JP2016156920A - Toner for electrostatic latent image development and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat-resistant storage property and low-temperature fixability of a toner for electrostatic latent image development to further suppress the attenuation of charge of the toner for electrostatic latent image development.SOLUTION: A toner for electrostatic latent image development contains toner cores and a shell layer that coats the surface of each of the toner cores. The shell layer includes a thermosetting resin and a thermoplastic resin having a hydrophobic functional group at a terminal. The thermosetting resin is one or more resins selected from the group consisting of a melamine resin, urea resin, and glyoxal resin.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic latent image developing toner and a method for producing the same.

  From the viewpoint of energy saving and downsizing of the image forming apparatus, a toner that can be satisfactorily fixed without heating the fixing roller as much as possible is desired. In general, a binder resin having a low melting point or glass transition point or a release agent having a low melting point is often used for preparing a toner having excellent low-temperature fixability. However, when such a toner is stored at a high temperature, there is a problem that toner particles contained in the toner tend to aggregate. When toner particles are aggregated, the charge amount of the aggregated toner particles tends to be lower than that of other non-aggregated toner particles.

  A toner containing toner particles having a core-shell structure may be used for the purpose of improving the low-temperature fixability, high-temperature stability, and anti-blocking property of the toner. For example, Patent Document 1 describes a toner containing toner particles in which the surface of a toner core is coated with a thin film containing a thermosetting component, and the softening temperature of the toner core is 40 ° C. or higher and 150 ° C. or lower.

JP 2004-138985 A

  However, the toner described in Patent Document 1 uses a hydrophilic thermosetting resin such as a melamine resin. The hydrophilic thermosetting resin easily absorbs water molecules under high temperature and high humidity. As a result, the electrical conductivity of the toner surface tends to increase, and the charge amount of the toner tends to decrease. When the toner charge amount decreases, the toner transfer efficiency tends to decrease.

  The present invention has been made in view of the above problems, and improves the heat-resistant storage stability and low-temperature fixability of the electrostatic latent image developing toner, and further suppresses charge attenuation of the electrostatic latent image developing toner. With the goal.

  The electrostatic latent image developing toner of the present invention contains toner particles including a toner core and a shell layer covering the surface of the toner core. The shell layer includes a thermosetting resin having a hydrophobic functional group at a terminal and a thermoplastic resin. The thermosetting resin is at least one resin selected from the group consisting of a melamine resin, a urea resin, and a glyoxal resin.

  The method for producing a toner for developing an electrostatic latent image of the present invention includes a toner core production step, a shell layer forming step, and a shell layer surface treatment step. In the toner core manufacturing process, a toner core is manufactured. In the shell layer forming step, a mixture of the toner core, the thermosetting resin precursor, and the thermoplastic resin obtained in the toner core manufacturing step is heated, and the thermosetting resin and the thermoplastic are formed on the surface of the toner core. A shell layer containing resin is formed. In the shell layer surface treatment step, the end of the thermosetting resin contained in the shell layer is modified with a hydrophobic functional group using a surface treatment agent having a hydrophobic functional group. The thermosetting resin is at least one resin selected from the group consisting of a melamine resin, a urea resin, and a glyoxal resin.

  According to the present invention, the heat-resistant storage stability and low-temperature fixability of the electrostatic latent image developing toner can be improved, and further, charge attenuation of the electrostatic latent image developing toner can be suppressed.

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

  The electrostatic latent image developing toner (also simply referred to as toner) according to this embodiment is a powder composed of a large number of toner particles. The toner according to the exemplary embodiment can be used in, for example, an electrophotographic apparatus (image forming apparatus).

  In an electrophotographic apparatus, an electrostatic latent image is developed using a developer containing toner. As a result, charged toner adheres to the electrostatic latent image formed on the photoreceptor. Then, after the adhered toner is transferred to the transfer belt, the toner image on the transfer belt is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan.

The toner according to the exemplary embodiment has the following configurations (1) and (2).
(1) Contain toner particles including a toner core and a shell layer covering the surface of the toner core. The shell layer includes a thermosetting resin and a thermoplastic resin.
(2) The thermosetting resin is at least one resin selected from the group consisting of a melamine resin, a urea resin, and a glyoxal resin. The thermosetting resin has a hydrophobic functional group at the terminal.

  Configuration (1) is useful for achieving both heat-resistant storage stability and low-temperature fixability of the toner. Specifically, it is considered that the heat resistant storage stability of the toner is improved by covering the toner core with the shell layer. Further, it is considered that the thermosetting resin improves the heat-resistant storage stability of the toner, and the thermoplastic resin improves the low-temperature fixability of the toner.

  Configuration (2) is useful for suppressing charge decay of the toner. Specifically, when the thermosetting resin constituting the shell layer undergoes a polymerization reaction, a terminal functional group such as an amino group may remain unreacted. Moisture is easily adsorbed to the unreacted terminal functional groups of the thermosetting resin contained in the shell layer. When moisture is adsorbed on the shell layer, the charge of the toner tends to attenuate. In the toner having the configuration (2), the end of the thermosetting resin is modified with a hydrophobic functional group. When the thermosetting resin contained in the shell layer has a hydrophobic functional group at the end, it becomes difficult for moisture to be adsorbed to the shell layer. It is considered that charge attenuation of the toner can be suppressed by suppressing moisture adsorption of the shell layer.

  The toner according to the present embodiment includes toner particles having both configurations (1) and (2) (hereinafter referred to as toner particles according to the present embodiment). The toner containing toner particles of this embodiment is excellent in heat-resistant storage stability, low-temperature fixability, and charge retention (see Tables 1 and 2 described later). The toner preferably contains the toner particles of this embodiment in a proportion of 80% by number or more, more preferably contains the toner particles of this embodiment in a proportion of 90% by number or more, and a proportion of 100% by number. More preferably, the toner particles of the present embodiment are included.

  The toner particles include a toner core and a shell layer that covers the surface of the toner core. The toner core includes a binder resin. The toner particles may contain an optional component (for example, a colorant, a release agent, a charge control agent, or a magnetic powder) in the binder resin as necessary.

  An external additive may be added to the surface of the toner particles (toner base particles) as necessary. The toner particles before being treated with the external additive may be referred to as toner mother particles. A plurality of shell layers may be laminated on the surface of the toner core.

  The toner may be used as a one-component developer. Further, a two-component developer may be prepared by mixing toner with a desired carrier.

[Toner core]
The toner core includes a binder resin. The toner core may contain an internal additive (for example, a colorant, a release agent, a charge control agent, or a magnetic powder).

