JP6180970B2 - Magnetic one-component developing color toner and method for producing the same - Google Patents

Description

  The present invention relates to a color toner for magnetic one-component development used for electrophotographic image formation such as copying machines, printers, facsimiles, and the like, and a method for producing the same.

  In general, in electrophotography, the surface of a photosensitive drum is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The formed electrostatic latent image is developed with toner to form a toner image. Further, the formed toner image is transferred to a recording medium to obtain a high quality image. The toner used for forming a normal toner image is obtained by mixing a colorant, a charge control resin, a release agent and the like with a binder resin such as a thermoplastic resin, and then kneading, pulverizing, and classifying. Toner particles (toner mother particles) having a particle diameter of 5 to 10 μm are used. For the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, and improving the cleaning property of the toner from the photosensitive drum, inorganic fine powders such as silica and titanium oxide are used as the toner base. Externally added to the particles.

  Currently, various dry development methods in various electrophotographic methods include a two-component development method using a carrier such as toner and iron powder, and a magnetic method using a toner containing magnetic powder inside the toner without using a carrier. A one-component development system is known. The magnetic one-component development method has the merit that it is compact and low-cost, but has a demerit that it tends to be black because it contains a lot of magnetic powder, and it is difficult to colorize it. In order to solve this problem, a magnetic toner using a white pigment together (Patent Document 1) or using a transparent organic magnetic material has been proposed (Patent Document 2).

  However, the magnetic toners described in Patent Document 1 and Patent Document 2 have not been satisfactory in terms of color, magnetic force, and cost.

Japanese Patent Application No. 60-210038 JP-A-3-33866

  An object of the present invention is to provide a color toner for magnetic one-component development, which can satisfy the color, magnetic force and cost.

The present invention is a magnetic one-component developing color toner containing at least a binder resin, magnetic powder, a colorant, and a polymerization initiator, and the volume average particle diameter of the magnetic powder is 28 nm or less . The first gist of the present invention is a color toner for magnetic one-component development in which the primary particle diameter of the magnetic powder is 20 nm or less and the content of the magnetic powder in the toner is 45.9% by mass or more .

The present invention also provides a magnetic powder solution containing magnetic powder having a volume average particle diameter of 28 nm or less and a primary particle diameter of 20 nm or less , and without drying the magnetic powder solution, A second gist is a method for producing a color toner for magnetic one-component development in which a colorant and a polymerization initiator are mixed.

  According to the present invention, it is possible to obtain a magnetic one-component developing color toner that contains nano-sized magnetic powder having a volume average particle diameter of 60 nm or less and is excellent in color, magnetic force, and cost.

  Hereinafter, embodiments of the present invention will be described in detail. However, 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.

  The magnetic one-component developing color toner of the present invention (hereinafter also simply referred to as “color toner” or “toner”) contains at least a binder resin, magnetic powder, and a colorant.

  The color toner of the present invention may contain a charge control resin, a release agent and the like as desired in addition to the binder resin, the magnetic powder, and the colorant. The toner of the present invention may have a surface treated with an external additive if desired.

[Binder resin]
The binder resin contained in the toner of the present invention is not particularly limited as long as it is a resin conventionally used as a binder resin for toner. Specific examples of the binder resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether. And thermoplastic resins such as styrene resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, styrene acrylic resins and polyester resins are preferred from the viewpoints of dispersibility of the colorant in the toner, toner chargeability, and paper fixing properties.

  The styrene acrylic resin is a copolymer of a styrene monomer and an acrylic monomer. Specific examples of the styrene monomer include styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-ethylstyrene. Specific examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, meta Examples include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

  As the polyester resin, those obtained by condensation polymerization or co-condensation polymerization of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component can be used. The components used when synthesizing the polyester resin include the following alcohol components and carboxylic acid components.

  Specific examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sol Tan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2, Examples include trivalent or higher alcohols such as 4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  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, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Divalent carboxylic acids such as acids, isododecyl succinic acid, alkyl such as isododecenyl succinic acid or alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5- Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4 Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid , Tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, trivalent or higher carboxylic acid such as empole trimer acid, and the like. As these divalent or trivalent or higher carboxylic acid components, ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters may be used. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  When the binder resin is a polyester resin, the softening point of the polyester resin is preferably 80 to 150 ° C, and more preferably 90 to 140 ° C.

