JP2017111282A - Positively chargeable toner and method for producing positively chargeable toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively chargeable toner capable of achieving all of charging stability, low-temperature fixability and heat-resistant storage property.SOLUTION: The positively chargeable toner comprises a plurality of toner particles 1. The toner particle 1 has a composite particle 5 and a shell layer 4 covering the composite particle 5. The composite particle 5 comprises a toner core 2 and a plurality of magnetic powder particles 3 provided on a surface of the toner core 2. The shell layer 4 comprises a thermosetting resin. The content of the magnetic powder particles 3 is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core 2. The magnetic powder particle 3 has a polyhedral form. An average Heywood diameter of the magnetic powder particle 3 is 0.010 μm or more and 0.500 μm or less. The magnetic powder particle 3 has a volume resistivity value of 1×10Ω cm or more and 1×10Ω cm or less. The surface of the composite particle 5 is negatively chargeable. The composite particle 5 has a triboelectric charge amount of -9 μC/g or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positively chargeable toner (particularly a positively chargeable toner for developing an electrostatic latent image) and a method for producing a positively chargeable toner.

  When an image is formed on a recording medium using the image forming apparatus and the electrostatic latent image developing toner, the electrostatic latent image developing toner is transferred to the recording medium. By applying heat and pressure to the transferred electrostatic latent image developing toner using, for example, a fixing roller, the electrostatic latent image developing toner is fixed on the recording medium. In order to form a high-quality image while reducing the energy required for fixing, it is desired to improve the fixability of the electrostatic latent image developing toner to the recording medium. Various studies have been made to improve the fixability of the electrostatic latent image developing toner. For example, in the electrostatic latent image developing toner described in Patent Document 1, the surface of the toner core is coated with urea resin. The urea resin is formed by resinating the concentrated urea resin precursor on the surface of the toner core without melting the toner core.

JP 2004-294468 A

  However, since the shell layer of the electrostatic latent image developing toner described in Patent Document 1 contains a urea resin, the low-temperature fixability and heat-resistant storage stability of the electrostatic latent image developing toner are insufficient. In addition, it is difficult to improve the charging stability with the electrostatic latent image developing toner described in Patent Document 1.

  The present invention has been made in view of the above problems, and an object thereof is to provide a positively chargeable toner capable of achieving both charging stability, low-temperature fixability and heat-resistant storage stability. Another object of the present invention is to provide a method for producing a positively chargeable toner capable of achieving both charge stability, low temperature fixability and heat resistant storage stability.

The positively chargeable toner according to the present invention includes a plurality of toner particles. The toner particles include composite particles and a shell layer that covers the composite particles. The composite particles have a toner core and a plurality of magnetic powder particles provided on the surface of the toner core. The shell layer contains a thermosetting resin. The content of the magnetic powder particles is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core. The magnetic powder particles have a polyhedral shape. The average haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.500 μm or less. The magnetic powder particles have a volume resistivity of 1 × 10 ² Ω · cm to 1 × 10 ⁸ Ω · cm. The surface of the composite particle has negative chargeability. The composite particles have a triboelectric charge amount of −9 μC / g or less.

The positively chargeable toner manufacturing method according to the present invention is a positively chargeable toner manufacturing method including a plurality of toner particles. The method for producing a positively chargeable toner according to the present invention includes a composite particle forming step and a shell layer forming step. In the composite particle forming step, a plurality of magnetic powder particles are attached to the surface of the toner core to form composite particles. In the shell layer forming step, a shell layer is formed so as to cover the composite particles by polymerizing or copolymerizing a thermosetting resin material on the surface of the composite particles. In the composite particle forming step, the addition amount of the magnetic powder particles is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core. The shell layer formed in the shell layer forming step contains a thermosetting resin. The magnetic powder particles have a polyhedral shape. The average haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.500 μm or less. The magnetic powder particles have a volume resistivity of 1 × 10 ² Ω · cm to 1 × 10 ⁸ Ω · cm. The surface of the composite particle has negative chargeability. The composite particles have a triboelectric charge amount of −9 μC / g or less.

  According to the positively chargeable toner of the present invention, it is possible to achieve both charging stability, low-temperature fixability and heat-resistant storage stability. Further, according to the method for producing a positively chargeable toner of the present invention, it is possible to provide a positively chargeable toner that can achieve both charge stability, low-temperature fixability and heat-resistant storage stability.

3 is a cross-sectional view showing toner particles contained in a positively chargeable toner according to an exemplary embodiment of the present invention. It is a figure for demonstrating an example of reaction with composite particle | grains and the material of a thermosetting resin. It is a figure for demonstrating another example of reaction with composite particle | grains and the material of a thermosetting resin.

  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) regarding a powder (for example, toner, toner core, composite particle, toner particle, and toner base particle described later) means a number average value unless specified. To do. 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. Furthermore, the particle diameter of the powder is the equivalent-circle diameter of primary particles measured using 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 a positively chargeable toner (hereinafter sometimes referred to as toner). The toner according to the exemplary embodiment is used to form an image with an electrophotographic image forming apparatus, for example. The toner according to this embodiment is developed in a positively charged state.

  According to the toner of the present exemplary embodiment, it is possible to achieve both charging stability, low-temperature fixability, and heat-resistant storage stability. Here, the characteristic that the toner charge amount distribution is sharp, the characteristic that the toner can be charged to a desired charge amount when starting to form an image using toner, and the case where images are continuously formed using toner A toner having a characteristic capable of charging the toner to a desired charge amount is a toner having excellent charging stability.

  The toner of the present embodiment includes a plurality of toner particles. The toner is a powder composed of a large number of toner particles. The toner substantially contains capsule toner particles having a shell layer, but may contain non-capsule toner particles not having a shell layer.

  Hereinafter, the structure of the toner particles 1 will be described with reference to FIG. FIG. 1 is a cross-sectional view showing toner particles 1 contained in the toner according to the present embodiment. The toner particles 1 have composite particles 5 and a shell layer 4. The composite particle 5 has a toner core 2 and a plurality of magnetic powder particles 3. Magnetic powder particles 3 are provided on the surface of the toner core 2. The shell layer 4 covers the composite particles 5. The shell layer 4 is provided so as to cover both the toner core 2 and the magnetic powder particles 3. The magnetic powder particles 3 are provided on the surface of the toner core 2 while being covered with the shell layer 4. The structure of the toner particle 1 has been described above with reference to FIG.

<1. Composite particles>
Next, the magnetic powder particles and the toner core included in the composite particles will be described.

<1-1. Magnetic powder particles>
A plurality of magnetic powder particles are provided on the surface of the toner core. The shell layer covers the toner core and the magnetic powder particles provided on the surface of the toner core. The toner having such a structure is considered to have the following advantages.

  The first advantage will be described. In a normal toner, the thickness and properties of the shell layer may become nonuniform due to variations in the shape and particle size distribution of the toner core and the polymerization conditions when forming the shell layer. When the shell layer contains a thermosetting resin (for example, melamine resin) and the thermosetting resin has a cationic group (a group that forms an ion having a positive charge), the shell layer tends to exhibit positive chargeability. is there. Since the shell layer exhibits positive chargeability, if the thickness and properties of the shell layer are not uniform, the charge amount of the toner particles having the shell layer may be non-uniform and the toner charge amount distribution may be broad. is there. However, in the toner of the present embodiment, as described above, the shell layer covers the toner core and the magnetic powder particles provided on the surface of the toner core. By containing magnetic powder particles in the shell layer, it is considered that the internal electrical resistance of the shell layer exhibiting positive chargeability can be adjusted to a desired value. As a result, the charge amount of the toner particles can be made uniform, and the charge amount distribution of the toner can be sharpened. Further, even when images are continuously formed using toner, it is possible to suppress the toner charge amount from being excessively increased (charged up), and to suppress a decrease in image density of the formed image. be able to.

  The second advantage will be described. In a toner in which the shell layer contains a thermosetting resin, the shell layer is generally not easily broken even when heat and pressure are applied to the toner at the time of fixing the toner. Therefore, such toner tends to be inferior in low-temperature fixability. However, in the toner of this embodiment, as described above, the shell layer covers the toner core and the magnetic powder particles provided on the surface of the toner core. Therefore, when heat and pressure are applied to the toner at the time of fixing the toner, it is considered that the magnetic powder particles existing inside the shell layer become a starting point for destroying the shell layer. As a result, the low-temperature fixability of the toner can be improved.

  The third advantage will be described. In the toner of the present embodiment, a plurality of magnetic powder particles are provided on the surface of the toner core. By arranging the magnetic powder particles at a relatively outer edge of the toner particles, for example, when developing the toner using an image forming apparatus including a magnet roller, the toner is easily held by the magnet roller. As a result, it is considered that fog and toner scattering can be suppressed in the formed image.

  The content of the magnetic powder particles is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core. When the content of the magnetic powder particles is less than 0.50 parts by mass with respect to 100.00 parts by mass of the toner core, it is difficult to adjust the electric resistance inside the shell layer to a desired value. As a result, the toner charge amount distribution tends to be broad. Further, when images are continuously formed using toner, the charge amount of the toner tends to increase too much, and the image density of the formed image tends to decrease. On the other hand, if the content of magnetic powder particles exceeds 3.00 parts by mass with respect to 100.00 parts by mass of the toner core, the toner charge amount tends to decrease when images are continuously formed using toner. is there. This is because many magnetic powder particles having a relatively low electrical resistance are contained.

  Further, when the content of the magnetic powder particles is less than 0.50 parts by mass with respect to 100.00 parts by mass of the toner core, the low-temperature fixability of the toner tends to be lowered. This is because there are few magnetic powder particles as starting points for destroying the shell layer. On the other hand, when the content of the magnetic powder particles exceeds 3.00 parts by mass with respect to 100.00 parts by mass of the toner core, the low-temperature fixability of the toner tends to decrease. This is because many magnetic powder particles that are difficult to melt at the fixing temperature of the toner are contained.