(Binder resin)
In the toner core, the binder resin often occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core has a strong tendency to become anionic, and the binder resin has an amino group, a quaternary ammonium group, or When it has an amide group, the toner core has a strong tendency to become cationic. In order for the binder resin to have a strong anionic property, the hydroxyl value (OHV value) and the acid value (AV value) of the binder resin are each preferably 10 mgKOH / g or more, and each 20 mgKOH / g or more. Is more preferable.

  As the binder resin, a resin having one or more functional groups selected from the group consisting of an ester group, a hydroxyl group, an ether group, an acid group, and a methyl group is preferable, and a resin having a hydroxyl group and / or a carboxyl group is more preferable. . The binder resin having such a functional group easily reacts with the shell material (for example, methylol melamine) to be chemically bonded. When such a chemical bond occurs, the bond between the toner core and the shell layer becomes strong. Further, as the binder resin, a resin having a functional group containing active hydrogen in the molecule is also preferable.

  The glass transition point (Tg) of the binder resin is preferably equal to or lower than the curing start temperature of the shell material. When such a binder resin having Tg is used, it is considered that the toner fixability is unlikely to deteriorate even during high-speed fixing.

  The Tg of the binder resin can be measured using, for example, a differential scanning calorimeter. More specifically, by measuring the endothermic curve of the sample (binder resin) using a differential scanning calorimeter, the Tg of the binder resin can be obtained from the change point of specific heat in the obtained endothermic curve.

  The softening point (Tm) of the binder resin is preferably 100 ° C. or lower, and more preferably 95 ° C. or lower. When the Tm of the binder resin is 100 ° C. or less, the toner fixability is hardly lowered even during high-speed fixing. Further, when the Tm of the binder resin is 100 ° C. or less, when the shell layer is formed on the surface of the toner core in the aqueous medium, the toner core is likely to be partially softened during the curing reaction of the shell layer. The toner core is easily rounded due to surface tension. In addition, Tm of binder resin can be adjusted by combining several resin which has different Tm.

The Tm of the binder resin can be measured using, for example, a Koka type flow tester. More specifically, a sample (binder resin) is set in the Koka flow tester, and the binder resin is melted and discharged under predetermined conditions. Then, an S-shaped curve of the sample (binder resin) is measured. The Tm of the binder resin can be read from the obtained S-shaped curve. In the obtained S-curve, if the maximum stroke value is S ₁ and the low-temperature baseline stroke value is S ₂ , the stroke value in the S-curve is “(S ₁ + S ₂ ) / 2”. The temperature (° C.) at which corresponds to the Tm of the measurement sample (binder resin).

  As the binder resin, a thermoplastic resin is preferable. Preferable examples of the thermoplastic resin that can be used as the binder resin include a styrene resin, an acrylic acid resin, an olefin resin (more specifically, a polyethylene resin or a polypropylene resin), a vinyl resin (more specifically, Specifically, a vinyl chloride resin, a polyvinyl alcohol resin, a vinyl ether resin, or an N-vinyl resin), a polyester resin, a polyamide resin, a urethane resin, a styrene acrylic acid resin, or a styrene butadiene resin can be used. Among them, the styrene acrylic resin and the polyester resin are excellent in the dispersibility of the colorant in the toner, the charging property of the toner, and the fixing property of the toner to the recording medium, respectively.

  Hereinafter, a styrene acrylic acid resin that can be used as a binder resin will be described. The styrene acrylic acid resin is a copolymer of a styrene monomer and an acrylic acid monomer.

  Suitable examples of the styrenic monomer include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, Or p-ethylstyrene is mentioned.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic acid n. -Butyl, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Examples of (meth) acrylic acid hydroxyalkyl esters include: 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic acid 4 -Hydroxybutyl is mentioned. In some cases, acrylic acid and methacrylic acid are collectively referred to as “(meth) acrylic acid”, and acrylic acid ester and methacrylic acid ester are collectively referred to as “(meth) acrylate”.

  When preparing a styrene acrylic acid resin, a hydroxyl group-containing monomer (for example, p-hydroxystyrene, m-hydroxystyrene, or (meth) acrylic acid hydroxyalkyl ester) is used to add a hydroxyl group to the styrene acrylic acid resin. Can be introduced. Moreover, the hydroxyl value of the styrene acrylic resin obtained can be adjusted by adjusting the usage-amount of the monomer which has a hydroxyl group.

  When preparing a styrene acrylic resin, a carboxyl group can be introduced into the styrene acrylic resin by using (meth) acrylic acid (monomer). Moreover, the acid value of the styrene acrylic resin obtained can be adjusted by adjusting the usage-amount of (meth) acrylic acid.

  When the binder resin is a styrene acrylic resin, the number average molecular weight (Mn) of the styrene acrylic resin is preferably 2000 or more and 3000 or less in order to achieve both the strength of the toner core and the fixing property of the toner. . The molecular weight distribution (ratio Mw / Mn of mass average molecular weight (Mw) to number average molecular weight (Mn)) of the styrene acrylic resin is preferably 10 or more and 20 or less. Gel permeation chromatography can be used to measure Mn and Mw of the styrene acrylic resin.

  Hereinafter, the polyester resin that can be used as the binder resin will be described. The polyester resin can be obtained by polycondensation or copolycondensation of a divalent or trivalent or higher alcohol and a divalent or trivalent or higher carboxylic acid.

  Examples of dihydric alcohols that can be used to prepare the polyester resin include diols or bisphenols.

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

  Preferable examples of bisphenols include bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A ether, or polyoxypropylenated bisphenol A ether.

  Suitable examples of trihydric or higher alcohols that can be used to prepare the polyester resin 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, Examples include trimethylolpropane or 1,3,5-trihydroxymethylbenzene.

  Suitable examples of divalent carboxylic acids that can be used to prepare the polyester resin 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, or alkyl succinic acid or alkenyl succinic acid (more specifically, n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, or isododecenyl succinic acid).

  Preferable examples of the trivalent or higher carboxylic acid that can be used for preparing the polyester resin include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1 , 2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2, Examples include 4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

  The divalent or trivalent or higher carboxylic acid may be used as an ester-forming derivative (for example, acid halide, acid anhydride, or lower alkyl ester). Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  When preparing the polyester resin, the acid value and hydroxyl value of the polyester resin can be adjusted by changing the amount of alcohol used and the amount of carboxylic acid used. When the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  When the binder resin is a polyester resin, the number average molecular weight (Mn) of the polyester resin is preferably 1000 or more and 2000 or less in order to achieve both the strength of the toner core and the fixing property of the toner. The molecular weight distribution of the polyester resin (ratio Mw / Mn of mass average molecular weight (Mw) to number average molecular weight (Mn)) is preferably 7 or more and 21 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the polyester resin.