  As the binder resin, it is preferable to use a thermoplastic resin because of its good fixability, but not only the thermoplastic resin is used alone, but also a crosslinking agent or a thermosetting resin is added to the thermoplastic resin. It is also possible to use one. By introducing a partially crosslinked structure into the binder resin, it is possible to improve the storage stability, shape retention, durability and the like of the toner without deteriorating the toner fixability.

  As the thermosetting resin that can be used together with the thermoplastic resin, an epoxy resin or a cyanate resin is preferable. Specific examples of suitable thermosetting resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cycloaliphatic type epoxy resins, and cyanate resins. . These thermosetting resins can be used in combination of two or more.

  The glass transition point (Tg) of the binder resin is preferably 50 to 65 ° C, more preferably 50 to 60 ° C. When the glass transition point of the binder resin is too low, the toner may be fused inside the developing part of the image forming apparatus or the storage stability of the toner may be reduced, so that the toner container may be transported or stored in a warehouse. In some cases, the toner may be partially fused. In addition, when the glass transition point of the binder resin is too high, the strength of the binder resin is reduced, and the toner is likely to adhere to the latent image carrying portion. Further, when the glass transition point of the binder resin is too high, the toner tends to be difficult to fix well at a low temperature.

  In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the binder resin is measured as follows. Using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device, the glass transition point of the binder resin is determined by measuring the endothermic curve. 10 mg of binder resin as a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be determined from the endothermic curve of the binder resin obtained by measurement at a measurement temperature range of 25 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, and normal temperature and humidity.

  The amount of the binder resin used is not particularly limited as long as the object of the present invention is not impaired. Specifically, when the total amount of toner is 100 parts by mass, it is preferably 35 to 55 parts by mass, and more preferably 40 to 50 parts by mass.

[Magnetic powder]
Since the color toner of the present invention is a magnetic toner, the binder resin essentially contains magnetic powder. The kind of magnetic powder blended in the binder resin is not particularly limited as long as the object of the present invention is not impaired. Examples of suitable magnetic powders include: irons such as ferrite and magnetite; ferromagnetic metals such as cobalt and nickel; alloys containing iron and / or ferromagnetic metals; compounds containing iron and / or ferromagnetic metals; A ferromagnetic alloy subjected to a ferromagnetization treatment such as chromium dioxide.

  In addition, the magnetic powder can use what was surface-treated with surface treatment agents, such as a titanium coupling agent and a silane coupling agent, for the purpose of improving the dispersibility in binder resin.

  The volume average particle diameter of the magnetic powder is 60 nm or less, preferably 40 nm or less, more preferably 30 nm or less. When the volume average particle diameter of the magnetic powder exceeds 60 nm, the transparency of the formed image is deteriorated.

  The volume average particle diameter of the magnetic powder is measured using a particle size distribution measuring device (for example, LA-950, manufactured by Horiba, Ltd.) using, for example, a magnetic powder dispersion obtained by dispersing magnetic powder in water as a sample. Can do.

  The primary particle diameter of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less. If the primary particle diameter of the magnetic powder exceeds 50 nm, the transparency of the formed image tends to be poor.

  The primary particle size of the magnetic powder is, for example, observed with a scanning electron microscope (SEM) (for example, JSM-7600F, manufactured by JEOL Ltd.) and using image analysis software (for example, WinROOF, manufactured by Mitani Corporation). The primary particle diameter of the magnetic powder can be calculated from the equivalent circle diameter.

  The content of the magnetic powder in the toner is preferably 30% by mass or more, more preferably 35% by mass or more. When the content of the magnetic powder in the toner is less than 30% by mass, the formed image is likely to be fogged or the image density of the formed image may be lower than a desired value when printing is performed for a long period of time. .

[Colorant]
As the colorant contained in the color toner of the present invention, a known pigment or dye can be used in accordance with the color of the toner particles. Specific examples of suitable colorants that can be added to the toner include the following colorants.

  The yellow colorant is preferably composed of, for example, a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, and an allylamide compound. Examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, 194, etc.), Neftol Yellow S, Hansa Yellow G, C.I. I. Butt yellow is preferred.