  The magnetic powder particles have a polyhedral shape. Since the magnetic powder particles having a polyhedral shape have apexes and sides, charges are easily released from the apexes and sides. For this reason, the toner particles provided with magnetic powder particles having a polyhedral shape do not have an excessive charge amount as compared with toner particles provided with spherical magnetic powder particles. Further, since the magnetic powder particles having a polyhedral shape are present in the shell layer, when heat and pressure are applied to the toner at the time of fixing the toner, sharp portions such as the apexes and sides of the magnetic powder particles form the shell layer. It becomes the starting point to destroy. As a result, the shell layer is easily broken at the time of fixing the toner, and the low-temperature fixability of the toner can be improved.

  Examples of the polyhedron shape include an octahedron shape or a hexahedron shape. Specifically, the octahedron shape includes a convex octahedron shape surrounded by eight triangles. Specific examples of the hexahedral shape include a convex hexahedral shape surrounded by six squares. In the polyhedron shape, each vertex and each side included in the polyhedron may be pointed. Alternatively, the polyhedron shape may be a shape in which one or both of each vertex and each side included in the polyhedron are curved and a portion that can be regarded as a straight line exists in the outer peripheral portion of the projected image of the polyhedron.

  The shape of the magnetic powder particles can be changed, for example, by appropriately changing the pH of the aqueous metal solution in the magnetic powder core forming step described later. The shape of the magnetic powder particles is confirmed, for example, by observing the magnetic powder particles at an observation magnification of 50,000 using a scanning electron microscope (SEM, “JSM-880” manufactured by JEOL Ltd.).

  The average Haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.500 μm or less. The Haywood diameter (Heywood diameter) of the magnetic powder particles is a circle-equivalent diameter of the projected area of the magnetic powder particles. When the average haywood diameter of the magnetic powder particles is less than 0.010 μm, the magnetic powder particles are likely to aggregate, and the dispersibility of the magnetic powder particles with respect to the toner core may be reduced in the composite particle forming step described later. Therefore, it becomes difficult for the magnetic powder particles to adhere uniformly to the surface of the toner core. As a result, the toner charge amount distribution becomes broad and the toner charge amount tends to increase too much. In addition, since the magnetic powder particles are difficult to uniformly adhere to the surface of the toner core, the magnetic powder particles are unlikely to become a starting point for the destruction of the shell layer. As a result, the low-temperature fixability of the toner tends to decrease. On the other hand, when the average Haywood diameter of the magnetic powder particles exceeds 0.500 μm, the magnetic powder particles are easily detached from the toner core in the composite particle forming step described later, and the magnetic powder particles are difficult to be fixed in the shell layer. Also, the particle size distribution of the magnetic powder particles tends to be broad, and the magnetic powder particles are difficult to uniformly adhere to the surface of the toner core. As a result, the toner charge amount distribution becomes broad and the toner charge amount tends to increase too much. In addition, the magnetic powder particles are difficult to be fixed in the shell layer, and the magnetic powder particles are less likely to be a starting point for destruction of the shell layer. As a result, the low-temperature fixability of the toner tends to decrease.

  The average Haywood diameter of the magnetic powder particles is preferably 0.010 μm or more and 0.300 μm or less. When the average Haywood diameter of the magnetic powder particles is within such a range, the high temperature offset resistance of the toner can be improved. In order to particularly improve the high temperature offset resistance of the toner when the average haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.300 μm or less, the triboelectric charge amount of the composite particles described later is −20 μC / g or more − It is preferably 15 μC / g or less.

  The average haywood diameter of the magnetic powder particles is determined by, for example, the growth conditions of the metal particles (for example, the heating temperature of the aqueous metal solution, the speed of the air that is passed through the aqueous metal solution, and the aqueous metal solution in the magnetic powder core forming step described later). It can be adjusted by appropriately changing the time during which air is vented.

  The average Haywood diameter of the magnetic powder particles is measured by the following method, for example. Using a scanning electron microscope (SEM, “JSM-880” manufactured by JEOL Ltd.) and an image analyzer, a considerable number of magnetic powder particles are measured at an observation magnification of 50,000 times. The sum of all measured Haywood diameters is divided by the number of measured magnetic powder particles. Thereby, the average haywood diameter (number average haywood diameter) of the magnetic powder particles is calculated.

The volume resistivity of the magnetic powder particles is 1 × 10 ² Ω · cm or more and 1 × 10 ⁸ Ω · cm or less. When the volume resistivity of the magnetic powder particles is less than 1 × 10 ² Ω · cm, the charge amount of the toner tends to decrease particularly when images are formed continuously. On the other hand, if the volume resistivity value of the magnetic powder particles exceeds 1 × 10 ⁸ Ω · cm, the toner charge amount distribution becomes broad and the toner charge amount tends to increase excessively. Further, when the charge amount of the toner is excessively increased, the image density of the formed image is likely to be lowered.

The volume resistivity of the magnetic powder particles is preferably 3.0 × 10 ⁵ Ω · cm or more and 4.5 × 10 ⁵ Ω · cm or less. When the volume resistivity value of the magnetic powder particles is within such a range, the charge amount distribution of the toner can be made sharper.

  The volume resistivity of the magnetic powder particles is changed, for example, by changing one or more of the shape of the magnetic powder particles, the Haywood diameter of the magnetic powder particles, the type of surface treatment agent for the magnetic powder particles, and the amount of addition of the surface treatment agent for the magnetic powder particles It can be adjusted by doing. The surface treatment agent for the magnetic powder particles will be described later.

  The volume resistivity value of the magnetic powder particles is measured, for example, by the following method. Magnetic powder (many magnetic powder particles) is put into a measurement cell of an electric resistance meter (“R6561” manufactured by Advantest Corporation). A load of 1 kg is applied to the magnetic powder in the measurement cell for 1 minute. Subsequently, a DC voltage of 10 V is applied to measure the electric resistance of the magnetic powder. From the measured electric resistance value and the size (thickness) of the magnetic powder particles at the time of measuring the electric resistance, the volume specific resistance value of the magnetic powder particles is calculated.

In the toner of this embodiment, the surface of the composite particle has negative chargeability. The triboelectric charge amount of the composite particles is −9 μC / g or less. Usually, a part of the metal contained in the magnetic powder particles is cationized in an aqueous solvent, so that the magnetic powder particles tend to be cationic. For example, when iron is contained in the magnetic powder particles, a part of the iron contained in the magnetic powder is eluted as iron ions (Fe ²⁺ or Fe ³⁺ ) in the aqueous medium, and the magnetic powder particles have a cationic property. There is a tendency to show. When a shell layer having a cationic group (for example, a thermosetting resin, more specifically, a melamine resin) is formed on a toner core having such magnetic powder particles on the surface, the shell layer is well formed. May not progress. A toner core having magnetic powder particles on the surface thereof, wherein the magnetic powder particles having a cationic property provided on the surface of the toner core and a shell layer forming material having a cationic group (for example, a thermosetting resin material) are electrically repelled. This is because the adhesion of the shell layer forming material to the toner and the in-situ polymerization of the shell layer forming material in the toner core provided with the magnetic powder particles on the surface are difficult to proceed. Here, in the toner of the present embodiment, the toner particles include composite particles having a toner core and magnetic powder particles provided on the surface of the toner core. The surface of the composite particle has negative chargeability, and the triboelectric charge amount of the composite particle is −9 μC / g or less. Such composite particles tend to exhibit moderate anionic properties in aqueous media. Therefore, the shell layer forming material having a cationic group is easily attracted electrically to the composite particles exhibiting anionic property. Therefore, adhesion of the shell layer forming material to the composite particles and in-situ polymerization of the shell layer forming material on the surface of the composite particles tend to proceed well. Thereby, it becomes easy to coat the composite particles with a shell layer having a uniform thickness. As a result, the heat resistant storage stability of the toner can be improved. In addition, since the magnetic powder particles are easily contained uniformly in the shell layer, it is easy to improve the charging stability of the toner.

  The triboelectric charge amount of the composite particles is preferably from −30 μC / g to −18 μC / g. When the triboelectric charge amount of the composite particles is within such a range, the toner charge amount distribution tends to be particularly sharp.

  The triboelectric charge amount of the composite particles is changed, for example, by changing one or more of the shape of the magnetic powder particles, the Haywood diameter of the magnetic powder particles, the type of the surface treatment agent for the magnetic powder particles, and the addition amount of the surface treatment agent for the magnetic powder particles It can be adjusted by doing.

  The triboelectric charge amount of the composite particles is measured, for example, by the following method. 100 parts by mass of standard carrier N-01 (standard carrier for negatively charged polar toner) provided by the Imaging Society of Japan and 7 parts by mass of composite particles were mixed with a mixing device ("Tabra (registered trademark) mixer" manufactured by WAB). For 30 minutes. The triboelectric charge amount of the composite particles contained in the obtained mixture is measured using a Q / m meter (for example, “MODEL 210HS-2A” manufactured by Trek).

  Examples of metals contained in magnetic powder particles include ferromagnetic metals, alloys of multiple types of ferromagnetic metals, metals doped with cobalt oxide or nickel in iron oxide, and ferromagnetic metals that do not contain ferromagnetic metal elements but are heat treated. Mention may be made of the alloy or chromium dioxide which will be shown. Examples of ferromagnetic metals include iron, cobalt or nickel. Iron may be used in the form of iron oxide (eg, triiron tetroxide or ferrite). Specifically, triiron tetroxide is magnetite. For the magnetic powder particles, one of these magnetic powder particles may be used alone or in combination of two or more. The magnetic powder particles preferably contain magnetite because it is easy to adjust the charge amount of the toner particles.

