In the kneading step, the magnetic powder to which the crystallization inhibitor is adhered and the binder resin are kneaded to obtain a kneaded product.

  The configuration (5) is useful for providing a toner having excellent charging stability and offset resistance. In the method for producing a toner having the configuration (5), in the attaching step, a crystallization inhibitor is attached to the surface of the magnetic powder. In the kneading step, the magnetic powder to which the crystallization inhibitor is adhered and the binder resin are kneaded to obtain a kneaded product. By passing through such a process, the crystallization inhibitor is substantially adhered to the surface of the magnetic powder in the toner particles and is not substantially present in the binder resin. Since the crystallization inhibitor is not dispersed in the binder resin, the cohesive force of the toner is unlikely to decrease when the toner melts in the fixing step of the image forming step. For this reason, the manufacturing method of the toner having the configuration (5) can provide a toner having excellent offset resistance. Further, since the crystallization inhibitor exists substantially only on the surface of the magnetic powder, it tends to suppress crystallization only in the vicinity of the magnetic powder. For this reason, it is easy to control the charging stability of the toner. Therefore, the method for producing a toner having the configuration (5) can provide a toner having excellent charging stability. Therefore, the method for producing the toner having the configuration (5) can provide a toner having excellent charging stability and offset resistance.

  Further, in the method for producing a toner having the constitution (5), the crystallization inhibitor is present only in the toner particles only substantially on the surface of the magnetic powder, and is not substantially present in the binder resin. For this reason, the manufacturing method of the toner having the configuration (5) easily provides the toner having the configuration (4).

  The toner manufacturing method according to the second embodiment includes an adhesion step, a kneading step, and a pulverizing step. The toner manufacturing method according to the second embodiment may further include an external addition step. Hereinafter, an adhesion process, a kneading process, a pulverization process, and an external addition process will be described by giving an example of a toner manufacturing method according to the second embodiment.

[1. Adhesion process]
In the attaching step, a crystallization inhibitor is attached to the surface of the magnetic powder. Examples of the method for attaching the crystallization inhibitor include a method of mixing the magnetic powder and the crystallization inhibitor using a mixer (for example, FM mixer). Examples of the mixing condition include a rotation speed of 300 rpm to 2500 rpm or a rotation time of 1 minute to 10 minutes.

[2. Kneading process]
In the kneading step, the magnetic powder to which the crystallization inhibitor is adhered and the binder resin are kneaded to obtain a kneaded product. A mixture is obtained by mixing using a mixer (for example, FM mixer or Nauter mixer (registered trademark)). If necessary, a charge control agent and / or a release agent may be further added to the mixture. Subsequently, the obtained mixture is melted and kneaded using a twin-screw extruder (for example, “PCM-30” manufactured by Ikegai Co., Ltd.). The kneading temperature is preferably 80 ° C. or higher and 150 ° C. or lower. Thereby, a kneaded material is obtained.

[3. Grinding process]
In the pulverization step, the kneaded product is pulverized. In the pulverization step, first, the obtained kneaded product is primarily pulverized to obtain a primary pulverized product. Specifically, the obtained kneaded material is cooled using a drum flaker. The cooled kneaded material is first ground using a hammer mill. A sieve (for example, an opening of 5 mm) may be set on the hammer mill. Thereby, a primary pulverized product is obtained. The volume median diameter (D ₅₀ ) of the obtained primary pulverized product is preferably 100 μm or more and 1 mm or less.

Next, the primary pulverized product is pulverized (secondary pulverization). Thereby, toner particles are obtained. Specifically, the obtained primary pulverized product is subjected to secondary pulverization using a mechanical pulverizer (for example, “Turbomill T250” manufactured by Freund Turbo Inc.). For example, the secondary pulverization is preferably performed at a rotational speed of 5,000 rpm to 15,000 rpm. Next, the obtained secondary pulverized product is classified using a classifier (for example, an air classifier). Thereby, toner mother particles are obtained. The obtained toner base particles have a volume median diameter (D ₅₀ ) of preferably less than 10.0 μm, and more preferably 5.0 μm or more and 9.0 μm or less.

[4. External addition process]
In the external addition step, an external additive is attached to the surface of the toner base particles. As an example of a method for attaching an external additive, a toner (for example, an FM mixer or a Nauter mixer (registered trademark)) is used, under a condition that the external additive is not buried in the surface of the toner base particles. A method of mixing the base particles and the external additive can be mentioned. By attaching an external additive to the surface of the toner base particles, a toner containing toner particles can be obtained.

  The toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. Further, steps other than the adhering step, the kneading step and the pulverizing step, and unnecessary operations may be omitted. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously.