  The magenta colorant is preferably composed of, for example, a condensed azo compound, diketopyrrolopyrrole compound, anthraquinone compound, quinacridone compound, basic dye lake compound, naphthol compound, benzimidazolone compound, thioindigo compound, and perylene compound. Examples of magenta colorants include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 , 184, 185, 202, 206, 220, 221, 254, etc.).

  The cyan colorant is preferably composed of, for example, a copper phthalocyanine compound, a copper phthalocyanine derivative, an anthraquinone compound, or a basic dye lake compound. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66, etc.), phthalocyanine blue, C.I. I. Bat Blue, C.I. I. Acid blue is preferred.

  Each color of these colorants can be used alone or in combination. A black colorant such as carbon black can also be mixed and used. The amount of the colorant used is not particularly limited as long as the object of the present invention is not impaired. Specifically, 1 to 20 parts by mass is preferable with respect to 100 parts by mass of the binder resin, and more preferably 1 to 10 parts by mass.

[Charge control resin]
The color toner of the present invention may contain a charge control resin. The kind of the charge control resin is not particularly limited as long as the object of the present invention is not impaired. For example, a resin having a quaternary ammonium salt, a carboxylate, or a carboxyl group as a functional group can be used.

  More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, and a carboxylate A styrene resin having a carboxylate, an acrylic resin having a carboxylate, a styrene-acrylic resin having a carboxylate, a polyester resin having a carboxylate, a styrene resin having a carboxyl group, an acrylic resin having a carboxyl group, One type or two or more types such as a styrene-acrylic resin having a carboxyl group and a polyester resin having a carboxyl group may be mentioned. The molecular weight of these resins is not particularly limited as long as the object of the present invention is not impaired, and may be an oligomer or a polymer.

  Among such charge control resins, it is easy to favorably disperse the charge control resin in the binder resin in a desired state, and it is easy to produce a toner having the charge control resin attached to the surface of the toner particles. Therefore, a resin in which a positively or negatively charged functional group is introduced into a styrene-acrylic resin is preferable.

  Among the resins that can be used as the positively chargeable charge control resin, a styrene-acrylic resin having a quaternary ammonium salt as a functional group is preferable because the charge amount can be easily adjusted to a value within a desired range. More preferred. Specific examples of preferred acrylic comonomers copolymerized with styrene units for styrene-acrylic resins having a quaternary ammonium salt as a functional group include methyl acrylate, ethyl acrylate, n-propyl acrylate, and iso-acrylate. (Meth) acrylic such as propyl, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate Examples include acid alkyl esters.

  As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate, dialkyl (meth) acrylamide, or dialkylaminoalkyl (meth) acrylamide through a quaternization step is used. Specific examples of the dialkylaminoalkyl (meth) acrylate include, for example, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, Specific examples of dialkyl (meth) acrylamide include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl (meth) acrylamide include dimethylaminopropyl methacrylamide. Further, a hydroxy group-containing polymerizable monomer such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, or N-methylol (meth) acrylamide can be used in combination during polymerization.

  A suitable negatively chargeable charge control resin, for example, a resin obtained by copolymerizing a carboxyl group or a monomer having an unsaturated bond with a carboxylate group with the aforementioned acrylic comonomer or styrene can be used. Specific examples of the monomer having an unsaturated bond having a carboxyl group or a carboxylate group include acrylic acid, methacrylic acid, maleic acid, acrylate, methacrylate and maleate. As the carboxylate contained in the carboxylate group, an alkali metal salt of carboxylic acid is preferable, and a sodium carboxylate or potassium carboxylate is preferred. These negatively chargeable charge control resins can be used in combination of two or more.

  The amount of the positively or negatively chargeable charge control resin used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the positively or negatively chargeable charge control resin used is preferably 1.5 to 15 parts by mass, and 2.0 to 8.0 parts by mass when the total amount of toner is 100 parts by mass. Part is more preferable, and 4.0 to 7.0 parts by weight is particularly preferable.

  When the amount of the charge control resin used is too small, the image charge density of the formed image may be lower than desired because the charge rising characteristics of the toner are not good during the initial image formation. When the amount of the charge control resin used is excessive, the toner is likely to be poorly charged, so that the formed image is likely to be fogged.