  The surface of the magnetic powder particles is preferably treated with a surface treatment agent. For example, the magnetic powder particles are preferably coated with a surface treatment agent. By treating the surface of the magnetic powder particles with the surface treatment agent, the surface of the composite particles can be adjusted to be negatively charged, and the triboelectric charge amount of the composite particles can be easily adjusted to −9 μC / g or less. In addition, by treating the surface of the magnetic powder particles with a surface treatment agent, it is possible to suppress cationization and elution of a part of the metal contained in the magnetic powder particles in the aqueous medium in the shell layer forming process described later. It is considered possible. As a result, the adhesion of the shell layer forming material to the composite particles and the in-situ polymerization of the shell layer forming material on the surface of the composite particles easily proceed.

  When the surface of the magnetic powder particles is treated with a surface treatment agent, the magnetic powder particles have a magnetic powder core and a coating layer. The coating layer is provided so as to cover the magnetic powder core. A magnetic powder core contains the metal contained in the above-mentioned magnetic powder particle. The coating layer contains a surface treatment agent or a hydrolyzate of the surface treatment agent.

  The coating layer should just be provided in at least one part of the surface of the magnetic powder core. In order to prevent a part of the metal contained in the magnetic powder particles from being cationized and eluted into the aqueous medium in the shell layer forming process described later, the coating layer is substantially formed on the surface of the magnetic powder core. It is preferable to be provided throughout. A part of the surface treatment agent contained in the coating layer may be chemically bonded to a group (for example, hydroxyl group) of the magnetic powder core or free water contained in the magnetic powder core.

  Examples of the surface treatment agent contained in the coating layer include a silicon compound or a phosphate compound. A surface treating agent may be used individually by 1 type, and may be used in combination of 2 or more type. The surface treatment agent is preferably a silicon compound because the triboelectric charge amount of the composite particles can be easily adjusted to −9 μC / g or less.

  Examples of silicon compounds include alkyltrialkoxysilanes, dialkyldialkoxysilanes, trialkylalkoxysilanes, aryltrialkoxysilanes, or silicate compounds.

  Examples of alkyltrialkoxysilanes include n-octyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, or An example is decyltrimethoxysilane.

  Examples of dialkyl dialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane or diethyldiethoxysilane.

  Examples of trialkylalkoxysilanes include trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, or triethylethoxysilane.

  Examples of aryltrialkoxysilanes include phenyltrimethoxysilane or phenyltriethoxysilane.

  Examples of silicic acid compounds include alkyl silicates, and more specifically, methyl silicate or ethyl silicate. When an alkyl silicate is used as the surface treatment agent, the alkyl silicate may be hydrolyzed on the surface of the magnetic powder particles to produce silica. Therefore, the coating layer of magnetic powder particles may contain silica which is a hydrolyzate of the surface treatment agent. The alkyl silicate is hydrolyzed, for example, by heating.

  As the surface treatment agent, alkyltrialkoxysilane or alkylsilicate is preferably used. When alkyltrialkoxysilane is used as the surface treatment agent, the coating layer of the magnetic powder particles contains alkyltrialkoxysilane. When an alkyl silicate is used as the surface treating agent, the coating layer of the magnetic powder particles contains silica that is a hydrolyzate of the alkyl silicate. By using alkyltrialkoxysilane or alkyl silicate as the surface treatment agent, the triboelectric charge amount of the composite particles can be easily adjusted to a desired value.

  More preferably, n-octyltriethoxysilane is used as the surface treating agent. In this case, the coating layer of magnetic powder particles contains n-octyltriethoxysilane. By using n-octyltriethoxysilane as the surface treatment agent, the image density of the formed image can be easily improved even when images are continuously formed.

  The content of the surface treatment agent is preferably 0.01 parts by mass or more and 2.00 parts by mass or less with respect to 100.00 parts by mass of the magnetic powder core. If the content of the surface treatment agent is within such a range, it is considered that negative chargeability can be imparted to the surface of the magnetic powder while maintaining the magnetism of the magnetic powder.

  The magnetic powder particles are preferably provided on the surface of the toner core so that the magnetic powder particles are in contact with the surface of the toner core or part of the magnetic powder particles are buried in the toner core. Since the magnetic powder particles are provided on the surface of the toner core so as not to be completely buried in the toner core, it becomes easy to adjust the electric resistance inside the shell layer, and it is easy to suppress the charge amount of the toner particles from being excessively increased. Further, the magnetic powder particles present in the shell layer become a starting point for breaking the shell layer at the time of fixing the toner, and it becomes easy to improve the fixing property of the toner.

<1-2. Toner core>
The toner core contains, for example, one or more of a binder resin, a colorant, and a release agent. However, unnecessary components (for example, a binder resin, a colorant, or a release agent) may be omitted depending on the use of the toner.

(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 core preferably contains a polyester resin as the binder resin. 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, 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. The glass transition point of the binder resin is preferably 30 ° C. or higher and 60 ° C. or lower. When the softening point and glass transition point of the binder resin are within such ranges, it is easy to improve the storage stability, form retention and durability of the toner while maintaining high toner fixability.

(Coloring agent)
The toner core may contain a black colorant as a colorant. Examples of the black colorant include black pigments and 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.

(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 mold release agents include aliphatic hydrocarbon waxes, oxides of aliphatic hydrocarbon waxes, vegetable waxes, animal waxes, mineral waxes, waxes based on fatty acid esters or part or all of fatty acid esters. An oxidized wax may be 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 waxes include candelilla wax, carnauba wax, wood wax, jojoba wax or rice wax. Examples of animal waxes include beeswax, lanolin or whale wax. Examples of mineral 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.

<2. Shell layer>
The composite particles are covered with a shell layer. When the composite particles are coated with the shell layer, the heat resistant storage stability of the toner tends to be improved. In addition, since the magnetic powder particles have low electric resistance, the magnetic particles in the composite particles tend to be charged to a desired value when the magnetic powder particles are covered with the shell layer. Furthermore, since the magnetic powder particles are highly hygroscopic, the magnetic powder particles in the composite particles are coated with a shell layer, so that they are formed even when an image is formed in a high temperature and high humidity environment. There is a tendency for the image density of the image to improve. In addition, the fluidity of the toner particles tends to be improved by coating the magnetic powder particles in the composite particles with the shell layer.

  The shell layer contains a thermosetting resin. The thermosetting resin contained in the shell layer is obtained by polymerizing or copolymerizing monomers of the thermosetting resin. When the shell layer contains a thermosetting resin, the shell layer is usually hardly broken even when heat and pressure are applied to the toner at the time of fixing the toner. However, in the toner of this embodiment, as already described, it is considered that when heat and pressure are applied to the toner at the time of fixing the toner, the magnetic powder particles existing inside the shell layer become a starting point for destroying the shell layer. Therefore, even when the shell layer contains a thermosetting resin, the low-temperature fixability of the toner can be improved.

  The thermosetting resin contained in the shell layer preferably has a cationic group. The thermosetting resin having a cationic group is obtained by polymerizing or copolymerizing a monomer of a thermosetting resin having a cationic group. Here, when an anionic resin (for example, a resin having an ester bond or a hydroxyl group) is used as the binder resin, the toner core has a strong tendency to exhibit anionic property in an aqueous medium. As already described, the surface of the composite particles (toner core and magnetic powder particles) has negative chargeability, and thus the composite particles exhibit an anionic property in an aqueous medium. Therefore, when the thermosetting resin monomer has a cationic group, when the shell layer forming step described later is performed using an aqueous medium, the monomer of the thermosetting resin exhibiting a cationic property is anionic. It becomes easy to attract to the surface of the composite particles (magnetic powder particles and toner core) shown. That is, the monomer of the thermosetting resin that is positively charged in the aqueous medium is easily attracted electrically to the composite particles (toner core and magnetic powder particles) that are negatively charged in the aqueous medium. And it becomes easy to form a shell layer uniformly on the surface of a composite particle by in-situ polymerization, for example. As a result, as described above, the charge amount of the toner particles can be made uniform, and the charge amount distribution of the toner can be sharpened. Further, even when images are continuously formed using toner, it is possible to suppress the toner charge amount from being excessively increased (charged up), and to suppress a decrease in image density of the formed image. be able to.

  As an example of the cationic group which a thermosetting resin has, a nitrogen-containing group (for example, -NH- or -N =) is mentioned. Examples of the thermosetting resin having a cationic group include a nitrogen-containing thermosetting resin. Examples of the nitrogen-containing thermosetting resin include melamine resin, urea resin, and glyoxal resin, and melamine resin is preferable.

  Melamine resin is a polycondensate of melamine and formaldehyde. The monomers used to form the melamine resin are melamine and formaldehyde. Urea resin is a polycondensate of urea and formaldehyde. The monomers used to form the urea resin are urea and formaldehyde. Glyoxal resin is a polycondensate of a reaction product of glyoxal and urea with formaldehyde. The monomers used in the formation of the glioxal resin are the reaction product of glyoxal and urea and formaldehyde.

  A shell layer may be formed using a prepolymer of a thermosetting resin. For example, a reaction product of melamine, urea or glyoxal and urea may be used in the form of a prepolymer (hereinafter sometimes referred to as an initial polymer). Here, the prepolymer means an intermediate product obtained by stopping the monomer polycondensation reaction at a stage before the polymerization degree reaches the polymerization degree of the polymer.

  The shell layer may be formed using a derivatized thermosetting resin monomer. For example, urea reacted with melamine, urea and glyoxal may have undergone known modification. For example, the monomer of the thermosetting resin may be methylolated with formaldehyde before reacting with the thermoplastic resin.