  As described above, the toner manufacturing method according to the second embodiment can provide a toner having excellent charging stability and adhesion.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the scope of the examples.

[1. Preparation of toner]
[1-1. Preparation of magnetic powder]
(Preparation of magnetic powder A)
40 parts by mass of magnetic powder ("BL-100" manufactured by Titanium Industry Co., Ltd.) and 3 parts by mass of nigrosine ("Bontron (registered trademark) N-01" manufactured by Orient Chemical Co., Ltd.) are mixed with an FM mixer (Nippon Coke Industries, Ltd.). The product was stirred under the conditions of a rotation speed of 500 rpm and a rotation time of 5 minutes. As a result, magnetic powder A with nigrosine attached to the surface was obtained.

(Adjustment of magnetic powder B)
Magnetic powder B was prepared in the same manner as magnetic powder A, except that the content of nigrosine was changed from 3 parts by mass to 1 part by mass.

(Preparation of magnetic powder C)
Magnetic powder C was prepared in the same manner as the magnetic powder A preparation method, except that the rotation speed was changed from 500 rpm to 2,000 rpm.

(Preparation of magnetic powder D)
3 parts by weight of nigrosine (“Bontron (registered trademark) N-01” manufactured by Orient Chemical Co., Ltd.) was dissolved in 100 parts by weight of ethanol to prepare an ethanol solution. Using a fluidized bed spray coater ("SPIR-A-FLOW (registered trademark)" manufactured by Freund Sangyo Co., Ltd.), the prepared ethanol solution was applied to magnetic powder ("BL-100" manufactured by Titanium Industry Co., Ltd.) Dried. As a result, magnetic powder D was obtained. Table 1 shows the composition of the obtained magnetic powders A to D and the method of attaching nigrosine.

[1-2. Preparation of crystalline polyester resin]
A reaction vessel was charged with 132 parts by mass of 1,6-hexanediol, 230 parts by mass of 1,10-decanedicarboxylic acid, 1 part by mass of a catalyst (dibutyltin oxide), and 0.3 part by mass of hydroquinone. Next, the inside of the reaction vessel was placed in a nitrogen atmosphere, and the temperature inside the reaction vessel was raised to 200 ° C. while stirring the contents of the reaction vessel. While distilling off by-product water at the same temperature (200 ° C.), the polymerization reaction was carried out for 5 hours. Subsequently, the pressure in the reaction vessel was reduced to 5 to 20 mmHg, the polymerization reaction was continued, and the reaction was performed at the same temperature (200 ° C.) for 1 hour. After completion of the reaction, the contents in the reaction vessel were taken out and cooled to obtain a crystalline polyester resin.

[1-3. Preparation of amorphous polyester resin]
A reaction vessel was charged with 1575 parts by mass of a propylene oxide adduct of bisphenol A, 163 parts by mass of an ethylene oxide adduct of bisphenol A, 377 parts by mass of fumaric acid, and 4 parts by mass of a catalyst (dibutyltin oxide). Next, the inside of the reaction vessel was placed in a nitrogen atmosphere, and the temperature inside the reaction vessel was raised to 220 ° C. while stirring the contents of the reaction vessel. Subsequently, after reacting at the same temperature (220 ° C.) for 8 hours, the pressure in the reaction vessel was reduced to 60 mmHg, and the reaction was performed for 1 hour. Thereafter, the reaction mixture was cooled to 210 ° C., and 336 parts by mass of trimellitic anhydride was added to the reaction vessel. After the addition of trimellitic anhydride, the reaction was carried out at the same temperature (210 ° C.) for 3 hours. After completion of the reaction, the contents in the reaction vessel were taken out and cooled to obtain an amorphous polyester resin.

Example 1
[1-4. Adjustment of toner base particles]
As the binder resin, 7 parts by mass of the crystalline polyester resin and 40 parts by mass of the amorphous polyester resin prepared as described above, 43 parts by mass of the magnetic powder A, and a release agent (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato Co., Ltd.) ) 5 parts by mass and 5 parts by mass of a charge control agent (Oriento Chemical Co., Ltd. “Bontron (registered trademark) P-51”) are charged into an FM mixer (manufactured by Nippon Coke Industries Co., Ltd.), and the contents are premixed. did. Subsequently, the mixture was kneaded using a biaxial kneader (“PCM-30” manufactured by Ikekai Tekko Co., Ltd.). The kneaded product was then cooled. Next, the cooled kneaded material was primarily pulverized using a coarse pulverizer (“Rohtoplex (registered trademark)” manufactured by Hosokawake Micron Corporation). Next, the obtained primary pulverized product was subjected to secondary pulverization using a fine pulverizer ("T-250" manufactured by Freund Turbo Co., Ltd.). Using an elbow jet classifier, the obtained secondary pulverized product was classified to obtain toner base particles. The volume median diameter of the toner base particles was 8.0 μm.

[1-5. Toner particles]
100 parts by mass of toner base particles and 0.3 part by mass of an external additive (“HDK H3050 VP” silica manufactured by Clariant Japan) were charged into an FM mixer (manufactured by Nippon Coke Industries, Ltd.). The contents were mixed to obtain toner A. It was confirmed that the crystallization inhibitor adhered to the surface of the magnetic powder, and no crystallization inhibitor was confirmed in the binder resin. That is, it was confirmed that the crystallization inhibitor is not substantially present in the binder resin.

Example 2
Except for changing 43 parts by mass of magnetic powder A to 41 parts by mass of magnetic powder B and 2 parts by mass of nigrosine (“Bontron (registered trademark) N-01” manufactured by Orient Chemical Co., Ltd.) Thus, Toner B was obtained. The volume median diameter of the toner B was 8.0 μm. It was confirmed that the crystallization inhibitor adhered to the surface of the magnetic powder, and the crystallization inhibitor in the binder resin was confirmed.

Example 3
Toner C was obtained in the same manner as in the production method of toner A, except that 43 parts by mass of magnetic powder A was changed to 43 parts by mass of magnetic powder C. The volume median diameter of the toner C was 8.0 μm. It was confirmed that the crystallization inhibitor adhered to the surface of the magnetic powder, and no crystallization inhibitor was confirmed in the binder resin. That is, it was confirmed that the crystallization inhibitor is not substantially present in the binder resin.

Example 4
Toner D was obtained in the same manner as in the production method of toner A, except that 43 parts by mass of magnetic powder A was changed to 43 parts by mass of magnetic powder D. The volume median diameter of the toner D was 8.0 μm. It was confirmed that the crystallization inhibitor adhered to the surface of the magnetic powder, and no crystallization inhibitor was confirmed in the binder resin. That is, it was confirmed that the crystallization inhibitor is not substantially present in the binder resin.

Comparative Example 1
Except for changing 43 parts by weight of magnetic powder A to 40 parts by weight of magnetic powder D and 3 parts by weight of nigrosine (“Bontron (registered trademark) N-01” manufactured by Orient Chemical Industries, Ltd.) Thus, Toner E was obtained. Magnetic powder D is magnetic powder ("BL-100" manufactured by Titanium Industry Co., Ltd.). A crystallization inhibitor in the binder resin was confirmed.

  Table 2 shows each sample (toners of Examples 1 to 4 and Comparative Example 1). In Table 2, N-01 represents “Bontron (registered trademark) N-01” manufactured by Orient Chemical Industries, Ltd., and P-51 represents “Bontron (registered trademark) P-51” manufactured by Orient Chemical Industries, Ltd. Kaunauba wax represents “Kaunauba wax No. 1” manufactured by Kato Yoko Co., Ltd.

[2. Measuring method]
(2-1. Volume median diameter and particle size distribution of toner)
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.). The volume median diameter (D ₅₀ ) is a median diameter calculated on a volume basis using a Coulter counter method.

(2-2. Presence of crystallization inhibitor)
Using a transmission electron microscope (TEM, “JSM-6700F” manufactured by JEOL Ltd.), it was confirmed that the crystallization inhibitor was adhered to the surface of the magnetic powder and contained in the binder resin. .
<Method for Taking TEM Photo of Cross Section of Toner Particle>
First, the toner was dispersed in a room temperature curable epoxy resin and allowed to stand in an atmosphere of 40 ° C. for 2 days to obtain a cured product. From the obtained cured product, a thin piece sample for cross-sectional observation of 200 nm thick toner particles was cut out using a microtome (“EM UC6” manufactured by Leica Corporation). The obtained flake sample is observed at a magnification of 10,000 times using a transmission electron microscope (TEM, “JSM-6700F” manufactured by JEOL Ltd.), and whether the crystallization inhibitor is contained in the binder resin, And it was confirmed whether the crystallization inhibitor adhering to magnetic powder exists in the magnetic powder vicinity.

[5. Evaluation method]
[5-1. Evaluation of charging stability of toner]
The sample (toner) was left exposed for 24 hours in a high temperature and high humidity environment (temperature: 32.5 ° C., humidity: 80% RH). Hereinafter, this operation may be referred to as leaving in a high temperature and high humidity environment. 5 parts by weight of the sample after being left in a high temperature and high humidity environment and 100 parts by weight of a ferrite carrier are placed in a normal environment (Temperature: T2F type manufactured by Shinmaru Enterprises Co., Ltd.) using a Turbler (registered trademark) shaker mixer. (25 ° C., humidity: 50% RH) for 30 seconds. The charge amount (μC / g) of the toner at the time of the frictional charging was measured using a suction type charge amount measuring device (“Medel 210HS” manufactured by Trek). The charge amount of the obtained toner was defined as the charge amount of the toner after being left in a high temperature and high humidity environment. The charge amount (μC / g) of the sample (toner) before being left in a high temperature and high humidity environment was measured by the same method as the charge amount of the toner after being left in a high temperature and high humidity environment. The charge amount of the obtained toner was defined as the charge amount of the toner before being left in a high temperature and high humidity environment. The charge retention rate was calculated from the charge amount of the obtained toner using Equation (6).
Charge retention ratio (%) = [charge amount of toner after leaving in high temperature and high humidity environment / charge amount of toner before leaving in high temperature and high humidity environment] × 100 (6)
The charging stability of the toner was evaluated according to the following criteria from the obtained charge retention rate.
○ (Good): The charge retention rate was 70% or more.
X (Poor): The charge retention rate was less than 70%.

[5-2. Evaluation of toner offset resistance]
As an evaluation machine, a modified machine of a printer (“FS-4020DN” manufactured by Kyocera Document Solutions Inc.) was used. This evaluation machine is a modified machine that can change the fixing control temperature of the printer. Each sample (toner) was put into this evaluation machine. Using an evaluation machine, the fixing temperature was set 10 ° C. higher than the standard control temperature, and an evaluation image was printed. The evaluation image was a solid image having a square shape. It was confirmed whether or not the solid image was smeared on the downstream side of the circumference of the fixing roller of the evaluation paper. When no dirt was confirmed, it was judged as “good”. When the dirt was confirmed, it was judged as “not good”. When the judgment result was good, the same operation as described above was performed except that the fixing temperature was further raised by 10 ° C. The same operation as above was performed until a judgment result of “not good” was obtained. The fixing temperature at which the judgment result was “not good” was defined as “offset generation temperature”. From the obtained offset generation temperature, the difference from the standard control temperature was determined using Equation (7).
Difference (° C) = Offset generation temperature-Standard control temperature (7)
The offset resistance of the toner was evaluated based on the difference based on the following criteria.
○ (Good): The difference was + 50 ° C. or more.
X (Poor): The difference was less than + 50 ° C.

  Table 3 shows the evaluation results of charging stability and offset resistance of each sample (the toners of Examples 1 to 4 and Comparative Example 1).

  As shown in Tables 1 and 2, the toners according to Examples 1 to 4 had the configuration (1). Specifically, in the toners according to Examples 1 to 4, the toner particles contained a crystalline polyester resin, a magnetic powder, and a crystallization inhibitor as a binder resin. Moreover, the crystallization inhibitor adhered to the surface of the magnetic powder. Further, the toner according to Comparative Example 1 did not have the configuration (1). Specifically, in the toner according to Comparative Example 1, no crystallization inhibitor was confirmed on the surface of the magnetic powder.

  As shown in Table 3, in the toners according to Examples 1 to 4, the charging stability and the offset resistance were both evaluated as good (good). In addition, in the toner according to Comparative Example 1, both the charging stability and the anti-offset property were evaluated as x (poor).

  From the above, it was shown that the toners according to Examples 1 to 4 have superior charging stability and offset resistance as compared with Comparative Example 1.

  As shown in Tables 1 and 2, in the toners according to Examples 1, 3, and 4, the crystallization inhibitor is substantially present only on the surface of the magnetic powder. Further, in the toner according to Example 2, the crystallization inhibitor was confirmed in the binder resin in addition to the surface of the magnetic powder.

  As shown in Table 3, in the toners according to Examples 1, 3, and 4, the charge retention rate was 85% or more, and the difference was + 80 ° C. In the toner according to Example 2, the charge retention rate was 82%, and the difference was + 60 ° C.

  From the above, it was shown that the toners according to Examples 1, 3 and 4 have improved charging stability and offset resistance as compared with the toner according to Example 2.

  The magnetic toner according to the present invention can be used for forming an image in an image forming apparatus (for example, a copying machine or a printer).

Claims (1)

A method for producing a magnetic toner containing a plurality of toner particles, comprising a crystalline polyester resin as a binder resin, magnetic powder, and a crystallization inhibitor containing nigrosine ,
A deposition step of depositing said crystallization inhibitor on the front surface of the magnetic powder,
A kneading step of kneading the magnetic powder to which the crystallization inhibitor is adhered and the binder resin to obtain a kneaded product;
And a pulverizing step of pulverizing the kneaded product.