〔Release agent〕
The color toner of the present invention may contain a release agent. The type of release agent added to the toner is not particularly limited as long as the object of the present invention is not impaired. As the mold release agent, a wax is preferable, and specific examples of the wax include polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, and rice wax. These release agents can be used in combination of two or more. By adding these release agents to the toner, the occurrence of offset and image smearing (dirt around the image when the image is rubbed) can be more efficiently suppressed.

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. The specific amount of the release agent used is preferably 1 to 10 parts by mass when the total amount of toner is 100 parts by mass. If the amount of release agent used is too small, the desired effect may not be obtained with respect to suppression of occurrence of offset and image smearing. If the amount of release agent used is excessive, fusion between toners may occur. Depending on the case, the storage stability of the toner may decrease.

(External additive)
The surface of the toner of the present invention can be treated with an external additive as desired. The type of external additive is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from external additives conventionally used for toners. Specific examples of suitable external additives include silica or metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more. These external additives can also be used after being hydrophobized with a hydrophobizing agent such as an aminosilane coupling agent or silicone oil. When using a hydrophobized external additive, it is easy to suppress a decrease in charge amount under high temperature and high humidity, and it is easy to obtain a toner having excellent fluidity.

  The amount of the external additive used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the external additive used is preferably 0.5 to 5% by mass with respect to the total mass of the toner particles before the external addition treatment.

[Method of producing color toner for magnetic one-component development]
The method for producing the color toner of the present invention is not particularly limited as long as a color toner containing magnetic powder having a volume average particle diameter of 60 nm or less can be obtained. Specifically, the magnetic powder produced in an aqueous solution is once used. It is preferable to add to the toner without drying.

  A specific example of a suitable method for producing such a color toner will be described below.

(Preparation of magnetic powder solution)
For example, a sodium hydroxide aqueous solution is added to a ferrous sulfate aqueous solution, and the pH is adjusted by heating. While maintaining the liquid temperature, air is blown to carry out the oxidation reaction. After adding sulfuric acid aqueous solution to this suspension so that pH may be set to 7.0, air is blown in maintaining liquid temperature, and magnetic powder (for example, magnetite particle) is produced. The obtained solution containing the magnetic powder is filtered and washed with ion exchange water by a conventional method to obtain a solution containing 50% by mass of the magnetic powder, and 1 part by mass of a highly hydrophobic surfactant with respect to 100 parts by mass of this solution. Add to produce a magnetic powder solution. The magnetic powder in this solution has a volume average particle size of 60 nm or less.

(Manufacture of color toners)
The magnetic powder produced as described above, a binder resin monomer, a colorant, and optional components such as a charge control resin and a release agent, if necessary, are mixed by a mixer or the like to obtain a mixture. Next, a polymerization initiator and a suspension stabilizer are added to the obtained mixture, and the mixture is stirred to form toner droplets and then polymerized. This toner dispersion is filtered, washed and dried to obtain a toner raw powder (toner mother particles). If necessary, an external additive may be attached to the surface of the toner base particles. The method for attaching the external additive to the surface of the toner base particles is not particularly limited, and can be appropriately selected from conventionally known methods. Specifically, the processing conditions are adjusted so that the particles of the external additive are not embedded in the surface of the toner base particles, and the toner base particles and the external additive are mixed by a mixer such as a Henschel mixer or a Nauter mixer. By the method, the toner base particles are treated with an external additive.

When the color toner of the present invention is a cyan toner, the L value at a toner amount of 0.7 mg / cm ² is preferably 40 or more, more preferably 46 or more.

When the color toner of the present invention is a yellow toner, the L value when the toner amount is 0.7 mg / cm ² is preferably 60 or more, more preferably 69 or more.

Further, when the color toner of the present invention is a magenta toner, the L value at a toner amount of 0.7 mg / cm ² is preferably 36 or more, more preferably 40 or more.

  According to the color toner for magnetic one-component development of the present invention described above, the color, magnetic force and cost can be satisfied. For this reason, the toner for magnetic one-component developer of the present invention is suitably used in various image forming apparatuses adopting the magnetic one-component developing system.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to these examples.