  The aforementioned thermosetting resin monomers, thermosetting resin prepolymers and derivatized thermosetting resin monomers are sometimes collectively referred to as “thermosetting resin materials”. The material of the thermosetting resin preferably has a cationic group, and more preferably has a nitrogen-containing group (for example, -NH- or -N =). When the thermosetting resin material has a cationic group, the thermosetting resin material that is positively charged in the aqueous medium is a composite particle that is negatively charged in the aqueous medium (toner core and magnetic powder). Particles) are easily attracted electrically. And it becomes easy to advance in-situ polymerization of the material of the thermosetting resin on the surface of the composite particle.

  The material of the thermosetting resin preferably has a functional group capable of reacting with the functional group of the binder resin contained in the toner core in the composite particle. For example, when the binder resin is a polyester resin, the material of the thermosetting resin preferably has a hydroxyl group that can react with a hydroxyl group and a carboxyl group that the polyester resin has. Hereinafter, with reference to FIG.2 and FIG.3, reaction with the composite particle 5 and the material of a thermosetting resin is demonstrated. In order to facilitate understanding, in FIGS. 2 and 3, the binder resin contained in the toner core 2 in the composite particle 5 is a polyester resin, and the thermosetting resin material has a hydroxyl group and is formed. A case where the thermosetting resin is a melamine resin will be described as an example.

  As shown in FIG. 2, the composite particle 5 includes a toner core 2 and a plurality of magnetic powder particles 3 provided on the surface of the toner core 2. The toner core 2 contains a polyester resin as a binder resin. Therefore, the hydroxyl group of the polyester resin and the hydroxyl group of the carboxyl group of the polyester resin are exposed on the surface of the toner core 2. The compound shown in FIG. 2 is methylol melamine as a material for the thermosetting resin. Methylolmelamine has a hydroxyl group. The shell layer 4 (see FIG. 1) is formed by polymerization or copolymerization of the thermosetting resin material. It is considered that the following reaction proceeds when the shell layer 4 is formed together with the polymerization or copolymerization of the material of the thermosetting resin. Specifically, the hydroxyl group exposed on the surface of the toner core 2 undergoes dehydration condensation with the hydroxyl group of methylolmelamine to form an ether bond. Further, the hydroxyl group of the carboxyl group exposed on the surface of the toner core 2 reacts with the hydroxyl group of methylolmelamine to form an ester bond. As a result, it is considered that the composite particles 5 having the toner core 2 and the shell layer 4 are firmly bonded.

  It is considered that the bond between the composite particle 5 having the toner core 2 and the shell layer 4 is formed even when the polymerization reaction of the thermosetting resin material proceeds to some extent. The compound shown in FIG. 3 is a part of a melamine resin obtained by polymerization of methylol melamine as a thermosetting resin material. As shown in FIG. 3, even when the polymerization reaction proceeds to some extent, the hydroxyl group at the end of the generated melamine resin undergoes dehydration condensation with the hydroxyl group exposed on the surface of the toner core 2 to form an ether bond. Conceivable. In addition, it is considered that the hydroxyl group at the end of the generated melamine resin reacts with the hydroxyl group of the carboxyl group exposed on the surface of the toner core 2 to form an ester bond. As a result, it is considered that the composite particles 5 having the toner core 2 and the shell layer 4 are firmly bonded. The reaction between the composite particles 5 and the thermosetting resin material has been described above with reference to FIGS. 2 and 3.

<3. External additive>
An external additive may be attached to the surface of the composite particle coated with the shell layer, if necessary. The particles before the external additive is adhered (composite particles coated with a shell layer) may be referred to as toner base particles.

  Examples of the external additive include metal oxides (for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate or barium titanate), silicon carbide or silica. Specific examples of the silica include colloidal silica and hydrophobic silica. The external additive may be surface-treated with a surface treatment agent (for example, aminosilane, silicone oil, hexamethyldisilazane, titanate coupling agent or silane coupling agent) as necessary.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.00 μm or less. The content of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner base particles.

<4. Two-component developer>
The toner may be mixed with a desired carrier and used in a two-component developer. When preparing a two-component developer, it is preferable to use a magnetic carrier. The toner may be used in a one-component developer.

  An example of the carrier is a carrier core coated with a resin. The carrier core is formed by magnetic particles. Another example of the carrier is a resin carrier in which magnetic particles are dispersed in a resin.

  Specific examples of magnetic particles include iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, or cobalt particles; alloys of these materials with metals such as manganese, zinc, or aluminum. Particles; iron-nickel alloy particles; iron-cobalt alloy particles; ceramic particles; or high dielectric constant material particles. Examples of ceramics used as ceramic particles include titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, Examples include lead zirconate or lithium niobate. Examples of the high dielectric constant material used as the particles of the high dielectric constant material include ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt.

  Examples of the resin covering the carrier core and the resin contained in the resin carrier include acrylic acid polymers, styrene polymers, styrene-acrylic acid copolymers, olefin polymers (eg, polyethylene, chlorinated polyethylene). Or polypropylene), polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, urethane resin, epoxy resin, silicone resin, fluororesin (eg, polytetrafluoroethylene, polychlorotri Fluoroethylene or polyvinylidene fluoride), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin or amino resin. One of these resins may be used alone, or two or more thereof may be used in combination.

  The particle diameter of the carrier is preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less. The particle diameter of the carrier is measured by, for example, an electron microscope.

  When the toner is used in the two-component developer, the toner content is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to the mass of the two-component developer. It is preferable.

<5. Production of toner>
The toner manufacturing method of this embodiment includes a composite particle forming step and a shell layer forming step. The toner manufacturing method may include one or more of a magnetic powder forming step, a toner core forming step, a washing step, a drying step, and an external addition step as necessary. Hereinafter, an example of a toner manufacturing method will be described.

<5-1. Magnetic powder formation process>
The magnetic powder forming step includes a surface treatment step. The magnetic powder forming step may include a magnetic powder core forming step as necessary.

(Magnetic powder core forming process)
In the step of forming the magnetic powder core, an aqueous metal solution is heated under basic conditions. Air is bubbled through the heated aqueous metal solution. This oxidizes the metal. Grind the oxidized metal. As a result, a magnetic powder core is obtained.

  When the aqueous metal solution is heated, the pH of the aqueous metal solution is preferably adjusted to 12.0 or more and 13.0 or less using a basic substance. The heating temperature of the aqueous metal solution is preferably 70 ° C. or higher and 100 ° C. or lower. The speed of the air that is passed through the metal aqueous solution is preferably 50 L / min or more and 200 L / min or less. The time for aeration of the metal aqueous solution is preferably 30 minutes or more and 600 minutes or less, and more preferably 200 minutes or more and 250 minutes or less. The oxidized metal is pulverized using, for example, a pulverizer (for example, “Hammer Mill (HM-5)” manufactured by Nara Machinery Co., Ltd.).

  If necessary, one or more operations of washing, filtration, and drying may be performed on the obtained magnetic powder core.

(Surface treatment process)
In the surface treatment step, the surface of the magnetic powder core is treated with a surface treatment agent. Thereby, magnetic powder particles are obtained. The magnetic powder particles obtained in the surface treatment step have a magnetic powder core and a coating layer that covers the magnetic powder core. The formed coating layer contains a surface treatment agent or a hydrolyzate of the surface treatment agent.

  When the surface treatment agent is an alkyltrialkoxysilane, a dialkyldialkoxysilane, a trialkylalkoxysilane, or an aryltrialkoxysilane, the treatment with the surface treatment agent is performed by, for example, mixing a surface treatment agent and a magnetic powder core (specifically, Is carried out by mixing using a wheel-type kneader. The mixing time is preferably 5 minutes or more and 5 hours or less, and more preferably 30 minutes or more and 2 hours or less.

  When the surface treatment agent is a silicate compound, the treatment with the surface treatment agent is performed by immersing the magnetic powder core in the surface treatment agent (for example, a liquid silicate compound). Next, the immersion time is preferably 0.1 seconds or more and 30 minutes or less on the surface of the obtained magnetic powder core using a surface treatment agent. The temperature for immersion is, for example, 0 ° C. or more and 50 ° C. or less.

  The magnetic powder core immersed in the surface treatment agent may be heated as necessary. The heating temperature is preferably 100 ° C. or higher and 300 ° C. or lower. Heating may be performed under reduced pressure.

<5-2. Toner core formation process>
The toner core is formed by, for example, an aggregation method or a pulverization method.

  When the toner core is formed by an aggregation method, the toner core formation process includes, for example, an aggregation process and a coalescence process. In the aggregation step, the fine particles containing the components constituting the toner are aggregated in an aqueous medium to form aggregated particles. In the coalescence process, the components contained in the aggregated particles are coalesced in an aqueous medium to form a toner core. According to the aggregation method, it is easy to obtain a toner core having a uniform shape and a uniform particle diameter.

  When the toner core is formed by a pulverization method, the toner core formation step includes, for example, a mixing step, a kneading step, a pulverizing step, and a classification step. In the mixing step, the binder resin, the colorant, and the release agent are mixed to obtain a mixture. In the kneading step, the obtained mixture is melted and kneaded to obtain a kneaded product. In the pulverization step, the obtained kneaded product is pulverized to obtain a pulverized product. In the classification step, the obtained pulverized product is classified to obtain a toner core. According to the pulverization method, the toner core can be prepared relatively easily. In addition, in the shell layer forming process described later, the toner core that has been slightly softened by heating contracts due to surface tension, and thus the toner core tends to be spherical. Therefore, even when the toner core is manufactured by a pulverization method, it is easy to improve the average circularity of the toner particles.