(Coloring agent)
The toner core may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. The amount of the colorant to be used is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, or arylamide compounds. Suitable examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, or 194), naphthol yellow S, Hansa yellow G, or C.I. I. Bat yellow is mentioned.

  Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, or perylene compounds. Suitable examples of magenta colorants include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254).

  Examples of cyan colorants include copper phthalocyanine compounds, copper phthalocyanine derivatives, anthraquinone compounds, or basic dye lake compounds. Suitable examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66), phthalocyanine blue, C.I. I. Bat Blue, or C.I. I. Acid blue.

(Release agent)
The toner core may contain a release agent. The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to increase the anionicity of the toner core, it is preferable to produce the toner core using an anionic wax. In order to improve the fixing property or 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 20 parts by mass or less.

  Preferable examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax Or an oxide of an aliphatic hydrocarbon wax such as a block copolymer of oxidized polyethylene wax; a plant wax such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; beeswax, lanolin, or Animal waxes such as whale wax; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate wax or castor wax; Such as carnauba wax, part or all of fatty acid esters are de-oxidized waxes.

  In order to improve the compatibility between the binder resin and the release agent, a compatibilizing agent may be added to the toner core.

(Charge control agent)
The toner core may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charging stability or charging rising property of the toner. Further, the anionic property of the toner core can be enhanced by including a negatively chargeable charge control agent in the toner core. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

(Magnetic powder)
The toner core may contain magnetic powder. Examples of magnetic powder include iron (more specifically, ferrite or magnetite), a ferromagnetic metal (more specifically, cobalt or nickel), a compound containing iron and / or a ferromagnetic metal (more specifically, Is an alloy), a ferromagnetic alloy that has been subjected to a ferromagnetization treatment (for example, heat treatment), or chromium dioxide.

  In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When a shell layer is formed on the surface of the toner core under acidic conditions, if the metal ions are eluted on the surface of the toner core, the toner core and other toner cores are easily fixed. By suppressing the elution of metal ions from the magnetic powder, it is possible to suppress adhesion between the toner core and another toner core.

(Toner core frictional charge)
The triboelectric charge amount of the toner core is preferably negative, more preferably −10 μC / g or less. A method for measuring the triboelectric charge amount will be described below. A standard carrier (standard carrier for negatively charged polarity toner “N-01”) provided by the Imaging Society of Japan and a toner core are mixed for 30 minutes using a tumbler mixer. At this time, the usage amount of the toner core is 7% by mass with respect to the mass of the standard carrier. After mixing, the triboelectric charge amount of the toner core is measured using a Q / m meter (“MODEL 210HS-2A” manufactured by Trek). The triboelectric charge amount of the toner core measured in this way is an index of whether the toner core is easily charged to a positive or negative polarity and an index of the ease of charging of the toner core.

  When the triboelectric charge amount of the toner core is negative, the shell layer material (thermoplastic resin and thermosetting resin precursor) that is positively charged in the aqueous medium is easily attracted electrically to the toner core. On the surface of the toner core, the reaction between the material of the shell layer adsorbed on the toner core and the binder resin (for example, polyester resin) in the toner core proceeds favorably.

(Zeta potential of toner core)
Regarding the toner core, the zeta potential measured in an aqueous medium adjusted to pH 4 is preferably negative, and more preferably −10 mV or less. Examples of the zeta potential measurement method include an electrophoresis method, an ultrasonic method, and an ESA (electroacoustic) method.

  In the electrophoresis method, an electric field is applied to the particle dispersion to cause electrophoresis of charged particles in the dispersion, and the zeta potential is calculated based on the electrophoresis speed. As an example of the electrophoresis method, there is a laser Doppler method (a method in which an electrophoretic velocity is obtained from the amount of Doppler shift of the obtained scattered light by irradiating the electrophoretic particles with laser light). The laser Doppler method has the advantage that the particle concentration in the dispersion does not need to be high, the number of parameters necessary for calculating the zeta potential is small, and the electrophoresis speed can be detected with high sensitivity.

  The ultrasonic method is a method of irradiating a particle dispersion with ultrasonic waves to vibrate charged particles in the dispersion and calculating a zeta potential based on a potential difference caused by the vibration.

  In the ESA method, a high frequency voltage is applied to the particle dispersion to vibrate charged particles in the dispersion to generate ultrasonic waves. Then, the zeta potential is calculated from the magnitude (intensity) of the ultrasonic waves.

  The ultrasonic method and the ESA method have an advantage that the zeta potential can be measured with high sensitivity even in a particle dispersion having a high particle concentration (for example, exceeding 20% by mass).

[Shell layer]
In the toner of the present embodiment, the shell layer includes a thermosetting resin and a thermoplastic resin. Even if it is a thin film, the shell layer comprised only from a thermosetting resin tends to become hard. Therefore, in the toner having such a shell layer, the shell layer is not easily broken, and the fixability may not be sufficient. However, in a toner in which the shell layer includes a thermosetting resin and a thermoplastic resin, even when the thin and hard shell layer is uniformly formed, the shell layer tends to have a plurality of strength points. There is. For this reason, the fixing property of the toner is improved, and the shell layer can be instantaneously destroyed at the time of fixing.

  The thermosetting resin is at least one resin selected from the group consisting of melamine resin, urea resin, and glyoxal resin. Melamine resin is an addition condensate of melamine and formaldehyde. The monomer used to form the melamine resin is melamine. Urea resin is an addition condensate of urea and formaldehyde. The monomer used to form the urea resin is urea. Glyoxal resin is an addition condensate of a reaction product of glyoxal and urea with formaldehyde. The monomer used to form the glioxal resin is the reaction product of glyoxal and urea. These may be subjected to known modification.

  Specific examples of the thermoplastic resin include acrylic acid resin or styrene acrylic acid resin. As the thermoplastic resin, a styrene acrylic acid resin is preferable from the viewpoint of availability, dispersion stability, and cost merit.

  The acrylic acid resin is a resin obtained by copolymerizing at least a monomer containing an acrylic acid monomer. The content of the acrylic acid monomer contained in the acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Most preferably, it is mass%.

  Examples of acrylic acid monomers used in the preparation of acrylic resins include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, or butyl (meth) acrylate. Alkyl (meth) acrylates; such as (meth) acrylamide, N-alkyl (meth) acrylamide, N-aryl (meth) acrylamide, N, N-dialkyl (meth) acrylamide, or N, N-diaryl (meth) acrylamide A (meth) acrylamide compound is mentioned.