[Example 1]
(Production of magnetic powder solution A)
28 L of 4.5N sodium hydroxide aqueous solution was added to 30 L of 2 mol / L ferrous sulfate aqueous solution and heated to 90 ° C. to adjust the pH to 10.5. While maintaining the liquid temperature at 90 ° C., an oxidation reaction was performed by blowing 80 L of air per minute for 100 minutes. After adding a 2 mol / L sulfuric acid aqueous solution to this suspension so that the pH was 7.0, 80 L of air was blown for 10 minutes per minute while maintaining the liquid temperature at 90 ° C. to generate magnetite particles. The obtained solution containing magnetite particles is filtered and washed with ion-exchanged water by a conventional method to obtain a solution containing 50% by mass of magnetite, and a highly hydrophobic surfactant (Nonion SP-60R) with respect to 100 parts by mass of this solution. 1 part by mass was added to produce a magnetic powder solution A. The magnetite in this solution was an octahedron having a volume average particle size of 28 nm and a primary particle size of 20 nm. The volume average particle diameter and primary particle diameter were measured by the following methods.

<Measurement method of volume average particle diameter of magnetic powder>
The volume average particle size of the magnetic powder was measured with a particle size distribution measuring device (LA-950, manufactured by Horiba, Ltd.) using a magnetic powder dispersion in which the magnetic powder was dispersed in water as a sample.

<Measurement method of primary particle size of magnetic powder>
Observe the image with a scanning electron microscope (SEM) (JSM-7600F, manufactured by JEOL Ltd.) and use image analysis software (WinROOF, manufactured by Mitani Corp.) to calculate the primary particle diameter of the magnetic powder from the equivalent circle diameter. did.

(Manufacture of cyan toner)
80 parts by mass of styrene, 20 parts by mass of 2-ethylhexyl methacrylate, 7 parts by mass of Toner Cyan BG (manufactured by Clariant Japan), 5 parts by mass of low molecular weight polypropylene (Sunwax LEL-250, manufactured by Sanyo Chemical Co., Ltd.), charge control agent (FCA207 200 parts by mass of the above magnetic powder solution A was added to a mixed solution of 5 parts by mass of Fujikura Kasei Co., Ltd. and 1 part by mass of divinylbenzene (crosslinking agent). After sufficiently dispersing with a ball mill, 3 parts by mass of a polymerization initiator 2,2-azobis (2,4-dimethylvaleronitrile) is added, and it is added to 400 parts by mass of ion-exchanged water, and further as a suspension stabilizer. 6 parts by mass of tribasic calcium phosphate and 0.2 parts by mass of sodium dodecylbenzenesulfonate were added, and the mixture was stirred for 120 minutes at a rotation speed of 6000 rpm using a TK homomixer (manufactured by Koki Kogyo Co., Ltd.). After a polymerization reaction at 100 rpm for 10 hours, acid washing was performed to remove tricalcium phosphate. This toner dispersion was filtered, washed and dried to obtain a toner raw powder. The obtained toner particles had a volume average particle size of 8.1 μm. To 100 parts by mass of this toner, 0.7 parts by mass of silica fine particles (RA200, manufactured by Aerosil Co., Ltd.) and 0.5 parts by mass of titanium oxide particles (EC100, manufactured by Titanium Industry Co., Ltd.) are added, and a Henschel mixer (FM-20) is added. Cyan toner was manufactured by spraying with Nippon Coke.

[Example 2]
(Production of magnetic powder solution B)
A magnetic powder solution B was manufactured and manufactured according to the above-described manufacturing method of the magnetic powder solution A, except that the oxidation reaction time was changed. That is, a magnetic powder solution B was manufactured and manufactured according to the above-described manufacturing method of the magnetic powder solution A, except that 80 L of air was blown for 180 minutes and the oxidation reaction was performed while maintaining the liquid temperature at 90 ° C. The magnetite in this solution was an octahedron having a volume average particle size of 60 nm and a primary particle size of 50 nm.

Example 3
(Manufacture of cyan toner)
A cyan toner was produced in the same manner as in Example 1 except that the addition amount of the magnetic powder solution A was changed to 110 parts by mass.