<5-3. Complex Particle Formation Step>
In the composite particle forming step, a plurality of magnetic powder particles are adhered to the surface of the toner core. Thereby, the composite particle is formed. It is preferable to mechanically attach a plurality of magnetic powder particles to the surface of the toner core. Examples of the method for attaching the magnetic powder particles to the surface of the toner core include a method of mixing the toner core and the magnetic powder particles using a mixer (for example, FM mixer or Nauter mixer (registered trademark)). The mixing conditions are preferably set so that the magnetic powder particles are not completely buried in the surface of the toner core.

  The amount of magnetic powder particles added in the composite particle forming step is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core. Further, the surface of the composite particle obtained in the composite particle forming step has negative chargeability. The triboelectric charge amount of the composite particles obtained in the composite particle forming step is −9 μC / g or less.

<5-4. Shell layer formation process>
In the shell layer forming step, a thermosetting resin material is polymerized or copolymerized on the surface of the composite particle. Thereby, a shell layer is formed so as to cover the composite particles. As a result, toner base particles are obtained.

  When forming the shell layer, it is preferable to prevent dissolution of the binder resin and elution of components (for example, a release agent) contained in the toner core in the solvent used for forming the shell layer. For this reason, the shell layer is preferably formed in an aqueous medium.

  The aqueous medium is a medium mainly composed of water. The aqueous medium may function as a solvent or may function as a dispersion medium. Specific examples of the aqueous medium include water or a mixed liquid of water and a polar solvent. Examples of the polar solvent contained in the aqueous medium include methanol or ethanol. The content of water in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, based on the mass of the aqueous medium. Most preferably, it is mass%.

  The shell layer is formed, for example, by adding composite particles to an aqueous medium containing a thermosetting resin material. After the composite particles are added to the aqueous medium, the composite particles are dispersed in the aqueous medium.

  Examples of the dispersion method include a method in which the composite particles are mechanically dispersed in an aqueous medium using an apparatus that strongly stirs the dispersion. As a device for vigorously stirring the dispersion, for example, a mixing device (for example, “Hibismix (registered trademark)” manufactured by Primics Co., Ltd.) is used.

  It is preferable to adjust the pH of the aqueous medium to about 4 using an acidic substance before adding the composite particles to the aqueous medium containing the thermosetting resin material. By adjusting the pH of the aqueous medium to the acidic side, the polycondensation reaction of the thermosetting resin material is facilitated. The composite particles preferably exhibit anionic property in an aqueous medium having a pH of 4. Thereby, it is thought that it can suppress that a part of metal contained in the magnetic powder particle in a composite particle ionizes and elutes in the aqueous medium of pH4. As a result, it becomes easy to form a uniform shell layer on the composite particles.

  After adjusting the pH of the aqueous medium as necessary, the thermosetting resin material and the composite particles are mixed in the aqueous medium. Thereby, an aqueous dispersion of composite particles is obtained. In the obtained aqueous dispersion, the polymerization reaction of the thermosetting resin material proceeds on the surface of the composite particles.

  The temperature of the aqueous medium when forming the shell layer is preferably 40 ° C. or higher and 95 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. If the shell layer is formed at a temperature within such a range, the formation of the shell layer is likely to proceed.

  The temperature at which the shell layer is formed on the surface of the composite particle is preferably 40 ° C. or higher and 95 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. By forming the shell layer at a temperature within such a range, the formation of the shell layer proceeds well.

  By forming a shell layer so as to cover the composite particles, an aqueous dispersion containing toner base particles can be obtained. The aqueous dispersion containing the toner base particles is cooled to room temperature. Thereafter, one or more steps selected from a toner mother particle cleaning step, a drying step, and an external addition step, which will be described later, are performed as necessary. As a result, a toner containing toner particles is obtained.

<5-5. Cleaning process>
The toner base particles are washed with water as necessary. As an example of the washing method, there is a method in which a wet cake of toner mother particles is recovered from an aqueous dispersion containing toner mother particles by solid-liquid separation (for example, filtration), and the resulting wet cake is washed with water. Can be mentioned. As another example of the washing method, there is a method in which the toner base particles in the dispersion liquid are settled, the supernatant liquid is replaced with water, and the toner base particles are redispersed in water after the replacement.

<5-6. Drying process>
The toner base particles may be dried as necessary. Examples of the method for drying the toner base particles include a method using a dryer. Examples of the dryer include a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, and a vacuum dryer. In order to suppress aggregation of toner base particles during drying, a method using a spray dryer is preferable. In the case of using a spray dryer, by spraying a dispersion of an external additive such as silica together with a dispersion of the toner base particles, the external additive adheres to the surface of the toner base particles simultaneously with the drying of the toner base particles. May be.

<5-7. External process>
An external additive may be attached to the surface of the toner base particles as necessary. As a method for attaching the external additive to the surface of the toner base particles, for example, a mixer (for example, FM mixer and Nauter mixer (registered trademark)) under the condition that the external additive is not buried in the surface of the toner base particles. And a method of mixing toner base particles and an external additive.

  The toner manufacturing method may be arbitrarily changed according to the required toner characteristics. Further, unnecessary operations and processes may be omitted. When omitting the external addition step, the toner base particles correspond to the toner particles.

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

<1. Production of magnetic powder>
First, magnetic powders (powder composed of a large number of magnetic powder particles) A to M shown in Table 1 were produced.

(Manufacture of magnetic powder A)
First, a magnetic powder core was formed. Specifically, 20 L of ferrous sulfate containing iron ions (Fe ²⁺ ) at a concentration of 1.5 mol / L and 20 L of a 3.40N aqueous sodium hydroxide solution were mixed. The temperature of the mixed solution was raised to 90 ° C. to obtain an aqueous ferrous salt solution containing iron hydroxide (Fe (OH) ₂ ) having a pH of 12.5. The temperature of the obtained aqueous solution was set to 90 ° C., and air was bubbled through the aqueous solution at a rate of 100 L / min for 220 minutes. As a result, iron hydroxide was oxidized to obtain magnetic powder (magnetite). The obtained magnetic powder was washed with water, filtered, and dried. The dried magnetic powder was pulverized using a pulverizer (“Hammer Mill (HM-5)” manufactured by Nara Machinery Co., Ltd.) to obtain a magnetic powder core for octahedral magnetic powder A.

  Next, the obtained magnetic powder core was surface-treated using a surface treatment agent. N-octyltriethoxysilane ("A-137" manufactured by Momentive Performance Materials) was used as the surface treatment agent. 10 kg of the magnetic powder core and 15 g of the surface treatment agent were mixed for 1 hour using a wheel-type kneader (“Sand Mill” manufactured by Matsumoto Casting Iron Co., Ltd.). Thus, the magnetic powder core was coated with the surface treatment agent. As a result, a coating layer was formed so as to cover the magnetic powder core, and the coating layer contained n-octyltriethoxysilane as a surface treatment agent. Thereby, magnetic powder A was obtained. Magnetic powder A was octahedral.

(Production of magnetic powders B to E, H, I, K and L)
Each of the magnetic powders B to E, H, I, K, and L was manufactured by the same method as the manufacturing of the magnetic powder A except that the following points were changed. In the oxidation reaction of iron hydroxide, the growth conditions of the iron hydroxide particles (for example, the temperature of the ferrous salt aqueous solution and the speed and time for allowing air to pass through the aqueous ferrous salt solution) were appropriately changed. As a result, the average haywood diameter (0.300 μm) of the magnetic powder A was changed to the average haywood diameters of the magnetic powders B to E, H, I, K, and L shown in Table 1. By changing the average Haywood diameter of the magnetic powder to the value shown in Table 1 and appropriately changing the addition amount of the surface treatment agent (n-octyltriethoxysilane), the volume resistivity (4 × 10 ⁵ Ω / cm) and the triboelectric charge amount (−21 μC / g), the volume resistivity values and triboelectric charge amounts of magnetic powders B to E, H, I, K and L shown in Table 1 were changed.

(Manufacture of magnetic powder F)
The magnetic powder F was manufactured by the same method as the manufacture of the magnetic powder A except that the following points were changed. The shape of the magnetic powder was changed from the octahedron of magnetic powder A to the hexahedron of magnetic powder F by appropriately changing the pH of the ferrous salt aqueous solution from 12.5 in the production of magnetic powder A. By changing the shape of the magnetic powder to hexahedron and appropriately changing the addition amount of the surface treatment agent (n-octyltriethoxysilane), the volume resistivity of the magnetic powder A (4 × 10 ⁵ Ω / cm) In addition, the volume resistivity value and the friction charge amount of the magnetic powder F shown in Table 1 were changed from the friction charge amount (−21 μC / g).

(Manufacture of magnetic powder G)
First, a magnetic powder core was formed. A magnetic powder core for octahedral magnetic powder G was obtained in the same manner as in the production of magnetic powder core for magnetic powder A. Next, the obtained magnetic powder core was surface-treated using a surface treatment agent. An ethyl silicate solution (concentration 100%) was used as a surface treatment agent. 10 kg of the magnetic powder core was immersed in 20 L of ethyl silicate solution for 5 minutes. After immersion, the magnetic powder core was taken out from the ethyl silicate solution. The magnetic powder core taken out was heated at 230 ° C. for 30 minutes under reduced pressure. As a result, a silica film was formed on the surface of the magnetic powder core. That is, a coating layer (silica film) was formed so as to cover the magnetic powder core, and the coating layer contained silica (SiO ₂ ) which is a hydrolyzate of the surface treatment agent. Thereby, magnetic powder G was obtained. The magnetic powder G had an octahedral shape.