  The acrylic resin may be a resin obtained by copolymerizing an acrylic monomer and another monomer other than the acrylic monomer. Examples of monomers other than acrylic monomers include olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, or octene-1; allyl acetate, allyl benzoate, aceto Allyl esters such as allyl acetate or allyl lactate; hexyl vinyl ether, octyl vinyl ether, ethyl hexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 2-ethylbutyl vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, benzyl Vinyl ether, vinyl phenyl ether, vinyl tolyl ether, vinyl chlorophenyl ether, vinyl-2,4-dichlorophenyl ether, or vinyl Vinyl ethers such as naphthyl ether; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl diethyl acetate, vinyl chloroacetate, vinyl methoxy acetate, vinyl butoxy acetate, vinyl phenyl acetate, vinyl acetoacetate, And vinyl esters such as vinyl lactate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, or vinyl naphthoate.

  The styrene acrylic acid resin is a resin obtained by copolymerizing a monomer containing at least a styrene monomer and an acrylic acid monomer. The total content of the styrene monomer and acrylic acid monomer contained in the styrene acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more, and 90% by mass. The above is particularly preferable, and 100% by mass is most preferable.

  Styrene monomers used for the preparation of styrene acrylic acid resins include styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene. , Pn-butylstyrene, p-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, or p-chlorostyrene. Of the styrenic monomers, styrene is preferable.

  The acrylic monomer used for the preparation of the styrene acrylic resin is the same as the acrylic monomer used for the preparation of the acrylic resin. Among the acrylic monomers, alkyl (meth) acrylate is preferable, and butyl acrylate is more preferable.

  The styrene acrylic acid resin preferably contains a carboxyl group as an acidic group. In this case, the acid value of the styrene acrylic acid resin can be adjusted by increasing or decreasing the amount of acrylic acid used when preparing the styrene acrylic acid resin.

  The styrene acrylic acid resin may be a resin obtained by copolymerizing a styrene monomer, an acrylic acid monomer, and a monomer other than the styrene monomer and the acrylic acid monomer. Examples of other monomers used for adjusting the styrene acrylic resin are the same as those other than the acrylic monomer used for adjusting the acrylic resin.

  The shell layer preferably contains a nitrogen atom derived from melamine or the like. A toner having such a shell layer is easily positively charged to a desired charge amount when an image is formed by positively charging the toner. In order to positively charge the toner to a desired charge amount, the content of nitrogen atoms in the shell layer is preferably 10% by mass or more.

  The thickness of the shell layer is preferably 30 nm or less, and more preferably 1 nm or more and 20 nm or less. If the shell layer is too thick, the shell layer is not easily destroyed even if pressure is applied when fixing the toner to the recording medium. In this case, the softening or melting of the binder resin (or release agent) contained in the toner core does not proceed quickly, and it is difficult to fix the toner on the recording medium in a low temperature range. On the other hand, a shell layer that is too thin has low strength, and the shell layer may be destroyed by an impact in a situation such as transportation. Here, when the toner is stored at a high temperature, the toner particles in which at least a part of the shell layer is broken easily aggregate. This is because a component such as a release agent tends to ooze out to the surface of the toner particles through the broken portion in the shell layer at a high temperature.

  The thickness of the shell layer can be measured by analyzing a cross-sectional TEM image of the toner particles using commercially available image analysis software. As commercially available image analysis software, software such as WinROOF (manufactured by Mitani Corporation) can be used. Specifically, two straight lines that are orthogonal to each other at substantially the center of the cross section of the toner are drawn, and the lengths of four points on the two straight lines that intersect the shell layer are measured. The average value of the four lengths thus measured is taken as the thickness of the shell layer of one toner particle to be measured. Such a measurement of the thickness of the shell layer is performed on 10 or more toner particles, and an average value of the thicknesses of the shell layers included in each of the plurality of toner particles to be measured is obtained. The obtained average value is taken as the film thickness of the shell layer provided in the toner particles.

  If the shell layer is too thin, it may be difficult to measure the thickness of the shell layer because the interface between the shell layer and the toner core is unclear on the TEM image. In such a case, a combination of TEM imaging and electron energy loss spectroscopy (EELS) is used to map an element (for example, nitrogen) characteristic of the material of the shell layer in the TEM image, and the shell layer and the toner core. And the thickness of the shell layer may be measured.

[Surface treatment agent]
A surface treating agent is used in order to modify the terminal functional group of a thermosetting resin. The surface treatment agent has a hydrophobic functional group. Examples of the hydrophobic functional group include a benzyl group or an alkyl group having 8 or more carbon atoms. Note that the alkyl group having 8 or more carbon atoms may have a branched chain. Examples of the surface treatment agent include benzylamine, dodecylamine, octylamine, nonylamine, decylamine, and undecylamine.

  The content of the surface treatment agent is preferably 80 parts by mass or more and 300 parts by mass or less, and 100 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the thermosetting resin used for forming the shell layer. More preferred.

[External additive]
An external additive may be attached to the surface of the toner particles as necessary. Examples of the external additive include metal oxide (for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate), or silica fine particles.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less. The amount of the external additive used is preferably 0.5 parts by mass or more and 10 parts by mass or less, 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.

  A two-component developer can be prepared by mixing the toner of this embodiment with a desired carrier. When preparing a two-component developer, it is preferable to use a magnetic carrier.

  An example of a suitable carrier is a carrier having a carrier core coated with a resin. Specific examples of carrier cores 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 of iron-nickel alloy or iron-cobalt alloy; ceramics (titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate , Particles of lead titanate, lead zirconate, or lithium niobate); particles of a high dielectric constant material (ammonium dihydrogen phosphate, potassium dihydrogen phosphate, or Rochelle salt). A resin carrier may be prepared by dispersing the particles in a resin.

  Examples of resins that coat the carrier core include acrylic acid polymers, styrene polymers, styrene acrylic acid copolymers, olefin polymers (polyethylene, chlorinated polyethylene, or polypropylene), polyvinyl chloride, poly Vinyl acetate, polycarbonate resin, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, urethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, or polyvinylidene fluoride), phenol Examples include resins, xylene resins, diallyl phthalate resins, polyacetal resins, and amino resins. Two or more of these resins may be combined.

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

  When preparing a two-component developer using a toner and a carrier, the toner content is preferably 3% by mass or more and 20% by mass or less with respect to the mass of the two-component developer. It is preferable that it is 15 mass% or less.

[Toner Production Method]
The method for producing a toner for developing an electrostatic latent image according to the present embodiment includes a toner core production process, a shell layer formation process, and a shell layer surface treatment process. In the toner core manufacturing process, a toner core is manufactured. In the shell layer forming process, a mixture of the toner core obtained in the toner core manufacturing process, the thermosetting resin precursor, and the thermoplastic resin is heated, so that the thermosetting resin and the thermoplastic resin are formed on the surface of the toner core. A shell layer is formed. In the shell layer surface treatment step, the shell layer is surface-treated by adding and heating a surface treatment agent having a hydrophobic functional group to the shell layer containing a thermosetting resin and a thermoplastic resin. The thermosetting resin is at least one resin selected from the group consisting of melamine resins, urea resins, and glyoxal resins. Hereinafter, a preferred method for producing the electrostatic latent image developing toner according to the present embodiment will be described.

(Toner core manufacturing process)
The toner core production process is not particularly limited as long as an arbitrary component (a component such as a colorant, a release agent, a charge control agent, or a magnetic powder) can be satisfactorily dispersed in the binder resin. Can be adopted as appropriate. In the toner core manufacturing process, for example, a pulverization method or an aggregation method is employed.

  In the pulverization method, a binder resin and an internal additive (for example, a colorant, a release agent, a charge control agent, or magnetic powder) are mixed. Subsequently, the obtained mixture is melted and kneaded. Subsequently, the obtained kneaded material is pulverized. Subsequently, the obtained pulverized product is classified. As a result, a toner core having a desired particle size can be obtained. According to the pulverization method, the toner core can be prepared relatively easily.

  The aggregation method includes, for example, an aggregation process and a coalescence process. In the aggregating step, fine particles containing the components constituting the toner core 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.

(Shell layer forming process)
The shell layer covering the toner core is formed by reacting a thermosetting resin precursor with a thermoplastic resin. The thermosetting resin precursor is a reaction product of melamine, urea, glyoxal and urea, or a precursor produced by an addition reaction of these with formaldehyde. In order to prevent the binder resin from dissolving in the solvent used to form the shell layer, or to prevent the release of components such as a release agent contained in the toner core, the shell layer is formed in a solvent such as water. Preferably, it is done.

  The shell layer is preferably formed by adding a material for forming the shell layer to the aqueous dispersion containing the toner core. As a method for satisfactorily dispersing the toner core in the aqueous medium, there is a method in which the toner core is mechanically dispersed in the aqueous medium using an apparatus that can stir the dispersion strongly (for example, “Hibismix” manufactured by Primix Co., Ltd.). Can be mentioned.

  The pH of the aqueous dispersion containing the toner core is preferably adjusted to about 4 using an acidic substance before the shell layer is formed. By adjusting the pH of the dispersion to the acidic side, the condensation reaction of the material used to form the shell layer described later is promoted.

  After adjusting the pH of the aqueous dispersion containing the toner core as necessary, the material for forming the shell layer is dissolved in the aqueous dispersion containing the toner core. Thereafter, the shell layer material is reacted in an aqueous dispersion to form a shell layer covering the surface of the toner core.

  The temperature at which the shell layer is formed 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. The polymerization time for forming the shell layer is preferably 30 minutes or longer and 2 hours or shorter.

  When the binder resin contains a resin having a hydroxyl group or a carboxyl group, such as a polyester resin, the methylol that the thermosetting resin precursor has and the hydroxyl group or carboxyl group exposed on the surface of the toner core when the shell layer is formed. The group reacts. As a result, a covalent bond is formed between the binder resin constituting the toner core and the resin constituting the shell layer. Then, the shell layer can be firmly attached to the toner core.

(Shell layer surface treatment process)
In order to surface-treat the shell layer, a surface treatment agent having a hydrophobic functional group is added to an aqueous medium and heated. By heating, the terminal functional group of the thermosetting resin constituting the shell layer reacts with the surface treatment agent having a hydrophobic functional group, and the terminal functional group is substituted with the hydrophobic group. As a result, toner mother particles having a surface-treated shell layer are obtained.

  The surface temperature of the shell layer is preferably 40 ° C. or higher and 95 ° C. or lower and preferably 50 ° C. or higher and 80 ° C. or lower in order for the surface treatment agent to react well with the terminal functional group of the shell layer. It is more preferable. The time for surface treatment of the shell layer is preferably 5 minutes or more and 2 hours or less.

  After the surface-treated shell layer is formed as described above, the dispersion liquid containing the toner mother particles is cooled to room temperature. Thereafter, if necessary, a step of cleaning the toner base particles (cleaning step), a step of drying the toner base particles (drying step), and a step of attaching an external additive to the surface of the toner base particles (external addition step) Then, the toner is recovered from the dispersion of the toner base particles.

(Washing process)
In the washing step, the toner base particles are washed with water. As a suitable cleaning method, a method of recovering wet cake-like toner base particles from a dispersion containing toner base particles by solid-liquid separation, and washing the obtained wet cake-like toner base particles with water. And 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 re-dispersed in water after the replacement.

(Drying process)
In the drying step, the toner base particles are dried. Suitable methods for drying the toner base particles include a method using a dryer (for example, a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, or a vacuum dryer). Among these methods, a method using a spray dryer is preferable in order to suppress aggregation of toner base particles during drying. When a spray dryer is used, the external additive can be attached to the surface of the toner base particles by spraying a dispersion of the external additive such as silica together with the dispersion of the toner base particles.

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

  The toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, after the shell layer material is dissolved in a solvent, the toner core may be added to the solvent. Further, after adding the toner core to the solvent, the material of the shell layer may be dissolved in the solvent. The method for forming the shell layer is arbitrary. For example, the shell layer may be formed using any of an in-situ polymerization method, a submerged cured coating method, and a coacervation method. Further, various processes may be omitted depending on the target toner. When the external additive is not attached to the surface of the toner base particles (the step of external addition is omitted), the toner base particles correspond to the toner particles. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously.

Example 1
(Manufacture of polyester resin)
1245 g of terephthalic acid, 1245 g of isophthalic acid, 1248 g of bisphenol A ethylene oxide adduct, and 744 g of ethylene glycol were charged into a 5 L four-necked flask. Subsequently, the inside of a flask was made into nitrogen atmosphere, and the temperature in a flask was raised to 250 degreeC, stirring the contents of a flask. After the flask contents were reacted for 4 hours under conditions of normal pressure and 250 ° C., 0.875 g of antimony trioxide, 0.548 g of triphenyl phosphate, and 0.102 g of tetrabutyl titanate were added to the flask. Subsequently, the pressure in the flask was reduced to 0.3 mmHg, and the temperature in the flask was increased to 280 ° C. The contents of the flask were reacted for 4 hours under conditions of a pressure of 0.3 mmHg and a temperature of 280 ° C. to obtain a polyester resin. The resulting polyester resin had a glass transition point Tg of 51 ° C., a number average molecular weight of 1800, and a molecular weight distribution of 7.5.

(Adjustment of binder resin dispersion)
The obtained polyester resin was coarsely pulverized using a mechanical pulverizer (“Turbomill T250” manufactured by Freund Turbo Inc.) so that the volume median diameter was 10 μm. Next, 100 g of the obtained coarsely pulverized product, 2 g of an anionic surfactant (“Emar E-27C” manufactured by Kao Corporation, component: sodium polyoxyethylene lauryl ether sulfate), and 50 g of 0.1N sodium hydroxide aqueous solution, And ion-exchanged water was further added to prepare a slurry having a total amount of 500 g. The obtained slurry was put into a pressure-resistant round bottom stainless steel container. Next, the slurry was heated to a temperature using a high-speed shearing emulsifying device (“Harmec HMT-CA-2” manufactured by M Technique Co., Ltd., CLEARMIX “CLM-2.2S” with anchor mixer “AM-0.2”). Shear dispersion was performed at 145 ° C. and a pressure of 0.5 MPa (G) for 30 minutes at a rotor rotational speed of 20000 rpm. After the shear dispersion, the slurry was stirred at a rotor rotational speed of 15000 rpm while cooling the slurry at a rate of 5 ° C./min until the internal temperature of the stainless steel container reached 50 ° C. Thereafter, the slurry was cooled to room temperature at a rate of 5 ° C./min. Ion-exchanged water was added to the slurry cooled to room temperature so that the solid content would be 5% by mass. A binder resin dispersion in which fine particles of a polyester resin having a volume median diameter of 140 nm are dispersed was obtained. In addition, the volume median diameter of the polyester resin was measured using a particle size distribution measuring device (“Microtrack UPA150” manufactured by Nikkiso Co., Ltd.).

(Preparation of release agent dispersion)
Release agent (“Nissan Electol (registered trademark) WEP-5” manufactured by NOF Corporation, 200 g of components: pentaerythritol behenate wax, melting temperature 84 ° C.), anionic surfactant (“Emar E manufactured by Kao Corporation) -27C ") 2g and ion-exchanged water 800g. The obtained mixture was heated to 100 ° C. to melt the release agent, and then emulsified with a homogenizer (“Ultra Tlux T50” manufactured by IKA) for 5 minutes. Subsequently, the emulsification process was performed on the conditions of 100 degreeC using the gorin type homogenizer (made by Manton Gorin). In this way, a release agent dispersion having a solid content concentration of 20% by mass was obtained. The volume median diameter of the release agent was 250 nm, and the melting point of the release agent was 83 ° C. The volume median diameter of the release agent was measured using a particle size distribution measuring apparatus (“Microtrac UPA150” manufactured by Nikkiso Co., Ltd.).

(Preparation of colorant dispersion)
Cyan colorant (CI Pigment Blue 15: 3, component: copper phthalocyanine) 90 g, anionic surfactant (“Emar 0” manufactured by Kao Corporation, component: sodium lauryl sulfate) 10 g, and 400 g of ion-exchanged water are mixed. did. The mixed solution was emulsified and dispersed for 1 hour using a high-pressure impact disperser ultimateizer (“HJP30006” manufactured by Sugino Machine Co., Ltd.). A colorant dispersion having a solid concentration of 18% by mass was obtained. The volume median diameter of the colorant particles contained in the obtained colorant dispersion was 160 nm, and the Cv value of the particle size distribution was 25%. From the TEM image of the colorant particles, it was confirmed that the circularity was 0.800. The volume median diameter of the colorant particles was measured using a particle size distribution measuring device (“Microtrack UPA150” manufactured by Nikkiso Co., Ltd.).

(Toner core manufacturing process)
A temperature sensor, a condenser tube, and a stirrer were installed in a 1 L four-necked flask. 425 g of binder resin dispersion, 12.5 g of release agent dispersion, 7 g of colorant dispersion, 12 g of an anionic surfactant (“Emar 0” manufactured by Kao Corporation, component: sodium lauryl sulfate), and ion-exchanged water 43. 5 g was mixed in a four neck flask. The resulting mixture was stirred at a stirring speed of 200 rpm. Thereafter, the pH of the flask contents was adjusted to 9 using triethanolamine. Next, an aqueous solution in which 10.2 g of magnesium chloride hexahydrate (flocculating agent) was dissolved in 10.2 g of ion-exchanged water was added to the flask. After allowing the dispersion in the flask to stand for 5 minutes, the internal temperature of the flask was increased to 50 ° C. at a rate of 5 ° C./min. Thereafter, the internal temperature of the flask was further increased to 73 ° C. at a rate of 0.5 ° C./min. Next, the temperature of the dispersion was kept at 73 ° C. to aggregate the fine particles in the dispersion. When the volume average particle diameter of the aggregated particles in the dispersion reached 6.5 μm, 29.3 g of sodium chloride (aggregation terminator) was added, and the dispersion was stirred at a stirring speed of 350 rpm for 10 minutes. After stirring, the dispersion is cooled to room temperature at a rate of 5 ° C./min to obtain a dispersion containing a toner core having a volume median diameter of 6.6 μm, a number median diameter of 5.7 μm, and a number average circularity of 0.93. It was. A wet cake-like toner core was filtered from the toner core dispersion using a filter cloth having an opening of 1 μm with respect to the obtained dispersion. The toner core was washed again by dispersing the wet cake toner core in ion exchange water. Washing of the toner core with ion-exchanged water was repeated 5 times. The washed wet cake toner core was vacuum dried at 40 ° C. to obtain a toner core.

(Shell layer forming process)
300 mL of ion-exchanged water was placed in a 1 L three-necked flask equipped with a thermometer and a stirring blade, and the flask internal temperature was maintained at 30 ° C. using a water bath. Next, dilute hydrochloric acid was added to the flask to adjust the pH of the aqueous medium in the flask to 4. After adjusting the pH, a thermosetting resin precursor and a thermoplastic resin were added to the flask as raw materials for the shell layer. As a thermosetting resin precursor, 1.0 g of an aqueous solution of a hexamethylolmelamine initial polymer (“Milben (registered trademark) Resin SM-607” manufactured by Showa Denko KK, solid content concentration: 80% by mass) was added. As a thermoplastic resin, 1.5 g of an aqueous solution of acrylamide resin (“BECKAMINE (registered trademark) A-1” manufactured by DIC Corporation, solid content concentration: 11% by mass) was added. The raw material for the shell layer was dissolved in an aqueous medium to obtain an aqueous solution (A) of the raw material for the shell layer. To the aqueous solution (A), 300 g of the toner core was added, and the contents of the flask were stirred at a stirring speed of 200 rpm for 1 hour. Next, 300 mL of ion exchange water was added to the flask. Thereafter, the temperature in the flask was increased to 70 ° C. at a rate of 1 ° C./min while stirring the contents of the flask at a stirring rate of 100 rpm. After the temperature increase, the contents of the flask were stirred for 1 hour under the conditions of a temperature of 70 ° C. and a stirring speed of 100 rpm. Thereafter, 1.6 mL of benzylamine (manufactured by Tokyo Chemical Industry Co., Ltd., special grade reagent) was added as a surface treatment agent, and the flask contents were further stirred for 1 hour. Thereafter, sodium hydroxide was added to the flask to adjust the pH of the contents of the flask to 7. Next, the contents of the flask were cooled to room temperature to obtain a dispersion containing toner mother particles.

(Washing process)
Using a Buchner funnel, wet cake-like toner base particles were filtered from the dispersion containing the toner base particles. Subsequently, the toner base particles in the form of wet cake were dispersed again in ion-exchanged water to wash the toner base particles. Such washing of the toner base particles with ion-exchanged water was repeated 5 times.

(Drying process)
The wet cake-like toner base particles obtained in the washing step were 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 reforming apparatus (“Coatmizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.) to dry the toner base particles in the slurry to obtain toner base particles. Drying conditions were a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min.

(External addition process)
100 parts by mass of toner base particles obtained in the drying step and 1.0 part by mass of dry silica (“REA90” manufactured by Nippon Aerosil Co., Ltd.) were used using a 10 L capacity FM mixer (manufactured by Nippon Coke Industries, Ltd.). The mixture was mixed for 5 minutes to adhere the external additive to the surface of the toner base particles. Thereafter, the obtained toner was sieved with a 200 mesh (aperture 75 μm) sieve to obtain the toner of Example 1.

Example 2
In the shell layer forming step, instead of 1.0 g of an aqueous solution of hexamethylolmelamine initial polymer as a thermosetting resin precursor, methylolated urea ("Milben (registered trademark) resin 3HSP-H (trade name) manufactured by Showa Denko KK" The toner of Example 2 was obtained in the same manner as the toner of Example 1 except that 1.0 g was added.

Example 3
In the shell layer forming step, instead of 1.5 g of an aqueous solution of acrylamide resin as a thermoplastic resin, the copolymer was changed to adding 1.5 g of copolymerized acrylic (“Vinyl Blanc 2647 (trade name)” manufactured by Nissin Chemical Industry Co., Ltd.). Except for the above, the toner of Example 3 was obtained in the same manner as the toner of Example 1.

Example 4
In the shell layer forming step, the toner of Example 1 was used except that 1.6 mL of dodecylamine (manufactured by Tokyo Chemical Industry Co., Ltd., first grade reagent) was added instead of 1.6 mL of benzylamine as a surface treatment agent. A toner of Example 4 was obtained in the same manner.

Example 5
In the shell layer forming step, the addition amount of the aqueous solution of the hexamethylolmelamine initial polymer as the thermosetting resin precursor is changed from 1.0 g to 1.5 g, and the addition amount of benzylamine as the surface treatment agent is 1. A toner of Example 5 was obtained in the same manner as the toner of Example 1 except that the volume was changed from 6 mL to 2.4 mL.

Example 6
In the shell layer forming step, the addition amount of the aqueous solution of hexamethylolmelamine initial polymer as the thermosetting resin precursor is changed from 1.0 g to 0.8 g, and the addition amount of benzylamine as the surface treatment agent is 1. A toner of Example 6 was obtained in the same manner as the toner of Example 1 except that the volume was changed from 6 mL to 1.2 mL.

Example 7
In the shell layer forming step, the toner of Example 7 was obtained in the same manner as the toner of Example 1, except that the addition amount of the aqueous solution of the acrylamide resin as the thermoplastic resin was changed from 1.5 g to 2.0 g. .

Example 8
In the shell layer forming step, the toner of Example 8 was obtained in the same manner as the toner of Example 1, except that the addition amount of the aqueous solution of the acrylamide resin as the thermoplastic resin was changed from 1.5 g to 1.0 g. .

Example 9
The toner of Example 9 was obtained in the same manner as the toner of Example 1, except that the amount of benzylamine added as the surface treatment agent was changed from 1.6 mL to 2.4 mL in the shell layer forming step.

Example 10
A toner of Example 10 was obtained in the same manner as the toner of Example 1, except that the amount of benzylamine added as the surface treatment agent was changed from 1.6 mL to 1.2 mL in the shell layer forming step.

Comparative Example 1
In the shell layer forming step, Comparative Example 1 was obtained in the same manner as in Example 1 except that the surface treatment agent was not added.

Comparative Example 2
In the shell layer forming step, in the same manner as in Example 1 except that 1.6 mL of ethylamine (manufactured by Tokyo Chemical Industry Co., Ltd., reagent) was added as a surface treatment agent instead of 1.6 mL of benzylamine. Comparative Example 2 was obtained.

Comparative Example 3
In the shell layer forming step, the same method as in Comparative Example 2 was applied except that 1.6 mL of furfurylamine (manufactured by Tokyo Chemical Industry Co., Ltd., reagent) was added as a surface treatment agent instead of 1.6 mL of ethylamine. Comparative Example 3 was obtained.

Comparative Example 4
In the shell layer forming step, the same method as in Comparative Example 2 except that 1.6 mL of ethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd., special grade reagent) is added as a surface treatment agent instead of 1.6 mL of ethylamine. Comparative Example 4 was obtained.

  Table 1 summarizes the thermosetting resins, thermoplastic resins, and surface treatment agents used in forming the shell layers of Examples 1-10 and Comparative Examples 1-4.

[Evaluation method]
The evaluation method of each sample (the toners of Examples 1 to 10 and Comparative Examples 1 to 4) is as follows.

<Heat resistant storage stability>
A sample for evaluation of heat-resistant storage stability was obtained by weighing 2 g of a sample (toner) into a 20 mL capacity plastic container and leaving it in a thermostat set at 60 ° C. for 3 hours. Then, the sample for heat-resistant storage stability evaluation was sieved using a 100 mesh (aperture 150 μm) sieve under the conditions of rheostat scale 5 and time 30 seconds according to the manual of a powder tester (manufactured by Hosokawa Micron Corporation). . After sieving, the mass of the sample remaining on the sieve was measured. From the mass of the sample before sieving and the mass of the sample remaining on the sieving after sieving, the degree of aggregation (% by mass) of the sample was calculated according to the following formula. From the calculated degree of aggregation of the sample, the heat resistant storage stability of the sample was evaluated according to the following criteria.
Aggregation degree (mass%) = (mass of sample remaining on sieve / mass of sample before sieving) × 100
A (very good): The degree of aggregation of the sample is less than 40% by mass.
○ (Good): The degree of aggregation of the sample is 40% by mass or more and less than 50% by mass.
X (not good): The degree of aggregation of the sample is 50% by mass or more.