[Comparative Example 1]
(Production of dried magnetite)
The magnetic powder solution A produced as described above is dried (conditions: 180 ° C. × 24 hours, device name: manufactured by Tabay Espec, PH-200), and then Henschel mixer (FM-20, manufactured by Nippon Coke). The magnetite was crushed and dried to produce magnetite. The obtained magnetite was an octahedron having a volume average particle size of 126 nm and a primary particle size of 20 nm.

(Manufacture of cyan toner)
A cyan toner was produced in the same manner as in Example 1 except that 50 parts by mass of dried magnetite was used instead of 100 parts by mass of the magnetic powder solution A.

[Comparative Example 2]
(Production of magnetic powder solution C)
A magnetic powder solution C was produced according to the above-described method for producing the magnetic powder solution A, except that the oxidation reaction time was changed. That is, a magnetic powder solution C was manufactured and manufactured according to the above-described manufacturing method of the magnetic powder solution A, except that the oxidation reaction was performed by blowing 80 L of air per minute for 200 minutes while maintaining the liquid temperature at 90 ° C. The magnetite in this solution was an octahedron having a volume average particle size of 74 nm and a primary particle size of 60 nm.

(Manufacture of cyan toner)
A cyan toner was produced in the same manner as in Example 1 except that the magnetic powder solution C was used instead of the magnetic powder solution A.

[Comparative Example 3]
A cyan toner was produced in the same manner as in Example 1 except that the magnetic powder solution A was not used.

≪Evaluation≫
Using the cyan toners of Examples 1 to 3 and Comparative Examples 1 to 3, the characteristics were evaluated according to the following criteria. The results are shown in Table 1 below.

[Image evaluation]
Using a printer (FS-1370DN, manufactured by Kyocera Document Solutions Co., Ltd.), a cyan toner of Examples and Comparative Examples was set in the developing unit, and an image was output by adjusting the developing bias.
In Comparative Example 3, the printer was changed to a printer (DP-560 manufactured by Kyocera Document Solutions Inc.) (non-magnetic one-component system), and an image was output in the same manner.

[Color evaluation]
The toner amount of the solid part on the paper surface was adjusted to 0.7 mg / cm ² . CIE Lab coordinates were measured at the center of a solid image of 2.5 cm × 2.5 cm with SpectroEye (GretagMacbeth).

  From the results of Table 1 above, in Examples 1 to 3, since the magnetic powder solution was made into toner without drying, it was possible to maintain transparency without agglomeration of nano-sized magnetic powder. Therefore, the L value was 40 or more, and the cyan color evaluation was good.

On the other hand, in Comparative Example 1, since the magnetic powder solution was dried, the nano-sized magnetic powder was agglomerated by drying, the particle size was increased, and transparency was lost. Therefore, the L value was less than 40, and the cyan color evaluation was inferior.
In Comparative Example 2, since the volume average particle diameter of the magnetic powder was too large, the L value was less than 40 and the cyan color evaluation was inferior.

Example 4
(Production of magnetic powder solution A)
A magnetic powder solution A was produced as described above.

(Manufacture of yellow toner)
A yellow toner was produced in the same manner as in Example 1 except that Toner Yellow HG (manufactured by Clariant Japan) was used instead of Toner Cyan BG (manufactured by Clariant Japan).

Example 5
(Production of magnetic powder solution B)
A magnetic powder solution B was produced as described above.

(Manufacture of yellow toner)
A yellow toner was produced in the same manner as in Example 4 except that the magnetic powder solution B was used in place of the magnetic powder solution A.

[Comparative Example 4]
(Production of dried magnetite)
The dried magnetite was produced as described above.

(Manufacture of yellow toner)
A yellow toner was produced in the same manner as in Example 4 except that 50 parts by mass of dried magnetite was used instead of 100 parts by mass of the magnetic powder solution A.

[Comparative Example 5]
(Production of magnetic powder solution C)
A magnetic powder solution C was produced as described above.

(Manufacture of yellow toner)
A yellow toner was produced in the same manner as in Example 4 except that the magnetic powder solution C was used in place of the magnetic powder solution A.

[Comparative Example 6]
A yellow toner was produced in the same manner as in Example 4 except that the magnetic powder solution A was not used.

≪Evaluation≫
Using the yellow toners of Examples 4 and 5 and Comparative Examples 4 to 6, each characteristic was evaluated according to the above-mentioned criteria. The results are shown in Table 2 below.