(Manufacture of magnetic powder J)
First, a magnetic powder core was formed. 1.8 L of ferrous sulfate containing iron ions (Fe ²⁺ ) at a concentration of 1.8 mol / L was mixed with 2.8 L of a 1.346N aqueous sodium hydroxide solution. The temperature of the mixed solution was raised to 90 ° C. to obtain a ferrous salt aqueous solution containing iron hydroxide (Fe (OH) ₂ ). The obtained aqueous solution was aerated with air at a rate of 15 L / min for 180 minutes under the conditions of an aqueous solution temperature of 90 ° C. and pH 6.8. When the pH of the aqueous solution started to drop to 6.0, 4 L of 4N aqueous sodium hydroxide solution was added to the aqueous solution. This adjusted the pH of the aqueous solution to 12.0. Air was bubbled through the aqueous solution for 60 minutes at a rate of 15 L / min under conditions of an aqueous solution temperature of 90 ° C. and a pH of 12.0. As a result, iron hydroxide was oxidized to obtain magnetic powder (magnetite). The obtained magnetic powder was washed with water, filtered, and dried. By pulverizing the dried magnetic powder, a magnetic powder core for spherical magnetic powder J was obtained.

  Next, the obtained magnetic powder core was surface-treated using a surface treatment agent. N-octyltriethoxysilane ("A-137" manufactured by Momentive Performance Materials) was used as the surface treatment agent. 10 kg of the magnetic powder core and 15 g of the surface treatment agent were mixed for 1 hour using a wheel-type kneader (“Sand Mill” manufactured by Matsumoto Casting Iron Co., Ltd.). Thus, the magnetic powder core was coated with the surface treatment agent. As a result, a coating layer was formed so as to cover the magnetic powder core, and the coating layer contained n-octyltriethoxysilane as a surface treatment agent. Thereby, magnetic powder J was obtained. The magnetic powder J was spherical.

(Manufacture of magnetic powder M)
First, a magnetic powder core was formed. A magnetic powder core for octahedral magnetic powder M was obtained in the same manner as the production of magnetic powder core for magnetic powder A. Next, the obtained magnetic powder core was surface-treated using a surface treatment agent. 3-Aminopropyltriethoxysilane was used as a surface treatment agent. 10 kg of the magnetic powder core and 15 g of the surface treatment agent were mixed for 1 hour using a wheel-type kneader (“Sand Mill” manufactured by Matsumoto Casting Iron Co., Ltd.). Thus, the magnetic powder core was coated with the surface treatment agent. As a result, a coating layer was formed so as to cover the magnetic powder core, and the coating layer contained 3-aminopropyltriethoxysilane as a surface treatment agent. Thereby, magnetic powder M was obtained. The magnetic powder M was octahedral.

<2. Measurement of physical properties of magnetic powder>
For each of the obtained magnetic powders A to M, the shape, average Haywood diameter, volume specific resistance value, and triboelectric charge amount were measured by the following methods. The measurement results are shown in Table 1. In Table 1, the measurement target of the shape, the average Haywood diameter and the volume resistivity is magnetic powder. In Table 1, the target of measurement of the triboelectric charge amount is the composite particles after the composite particle forming process described later and before the shell layer forming process.

(Measurement of shape and average Haywood diameter)
Using a scanning electron microscope (SEM, “JSM-880” manufactured by JEOL Ltd.), the measurement sample (magnetic powder) was observed at an observation magnification of 50,000 times. 300 magnetic powder particles contained in the measurement sample were randomly selected, and an SEM photograph of each magnetic powder particle was taken. The shape of the magnetic powder particles was confirmed from the obtained SEM photograph. In addition, the SEM photograph was subjected to image analysis using an image analyzer, thereby measuring the Haywood diameter of 300 magnetic powder particles. The sum of all measured Haywood diameters was divided by the number of measured magnetic powder particles (300). Thereby, the average Haywood diameter (number average Haywood diameter) of the magnetic powder particles was calculated.

(Measurement of volume resistivity)
A measurement sample (magnetic powder) 5 g was placed in a measurement cell of an electric resistance meter (“R6561” manufactured by Advantest Corporation). Electrode resistance electrodes were connected to the upper and lower portions of the measurement cell, respectively. A load of 1 kg was applied to the measurement sample in the measurement cell for 1 minute. Subsequently, a DC voltage of 10 V was applied to the electrode, and the electrical resistance of the measurement sample was measured. And based on the value of the measured electrical resistance and the dimension (thickness) of the measurement sample at the time of electrical resistance measurement, the volume specific resistance value of the measurement sample was obtained. The volume resistivity value was measured in an environment at a temperature of 20 ° C. and a humidity of 50% RH.

(Measurement of triboelectric charge)
100 parts by mass of a standard carrier N-01 (standard carrier for negatively charged polar toner) provided by the Imaging Society of Japan and 7 parts by mass of a measurement sample (composite particles after a composite particle forming step and a shell layer forming step described later) Were mixed for 30 minutes using a mixing device ("Tabra (registered trademark) mixer" manufactured by WAB). The triboelectric charge amount of the measurement sample in the obtained mixture was measured using a Q / m meter (for example, “MODEL 210HS-2A” manufactured by Trek).

<3. Production of Toner A-1>
Toner A-1 was produced by the following method.

(Toner core formation process)
The following binder resin, colorant and release agent were used as the raw material for the toner core.
Binder resin: Polyester resin ("Polyester (registered trademark) HP-313" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Colorant: Carbon black ("MA-100" manufactured by Mitsubishi Chemical Corporation)
Mold release agent: Ester wax (“Nissan Electol (registered trademark) WEP-4” manufactured by NOF Corporation)

90 parts by mass of the binder resin, 3 parts by mass of the colorant and 7 parts by mass of the release agent were stirred using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.) to obtain a mixture. The mixture was kneaded while melting using a twin-screw extruder (“TEM-26SS” manufactured by Toshiba Machine Co., Ltd.). The obtained melt-kneaded material was coarsely pulverized using a pulverizer (“Rotoplex (registered trademark) 16/8 type” manufactured by Hosokawa Micron Corporation). The particle size of the coarsely pulverized product obtained was about 2 mm. The coarsely pulverized product was pulverized by a pulverizer (“Turbomill RS type” manufactured by Freund Turbo). The obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core was obtained. The resulting toner core had a volume median diameter D ₅₀ of 7.0 μm.

(Composite particle formation process)
100.00 parts by mass of the toner core and 2.00 parts by mass of the magnetic powder A were mixed for 5 minutes at a rotational speed of 5000 rpm using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.). As a result, magnetic powder was adhered to the surface of the toner core. As a result, composite particles were obtained.

(Shell layer forming process)
300 mL of ion-exchanged water was put into a 1 L three-necked flask equipped with a thermometer and a stirring blade. The internal temperature of the flask was kept at 30 ° C. using a water bath (Aswan Co., Ltd. “IWB-250 type”). Next, dilute hydrochloric acid was added to the flask to adjust the pH of the liquid in the flask to 4. After pH adjustment, 2 mL of water-soluble methylol melamine (“Nikaresin (registered trademark) S-260” manufactured by Nippon Carbide Industries, Ltd.), which is a material of thermosetting resin, was added to the flask. Next, the contents of the flask were stirred, and the thermosetting resin material was dissolved in ion-exchanged water. As a result, an aqueous solution of a thermosetting resin material was obtained.

  300 g of composite particles were added to the aqueous solution of the obtained thermosetting resin material. The contents of the flask were stirred for 1 hour at a speed of 200 rpm. Next, 300 mL of ion exchange water was added to the flask. Thereafter, the temperature inside the flask was increased to 70 ° C. at a rate of 1 ° C./min while stirring the contents of the flask at a rate of 100 rpm. After the temperature increase, the contents of the flask were stirred for 2 hours under the conditions of a flask internal temperature of 70 ° C. and a speed of 100 rpm. Thereafter, sodium hydroxide was added to the flask to adjust the pH of the contents of the flask to 7. The flask contents were then cooled to room temperature. As a result, a shell layer of melamine resin was formed so as to cover the composite particles. As a result, a dispersion of toner base particles was obtained.

(Washing process)
The obtained dispersion of toner base particles was filtered with a Buchner funnel to obtain a wet cake of toner base particles. Next, the toner base particle wet cake was dispersed in ion-exchanged water, and the toner base particles contained in the dispersion were filtered. As a result, the toner base particles were washed. The washing operation of the toner base particles with ion exchange water was repeated 5 times in the same manner. As a result, a wet cake of toner base particles after washing was obtained.

(Drying process)
The wet cake of toner mother particles after washing was dispersed in an aqueous ethanol solution having a concentration of 50% by mass to prepare a slurry. The obtained slurry was supplied to a continuous surface reformer (“Coatmizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.) to dry the toner base particles in the slurry. Drying with a coatmizer (registered trademark) was performed under conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min.

(External addition process)
100.0 parts by mass of dried toner base particles, positively-charged silica particles as external additives (“CAB-O-SIL (registered trademark) TG-308F” manufactured by Cabot Corporation), fumed with a hydrophobic treated surface Silica particles) 1.5 parts by mass and 1.0 part by mass of titanium oxide particles (“MT-500B” manufactured by Teika Co., Ltd.) as an external additive were mixed with FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.). Was mixed for 5 minutes at a rotational speed of 3500 rpm. As a result, the external additive was adhered to the surface of the toner base particles. As a result, Toner A-1 was obtained.

<4. Production of Toners A-2 to A-9 and B-1 to B-9>
Toners A-2 to A-9 and B-1 to B-9 were produced in the same manner as in the production of the toner A-1, except that the following points were changed. The kind of magnetic powder used in the composite particle forming step was changed from the magnetic powder A in the production of the toner A-1 to the kind of magnetic powder shown in Table 2. The addition amount of the magnetic powder in the composite particle forming step was changed from 2.00 parts by mass in the production of the toner A-1 to the addition amount (content) shown in Table 2.

<5. Production of carriers>
A carrier for use in evaluation of charge amount distribution, charge amount, image density, low-temperature fixability and high-temperature offset resistance described later was produced. Specifically, ferrite particles (“F51-50” manufactured by Powdertech Co., Ltd., particle diameter 50 μm) were used as the carrier core. 2 kg of an epoxy resin (“jER (registered trademark) 1004” manufactured by Mitsubishi Chemical Corporation) was dissolved in 20 L of acetone. To the obtained solution, 100 g of diethylenetriamine and 150 g of phthalic anhydride were added and mixed. The obtained mixed liquid was sprayed onto 10 kg of the carrier core while feeding hot air at 80 ° C. using a fluidized bed coating apparatus (“Spiraflow (registered trademark) SFC-5” manufactured by Freund Sangyo Co., Ltd.). As a result, the carrier core was coated with an uncured organic layer (fluidized bed). The carrier core covered with the uncured organic layer (fluidized bed) was heated at 180 ° C. for 1 hour using a dryer. Thereby, the fluidized bed was hardened. Thereby, carrier particles (carrier) having a carrier core and a resin layer (coat layer) covering the carrier core were obtained.

<6. Evaluation of charge distribution>
5 g of toner (any one of toners A-1 to A-9 and B-1 to B-9) and 10 g of the carrier produced as described above were placed in a 20 mL capacity plastic container. Using a ball mill, the contents of the container were stirred for 10 minutes at a rotation speed of 100 rpm to obtain a mixture. The obtained mixture was passed through a measurement unit of a charge amount / particle size distribution measuring device (“Espert Analyzer EST-3” manufactured by Hosokawa Micron Corporation). For the 3000 toner particles contained in the mixture passing through the measurement unit, the charge amount Q and the particle diameter d of each toner particle were measured using a laser Doppler method. From the measured charge amount Q and particle diameter d of each toner particle, the charge amount per particle diameter (Q / d) was calculated for each toner particle. The charge amount per particle diameter (Q / d) is plotted on the horizontal axis, and the number of toner particles having the charge amount (Q / d) corresponding to the vertical axis is plotted. Thereby, a charge amount distribution curve was obtained. From the obtained charge amount distribution curve, a frequency width of 1/4 of the mode value of the toner charge amount distribution was obtained. Hereinafter, the width of the quarter of the mode value of the toner charge amount distribution may be referred to as “Q / d distribution width”. The unit of the Q / d distribution width is “femtC / μm”. The smaller the toner Q / d distribution width, the sharper the toner charge amount distribution. A toner having a Q / d distribution width of less than 0.80 femt C / μm was considered acceptable.

<7. Production of two-component developer>
9 parts by mass of the toner and 100 parts by mass of the carrier produced as described above were mixed for 30 minutes using a ball mill to obtain a two-component developer. The obtained two-component developer was used for evaluation of the following charge amount, image density (ID), low temperature fixability and high temperature offset resistance.

<8. Evaluation of charge amount and image density>
Using the obtained two-component developer, the toner charge amount and image density were evaluated by the following methods. These evaluations were performed in an environment of a temperature of 20 ° C. and a humidity of 50% RH (relative humidity).

First, an image was formed on paper using the obtained two-component developer and an evaluation machine. Specifically, a color printer FS-C5016 (manufactured by Kyocera Document Solutions Co., Ltd.) was used as an evaluation machine. As the paper, an evaluation paper (“ColorCopy (registered trademark)” manufactured by Mondi, A4 size, 90 g / m ² ) was used. 150 g of the two-component developer was put into a black developing device. Further, a replenishing toner was put into a black toner container.

(Initial image density and charge amount)
Next, an image I was formed on one sheet using a two-component developer and an evaluation machine. The image I included a pattern image portion (printing rate 8%), a solid image portion (size 20 mm × 30 mm), and a blank paper image portion. The formed image was used as an initial image density evaluation sample. The image density (initial image density) of the solid image portion in the initial image density evaluation sample was measured using a reflection densitometer (“RD914” manufactured by X-Rite). Table 2 shows the measured initial image density. A toner having an initial image density of 1.20 or more was considered acceptable.

  The charge amount (initial charge amount) of the toner after the image I was formed on one sheet of paper was measured using a suction type small charge amount measuring device (“MODEL 212HS” manufactured by Trek). Specifically, after forming the image I on one sheet, the two-component developer was taken out from the developing device. 0.10 g of the two-component developer taken out was put into a measuring cell of a measuring device. Only the toner out of the charged two-component developer was sucked through a sieve for 10 seconds. The total electricity and mass of the sucked toner were measured using a measuring device. Then, the charge amount (μC / g) of the toner in the two-component developer was calculated from the formula “total electric amount of sucked toner (μC) / mass of sucked toner (g)”. Table 2 shows the calculated initial charge amount (μC / g) of the toner. A toner having an initial charge amount of 20 μC / g or more and less than 30 μC / g was determined to be acceptable.

(Image density and charge amount after printing 30,000 sheets)
Subsequently, an image I was continuously formed on 30,000 sheets using a two-component developer and an evaluation machine. The image formed on the 30,000th sheet was used as an image density evaluation sample after printing 30,000 sheets. The image density (image density after printing 30,000 sheets) in the sample for evaluation of image density after printing 30,000 sheets was measured using a reflection densitometer (“RD914” manufactured by X-Rite). Table 2 shows the measured image density after printing 30,000 sheets. A toner having an image density of 1.20 or more after printing 30,000 sheets was regarded as acceptable.

  The charge amount of the toner after forming the image I on 30,000 sheets (charge amount after printing 30,000 sheets) was measured by the same method as the measurement of the initial charge amount. Table 2 shows the charge amount (μC / g) of the obtained toner after printing 30,000 sheets. A toner having a charge amount after printing 30,000 sheets of 20 μC / g or more and less than 30 μC / g was regarded as acceptable.

<9. Evaluation of low-temperature fixability>
Using the prepared two-component developer, an image was formed on a sheet by an evaluation machine and a fixing jig. As an evaluation machine, an evaluation machine with the fixing device removed from a color printer FS-C5016 (manufactured by Kyocera Document Solutions Co., Ltd.) was used. Evaluation paper (“ColorCopy (registered trademark)” manufactured by Mondi, A4 size, 90 g / m ² ) was used as the paper. The prepared two-component developer was put into a black developing device of an evaluation machine. The replenishing toner was put into the black toner container of the evaluation machine.

Using an evaluation machine, a solid image (unfixed image) having a size of 20 mm × 30 mm was formed on a sheet under the condition of a toner loading amount of 1.8 mg / cm ² . Subsequently, an unfixed image was fixed on the paper using a fixing jig. The fixing conditions were a linear speed of 280 mm / second and a fixing temperature of 150 ° C.

  Subsequently, whether or not the toner could be fixed was confirmed by the following rubbing test. Specifically, the paper that passed through the fixing device was folded in half so that the surface on which the image was formed was on the inside. The folded paper was rubbed 5 times on the crease using a 1 kg weight coated with a fabric. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the toner peeling length (peeling width) of the bent portion was measured. Table 2 shows the measured peeling width. A toner having a peeling width of less than 1.0 mm was regarded as acceptable.

<10. Evaluation of high-temperature offset resistance>
For the evaluation of the high temperature offset resistance, the same evaluation machine, fixing jig and paper as those for the low temperature fixing property were used. Using an evaluation machine, a solid image (unfixed image) having a size of 20 mm × 30 mm was formed on a sheet under the condition of a toner loading amount of 1.8 mg / cm ² . Subsequently, an unfixed image was fixed on a sheet using a fixing jig to obtain a fixed image. The linear velocity during fixing was 100 mm / second. The fixing temperature of the fixing jig was increased from 200 ° C. by 5 ° C., and the maximum temperature at which no hot offset occurred in the fixed image (temperature at which no offset occurred) was measured. Whether or not hot offset occurred was confirmed by observing the fixed image with the naked eye. When a hot offset occurs, an image defect in which the toner is transferred to the sheet is confirmed in a portion corresponding to the second turn of the heat roller of the fixing jig in the fixed image. Table 2 shows the measured non-offset temperature. A toner having an offset non-occurrence temperature of 210 ° C. or higher was regarded as acceptable.

<11. Evaluation of heat-resistant storage stability>
10.00 g of the toner was weighed into a sample bottle and allowed to stand for 100 hours in a thermostatic bath set at 50 ° C. (“CONVECTION OVEN” manufactured by Sanyo Electric Co., Ltd.). Subsequently, the sample bottle was taken out from the thermostat and allowed to stand overnight at room temperature. As a result, a toner for heat resistant storage stability evaluation was obtained. Thereafter, the toner for heat resistant storage stability evaluation was sieved using a powder tester (“TYPE PT-E 84810” manufactured by Hosokawa Micron Corporation). Specifically, according to the manual of a powder tester (manufactured by Hosokawa Micron Co., Ltd.), a toner for heat-resistant storage stability evaluation was screened using a 26-mesh screen under the conditions of rheostat scale 2.5 and time 20 seconds. . After sieving, the mass of the toner remaining on the sieve (the mass of residual sieving toner) was measured. Table 2 shows the measured screen residual toner mass. A toner having a sieve residual toner mass of 0.20 g or less was regarded as acceptable.

  In Table 2, “Q / d distribution width” indicates a frequency width of ¼ of the mode value of the toner charge amount distribution. “ID” indicates the image density.

The toner particles contained in the toners A-1 to A-9 had composite particles and a shell layer covering the composite particles. The composite particles had a toner core and a plurality of magnetic powder particles provided on the surface of the toner core. The shell layer contained a thermosetting resin. The content of the magnetic powder particles was 0.50 parts by mass or more and 3.00 parts by mass or less with respect to the toner core of 100.00 parts by mass. The magnetic powder particles had a polyhedral shape. The average Haywood diameter of the magnetic powder particles was 0.010 μm or more and 0.500 μm or less. The volume resistivity value of the magnetic powder particles was 1 × 10 ² Ω · cm or more and 1 × 10 ⁸ Ω · cm or less. The surface of the composite particle had negative chargeability, and the triboelectric charge amount of the composite particle was −9 μC / g or less. Therefore, as shown in Table 2, with these toners, the Q / d distribution width was narrow, and both the initial charge amount and the charge amount after printing 30,000 sheets were 20 μC / g or more and less than 30 μC / g. That is, these toners were excellent in charging stability. Further, these toners were excellent in low-temperature fixability and heat-resistant storage stability.

In toner B-1, the volume resistivity of the magnetic powder particles was less than 1 × 10 ² Ω · cm. Therefore, as shown in Table 2, the charge amount after printing 30,000 sheets was reduced in the toner B-1.

In Toner B-2, the volume resistivity of the magnetic powder particles exceeded 1 × 10 ⁸ Ω · cm. Therefore, as shown in Table 2, the toner B-2 has a wide Q / d distribution width, and the charge amount after printing 30,000 sheets is too high. With toner B-2, the image density after printing 30,000 sheets was lowered because the amount of charge was too high.

  In Toner B-3, the magnetic powder particles were not polyhedral. Therefore, as shown in Table 2, in the toner B-3, the Q / d distribution width is wide, and the charge amount after printing 30,000 sheets was too high. The reason is presumed that the spherical magnetic powder particles were easier to accumulate charges than the polyhedral magnetic powder particles. In Toner B-3, the image density after printing 30,000 sheets was lowered because the charge amount was too high. In addition, the toner B-3 was inferior in low-temperature fixability. The reason is presumed that the spherical magnetic powder particles are less likely to be the starting point for destroying the shell layer compared to the polyhedral magnetic powder particles.

  In Toner B-4, the average Haywood diameter of the magnetic powder particles was less than 0.010 μm. Therefore, as shown in Table 2, the toner B-4 had a wide Q / d distribution width, and the charge amount after printing 30,000 sheets was too high. The reason is that since the average Haywood diameter of the magnetic powder particles was less than 0.010 μm, the dispersibility of the magnetic powder particles with respect to the toner core in the composite particle forming process was poor, and the magnetic powder particles adhered unevenly to the surface of the toner core. It is presumed that. With toner B-4, the image density after printing 30,000 sheets was lowered because the amount of charge was too high. In addition, toner B-4 was inferior in low-temperature fixability. The reason is presumed that the magnetic powder particles hardly adhere to the surface of the toner core, so that the magnetic powder particles are unlikely to be a starting point for destroying the shell layer.

  In toner B-5, the average Haywood diameter of the magnetic powder particles exceeded 0.500 μm. Therefore, as shown in Table 2, in the toner B-5, the Q / d distribution width is wide, and the charge amount after printing 30,000 sheets was too high. The reason is that, because the average Haywood diameter of the magnetic powder particles exceeded 0.500 μm, the magnetic powder particles were easily detached from the toner core in the composite particle forming step, and the magnetic powder particles were difficult to be fixed in the shell layer. Guessed. With toner B-5, the image density after printing 30,000 sheets was lowered because the amount of charge was too high. Further, the toner B-5 was inferior in low-temperature fixability. The reason is presumed that the magnetic powder particles are difficult to be fixed in the shell layer, so that the magnetic powder particles are unlikely to become a starting point for destroying the shell layer.

  With toner B-6, the triboelectric charge amount of the composite particles was larger than −9 μC / g. Therefore, as shown in Table 2, in the toner B-6, the Q / d distribution width was wide, and the charge amount at the initial stage and after printing 30,000 sheets was low. In addition, Toner B-6 was inferior in heat resistant storage stability. The reason is presumed that the formation of the shell layer by the thermosetting resin did not proceed well because the negative chargeability of the surface of the composite particles was low.

  In Toner B-7, the composite particles did not have magnetic powder particles. Therefore, as shown in Table 2, the toner B-7 has a wide Q / d distribution width, and the charge amount after printing 30,000 sheets is too high. The reason is presumed that it was difficult to adjust the electrical resistance of the shell layer because the toner particles do not have magnetic powder particles. With toner B-7, the image density after printing 30,000 sheets was lowered because the charge amount was too high. In addition, the toner B-7 was inferior in low-temperature fixability. The reason is presumed that since the toner particles do not have magnetic powder particles, the shell layer is hardly broken at the time of fixing the toner.

  In Toner B-8, the content of the magnetic powder particles was less than 0.50 parts by mass with respect to the toner core of 100.00 parts by mass. Therefore, as shown in Table 2, in the toner B-8, the Q / d distribution width was wide, and the charge amount after printing 30,000 sheets was too high. The reason is presumed that it was difficult to adjust the electric resistance of the shell layer because the content of the magnetic powder particles was small. With toner B-8, the image density after printing 30,000 sheets was lowered because the amount of charge was too high. In addition, the toner B-8 was inferior in low-temperature fixability. This is presumably because the shell layer was difficult to be destroyed at the time of fixing the toner because the content of the magnetic powder particles was small.

  In toner B-9, the content of the magnetic powder particles was more than 3.00 parts by mass with respect to the toner core of 100.00 parts by mass. Therefore, as shown in Table 2, the toner B-9 had a wide Q / d distribution width and a low charge amount after printing 30,000 sheets. In addition, the toner B-9 was inferior in low-temperature fixability.

  From the above, it has been shown that the toner of the present invention can achieve both charging stability, low-temperature fixability and heat-resistant storage stability. Further, it has been shown that according to the method for producing a toner of the present invention, it is possible to produce a toner having both charging stability, low-temperature fixability and heat-resistant storage stability.

  The toner according to the present invention can be used for forming an image by an image forming apparatus. The toner manufactured by the toner manufacturing method according to the present invention can be used to form an image by an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Toner particle 2 Toner core 3 Magnetic powder particle 4 Shell layer 5 Composite particle

Claims (12)

A positively chargeable toner comprising a plurality of toner particles,
The toner particles include composite particles and a shell layer that covers the composite particles;
The composite particle has a toner core and a plurality of magnetic powder particles provided on the surface of the toner core,
The shell layer contains a thermosetting resin,
The content of the magnetic powder particles is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core.
The magnetic powder particles have a polyhedral shape,
The average Haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.500 μm or less,
The magnetic powder particles have a volume resistivity of 1 × 10 ² Ω · cm to 1 × 10 ⁸ Ω · cm,
A positively chargeable toner in which the surface of the composite particle has negative chargeability, and the triboelectric charge amount of the composite particle is −9 μC / g or less.   The positively chargeable toner according to claim 1, wherein the magnetic powder particles have an octahedral shape or a hexahedral shape. The magnetic powder particles have a magnetic powder core and a coating layer that covers the magnetic powder core,
The positively chargeable toner according to claim 1, wherein the coating layer contains a surface treatment agent or a hydrolyzate of the surface treatment agent. The magnetic powder particles have a magnetic powder core and a coating layer that covers the magnetic powder core,
The positively chargeable toner according to claim 1, wherein the coating layer contains alkyltrialkoxysilane or silica. The magnetic powder particles have a magnetic powder core and a coating layer that covers the magnetic powder core,
The positively chargeable toner according to claim 1, wherein the coating layer contains n-octyltriethoxysilane.   The positively chargeable toner according to claim 1, wherein the thermosetting resin has a cationic group.   The positively chargeable toner according to claim 1, wherein the thermosetting resin is a melamine resin. 8. The positive chargeability according to claim 1, wherein the magnetic powder particles have a volume resistivity of 3.0 × 10 ⁵ Ω · cm to 4.5 × 10 ⁵ Ω · cm. toner.   The positively chargeable toner according to claim 1, wherein the composite particles have a triboelectric charge amount of −30 μC / g or more and −18 μC / g or less. The average Haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.300 μm or less,
The positively chargeable toner according to claim 1, wherein the composite particles have a triboelectric charge amount of −20 μC / g or more and −15 μC / g or less. A method for producing a positively chargeable toner comprising a plurality of toner particles,
A composite particle forming step of forming a composite particle by attaching a plurality of magnetic powder particles to the surface of the toner core;
A shell layer forming step of polymerizing or copolymerizing a thermosetting resin material on the surface of the composite particles to form a shell layer so as to cover the composite particles;
In the composite particle forming step, the addition amount of the magnetic powder particles is 0.50 parts by mass or more and 3.00 parts by mass or less with respect to 100.00 parts by mass of the toner core.
The shell layer formed in the shell layer forming step contains a thermosetting resin,
The magnetic powder particles have a polyhedral shape,
The average Haywood diameter of the magnetic powder particles is 0.010 μm or more and 0.500 μm or less,
The magnetic powder particles have a volume resistivity of 1 × 10 ² Ω · cm to 1 × 10 ⁸ Ω · cm,
The method for producing a positively chargeable toner, wherein the surface of the composite particle has negative chargeability, and the triboelectric charge amount of the composite particle is −9 μC / g or less. A surface treatment step of treating the surface of the magnetic powder core with a surface treatment agent;
In the surface treatment step, the magnetic powder particles are obtained,
The magnetic powder particles have the magnetic powder core and a coating layer that covers the magnetic powder core,
The method for producing a positively chargeable toner according to claim 11, wherein the coating layer contains the surface treatment agent or a hydrolyzate of the surface treatment agent.

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