<Charge decay constant>
The charge decay constant α of the toner (the charge decay constant of the toner base particles) conforms to the JIS standard (JIS C 61340-2-1) using an electrostatic diffusivity measuring device (“NS-D100” manufactured by Nano Seeds Co., Ltd.). It was measured by the method. The method for measuring the charge decay constant of the toner will be described in detail below.

  A sample (toner) was placed in the measurement cell. The measurement cell was a metal cell in which a recess having an inner diameter of 10 mm and a depth of 1 mm was formed. The sample was pushed in from above using a slide glass, and the concave portion of the cell was filled with the sample. The sample overflowed from the cell was removed by reciprocating the slide glass on the surface of the cell. The filling amount of the sample was 0.04 g or more and 0.06 g or less.

Subsequently, the measurement cell filled with the sample was left in an environment of a temperature of 32 ° C. and a humidity of 80% RH for 12 hours. Subsequently, the grounded measurement cell was placed in an electrostatic diffusivity measuring device, and ions were supplied to the sample by corona discharge, and the sample was charged under the condition of a charging time of 0.5 seconds. And after 0.7 second passed after completion | finish of corona discharge, the surface potential of the sample was measured continuously. Based on the measured surface potential and the formula “V = V ₀ exp (−α√t)”, the charge decay constant (charge decay rate) α of the sample was calculated. In the formula, V represents the surface potential [V], V ₀ represents the initial surface potential [V], and t represents the decay time [second]. The calculated charge decay constant α of the sample was evaluated according to the following criteria.
A (very good): The charge decay constant α of the sample is less than 0.015.
○ (Good): The charge decay constant α of the sample is 0.015 or more and less than 0.017.
X (bad): The charge decay constant α of the sample is 0.017 or more.

  The low-temperature fixability of each sample (toner) was evaluated using a two-component developer adjusted according to the following method.

  A developer carrier (a carrier for “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) and a toner of 10% by mass with respect to the mass of the developer carrier are mixed for 30 minutes using a ball mill, and two components for evaluation are mixed. A developer was prepared.

<Low temperature fixability>
An image was formed using the two-component developer prepared as described above, and the low-temperature fixability of the toner was evaluated. As an evaluator, a color printer having a Roller-Roller type heat and pressure type fixing device (nip width 8 mm) (evaluator capable of changing the fixing temperature by modifying "FS-C5250DN" manufactured by Kyocera Document Solutions Co., Ltd.) ) Was used. The two-component developer prepared as described above was put into a developing device of an evaluation machine, and a sample (toner) was put into a toner container of the evaluation machine.

When evaluating the fixability of the sample (toner), the above-mentioned evaluation machine was used, and the linear velocity was 200 mm / second (nip passage time 40 msec), and the toner applied amount was 1.0 mg / cm ^2. A solid image having a size of 25 mm × 25 mm and a printing rate of 100% was formed on paper No. ² (A4 size printing paper). Subsequently, the paper on which the image was formed was passed through a fixing device. The setting range of the fixing temperature was 100 ° C. or higher and 200 ° C. or lower. Specifically, the fixing temperature of the fixing device was gradually increased from 100 ° C., and the minimum temperature (minimum fixing temperature) at which the toner (solid image) can be fixed on the paper was measured.

Whether or not the toner could be fixed in the measurement of the minimum fixing temperature was confirmed by a rubbing test as shown below. Specifically, the paper was folded in half so that the surface on which the image was formed was inside, and a 1 kg weight covered with a cloth was used to rub the crease 5 times. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the length (peeling length) of toner peeling at the bent portion was measured. The lowest temperature among the fixing temperatures at which the peeling length was less than 1 mm was defined as the lowest fixing temperature. From the obtained minimum fixing temperature, the low-temperature fixability of the sample was evaluated according to the following criteria.
○ (Good): The minimum fixing temperature of the sample is 130 ° C. or lower.
X (Poor): The minimum fixing temperature of the sample is higher than 130 ° C.

[Evaluation results]
The evaluation results for each of the samples (the toners of Examples 1 to 10 and Comparative Examples 1 to 4) are as follows.

  Table 2 shows the evaluation results of the heat-resistant storage stability, low-temperature fixability, and charge decay constant of the toners of Examples 1 to 10 and Comparative Examples 1 to 4, respectively.

  The toners according to Examples 1 to 10 were electrostatic latent image developing toners having the above-described configurations (1) and (2), respectively. Specifically, the toners according to Examples 1 to 10 each contained toner particles including a toner core and a shell layer covering the surface of the toner core. The shell layer contained a thermosetting resin and a thermoplastic resin. The thermosetting resin was one or more resins selected from the group consisting of melamine resins, urea resins, and glyoxal resins. The thermosetting resin had a hydrophobic functional group at the terminal.

  Each of the toners according to Examples 1 to 10 was excellent in heat-resistant storage stability, low-temperature fixability, and charge decay constant.

  The toner for developing an electrostatic latent image according to the present invention can be used for forming an image in, for example, a copying machine or a printer.

Claims (4)

An electrostatic latent image developing toner containing toner particles including a toner core and a shell layer covering a surface of the toner core,
The shell layer includes a thermosetting resin having a hydrophobic functional group at a terminal and a thermoplastic resin,
An electrostatic latent image developing toner, wherein the thermosetting resin is at least one resin selected from the group consisting of melamine resin, urea resin, and glyoxal resin.   The electrostatic latent image developing toner according to claim 1, wherein the hydrophobic functional group is a benzyl group or an alkyl group having 8 or more carbon atoms. A toner core manufacturing process for manufacturing the toner core;
A shell layer containing a thermosetting resin and a thermoplastic resin is formed on the surface of the toner core by heating a mixture of the toner core, the thermosetting resin precursor, and the thermoplastic resin obtained in the toner core manufacturing process. Forming, and
A method for producing a toner for developing an electrostatic latent image, comprising a step of modifying a terminal of the thermosetting resin contained in the shell layer with the hydrophobic functional group using a surface treatment agent having a hydrophobic functional group. Because
A method for producing a toner for developing an electrostatic latent image, wherein the thermosetting resin is at least one resin selected from the group consisting of a melamine resin, a urea resin, and a glyoxal resin.   The method for producing a toner for developing an electrostatic latent image according to claim 3, wherein the surface treatment agent is benzylamine or an alkylamine having 8 or more carbon atoms.