  From the results of Table 2 above, in Examples 4 and 5, since the magnetic powder solution was made into toner without drying, the nano-sized magnetic powder could be kept transparent without agglomeration. Therefore, the L value was 60 or more, and the yellow color evaluation was good.

On the other hand, in Comparative Example 4, since the magnetic powder solution was dried, the nano-sized magnetic powder was agglomerated by drying, the particle size was increased, and transparency was lost. Therefore, the L value was less than 60, and the yellow color evaluation was inferior.
In Comparative Example 5, since the volume average particle diameter of the magnetic powder was too large, the L value was less than 60, and the yellow color evaluation was inferior.

Example 6
(Production of magnetic powder solution A)
A magnetic powder solution A was produced as described above.

(Manufacture of magenta toner)
Magenta toner was produced in the same manner as in Example 1 except that Toner Yellow HG (manufactured by Clariant Japan) was used instead of Toner Yellow HG (manufactured by Clariant Japan).

Example 7
(Production of magnetic powder solution B)
A magnetic powder solution B was produced as described above.

(Manufacture of magenta toner)
A magenta toner was produced in the same manner as in Example 6 except that the magnetic powder solution B was used in place of the magnetic powder solution A.

[Comparative Example 7]
(Production of dried magnetite)
The dried magnetite was produced as described above.

(Manufacture of magenta toner)
A magenta toner was produced in the same manner as in Example 6 except that 50 parts by mass of dried magnetite was used instead of 100 parts by mass of the magnetic powder solution A.

[Comparative Example 8]
(Production of magnetic powder solution C)
A magnetic powder solution C was produced as described above.

(Manufacture of magenta toner)
A magenta toner was produced in the same manner as in Example 6 except that the magnetic powder solution C was used in place of the magnetic powder solution A.

[Comparative Example 9]
A magenta toner was produced in the same manner as in Example 6 except that the magnetic powder solution A was not used.

≪Evaluation≫
Using the magenta toners of Examples 6 and 7 and Comparative Examples 7 to 9, each characteristic was evaluated according to the above-mentioned criteria. The results are shown in Table 3 below.

  From the results of Table 3 above, in Examples 6 and 7, the magnetic powder solution was converted into a toner without being dried, so that the nano-sized magnetic powder was not aggregated and the transparency could be maintained. Therefore, the L value was 36 or more, and the magenta color evaluation was good.

On the other hand, in Comparative Example 7, since the magnetic powder solution was dried, the nano-sized magnetic powder was agglomerated by drying, the particle size was increased, and transparency was lost. Therefore, the L value was less than 36, and the magenta color evaluation was poor.
In Comparative Example 8, since the volume average particle diameter of the magnetic powder was too large, the L value was less than 36, and the magenta color evaluation was inferior.

  The present invention is useful for various image forming apparatuses that employ a magnetic one-component development system.

Claims (6)

And at least a binder resin, a magnetic powder, a colorant, a magnetic one-color toner for component developer containing a polymerization initiator, a volume average particle diameter of the magnetic powder at 28 nm or less, the magnetic powder A color toner for magnetic one-component development, having a primary particle diameter of 20 nm or less and a magnetic powder content in the toner of 45.9% by mass or more . 2. A color toner for magnetic one-component development according to claim 1, wherein the polymerization initiator is 2,2-azobis (2,4-dimethylvaleronitrile) . The color toner for magnetic one-component development according to claim 1, wherein the toner is a cyan toner having an L value of 49 or more at a toner amount of 0.7 mg / cm ² . The color toner for magnetic one-component development according to claim 1, wherein the toner is a yellow toner having an L value of 69 or more at a toner amount of 0.7 mg / cm ² . The color toner for magnetic one-component development according to claim 1, wherein the toner is a magenta toner having an L value of 40 or more at a toner amount of 0.7 mg / cm ² . A magnetic powder solution containing a magnetic powder having a volume average particle diameter of 28 nm or less and a primary particle diameter of 20 nm or less is prepared, and the binder resin, the colorant, and the polymerization initiator are dried without drying the magnetic powder solution. The method for producing a color toner for magnetic one-component development according to any one of claims 1 to 5, wherein: